A cementing technology for preventing the annulus pressure of horizontal wells in JY shale gasfield

With the large-scale development of shale gas, there are more and more researches on how to improve the cementing quality of shale-gas horizontal wells. However, the sustained casing pressure of shale gas wells is not alleviated and brings severe challenges to the safe operation of shale gas fields. To solve this problem, a device for evaluating the seal integrity of cement sheath was built up. Then, the factors influencing the seal integrity of cement sheath in JY Shale Gas Field were analyzed. Finally, the cementing technology for preventing sustained casing pressure was developed correspondingly. It is indicated that poor cementation and volume shrinkage of set cement lead to early sustained casing pressure, and the damage to set cement and its cementation by staged fracturing and production parameter change is the most important reason for the sustained casing pressure of shale gas well. The cementing technology for preventing sustained casing pressure is applied and popularized in JY shale gasField. After fracturing and commissioning, the percentage of the wells with sustained casing pressure declines by 82%. This technology solves the sustained casing pressure of shale gas wells effectively, improves long-term seal integrity of cement sheath in shale gas wells.