复杂构造非常规油气水平井钻井工艺研究

Research of Unconventional Oil and Gas Horizontal Wells Drilling in Complex Structure

复杂构造的地质条件通常对钻井工程时效和安全带来极大挑战,如W201-H1水平井钻井时效偏低,处理复杂情况占用时间达64%。通过对工程资料的总结以及文献调研,分析了表层井漏与储层段阻卡等复杂情况,分析高碳页岩的强度各向异性及区域性的强构造应力是造成井壁失稳和降低钻井时效的主要机理。推荐进入龙马溪组组水平段后及时提高油基钻井液密度不低于1.58g/cm^3;调整钻井液活度使之略低于原始地层水活度保证抑制性;从碱度、乳化剂用量、固控效率入手,控制钻井液PV在55~64MPa·s之间,以保证携岩清洁效果;添加粒度匹配的超细碳酸钙与可变形封堵材料,保持API滤失量在0.1ml以下,HTHP滤失量在1ml以下,封堵地层天然裂缝。以上成果认识对复杂构造下非常规油气水平井钻探具有一定指导意义。

The geological conditions of complex structures often pose great challenges to the aging and safety of drilling engineering.Well W201-H1 is the first horizontal well in China,however,the consuming time for drilling problems accounts for 64%of the whole drilling time.The main reasons of drilling problems are precipitous structure,high in-situ stresses and lack of experiences in Weiyuan structure.In this paper,the effectiveness of drilling program is statistically studied based on the comprehensive analysis of geological and engineering data.It is recommended to increase the oil-based drilling fluid density to not less than 1.58 g/cm^3 after entering the horizontal section of Longmaxi Formation;adjust the drilling fluid activity to be slightly lower than the original formation water activity to ensure inhibition;from alkalinity,emulsifier dosage Start with solid control efficiency,control the drilling fluid PV between 55 and 64 MPa·s to ensure the cleaning effect of the rock.Add the particle size matching ultra-fine calcium carbonate and deformable sealing material to keep the API fluid loss below 0.1 ml.The HTHP fluid loss is below 1ml,blocking the natural cracks in the formation.The above achievements have certain guiding significance for the horizontal well drilling in the Weiyuan structure of the basin.