A REPORT ON SUMMER INTERNSHIP IN ONGC

RAJAMUNDRY

FACILITIES IN PRODUCTION &SAFETY MEASURES

Submitted by

NAGANABOYINA LIKHITA CHANDINI

University College Of Engineering Kakinada

From 22/05/2025 to 22/06/2025

Under the Guidance of

Shri K.Sri Krishna Shri

N.Srinivasulu
DGM (product). CE(P)
 1.INTRODUCTION

The petroleum industry is one of the most technically complex and strategically vital sectors
in the global economy. Organizations such as the Oil and Natural Gas Corporation (ONGC)
play a critical role in the exploration, production, and processing of hydrocarbons, which
serve as the backbone of modern energy systems. The operations in such industries require
sophisticated production facilities and highly regulated safety measures to ensure efficiency,
continuity, and protection of human and environmental resources.

●​ Facilities in Production
In the context of petroleum production, facilities typically include onshore and offshore
drilling rigs, production platforms, processing plants, storage tanks, pipelines, and terminal
stations. These installations are designed to handle the exploration, extraction, separation,
treatment, and transportation of crude oil and natural gas. Advanced control systems,
instrumentation, and process automation are employed to monitor and regulate flow rates,
pressures, and chemical compositions, ensuring consistent production output and product
quality.

ONGC’s production facilities are often located in remote or offshore areas, demanding robust
infrastructure that can withstand harsh environments while maintaining operational integrity.
Key components like wellheads, separators, compressors, flare systems, and emergency
shutdown systems are integrated into the production process to manage complex upstream
activities.

●​ Safety Measures

Given the hazardous nature of petroleum operations—including high-pressure systems,

flammable substances, toxic gases (e.g., H₂S), and extreme temperatures—safety is of
paramount importance. ONGC and similar organizations follow strict safety protocols
aligned with international standards such as ISO 45001 (Occupational Health & Safety), API
(American Petroleum Institute) guidelines, and local government regulations.
 2. Oil And Natural Gas Corporation
Limited
2.1.The Overview of ONGC:

ONGC is vertically integrated across the entire oil and gas industry. It is involved in
exploring for and exploiting hydrocarbons in 26 sedimentary basins of India, owns and
operates over 11,000 kilometers of pipelines in the country and operates a total of around 230
drilling and workover rigs. Its international subsidiary ONGC Videsh currently has projects
in 15 countries. ONGC has discovered 7 out of the 8 producing Indian Basins, adding over
7.15 billion tonnes of In-place Oil & Gas volume of hydrocarbons in Indian basins. Against a
global decline of production from matured fields, ONGC has maintained production from its
brownfields like Mumbai High, with the help of aggressive investments in various IOR
(Improved Oil Recovery) and EOR (Enhanced Oil Recovery) schemes. ONGC has many
matured fields with a current recovery factor of 25–33%.[5] Its Reserve Replacement Ratio for
between 2005 and 2013, has been more than one.[5]
During FY 2012–13, ONGC had to share the highest ever under-recovery of ₹ 89765.78
billion (an increase of ₹ 17889.89 million over the previous financial year) towards the
under-recoveries of Oil Marketing Companies (IOC, BPCL and HPCL).[5]
On 1 November 2017, the Union Cabinet approved ONGC for acquiring a majority 51.11%
stake in Hindustan Petroleum Corporation Limited (HPCL).[6] On 30 January 2018, ONGC
completed the acquisition of 51.11% stake in HPCL.[

2.2 The History of ONGC

●​ 1956: ONGC established by the Indian government to explore and develop oil and
natural gas resources.
 ●​ 1959: ONGC was converted into a statutory body.
●​ 1959: First oil discovery in the Cambay basin.
●​ 1965-67: Giant oil discovery in Ankleshwar, Gujarat, followed by discoveries in
Assam.
●​ 1970: Discovery of Bombay High, a major offshore oil field.
●​ 1980: ONGC expanded into offshore exploration and production.
●​ 1994: ONGC was reorganized as a public limited company.
●​ 2001: ONGC's international arm, OVL, began undertaking petroleum projects
overseas.
●​ 2003: ONGC acquired a 25% stake in the Greater Nile Oil Project.
●​ 2010: ONGC was recognized as the most valuable Indian company.
●​ 2018: ONGC acquired the government's stake in Hindustan Petroleum Corporation
Limited (HPCL).

Basins:
Producing Basins :
1. Cambay Basin – Vadodara, Gujarat
2. Mumbai Offshore Basin – Mumbai, Maharashtra
3. Krishna-Godavari (KG) Basin – Rajahmundry, Andhra Pradesh
4. Cauvery Basin – Karaikal/Chennai, Tamil Nadu
5. Assam Shelf Basin – Nazira, Assam
6. Assam-Arakan Fold Belt – Jorhat, Assam
7. Rajasthan Basin – Jodhpur, Rajasthan
Non- Producing Basins :
1. Tripura-Cachar Basin – Agartala, Tripura
2. Mahanadi Basin – Bhubaneswar, Odisha
3. Vindhyan Basin – Varanasi, Uttar Pradesh
4. Saurashtra Basin – Rajkot, Gujarat
5. Kutch Basin – Bhuj, Gujarat
6. Himalayan Foreland Basin – Dehradun, Uttarakhand
7. Bengal Basin – Kolkata, West Bengal
8. Andaman-Nicobar Basin – Port Blair, A&N Islands

2.3Krishna Godavari Basin

The Krishna-Godavari (KG) Basin, situated along India's eastern coast, is a significant
hydrocarbon-rich region contributing substantially to the nation's oil and gas production. As
of the latest available data, the basin comprises 54 fields with a total of 324 wells across its
onland, shallow water, and deepwater sub-basins. The onland sub-basin hosts 40 fields with
251 wells, the shallow water sub-basin contains 11 fields with 48 wells, and the deepwater
sub-basin has 3 fields with 25 wells.
In terms of production, the KG Basin has been a significant contributor to India's energy
sector. Notably, the Ravva oil field, developed in partnership with Cairn India, ONGC,
Videocon, and Ravva Oil Singapore Private Limited, has produced over 253 million barrels
of crude oil and sold 317 billion cubic feet of gas, surpassing initial estimates. Additionally,
the deepwater KG-DWN-98/2 block, located approximately 30 kilometers off the coast of
Kakinada, commenced oil production in January 2024. This project is expected to peak at
45,000 barrels of oil per day and over 10 million metric standard cubic meters per day of gas,
potentially increasing ONGC's total oil production by 11% and gas production by 15%.

Collectively, the KG Basin's extensive network of wells and robust production capacities
underscore its pivotal role in India's hydrocarbon sector, significantly bolstering domestic oil

and gas output.

2.4 The History of KG Basin

●​ 1956: ONGC was founded on 14 August to lead India's quest for energy
self-sufficiency.

●​ 1959: Achieved its first major success with the discovery of oil in the Cambay Basin,
Gujarat.

●​ 1974: Discovered the iconic Bombay High offshore field, transforming India’s oil
production landscape.
●​ 1983–85: Initiated exploratory activities in the Krishna-Godavari (KG) Basin, located
along the eastern coast of India.

●​ Late 1990s: Stepped up investments in seismic surveys and deepwater drilling in the
KG Basin, which showed immense hydrocarbon potential.

●​ 2001: Major gas discoveries in the KG-DWN-98/2 block (KG-D5), one of ONGC’s
biggest offshore assets.

●​ 2004–2015: Intensive development planning for the KG-D5 block, involving

cutting-edge technology and deep-sea infrastructure.

●​ 2018: ONGC launched an ambitious project to develop Cluster-II of the KG-D5

block with an estimated investment of over $5 billion.

●​ 2021 onwards: Production operations began in phases from the KG Basin’s deepwater
reserves, contributing significantly to India’s domestic gas output.

●​ 2025: ONGC expanded offshore activities in the KG Basin and announced

breakthroughs in enhanced recovery from deep formations, boosting energy security.
 3.PETROLEUM GEOLOGY
Petroleum is a naturally occurring, flammable liquid found beneath the Earth's surface. It's a
complex mixture of hydrocarbons—basically long chains of hydrogen and carbon—and it
serves as the raw material for fuels like petrol, diesel, jet fuel, and also for products like
plastics and synthetic rubber.It all starts millions of years ago. Dead plants, algae, and tiny
sea creatures settled at the bottoms of oceans and swamps. Over time, they got buried under
layers of mud, sand, and rock. Without oxygen and under immense heat and pressure, these
organic remains slowly broke down and transformed into petroleum.The whole process takes
millions of years, which is why we call it a non-renewable resource. It's a bit like nature’s
very slow cooking recipe—low and slow, buried deep, and without any do-overs.

3.1 EXTERNAL DYNAMICS:

External dynamics refer to the surface and near-surface geological

processes that influence sedimentation, basin formation, and
hydrocarbon potential over time. These are mainly exogenic
processes—driven by forces outside the Earth’s interior, such as
climate, water, wind, and biological activity.
1. Weathering and Erosion
●​ Breakdown of rocks on Earth’s surface due to atmospheric factors (wind, rain, temperature).
●​ Supplies sediments to basins, which can become source or reservoir rocks.

2. Transportation and Deposition

●​ Agents like rivers, glaciers, wind, and ocean currents transport sediments.
●​ Deposition in various environments (fluvial, deltaic, marine) forms sedimentary layers, which
are essential for petroleum systems.
3. Sedimentation and Stratigraphy
●​ Determines the type and layering of sedimentary rocks—key for reservoir, source, and seal
rocks.
●​ Controls porosity, permeability, and organic content—crucial for hydrocarbon generation and
accumulation.

4. Sea Level Changes (Eustasy)

●​ Global sea level rise/fall affects sedimentation rates and environments.

●​ Transgression (rising sea level) and regression (falling sea level) influence facies distribution,
affecting reservoir quality.

5. Climate and Biologic Activity

●​ Tropical climates → more vegetation → organic-rich source rocks.

●​ Biologic productivity influences organic matter accumulation and preservation.

3.1.1 Origin of Petroleum

The origin of petroleum is like a time capsule from Earth's distant past—roughly 300 to 400
million years ago.It all began when the Earth looked very different. Vast oceans teemed with
microscopic organisms like plankton, algae, and other simple marine life. When these
organisms died, they sank to the sea floor, mixing with mud and sand. Over time, layer upon
layer of this organic-rich sediment built up . With burial over millions of years, the combined
effects of intense heat, pressure, and lack of oxygen caused chemical reactions that gradually
turned this once-living material into hydrocarbons—what we now call crude oil and natural
gas. So, in a poetic sense, petroleum is sunlight from ancient times, stored in the bodies of
prehistoric life and converted by Earth's deep processes into energy we still use today.

3.2 SUBSURFACE STRUCTURES

Subsurface structures are the geometrical arrangements of rock layers beneath the Earth's
surface, caused by tectonic forces, sedimentation, and diagenetic processes. These structures
are critical in petroleum exploration because they control.
●​ The generation, migration, and accumulation of hydrocarbons.
●​ The formation of structural traps that hold oil and gas.

3.2.1 Folds:
🌀 Anticline
●​ Arch-shaped fold with oldest rocks at the core.
●​ Hydrocarbons migrate up and accumulate at the crest if sealed properly.

🕳️
●​ Most classic oil fields are found in anticlines.
Syncline
 ●​ Trough-shaped fold with youngest rocks at the core.
●​ Not ideal for hydrocarbon accumulation but may assist migration paths.

3.2.2 Faults:
A fault is a fracture in the Earth’s crust where rocks on either side have moved relative to
each other due to tectonic forces. In petroleum geology, faults are important because they can
act as traps for oil and gas, pathways for migration, or even leak points depending on their
nature. Common types include normal, reverse, thrust, and strike-slip faults, each formed
by different stress conditions. Faults often help form structural traps by placing permeable
reservoir rocks against impermeable seal rocks, making them key targets in oil and gas
exploration.

3.2.3 Fractures and Joints:

In petroleum geology, fractures and joints are natural breaks or cracks in rocks. These are
formed due to stress in the Earth’s crust. Unlike faults, they usually don’t show significant
movement along the crack surface.
Joints: Cracks with no visible displacement.
Fractures: A broader term; includes joints and small displacements.

3.2.4 Salt Domes

Salt domes are dome-shaped geological structures formed when a thick bed of evaporite
minerals, primarily halite (rock salt), rises through overlying sedimentary layers due to its
low density and plasticity. Over millions of years, buried salt layers become mobile under
pressure and begin to flow upward, piercing through rock strata to create a dome-like shape.
These structures are very important in petroleum geology because they can form excellent
traps for oil and gas. As the salt rises, it deforms and bends the surrounding rocks, creating
spaces where hydrocarbons can accumulate. The impermeable nature of salt also acts as a
seal, preventing oil and gas from escaping. Salt domes are often associated with productive
oil fields, especially in regions like the Gulf of Mexico, Iran, and West Africa. Modern
exploration uses seismic surveys to locate these domes and understand their trap potential.
3.2.5 Unconformities:
An unconformity is a surface in the rock record that represents a gap in geological time,
caused by erosion or non-deposition. It separates older rock layers from younger ones and
indicates that part of the geologic record is missing. In petroleum geology, unconformities are
important because they can form stratigraphic traps for hydrocarbons. When a porous
reservoir rock is truncated by an unconformity and later overlain by impermeable rocks, oil
and gas can accumulate beneath the sealing layer. Unconformities also influence migration
pathways, acting either as barriers or conduits depending on their properties. There are
different types of unconformities, including angular unconformities, disconformities, and
nonconformities, each reflecting different geological histories. Identifying unconformities
using seismic data and well logs is a key step in successful oil and gas exploration.

3.3 TRAPS:
A trap is a geological structure that blocks the upward migration of oil and gas and causes them to
accumulate in a reservoir rock. Traps are essential components of a petroleum system, as they hold
hydrocarbons in place until they are discovered and extracted. Without traps, the hydrocarbons would
continue migrating until they escape to the surface.

3.3.1 Structural Traps

Structural traps are formed due to the deformation of rock layers caused by tectonic forces
such as compression, tension, or shearing. These deformations lead to the creation of
structures like folds and faults, which can trap migrating hydrocarbons beneath an
impermeable sealing rock. Common types of structural traps include anticline traps, where
rock layers are bent upward in an arch-like shape, and fault traps, where a fault displaces
reservoir rock against a sealing formation. Structural traps are among the most important and
widely discovered types in petroleum exploration because they are often large, well-defined,
and detectable using seismic surveys. Their ability to trap oil and gas depends on the presence
of a reservoir rock, a seal rock, and the timing of hydrocarbon migration relative to the trap
formation.
3.3.2 Statigraphic Traps

Stratigraphic traps are formed due to variations in sedimentary rock layers caused by changes
in deposition, erosion, or lithology rather than tectonic movements. These traps occur
when a porous reservoir rock is enclosed by impermeable rocks due to changes in rock type,
thinning out (pinch-out), or truncation by an unconformity. Unlike structural traps, which rely
on folding or faulting, stratigraphic traps depend on the original rock layering and
depositional features. Examples include pinch-out traps, reef traps, and unconformity traps.
Though harder to detect through seismic data, they are important because they can host
significant hydrocarbon accumulations, especially in subtle or hidden reservoirs.
Detailed geological and stratigraphic analysis is essential to identify these traps accurately
during exploration.

3.4 COOKING OF CRUDE OIL :

Chemical processes will take place in order to transform organic

matter preserved in source rocks into petroleum. This can be called a
cooking process. Three phases regarding maturation of the organic
matter to form petroleum are diagenesis, catagenesis and metagenesis.

Diagenisis: This occurs at shallow surfaces and begins during initial deposition. It normally
takes place from a shallow depth to 1,000 m and the temperature range is less than 60 C (140
F). Non-biogenic reaction and biogenic decay aided by bacteria turns organic matter to
Methane (CH4), Carbon Dioxide (CO2), water (H2O) and Kerogen. Kerogen is a precursor
tothe creation of petroleum. Types of kerogens depend on the original type of organic matter.

Catagenesis: With an increasing depth of deposition, pressure and temperature increase and
bacteria cannot live in this environment. The critical temperature is around 60 C (140 F) that
will start to crack molecules of kerogen and then oil begins to form. The deeper the depth of
burial, the higher the temperature that will crack molecules of oil and heavy oil will become
lighter oil or gas.
Metagenesis: This phase occurs at very high temperature and pressure. Gas molecules will
be broken down and become only carbon in the form of graphite.

3.5 RESERVOIR SYSTEM:

A reservoir system is a natural underground formation that stores and allows the movement
of fluids like oil, gas, or water. It typically consists of a reservoir rock, which has enough
porosity to hold fluids and enough permeability to let them flow, a seal rock that traps the
fluids and prevents them from escaping, and a trap structure that gathers hydrocarbons in one
place. The system also includes source rocks where hydrocarbons are formed and migration
pathways that guide them into the reservoir. Altogether, this setup makes it possible to
accumulate and eventually extract hydrocarbons efficiently.

Key Characteristics:
1.POROSITY:
Porosity refers to the amount of empty space—or pores—within a rock that can hold fluids
like oil, gas, or water. It’s usually expressed as a percentage of the total rock volume.
There are two main types:
●​ Primary porosity: These are the original spaces between grains in sedimentary rocks
like sandstone.
●​ Secondary porosity: These develop later through processes like fracturing,
dissolution, or weathering—common in carbonate rocks.
Higher porosity means a rock can store more fluid, but to actually extract that fluid,
permeability (how well fluids flow through the rock) matters too. It’s kind of like having a
sponge—you want not just the holes, but interconnected holes that let the fluid move.
2.PERMEABILITY:
Permeability is the ability of a rock or sediment to allow fluids (like oil, gas, or water) to flow through
its pore spaces. While porosity tells you how much fluid a rock can hold, permeability tells you how
easily that fluid can move.
There are three main types:
●​ Absolute permeability: measures flow of a single fluid when the rock is fully saturated.
●​ Effective permeability: measures flow of one fluid when other fluids are present.
●​ Relative permeability: compares how well multiple fluids flow through the rock together.
Permeability is typically measured in units called darcies or millidarcies (mD). Higher values mean
higher ease of fluid flow.

3.LITHOLOGY
Most reservoir rocks are sedimentary, such as:
●​ Sandstones: common due to good porosity and permeability.
●​ Carbonates (limestone, dolostone): can have high secondary porosity.
●​ Fractured rocks: even low-porosity rocks like shale can act as reservoirs if heavily
fractured.

4.TEXTURE & GRAIN SIZE:

Texture in reservoir rocks refers to the size, shape, sorting, and arrangement of the mineral
grains within the rock. It plays a key role in determining the porosity and permeability, which
are crucial for storing and transmitting oil and gas. Well-sorted and loosely packed grains,
especially if rounded, usually create better pore spaces and fluid flow pathways, making the
rock a good reservoir. In contrast, poorly sorted or tightly packed textures reduce the
effectiveness of a reservoir.

5.CEMENTATION& COMPACTION
Cementation is a geological process where minerals, carried by groundwater, fill the spaces
between sediment grains and bind them together into solid rock. It’s one of the key steps in
turning loose sediment into sedimentary rock, like sandstone or limestone.

●​ When more minerals like quartz or calcite are deposited, they can clog up the pores,
reducing the rock’s ability to store and transmit fluids.
●​ Light cementation might still preserve good reservoir quality, but heavy cementation
usually reduces porosity and permeability significantly.
6.WETTABILITY
Wettability is the tendency of a fluid to spread on or adhere to a solid surface in the presence
of other immiscible fluids—like oil and water in a rock. In reservoir engineering, it’s a crucial
property because it influences how fluids are distributed in the pore spaces of the rock and
how easily they can be produced.

Types of Wettability:
1. Water-wet: Water coats the rock surface, and oil occupies the center of the pores. This is
the most common and generally preferred condition for oil recovery.
2. Oil-wet: Oil sticks to the rock surface, and water fills the center of the pores.
3. Intermediate-wet or mixed-wet: A combination of both, where some parts of the rock are
water-wet and others are oil-wet.

7.BUOYONCY
Buoyancy in a reservoir refers to the upward force that causes lighter fluids like oil and gas to
rise above heavier fluids like water within the pore spaces of a rock. This phenomenon is
driven by differences in fluid density and plays a key role in how hydrocarbons migrate and
accumulate in traps.

3.6 SURFACE GEOPHYSICS

Gravity Surveying
Gravity surveying is a geophysical method used to measure variations in the Earth's
gravitational field to detect subsurface structures. These variations occur due to differences in
the density of underground rocks and formations. In petroleum exploration, gravity surveys
help identify features like salt domes, anticlines, and sedimentary basins, which may act as
traps for oil and gas. It is a non-invasive, cost-effective technique often used in the early
stages of exploration to guide further seismic or drilling activities.
Magnetic Surveying
Magnetic surveying is a geophysical technique used to measure variations in the Earth's
magnetic field caused by the magnetic properties of underground rocks. It helps in identifying
subsurface structures and rock types, especially those containing magnetic minerals like
magnetite. In petroleum exploration, magnetic surveys are useful for mapping basement
rocks, faults, and sedimentary basin boundaries. This method is often used in the initial stages
of exploration as it is quick, cost-effective, and provides valuable information to guide more
detailed surveys like seismic or drilling.

Seismic Surveying
Seismic surveying is a key geophysical method used in petroleum exploration to map subsurface rock
layers and structures. It works by generating seismic waves (using explosives or vibroseis trucks) that
travel through the Earth and reflect back from different geological boundaries. These reflected waves
are recorded by sensors called geophones. By analyzing the travel time and strength of these waves,
geologists can create detailed images of underground formations. Seismic surveys are highly effective
for identifying oil and gas traps, faults, folds, and reservoir structures, making them essential for
accurate drilling decisions.
1.Reflection Sesimology
Reflection seismology is a geophysical method used to study the Earth's subsurface by
analyzing the reflection of seismic waves. In this technique, seismic waves are generated at
the surface (using a controlled source like dynamite or a vibroseis truck), and as they travel
through the Earth, they bounce back or reflect off different rock layers. These reflected waves
are captured by receivers called geophones or hydrophones.

By measuring the time it takes for the waves to return and analyzing their strength,
geophysicists can create detailed images of subsurface structures. Reflection seismology is
especially important in petroleum exploration because it helps identify rock layers, faults, and
traps where oil and gas may accumulate. It provides high-resolution data and is widely used
for both onshore and offshore surveys.

2. Refraction Sesimology

Refraction seismology is a geophysical method used to investigate the subsurface by

analyzing seismic waves that bend, or refract, as they pass through different rock layers.
When a seismic wave travels from one layer to another with a different density and velocity,
it changes direction. If the lower layer has a higher velocity, part of the wave travels along
that layer and returns to the surface, where it is detected by sensors called geophones.
 4.DRILLING
Drilling is the process of creating a borehole (hole in the earth) to access petroleum (oil and
natural gas) reservoirs located deep beneath the Earth's surface. It is a critical phase in oil and
gas exploration and production. The primary objective is to reach the hydrocarbon-bearing
formations and bring the oil or gas to the surface safely and efficiently.

4.1 Types of Drilling:

1. Exploratory Drilling:
●​ Done to locate new oil/gas reservoirs.
●​ Also called wildcat drilling.
●​ Involves geological and geophysical surveys before drilling.

2. Development Drilling:
●​ Performed after discovery of hydrocarbons.
●​ Aims to maximize extraction from a known reservoir.
3. Directional Drilling:
●​ The wellbore is drilled at an angle (not vertical).
●​ Used for accessing multiple reservoirs or offshore platforms.
4. Horizontal Drilling:
●​ The well goes horizontally through the reservoir.
●​ Increases contact with the reservoir, boosting production.
4.2 Drilling Process – Step-by-Step
1. Site Preparation:
●​ Clearing land, constructing roads, installing water supply.
●​ Drilling rig is assembled at the site.
2. Spudding:
●​ The very start of the drilling operation.
●​ Surface hole is drilled first, followed by setting surface casing.
3. Drilling Operation:
●​ Drill bit is attached to a drill string and rotated.
●​ Drilling fluid (mud) is circulated to cool the bit, remove cuttings, and control pressure.
4. Casing and Cementing:
●​ After drilling to a certain depth, steel casing is inserted.
●​ Cement is pumped to hold casing in place and seal off formations.
5. Blowout Preventer (BOP)
●​ A safety device installed at the surface to control pressure and prevent blowouts (uncontrolled
flow).
6. Logging:
●​ Tools are lowered into the well to collect data about rock formations, fluids, porosity, etc.
7. Reaching Target Depth:
●​ Drilling continues until the planned depth is reached, called Total Depth (TD).
8. Well Completion:
●​ Final preparations made to make the well ready for production.
●​ Includes perforation, installation of tubing, packers, and the Christmas tree (valve assembly).

Drilling Rig:

A drilling rig is a large, complex structure used to drill wells into the Earth's surface to extract oil,
natural gas, or water. It contains all the necessary equipment to create a borehole, manage fluids,
control pressure, and reach targeted depths.
4.3 Main Components of a Drilling Rig

1. Derrick or Mast
●​ A tall steel tower that supports the drill string.
●​ Used for lifting and lowering heavy equipment.

2. Drill String
●​ A long assembly of drill pipes connected together.
●​ Transmits rotational force from the surface to the drill bit.

3. Drill Bit
●​ The cutting tool at the end of the drill string.
●​ Breaks and crushes the rock to create the wellbore. Derrick

4. Rotary System
●​ Includes rotary table or top drive.
●​ Rotates the drill string and bit.

5. Mud Circulation System

●​ Pumps drilling mud down the drill string.

●​ Mud cools the bit, removes rock cuttings, and controls
pressure.
●​ Major parts: mud pumps, mud tanks, shale shakers (for
filtering rock cuttings).

6. Blowout Preventer (BOP)

●​ A high-pressure valve system installed at the wellhead.
●​ Prevents blowouts (uncontrolled flow of oil/gas).
●​ Critical for safety.

7. Power System

●​ Includes diesel engines, generators, or electric motors.

●​ Provides power to all parts of the rig.

8. Hoisting System

●​ Uses a drawworks, crown block, and traveling block.

●​ Lifts or lowers drill pipe, casing, and other tools into the
well
4.4 Drilling Fluids:
Drilling fluids, also known as drilling mud, are essential in the drilling process of oil and gas
wells. These specially formulated fluids serve multiple critical functions that ensure the
safety, efficiency, and success of the drilling operation. The primary purpose of drilling fluid
is to cool and lubricate the drill bit as it cuts through various layers of rock. It also helps in
carrying the rock cuttings to the surface, preventing them from clogging the wellbore. One of
the most vital roles of drilling fluids is to maintain hydrostatic pressure within the well, which
helps in controlling subsurface formation pressures and prevents blowouts or influxes of
formation fluids.

Additionally, drilling mud stabilizes the wellbore walls and prevents them from collapsing,
which is crucial for maintaining well integrity. Drilling fluids also aid in suspending cuttings
when the circulation is stopped and help in forming a thin filter cake on the wellbore walls to
minimize fluid loss into permeable formations. There are different types of drilling fluids,
including water-based, oil-based, and synthetic-based muds, and the choice depends on the
geological conditions and the specific requirements of the well. The properties of drilling
mud, such as viscosity, density, pH, and filtration rate, are carefully monitored and adjusted
during drilling operations. Proper management and disposal of used drilling fluids are also
essential to avoid environmental pollution. Overall, drilling fluids play a crucial role in
ensuring a safe, smooth, and cost-effective drilling operation.
4.4.1 Drilling fluid circulating System:
The drilling fluid circulating system is a vital part of the drilling rig that continuously moves drilling
fluid (mud) down the well and back to the surface in a closed-loop system. This system begins at the
mud tanks, where the fluid is stored and treated. Powerful mud pumps then push the fluid through the
standpipe, kelly hose, and drill string all the way down to the drill bit. As the fluid exits the bit, it
cools and lubricates it while carrying the rock cuttings back up the annulus (the space between the
drill pipe and wellbore). Once it returns to the surface, the fluid flows over shale shakers, which
remove the solid cuttings. It then passes through additional solids control equipment like desanders
and desilters for further cleaning before being returned to the mud tanks for reuse. This continuous
circulation maintains pressure control, removes debris, and helps in stabilizing the wellbore, making
the system essential for safe and efficient drilling operations.

4.5 Drill bits

Oil and gas drill bits are broadly classified into two main types on the basis of their primary
cutting mechanism rolling cutter bits & fixed cutter bits. While the former drill largely by
fracturing or crushing the formation with "tooth" shaped cutting elements on two or more
cone-shaped elements that roll across the face of the borehole as the bit is rotated, the latter
employ a set of blades with very hard cutting elements, most commonly natural or synthetic
diamond, to remove material by scraping or grinding action as the bit is rotated

Irrespective of the type, drill bits must satisfy two primary design goals: maximize the rate of
penetration (ROP) of the formation and provide a long service life. The ability of a bit design
to satisfy the two primary goals is constrained by a number of factors such as the wellbore
diameter. Other constraints are dictated by its intended use: formation type to be drilled,
operating environment at depth, the capabilities of the equipment used in the operation and
the angle of the wellbore. The designs of drill bits available these days try to balance these
constraints to achieve the primary goals.
4.6 Safety at drilling Site:

1. Personal Protective Equipment (PPE):

All workers must wear helmets, gloves, safety glasses, flame-resistant clothing, and steel-toe
boots.

2. Blowout Preventer (BOP):

Install and regularly test BOPs to prevent blowouts and uncontrolled fluid releases.

3. Proper Training:
Ensure all personnel are trained in equipment handling, emergency response, and safety
procedures.

4. Emergency Drills:
Conduct regular fire, gas leak, and well control drills to keep the crew prepared.

5. Rig Inspection and Maintenance:

Perform routine checks on rig equipment to identify wear, damage, or malfunctions early.

6. Safe Use of Equipment:

Operate machinery only by authorized and trained personnel; follow standard procedures.

7. Clear Communication:
Use radios, visual signals, and alarms for effective communication across the site.
8. Hazard Identification:
Mark hazardous areas with warning signs and limit unauthorized access.

9. Well Pressure Monitoring:

Constantly monitor well pressure to prevent kicks or sudden fluid influxes.

10. Proper Handling of Chemicals:

Store and handle drilling fluids, fuels, and chemicals safely with proper labeling.

11. Good Housekeeping:

Keep the site clean and organized to prevent slips, trips, and falls.

12. Lightning and Electrical Safety:

Ground all electrical equipment and avoid operations during severe weather.

13. Fire Prevention:

Keep fire extinguishers accessible; avoid smoking and sparks near flammable areas.

14. Fall Protection:

Use safety harnesses and guardrails when working at heights.

15. First Aid Availability:

Ensure a fully equipped first aid kit and trained medical personnel are on-site.

16. Waste Management:

Properly dispose of waste fluids and cuttings to avoid environmental contamination.

17. Fatigue Management:

Rotate shifts to avoid overwork and maintain alertness among workers.

18. Visitor Safety:

Restrict and supervise visitors; provide safety orientation if required.

19. Noise Protection:

Provide ear protection in high-noise zones to prevent hearing loss.

20. Continuous Monitoring and Improvement:

Review safety procedures regularly and update them based on new risks and incidents.
 5.WELL COMPLETIONS
The main purpose of well completion is to make a drilled well ready for safe and efficient
production of oil or gas. It involves a series of operations after drilling to prepare the
wellbore for extraction, control the flow of hydrocarbons, and protect the well structure.

●​ Installing casing and tubing to support the well and prevent collapse.
●​ Placing cement to isolate zones and prevent fluid migration.
●​ Installing production equipment like packers, valves, and perforations to allow controlled
flow.
●​ Ensuring safety and longevity of the well during production.

5.1 TYPES OF COMPLETIONS

Open Hole Completion:

Open hole completions were originally used in the early days of the petroleum Industry when
most wells were drilled with cable tools. Normally, casing was run as the hole was drilled.
When the formation was penetrated and oil and as began to flow, drilling ceased, and the well
was produced as an open hole completion. As rotary rigs began to drill most of the wells, it
was still common to complete cominon to complete a well using an open hole completion. If
the well needed to be stimulated, nitroglycerine was used to rubberize the formation near the
wellbore.
Liner Completion:
Liner completion involves installing a shorter casing string (liner) across the reservoir zone,
which is suspended from the previous casing using a liner hanger. This method is often used
in deep wells to save costs and reduce casing weight. It allows for efficient zonal isolation
and selective production. Liner completions are commonly used when multiple production
zones are targeted or when a full casing string is not economically practical.

●​ Slotted liner
●​ Screen liner
●​ Cemented liner

Perforated Casing Completion:

Perforated casing completion is a commonly used method in

petroleum wells where the production casing is run and
cemented through the reservoir zone, and then holes are
created in the casing and surrounding cement to allow oil or
gas to flow into the wellbore. These holes, known as
perforations, are made using perforating guns equipped with
shaped explosive charges. The process involves first drilling
and casing the well, followed by cementing to seal the
casing in place. Once the cement hardens, the perforating
gun is lowered into the well to the desired depth and fired to
create channels through the casing, cement, and into the
reservoir rock. This method provides excellent control over
the production zones and is ideal for formations that need
support or require selective stimulation. It also allows for
safe and effective application of techniques like acidizing or
hydraulic fracturing. Although it can be more expensive and
requires precise planning, perforated casing completion
offers flexibility, safety, and improved well management.
Single Completion:
The most common method is the single completion in which only one interval is produced at
a time. A single completion is simple and results in fewer operating problems and less cost
than multiple completions. Single very deep, if the formationis very shallow, then drilling
costs are minimal and completions a single completionare usually best. In very deep wells,
single completions are common on land wherethe reservoirs are either shallow or preferred
because of the complexity and expenseinvolved with a dual or triple completion in reservoirs
deeper than 10,000 ft.

Multiple Completion:
In certain cases, multiple completions may provide the best control of reservoir operations, Multiple
completions include the tubing-casing dual, dual tubing strings, and the typical triple completion
consisting of three tubing strings
The more complex the completion, the more trouble one can expect in both completion operations and
in subsequent workover operations. Multiple completions should be considered only in special
situations. These situations include areas where drilling costs are very high or where the area allocated
for drilling wells is at a premium. Such areas include offshore areas, highly populated areas, and
remote land locations.

5.2 COMPLETION COMPONENT

The upper completion refers to all components from the bottom of the production tubing
upwards .proper desig. Of this “ Completion String” is essential to ensure the well can flow
properly given the reservoir conditions and to permit any operations as are needed necessary
for enhancing production and safety

WELL HEAD
Wellhead is the component at the surface of an oil or gas well that provides the structural and
pressure-containing interface for the drilling and production The surface termination of a
wellbore that incorporates facilities for installing equipment. Casing hangers during the well
construction phase. The wellhead also incorporates a means of hanging the production tubing
and installing the Christmas tree and surface flow-control facilities in preparation for the
production phase of thewell. the primary purpose of a wellhead is to provide the suspension
point and pressure seals for the casing strings that run from the bottom of the whole sections
to the surface pressure control equipment. While drilling the oil well, surfacepressure control
is provided by a blowout the column of drilling fluid, casings, wellhead, and BOP, a well
blowout could preventer (BOP), If the pressure is not contained during drilling operations by
occur. When the well has been drilled, it is completed to provide an interface with the
reservoir rock and a tubular conduit for the well fluids. The surface pressure control is
provided by a Christmas tree, whichis installed on top of the wellhead, with isolation valves and
chokes equipment to control the flow of well fluids during production.
Purpose of well Head:
1. Provide a means of casing suspension. Casing is the permanently Installed pipe used to line
the well hole for pressure containment and collapse prevention during the drilling phase.
2. Provides a means of tubing suspension. Tubing is removable pipe installed in the Well
through which well fluids pass
3. Provides a means of pressure sealing and isolation between casing at surface when Many
casing strings are used.
4. Provides pressure monitoring and pumping access to annuli between different
casing/tubing strings
5.Provides a means of attaching a blowout preventer during drilling. 6. Provides a means of
attaching a Christmas tree for production operations.
7.Provides a reliable means of well access & provides a means of attaching a well pump

CHRISTMAS TREE:
In petroleum and natural gas extraction, a Christmas tree, or "tree", is an assembly of valves,
spools, and fittings used for an oil well, gas well, water injection well, water disposal well,
gas injection well, condensate well and other types of wells. It was named for its resemblance
to the Christmas tree. Christmas trees are used on both surface and subsea wells. It is
common to identify the type of tree as either "subsea tree" or "surface tree",
Purpose of Christmas Tree:
The Christmas Tree is a vital surface equipment used in oil and gas wells, designed to
control, monitor, and manage the production of hydrocarbons after a well has been
completed. Named for its resemblance to a decorated tree, it consists of a series of valves,
spools, chokes, and gauges mounted on top of the wellhead. Its main purpose is to regulate
the flow of oil or gas from the well to pipelines or storage facilities, ensuring that production
is both efficient and safe. The Christmas Tree plays a critical role in pressure control by
allowing operators to open, close, or throttle the flow through adjustable valves. It also serves
as a connection point for surface flowlines, measuring instruments, and safety devices.
Additionally, it provides access for injecting chemicals, water, or gas into the well for
enhanced oil recovery or maintenance. It allows for well testing, monitoring of pressure and
temperature, and performing interventions like wireline or coiled tubing operations. In gas
wells, it prevents blowouts by enabling quick shut-in during emergencies. The tree ensures
isolation of the well during shutdowns or repairs, reducing the risk of uncontrolled fluid
release. Some advanced Christmas Trees are equipped with automation and sensors for
remote control and real-time monitoring. Offshore and subsea wells use specially designed
subsea Christmas Trees that function in deepwater conditions. In multi-zone wells, the tree
helps control production from different zones. It is also used to manage sand and water
production and ensure flow assurance. Overall, the Christmas Tree is essential for
maintaining operational control, safety, and integrity of the well throughout its productive
life.
5.3 WELL LOGGING

Well logging, also known as borehole logging, is the practice

of making a detailed record (a well log) of the geological
formations penetrated by a borehole. The log may be based
either on visual inspection of samples brought to the surface
(geological logs) or on physical measurements made by
instruments lowered into the hole (geophysical logs). Some
types of geophysical well logs can be done during any phase
of a well's history:

drilling, completing, producing, or abandoning Well loggingis

performed in boreholes drilled for the oil and gas,
groundwater, mineral and geothermal exploration, as well as
part of environmental and geotechnical studies.

1.Wireline Logging

a. Electric Logs: Resistivity log

Borehole Imaging

b. Porosity Logs: Density log

1.Neutron Porosity
2.Sonic log

c. Lithology Logs: Gamma Ray Log

SP Log

d. Miscellaneous: Caliper

1. Nuclear magnetic resonance

2.Mud Logging
3. Coring
5.4 TYPES OF LOGS :

Resistivity Log:
Resistivity logging measures the subsurface electrical resistivity, which is the ability to
impede the flow of electric current. This helps to differentiate between formations filled with
salty waters (good conductors of electricity) and those filled with hydrocarbons (poor
conductors of electricity).
Borehole Imaging. The term "borehole imaging" refers to those logging and data-processing
methods that are used to produce centimeter-scale images of the borehole wall and the rocks
that make it up. Specific applications are fracture identification. [9] analysis of small-scale
sedimentological features, evaluation of net pay in thinly bedded formations, and the
identification of breakouts.

Density Log:
The density log measures the bulk density of a formation by bombarding it with a radioactive
source and measuring the resulting gamma ray count after the effects of Compton scattering
and photoelectric absorption. This bulk density can then be used to determine porosity.

Neutron Porosity Log:

The neutron porosity log works by bombarding a formation with high energy epithermal
neutrons that lose energy through elastic scattering to near thermal levels before being
absorbed by the nuclei of the formation atoms. Depending on the neutron logging tool, either
the gamma ray of capture, scattered thermal neutrons or scattered, higher energy epithermal
neutrons are detected. The neutron porosity log is predominantly sensitive to the quantity of
hydrogen atoms in a particular formation, which generally corresponds to rock porosity.
Gamma Ray Log:
A log of the natural radioactivity of the formation along the borehole, measured in API units,
particularly useful for distinguishing between sands and shales in a Siliclastic environment.

Self - Potential (SP) Log:

The Spontaneous Potential (SP) log measures the natural or spontaneous potential difference
between the borehole and the surface, without any applied current. It was one of the first
wireline logs to be developed, found when a single potential electrode was lowered into a
well and a potential was measured relative to a fixed reference electrode at the surface.

Caliper Log:
A tool that measures the diameter of the borehole, using either 2 or 4 arms. It can be used to
detect regions where the borehole walls are compromised, and the well logs may be less
reliable.
 6.ONGC MANDAPETA GCS
About Mandapeta Field:
The ONGC started the exploration activity in MANDAPETA area in the year 1993 and struck
Gas in MANDAPETA Well Number-1(MDP#1). The present GCS is located in the location
of the Well Site of the well MANDAPETA#1.
The production from the field has started after commissioning to the GCS on 29/09/1994.
Gas consumers have come up in the vicinity for consumption of gas from the GCS. M/s.
GAIL draws gas from the GCS and adds on to distribution network system for distribution to
consumers.
6.1 DESCRIPTION OF MANDAPETA GCS :
MANDAPETA-GCS is located at about 40 Km from Rajahmundry City.
●​ The fluid from different wells is brought to the GCS through underground flow lines
to the Well Manifold at Installation and then to 3-Phase Separator whereby the gas
and liquid are being separated from fluid
●​ The gas separated supplies to M/s GAIL for further distribution to their Consumers.
The liquid enters into Process Storage tanks where Produced Water is being decanted
from liquid then stores in Storage tanks
●​ The oil thus stored in Process Storage is transported through Road tankers to the Oil
Unloading Station (OUS) at S/Yanam, which collects oil from all production
installations of the Asset for custody transfer.
●​ The Produced Water (Effluent Water) is collected in tanks and transports by Road
tankers to Tatipaka ETP and after transports to KPDA-EPS for further disposal
through injection wells,
●​ There are three numbers of Headers viz. High Pressure Group header, Low Pressure
Group header, and Test header.
●​ Presemly, 14 Nos of wells are connected and 08 No. of wells are flowing and
producing Gas, Oil Condensate and Produced Water (Effluent water).
LP Gas Processing and Compressing ( New facility) :
The wells lootted in this region are prodising at pressure 65-70 kg/g, but ever the period of
time due to agning of Reservies, stie wells prossures ar gradually, depleting hence the same
cannot cater to the GAIL gas distribution network. So, a required to process the LP gas and
comprens it for fooding to the GAIL gas network

7.2 TEST SEPERATOR:

Test separator is an indispensable device in the exploration and development of onahore arid
offshore oil and gas fields It is mainly used in well testing, well clean sups and other flow
operations for efficient and sate separation and measurement of oil gas and water. According
to the form can be divided into horizontal, vertical and spherical
Test separator typically consists of a vessel, an oil flow-measuring system with dual meters, a
flow measuring system for gas, several sampling points for each effluent phase, and two
relief valves to protect the vessel against overpressure. Most separators are also equipped to
measure water flow rate To provide accurate measurements, the test separator is fitted with
pneumatic regulators that maintain a constant pressure and a constant liquid level inside the
vessel by control valves on the oil and gas outlets.
The test separator is fitted with a deflector plate, coalescing plates, a foam breaker, a vortex
breuker, a weir plate, and a mist extractor. These components reduce the risk of carryover
(liquid in gas line) and carry under (gas in liquid line) that would affect the flow rate
measurement accuracy

Horizontal/ vertical Seperators :

According to the installation mode ,the Seperator can be divided in to horizontal/ vertical
installation ,or indoor/ outdoor installation

The horizontal Seperator is built horizontally, in other words, as the vessel shell. axis
parallel to the ground. It is usually used for large liquid/gas ratio fluid treatment or
liquid/liquid separation. Compared with vertical separators, there are longer horizontal
sections for liquid flowing and shorter vertical sections for gravity separation of liquids with
different densities. The horizontal separator requires a relatively large horizontal installation
space, and its application is generally not affected by the field wind.
The vertical Seperator is built vertically, which
means the vessel shell axis is perpendicular to the
ground. It is usually used for large gas/liquid ratio
fluid treatment. Compared with horizontal
separators, there are larger cross-sectional area for
gas flowing and longer vertical sections for gravity
separation of liquids from the gas. The vertical
separator requires a relatively small horizontal
installation space, but for very high or slender
separator the field wind shall be considered. Vertical
separator can be used for test separator, production
separator, two-phase separator, three-phase separator
and special application separator.
6.3 LP Gas Compressor:
At ONGC’s Mandapeta Gas Collecting Station (GCS), a 2-stage compressor plays a crucial
role in handling natural gas efficiently and safely. While specific technical schematics for
Mandapeta aren't publicly detailed, here's how a typical 2-stage compressor functions in such
a setup

●​ Reciprocating Compressors are commonly used in ONGC’s onshore GCS facilities.

●​ These are oil-lubricated, double-acting, two-stage machines designed for
high-pressure gas compression.
●​ They’re often skid-mounted with integrated intercoolers, pulsation dampeners, and
safety systems.
Compressor Capacity:
●​ Though exact figures for Mandapeta aren’t listed, compressors in similar ONGC GCS
units typically handle:
●​ 1.0 to 1.5 MMSCMD (Million Metric Standard Cubic Meters per Day) of gas
throughput.
●​ Discharge pressures can range from 80 to 120 kg/cm², depending on downstream
requirements.

1. First Stage Compression:

●​ Low-pressure gas from the well enters the first cylinder.
●​ It's compressed to an intermediate pressure.
●​ This raises the gas temperature significantly.
2. Intercooling:
●​ The hot gas passes through an intercooler, which cools it down.
●​ Cooling reduces the energy needed for the next stage and protects equipment.

3. Second Stage Compression:

●​ The cooled, partially compressed gas enters the second cylinder.
●​ It's compressed again to the final discharge pressure suitable for downstream
processing or pipeline transport.

6.4 Air Cooled Heat Exchanger :

An air-cooled heat exchanger (ACHE) in a Gas Collecting Station (GCS) like ONGC’s Mandapeta
facility is a key component used to cool process fluids—typically natural gas or condensate—using
ambient air instead of water. This is especially useful in remote or water-scarce regions
1. Hot process fluid flows through finned tubes.
2. Fans (either forced or induced draft) blow or draw ambient air across these tubes.
3. Heat transfers from the fluid to the air, cooling the fluid before it moves to the next stage.

In Mandapeta GCS, the ACHE likely cools compressed gas before it’s sent to pipelines or further
processing, helping maintain safe temperatures and system efficiency.
6.5 GAS DEHYDRATION UNIT :
Glycol dehydration is a liquid desiccant system for the removal of water and hydrocarbons from
natural gas. It is the most common and economical means of water removal from these streams. TEG
is the most commonly used glycol in industry. The gas produced from a GCP, usually contains a large
amount of water and is typically completely saturated or at the water dew point. This water can cause
several problems for downstream processes and equipment. At low temperatures the water can get
freeze in piping or, as is more commonly the case, form hydrates with CO2 and hydrocarbons (mainly
methane hydrates). Depending on composition, these hydrates can form at relatively high
temperatures plugging equipment and piping. Glycol dehydration units depress the hydrate formation
point of the gas through water removal. Without dehydration, a free water phase (liquid water) could
also drop out of the natural gas as it is either cooled or the pressure is lowered through equipment and
piping This free water phase will often contain some portions of acid gas (such as H2S and CO2) and
can cause corrosion. For the above two reasons the Gas Processors Association sets out a pipeline
quality specification for gas that the water content should not exceed 7 pounds per million standard
cubic feet.

Glycol dehydration units must typically meet this specification at a minimum, although further
removal may be required if additional hydrate formation temperature depression is required, such as
upstream of a cryogenic process

Tri Ethylene glycol:

Triethylene glycol (TEG) plays a crucial role in a Gas Dehydration Unit (GDU)—its main job is to
remove water vapor from natural gas. This is essential because moisture in natural gas can lead to
problems like pipeline corrosion and hydrate formation, which can block flow and damage
infrastructure.
Natural gas flows upward through a contact tower while lean TEG (dry glycol) flows downward. As
they interact, the TEG absorbs the water vapor from the gas. The now “rich” TEG (full of water) is
then regenerated—heated to remove the absorbed water—and reused in the cycle.
Shell & Tube Heat Exchanger:
In a Gas Dehydration Unit (GDU), the shell and tube heat exchanger plays a key role in energy
recovery and efficiency—especially during the regeneration of Triethylene Glycol (TEG).

●​ The heat exchanger transfers heat from the hot, regenerated (lean) TEG to the cooler,
water-rich (rich) TEG coming from the absorber. This preheats the rich TEG before it enters
the reboiler, reducing the energy needed for regeneration.

●​ Typically, the lean TEG flows through the tube side, while the rich TEG flows through the
shell side (or vice versa, depending on design). The two fluids never mix—they just exchange
heat through the tube walls.

●​ As the hot lean TEG exits the reboiler, it passes through the exchanger and transfers its heat
to the incoming rich TEG. This cools the lean TEG before it returns to the absorber and
warms the rich TEG before it enters the reboiler.

●​ This setup improves thermal efficiency, reduces fuel consumption in the reboiler, and helps
maintain stable operating temperatures.

Plate type Heat Exchanger:

In a Gas Dehydration Unit (GDU), a plate-type heat exchanger serves a similar purpose to a
shell-and-tube exchanger but with a more compact and efficient design. Its main role is to
transfer heat between the rich and lean Triethylene Glycol (TEG) streams.
●​ It preheats the incoming rich TEG (loaded with water) using the hot lean TEG (freshly
regenerated), reducing the load on the reboiler.
●​ Plate heat exchangers offer high heat transfer efficiency in a smaller footprint, which is ideal
for space-constrained installations.
 ●​ They’re easier to clean and maintain compared to traditional exchangers, especially in
modular GDU setups.
●​ The corrugated plates create turbulence, which improves heat transfer and reduces fouling.

Reboiler& Flash Tank:

In a Gas Dehydration Unit (GDU), both the reboiler and the flash tank are essential for
regenerating Triethylene Glycol (TEG) so it can be reused to dry natural gas.
●​ Heat the rich TEG (which has absorbed water from the gas) to around atmospheric
pressure.
●​ Boil off the water from the glycol, turning it back into lean (dry) TEG.
●​ Ensure the glycol is ready to be reused in the absorber tower.

The flash tank (also called a gas-condensate-glycol separator) serves a few key purpose
●​ Reduces pressure of the rich glycol before it enters the reboiler.
●​ Separates entrained gas and light hydrocarbons from the glycol to prevent vapor lock
or foaming in the reboiler.
●​ Helps recover valuable condensates and minimizes emissions.

Filters:
In a Gas Dehydration Unit (GDU), these filters are vital for keeping the Triethylene Glycol
(TEG) clean and the system running smoothly. Here’s a quick breakdown

Pre-Filter
Captures large solid particles like rust, scale, and debris before they reach sensitive
equipment.
Charcoal (Carbon) Filter
Removes dissolved hydrocarbons, compressor oils, and degradation products from the glycol.
After Filter
Final polish—removes any remaining fine particulates or carbon dust after the charcoal filter.

Burner Management system:

A Burner Management System (BMS) is a critical safety and control system used in
industrial processes—like in a Gas Dehydration Unit (GDU)—to ensure the safe startup,
operation, and shutdown of burners.
Safety First
●​ Monitors flame presence using flame detectors.
●​ Prevents fuel flow if no flame is detected, avoiding unburned gas buildup.
 ●​ Executes emergency shutdowns (Master Fuel Trip) if unsafe conditions arise—like
low fuel pressure or high furnace pressure.

Sequencing & Control

●​ Manages the startup sequence: purge → pilot ignition → main burner ignition.
●​ Controls shutdown procedures in a safe, orderly manner.
●​ Ensures all interlocks and permissives are satisfied before allowing burner operation.
Integration & Monitoring
●​ Interfaces with PLC or DCS systems for real-time monitoring and diagnostics.
●​ Can be standalone or integrated with the plant’s safety instrumented system (SIS).
●​ Often designed to meet SIL (Safety Integrity Level) standards for critical applications.

6.6 MECHANICAL REFRIGERATION UNIT:

In a Gas Dehydration Unit (GDU), a Mechanical Refrigeration Unit (MRU) is used to cool natural gas
to very low temperatures, allowing for the condensation and removal of heavier hydrocarbons and
water vapor. This process helps in achieving the required dew point specifications for pipeline
transport and enhances the recovery of Natural Gas Liquids (NGLs) like propane, butane, and
condensates43dcd9a7-70db-4a1f-b0ae-981daa162054. By lowering the gas temperature, the MRU
prevents hydrate formation and corrosion issues downstream, especially in cryogenic or high-pressure
systems. It’s a vital component when high-efficiency dehydration and liquid recovery are needed
beyond what glycol systems alone can achieve.

Mono Ethylene Glycol:

Monoethylene Glycol (MEG) is used in a Mechanical Refrigeration Unit (MRU) primarily as a
hydrate inhibitor. In natural gas processing, especially in cold environments or high-pressure systems,
there's a risk of hydrate formation—ice-like crystals that can block pipelines and damage equipment.
MEG helps by lowering the hydrate formation temperature, keeping the gas flow smooth and
uninterrupted.

Once injected into the gas stream, MEG absorbs water and prevents hydrates from forming. The
resulting “rich MEG” (containing water and impurities) is then sent to a MEG Recovery Unit (MRU),
where it’s regenerated and purified for reuse. This closed-loop system is both cost-effective and
environmentally friendly, reducing the need for constant chemical replenishment.
 7. KALAVACHARLA WORKOVER
RIG
A workover rig is a specialized piece of equipment used in the oil and gas industry to perform
maintenance, repair, or enhancement operations on an existing well after it has been drilled and
completed. Unlike drilling rigs, which are used to create new wells, workover rigs are deployed to
restore or improve the productivity of wells that are underperforming, damaged, or nearing the end of
their operational life. These rigs are essential for a wide range of tasks, including replacing downhole
pumps, clearing obstructions, repairing tubing, sealing leaks, or even modifying the well’s completion
to access new reservoir zones. They are also used for well interventions, such as acidizing, hydraulic
fracturing, or installing new perforations to stimulate production. In some cases, workover rigs are
employed to plug and abandon wells that are no longer economically viable, ensuring environmental
safety and regulatory compliance. The rig is typically mobilized when a well shows signs of declining
output, mechanical failure, or when there's a need to adapt the well for a different purpose—like
converting it from production to injection. Because these operations often involve invasive techniques
like wireline, coiled tubing, or snubbing, workover rigs are designed to handle complex and delicate
procedures with precision and safety. Their use is critical in maximizing the lifespan and efficiency of
oil and gas wells while minimizing downtime and operational risks.
Workover rig at KALAVACHARLA
7.1 JOBS AT WORK OVER RIGS :
In petroleum production, workover rigs are used for maintenance, repair, or enhancement of oil and
gas wells that are already in production. Two of the most commonly used methods during workover
operations are:

Coiled Tubing Unit (CTU) Operations:

Coiled Tubing Unit (CTU) is a versatile, efficient, and less invasive method used in well
interventions. The CTU consists of a continuous length of small-diameter steel tubing spooled on a
reel, which can be inserted into the well without removing the wellhead.
1. Well Cleanouts:
●​ Removal of sand, scale, wax, or debris blocking production flow.
●​ Using nitrogen lifting, solvents, or chemical washes.

2. Acid Stimulation:
●​ Pumping acid into the reservoir to dissolve carbonate formations and increase permeability.
●​ Enhances oil and gas flow from near-wellbore zone.

3. Fishing Operations:
●​ Retrieving dropped or stuck equipment inside the wellbore using specialized CT tools.

4. Logging and Perforation:

●​ Deploying sensors to collect data (temperature, pressure, etc.).
●​ Using CT to deploy perforation guns to create new flow paths in casing.

5. Cementing Jobs:
●​ For zonal isolation or sealing off unwanted water zones.
●​ CT allows precise placement of cement.
6. Scale Removal and Inhibitor Injection:
●​ Pumping scale dissolvers or corrosion inhibitors.

7. Hydraulic Fracturing (in some cases):

●​ Mini-fracs or re-fracturing jobs via CT.

Nitrogen (N₂) Lifting / Jetting Jobs

Nitrogen is an inert, non-flammable gas often used to lighten the hydrostatic column in a well or
remove fluids to restore production.

1. Well Kick-off (Initial Start-up):

●​ After drilling or a workover, nitrogen is used to lighten the fluid column and help bring the
well into production.

2. Well Lifting:
●​ Injecting nitrogen reduces hydrostatic pressure, allowing reservoir fluids to flow

3. Well Cleaning / Debris Removal:

●​ N₂ jetting clears sand, wax, or liquid slugs from the wellbore or tubing.

4. Foam Lift:
●​ Nitrogen is injected with surfactants to create foam and lift heavy fluids.

5. Underbalance Operations:
●​ Maintaining pressure lower than formation pressure using N₂ to avoid formation damage
during interventions.

6. Inert Environment Creation:

●​ To prevent oxidation or combustion during hot work (welding, cutting).

Non-invasive and faster than traditional rigs.

Can be performed under pressure (live well intervention).

Reduce downtime and enhance well productivity.

Environmentally safer (especially N₂ as it is inert and dry).

 8.ARTIFICIAL LIFT

Artificial lift is a vital method used in oil and gas production to enhance the flow of
hydrocarbons from the reservoir to the surface when natural pressure is insufficient. In
ONGC (Oil and Natural Gas Corporation), artificial lift systems play a crucial role in
maintaining and improving production rates from mature and low-pressure wells. The
primary purpose of artificial lift is to increase reservoir recovery by reducing the bottom-hole
pressure, allowing more oil to flow into the wellbore. Techniques such as sucker rod
pumping, gas lift, electric submersible pumps (ESP), and progressive cavity pumps are
commonly employed based on well conditions. These methods are especially essential in
ONGC's ageing fields, where reservoir energy has declined over time. By using artificial lift,
ONGC ensures consistent production, optimizes reservoir performance, and extends the
economic life of oil wells, thereby contributing to the efficient and sustainable exploitation of
India's hydrocarbon resources.
8.1 TECHNIQUES USED IN ARTIFICIAL LIFT:

Artificial lift techniques are used in oil and gas wells to increase the flow of fluids when
natural reservoir pressure isn't enough to bring them to the surface. Here are the most
common methods

1. Sucker Rod Pump

2. Electric Submersible Pump (ESP)
3. Gas Lift
4. Progressive Cavity Pump (PCP)
5.Plunger Lift
6.Jet Pump

8.1.1 GAS LIFT:

Gas is injected into the annulus (the space between the tubing and casing) and enters the production
tubing through gas lift valves. This injected gas mixes with the produced fluids, reducing their density
and hydrostatic pressure. As a result, the reservoir pressure becomes sufficient to push the lighter fluid
column to the surface.
●​ The well is completed with side pocket mandrels installed in the tubing to house gas lift
valves.
●​ Tubing is run into the well, and a packer is set above the perforations to isolate the annulus.
●​ The casing and tubing are pressure-tested to ensure integrity.
●​ Dummy valves placed during installation are retrieved using a kickover tool via wireline.

●​ Actual gas lift valves are installed in the mandrels at calculated depths.
●​ Compressed gas is injected into the annulus from a surface compressor.
●​ Gas enters the tubing through the lowest operating valve (based on pressure differential).
●​ The injected gas aerates the fluid column, reducing its density and allowing reservoir
pressure to lift it to the surface.
●​ Continuous gas lift: Gas is injected constantly for high-rate wells.
●​ Intermittent gas lift: Gas is injected in cycles for low-rate wells.
This method is especially effective in deviated wells, high GOR reservoirs, and wells with sand or
scale issues.

8.1.2 SUCKER ROD PUMP :

A sucker rod pump (SRP), also known as a beam pump, is one of the most widely used artificial lift
systems in the oil and gas industry—especially effective in low-to-medium production wells.
●​ A prime mover (usually an electric motor) drives the crank arm of the surface unit.
●​ The crank arm rotates, moving the walking beam up and down. This motion is transferred to
the polished rod and sucker rod string.
●​ The plunger moves downward inside the pump barrel.
●​ The traveling valve opens, allowing fluid to pass through the plunger.
●​ The standing valve remains closed, keeping fluid in the pump barrel.
●​ The plunger moves upward.
●​ The traveling valve closes, trapping fluid above the plunger.
●​ The standing valve opens, allowing new fluid to enter the pump barrel from the reservoir.
●​ The trapped fluid above the plunger is lifted to the surface through the tubing with each
upstroke.
●​ This cycle repeats, lifting fluid to the surface in pulses with each stroke.

8.1.3 PLUNGER LIFT :

A plunger lift system is a type of artificial lift used primarily in gas wells to remove
accumulated liquids (like water or condensate) that hinder gas production. It’s a clever,
energy-efficient method that uses the well’s own pressure to lift liquids to the surface.

●​ A free-traveling plunger (a metal or plastic piston) is dropped from the surface into
the well. It falls to the bottom of the tubing, typically landing on a bumper spring or
seating nipple.
●​ With the well shut in, reservoir pressure builds beneath the plunger and the
accumulated liquid column.
●​ When the well is opened, the built-up pressure pushes the plunger and the liquid slug
above it to the surface. The plunger acts like a piston, reducing fallback and
improving liquid removal efficiency.
●​ Once the plunger reaches the surface, it’s captured in a lubricator. The cycle then
repeats.
8.1.4 PROGRESSIVE CAVITY PUMP:

A progressive cavity pump (PCP) is a type of positive displacement pump designed to handle viscous,
abrasive, or shear-sensitive fluids with precision and consistency. Here's how it works:
At its core, a PCP consists of:
Rotor: A single-helix metal shaft.
Stator: A double-helix elastomer sleeve that forms cavities with the rotor.
As the rotor turns inside the stator, it creates sealed cavities that progress from the suction to the
discharge end. These cavities trap and move fluid forward in a smooth, non-pulsating flow. This
makes PCPs ideal for applications where maintaining fluid integrity is crucial.
●​ Fluid enters the pump through the inlet.
●​ The rotating rotor forms cavities with the stator.
●​ These cavities carry the fluid forward as the rotor turns.
●​ The fluid exits the pump in a steady stream.
8.1.5 ELECTRIC SUBMERSIBLE PUMP:
An ESP is essentially a multistage centrifugal pump driven by a submersible electric motor. It
operates under the surface, submerged in the well fluid. The motor powers a shaft connected to a
series of impellers and diffusers that incrementally boost the pressure of the fluid, lifting it to the
surface.
●​ A sealed electric motor at the bottom drives the shaft.
●​ Each stage (impeller + diffuser) adds head to the fluid.
●​ Fluid enters through the intake above the motor.
●​ Removes free gas to prevent cavitation.
●​ Pressurized fluid exits the pump and flows up the tubing to surface facilities.

8.1.6 JET PUMP:

A jet pump is a type of artificial lift system that uses the Venturi effect to lift fluids from a well
without any moving parts downhole

●​ High-pressure power fluid (usually treated produced water or oil) is pumped from the surface
down the tubing to the jet pump nozzle
●​ The power fluid passes through a converging nozzle, converting pressure energy into high
velocity. This creates a low-pressure zone at the nozzle exit
●​ The low-pressure zone draws in reservoir fluids through the pump intake. These fluids mix
with the power fluid in the throat section.

●​ In the throat, the high-velocity power fluid transfers momentum to the reservoir fluid,
entraining it and forming a combined flow.
●​ The mixed fluid enters the diffuser, where the flow area increases. This slows the fluid
velocity and converts kinetic energy back into pressure, allowing the fluid to be lifted to the
surface.
 ●​ The combined fluid (power + reservoir) flows up the annulus (or tubing, depending on
completion) to surface separation and processing facilities.

8.2 SAFETY MEASURES WHILE INSTALLING ARTIFICIAL

LIFT SYSTEM
1. Wear Full PPE (Personal Protective Equipment):
Use safety helmets, gloves, safety goggles, steel-toed boots, flame-resistant clothing, and hearing
protection during all operations.

2. Inspect Tools and Equipment Before Use:

Ensure that hammers, spanners, slings, and lifting devices are in good condition and free from defects.
Damaged tools must not be used.

3. Proper Handling of Counterweights:

Counterweights are heavy and dangerous. Use proper lifting techniques and equipment like chain
blocks or cranes. Never try to lift manually

4. Secure the Work Area:

Use barricades and signs to restrict unauthorized access. Ensure no one is standing under suspended
loads.

5. Use Hammering Shields & Controlled Force:

While hammering, use hammering shields or clamps to prevent accidental slipping or metal fragment
injuries. Avoid excessive force that can cause tool rebound.

6. Check Thread Alignments Before Fixing Nuts/Bolts:

Misalignment can cause stripping of threads or tool slips. Always align components correctly before
tightening.

7. Use Torque Wrench Where Required:

Over-tightening or under-tightening can be hazardous. Follow manufacturer torque specifications
when tightening nuts and bolts.

8. Keep Hands Clear from Pinch Points:

While lowering or aligning lift components, keep fingers away from joints, hinges, or rotating parts to
prevent crush injuries.

9. Communication and Signaling:

Always have a clear communication protocol between ground crew and lifting equipment operator.
Use hand signals or radios.

10. Emergency Response Ready:

Keep first-aid kits, fire extinguishers, and emergency shutdown protocols nearby. Crew
should know emergency procedures and evacuation routes.
 9.ONGC TATIPAKA
ONGC Tatipaka, located in the East Godavari district of Andhra Pradesh, is a significant onshore
production hub under the Rajahmundry Asset. It was discovered in the early 1980s, with the first
successful well drilled around 1985. The area has seen continuous development since then. Around
70+ wells have been drilled, and approximately 40–45 wells are currently active and producing
hydrocarbons. The main products from Tatipaka include crude oil, natural gas, and gas condensate.
The processing operations at the Tatipaka Gas Processing Complex (GPC) involve gas-liquid
separation, dehydration, H₂S removal (sweetening), compression, and condensate stabilization. Key
units inside ONGC Tatipaka include the Gas Processing Unit (GPU), Oil Collecting Station (OCS),
Dehydration Unit, Test Separator Unit, Gas Sweetening Unit, Condensate Storage, and Gas
Compression Station.

The output is divided into three major streams:

1. Dry Natural Gas – supplied to industries, power plants, and domestic distribution.
2. Condensate/Crude Oil – transported to refineries.
3. LPG/NGLs – sent to processing units like the Odalarevu GCP

The sub-products from processing include LPG (Liquefied Petroleum Gas), NGLs (Natural Gas
Liquids) like propane and butane, stabilized condensate, and sulfur (recovered during sweetening).
Tatipaka also contributes to domestic gas supply, making it a crucial part of ONGC's eastern
operations.