Volumetric and Phase Behavior of Oil and Gas from Paloma Field

Abstract

Abstract Samples of liquid and gas were obtained from the primary separator of a well inthe Paloma field. The volumetric properties of the samples and of sixsystematically chosen mixtures of the samples were experimentally determined at100?, 190?, and 250?F. at pressures up to 5000 lb. per sq. inch. From these data the influence of pressure and temperature upon the compositionand specific volume of the bubble-point liquid and of the retrograde dew-pointgas was established. The formation volumes and gas-oil ratios of the mixturesinvestigated were calculated on the basis of the plant-product oil, which isdefined as the isobutane and less volatile portion of each mixture. The resultsare presented in graphical and tabular form. The volumetric behavior of the mixture corresponding to that produced by thewell at the time of sampling was determined for 235?F., the reported reservoirtemperature, by graphical interpolation of the experimental data with respectto composition and temperature. The results indicate that the well-productionmixture probably existed as a gas at its retrograde dew point under theconditions of temperature and pressure believed to prevail in the producingzone at the time of sampling. The effect upon the phase behavior occasioned by the omission from thewell-production mixture of certain components of intermediate molecular weightwas investigated. In the first case, all of the isobutane and n-butane, andsubstantially all of the isopentane, were removed from the mixture of trapsamples corresponding to the well production. In the second case, all thepropane, isobutane and n-butane, and substantially all of the isopentane, wereremoved. Both modifications led to considerable increases in the retrogradedew-point pressure at 235?F.; an increase of 558 lb. per sq. in. above that ofthe unmodified well-production mixture in the first case, and an increase of1208 lb. per sq. in. in the second. It was concluded that-the materials remaining after the removal of certaincomponents of intermediate molecular weight could not be injected back into thereservoir in the same proportion in which they were produced without entailingappreciable loss of liquid material through condensation within theformation. Introduction Under the usual conditions of production practice, petroleum arrives at thesurface of the earth in a physical state considerably different from that inwhich it existed in the underground reservoir. The relative rates of productionand the properties of oil and gas measured at surface conditions do notconstitute, in general, even a qualitative description of the fluids existingin the reservoir. The estimation of reserves and the attainment of optimum efficiency with regardto rate, quantity, and cost of production require accurate data concerning thephysical properties of petroleum throughout large changes in pressure andtemperature. T.P. 1861