柴参1侧1井钻井液技术

Drilling fluid technology for Well Chaican-1-C1

柴参1侧1井是在柴参1井直井眼内侧钻出的一口井,所钻地层为泥岩层段,成岩性差且裂隙发育,地层破碎.极易水化剥落及坍塌,在井深3600 m左右有断层存在.极易发生井漏、井壁失稳及坍塌,柴参1井在钻井过程中井壁垮塌严重。柴参1侧1井通过应用聚合醇钻井液顺利钻达目的层,在钻进过程中未发生一次因井眼坍塌而引发的井下复杂及事故;与柴参1井相比,该井井径扩大率较小,大部分井段的井径扩大率都在16％左右;在钻进过程中钻井液密度控制为1.22～1.23 g/cm3,全井处于近平衡钻井状态,取全了各种资料。现场应用表明,聚合醇钻井液是一种强抑制性体系,通过优选聚合醇等各种防塌处理剂,满足了不同井深的需要;其防塌封堵性、润滑性和流变性良好,满足了柴参1侧1井的钻探要求,很好地保护了油气层。

Well Chaican-1-Cl is a sidetracked well from the vertical hole of Well Chaican-1. Long section of shale has to be drilled, and because of the poor formation integrity and highly developed fractures, hole sloughing and collapses are likely to happen due to hydration; there are fault blocks in about 3600m, and such troubles as lost circulation, hole instability and collapse are likely to take place, and serious hole collapse was encountered during the drilling of Well Chaican-1. By using the polyol drilling fluid in Well Chai-can-l-Cl, it was smoothly drilled to the target zone and no downhole troubles and accidents were encoun tered because of hole sloughing. As compared with Well Chaican-1, it had a smaller hole enlargement rate, of about 16% in large section of the hole; drilling fluid density was controlled between 1. 22-1. 23 g/cm3 during drilling, and the well was in a state of near-balanced, with various data collected. Field using showed that the polyol drilling fluid is a highly inhibitive system, and by selecting various sloughing control additives, it met the requirements of different hole depth. This drilling fluid system had such advantages as good sloughing control and plugging capability, good lubricity and rheology, and it effectively minimized the formation damages.