Application and Characterization Technology of Cleat in Medium-Rank Coalbed Methane

Abstract

Whether coalbed methane can be produced with high efficiency, permeability is a key parameter. However, cleats are widely distributed in the coalbed and are of great significance for coalbed permeability. Compared with high-rank and low-rank coal, the highlighted characteristic is that cleats are very developed in medium-rank coal; cleat is the endogenetic fracture system in coal, including face cleat and butt cleat, which are the main seepage channels. Cleat characterization contains the study of three cleat elements, which are cleat orientation, cleat density, and cleat permeability. Cleat density and permeability can be used to predict the potential area with high production, while cleat orientation has a great significance for the development strategy, such as optimum drilling survey designing. Through the recognization of coal reservoir in B area of A country, from qualitative description for cleat orientation to quantitative characterization for cleat orientation, density, and permeability, integrating with other parameters of coal reservoir, the potential areas were predicted and four pilot wells were designed and drilled. Testing data show that the relationship between horizontal interval and cleat orientation has a great effect on the production, and when the horizontal interval of surface to inseam (SIS) wells is perpendicular to the face cleat, the maximum production of one well is 27,700 m³/d.

Copyright 2018, Shanxi Petroleum Society.

This paper was prepared for presentation at the 2018 International Field Exploration and Development Conference in Xi’an, China, 18–20 September, 2018.

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