Experimental Study On Effect Of Calcium Carbonate Precipitation Induced By Soybean Urease On Microstructure And Mechanical Properties Of Sandstone

As a new geotechnical reinforcement technology,enzyme induced calcium carbonate precipitation remediation technology has the advantages of no bacterial involvement,no biofilm formation,small microscopic size,good injectivity,uniform distribution and small injectable size.It has potential application potential in oil and gas mining waterflood plugging seepage formation,CO₂geological storage,and improving geological conditions of water-rich sandstone.However,the cost of commodity purification urease is high,so it can not be applied in practical engineering.Based on this,in order to reduce the production cost of urease,this paper optimized the extraction technology of soybean urease,studied the catalytic reaction rule of soybean urease under different temperatures,pH and cementation concentration,and carried out the restoration test of soybean urease induced calcium carbonate precipitation of sandstone.The main research contents and achievements are as follows:（1）The experiment of preparation of low cost crude urease solution from soybean was carried out.The influence of temperature,pH and reaction solution ratio on urease activity and calcium carbonate precipitation of soybean was studied.（2）Restoration tests were carried out on coarse and fine sandstone under different times of calcium carbonate precipitation induced by soybean urease,and NMR system was used to record the changes of sandstone mesostructure before and after restoration,and the influence of The Times of calcium carbonate precipitation induced by soybean urease on the changes of sandstone mesostructure was analyzed.（3）Uniaxial compression and acoustic emission tests were carried out on coarse and fine sandstone under different repair times of calcium carbonate precipitation induced by soybean urease,and the effects of repair times on uniaxial compressive strength,elastic modulus and acoustic emission characteristics of coarse and fine sandstone were analyzed.（4）Using PFC^2Dnumerical simulation analysis software,the particle flow numerical model of sandstone specimen was established,and the mesomechanical parameters were calibrated by using the laboratory test results.The influence law of repair times on mesomechanical parameters was analyzed,and the rationality of the numerical simulation test was verified.