盐下水平井YM7-H4大井眼段钻井技术

Drilling Design of Large Hole Section of Horizontal Well YM7-H4 Beneath The Salt Bed

YM7-H4井是一口盐下水平井,因盐膏层距目的层垂深约25 m,设计用311.1 mm钻头在易垮塌的吉迪克组地层进行定向,在盐膏层内一直增斜达到73.62°,直至钻穿盐膏层至井深4 770 m,然后下入273.1 mm厚壁套管封固盐膏层。该井311.1 mm井眼在钻井与中完施工过程中存在很多难点:一是吉迪克组地层泥岩严重垮塌,定向难度大;二是大井眼轨迹控制困难;三是盐膏层段长、井深、钻井液密度高达1.80 kg/L,易卡钻;四是厚壁套管直径大、刚性强、下入困难等。通过技术攻关,该井应用了大井眼轨迹控制技术、吉迪克组地层泥岩防塌钻井液技术、盐膏层钻井技术和大尺寸套管下入井眼准备技术等,顺利完成了该井大井眼段的钻井施工。

Horizontal well YM7-H4 is a typical horizontal well beneath the salt bed. The true vertical depth from salt formation to target zone is about 25 m. Orientation was made using 4311.1 mm bit in an easy collapse section called Jidik group according to drilling design. The build-up hole angle in the salt-gypsum zone reached up to 73. 62°. It passed through salt-gypsum zone to the depth of 4 770 m, and 4273. 1 mm heavy wall casing was run to ce- ment the salt formation. This paper analyzed the difficulties occurred in drilling and completion operations in φ311.1 mm well section, including the orientation in a slough mudstone interval in Jidik group, difficulties in controlling well trajectory in big hole, pipe stuck in large section of salt formation, deep depth, and with drilling fluid density up to 1.80 g/cm^3 , difficulties in running big size heavy wall casing due to its huge stiffness, etc. Through investigation and field application, four major drilling technologies were proposed, the well trajectory control in big hole, anti-slough in Jidik mudstone section with drilling fluid, drilling technology in salt-gypsum zone, well bore preparation for running big size casing. This paper will provide important reference in drilling horizontal well under salt formation.