Performance Identification and Application of Microorganism WXX-2 for Oil Recovery

Abstract

Employing the oil-degrading microorganism WXX-2 isolated from high-salinity reservoirs in Qinghai Oilfield, field applications were conducted to alleviate wax deposition and enhance oil recovery efficiency. To assess the behavior of WXX-2, A set of laboratory experiments was performed, including environmental adaptability evaluation, emulsifying property determination, viscosity reduction rate measurement, and physical simulation oil displacement experiments. Meanwhile, field trials were carried out to verify its application value in wax removal/prevention and oil recovery enhancement. WXX-2 was capable of growing and reproducing under the conditions of salinity up to 150,000 mg/L, pH ranging from 6 to 9, and temperature of 30–50°C. It was found that the EI24 value of WXX-2 fermentation supernatant was as high as 94.6%, and the surface tension value is 27.36 mN/m. At 30°C and 37°C, The measured viscosity reduction ratios of crude oil were 96.45% and 98.2%, respectively. The physical simulation oil displacement experiment showed that WXX-2 could increase oil recovery by 25.34%. In field applications, 407 well-times of wax removal/prevention operations, 7 well-times of huff-puff treatments, and 2 well-group microbial flooding tests were conducted. The average well-washing cycle was prolonged by 83 days due to wax removal and control; the cumulative oil increment from huff-puff treatments reached 1079 tons, and that from microbial flooding amounted to 838 tons. Both laboratory research and field application results indicated that WXX-2 can significantly extend the wax deposition cycle of oil wells and enhance crude oil recovery, thus exhibiting broad application prospects.