油藏嗜热菌与膨润土的相互作用及其对储层防膨的意义

Effect of interaction between pristine thermophilic bacteria and bentonite on anti-swelling of oil reservoir

【目的】本文从胜利油田沾3区块的高温油藏的原油采出液中分离得到一株嗜热菌,通过其与膨润土的相互作用,尝试探讨油藏微生物作为油藏储层中水敏性矿物(如蒙皂石)改性剂的可能性。【意义】研究结果将在降低水敏矿物的膨胀性能,为解决水驱采油中遇到的水敏效应的瓶颈问题提供微生物的新途径。【结果】所得菌株为革兰氏阳性菌,呈杆状,具芽孢,兼性厌氧,鉴定为Geobacillus icigianus SL-1。菌株SL-1在厌氧条件下能够还原蒙皂石的结构铁。扫描电镜(SEM)结果显示,无菌对照体系中,蒙皂石呈不规则薄片状。而经微生物作用后,除薄片状蒙皂石外,另有板状次生矿物的生成。进一步能谱(EDS)分析表明,与薄片状蒙皂石相比,板状矿物含有较高的Al/Si比值,且含有明显的K^+信号。XRD结果显示,经过微生物作用后,固相物质中蒙皂石的百分比下降至47.7%,伊利石百分比上升至29.1%,而无菌对照组中蒙皂石的百分含量则为70.4%,伊利石的百分比则为19.8%。XRD物相分析和EDS结果均证实经过微生物作用后,部分蒙皂石转化成了伊利石。膨胀性能的分析进一步揭示菌株SL-1作用后,矿物膨胀性较初始矿物显著降低,缩膨率达到25.9%。以上结果为油藏储层防膨提供了重要的实验依据。

[Objective] To decrease the swelling of water-sensitive minerals via microorganisms in oil reservoir, one thermophilic bacterial strain was isolated from a high-temperature reservoir in the Zhan 3 block of the Shengli Oilfield. Further experiments were conducted to evaluate the interaction between this isolate and bentonite with smectite as the main mineral.[Results] The isolated strain was thermophilic, facultative anaerobic, Gram-positive, and rod-shaped. It could form spores and was identified as Geobacillus icigianus SL-1 via 16S rRNA sequencing. It could reduce structural Fe(Ⅲ) of smectite under anaerobic conditions. Scanning electron microscopy results showed that smectite was irregularly flaky before the experiments, whereas slab-like particles were observed after the experiments with the presence of SL-1, suggesting the formation of secondary minerals. The energy spectrum analysis showed higher Al/Si ratios were detected in the platy minerals and much stronger peaks for K^+ than those in thin smectites. The percentage of smectite in biotic systems decreased significantly (47.7%) in comparison of those in abiotic systems (70.4%) at the end of experiments as indicated by the X-Ray Diffraction (XRD) analysis. Collectively XRD and Energy Dispersive Spectrometer (EDS) results confirmed the transformation of smectite to illite in the biotic systems, which reduce the mineral swelling property by 25.9%.[Significance] These results confirm that pristine bacteria in oil reservoir can play an important role in mineral transformation, subsequently decreasing the swelling properties of clay minerals. Therefore, our results offer a promising way to deal with the water-sensitive issues in oil recovery process.