延平1水平井煤层气绒囊钻井液实践

Application of Fuzzy-ball Drilling Fluids to Coalbed Methane Development in Yanping 1# Horizontal Well

延平1井是鄂尔多斯盆地东缘延川南区块东部平台区的第一口煤层气水平排采井,目的层为山西组2#煤层。一开采用膨润土钻井液,完钻井深140 m,下入Φ244.5 mm套管139 m;二开采用聚合物钻井液,完钻井深1 031 m,下入Φ177.8 mm套管1 030 m;三开采用绒囊钻井液以提高机械钻速、稳定井壁。煤层气绒囊钻井液由成核剂、成膜剂、囊层剂、绒毛剂等专用处理剂组成,添加KCl提高抑制性。钻井液密度1.05～1.11 g/cm3,切力2.5～8 Pa,动塑比0.35～0.85 Pa/mPa.s。10 d完成设计井深1 729.59 m,完钻井深1 732 m,顺利下入Φ114.3 mm筛管至井深1 725.4 m。三开段平均机械钻速5.09 m/h,72 h不循环井壁稳定,不影响井下信号传输,一次性与延平1-V井对接成功。完钻后通井划眼2次,后对储层段静置破胶48 h后,用清水顶替破胶液,破胶液粘度接近清水。

Yanping Well 1# is the first horizontal coalbed methane well located in the eastern platform area of Yanchuannan,Erdos Basin.The bed of interest is the 2# coal layer in Shanxi formation.Bentonite drilling fluid was used in the first spudding,with total depth of 140m and Φ244.5 mm casing down to a depth of 139 m.Polymer drilling fluid was used in the second spudding,with total depth of 1031m and Φ177.8 mm casing down to a depth of 1030 m.Fuzzy-ball drilling fluid was used in the third spudding so as to increase rate of penetration and stabilize the wellbore wall.Fuzzy-ball drilling fluid,used for coalbed methane,consists of such special disposal agents as nucleating agent,film-forming agent,capsule layer agent and fluffy agent,and potassium chloride added to it can improve inhibitive ability.The density of the drilling fluid was 1.05～1.11 g/cm3,with a shear stress of 2.5～8 Pa and a ratio of dynamic to plastic viscosity of 0.35～0.85 Pa/mPa·s.It took ten days to achieve the designed well depth of 1729.59 m.The finished drilling depth was 1732 m,with Φ114.3 mm sieve tube down to a depth of 1725.54 m.The average rate of penetration in the third spudding section was 5.09 m/h,not circular borehole wall was stable after soaked for 72 hours and signal transmission in the downhole was not affected and the third one was successfully docked with Yanping 1-V well in a single process.The well was reamed twice after well completion.The formation was held for 48 hours to make the gel breaker.Fresh water was used to replace the gel breaker and viscosity of the gel breaker was close to fresh water.