Effect of viscosity and interfacial tension of surfactant–polymer flooding on oil recovery in high-temperature and high-salinity reservoirs

Zhiwei Wu,Jie Yu,Xiang’An Yue,Tao Cheng,Heng Yang

doi:10.1007/s13202-013-0078-6

Zhiwei Wu, Jie Yu + Show 3 more

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https://doi.org/10.1007/s13202-013-0078-6

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Abstract

This study aims to analyze the influence of viscosity and interfacial tension (IFT) on oil displacement efficiency in heterogeneous reservoirs. Measurement of changes in polymer viscosity and IFT indicates that viscosity is influenced by brine salinity and shearing of pore media and that IFT is influenced by salinity and the interaction between the polymer and surfactant. High concentrations (2,500 and 3,000 mg/L) of polymer GLP-85 are utilized to reduce the effect of salinity and maintain high viscosity (24 mPa s) in formation water. After shearing of pore media, polymer viscosity is still high (17 mPa·s). The same polymer viscosity (17 mPa·s) is utilized to displace oil, whose viscosity is 68 mPa·s, at high temperature and high pressure. The IFTs between surfactant DWS of 0.2 % in the reservoir water of different salinities and crude oil droplet are all below 10−2 mN/m, with only a slight difference. Surfactant DWS exhibits good salt tolerance. In the surfactant–polymer (SP) system, the polymer solution prolongs the time to reach ultra-low IFT. However, the surfactant only has a slight effect on the viscosity of the SP system. SP slugs are injected after water flooding in the heterogeneous core flooding experiments. Recovery is improved by 4.93–21.02 % of the original oil in place. Furthermore, the core flooding experiments show that the pole of lowering the mobility ratio is more significant than decreasing the IFT of the displacing agent; both of them must be optimized by considering the injectivity of the polymer molecular, emulsification of oil, and the economic cost. This study provides technical support in selecting and optimizing SP systems for chemical flooding.

Highlights

Polymer flooding has been employed successfully in Daqing Oilfield in China for decades; it contributed to the oil recovery of more than 10 % of original oil in place (OOIP) after water flooding (Wang et al 2009).J Petrol Explor Prod Technol (2014) 4:9–16Alkaline–surfactant–polymer (ASP) flooding can effectively reduce oil residual saturation to reduce interfacial tension (IFT) and the mobility ratio between the water phase and oil phase (Clark et al 1988; Meyers et al 1992; Vargo et al 1999)
This study aims to analyze the influence of viscosity and interfacial tension (IFT) on oil displacement efficiency in heterogeneous reservoirs
Polymer viscosity was measured in high salinity under constant temperature because salinity affects the viscosity and IFT of the binary system

Summary

Introduction

Alkaline–surfactant–polymer (ASP) flooding can effectively reduce oil residual saturation to reduce interfacial tension (IFT) and the mobility ratio between the water phase and oil phase (Clark et al 1988; Meyers et al 1992; Vargo et al 1999). Surfactants with concentrations higher than the critical micelle concentration (CMC) can achieve ultra-low IFT. In formulas involving the capillary number, ultra-low IFT between the binary system and oil drop in a homogenous core yields the lowest residual oil saturation and the highest oil recovery. Highest oil recovery can be achieved under optimum IFT and not under the lowest IFT of the binary system This concept (Wang et al 2010) is based on light oil reservoir with high permeability and low temperature.

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