川南页岩气地层油基钻井液技术难题及案例分析

随着川南页岩气产区开发力度不断加大,钻井过程中长水平段起钻倒划眼、卡钻以及井漏等复杂事故已成为严重制约页岩气开发效率提升的拦路虎。对龙马溪页岩地层的地质特征、孔缝分布情况进行了总结分析,系统阐述了页岩地层微孔缝封堵、钻井液流变性控制、水平段润滑防卡、钻井液密度优化、钻井液低密度固相控制以及油基钻井液防漏堵漏等油基钻井液技术难题。最后,通过对典型案例分析,对系列页岩气地层油基钻井液技术难题进行了详细展示,并指出合理的钻井液施工密度、良好的流变性与携岩能力以及适当的工程措施等对预防井漏、保障井下安全具有重要支撑作用。

Technical Difficulties and Case Study of Oil Base Drilling Fluid Operation in Shale Gas Drilling in South Sichuan

Shale gas drilling in the south of Sichuan Province has been faced with downhole troubles such as back reaming during POOH in long horizontal section, pipe sticking and mud losses etc. This paper summarizes and analyzes the geological nature and pore and fracture distributions of the Longmaxi shale formation. Technical concerns as to the use of oil base muds are illustrated in this paper, such as plugging of micro fissures in shales, mud rheology control, lubricity of mud in horizontal section to prevent pipe sticking, optimization of mud density, control of low density solids, as well as the prevention and control of mud losses. By analyzing some typical cases, technical challenges as to the use of oil base muds in shale gas drilling are detailed. It is pointed that proper mud density, good mud rheology, good cuttings carrying capacity as well as practical engineering measures play important roles in preventing mud losses and in ensuring downhole safety.