海水基微生物钻井液微生物菌种优选实验研究

Experimental study on the selection of microbial strains for seawater-based drilling fluids

摘要:

在海域天然气水合物钻采过程中，受沉积物胶结程度与水合物稳定影响的储层井壁失稳问题严重制约了钻井安全与效率。研发一种兼具增强储层胶结强度和抑制水合物分解与再生特性的新型海水基钻井液体系是保障井壁稳定并实现高效钻井的关键。微生物诱导碳酸钙沉淀（MICP）技术为解决该问题提供了可资借鉴的新途径，而微生物种类作为MICP过程的关键因素，其在海水基钻井液中的生长情况，将直接影响固壁效果。因此，本文通过实验探究了在30、20、10、4 ℃的温度条件下，巴氏芽孢杆菌和巨大芽孢杆菌两种微生物在海水中的生长规律，筛选出适合构建海水基微生物钻井液体系的微生物菌种。结果表明：在海水中，巴氏芽孢杆菌产出脲酶的活性均远高于巨大芽孢杆菌，48 h内菌种浓度（OD₆₀₀）为0.583~0.926，脲酶活性可达0.77~0.88 mmol/min，对数生长期更短，最大生长速率更高，稳定期更长，故以巴氏芽孢杆菌作为海水基微生物钻井液体系的优选菌种。

Abstract:

During the drilling and extraction of gas hydrates in marine areas， the problem of reservoir wellbore instability caused by the degree of sediment cementation and the stability of hydrates severely restricts the safety and efficiency of drilling. Developing a new type of seawater-based drilling fluid system that can enhance the cementation strength of the reservoir and inhibit the decomposition and regeneration of hydrates is the key to ensuring wellbore stability and achieving efficient drilling. The microbial-induced calcium carbonate precipitation （MICP） technology provides a new reference for solving this problem， and the type of microorganisms as a key factor in the MICP process， their growth conditions in seawater-based drilling fluids will directly affect the wellbore stability. Therefore， through experiments in this paper， the growth patterns of two types of microorganisms， Bacillus pasteurii and Bacillus megaterium， in seawater at temperatures of 30， 20， 10， and 4℃ were investigated. Microbial strains suitable for constructing a seawater-based microbial drilling fluid system were selected. The results show that in seawater， the urease activity produced by Bacillus pasteurii is much higher than that of Bacillus megaterium. The bacterial concentration （OD₆₀₀） within 48 hours is 0.583~0.926， and the urease activity can reach 0.77~0.88 mmol/min. The logarithmic growth period is shorter， the maximum growth rate is higher， and the stable period is longer. Therefore， Bacillus pasteurii is selected as the preferred strain for the seawater-based microbial drilling fluid system.