A New Method for Evaluating the Characteristics of Hydration in the Longmaxi Shale Gas Reservoir in Sichuan-Chongqing Area

A new method has been introduced in order to effectively evaluate the changes in hydration characteristics of shale formations.It is also used to evaluate the reservoir hydration characteristics of Longmaxi shale in Sichuan and Chongqing area.This paper analyzes the rock fabric and physiochemical features of Longmaxi shale,showing that the conventional test methods like rolling recovery and linear expansion cannot effectively evaluate the wellbore stability in Longmaxi shale under different drilling fluid conditions.Also,this paper explains the method for evaluating rock mechanical properties based on rock depiction technique,the method for evaluating the fracture extension based on CT imaging technique and the method for evaluating the micro-fracture sealing based on pressure penetration technique,and tests were made on the cores taken from Longmaxi shale in Sichuan and Chongqing area.The tests showed that the continuous rock depiction technique could quantitatively evaluate the effect of micro shale fabric on the strength of hydrated shale.CT imaging technique could also be used to visually describe the changes in the internal micro-structure of shale.Finally,the pressure penetration method could effectively evaluate the penetration effect of shale in shale and could help select the size of shale plugging grains.The study showed that the above three methods could effectively evaluate the changes of Longmaxi shale properties after hydration and could be used as a common method for evaluating the wellbore stability in this area.