Experimental Studies of the Detection and Reuse of Produced Chemicals in Alkaline/Surfactant/Polymer Floods

Abstract

SummaryAlkaline/surfactant/polymer (ASP) flood processes have been applied increasingly in oil fields because of their contribution to high ultimate oil recovery. However, a major technical challenge is determining how to significantly reduce the amount and the cost of chemicals used so that ASP floods can become cost-effective as well. On the other hand, some field applications show that alkali, surfactant, and polymer concentrations remain relatively high in the produced liquids of ASP floods. Thus, successful detection and reuse of these chemicals can substantially minimize the capital cost and the environmental impact. In this paper, several methods are applied to detect each chemical and quantify its concentration in the produced liquids. In addition, reinjection tests of the produced chemicals are conducted for further enhancing oil recovery. More specifically, first, the total interactions of each chemical with the oil/brine/rock system are studied. With the developed detection methods for each individual chemical used in ASP floods, the total loss of each chemical is measured. The chemical loss is caused by its chemical reactions with the crude oil and the reservoir brine, as well as its adsorption onto the rock surface. Second, coreflood tests are performed for alkaline floods (AFs), surfactant floods (SFs), alkaline/surfactant floods (ASFs), and ASP floods (ASPFs) to determine their respective tertiary oil recoveries. Hence, a better understanding of how each chemical contributes to enhanced oil recovery (EOR) is achieved. Third, typical chemical concentrations in the produced liquids are measured and compared with those in the injected slugs to determine the potential of reusing these chemicals in practice. Finally, the coreflood tests of reusing these produced chemicals are carried out by reinjecting the produced liquids into new sandpacks or Berea-sandstone cores. The reinjection coreflood-test results show that the produced chemicals can be reused effectively to enhance oil recovery. It is anticipated that the detection methods and reuse schemes studied in this experimental work should facilitate the design, optimization, and implementation of ASP field flood projects.