Petroleum introduction

Petroleum Introduction

Kuwait Oil Company

Kuwait, 24/11/2011

HYDROCARBONS

Setting

• Oil and natural gas (hydrocarbons) produced from oil and gas fields are in porous and permeable rock or reservoirs, in which liquids have collected over geologic time

• Coincidence of four types of geologic features:

• Hydrocarbons source rocks

• Reservoir rocks

• Seals, and

• Traps

Setting

• Oil and natural gas (hydrocarbons) produced from oil and gas fields are in porous and permeable rock or reservoirs, in which liquids have collected over geologic time

• Coincidence of four types of geologic features:

• Hydrocarbons source rocks

• Reservoir rocks

• Seals, and

• Traps

Source

• Sedimentary rocks that were deposited usually in still swamps on land, shallow quiet marine bays or in deep submarine

• Comprised of very small mineral fragments

• In between them were organic remains like algae, wood or soft parts of plants

• Buried by the deposition of later, overlying sediments

• Increased heat and pressure with depth turned them into rock

• If further burial temperature > 120oC (250oF) then organic remains begin to “cook” into hydrocarbon over time

Source

• Sedimentary rocks that were deposited usually in still swamps on land, shallow quiet marine bays or in deep submarine

• Comprised of very small mineral fragments

• In between them were organic remains like algae, wood or soft parts of plants

• Buried by the deposition of later, overlying sediments

• Increased heat and pressure with depth turned them into rock

• If further burial temperature > 120oC (250oF) then organic remains begin to “cook” into hydrocarbon over time

Reservoir

• Must be porous and permeable to contain anything

• Contain interconnected passageways of microscopic pores or holes in between the mineral grains of the rocks

• Hydrostatic pressure will naturally expel hydrocarbons from source rocks

• They will migrate to adjacent reservoir rocks

• Mostly sandstone, limestone or dolomite

Reservoir

• Must be porous and permeable to contain anything

• Contain interconnected passageways of microscopic pores or holes in between the mineral grains of the rocks

• Hydrostatic pressure will naturally expel hydrocarbons from source rocks

• They will migrate to adjacent reservoir rocks

• Mostly sandstone, limestone or dolomite

• Hydrocarbons are relatively free to move once they are in the reservoir rock

• Those are originally filled with saline water ~ 1.03 g/cm3

• Oil (0.82 - 0.93 g/cm3) and gas (0.12 g/cm3) will rise up through pore space until they meet an impermeable barrier

• Seals are generally fine-grained rock with no over very small pore space that prevents fluids from entering

• Oil and natural gas then accumulate in the reservoir against those seals into what is called a trap

• Hydrocarbons are relatively free to move once they are in the reservoir rock

• Those are originally filled with saline water ~ 1.03 g/cm3

• Oil (0.82 - 0.93 g/cm3) and gas (0.12 g/cm3) will rise up through pore space until they meet an impermeable barrier

• Seals are generally fine-grained rock with no over very small pore space that prevents fluids from entering

• Oil and natural gas then accumulate in the reservoir against those seals into what is called a trap

Traps, structural

• Formed when reservoir rock and overlying seal have been deformed by folding or faulting

• Usually millions or 100s of millions of years after the deposition of the sediments turned into seals or reservoir rock

• Hydrocarbons migrate upward in pore spaces, through buoyancy, to the highest part of the structure

• Likewise hydrocarbons layer above water, and gas layers above oil

Traps, structural

• Formed when reservoir rock and overlying seal have been deformed by folding or faulting

• Usually millions or 100s of millions of years after the deposition of the sediments turned into seals or reservoir rock

• Hydrocarbons migrate upward in pore spaces, through buoyancy, to the highest part of the structure

• Likewise hydrocarbons layer above water, and gas layers above oil

Traps, stratigraphic

• Formed when reservoir rocks are deposited in a discontinuous layer - abut against or turn into a seal sideways - in other words seals are deposited beside or on top of reservoirs

• Common example is a coastal barrier island, which is an elongate lens of sandstone sandwiched in between shale, which in turn could be source rocks too

• It also helps if it gets all tilted up sideways by further uplift, not strong enough to deform rocks, but helps abut the hydrocarbons against the seal through natural buoyancy

Traps, stratigraphic

• Formed when reservoir rocks are deposited in a discontinuous layer - abut against or turn into a seal sideways - in other words seals are deposited beside or on top of reservoirs

• Common example is a coastal barrier island, which is an elongate lens of sandstone sandwiched in between shale, which in turn could be source rocks too

• It also helps if it gets all tilted up sideways by further uplift, not strong enough to deform rocks, but helps abut the hydrocarbons against the seal through natural buoyancy

GEOLOGY

Exploration - basin delineation

Exploration – surface mapping

Logging - surface

Sub-surface

GEOPHYSICS

Methods

• Hydrocarbons are usually buried deep underground

• They form a discontinuity in the rock formation

• Though porosity that is filled or empty of hydrocarbons

• Through changes from reservoir rocks to seal rocks

• Therefore ideally suited for geophysical prospecting

• The indirect measurement of rock properties underground

Methods

• Hydrocarbons are usually buried deep underground

• They form a discontinuity in the rock formation

• Though porosity that is filled or empty of hydrocarbons

• Through changes from reservoir rocks to seal rocks

• Therefore ideally suited for geophysical prospecting

• The indirect measurement of rock properties underground

Gravity

• Measure the spatial variation in the earth’s gravity filed caused by the differences in density of the underlying rocks

• The measure of changes in gravitational acceleration is expressed in gravity anomalies in milligals (10-5 m/s2)

• As a deviation from a reference value along a geoid (surface along which gravitational accelerations is the same)

• Gravity is measured as variations is value between different points on the earth’s surface

• It is a scalar value (intensity measured at each point)

Gravity

• Measure the spatial variation in the earth’s gravity filed caused by the differences in density of the underlying rocks

• The measure of changes in gravitational acceleration is expressed in gravity anomalies in milligals (10-5 m/s2)

• As a deviation from a reference value along a geoid (surface along which gravitational accelerations is the same)

• Gravity is measured as variations is value between different points on the earth’s surface

• It is a scalar value (intensity measured at each point)

Gravity Map

Magnetics

• Same thing as gravity, except the anomalies measured are magnetic in Tesla (V m/s2 , or very faint in nano Tesla = 10-9)

• Also magnetic susceptibility or remanance is a vector (meaning it has a direction as well as a scalar value)

• It is left behind by magnetic elements in rocks and minerals that vary with the type of rocks in the subsurface

• Anomaly = regional (background) – residual (local) fields

Magnetics

Magnetic map

Electromagnetics

• Same as magnetic except that:

• instead of measuring the magnetism in the ground, measure:

• the change resulting from inducing a current in the ground

• Also that is a 2-dimensional vector

• Anomaly = primary field (natural) – secondary field (induced) modified by what lies underground

• It is used for example in passive sea-bed logging

• Similarities in seismic and well logging to follow

Electromagnetics

Seismic

• Echo- or depth-sounding off rocks in the subsurface:

• from a pulse caused artificially on the earth’s surface

• the reflection of waves against variations in rock types

• and recording of travel + arrival times of various waves

Seismic

ENGINEERING

Platform

Kelly bushing

Rig floor

Rig sub-floor

Logging

Coring

MAPPING

PRODUCTION

GIS WRAP-UP

QUESTION TIME

Petroleum introduction

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