Introduction
The Petroleum Industry
Includes multiple stages:
Exploration, Extraction, Refining, Transportation,
Marketing.
The main products are fuel oil and gasoline.
Petroleum is a raw material for many chemical
products:
Pharmaceuticals, fertilizers, plastics and pesticides.
The industry is divided into 3 sections:
Upstream, Mid stream and Downstream.
Introduction
Importance of Petroleum Exploration Methods
The impact on the environment due to:
Drilled rock cuttings, Seismic operations, Accidental discharges.
Identification of type of reservoir and porosity of rock.
Verification that the location was not previously drilled by
another company.
Reduction of costs and time of Drilling procedure.
Role of Petroleum Geologists
Analyse data and prepare reports.
Determine whether the area is viable for drilling.
Identification of high-pressure zones.
Exploration Techniques
Geochemical Methods
Conducted to reduce risks associated with exploration. Remote
Sensing
Molecular composition and Isotopic composition of
Gases.
Isotope
Magnetic
Biomarker compositions of Oils. ratio
Method
Analysis
Hydrocarbon maturity, continuation of reservoir,
migration and accumulation processes. Exploration
Techniques
Geophysical Methods Biomarker Gravity
Analysis Method
The study of physical properties of the subsurface rocks:
Density, Magnetic and Acoustical.
Seismic
Gravity, magnetic and seismic methods are usually Method
combined for more accurate results.
Geochemical Methods
Biomarker Analysis
Found in oils, rock extracts, recent sediments and
soil extracts.
They are analyzed using gas chromatography and
mass spectrometry.
Used to estimate the migration pathway of
petroleum deposits.
Isotopic Analysis
Isotopic ratios analyzed to determine hydrocarbon
origin.
Used to estimate the accumulation of oil and gas.
Remote Sensing
The use of aerial photographs to locate and map
surface features.
Satellite imagery reveals soil moisture, mineral
and vegetable distribution and soil type.
How does Remote Sensing work?
An energy source is required, this is the light from
the Sun.
A satellite sensor records the reflected
electromagnetic radiation.
A computer processes the electronic information
into an image.
Magnetic Surveying
Definition
Magnetic surveying is a method used to investigate subsurface geology on the
basis of anomalies that occur in the Earth’s magnetic field.
Survey Routes
Airborne/Aeromagnetic is more advantageous as it covers a larger area within a
smaller time frame.
Instrumentation
A magnetometer is a complex instrument that measures both the orientation and
strength of a magnetic field.
Proton Precession and Gradiometer are common types of magnetometer systems
used within industry.
Magnetic Surveying
Magnetic Surveying Results
A magnetic reading profile across a dyke
Gravity Surveying
Definition
Gravity surveying measures the change in rock density by looking at changes in
gravity.
The strength of the gravitational field is directly proportional to the density of
the subsurface materials.
Survey Routes
Ground-based approach used as these surveys are the most sensitive.
Instrumentation
A gravimeter is used to measure the variations in the Earth’s gravitational field.
Worden and the Scintrex are common types of gravimeters used within industry.
Gravity Surveying
Gravity Surveying Results
Gravity profile across a buried salt dome
Seismic Surveying
Definition
Seismic surveying involves sending strong pressure/sound waves through the
earths surface and then receiving the reflected waves of the various surfaces of
the subsurface rock layers.
Sound waves can be created using huge land vibrators or explosives.
Survey Routes
Ground based surveying route.
Instrumentation
Seismograph -records the arrival of seismic waves with respect to time.
Geophone - small receivers that detect and convert the mechanical energy
(wave) to electrical voltages.
Seismic Surveying
Types of Seismic Surveying
Seismic refraction:
Occurs when the sound wave travels
through an upper medium and
along an interface and
then back to the surface.
Method used for mineral
investigations
Seismic Refraction
Seismic Surveying
Types of Seismic Surveying
Seismic reflection:
Occurs when the sound wave travels
down to a geological interface and then
reflects back to the surface.
Method used for oil and gas exploration.
Seismic Reflection
Conclusion
Geochemical and geophysical exploration methods were assessed for the petroleum
industry.
The magnetic and gravity methods must be paired with other data sets.
The seismic reflection surveying was selected as the suitable exploration method
• Accurate surveying method
• Subsurface layering and mechanical properties provided
• Method with best resolution of features.
References
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