Safety Evaluation Technique of Annular Pressure in Offshore High-Temperature High-Pressure Gas Wells

The high-temperature high-pressure (HTHP) nature gas reserves in the South China Sea are 15 trillion cubic meters, accounting for approximately one-third of the total oil and gas resources in the South China Sea. There are many leak risk points of the HTHP wellbore, so it is very difficult to guarantee the wellbore integrity, and the annular pressure seriously threatens the test and construction security. Based on the safety assessment technology study of the annular pressure offshore HTHP gas fields, this paper designed the whole-life-cycle annular pressure management model and operation measures, developed the risk assessment technology of wellbore integrity, compiled the annular pressure diagnosis model, developed the calculation software of annular pressure critical control value, etc. And then, the critical control value of wellbore pressure can be calculated much more quickly and accurately for different production time, which could better manage the wellbore pressure risk and ensure the wellbore integrity. The safety assessment technology study result in the paper has been applied successfully in Yingqiong (YQ) Basin and achieved “zero” annular pressure during the on-site drilling, completion, and production operations.