Reservoir drive mechanism
Is a source of energy for driving the fluids out through the wellbore
Primary recovery
Primary recovery refers to the production of oil and gas from a reservoir without the use of any process such as fluid injection to supplement the natural energy of the reservoir
Primary recovery mechanism
There are six driving mechanisms for oil recovery
Rock and fluid expansion drive mechanism
Can be defined as the mechanism wherein the displacement of oil from the formation to the
production wells are accomplished by rock and fluid expansion
Characteristics of rock and fluid expansion drive mechanism
A very rapid decline in pressure
Constant gas oil ratio that is equal to the gas solubility at the bubble point pressure
Nil water production
Ultimate recovery factor is less than 5%
The Depletion Drive Mechanism
Can be defined as the mechanism wherein the displacement of oil from the formation to the
production wells are accomplished by expansion of solution gas
Characteristics of Depletion Drive Mechanism
A rapid decline in pressure
because there is no extraneous fluid or gas caps are available to provide a replacement of the gas and oil withdrawals
Increasing GOR
Water- free oil production
%Ultimate recovery factor may be average from 15 to 25
Well behavior requires pumping at an early stage
Gas-Cap drive mechanism
can be defined as the mechanism wherein the displacement of oil from the formation to the
production wells are accomplished by expansion of the original free gas cap
and can be defined as the presence of agas cap with little or no water drive
Characteristics of Gas-Cap drive mechanism
A slow decline in pressure
due to pressure tends to be maintained at a higher level in a depletion drive reservoir
Increasing GOR
Nil water production
Well behavior long life well
Water-drive mechanism
can be defined as the mechanism wherein the displacement of oil from the formation to the
production wells are accomplished by water influx from the aquifer into the reservoir
Characteristics of water drive mechanism
a very gradual decline in the pressure
due to the oil and gas withdrawals from the reservoir are replaced almost volume for volume by water encroaching into the oil zone
More or less constant GOR
Early increasing water production
Ultimate recovery factor ranges from 35% to 75% of the original oil in place
The Gravity drainage drive mechanism
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Can be defined as the mechanism wherein the displacement of oil from the formation to the producing wells is accomplished as a result of differences in densities of the reservoir fluids
Characteristics of The Gravity drainage drive mechanism
Variable rates of pressure decline depending principally upon the amount of gas conservation
Low gas-oil ratio
due to a migration of the evolved gas up structure due to gravitational segregation of the fluids
Formation of a secondary gas cap in reservoirs those initially was undersaturated
Little or no water production
ultimate recovery factor up to 80% of the original oil in place
The Combination driving mechanism
can be defined as the mechanism by which both water and free gas are available in some degree to displace the oil toward the producing wells
Characteristics of The Combination driving mechanism
Relatively rapid pressure decline
Ultimate recovery from combination drive reservoirs is usually greater than recovery from depletion drive reservoir but less than recovery from water drive reservoir
Gas-Cap drive mechanism
Gravity drainage drive mechanism