天然气勘探与开发2025，Vol.48Issue(3)：97-104,8.DOI:10.12055/gaskk.issn.1673-3177.2025.03.010
元坝气田超深井小井眼侧钻关键技术及其应用
Sidetracking of ultra-deep slim holes in Yuanba gas field:Key technologies and their application
摘要
Abstract
In the Yuanba gas field of northeastern Sichuan Basin,the Upper Permian Changxing Formation biogenic reef gas reservoirs are buried at depths ranging from 6300 to 7200 m,with reservoir temperatures between 149 and 164℃.The Lower Triassic Feixianguan Formation exhibits formation pressures of 118-120 MPa,with average H2S content of 4.64%and CO2 content of 5.72%.The reefs are relatively poor in reservoir connectivity,leading to incomplete gas reserve producing in some reefs.In order to improve the ultimate recovery of the gas reservoirs,sidetracking through original wellbores is employed for reservoir connection to efficiently produce the remaining reserves.Based on the analysis of engineering geological characteristics and previous drilling practices,a set of key technologies has been developed,including the casing program optimization design of sidetracked hole,low-density high-temperature-resistant acid-soluble drilling fluid,and ultra-deep slim hole trajectory control.These technologies provide effective solutions to the problems such as the co-occurrence of leakage and blowout caused by significant difference in formation pressure coefficients between the Lower Triassic Jialingjiang-Feixianguan Formations and the Upper Permian Changxing Formation,casing deformation induced by the developed gypsum salt rocks in the Jialingjiang-Feixianguan Formations,high leakage risk in low-pressure coefficient reservoirs(with a pressure coefficient of 0.6)and the difficulty of reservoir protection,and hard trajectory control of slim holes.The application of the technologies to Well YB103-1H demonstrates that,(i)the sixth spud with specialized drilling techniques for the Changxing Formation low-pressure reservoirs enables a safe well construction and also reservoir protection by reducing drilling fluid density to avoid leakage;(ii)the low-density high-temperature-resistant acid-soluble drilling fluid achieves the dual objectives of wellbore stability and reservoir protection;and(iii)the optimization of bottomhole assembly(BHA)allows for both trajectory control and sticking prevention.It is concluded that the proposed key technologies for sidetracking of ultra-deep slim holes provide not only technical guarantee for efficiently producing remaining gas reserves and enhancing ultimate recovery in this gas field,but also references for subsequent safe and efficient operations of ultra-deep slim hole sidetracking.关键词
四川盆地东北部/元坝气田/生物礁气藏/超深井/小井眼/侧钻/提高气藏采收率Key words
Northeastern Sichuan Basin/Yuanba gas field/Biogenic reef gas reservoir/Ultra-deep well/Slim hole/Sidetracking/Enhanced gas recovery引用本文复制引用
严焱诚,罗成波,郭治良,胡大梁,张生军,黄河淳,房舟,江波,任茂..元坝气田超深井小井眼侧钻关键技术及其应用[J].天然气勘探与开发,2025,48(3):97-104,8.基金项目
中国石化科技部项目(编号:P22116). （编号:P22116）
