Polymer Injection in Heavy Oil Reservoir under Strong Bottom Water Drive

Abstract

Implementing Enhance Oil Recovery techniques in heavy oil reservoirs with strong bottom water drive has been a challenge in the oil industry. This paper describes an Enhanced Oil Recovery process in which polymer is injected into a clastic reservoir with a strong bottom aquifer drive bearing heavy-oil (250-500 cP). The high reservoir permeability (2-5 Darcy) enables stretching the viscosity limit of a standard polymer application. The presence of a strong bottom aquifer maintains high reservoir pressure, which could provide a challenge to injectivity. The close proximity of injectors to the oil water contact reduces the efficiency of the polymer flood through water fingering, and polymer loss to the aquifer. To best understand details of the influence of aquifer on the recovery process, test different development scenarios and address key uncertainties, detailed simulation study was conducted. The simulation results showed that the optimum development concept which would help reduce impact of polymer loss to the aquifer would be to utilize the currently existing and future horizontal producers, augmented with additional infill horizontal injectors placed approximately mid-way in the oil column. Optimization of the development was performed using the simulation model where the polymer viscosity, slug size, and injector location were optimized for net present value. Uncertainty analysis using the simulation model showed that factors such as poor injectivity, poor conformance control and high kv/kh ratio have negative impact on process efficiency. To address and mitigate these key risks and uncertainties a number of activities are underway. These activities include intensive laboratory tests, field injectivity test and a field trial where polymer is injected in newly drilled injectors. The paper discusses study to identify the optimum development concept, key uncertainties and associated risk reduction activities. Finally, this paper discusses the design and the surveillance aspects of the upcoming field trial.

Application of horizontal well discontinuous chemical flooding technology in Bohai oilfield

“…The system to increase the injection capacity selects water and acid liquid system and cooperates with the flushing operation. According to the length of the horizontal section, the injection volume of the acid liquid system is designed to be about 250 m (Al Azri et al, 2010).…”

“…The liquid production volume of a single well is determined according to the analysis results of the liquid production capacity in the chemical flooding stage of the production well. The daily production volume of 4 single wells is 150-600 m (Al Azri et al, 2010), and the daily production volume of the whole test area is 1250 m (Al Azri et al, 2010). The daily injection…”

“…The combination of horizontal well and chemical flooding technology has been applied in Pelican lake, Mooney, Seal, East Bodo oilfield in Canada (Delamaide et al, 2013a;Gao, 2011) and South Oman (Al Azri et al, 2010;Brooks et al, 2010) to conduct field tests of several wells, and the field tests have achieved certain oil increasing effects (Al Azri et al, 2010;Brooks et al, 2010;Gao, 2011;Delamaide et al, 2013a;Delamaide et al, 2013b). There are many horizontal wells in Bohai Oilfield, accounting for about 40% (Shi et al, 2020).…”

“…The chemical flooding potential of horizontal wells in Bohai Oilfield is huge (Liang et al, 2014;Liang et al, 2018). In general, the chemical flooding injection mode is continuous injection, which, combined with the reservoir heterogeneity and other reasons, is prone to cross flow along the high permeability strip during the development and production process, leading to the decline of oil increase effect and the rapid return of water cut, which can not achieve the desired effect (Azrin Al et al, 2010;Howe et al, 2015;Heesong et al, 2016;Xie et al, 2016;Bao et al, 2017;Erincik et al, 2017;Pal et al, 2018;Xu et al, 2019;Chang et al, 2021;Tan et al, 2021;Zhai et al, 2021). It is found in the study that the continuous chemical flooding of horizontal wells will also face the same problems due to the influence of factors such as toe effect of horizontal wells, large injection volume, thin reservoir and strong heterogeneity along the horizontal section.…”

Polymer Flooding of Heavy Oil - From Screening to Full-Field Extension

“…Al Azri (Al Azri et al 2010) studied polymer injection in the Nimr field in Oman, in a 30 m to 50 m thick heavy oil reservoir (viscosity 250 -500 cp) underlain by an active aquifer. They found that horizontal wells in combination with polymer injection could improve recovery but we suspect that this is largely influenced by the very short spacing (43 m) between injection and production wells.…”