微生物对裂隙岩样渗透系数的影响

Study on Permeability of Cracked Rock Filled by Microbial Carbonate Precipitation

选取球形芽孢杆菌单独、与原油共混以及与铜绿假单胞菌共同作用下对裂隙岩样渗透系数的影响,研究了该细菌在不同条件下的生长和沉积特性。以乙酸钙为钙源及5种钙离子浓度对细菌诱导碳酸钙沉积率的影响,优选出最佳沉积条件。采用菌液注射法对岩样裂隙进行充填实验。结果表明,水压在0.2~0.6 MPa时,球形芽孢杆菌单独诱导Ca^2+沉积作用30 d后,岩样渗透系数可下降56%~78%;原油存在条件下,球形芽孢杆菌诱导Ca^2+沉积相同时间,岩石渗透系数下降30%左右,表明原油对球形芽孢杆菌诱导Ca^2+沉积具有一定的抑制作用;球形芽孢杆菌与铜绿假单胞菌同时作用下,裂隙岩石渗透系数降低30%~60%,即两种细菌同时作用的充填效果低于单一细菌作用时的填充效果。微观测试结果表明,细菌诱导碳酸钙沉积物为团簇状的絮状物,由方解石和球文石组成。

Influence of spherical bacillus,coupling together with crude oil and pseudomonas aeruginosa on permeability of cracked rock was investigated.Firstly,the growth and deposition characteristics of two kinds of bacteria were explored,the effects of 5 calcium ion concentrations of calcium acetate on rate of deposition were carried out to optimize the deposition condition.Then,the experiment of filling the fissures with bacterial fluid injection method was carried out.The results show that when water pressure changes within 0.2~0.6 MPa,spherical bacillus alone induced Ca^2+deposition for 30 days,the permeability coefficient of cracked rock can decrease to 56%~78%.In the presence of crude oil,the rate of descent of the permeability coefficient of cracked rock is about 30%using spherical bacillus induced Ca^2+deposition for 30 days,the results indicate that crude oil inhibits microbial carbonate precipitation.The combined actions of spherical bacillus and pseudomonas aeruginosa cause the 30%~60%decline of the permeability coefficient,the effect is lower than that of spherical bacillus alone.The microscopic test results show the deposition is flocculent mass composed by calcite and vaterite.