An experimental investigation of the effect of carbon dioxide on steam drive recovery /

Abstract

A large number of displacement tests were conducted on unconsolidated sand packs of 3 inches in diameter and 24 inches in length. The sand packs were saturated with crude oils of gravities 15, 20, and 26(DEGREES)API. A mixture of varying concentration of carbon dioxide in steam, ranging from 0.0 to 0.006 SCF CO(, 2)/cm.('3) steam (water equivalent), was injected at different steam temperatures, rates, and pH to evaluate the effect of each individual parameter on oil recovery.

The examination of the results obtained indicated that: (1) the injection of carbon dioxide with steam increases the rate of recovery significantly, (2) the recovery is affected by the concentration of carbon dioxide in the injected steam and is maximized at a concentration of about 0.004 standard cubic feet of carbon dioxide per cubic centimeter of cold water equivalent steam, (3) the overall recovery depends on oil viscosity and hence the API gravity. It improves by 8% in case of 15(DEGREES)API oil, 4% in case of 20% API oil, whereas no significant improvement in ultimate recovery, over the conventional steam flooding process, was observed in case of 26(DEGREES)API oil, (4) the recovery decreases with increasing pressure and hence the temperature, (5) the recovery is rate dependent and is maximized at a steam injection rate of 30 cm.('3)/minute, (6) the recovery is not affected by pH, when steam and carbon dioxide are injected simultaneously.

A laboratory study was undertaken to evaluate the effects of carbon dioxide injection with steam on heavy to intermediate oil recovery. The effects of other operating parameters, such as pressure, temperature, injection rate, oil viscosity, and pH on oil recovery were also investigated.