The South China YQ Basin, with its 15 trillion m3 of natural gas, is typical of ultrahigh-pressure/high-temperature (ultra-HP/HT) plays, with the highest bottomhole temperature (BHT) at 249°C, the maximum bottomhole pressure (BHP) at 142 MPa, and an extremely narrow pressure window. Predictably, drilling challenges in these plays are numerous. This paper discusses the successful application of managed-pressure drilling (MPD) in the basin with reduction in risks and well costs.
Overview of the YQ Basin
In recent years, approximately 27% of major oil and gas discoveries have come from HP/HT fields. The South China YQ Basin is one of the three major offshore HP/HT regions in the world and is located at the intersection of the Eurasian, Pacific, and Indo-Australian plates and has a complex geological structure.
The drilling in this basin, as is the case in any HP/HT area, faces various technical challenges, including the following:
- The temperature and pressure gradient is very high.
