Fundamentals of Petroleum Engineering Lecture 1

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Questions and Answers

What is the main characteristic of primary stratigraphic traps?

Combination of structural and stratigraphic traps

Discontinuous deposition of sediment (correct)

Tectonic processes and changes in lithology

Changes in porosity of the rock after sedimentation

What is the name of the trap that results from a combination of tectonic processes and changes in lithology?

Salt dome

Unconformity trap

Combination Trap (correct)

Lenses trap

What is the primary purpose of understanding driving mechanisms in oil recovery?

To calculate the total oil in place

To identify the type of rock grains

To control the behavior of fluids within reservoirs (correct)

To determine the type of trap formation

What happens to the reservoir pressure in an under saturated oil reservoir?

It decreases Signup and view all the answers

What are the two factors that contribute to reservoir rock compressibility?

Expansion of individual rock grains and formation compaction Signup and view all the answers

What is the typical recovery percentage for rock and liquid expansion drive mechanism?

3-5% Signup and view all the answers

What is another name for the depletion drive mechanism?

Solution gas drive Signup and view all the answers

How many driving mechanisms are necessary for oil recovery?

6 Signup and view all the answers

What is the primary component of sandstone reservoir rocks?

Quartz and feldspar Signup and view all the answers

What is the purpose of the cap rock in an oil and gas trap?

To prevent hydrocarbons from rising to the surface Signup and view all the answers

What is the term for the general physical characteristics of a rock?

Lithology Signup and view all the answers

Which type of trap is formed during the sedimentation process?

Stratigraphic trap Signup and view all the answers

What is the effect of swelling clays on reservoir quality?

Negative impact Signup and view all the answers

What is an example of a structural trap?

All of the above Signup and view all the answers

What is the term for the arrangement of rock layers that contains an accumulation of hydrocarbons?

Oil and gas trap Signup and view all the answers

What is the term for the pore space in carbonate reservoir rocks?

All of the above Signup and view all the answers

What is the primary source of energy in an internal gas drive reservoir?

Liberation of solution gas from the crude oil Signup and view all the answers

What is a characteristic of a gas-cap-drive reservoir?

Slow decline in reservoir pressure Signup and view all the answers

What is the primary driving force in a water-drive mechanism?

Influx of water from the aquifer Signup and view all the answers

What occurs when the reservoir pressure falls below the bubble-point pressure?

Gas bubbles are liberated within the microscopic pore spaces Signup and view all the answers

What is a result of the differences in densities of the reservoir fluids in a gravity-drainage-drive mechanism?

The gas-oil and oil-water contacts are essentially horizontal Signup and view all the answers

What is the combination-drive mechanism?

A combination of both water and free gas drive Signup and view all the answers

What is the purpose of the example of placing crude oil and water in a jar and agitating the contents?

To illustrate the effect of gravity on the reservoir fluids Signup and view all the answers

What is the assumption about the reservoir fluids in a gravity-drainage-drive mechanism?

The reservoir fluids are in equilibrium Signup and view all the answers

Study Notes

Production System

An oil and gas field involves oil and gas reservoirs (G & O Accumulation)

Lithology of Petroleum Reservoirs

Lithology refers to the general physical characteristics of a rock
Reservoir rocks can be divided into two types: sandstone and carbonates
- Sandstone: usually composed of silica grains (mainly quartz) and some feldspar, can be consolidated or loosely consolidated, may contain swelling clays
- Carbonates: two major types are limestone (CaCO3) and dolomite (CaMg(CO3)2), pore space consists of inter- or intragranular porosity as well as areas of dissolution (vugs) and fractures

Petroleum Traps

An oil and gas trap is an arrangement of rock layers that contains an accumulation of hydrocarbons, covered by a cap rock to prevent them from rising to the surface
Traps can be classified into three types: structural, stratigraphic, and combination traps
Structural traps result from a local deformation of the reservoir formation, such as folding and/or faulting of the rock layers
The most common types of structural traps are:
- Anticline traps: formed by folding of rock
- Fault traps: formed when reservoir rock is split along a fault line
Stratigraphic traps are formed during the sedimentation process, and can be primary or secondary
Combination traps result from a combination of tectonic processes and changes in lithology

Primary Recovery Mechanisms

There are six driving mechanisms that provide the natural energy necessary for oil recovery:
- Rock and liquid expansion drive
- Depletion drive
- Gas cap drive
- Water drive
- Gravity drainage drive
- Combination drive

Rock and Liquid Expansion Drive

Occurs when an oil reservoir initially exists at a pressure higher than its bubble-point pressure
As the reservoir pressure declines, the rock and fluids expand due to their individual compressibilities
This type of reservoir is considered the least efficient driving force and usually results in the recovery of only a small percentage of the total oil in place (3-5%)

Depletion Drive Mechanism

Also referred to as solution gas drive, dissolved gas drive, or internal gas drive
The principal source of energy is the gas liberation from the crude oil and the subsequent expansion of the solution gas as the reservoir pressure is reduced

Gas Cap Drive

Gas-cap-drive reservoirs can be identified by the presence of a gas cap with little or no water drive
The natural energy available to produce the crude oil comes from the expansion of the gas cap and the solution gas as it is liberated

Water Drive Mechanism

Common types are edge water or bottom water in the water influx into a reservoir
Bottom water occurs directly beneath the oil and edge water occurs off the flanks of the structure at the edge of the oil

Gravity-Drainage-Drive Mechanism

Occurs due to differences in densities of the reservoir fluids
Gravitational forces can be illustrated by placing a quantity of crude oil and a quantity of water in a jar and agitating the contents

Combination-Drive Mechanism

A combination of driving forces resulting from the presence of a gas-cap and an aquifer
Two combinations of driving forces resulting from the presence of a gas-cap and an aquifer

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Description

This quiz covers the basics of petroleum engineering, including the definition of oil and gas fields, lithology of petroleum reservoirs, and characteristics of sandstone and carbonate reservoir rocks.