莲花山构造定向井安全钻井技术

SAFETY DRILLING TECHNOLOGY FOR DIRECTIONAL WELL OF LIANHUASHAN STRUCTURE

莲花山构造位于四川盆地西部边缘,龙门山逆掩推覆带的前缘坳陷。该构造复杂,断层发育,并均为逆断层。定向点以上的表层夹关组以砂岩为主夹泥岩,地层疏松胶结不好,钻遇该层位时发生严重漏失,甚至失返等险情。在定向点以下为须家河组,在须五段为页岩和砂岩互层,夹碳质页岩及煤层,须五地层本身就易发生掉块和垮塌,该地层的地层倾角大,又为定向井,更容易引起掉块和垮塌。为此,从优化钻井参数、优选钻头、优选钻井液体系、堵漏措施、电测及下套管等方面进行研究,形成一套适合莲花山构造定向井安全钻井技术,经现场试验该技术方案效果明显。

Lianhuashan structure is situated at the frontal depression of Longmenshan overthrust nappe belt, western edge of Sichuan Basin. Some thrust faults are developed in this complex structure. Above the directional point, Jiaguan Formation is dominated by sandstone interbedded with mudstone featured by weak cementation. Serious lost circulation and no-return problems may occur while drilling. Under the directional point, Xujiahe 5 Member consists of shale interbedded with sandstone, and mixed with carbonaceous shale and coal bed. Due to large dip angle, formation collapse may occur frequently. Therefore, a methodology of safety drilling for directional well is developed according to the research on drilling parameter, bit and drilling-fluid system optimizations, plugging measures, electronic logging, and casing running. Field test shows that the methodology is obviously effective.