The poor volumetric sweep efficiency of water and invalid cycles caused by rock layer heterogeneity are major problems in crude oil production. In this study, four pairs of columns under different conditions containing different particle sizes of sand were tested to simulate heterogeneous rock layers. The results indicated that microbially induced calcium carbonate precipitation (MICP) was more durable than bioclogging (e.g., Sporosarcina pasteurii and extracellular polymeric substances (EPS)) even in the absence of a nutrient supply. The permeability reduction due to the MICP brought oil recovery improvement from about 44% to 83% in laboratory displacement experiments. Both pH and ammonium concentration slightly increased, reaching values of approximately 9.0 and 8.5 g L?1, respectively. Permeability, an effective hydraulic indicator of pore volume, decreased from 16.0 D to 0.6 D due to plugging. The nuclear magnetic resonance (NMR) transverse relaxation time (T2) curve decreased due to the filling of voids by calcium carbonate precipitation after treatment. Moreover, the ureolysis reaction was still possible at high salinity and elevated temperature (<50 °C) despite the prolonged flow diversion period. This work further emphasizes the potential application of MICP to enhanced oil recovery (EOR).
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机译：水的低体积扫描效率和由岩石层非均质性引起的无效循环是原油生产中的主要问题。在这项研究中，测试了四对在不同条件下包含不同粒径沙子的圆柱，以模拟非均质岩层。结果表明，即使在不存在微生物的情况下，微生物诱导的碳酸钙沉淀（MICP）仍比生物阻塞（ eg ， Sporosarcina pasteurii 和细胞外聚合物（EPS））更持久。营养供应。在实验室置换实验中，由于MICP导致的渗透率降低使采油率从约44％提高到83％。 pH和铵浓度均略有增加，分别达到约9.0和8.5 g L ？1 。渗透率（有效的孔隙体积水力指标）由于堵塞而从16.0 D降低至0.6D。核磁共振（NMR）横向弛豫时间（T2）曲线由于处理后碳酸钙沉淀填充空隙而减少。此外，尽管分流时间延长，但在高盐度和升高的温度（<50°C）下仍可能发生尿素分解反应。这项工作进一步强调了MICP在提高采油率（EOR）中的潜在应用。
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