A simple, reliable method for the determination of the surface area of calcium carbonate is described. The method is based upon the extent of exchange between a calcium carbonate precipitate and radioactive, calcium-45 ions in solution. The procedure gives results reproducible to =t5% when averages of several determinations are used. Within a given series, however, results may differ by as much as 20%. The isotopic exchange method agrees well with values obtained by an electron microscope method for smallparticle-size samples, but gives low values for samples of large-size particles. Samples of lower surface areas show good agreement of comparison with the standard BET method but samples of high surface areas give high vesults. Limited tests with a liquid phase absorption method, using carbon-14 labeled stearic acid, indicate that good agreement can be obtained with the surface area values determined by the exchange method for both large-and small-particle-size samples.

This paper was prepared for the 42nd Annual California Regional Meeting of the Society of Petroleum Engineers of AIME, held in Los Angeles, Calif., Nov. 4–5, 1971. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract A simple micellar solution or microemulsion has been tested for its oil displacement capabilities in a sandstone core. The micellar solution was prepared using crude oil, water and a phosphate prepared using crude oil, water and a phosphate ester surfactant. Phase studies at 74 degrees F showed that a micellar solution existed when the phosphate ester surfactant concentration was 4 to 8 percent by volume or greater in a sour crude oil and water system. Similar concentration requirements were exhibited by a sweet crude oil-water system. Tests at elevated temperatures showed that the microemulsions tended to degrade as temperature was increased. Partial and total neutralization of the acid surfactant improved the microemulsions tolerance of higher temperatures. Oil displacement tests showed that the micellar solution employed was capable of displacing 90 percent of the core's oil saturation. Slug floods of 30 percent PV and larger yielded an oil displacement percent PV and larger yielded an oil displacement efficiency of 90 percent also. Water-driven slugs were employed. Displacement efficiencies exhibited by oil-rich and water-rich micellar solutions were slightly different. These differences are explored via dilution arguments. Introduction Numerous patents and publications have appeared regarding the use of micellar solutions or microemulsions for secondary recovery of oil and the stimulation of water injection wells. These papers report the use of certain petroleum sulfonates as the solubilizing agent. The excellent capabilities of the petroleum sulfonates has been demonstrated. The purpose of this study was to explore the oil displacement merits and certain phase characteristics presented by a different solubilizer - a mono substituted presented by a different solubilizer - a mono substituted ortho phosphate ester. The surfactant employed is manufactured by BASF Wyandotte Corp. and marketed as KLEARFAC AA-420. This surfactant is an anionic, biodegradable liquid that exhibits solubilizing properties within a broad pH spectrum 17 Used primarily in metal cleaning and textile processing, its capability of recovering oil has not been previously studied. Preliminary phase behavior studies showed that KLEARFAC AA-420 was an excellent solubilizer of crude oil and water. This characteristic prompted a series of oil displacement tests plus further phase behavior tests at elevated temperatures.

A surjactant waterflood, using a block copolymer oj ethylene and propylene oxide (PL.URONIC L64*), was started in i 956 in Kansas to determine the commercial feasibility O! such a process. The production jorwation was the Bardesville sand at a depth of 1,400 jt. Leases in the test area had attained both primary and secondary production peaks, and were on a normal decline when the tests were initiated. The injection wells were taking water at a reasonable p,-es.rure and none of the operating conditions were particularly unusual. The leases were selected primarily because of normal operating conditions, and not because oj any serious problems demanding remedie>. Oil production and water injection data were recorded during the IO-year test period, and their compilation indicates that the surjactant resulted in an increase of about 9 percent in secondary oil production.Other benefits derived jrom the surjactant injection were lower injection pressure that resulted in reduced power consumption and reduced erosion oj the pumps; and lower calcium scale buildup. These jringe benejits more than oflsct the cost oj the surjactant used.