Application of CO2 - MICP technology on deep water formation drilling.

Deepwater drilling faces the challenge of wellbore collapse and damage to formation stability in weakly consolidated or unconsolidated formations. The materials used in conventional geological consolidation techniques could cause the marine environment risk. Therefore, this study explored the impact of CO2 - MICP technology on formation strength and stability. The use of this combined method not only avoids environmental pollution caused by chemical materials, but also plays a certain role in CO2 sequestration. In this work, the influence of CO2 - MICP technology to improve formation strength and stability was explored, and its effectiveness was evaluated by triaxial tests, X-ray CT, etc. The results show that the Bacillus megaterium used can adapt to the high-salt environment of seawater, the CO2 - MICP technology can further enhance the strength of stratum and the mineralization of microorganisms, increasing the cohesion and friction angle of the stratum by 6.65 times and 12.13% respectively. In the presence of CO2, Bacillus megaterium accelerates the formation of carbonate ions through urease to decompose urea and carbonic anhydrase to promote the hydration of CO2, and effectively generates calcium carbonate to cement sand particles, thereby improving the stability of the stratum. In addition, the CO2 - MICP technology can also alleviate the accumulation of calcium carbonate at the entrance, increase the grouting times of treatment liquids, and further enhance the strength and stability.