Introduction

In Myanmar, most of the on-land oil fields can be found just on both sides of
Ayeyarwaddy river, and thus there was a saying that the oil is being produced on Myitkyina
Theory (Literally meaning as Near-the-river). Starting from Letpando, Ayadaw, Yenangyat,
Chauk, Lanywa, and Yenangyaung, and so on, all the oil fields were established along
Ayeyarwaddy River since years back. Regarding that discovery, some of the professionals
said:

“The transportation and deposition from mountain ranges and plateau like Bago and
Rakhine have been accumulated at the down side (where the rivers are flowing) for millions
of years. Additionally, the sedimentation of main rivers like Ayeyarwaddy and Chindwin,
also supported that accumulation, and subsequently the chances of oil prospect related to
those rivers.” Discovery of oil basins at offshore is the same analogous theory of
sedimentation. Mann Oil Field is also a proof of that so-called “Myitkyina (Near-the-River)
Theory.”

Referring to the name of the creek flowing in that area, originated from Rakhine
mountain ranges, that field is called “Mann Oil Field.” That field is one of the essential on-
land oil field in Myanmar. It was first discovered in April 1970. It is situated at the northern
part of Minbu geological structure which is plunging to Salin Basin. Gravity survey and
Seismic Data Acquisition were conducted in 1966 and subsurface geology with oil prospect
was unearthed.

It is Asymmetrical Anticline with high angle dip at the east. Longitudinal Faults and
Cross Faults are dividing along the north-south structure. Blocks are also demarcated
according to that faults where the sand layers at the north are deeper as those at the south are
shallower.

The reservoir is first produced with natural drive energy to displace hydrocarbon from
reservoir up to surface. Due to the production of oils for several years, the reservoir is
depleted gradually. As the production time goes on, changes in the physical properties occur
in the reservoir such as a decrease in reservoir pressure and a decrease in well productivity.

Changes in the physical properties of the reservoir will affect the performance of the
sucker rod pump. At this time reservoir pressure drops below bubble point pressure. With the
depletion of the reservoir pressure during time by time production, other implementation
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methods (such as artificial lift methods) are required for oil production. Most of the wells in
Mann Oil Field produce fluid using artificial lift equipment. Sucker rod pumping is the most
widely used artificial lift method. That is, more artificial lift wells are equipped with rod
pumps than any other type of artificial lift method.

Many different pumping systems are in current use, e.g., conventional sucker rod
pumping, long-stroke pumping, hydraulic, centrifugal, and sonic pumping. Sucker rod
pumping system is so common and mechanically so simple. Therefore, the artificial lifting
equipment that is commonly used in Mann Oil Field is sucker rod pump.

Among sucker rod pumping wells in that field, this thesis must analyze about 2 (or) 3
sucker rod pumping wells performance. The performance of the sucker rod pump is
influenced by the characteristics of the well and reservoir such as pressure, well productivity,
physical properties of the fluid, depth and diameter of the well.

The wells produce fluid from Mann Oil field’s reservoirs (e.g., Kyaukkok, Pyawbwe,
Okhmintaung and upper Padaung Sands. Shwezetaw formations). In order to produce fluid
using the pump optimally, it is necessary to adjust the pump speed (N) and stroke length (S).

So that in this study an allowable stroke length was selected that produces at the
optimum flow rate. As mentioned above that reservoir pressure declines as production time
increases. A decrease in reservoir pressure results in a decrease in flow rate in the future.
Accordingly it is necessary to adjust stroke length in the future. In addition, the decline in
production rate and reservoir pressure will affect the requirement of horse power. Based on
the background that has been described, then several things can be analyzed, such as the
allowable stroke length for that wells that provide optimum production rates and future
production rate and stroke length adjustment due to reservoir pressure decline.

Aim and Objective

The main aim of the thesis is to analyze the performance of sucker rod pumping wells
and forecast production in the future. The objective is to design a pump at that wells and to
analyze production rate changes and stroke length adjustment in the future. The flow rate
determination is obtained from the point of intersection between the pump intake pressure
curve and IPR (Inflow Performance Relationship) curves both in the present and in the future,
and to construct the IPR curve for analyzing the pressure maintenanc
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Problem Statement

The main problem in Mann Oil Field is the decline of pressure and production rates.
There are two main causes of these factors, either the bottomhole flowing pressure drops to a
level at which it is no longer sufficient in overcome pressure losses in the well, or the flowing
pressure losses become greater than the bottomhole pressure necessary for the well to
produce.

The first case happens due to the removal of fluids from the underground reservoir
and entails a gradual decrease in reservoir pressure. In second case is mechanical problems
(too-small tubing size, downhole restrictions, etc). In Mann Oil Field, sucker rod pumping
method is most useful artificial lift method. As for the solution, this thesis must analyze about
2 (or) 3 sucker rod pumping wells performance in that field.

The surface and downhole equipment for a rod-pumped well are shown in Figure (1)
and (2). The rotary motion of the crank is translated to a is translated to a reciprocating
motion of the polished rod by the Pitman and the walking beam: the sucker rods transmit the
reciprocating motion from the polished rod to the downhole pump.

The pump consists of a barrel with a ball-and-seat check valve at its bottom (the
standing valve) and a plunger containing another ball-and-seat check valve (the traveling
valve). When the plunger move up, the standing valve opens, the travelling valve closes, and
the barrel fills with fluid. On a down stroke, travelling closes, and the fluid in the barrel is
displaced into the tubing.

Sucker rod pump is positive-displacement pump. That pump performance is evaluated

based on the volume of fluid displaced, not the pressure increase generated by the pump,
since the compression of the wellbore fluid in the pump will create enough pressure to
displace th fluid in the tubing. The volumetric flow rate displaced by a rod pump is;

q = 0.1484N

where q is the downhole volumentric flow rate (bbl/d), N is the pump speed (strokes per
minute, spm), is the volumetric efficiency, is the volumetric efficiency, is the plunger
cross-sectional area ( ), and is the effective plunger stroke length (in). The surface
production rate is the downhole rate divided by the formation volume factor.
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The volumetric efficiency is less than 1 because of leakage of the fluid around the
plunger. The volumetric efficiency is usually 0.7-0.8 for a properly working rod pump.

Figure (1) Typical Sucker-Rod Pump Figure (2) Rod Pump

METODOLOGI

The thesis procedure carried out in this study is shown in Figure (3). Basically the
thesis stages include data collection, pump optimization, and prediction of pump performance
in the future. The procedure of the thesis is as follows:

1. Plot the Inflow Performance Relationship (IPR) Curve (Inflow Curve).

2. Prepare the Pump Intake Pressure Curve. To make a pressure curve into the pump
(plunger) it is necessary to calculate constants a, b, c. The steps required are:
a) Select the type of Sucker Rod and rod weigh.
b) Select the steel quality.
c) Determination of Crank to Pitman ratio.
d) Determination of Crank to Pitman ratio.
e) Determination of the constant K.
f) Determination of weight of Sucker Rod in the air, Wr.
g) Determination of constants b and c.
h) Calculation of Sectional Sucker Rod Top Sect Area, ATr.
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i) Specific calculations of fluid gravity (oil and water).

j) Calculation of fluid (water and oil) weight that fill in the Plunger (Wf).
k) Determination of parameter a.
l) Plot Pump Intake Pressure Curve (Outflow Curve).

Figure (3) Flow Diagram of the Thesis

3. Determination of Flow Rate (q) in the Present and Future.

4. Calculation of Polished Rod Material Strength The strength of the polished rod
material needs to be calculated. The calculated parameters are:
a) Maximum polished rod load.
b) Minimum polished rod load.
c) Constants 1 and 2.
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d) Maximum stress, max, minimum stress, min, allowable, and allowable stress,
allowable.

The first step is data collection and preparation. The collected data include the data of
reservoir physical properties and data of about 2 (or) 3 wells in Mann Oil Field. The change
in reservoir pressure and water cut in the future. The estimated decline of the reservoir
pressure was used to construct inflow performance relationship curves. Future IPR curves can
be estimated future reservoir pressure. Pump intake pressure curve is a curve that relates fluid
pressure (P) and flow rate (q) that enters the pump. If the plunger is located at the bottom of
the well, the pump inlet fluid pressure (P) is equal to the bottom well pressure (Pwf).

CONCLUSIONS

Sucker rod pumping artificial lift method is currently used in Mann Oil Field. The
role of sucker rod pumping well performance is influenced the well pressure and flow rate.
With the help of the IPR curve and pump intake pressure curve, future performance is also
predicted.

At the condition of reservoir pressure Pr is low bubble point pressure, the IPR
equation can be used to depict the relationship between flow rate and bottom hole pressure.

The possible flow rates in the present and future time can be obtained from the
intersection between the IPR (inflow) curve and the pump inlet pressure curve. Based on that
curves, it can be concluded that:

i. At pump speed (N) the sucker rod pump is estimated to produce liquid flow rate and
stroke length (S).
ii. The flow rate of the sucker rod pump is reduced due to a decrease in reservoir
pressure in the future.
iii. The pump stroke length (S) needs to be reduced due to the decrease of flow rate.

REFERENCES

1) https://images.app.goo.gl/Qa8eUTEMESuBTs1V8.
2) https://www.researchgate.net.
3) https://www.sciencedirect.com/topics/engineering/rod-pumping-system.
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4) M. F. Sabaruddin, I. M. Azmi, C. E. F. Firdaus, M. R. Shahrazade, “Optimization and

Prediction of Sucker Rod Pump Performance on Well X-1 in Field X in the Future”
by Journal of Earth Energy Science, Engineering, and Technology, Vol. 2, 2019.
5) Michael J. Economides A. Daniel Hill Christine Ehlig-Economides Ding Zhu,
“Petroleum Production Systems, Second Edition” by Pearson Education, Inc.
6) T. E. W. NIND, Associate Professor, Department of Geological Sciences, University
of Saskatchewan, “Principles of Oil Well Production” by McGraw-Hill, 1964.
7) THAN TUN (oil), “OIL FIELDS OF MYANMAR”.