Crude-Oil-Water Emulsions to Improve Fluid Flow in an Oil Reservoir

Abstract

A field test was conducted to see if oil-in-water emulsions, prepared from petroleum crude oils, would reduce water channeling from injection to producing wells. In a two-year period after emulsion treatment of three water-injection wells, fluid production from offset wells showed increased oil recovery and lower water-oil ratios. Sweep efficiency was also improved. Introduction Channeling of injected water through high-permeability zones in heterogeneous reservoir sands results in low sweep efficiency in the displacement of crude oil. In efforts to improve the distribution of water injected into wells in waterfloods, wellbores have been treated with such solids as cement, ground limestone, and ground leather. However, even if such shallow-penetration methods do effect a better distribution of water into the formation at the wellbore, they are not likely to result in better sweep efficiency unless the higher-permeability zones are separated by shale breaks of very much lower permeability. Even shale breaks with low permeabilities may allow appreciable crossflow because the cross-formation surface areas are large compared with the formation areas at the flood fronts. A deep-penetration method should be more effective. Techniques for obtaining deeper-penetration plugging agents have been reported. These include the use of silica gel, rubber latex, and asphalt. In recent laboratory studies it was shown that oil-in-water emulsions possessed properties that suggested greater oil recovery. Injection of emulsion into sandstone cores improved sweep efficiency by improving the fluid flow heterogeneity of the sandstone cores. Field Investigation, Midway-Sunset Field, Section 5K This paper presents results obtained by injecting surface-prepared oil-in-water emulsion into water injection wells of a waterflood in progress at Section 5K of the Midway-Sunset oil field near Taft, Calif. the forming sections present briefly the geology, the waterflood results, and the results obtained by injecting 33,000 bbl of emulsified crude oil. Geological Information Fig. 1 is a structural map of the Section 5K area, contoured on top of the second finger, Top Oil sand. The structural nose dips to the southeast. A fault is shown as a heavy dashed line running just east of Wells 36, 109, and 126. Fig. 1 also shows an electric log, indicating the thicknesses and depth relationships of the producing intervals. The sands under flood are the first and second fingers of the Top Oil sands, and the Kinsey sand. Well-location hexagons indicate the wells and sands involved in the emulsion-treated and waterflooded areas. The legend gives the key to the hexagons. Note that in many wells not all sands are open. The average permeability of the first and second finger Top Oil sands and the Kinsey sand is 450 md. The sand thicknesses in both the waterflooded and the emulsion-treated areas arefirst finger, Top Oil, 10 to 20 ft;second finger, Top Oil, 10 to 11 ft; andKinsey, 6 to 12 ft. The oil gravities are about 20 degrees API for the first and second finger Top Oil sands, and the Kinsey oil gravity is 25 degrees API. JPT P. 721