Structure and hardness characteristics of the filter cake-coal wall interface near a CBM well and its engineering significance

被引：0
|
作者：
Chen L. [1 ,2 ]
Wang S. [2 ,3 ]
Zhang D. [2 ]
机构：
[1] School of Mining and Technology, Inner Mongolia University of Technology, Hohhot, 010051, Inner Mongolia
[2] State Key Laboratory of Coal and CBM Co-mining, Jincheng Anthracite Mining Group, Jincheng, 048012, Shanxi
[3] Faculty of Earth Resources, China University of Geosciences - Wuhan, Wuhan, 430074, Hubei
来源：
Natural Gas Industry | 2020年 / 40卷 / 06期
关键词：
CBM well; Filter cake of drilling and completion fluid; Hardness; Hydraulic fracture propagation; Indentation method test; Interfacial mechanical property; Interfacial zone structure; Near-wellbore coal wall;
D O I：
10.3787/j.issn.1000-0976.2020.06.010
中图分类号：
学科分类号：
摘要：
The filter cake-coal wall interfacial structure formed with the invasion of drilling and completion fluid near a coalbed methane (CBM) well plays a complex restriction role in the initiation and propagation of hydraulic fractures. The structure and mechanical property of the filter cake-coal wall interface and its controlling mechanism on the initiation and propagation of hydraulic fractures were considered by analyzing the key factors restricting hydraulic facture propagation, e.g., combination mode, interfacial connection structure and interfacial mechanical property of the filter cake-coal wall interface near a CBM well, using coal mine observation, interfacial zone microstructure SEM and EDS analysis, mineral XRD test and indentation method test. These analyzes showed that the filter cake-coal wall interface near a CBM well is mainly classified into two types, including the coal-cementing cement filter cake interface and the cementing cement filter cake-filter cake of drilling and completion fluid-coal interface, wherein the first one is much tighter. These two types of filter cake-coal wall interfaces are basically constant in the physical and chemical properties of base materials and have clear interfaces and distinct boundaries, thus both of them are inactive contact interfaces. The indentation method test results revelaed that the Vickers hardness of the material in the coal-cementing cement filter cake interface follows the law of cementing cement filter cake > coal > connection interface, while that of the cementing cement filter cake-filter cake of drilling and completion fluid-coal interface is cementing cement filter cake > filter cake of drilling and completion mud > connection interface. The samples collected on site during the coal mine observation verify that during hydraulic fracturing, hydraulic fractures firstly break through the interface of coal-filter cake of drilling and completion fluid.
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页码：100 / 106
页数：6
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