千米级弱胶结涌砂地层小口径钻探技术研究与应用

Research and application of small-diameter drilling technology for kilometer-scale weakly cemented sand-bursting strata

摘要:

针对国内小口径固体矿产岩心钻探长期存在的千米级松散地层条件下施工难以开展的技术瓶颈，以青海某矿区YZK01钻孔为工程实例，通过产学研联合攻关，形成了一套完整的小口径绳索取心钻探施工技术体系。该孔终孔深度1120 m，全孔均为弱胶结泥砂层且伴随涌水涌砂现象，创新性地提出了“泥浆回灌+分步加重”的精准控压泥浆工艺思路，通过分层段差异化设计和动态调控，将泥浆密度控制精度提高至0.02 g/cm³，泥浆胶体稳定率由原来的65%提升至98%以上；自主研发了负压抽吸清砂钻具总成，利用单向阀在打捞时形成瞬时负压，有效清除孔底细颗粒岩粉（0.75 mm以下），相比传统干抓清渣方式效率提高3倍以上；同时建立了“低速、低压、小进尺”的精细化钻进参数体系，钻压、转速和回次进尺分别控制在常规值的50%、60%和30%左右。现场应用结果表明，采用这套技术后，日均进尺从最初的3.2 m提高到24.25 m，提高了约658%，钻孔垂直度和岩心采取率等关键指标全部满足规范要求。查新报告显示，该研究成果填补了国内千米级弱胶结涌砂地层小口径钻探技术空白，对西部复杂覆盖区深部找矿具有重要的工程应用价值。

Abstract:

Aiming at the long-term technical bottleneck of difficult construction of small-diameter core drilling for solid mineral resources in kilometer-scale loose strata in China， this study takes the YZK01 borehole in a mining area of Qinghai Province as the engineering example. Through industry-university-research collaborative study， a complete set of small-diameter wireline coring drilling construction technology system is established. The borehole reaches a final depth of 1120 m， and the entire hole section consists of weakly cemented mud-sand strata with continuous water and sand bursting phenomena. An innovative precise pressure-controlled drilling fluid technology of "drilling fluid recharge + stepwise weighting" is proposed. Through differentiated layered design and dynamic regulation， the control accuracy of drilling fluid density is improved to 0.02 g/cm³， and the drilling fluid colloidal stability rate is increased from 65% to more than 98%. A self-developed negative pressure sand cleaning drilling tool assembly is adopted， which forms instantaneous negative pressure through a one-way valve during fishing operations to effectively remove fine-grained rock powder （less than 0.75 mm） at the bottom hole， with the cleaning efficiency more than three times higher than that of the traditional dry grabbing deslagging method. Meanwhile， a refined drilling parameter system characterized by "low speed， low pressure and small footage" is established， in which the weight on bit， rotational speed and run footage are controlled at approximately 50%， 60% and 30% of the conventional values， respectively. Field application results show that the average daily drilling footage is increased from the initial 3.2 m to 24.25 m， increased by about 658%. All key indicators including borehole verticality and core recovery rate meet the specification requirements. The novelty search report verifies that the research results fill the domestic technical gap of small-diameter drilling in kilometer-scale weakly cemented sand-bursting strata， and possess important engineering application value for deep mineral exploration in complex overburden areas of western China.