离子稳定剂ENI对湘西北页岩气储层护壁机理的初探

Preliminary study on borehole wall protection mechanism of ionic stabilizer ENI for shale gas reservoir in northwestern Hunan

为研究一种离子稳定剂"ENI"对页岩气储层的护壁机理,以湘西北下寒武统牛蹄塘组炭质页岩为研究对象,通过抑制膨润土造浆试验、抑制页岩膨胀试验和抑制页岩分散试验,对比评价ENI作为钻井液关键处理剂的抑制性;通过扫描电镜试验考察ENI对炭质页岩细微结构的作用。试验表明:清水中加ENI后,膨润土造浆率降低52.41%,滚动回收率明显提高;提出的钻井液体系中,ENI钻井液作用下的页岩膨胀率最低,而滚动回收率最高,大于80%;同时,ENI生成的物质能填充孔隙,增强页岩颗粒间的连接。与所选用的其他处理剂相比,ENI具有更好的抑制炭质页岩水化膨胀、分散的效果,有助于维护井壁稳定。

A series of experiments were carried out to analyze the mechanism that a kind of ionic stabilizer named ＂ENI＂ improves wellbore stability of shale reservoirs in northwestern Hunan. Pulpification rate test of bentonite, shale hot rolling dispersion test and shale swelling rate test were employed to evaluate the inhibitive properties between ENI and other additives comparatively. Scanning electron microscope（SEM） was used to investigate the effect of ENI on the microstructure of carbonaceous shale. The test results show that ENI has excellent inhibitive properties; compared with the clear water, ENI solution decreased the pulpification rate of bentonite by 52.41%; the rolling recovery rate of the ENI solution was the highest under the action of clear water and three inhibitive solutions. Meanwhile, among the four drilling fluids formulations studied in this paper, shale swelling rate in the drilling fluid with ENI as the critical additive was the lowest, and the rolling recovery rate was higher than 80%, which was the highest. In addition, some material produced by ENI can fill tiny cracks or pores, and improve the integrity of rock. Compared with other additives studied in this paper, ENI was more effective to inhibit hydration expansion and dispersion of carbonaceous shale, and it is beneficial to maintain the wellbore stability.