Advantages of Brines in Secondary Recovery of Petroleum by Water-flooding

Abstract

Abstract The necessity for getting more water into sands of low permeability in anysecondaryrecovery water-flood operation in order to recover all the availableoil always has been a major problem. In the early days of waterflooding theaddition of soda ash and caustic soda to fresh input waters was recommended andtried without success in the Bradford field. The most frequent difficulty wassand plugging. The use of natural and artificial brines often has beensuggested for water-flooding, in the belief that laboratory observations ofdecreasing fresh-water throughput rates in measuring water permeabilities ofconsolidated sand cores might be partially explained by swelling ofclays. A review of available literature bearing on the subject and related laboratoryexperiments are presented herein, offering an explanation for failure in use ofsoda ash, and caustic soda waters and supporting the recent concept that everywater used for input purposes in the secondary recovery of oil should possesssuch physical and chemical characteristics as to keep the clay content of theproducing sands in a permanently flocculated condition. Produced brines meetthis requirement. Their use is recommended as a means of increasing intakerates of tight sands and oil recoveries, as a solution to brine-disposalproblems, and as a means of conserving a natural resource. Introduction There is a general belief among those engaged in the secondary recovery of oilby water-flooding that one of the most important requirements for the successof any such project is an adequate supply of good, fresh water. Fresh watershave the advantages of being more easily stabilized than salt waters and ofbeing usable about the lease for all purposes. The use of brines forwaterflooding never has been given much consideration in the Pennsylvania Gradearea. The use of brines in Mid-Continent operations has been considered largelyas a substitute for fresh waters, which were economically unobtainable for manyoperations. Estimated recoveries for some water" drive fields indicate that less of theoriginal oil in place will be left upon abandonment than with the above-averagepractices used in Pennsylvania Grade water-flood operations. Lower residual oilsaturations than 25 pet of the pore space following the water-flooding of ThirdBradford sand cores in the laboratory are unusual. In comparison, water-flushedsands surrounding any virgin oil pool are found to be practically devoid ofoil. T.P. 2127