Recent Advances in Polymer Flooding in China

Abstract

Polymer flooding is drawing lots of attention because of the technical maturity in some reservoirs. The first commercial polymer flooding in China was performed in the Daqing oilfield and is one of the largest applications in the world. Some laboratory tests from Daqing researchers in China showed that the viscoelasticity of high molecular weight polymers plays a significant role in increasing displacement efficiency. Hence, encouraged by the conventional field applications and new findings on the viscoelasticity effect of polymers on residual oil saturation (ROS), some high-concentration high-molecular-weight (HCHMW) polymer-flooding field tests have been conducted. Although some field tests were well-documented, subsequent progress was seldom reported. It was recently reported that HCHMW has a limited application in Daqing, which does not agree with observations from laboratory core flooding and early field tests. However, the cause of this discrepancy is unclear. Thus, a systematic summary of polymer-flooding mechanisms and field tests in China is necessary. This paper explained why HCHMW is not widely used when considering new understandings of polymer-flooding mechanisms. Different opinions on the viscoelasticity effect of polymers on ROS reduction were critically reviewed. Other mechanisms of polymer flooding, such as wettability change and gravity stability effect, were discussed with regard to widely reported laboratory tests, which were explained in terms of the viscoelasticity effects of polymers on ROS. Recent findings from Chinese field tests were also summarized. Salt-resistance polymers (SRPs) with good economic performance using produced water to prepare polymer solutions were very economically and environmentally promising. Notable progress in SRP flooding and new amphiphilic polymer field tests in China were summarized, and lessons learned were given. Formation blockage, represented by high injection pressure and produced productivity ability, was reported in several oil fields due to misunderstanding of polymers' injectivity. Although the influence of viscoelastic polymers on reservoir conditions is unknown, the injection of very viscous polymers to displace medium-to-high viscosity oils is not recommended. This is especially important for old wells that could cause damage. This paper clarified misleading notions on polymer-flooding implementations based on theory and practices in China.

Evaluating Factors Impacting Polymer Flooding in Hydrocarbon Reservoirs: Laboratory and Field-Scale Applications

“…Therefore, an increase in the viscosity of the injected liquid (as compared to just water) results in an increase in the capillary number in the porous media. In other words, the capillary forces become negligible compared to viscous forces [ 65 , 69 ]. A water-soluble polymer added to water at a concentration of 0.01–0.1% results in an increase in the viscosity of polymer solution of three to four times [ 70 ].…”

Remaining Oil Distribution Law and Development Potential Analysis after Polymer Flooding Based on Reservoir Architecture in Daqing Oilfield, China

“…Their crude oil production is falling rapidly. Polymer flooding is considered to be one effective technique to relieve the production decline of reservoirs [4][5][6][7]. In Daqing Oilfield, the largest continental sedimentary oilfield in China, polymer flooding technology has been tested and gradually implemented since 1972, and was commercialized in 1996.…”

Study on Micro-Displacement Mechanism and Reservoir Compatibility of Soft Dispersed Microgel

“…In order to solve the limitation that polymer flooding can only be used in the near-well area. Many scholars try to conduct “high-dose profile control”, also known as “deep profile control” [ 19 , 20 , 21 , 22 , 23 ], but the treatment radius is often no more than 10–20 m and the treatment cost is high. In addition, with the increase of water-cut in oilfields, the water-flooding contradiction changes from the shallow reservoir to the deep reservoir, or even the entire reservoir flow field.…”