Investigations on the Recovery of Oil from Sandstones by Gas Drive

Abstract

In the past few years a great deal of precise information has been obtainedabout the relation of natural gas to oil production. The improvement of ourunderstanding has been of great value, both in prolonging the life of wells andin providing a much needed technical background for the legal problem ofproration. But there are two principal aspects of the problem of production. Itis necessary to consider not only the energy available, in the form ofcompressed and dissolved gas and in the pressure of driving water, but also thetenacity with which the sandstone holds the oil. The amount of oil that eachsand condition will produce under given conditions of gas content should bedetermined. Hitherto the effect of the sand have been judged by a study of theflow of each well coupled with a procedure for extrapolating the productioncurve; but, as is well known to evaluation engineers, such production curvesare subject to changes that are not well understood, and often are affected byoutside disturbances. On the whole, the concept of "potential production" is vagueprincipally because the influence of the sand in production is not known beyondthe simple ideas of porosity and permeability. The permeability is a quantitythat has only inference value where mixtures of gas and oil or of gas, oil andwater are present. Excellent studies of the production of oil from reservoir packed withunconsolidated sand are available, but there studies treat largely ofsmall-scale analogies to a producing field, and the conclusions to he derivedfrom them are necessarily of a qualitative character because it is not known inwhat way these miniature oil fields resemble large ones.