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The natural energy of a reservoir can be used to move oil and gas toward the wellbore. Used in such a fashion, these sources of energy are called ''drive mechanisms''. Early determination and characterization of the drive mechanism(s) present within a reservoir may allow a greater ultimate recovery of hydrocarbons. Drive mechanisms are determined by the analysis of historical production data, primarily reservoir pressure data and fluid production ratios.

The natural energy of a reservoir can be used to move oil and gas toward the wellbore. Used in such a fashion, these sources of energy are called ''drive mechanisms''. Early determination and characterization of the drive mechanism(s) present within a reservoir may allow a greater ultimate recovery of hydrocarbons. Drive mechanisms are determined by the analysis of historical production data, primarily reservoir pressure data and fluid production ratios.

The three primary oil reservoir drive mechanisms are ''solution gas drive, gas cap drive'', and ''water drive''<ref name = pt10r5>Clark, N. J., 1969, Elements of petroleum reservoirs: Dallas, TX, Society of Petroleum Engineers, AIME, p. 66–84.</ref>. Reservoir pressure trends and producing gas-oil ratio trends of these three drive mechanisms are shown in Figures 1 and 2, respectively. A ''combination'' or ''mixed drive'' occurs when two or more of the primary drive mechanisms are present in the same reservoir. A combination drive may also occur when one or more of the primary drive mechanisms are assisted by ''gravity drainage''. Table 1 shows the energy sources and ultimate recovery ranges of the major drive mechanisms.

The three primary oil reservoir drive mechanisms are [Drive mechanisms and recovery#solution gas drive|solution gas drive], gas cap drive'', and ''water drive''<ref name = pt10r5>Clark, N. J., 1969, Elements of petroleum reservoirs: Dallas, TX, Society of Petroleum Engineers, AIME, p. 66–84.</ref>. Reservoir pressure trends and producing gas-oil ratio trends of these three drive mechanisms are shown in Figures 1 and 2, respectively. A ''combination'' or ''mixed drive'' occurs when two or more of the primary drive mechanisms are present in the same reservoir. A combination drive may also occur when one or more of the primary drive mechanisms are assisted by ''gravity drainage''. Table 1 shows the energy sources and ultimate recovery ranges of the major drive mechanisms.

[[file:drive-mechanisms-and-recovery_fig1.png|thumb|{{figure_number|1}}Reservoir pressure trends by drive mechanism.]]

[[file:drive-mechanisms-and-recovery_fig1.png|thumb|{{figure_number|1}}Reservoir pressure trends by drive mechanism.]]