Optimization of carbonate heavy oil reservoir development using surfactant flooding: From laboratory screening to pilot test

Abstract

Copyright 2020, Society of Petroleum Engineers. Bashkirian reservoir is a heavy oil fractured carbonate reservoir. It has a low temperature (23 °C) and anultra-high salinity (217.5 g/L). The low injectivity is the main problem that limits the efficient developmentof this reservoir. Hot water injection has been tried to solve this problem, but it did not work. The purpose ofthis work is to find an effective surfactant system for high salinity condition to increase the injectivity duringwater flooding. This paper presents the whole process from laboratory screening and numerical simulation topilot test. In laboratory, ten surfactants were evaluated by measuring interfacial tension (IFT) and wettabilitychange. For each surfactant, three concentrations were studied to obtain the optimal surfactant formulation.The optimal surfactants were used for filtration experiments to evaluate the effect of surfactant on theinjectivity and oil displacement efficiency. The effect of the best surfactant was assessed by reservoirnumerical simulation at the field scale. Eventually, the pilot test was implemented to test the effectivenessof surfactant injection. According to the ability to reduce IFT and change the wettability, oil displacementefficiency, the capacity of reducing injectivity, and production performance, as well as considering the costand accessibility of surfactant, one nonionic surfactant was eventually chosen for pilot test in the oilfield. The pilot test results show that this nonionic surfactant shows a very good effect on improving waterinjectivity. After the injection of surfactant, the wellhead pressure and downhole pressure were reducedfrom 40 at and 171.5 at to 24 at and 153.4 at), respectively. Surfactant injection increased additional oilproduction of about 1094 tones. The good effect of this nonionic surfactant showed in pilot test makes it agood candidate for wide application under high salinity condition to improve well injectivity as well as oildisplacement efficiency in the case of complex heavy oil carbonate deposits.