Some Experiments on the Behavior of Natural Gas III an Oil-sand Reservoir

Abstract

In connection with some of the experiments carried out by the writer on the behavior of gas and oil in a sand reservoir, an interesting phenomenon wasobserved which may throw some new light on the problem of recovery of oil froma natural reservoir. The experiments are intended to show the effect of the surface area of the occluded gas masses, originally present in a reservoir, on the further evolution of gas from the oil and its consequent effect upon therate of production of oil. The apparatus used in the experimental work is shown in Fig. 1. It consists primarily of a sand reservoir R and a displacement chamber D, whichis used to induce small variations in volume. The reservoir and displacementchamber form a unit, and a lowering of the plunger D is equivalent toincreasing the volume occupied by the oil and gas in the reservoir. The reservoir was first filled with dead oil and maintained under pressureuntil it was ascertained that most of the free gas had gone into solution. Thevolume of free gas present in the reservoir was computed from the coefficient of compressibility of the fluids by means of the displacement chamber D, reading to 0.005 c.c. and a special gage J reading to 0.02 lb. per sq. in. The oil was saturated with gas under pressure in reservoir S by circulating the oilfor a long period of time through the gear pump B. Subsequently, the saturated oil was circulated through the sand reservoir following the circuit S6, B, S5, R4, the sand reservoir R, R1, R2, F4, F1, back to reservoir S. In the following experiments the sand reservoir R was filled with gas-saturatedoil at a pressure of 415 lb. per sq. in. with no free gas present. This wasascertained by closing off all the outlet valves and determining thecoefficient of compressibility of the system by means of the displacementchamber D. Much difficulty was encountered in eliminating all of the free gas masses fromthe oil reservoir.