Experimental Study on the Effects of Polymers on Soil Microorganisms Based on High-Throughput Sequencing Technology

Dagang Oilfield is developed using polymer flooding technology. The process of polymer injection and produced liquid treatment is completed on the surface, which has the risk of accidental leakage. There are few researches conducted to study the effects of polymer leakage on soil and surface microorganisms. It is urgent to effectively evaluate the spatial and temporal distribution, pollution scope and biological pollution degree of polymer leakage. This work employed genetic high-throughput sequencing technology to analyze the biodiversity of soil samples at a depth of 1400 mm near the polymer injection and water injection wells in Gangxi Area. The polymer leakage was simulated to analyze its migration behavior in soil and monitor the changes of microbial species through soil column leaching and irrigation experiments. The experimental results indicate that the local biodiversity was developed in polymer injection and water injection wells. There are many kinds of bacteria and the quantity is basically the same, indicating that the microbes in the current polymer injection area were not contaminated by polymers. In laboratory soil column experiment, 2000 mg/L polymer was continuously rinsed, and the polymer migrated to 1400 mm after 180 days. However, most of the polymer was consumed in the process of migration, and the residual amount was only 3.2%–-16.8%. There is minor change in the major soil microbial groups after polymer leaching, indicating that the polymer at the current mine concentration will not significantly affect the microbial flora. The research work conducted in this paper is of great significance to realize the dual purpose of increasing oil production and protecting the environment in old oil fields and to promote the industrial application of polymer flooding technology.