东部某区块页岩井壁失稳实验研究

Experimental Research of Shale Wellbore Stability in an East Area

东部区块是国家油气发展的重点勘探区块,该区块某地层段经常因井壁失稳造成井下事故,从而影响该地区油气勘探开发进度。基于实验室室内岩石力学评价方法对该区块页岩的矿物组成、微观结构及在流体浸泡作用下力学性质变化等分别进行了实验研究;并对该区块页岩进行了物性、力学状态等方面进行了深入分析研究。建立了井下岩芯的稳定性的评价分析体系,并对现如今该地区使用的2种钻井液进行优选。实验结果表明:井下某一组段岩芯微裂缝和溶洞发育,泥浆易浸入,导致页岩理化性质发生变化的同时,力学性质也发生变化。研究发现,随着浸泡时间增加,页岩硬度变弱;成膜钻井液体系比抗高温钻井液体系影响小。

The area is the main oil and gas exploration and development blocks of China. The underground accidents were often caused by the wellbore instability in some Formation, which always influences oilfield development progress. Based on the rock mechanics evaluation method, the mineral composition, microstructure and mechanical properties and those items under immersion fluid are obtained by experiments about the shale from the area. The mechanical properties, physical properties and mechanics properties of the core are deeply analyzed for this block. Then, the evaluation analysis system about the stability of the underground core is established, which could be used for the preferred drilling fluid in this area. Experimental results are shown that the micro fissure and caverns are well developed on the cores from that formation of the area. The mud easily penetrated into the shale, which changed the physical properties, chemical properties and mechanical properties of the shale. The research also finds that the shale hardness become worse with longer the mud immersing. The film forming drilling fluid system is much better than the Anti-high temperature drilling fluid system.