CB251E-P1井钻井液技术

Drilling fluid technology of well CB251E-P1

CB2 5 1E P1井是胜利油田在渤海海域埕北断裂带北部埕北断层下降盘CB2 5 1E断块上的一口大位移水平井 ,也是胜利油田在海上开发馆陶组上段 1+2 3 油层的第一口水平井 ,完钻井深为 2 0 5 6m ,在井深 15 9.5 2m开始造斜 ,钻至井深 6 2 4 .84m后井斜达到 4 5°,最大井斜角为 96 .3° ,水平位移为 132 6 .2 0m ,水平段长 35 6m ,连续钻遇油层 2 0 4m ,创造埕岛油田连续钻遇油层最长记录。根据地质特点 ,全井要求钻井液密度控制在 1.10g/cm3 以内。为了满足CB2 5 1E P1井安全钻井、油层保护和海洋环境保护的需要 ,采用了改性天然高分子钻井液体系及其维护处理技术。该钻井液本身无毒、无害、无荧光 ,且加入了屏蔽暂堵剂 ,有利于发现和保护油气层。结果表明 ,该体系具有良好的抑制性、润滑性和降滤失能力 ,井眼清洁 ,无岩屑床形成 ,满足了水平井施工的要求。该井钻井施工时间仅用 9.4 8d ,建井周期 15 .86d ,是海上水平井难度最大但完成时间最短的一口井。

Well CB251E-P1 is an extended reach well, situated on CB251E Faulted Block of Chengbei Fracture Belt in Bohai area. It is also the first horizontal well to explore the upper 1+23 of Guantao formation by Shengli Oilfield. TD of this well is 2056 m, and it was kicked off at 159.52 m MD, and directionally drilled to 624.84 m MD. The drift azimuth is 45°, the maximum deviation is 96.3°, the horizontal displacement is 1326.20 m, and the horizontal section is 356 m. The oil pool continuously drilled through is 204 m, which is the longest in Chengbei Oilfield. According to geological charac teristics of the well, drilling fluid density is required not to surpass 1.0 g/cm 3. To satisfy the requirements of safe drilling, oil formation protection and ocean environment protection, a modified natural high molecule polymer drilling fluid and relevant maintenance technology were employed, The fluid exhibits no toxic to the marine environment, no damage to formation, no fluorescence to geological logging. With shielding and temporary plugging agent added in, the fluid is benefitable to find and protect oil reservoir. Application in CB251E-P1verified that the fluid system has excellent inhibiting, lubricating and filtrate-reducing ability. The hole was clean with no cuttings-bed forming. The well was drilled in 9.48 d, and the construction period was only 15.86 d, and it was drilled with the shortest time and the most difficulties in offshore horizontal well drilling.