超低渗油藏微生物吞吐技术的矿场试验

Microbial huff and puff field trial in ultra-low permeability reservoir

摘要:

【目的】通过对渭北低渗油藏内源微生物的研究，考察分离纯化的内源解烃菌产生表面活性剂和降解原油的能力、岩心驱替增油效率，同时验证其在超低渗油田单井吞吐矿场实验的应用效果，探讨微生物采油技术在超低渗油田提高采收率的工艺和可行性。【方法】采集超低渗油藏的油水样，应用油平板进行产表面活性剂解烃菌的分离，通过生理生化特性和16S rRNA基因序列分析对菌株进行种属鉴定，评价其油藏环境适应性，利用内源-外源功能微生物复配体系进行原油降解，在填砂管和岩心物模上进行驱油实验，将优化好的微生物复配体系应用于现场实施单井吞吐工艺的实验。【结果】从渭北某区块超低渗油藏的原油样品中分离得到一株铜绿假单胞菌(Pseudomonas aeruginosa)，命名为WB-001。该菌株可使发酵液的表面张力降至29.04 mN/m，使渭北原油蜡质含量降至8.48%。填砂管实验表明WB-001与外源枯草芽胞杆菌OPUS-HOB-001 (Bacillus subtilis)复配后，驱油效率较单纯水驱提高了9.72%；岩心驱替实验较水驱提高12.54%。微生物单井吞吐措施后，平均日产油由措施前的0.42 t增加到0.89 t，累计增油44.47 t；原油降粘率为11.70%，降凝率为9.41%，采出水表面张力降低幅度为18.93%。【结论】通过详细的室内评估和成功的矿场实验，证明微生物采油技术在超低渗油藏有一定的应用可行性，并为后续规模化应用提供了理论基础和物质基础，为超低渗油田的高效精细开发探索一条新的途径。

Abstract:

[Objective] To study the properties of endogenous microorganisms in Weibei Oilfield, we studied the ability of biosurfactant production, crude oil degradation and enhanced oil recovery on core displacement model of the isolated hydrocarbon oxidizing bacteria. Furthermore, we evaluated the effects of huff and puff field trial to discuss the process and feasibility for microbial enhanced oil recovery in ultra-low permeability and shallow reservoir. [Methods] We collected oil-water samples from ultra-low reservoirs and isolated surfactant producing hydrocarbon oxidizing bacteria by crude oil plate, identified the isolates by the physiological-biochemical properties and 16S rRNA gene sequence analysis, and then determined their environmental adaptation. Furthermore, we used an endogenous and exogenous microbial compound system to evaluate the abilities of crude oil degradation and enhanced oil recovery on both sand-pack and core-flooding physical model. Finally, the highly optimized microbial system was performed by the huff and puff process in a production well. [Results] A hydrocarbon oxidizing bacterium Pseudomonas aeruginosa, named WB-001, was isolated from ultra-low permeability reservoir in Weibei Oilfield. The fermentation broth surface tension and wax concentration were reduced to 29.04 mN/m and 8.48%, respectively. Sand-packing model and core displacement experiments showed that the oil displacement efficiency was 9.72% and 12.54%, respectively, performed with WB-001 and OPUS-HOB-001 compounding fermentation liquor injection compared with water flooding. The field trial showed that the daily oil production was increased from 0.42 t to 0.89 t, and total oil increase production was 44.47 t after microbial huff and puff process. In addition, the laboratory experiments on collecting samples showed that oil viscosity, freezing point and fluid surface tension was reduced by 11.70%, 9.41% and 18.93%, respectively. [Conclusion] This successful field trial proved that microbial enhanced oil recovery has its applicability in ultra-low permeability reservoirs and provides theoretical reference and a novel approach to high oil production of tight and ultra-low permeability reservoirs.