Regular Article

Enhanced oil recovery after polymer flooding by wettability alteration to gas wetness using numerical simulation

¹ School of energy resources, China university of Geosciences (Beijing), 29 Xueyuan Road, Beijing 100083, China
² Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Enrichment Mechanism, Ministry of Education, Beijing 100083, China
³ Department of Energy Resources Engineering, Stanford University, Stanford, CA 94305, USA
⁴ Jianghan Oilfield Branch, Sinopec, Beijing 100728, China

^* Corresponding author: likewen@cugb.edu.cn

Received: 22 December 2017
Accepted: 28 June 2018

Abstract

Polymer flooding, as one of the Enhanced Oil Recovery (EOR) methods, has been adopted in many oilfields in China and some other countries. Over 50% oil remains undeveloped in many oil reservoirs after polymer flooding. It has been a great challenge to find approaches to further enhancing oil recovery when polymer flooding is over. In this study, a new method was proposed to increase oil production using gas flooding with wettability alteration to gas wetness when polymer flooding has been completed. The rock wettability was altered from liquid- to gas-wetness during gas flooding. An artificial oil reservoir was constructed and many numerical simulations have been conducted to test the effect of wettability alteration on the oil recovery in reservoirs developed by water flooding and followed by polymer flooding. Production data from different scenarios, water flooding, polymer flooding after water flooding, gas flooding with and without wettability alteration after polymer flooding, were calculated using numerical simulation. The results demonstrate that the wettability alteration to gas wetness after polymer flooding can significantly enhance oil recovery and reduce water cut effectively. Also studied were the combined effects of wettability alteration and reservoir permeability on oil recovery.