Oil and Gas:

Upstream

Rohit Bisht

(MBA Oil and Gas Management Graduate)

ChemistryCrude oil, commonly known as petroleum,is a liquid found within the Earth comprisedof hydrocarbons, organic compounds andsmall amounts of metal. Whilehydrocarbons are usually the primarycomponent of crude oil, their compositioncan vary from 50%-97% depending on thetype of crude oil and how it is extracted.Organic compounds like nitrogen, oxygen,and sulfur typically make-up between 6%-10% of crude oil while metals such ascopper, nickel, vanadium and iron accountfor less than 1% of the total composition.

Crude Oil

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Basic Geology

Types of Rockso Igneous Rocks

o Sedimentary Rocks

o Metamorphic Rocks

Geologic Time Scale

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Oil FormationConditions for Oil and Gas Formation

There are four requirements necessary to form an oil deposit: o There must be a source rock

o There must be a heating event

o There must be a reservoir rock

o There must be a trapping mechanism

Oil Maturity

Organic matter is first changed by the

increase in temperature into kerogen,

which is a solid form of hydrocarbon

Around 90°C, it is changed into a liquid

state, called Oil.

Around 150°C, Oil generation dies oil and

only Methane and Hydrogen are produced.Rohit Bisht

Migration of PetroleumThe movement of hydrocarbons from their source into reservoir rocks.The movement of newly generated hydrocarbons out of their sourcerock is primary migration also called expulsion. The furthermovement of the hydrocarbons into reservoir rock in a hydrocarbontrap or other area of accumulation is secondary migration

Migration typically occurs from a structurally low area to a higher areabecause of the relative buoyancy of hydrocarbons in comparison to thesurrounding rock.

Being lighter than water, petroleum will displace groundwater and flowupwards and will seep to the surface via faults and porous overburdenunless confined under special circumstances to became trapped and toform economic petroleum deposits.

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ReservoirA petroleum reservoir is a subsurface pool of hydrocarbons containedin porous or fractured rock formations.

A suitable reservoir rock must be porous, permeable and containenough hydrocarbon to make it economically feasible fro the operatingcompany to drill for and produce them.

Porosity: Porosity of rock is a measure of its ability to hold a fluid.

Porosity = Pore volume/total rock volume x 100%

Permeability: Permeability is a measure of the amount of flow of a liquid through a rock.

Q = KAD/uL

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Geological structures for petroleum entrapment

TRAP: A trap consists of an impervious stratum that overlies the reservoir rock thereby prohibiting hydrocarbons from escaping upward and laterally. This impervious stratum is called a roof rock; it intervenes to collect and hold hydrocarbons underground. The roof forms a seal, or a barrier, which creates the needed conditions for a pool.

Classification of Traps:

o Structural Traps

• Anticline Trap

• Fault Trap

o Stratigraphic Traps

• Pinchout

• Truncated

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Exploration MethodsPreliminary Studies

Surveying marks the elementary phase for oil and gas exploration. Inthe first stage of the search for hydrocarbon-bearing rock formations,geological maps and satellite data are reviewed to identify majorsedimentary basins. Remote sensing and aerial photography may thenbe used to identify promising landscape formations such as faults, oranticlines.

Geological Methods:o Oil Seeps

The second important point in geological method for surface exploratory methods includes:o Preparation of geologic maps of the area

o Preparation of cross section geological formations

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Geophysical Methods :Seismic MethodsIt is a method of exploration geophysics that uses the principles of seismology toestimate the properties of the Earth's subsurface from reflected seismic waves. Themethod requires a seismic acoustic energy as a source, such as explosives (dynamite)and vibrators for land surveys or air guns for marine surveys. The reflected signals areoutput onto a storage medium, which is usually a magnetic tape. Once the data isrecorded on the tape, it can then be processed using specialist software which willresult in processed seismic profiles being produced.

On land, the typical seismometer used in a reflection experiment is a small, portableinstrument known as a geophone, which converts ground motion into an analogelectrical signal. In water, hydrophones, which convert pressure changes into electricalsignals, are used.

Seismic field acquisition involves three basic elements:

I. a source of acoustic energy

II. seismic receivers - geophones / hydrophones

III. a seismograph or recorder to collect and store the data

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2D - When exploring a new area where little is known of the subsurface geology, a 2D

survey is usually performed. It gives an idea about the lithology of the field and the

presence of any geological formations where petroleum can be trapped.

3D - In areas where the larger and more obvious traps are mapped, petroleum explorers

are increasingly using 3D surveys to obtain greater definition. By placing survey lines

much closer together, a more detailed three-dimensional picture can be built.

4D - 3D survey that is carried out at regular intervals to plan the development of the

field. Hence the fourth dimension becomes time.

Gravity methods

Gravity surveys involve taking reading about a kilometer apart throughout the region

with a device called gravimeter. The gravimeter measures the gravitational field and

this reading correlates with the density of the region. By studying the differences in the

density, one can predict which areas of the region might contain oil.

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Magnetic methods

By measuring the magnetic field, one can tell where there islikely to be oil because the rocks that may contain oil have verylow magnetic readings. The magnetic field can be measured withan instrument called magnetometer which can be flown over anarea or used on the ground. Magnetic surveys are usually madewith magnetometers borne by aircraft flying in parallel linesspaced two to four kilometers apart at an elevation of about 500meters when exploring for petroleum deposits. Ground surveysare conducted to follow up magnetic anomaly discoveries madefrom the air. Such surveys may involve stations spaced only 50meters apart

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Well DrillingPreparation to Drill

Setting the Rig

Drilling

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Preparing to drill

Once the land has been prepared, several holes must be dug to

make way for the rig and the main hole. A rectangular pit, called

a cellar, is dug around the location of the actual drilling hole. The

cellar provides a work space around the hole, for the workers and

drilling accessories. The crew then begins drilling the main hole,

often with a small drill truck rather than the main rig. The first

part of the hole is larger and shallower than the main portion, and

is lined with a large-diameter conductor pipe. Additional holes

are dug off to the side to temporarily store equipment -- when

these holes are finished, the rig equipment can be brought in and

set up.

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Setting the Rig

Depending upon the remoteness of the drill site and its access,

equipment may be transported to the site by truck, helicopter or

barge. Some rigs are built on ships or barges for work on inland

water where there is no foundation to support a rig (as in marshes

or lakes).

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DrillingThere are five basic steps to drilling the surface hole:

i. Place the drill bit, collar and drill pipe in the hole.

ii. Attach the kelly and turntable and begin drilling.

iii. As drilling progresses, circulate mud through the pipe and

out of the bit to float the rock cuttings out of the hole.

iv. Add new sections (joints) of drill pipes as the hole gets

deeper.

v. Remove (trip out) the drill pipe, collar and bit when the pre-

set depth (anywhere from a few hundred to a couple-

thousand feet) is reached.

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Once the final depth is reached, the well to allows il to flow into

the casing in a controlled manner. First, they perforating gun is

lowered a into the well to the production depth. The gun has

explosive charges to create holes in the casing through which oil

can flow. After the casing has been perforated, small-diameter

pipe (tubing) is put into the hole as a conduit for oil and gas to

flow up the well. A device called a packer is run down the outside

of the tubing. When the packer is set at the production level, it is

expanded to form a seal around the outside of the tubing. Finally,

they connect a multi-valved structure called a Christmas tree to

the top of the tubing and cement it to the op of the casing. The

Christmas tree allows them to control the flow of oil from the

well.

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EORPrimary Oil Recovery Secondary Oil Recovery Enhanced Oil Recovery

Primary oil recovery refers

to the process of extracting

oil either via the natural

rise of hydrocarbons to the

surface of the earth or via

pump jacks and other

artificial lift devices.

This method involves the

injection of gas or water,

which will displace the oil,

force it to move from its

resting place and bring it to

the surface

Rather than simply trying

to force the oil out of the

ground, as did the previous

two methods, enhanced oil

recovery seeks to alter its

properties to make it more

conducive to extraction.

There are three main types

of enhanced oil recovery:

• Thermal Recovery

• Gas Injection

• Chemical Injection

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Thermal Recovery. This is the most prevalent type of EOR in the USAand works by heating the oil to reduce its viscosity and allowing easierflow to the surface. This is most commonly achieved by introducingsteam into the reservoir, which will work to heat the oil. Lesscommonplace is the practice of burning part of the oil in order to heatthe rest (fire flooding or in-situ burning).

Gas Injection. Either natural gas, nitrogen or carbon dioxide(increasingly the most popular option) are injected into the reservoir tomix with the oil, making it more viscous, whilst simultaneouslypushing the oil to the surface (similar to secondary oil recovery).

Chemical Injection. The least common method of EOR, chemicalinjection works by freeing trapped oil in the well. This is done bylowering surface tension and increasing the efficiency of water-flooding.

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