Displacement of Oil from Porous Media by Water or Gas

Abstract

Abstract Laboratory apparatus has been devised which permits study of the displacementof oil from cores by water and by gas. The cores used contained interstitialbrine as well as oil. Experiments were run to determine the comparative effect of varying theproperties of the fluids used. No great effect was noted on the maximumdisplacement achieved. This observation made it unnecessary in initial work touse fluids in their exact reservoir conditions. Consequently, the displacementswere run at near-atmospheric pressure in Pyrex glass equipment, using strippedcrude oils. Introduction and Theory The chief object of this work has been to determine the efficiency of gasand water as primary agents for displacing oil from reservoir rock underlaboratory conditions in which capillary phenomena were predominant. To thisend the maximum displacement of oil from cores has been ascertained. Thismaximum displacement may not be equal to the maximum displacement from areservoir; but it will he a close approximation to it sometimes, and othertimes the laboratory information will be useful in reservoir engineeringpredictions. It is believed that the laboratory experimental maximum representsthe upper limit for the reservoir recovery. The experiments were carried out by obtaining cores of interest from thereservoir, and filling the pores with interstitial brine and oil with therestored state technique. Then the oil was displaced from the core as describedlater, either by brine from below, or by gas from above. The former type ofdisplacement suggests analogy to production by water drive, but not to waterflooding, for reasons discussed below. The latter type of displacement isbelieved to simulate production by gas cap displacement. The displacements were performed by what may be termed thecapillary-pressure method. The cores are placed in capillary contact with anoil-wetted membrane which has very small pores (about I micron in diameter).Pores of this size will transmit oil hut prevent the passage of gas or water, unless the pressures used are higher than the capillary pressures employed inthis work. Accordingly, use of the membrane makes it possible to apply acapillary pressure differential between the displacing phase and the oil in thecore. T.P. 2433