Solvent Stimulation of Viscous Crude-Oil Production

Abstract

Abstract To improve both the rate and volume of production of viscous crude oils, the USBM made a production of viscous crude oils, the USBM made a study of solvents to stimulate production. Five laboratory methods were used to evaluate the effectiveness of several solvents in the stimulation of viscous oil production. These methods were (1) viscosity reduction, (2) gravity drainage production from sand columns, (3) displacement from capillary tubes, (4) effect of organic acids on crude oil viscosity and (5) hydrocarbon analysis. Solvents ranging from refinery cuts to chemical compounds were used with six California and one Kansas crude oils. Results indicated that small quantities of effective solvents greatly reduced the viscosity of viscous crude oils. The rate and volume of production of viscous crude oils by gravity production of viscous crude oils by gravity drainage from laboratory sand columns were increased greatly by small quantities of effective solvents. It was also found that low molecular-weight aromatic-hydrocarbon solvents effectively removed viscous crude oils from glass capillary tubes. Introduction Because of the rapidly growing national demand for energy, a study was made by the USBM of improved methods for producing viscous crude oils. Previous USBM studies showed that over 100 billion bbl of viscous crude oil are present in over 2,000 petroleum reservoirs. present in over 2,000 petroleum reservoirs. California has the largest resource of viscous crude oil — about 75 percent of the oil classified as most favorable for recovery by stimulative methods. Exploration costs for viscous oils are almost nonexistent because the large reserves are in known fields where many producing facilities already exist. Interest producing facilities already exist. Interest in the viscous crude oil resource has been enhanced further by the development of high-yield hydrocracking refinery processes to convert low cost viscous crude oils into valuable fuels. Some hydrocracking processes yield up to 80 percent volatile fuels from viscous oils. percent volatile fuels from viscous oils. In this study, methods of evaluating solvents were examined in the San Fracisco Energy Research Laboratory, and the results obtained using viscosity reduction, sand columns, capillary tubes, addition of organic acids, and hydrocarbon analysis are described. Previous Related Work Previous Related Work A review of published information (1958 to 1968) showed that stimulation of the production of viscous crude oils in California has been improved by the addition of steam to the reservoir. Stimulation of production of viscous crude oils has been obtained by injecting large quantities of steam to heat the oil above normal reservoir temperature. Improved production by the addition of heat to decrease the viscosity of crude oil in the reservoir has been outstanding in the Kern River field of California where production has increased from 9,500 bbl a day in production has increased from 9,500 bbl a day in 1950 to 70,000 in 1970.