相国寺地下储气库低压裂缝性地层钻井防漏堵漏技术

相国寺储气库是川渝地区第1座地下储气库,由枯竭型碳酸盐岩气藏改建。因构造运动和剥蚀作用,地表已出露下三叠统嘉陵江组和下二叠统茅口组石灰岩,加之二叠系和石炭系气藏已枯竭,压力系数极低,纵向上压力系统极为复杂,钻井过程中十分突出的问题就是如何控制井漏。为此,针对相国寺储气库试验井纵向上地层裂缝发育、低压的井漏难点,结合国内外防漏堵漏工艺技术,提出了如下的技术措施:①采用优化井身结构分隔不同的低压层段,以保证不同的防漏治漏措施的效果;②应用气体钻井技术快速钻过上部低压裂缝发育段;③在长兴组—茅口组钻井液井段采用HHH堵漏、雷特纤维承压堵漏来确保油层套管固井施工作业对地层承压能力的要求。实践表明,采用这些防漏堵漏技术措施不仅解决了相国寺地下储气库试验井的钻井井漏问题,而且大幅度提高了机械钻速和缩短了钻井周期,将为后续储气井防漏堵漏提供了有效的技术支撑。

Lost circulation prevention and plugging technology for test wells at low pressure fractured formations of the Xiangguosi Underground Gas Storage

Xiangguosi Gas Storage is the first underground gas storage (UGS) in Sichuan and Chongqing area, which is transformed from a depleted carbonate gas reservoir. Due to tectonic activity and erosion, the Lower Triassic Jialingjiang and the Lower Permian Maokou Fms limestones started to expose at the surface; and because of the depleted Permian and Carboniferous gas reservoirs, the formation pressure coefficient is so low and longitudinal pressure system is so complicated that the lost circulation control is the focus of drilling the test wells in constructing this underground gas storage. In view of this, combining leak protection and plugging technologies at home and abroad, we proposed the following technical measures: optimizing low pressure well intervals to ensure the final effects of different leak prevention and plugging measures; applying gas drilling technology at upper low pressure sections with fractures developed; employing the HHH plugging technology in drilling fluids at well sections in Changxing – Maokou Fms, and using the Neotoy pressure bearing plugging technology in casing cementing operation at oil bearing layers. The practice shows that those technologies can not only prevent the lost circulation in the Xianguosi test wells, but greatly improve the penetration rate and reduce the drilling cycle, which provides robust technical support for follow up similar projects.