New progress and development prospect of key technologies for drilling of deep shale gas wells in the Sichuan Basin

The Sichuan Basin is rich in shale gas resources, and at present, deep shale gas has become an important field for the increase of natural gas reserves and production in this basin. With the increasing of burial depth and the changing of structural setting, however, the geological and engineering conditions will get more complicated to bring several technical difficulties in the drilling process, such as high risk of lost circulation, failure of downhole tools at high temperature, and difficult control of horizontal well trajectory. After systematically analyzing the actual drilling data of drilled wells, this paper systematically summarizes the key technical difficulties impeding the safe, optimized and fast drilling on the basis of the geological and engineering characteristics in deep shale gas blocks. Based on this, a series of key technologies for the safe, optimized and fast drilling of deep shale gas well are formed, which mainly include geology-engineering integration guided technology, ROP improvement technology, and leakage and complex accident prevention and control technology. And the following research results are obtained. First, the geology-engineering integration guided technologies dominated by the fine geological modeling for selection of geological and engineering "dual sweet spot" and the real-time target tracking realize the accurate selection and tracking of geological targets. Second, the ROP improvement technologies dominated by the efficient rock breaking technology of "type selection of efficient PDC bit + personalized optimization + large-torque screw", the real-time optimization technology of "MSE + CCS" parameters, and the cooling of oil based drilling fluid on the ground + high-temperature rotary steering technology realize the ROP improvement in shale gas drilling. Third, the complex accident prevention and control technologies dominated by the wellbore stability evaluation, the fractured thief zone identification, and the leakage and complex accident prevention and control reduce the risks of downhole leakage and pipe sticking from the very beginning. In conclusion, the application of these technologies for the safe, optimized and fast drilling of deep shale gas well significantly improves the ROP and the platinum target drilling rate. These technologies have been popularized and applied on site in more than 200 wells. As a result, the single-well average drilling period is shortened by 42.7% and the ROP is improved significantly, which provides a powerful support for the large-scale effective development of deep shale gas. What's more, the technological researches on the drilling of deep shale gas well will focus on geology-engineering integration, one trip in one horizontal section, leakage prevention and control, and intelligent drilling decision making. © 2024 Natural Gas Industry Journal Agency. All rights reserved.