Study on the Corrosion Pattern and Mechanism of Cement in High Temperature and High CO2 Environment in Yingqiong Basin
Due to the high CO2 content in high-pressure sections of some wells in Yingqiong Basin,the strength degradation of cement sheath and the mechanism of strength reduction of cement caused by CO2 corrosion are not clear under the condition of high temperature and high CO2 content,the effects of corrosion time,temperature,pressure and CO2 partial pressure on the corrosion of cement were analyzed by experimental method,and the corrosion mechanism was analyzed.The results show that with the increase of corrosion time,temperature,CO2 partial pressure and formation pressure,the corrosion depth of cement increases,while the compressive strength decreases.The main reason for this phenomenon is that CO2 dissolved in water corrodes tobermorite and xonorite in cement,generating calcium bicarbonate which is easily soluble in moist CO2 environment,so that the porosity and permeability of cement increase and the strength decrease.This study provides a basis for the selection and improvement of cement slurry system for subsequent high temperature and high pressure wells.
cementhigh temperaturehigh CO2 contentcrystal transformationcalcium carbonate
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