摘要
CCSD-SK2井是一口钻穿松辽盆地白垩纪陆相沉积地层的中国大陆科学钻探井。二开段先以216mm口径钻至2806.20m,然后进行444.5mm口径扩孔。泥页岩地层大井眼钻进过程中粘土矿物含量高且易造浆,砂砾岩层渗透性强易粘卡,井壁稳定控制与钻屑携带难度大。选用了钾铵聚合物钻井液体系和聚磺钻井液体系,通过正交实验确定了钻井液配方。将钻井液控制在合适的密度、较低的失水量以及较强的封堵性,有效实现了井壁稳定;保持适当的环空返速、较高的动塑比以及定期打稠塞举砂等措施,有效实现了井眼净化。1086.45m~1147.56m与1182.74m~1256.01m井段累计收获岩心130.90m,取心率达到97.41%,平均机械钻速为0.84m/h;最终顺利钻至2806.20m。
The well CCSD- SK2 is the main borehole of the China Scientific Drilling Project in the Songliao basin which is designed to penetrate Cretaceous strata. The second section of this well was drilled to 2806. 20 m with 216 mm diameter,and then the diameter of the hole was expanded to 444.5mm. During drilling,high- content of clay can result in mud in the shale formation and sticking often occurs when drilling to sandy conglomerate with strong permeability. Besides,borehole stability and cutting transportation are difficult to be controlled. To solve these problems,a polymer drilling fluid system and polysulfonate drilling fluid system were employed. The drilling fluid formulation was confirmed through an orthogonal test. Measures were taken to ensure borehole stability,such as maintaining proper density,controlling low fluid loss and strong plugging capacity. Hole cleaning and stability were realized by maintaining a proper annular velocity and high dynamic- plastic ratio. Cores of 130. 90 m were recovered in the interval of 1086. 45 m ~ 1147.56 m and 1182. 74 m ~ 1256. 01 m,respectively,and the core recovery is nearly 97. 41%. Finally,the second section of this well was drilled down to2806. 20 m as designed successfully.