Reservoir drive mechanism


Is asource of energy for driving the fluids out through the wellbore


Primary recovery


Primary recovery refer to the production of oil and gas from areservoir without 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


Reservoir drive mechanism


Rock and fluid expansion drive mechanism



Reservoir drive mechanism


Can be difined as the mechanism wherein the displacement of oil from the formation to the
production wells is accomplished by rock and fluid expansion


Characteristics of rock and fluid expansion drive mechanism


Very rapid decline in pressure


Constant gas oil ratio that is equal the gas solubility at the bubble point pressure


Nil water production


Ultimate recovery factor is less than 5%


The Depletion Drive Mechanism





Reservoir drive mechanism




Can be difind as the mechanism wherein the displacement of oil from the formation to the
production wells is accomplished by expansion of solution gas


Characteristics of Depletion Drive Mechanism


Rapid decline in pressure


becouse there is no extraneous fluid or gas caps are available to provide areplacement of the gas and oil withdrawals




Increasing GOR


Water- free oil production


%Ultimate recovery factor my be average from 15 to 25


Well behavior requires pumping at early stage




Gas-Cap drive mechanism





Reservoir drive mechanism


can be difind as the mechanism wherein the displacement of oil from the formation to the
production wells is accomplished by expansion of original free gas cap




and can be difined as the presence of agas cap with little or no water drive


Characteristics of Gas-Cap drive mechanism


Reservoir drive mechanism


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


Reservoir drive mechanism


can be difind as the mechanism wherein the displacement of oil from the formation to the
production wells is accomplished by water influx from aquifer into the reservoir




Characteristics of water drive mechanism


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

 




Reservoir drive mechanism


Can be difinea as the mechanism wherein the displacement of oil from the formation to the producting wells is accomplished as aresult of differences in densities of the reservoir fluids


Characteristics of The Gravity drainage drive mechanism




Varible rates of pressure decline depending principally upon the amount of gas conservation




Low gas-oil ratio
due to migration of the evolved gas upstructure due to gravitational segregation of the fluids






Formation of secondary gas cap in reservoirs those initially were undersaturated


Little or no water production


ultimate recovery factor up to 80% of the original oil in place


The Combination driving mechanism


Reservoir drive mechanism


can be difinea as the mechanism in 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


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