Drilling and completion fluid technology in the horizontal well drilling of the Changqing ultra-low-pressure gas storage reservoirs

The Changqing underground gas storage well is to be completed at the Shan 2 3 reservoir in the Yulin Gas Field of the Changqing gas zone, Ordos Basin. Due to the long-time production and fracturing stimulation, the pressure at the pay zone of the horizontal well is extremely low with the pressure coefficient of only 0.4 - 0.6, which becomes a geological factor leading to lost circulation when the horizontal section is drilled. Apart from that, to meet the needs of the designed work of screen liner completion, the drilling and completion fluid should have very good plugging performance. In view of this, an experimental study is conducted to find ways to avoid lost circulation and provide reservoir protection in terms of drilling and completion fluid technology, thus, a low-damage and non-clay composite salt system is developed with high inhibition, high lubricity, low solids content, and temporary plugging capability. It has been applied in 2 wells, the well Y37-2H of which was drilled and completed with a total depth of 5044 m and a horizontal section length of 1819 m, thus, a new record of the length was set up for the 0215.9 mm horizontal well drilling in the Changqing Gas Field. As a result, the 0139.7 mm liner was smoothly run to the predetermined depth without any problem. And the potential flow rate was high up to 1 million m 3 per day. This field application shows that this system can not only effectively protect the Shan 2 3 reservoir but make a safe drilling and completion job possible.