Controlled Evaluation of a Surfactant in Secondary Recovery

Abstract

Abstract A surfactant waterflood, using a block copolymer of ethylene and propylene oxide (PLURONIC L64*), was started in 1956 in Kansas to determine the commercial feasibility of such a process. The production formation was the Bartlesville sand at a depth of 1,400 ft. Leases in the test area had attained both primary and secondary production peaks, and were on a normal decline when the production peaks, and were on a normal decline when the tests were initiated. The injection wells were taking water at a reasonable pressure and none of the operating conditions were particularly unusual. The leases were selected primarily because of normal operating conditions, and not primarily because of normal operating conditions, and not because of any serious problems demanding remedies. Oil production and water injection data were recorded during the 10-year test period, and their compilation indicates that the surfactant resulted in an increase of about 9 percent in secondary oil production. Other benefits derived from the surfactant injection were lower injection pressure that resulted in reduced power consumption and pressure that resulted in reduced power consumption and reduced erosion of the pumps; and lower calcium scale buildup. These fringe benefits more than offset the cost of the surfactant used. Introduction During the past several decades, considerable research has been carried out on secondary recovery of crude oil that remains in the producing formation despite the most efficient, current primary production practices. Methods are constantly sought of increasing recovery of oil, while at the same time improving the economic efficiency of operations. One method that has received intensive study over the years is the use of a surfactant as a waterflood additive. Laboratory tests show conclusively that dilute solutions of surfactants remove considerably more oil from unconsolidated sand cores than does water alone. The loss of surfactant by adsorption at solid-liquid interfaces has caused serious doubt that surfactants can be used economically as waterflooding additives. This is especially true with anionic and cationic surfactants, and to a lesser extent with nonionic surfactants. This work was undertaken to determine the effectiveness in increasing oil production by injecting water containing small quantities of a nonionic surfactant. The surfactant selected was PLURONIC L64*, a block copolymer based on ethylene and propylene oxide, having the following structure: Selection of the Test Site The selection of the test site, a typical shoe-string sandstone type of field located at Batesville pool, Toronto District of Woodson County, Kans., was made because of its normal primary and secondary recovery operating conditions, and not because of any serious operating problems. When the tests were begun, the field was problems. When the tests were begun, the field was experiencing the customary post-peak production decline of a waterflood. Using for the tests a field that was on a normal production decline, while maintaining constant all variables production decline, while maintaining constant all variables other than the addition of the surfactant, was of paramount importance if success or failure was to be attributed paramount importance if success or failure was to be attributed to a particular cause. It was reasoned that if a surfactant was added to the injection waters and nothing else was done to influence the oil production or injection of water, the effects of the surfactant on the flood could be determined precisely. Production History Production HistoryThe first well in the tested field was drilled in 1935. Gas repressurization began immediately, but it was not until Aug., 1938, that the major portion of the field was developed. During the period of repressurization, 1,700 MMcf of gas was injected. As can be seen from the curves of Fig. 1, the production peak from gas injection was attained in 1937 and a normal production decline followed. Early in 1942, water injection wells were drilled and injection of water was initiated. JPT P. 1320