川东北元坝区块井身结构优化设计

Optimal Design of Casing Program in Yuanba Block,Northeastern Sichuan Basin

元坝区块是中国石化在川东北地区的重点勘探区块,由于气藏埋藏深,地质条件复杂,其钻井难度与风险极高。根据元坝区块的地质特点,针对目前井身结构存在的表层套管不能将低承压地层封固以及技术套管不能将高压层位完全封固的问题,对套管下深和套管尺寸进行优化,提出了非常规井身结构和水平井井身结构设计的优化方案,并对不同井身结构的特点进行了分析总结,认为非常规井身结构的大尺寸钻头进尺相对较小,有利于提高机械钻速,而水平井井身结构能提高元坝区块的单井产能。

Characterized by deep burial of gas reservoirs,complicated geological condition and high-risk drilling with many difficulties,Yuanba block is the key exploration one in northeastern Sichuan Basin for Sinopec.According to its geologic properties,aiming at the problems existing in casing program,i.e.the low-confined formation can’t be sealed by surface casing and theh igh-pressure horizon can’t be sealed by intermediate casing,theo ptimization for set-depth and size of casing is carried out in thiss tudy.The optimal design for unconventional and horizontal-wellc asing program has been proposed.Moreover,the properties of different casing programs are analyzed.The lesser drilling footage oft he big-size bit of unconventional casing program can raise a penetration rate.And horizontal-well casing program can increase thes ingle-well productivity of Yuanba block.