Development of an in situ emulsifying/ultra-low-interfacial-tension cyclic flooding system for medium- and low-permeability reservoirs

Abstract

Medium- and low-permeability reservoirs are important in oilfield development. However, due to their characteristics of poor pore permeability and high heterogeneity, the development of suitable technologies has been very difficult. In this study, an in situ emulsifying/ultra-low-interfacial-tension cyclic flooding system has been developed for low- and medium-permeability reservoirs. Based on the hydrophilic-lipophilic balance (HLB) value method, an emulsifying surfactant ASD with Span 80 (sorbitan monooleate) as the main component has been identified as highly promising through screening. At mass fractions of surfactant ASD between 0.2% and 0.6%, the extent of water separation from the emulsion is greatly reduced, and the W/O emulsion can effectively improve the mobility ratio and increase the sweep volume. The surfactant SA synthesized in our laboratory reduces the interfacial tension of crude oil to 10⁻⁴ mN m⁻¹. Laboratory core flooding experiments have shown that multiple rounds of alternating injection with aqueous solutions of surfactants ASD and SA can improve oil recovery by 22.25%. Upon injecting a low-viscosity aqueous solution of surfactant ASD, it emulsifies crude oil in situ under reservoir conditions, solving the problems of difficult polymer injection and insufficient spread. Our work provides useful insights for the development of low- and medium-permeability reservoirs.

Keywords:

• Cyclic flooding
• emulsifying
• enhanced oil recovery
• hydrophilic-lipophilic balance value
• ultra-low interfacial tension

Acknowledgments

We sincerely acknowledge the support from the Applied Technology Research and Development Program Project in Heilongjiang Province (GA20A201). We are grateful to the management of Daqing No. 3 Oil Production Plant for providing us with crude oil.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

Applied Technology Research and Development Program Project in Heilongjiang Province.