• Monday, April 13, 2015

    Reservoir drive mechanism

    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


     Gravity drainage drive mechanism


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