IN THE NAME OF ALLAH, THE MOST GRACIOUS, THE MOST MERCIFUL

MEHRAN UNIVERSITY COLLEGE OF ENGINEERING AND TECHNOLOGY KHAIRPUR MIR’S, SINDH,PAKISTAN

Department of Petroleum and Natural Gas Engineering2nd term 2nd year 11-Batch

Presentation by Group no. 09

Subject:- Petroleum Geology and Exploration

Teacher:- Mr. Faisal Hussain MemonGroup leader:-Abdul Basit (K-11PG46)

Group Members:-Ahsan Ali (K-11PG91) Shafiullah Sheikh (K-11PG83)

Muhammad Yasin (K-11PG36)

Topics…!1. Origin of petroleum by M.Yasin2. Petroleum traps by Shafiullah Shaikh

3. Abnormal pressure by A.Basit

4. Exploration techniques by Ahsan Ali

Origin of Petroleum…!

No any particular origin of petroleum. Some geologist believed , source material

deposited on shale and transforms into petroleum.

Some concepts assumes for oil transportation along with undergoing circulating water.

• Origin of petroleum is based on two theories

1. Organic theory2. Inorganic theory

Organic theory95% scientists believe in the organic theory.Organic theory commands that the oil and gas

are formed from the remains of plants, animals and insects.

Some believe that it is formed from the dinosaurs.

Some are giving its credit to small organisms living in earth like ants.

Some believe that it is formed due to marine organisms.

Some regard this as the convergence of phytoplankton into petroleum.

Hydrocarbon formed from dinosaurs

Inorganic theory Only 5% scientists believe in inorganic theory. In 1928 Fredic Wohler discovered urea from

inorganic material.He proved that we can get organic compound

from inorganic compound.

Petroleum Traps…!

Petroleum Traps • A trap is an arrangement of rock layers that

contains an accumulation of hydrocarbons.• The trap consists of an impermeable layer of

rock above a porous, permeable layer containing the hydrocarbons.

• The impermeable layer is termed as caprock.• Traps come in all shapes, sizes and types.

Mechanism of trap

Classification of traps• Geologists have divided traps into two basic

groups:1. Structural Traps2.Stratigraphic Traps

Structural Traps

• Structural traps are mostly formed by folding or faulting of reservoir rocks.

• Structural traps are the most important type of trap as they represent the majority of the world's discovered petroleum resources.

• Some of the most common structural traps are:i. Anticlinal trapsii. Fault trapsiii. Salt dome traps

i. Anticlinal traps:-A trap whose closure is controlled by the presence of an anticline.

ii. Fault traps:-A fault trap, as name suggests, will be formed by the movement of rock along a fault line.

iii. Salt dome trap:-A salt dome trap will be formed when a thick bed of evaporite minerals (mainly salt, or halite) found at depth intrudes vertically into surrounding rock strata.

Types

Stratigraphic traps• A stratigraphic trap is caused either by a

nonporous formation sealing off the top edge of a reservoir bed or by a change of porosity and permeability within the reservoir bed itself.

OR• A stratigraphic trap accumulates oil due to

changes of rock character rather than faulting or folding of the rock.

Stratigraphic trapsi. Unconformity ii. Reefiii. Pinch-out

i. Unconformity trap:- A type of hydrocarbon trap whose closure is controlled by the presence of an unconformity.

ii. Pinch out A porous reservoir rock encased within an impermeable seal such as shale; and the rock will not leave its original formation.

Abnormal Pressures…!

Background:- In some reservoirs the pressure is not in

balanced condition means the pressure is not normal pore pressure i.e. 0.465 psi/ft.

This will affect the behavior of reservoir during production or drilling.

It is a very important consideration in many aspects of well planning and operations.

The pressure of the fluid in the pore space (the pore pressure).

Dependent on the density of the fluid & depth of the pressure measurement.

Abnormal Pressure

Which is greater or less than normal pressure.

Normal pore pressure gradient is 0.465 psi/ft.

The magnitude of the pressure in the pores of a formation, known as the formation pore pressure (or simply formation pressure).

• An under pressured (subnormal) system occurs when the formation pore pressure is less than the normal pressure, 0.465 psi/ft.

Origins1. Thermal Expansion2. Formation forshoreting3. Depletion

EffectOccurrence of kick

Subnormal Pressure

Over pressured Pressure

• An over pressured system occurs when the formation pore pressure is greater than the normal pressure, 0.465 psi/ft.

Origins1. Incomplete Compaction2. Faulting3. Salt dome zone

EffectLost circulation zone

Normal and Abnormal Pore Pressure

Abnormal Pressure Gradients

Normal Pressure Gradients West Texas: 0.433 psi/ft. Gulf Coast: 0.465 psi/ft.

Dep

th,

ft.

10,000’

Pore Pressure, psig

Pore Pressure Gradient

Fracture Gradient

Detection

• 1. Drilling Parameters i. ROP ii. WOB• 2. Drilling mud i. Pit level will increase• 3. Drilled Cuttings Change in composition

Exploration Techniques…!

Oil Exploration Methods

• There are three commonly employed methods for oil exploration

• 1) Geological • 2) Geophysical• 3) Geochemical

Geophysical Methods

Seismic Method• Introduction:• Seismic techniques are commonly used to determine site

geology,• stratigraphy, and rock quality. These techniques provide detailed• information about subsurface layering and rock geomechanical

properties• using seismic acoustical waves. Reflection and Refraction are the

most• commonly used seismic techniques. These methods determine

geological• structure and rock velocities by either refracting or reflecting

waves off• boundaries between rock units with different seismic velocities

• Seismic Refraction:• Seismic refraction investigates the subsurface by

generating arrival time and offset distance information to determine the path and velocity of the elastic disturbance in the ground.

• The disturbance is created by shot ,hammer , weight drop, or some other comparable method for putting impulsive energy into the ground.

• Detectors measure the first arrival of the energy and its time.

• The data are plotted in time – distance graphs from which the velocities of the different layers, and their depths can be calculated.

Seismic Reflection:

• Seismic Reflection follows the law of mirror images – angle of reflection from a surface is equal to the angle of incidence. Shots are fired, in turn, at each of the geophone positions and active geophones are progressively added ahead of the shots.

• At each subsurface boundary, across . the elastic and density parameters differ, a percentage of the energy in the wave is reflected back to the surface where it is recorded.

Gravity method:

• Measurements of the gravitational field at a series of different locations over an area of interest. The objective in exploration work is to associate variations with differences in the distribution of densities and hence rock type

• A gravimeter or gravitometer is an instrument used in gravimetry for measuring the local gravitational field of the Earth.

Magnetic Survey:

• An exploration method in which an instrument that measure the intensity of the natural magnetic forces existing in the earth’s subsurface is passed over the surface or through the water.

• The instrument can detect deviations in magnetic forces, and such deviations may indicate the existence of an underground hydrocarbon reservoir.

• MagnetometerAn instrument used to measure the intensity and direction of a magnetic field, especially that of the earth.

Any Question…

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