Reservoir Fluids Oil Gas Engineering Essay

Reservoir fluids oil, gas formation harmonizing to popular organic theory of crude oil formation: -when organic stuffs as died workss and animate beings sank to the underside of seas and lakes and lied down on the sea bed where they decomposed and assorted together with sand, salts and stones, ensuing in a built up of several beds of organic stuffs, these beds were buried deep in the Earth by deposits such as sand, rocks and clay accumulated on top, compacting the beds of organic stuffs under its weight, 1000000s of old ages subsequently, organic beds were buried deeper under heavier beds of deposits.

Increasing force per unit area and temperature due to increase deepness of burial with absence of O allowed the geological procedures change overing deposits into sedimentary stones and the organic stuffs into either oil or gas harmonizing to temperature applied, and the stone incorporating these organic stuffs called beginning stone.

migration Petroleum formed in beginning stones in deeper beds of the Earth began traveling upward into higher beds to make the reservoir stones ( primary migration ) and traveling from a reservoir to another or roll uping into a reservoir trap or leak through the Earth surface with permeable beds ( secondary migration )

Beginning stone pores are little which stops oil go forthing the stone so, the combined formation and compression cause high force per unit area doing micro breaks in the stone that expel crude oil out

Minerals in stones contain H2O and with increase burial deepness the temperature and force per unit area addition doing the H2O to be released from them, this gives beginning of flushing of crude oil outside the stone to another stone and due to take down denseness crude oil moves above H2O to higher stones

Reservoir stones planes are irregular taking to accretion of oil droplets in these abnormalities, but one time sufficient volume ( 20-30 % of pore infinite ) were reached, they float into and along the reservoir

1-petroleum reservoir: –

Is a site there was accretion of rough oil and be on this site over the old ages and bring forth oil from the decomposition of life beings depending on the force per unit area and temperature addition.

And Is divided into: –

A-oil reservoir: –

A site for reservoirs incorporating Hydrocarbons exist under the ocean or Earth inside the pores of the stones

B-gas reservoir: –

is a type of crude oil reservoir of non associated gas

2-the types of oil reservoir: –

1-Depletion thrust reservoir: -It ‘s called ( solution gas thrust reservoir ) .And it ‘s a reservoir that the displacment of oil from the topographic point have formation of it to bring forthing Wellss by utilizing enlargement of gas solution. Beginning of energy is a gas liberation by the oil in the reservoir that make force per unit area in it reduced.

The features of Depletion thrust reservoir: –

1-reservoir force per unit area is decrease rapidly because there is no gas cap or fiuid to take topographic point oil

2-the oil /gas production ratio is fristly low so up to maximum

3-there is no H2O that means there is no H2O producting with oil.

4- recavary factor 5 % -35 %

2- gas cap thrust reservoir: -It ‘s known by a gas cap covered it and it ‘s defined as the reservoir wherein the supplanting of oil from the formation to the bring forthing Wellss by enlargement of the original free gas cap.It ‘s worked by the enlargement of gas as it is liberated that compressed the oil to the bring forthing Wellss to get down bring forthing.The energy that make bring forthing start come from: –

1-Expansion of the gas-cap.

2-Expansion of the solution gas as it is liberated.

The charastarictics of gas cap thrust reservoir: –

1-reservoir force per unit area is decrease rapidly

2-the oil/gas production ratio is start addition continuosily

3-there is no H2O production

4-Recavary factor 20 % -40 %

3- H2O thrust reservoir: -It ‘s bounded by aquifer and aquifer is abearing stone which hydraulicly connected to the reservoir, and it ‘s defined as reservoir wherein the supplanting of oil from the formation to the bring forthing Wellss by H2O inflow from aquifer into the reservoir. The reservoir know by happening surface H2O and sum of H2O find the type of H2O reservoir and there is two type

bottom H2O reservoir: -that occur when the H2O is under the oil wholly

b-edge H2O reservoir: – that occur when the H2O in the border of

reservoir under the reservoir

The charastarictics of H2O thrust reservoir: –

1-reservoir force per unit area is high

2-the ratio of oil during production is low if the force per unit area is high

3-in the production there is H2O bring forthing

4 — Recavary factor 35 % -80 %

4-COMBINATION DRIVE reservoir: -Is a reservoir that the oil is swept in the way of the boring hole. And oil is Besieged between free gas ( up ) and H2O ( down ) , the manner to bring forthing oil in this status is any manner of injection ( gas H2O, steam )

The charastarictics of combination thrust reservoir: –

1-the reservoir force per unit area is cut down rapidly

2-the ratio of oil during production is low

3 – recovery factor is bigger than solution gas reservoir

Traps: –

Is a alteration in construction of reservoir stone that formed to pin down the oil /gas

And it ‘s divided into: –

1-Stratigraphic Traps: –

are traps that are formed by alterations in the features of the stone such

permeableness or porousness of stone reservoir to pin down oil/gas

2-Structural Traps: –

Are a traps that formed by banding or interrupting the sedimentary stone, the type of Structural Traps is the anticline that formed when the stones buckled upward

Oil exists within certain stones particularly sedimentary stones and can be covered utilizing a batch of techniques. These techniques are divided into four chief classs primary, secondary, third and infill methods.

Primary methods: these methods depend on reservoir natural forces. Reservoir has a truth of energy beginnings by which oil comes out of the bring forthing Wellss. These beginnings are the enlargement of solution, gas cap enlargement, inflow of H2O into the reservoir and gravitative force. The enlargement of solution is a thrust mechanism wherein the enlargement of solution displaces oil towards the bring forthing Wellss. Gas cap enlargement this manner depends on the enlargement of the gas cap exists above the oil zone which cause high force per unit area make the oil leave the formation. Water thrust is another thrust mechanism works by the inflow of H2O into the reservoir to take topographic point the produced oil. Water enters the reservoir maintain the reservoir force per unit area high, therefore oil production continues. Gravitational force is a mechanism to drive oil to the surface depends on the difference in oil, gas and H2O denseness due to their original segregation, therefore applied scientists can divide oil, gas and H2O.

Secondary methods: are techniques used when natural forces fail in bring forthing oil. There are a batch of techniques but the most common types are H2O injection and gas injection. Water is injected to the reservoir to maintain the force per unit area inside the reservoir high and travel hydrocarbons toward the production Wellss. Gas deluging like H2O injection, but here gas is pumped to maintain the reservoir force per unit area high.

Third recovery: is used to increase the recovery factor since primary and secondary methods cover 35 % of the entire oil. Tertiary methods are divided into three chief methods, chemical, thermic and mixable gas methods. Chemical methods in which chemical are added to H2O so in injected to the reservoir.these chemicals have many maps like cut downing oil mobility and it ‘s permeableness, increase oil comparative permeableness. Miscible gas is injected to the reservoir to lift the reservoir force per unit area by the enlargement of gases like CO2 and N2.

Infill recovery: is the last thrust mechanism comes by the terminal of the reservoir life. This procedure involves increasing the Wellss Numberss to heighten the production degree. Although infill boring cost a batch of money, the extra hydrocarbons could be non immense.

The belongingss of crude oil fluids

Reservoir fluids known are five types black oil, volatile oil, prohibitionist gas, moisture gas and retrograde gas.

Differences between five types:

1-Black oil: consist of different chemicals called hydrocarbons with big heavy molecules.

2-Volatile oil: contain fewer heavy molecules than black oil.

3-Dry gas: hydrocarbon exist as a gas both in the reservoir and in the centrifuge.

4-Wet gas: hydrocarbon exist as a gas in the reservoir and exist as a gas and condensate in the centrifuge.

5-Retrograde gas: hydrocarbon exist as a gas and condensate both in the reservoir and in the centrifuge.

Properties of black oil:

Black oil has many physical belongingss which include the followers:

-Specific gravitation: the ratio of the denseness of the liquid to the denseness of H2O.

-Formation volume factor of oil: due to the decreasing in force per unit area the reservoir to the surface, there is a alteration ( diminishing ) in oil volume at the surface and the reservoir.this alteration is called Formation volume factor of oil.

– Solution gas oil ratio: the measure of gas dissolved in oil at reservoir status.

-Bubble point force per unit area: particular instance of impregnation at which the first release of gas occurs.

-The coefficient isothermal squeezability of oil: at force per unit area above the bubble point the coefficient isothermal squeezability of oil is the same as gas but at force per unit area below we should cipher the volume of gas which evolves.

-Coefficient of viscousness of oil: is a step of the opposition to flux exerted by a fluid.

-Initial reservoir force per unit area: the force per unit area in a black oil in the reservoir which may be either higher than bubble point force per unit area or equal.

-Pressure tendencies: after taking liquid from reservoir, it ‘s force per unit area lessening. at a force per unit area above the bubble point, fluids and reservoir stone force per unit area below the bubble point gas signifiers in pore infinite in the stone.

-Gas production tendencies: during the trip of oil from reservoir the surface and so to the stock tank the dissolved gas will come out of solution which appears as a centrifuge gas.

Properties of volatile oil: –

Volatile oil has all belongingss of black oil except formation volume factor and solution gas oil ratio which are non usually measured for volatile oil.

Properties of dry gas and moisture gas:

-gas formation volume factor: volume of gas at reservoir status required to bring forth one criterion three-dimensional pes of gas at surface.

– The coefficient isothermal squeezability of gas and Coefficient of viscousness of gas: discussed in black oil

-Heating value: the measure of heat produced when the gas is wholly burned to H2O and C dioxide.

Retrograde gas: has the belongingss of moisture gas at a force per unit area above the dew point force per unit area.

Duties of reservoir applied scientist:

-the appraisal of hydrocarbon in topographic point ( reservoir )

-determining the recovery factor.

-development planning.

-production operation optimisation.

-determining the fraction of ascertained hydrocarbon.

-contributing with the geologists and petro physicists to the appraisal of hydrocarbon.


Reserve categorization: *

Petroleum categorization have improved markedly the last 10 old ages the societies of crude oil such as society of crude oil applied scientists ( SPE ) , universe power raising Congress ( WPC ) and American association of crude oil geologist ( AAPG ) , accepted the progressed and industry range for qualifying.

Most of militias estimations are non 100 % accurate, depending on technology informations and understanding those informations good.

Categorization can be expressed by insulating militias into two chief types “ proven ” and “ non-proven ” the society of crude oil applied scientists and universe crude oil consul proved that probabilistic techniques 1p ( proved ) , 2p ( proved + likely ) and 3p ( proved+probable+possible ) volumes p90, p50, p10.

1 ) Proven militias:

There are many ways to gauge militias such as deterministic giving one value and probabilistic P90, P50, P10

In the United States accepted this type of study and the other states of the universe like Russia use different types of studies more proven likely modesty ( P50 ) .

Deterministic: defined as those recoverable with “ sensible certainty ” and high grade of assurance.

Probabilistic: 90 % of recoverability it means 90 per centum produced

Proven militias spliting into two footings

1 ) Proven developed ( PD )

2 ) non-proved developed ( PND )

2 ) Non-proven militias:

The non-proven militias besides based on technology informations like proved militias and they are non easy to roll up.

They are sub-classified as likely and possible

Probable militias knows as accretions and claimed 50 % assurance degree of recovery

International societies refer to them in the industry as 2P that ‘s average proved plus likely

Possible militias has a less recoverable factor it has 10 % certainty of being produced P10.