南堡2、3号构造中深层硬脆性泥岩漏失机理

冀东油田南堡2、3号构造中深层钻井液漏失问题突出,为科学认识其漏失机理,对该区块岩样开展微组构分析及理化性能测试,并结合现场统计资料分析了该区块钻井液漏失机理.研究结果表明:南堡2、3号构造中深层岩性以硬脆性泥岩为主,其水敏性不强,呈现出一定的硬脆性.岩样微裂缝发育,钻井液相沿裂缝侵入,造成岩样整体胶结强度减弱,易产生沿裂缝面的张性劈裂破坏.结合现场资料判断认为该区块漏失主要类型为张开型裂缝性漏失,钻井液侵入地层导致力学强度降低,引发水力尖劈作用而造成地层破碎,导致漏失程度增加.针对南堡2、3号构造复杂漏失原因,提出了针对不同漏失原因的应对措施.研究结果为科学认识该区块钻井液漏失机理、降低钻井成本提供了技术参考.

Analysis on the leakage mechanism of hard and brittle mudstone in Nanpu No.2 and No.3 structures

The problem of drilling fluid leakage in Nanpu No.2 and No.3 structure in Jidong Oilfield is serious. In order to understand the leakage mechanism in this area, the micro structure analysis and physical and chemical properties test of the rock samples were carried out. The mechanism of drilling fluid leakage in this filed was analyzed by combining with the field statistical data. The results show that the lithology of the layers in Nanpu No.2 and No.3 structures is mainly hard and brittle mudstone, which has weak water sensitivity and shows hard and brittle characteristics. The microfractures in the rock are developed, and the drilling fluid intrudes along the fractures, resulting in the weakening of the overall cementation strength of the rock, which is prone to tensile fracture along the fracture surface. According to the field data, the fractures in rock is the main factor of drilling fluid leakage. Drilling fluid intrudes into the formation, resulting in the decrease of mechanical strength, causing rock damage and leakage. In view of the complex leakage reasons of Nanpu No. 2 and No. 3 structures, the Countermeasures for different leakage reasons are proposed. The research results provide a technical reference for understanding the mechanism of drilling fluid leakage and reducing drilling cost.