强封堵高密度油基钻井液在新疆油田高探1井的应用

高探1井是2018年新疆油田的一口风险探井，位于准噶尔盆地南缘冲断带四棵树凹陷高泉东背斜构造，该井塔西河组地层存在断层、破碎带，安集海河组地层具有极强水敏性，吐谷鲁群组地层存在高压水层。钻井过程中，易出现井壁失稳、阻卡、井下复杂情况高发等难题。针对该构造的地质特点，分析采用油基钻井液钻井过程中的技术难点，提出相应的技术对策。通过实验优选出强封堵高密度油基钻井液的配方，对其性能进行实验分析评价。实验结果表明，强封堵高密度油基钻井液30 min高温高压滤失量2.8 mL，60 min高温高压滤失量2.9 mL，30 min后滤失量趋于0；对安集海河组泥岩的膨胀率为0.7%，岩屑滚动回收率为97.6%；抗10%岩屑、15%水、4%水泥、15%NaCl、3%石膏污染；在?30 ℃下，钻井液的漏斗黏度126 s、初切8 Pa、终切16 Pa。现场应用表明，强封堵高密度油基钻井液能够解决新疆准噶尔盆地南缘冲断带四棵树凹陷高泉东背斜构造地层钻井的难题，复杂事故率降至1%，钻井周期缩短50%、钻井综合成本降低50%，提质提效效果显著。建议在新疆准噶尔盆地南缘地区强水敏性地层、高地应力地层等复杂地层超深井中进一步推广应用。

Application of high-density plugging oil based drilling fluid in Well Gaotan-1 of Xinjiang Oilfield

Well Gaotan-1 is one wildcat well drilled in the Xinjiang Oilfield in 2018, and it is located at the Gaoquan east anticline of Sikeshu Sag in the thrust belt along the southern margin of the Junggar Basin. In this well, there are faults and fractured belts in the Taxihe Formation and high-pressure water layers in the Tuguluqun Formation, and Anjihaihe Formation is of extremely strong water sensitivity, so its drilling tends to suffer borehole instability, pipe sticking and frequent downhole complexities. The technical difficulties in the drilling process of oil based drilling fluid were analyzed based on the geological characteristics of Gaoquan east anticline, and the corresponding technical countermeasures were proposed. Then, the formula of the high-density plugging oil based drilling fluid was experimentally determined and its properties were experimentally analyzed and evaluated. The experimental results show that the loss of this high-density plugging oil based drilling fluid at high temperature and high pressure is 2.8 mL after 30 min, 2.9 mL after 60 min and nearly 0 after 30 min. Under the action of this drilling fluid, the expansion ratio of Anjihaihe Formation mudstone is 0.7% and its progressive cuttings recovery is 97.6%. It is resistant to 10% cuttings, 15% water, 4% cement, 15% NaCl and 3% gypsum contamination. Under the temperature of ?30 ℃, its funnel viscosity is 126 s, its initial gel is 8 Pa and final gel is 16 Pa. The field application indicates that high-density plugging oil based drilling fluid can solve the drilling difficulties at the Gaoquan east anticline of Sikeshu Sag in the thrust belt along the southern margin of the Junggar Basin, and its efficiency improvement effect is remarkable with complex accident ratio dropping to 1%, drilling cycle shortening by 50% and composite drilling cost reducing by 50%. Finally, it was suggested to apply this drilling fluid in ultra-deep wells in complex strata, e.g. those with strong water sensitivity or high ground stress along the southern margin of the Junggar Basin.