顺北含辉绿岩超深井井身结构优化设计

Casing program optimization of ultra-deep well with diabase reservoir in Shunbei block

顺北井区采用六级井身结构开发,存在大尺寸井眼长、套管层次多以及火成岩漏失,导致钻井效率低、亟需优化井身结构。采用Drillworks软件模拟了地层三压力剖面,成像测井与电镜扫描认识了火成岩裂缝分布,通过岩石矿物成分与理化性能分析了深部泥岩坍塌机理,通过对比非标套管与钻杆的强度与尺寸分析了管柱匹配性。结果表明全井存在4个不同压力系统,火成岩裂缝纵向分布缝宽0.5-2 mm、微裂缝缝宽2-3μm,易塌泥岩伊蒙混层达70%,蒸馏水作用下线性膨胀率40%-45%,得到了3个必封点与1个风险点;通过配套钾铵基聚磺钻井液体系与漏失补救措施,保障了长裸眼井壁稳定;优选了？139.7mm非标套管,完钻井眼尺寸由114.3 mm扩大至120.65 mm满足使用非标88.9 mm钻杆,将井身结构优化为四级。新结构满足高效钻井需求,缩短钻井周期达125 d。

The six-section casing program is adopted in the Shunbei block, but it is disadvantageous with long large-size borehole, excessive casing sections and mud loss in igneous rocks, which lead to low-effcient drilling. Therefore, it is necessary to optimize the casing program. In this paper, three reservoir pressures were simulated by using the Drillworks Software. The distribution of fractures in igneous rocks was identifed by using the image logging and SEM （scanning electron microscope）. The collapse mechanisms of deep shale were investigated on the basis of its mineral composition and physical and chemical properties. The matching between non-standard casings and drilling pipes was analyzed in terms of their strength and size. It is shown that there are four pressure systems in hole. The fractures distributed vertically in igneous rocks are 0.5-2 mm wide and the microfractures are 2-3 μm wide. The illite/smectite formation accounts for 70% of caving mudstones and its linear expansion ratio in distilled water is 40%~45%. Three plugging points and one risk point were defned. The long open-hole section was stabilized by taking mud loss remedial measures with potassium ammonium polysufde drilling fuid system. The Ф139.7 mm non-standard casing was selected and the completion hole diameter was enlarged to 120.65 mm from 114.3 mm, so that the Ф88.9 mm non-standard drilling pipe could be used and the casing program was optimized into four-section mode. By virtue of the new casing program, the drilling was performed effciently, with the drilling cycle shortened by 125 d.