Gas Reserve Estimation of Offshore Producible Shut-in Leases in the Gulf of Mexico A Report (1976) / Chapter Skim
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APPENDIX C: GAS RESERVOIRS AND GAS RECOVERY
APPENDIX C: GAS RESERVOIRS AND GAS RECOVERY
Pages 159-171
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From page 159... ...
If the original volume of the reservoir is say 1,000 units and 800 units are swept by invaded water with a recovery factor of 60 percent, then the overall recovery factor is Recovery Factor = 0.60 x = 0.48 or 48% In reservoir engineering terminology, for this example, 800/1000 is a sweep efficiency of 80 percent. In the Federal Power Commission report, estimates of the physically recoverable gas assume that the entire reservoir volume is swept by invading water.
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From page 160... ...
Associated Gas Reservoirs In oil reservoirs without initial gas caps, the depletion mechanism results in oil recoveries usually in the range of 10 to 25 percent. However, recovery of the dissolved gas is essentially 100 percent.
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From page 161... ...
In depletion oil reservoirs, with or without initial gas caps, actual gas recovery approaches 100 percent, therefore physically recoverable gas also approaches this value. Under active water drive, physically recoverable gas, both dissolved and in caps, may considerably exceed actual recovery by a factor determined by the sweep efficiency in the oil zone and overlying cap.
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From page 162... ...
This property is the ratio of void space to rock material in the reservoir and is normally described as a percentage. The transmission of a fluid through a reservoir is related to a property described as permeability, a function of the degree to which the void spaces in the reservoir are connected.
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From page 163... ...
To determine the amount of natural gas contained in a reservoir, it is necessary to be able to accurately describe its volume in terms of areal extent and thickness. Such a determination is only possible if a sufficient amount of accurate geological information is available.
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From page 164... ...
At the stage of early exploration of a reservoir, the amount of geological information is not adequate to determine the areal extent even to this degree of accuracy. Thus one obvious error in determining reserves of natural gas steins from faulty (inaccurate)
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From page 165... ...
Carbonates and sandstones are the two major rock types of petroleum reservoirs. Condensate vaporizing volume ratio - the volume of gas vapor obtained from a unit volume of liquid condensate under pressure when the pressure of the condensate is reduced to atmospheric.
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From page 166... ...
Drilling mud - mud formed of clay particles suspended in water or oil used in well drilling for the purpose of lubricating the hole, preventing caving, controlling formation pressure, cooling and lubricating the bit, and carrying formation cuttings to the surface. Drill stein test - procedure for releasing reservoir gas and fluids into a perforated anchor pipe attached to the drill pipe to measure reservoir pressures and flow capacity.
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From page 167... ...
Induction-Electrical log - an electric log obtained without the use of electrodes, by lowering into the uncased borehole a generating coil (fed with alternating current) that induces in rocks surrounding the borehole currents that are concentric with the hole and that are detected by a receiver coil giving a continuous record of the conductivity with depth.
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From page 168... ...
Reservoir volume factor - factor by which standard surface volumes of oil are multiplied to obtain reservoir volumes. Residual gas saturation - the fraction of the pore space in a rock which contains gas after depletion, usually applied to water drive.
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From page 169... ...
Solution gas-oil ratio - the volume of gas disolved in a unit-volume of oil, usually expressed in standard cubic feet of gas per barrel of oil. Specific gravity of separator condensate - the ratio of the mass of the body to the mass of an equal volume of water at standard conditions, measured by means of a hydrometer using a scale measured in degrees API (American Petroleum Institute)
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From page 170... ...
or may be due to naturally occurring reservoir waters. Water saturation - the fraction of pore space in a rock which contains water.
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