Utilising Managed Pressure Drilling to Drill Shale Gas Horizontal Well in Fuling Shale Gas Field

摘要

The SINOPEC Fuling shale gas field is the first large-scale commercial development shale gas field of China, which have been built as a productivity of 5 billion shale gas field until 2015. The problems faced in this location is narrow margin between pore (or collapse)and fracture pressure, therefore the mud loss, collapsing and gas kick are very common problem encountered while drilling, the ROP decreases greatly and the cost of drilling operation increases rapidly. With falling oil and natural gas prices, greater efficiency and excellence in well construction is called for, the MPD related theoretical model and successful use of MPD techniques for improving ROP, controlling gas kick and mud loss, reducing drilling cost for the shale gas horizontal well drilling in Fuling is described. Firstly, a new utility gas kick detect method based on real-time WHP analysis through the theoretical and model analysis was established, in which the WHP variation caused by the tripping, ROP and flow rate variation were taken into account, through which the gas kick can accurately detected as soon as quickly. Secondly, for improving the pressure control precision, a three-layer feedback control method was established and programmed in the controller, through which the bottom hole pressure (BHP) can be adjusted very stable. Moreover, integrated software that combined MPD design and gas kick control simulation was developed based on which the best pressure control procedure and kick initial response can be obtained easily. The MPD technique has been applied in several wells in Fuling shale gas field of SINOPEC, based on the integrated software, the BHP, flow rate, WHP, mud density, and others drilling parameters were all obtained. And through MPD, the drilling results show that the ROP of there wells were improved about 13.9-82%, the outage time have reduced more than 60%. Moreover, through using the low-density drilling mud, the mud loss has been successfully prevented, and also reduced the mud cost. This study will presented the utility theoretical model for MPD gas kick detection, three-layer feedback pressure control method, and the MPD application in shale gas drilling. Through the application of the MPD, the results show that the ROP in shale gas horizontal well drilling has been improved obviously, the optimal oil based drilling mud density was designed has successfully prevented the mud loss and reduced the drilling cost.