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ZK001井钻遇地层为大段泥岩,部分地层为页岩、含盐泥岩、盐膏层。在泥页岩地层进行大口径全面钻进,钻速较快,固控设备能力有限,引起钻屑中粘土颗粒重复性膨胀、软化及裂解分散,最终可能造成粘土侵,对井内安全造成威胁。深部岩膏层易溶于水,从而导致盐层蠕变、井径扩大、井壁失稳等问题。以ZK001井为例,通过优化钻井液体系及现场施工工艺,解决了地层强造浆、盐层失稳等问题。通过岩石力学测试、阳离子交换容量测试、钻井液体系优选及性能测试,确定了上部地层采用聚合物钻井液体系,下部含盐层取芯钻进转换为饱和盐水钻井液体系。通过选用合适的钻井液密度、粘度、切力量、滤失量、含盐量等指标,可以有效控制上部泥岩井壁稳定、含盐层蠕变、井径扩大的问题。钻进过程中钻井液性能稳定且易于维护,从而保证了钻进工作安全、高效、顺利的进行。
ZK001 well drilled encountered large strata of mudstone, part of the formation of shale, salt mudstone, salt cream layer. Drilling large diameter boreholes in shale formations with large drilling speeds, fast drilling speed and limited ability of solid control equipment caused repeated swelling, softening and cracking of clay particles in drilling cuttings, eventually resulting in clay invasion and posing a threat to well safety. Deep rock layer soluble in water easily, resulting in salt creep, borehole diameter expansion, wall instability and other issues. Taking ZK001 well for example, the problems of strong formation of strata and instability of salt layer are solved by optimizing drilling fluid system and on-site construction technology. Through the rock mechanics test, the cation exchange capacity test, the drilling fluid system optimization and the performance test, it is confirmed that the upper strata adopts the polymer drilling fluid system, and the lower salt coring drilling converts into the saturated brine drilling fluid system. Through the selection of appropriate drilling fluid density, viscosity, shear force, fluid loss, salt content and other indicators, we can effectively control the upper mudstone wall stability, salt layer creep, borehole diameter expansion. Drilling fluid performance during drilling stable and easy to maintain, thus ensuring the drilling work safely, efficiently and smoothly.