Tectonically deformed coal types and pore structures in Puhe and Shanchahe coal mines in western Guizhou Li Ming a,b,c,⇑ , Jiang Bo a,b , Lin Shoufa a,c , Wang Jilin a,b , Ji Mingjun d , Qu Zhenghui a,b a School of Resource and Earth Science, China University of Mining & Technology, Xuzhou 221008, China b Key Laboratory of Coalbed Methane Resources and Reservoir-Forming of Ministry of Education, Xuzhou 221008, China c Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Canada N2L 3G1 d Jiangsu Hogan Group Co., Ltd., Xuzhou 221137, China article info Article history: Received 28 September 2010 Received in revised form 12 November 2010 Accepted 2 December 2010 Available online 11 June 2011 Keywords: Puhe and Shanchahe coal mines Tectonically deformed coal Pore structure Coalbed methane abstract To evaluate the effect of tectonic deformation on coal reservoir properties, we provide an analysis of the types of tectonically deformed coal, macro- and microscopic deformation and discuss pore structural characteristics and connectivity based on samples from the Puhe and Shanchahe coal mines. Our research shows that the tectonically deformed coal mostly includes cataclastic structural coal, mortar structural coal and schistose structural coal of a brittle deformation series. The major pore structures of different types of tectonically deformed coal are transitional pores and micropores. The pore volumes of macrop- ores and visible fracture pores produced by structural deformations vary over a large range and increase with the intensity of tectonic deformation. Mesopores as connecting passages develop well in schistose structural coal. According to the shapes of intrusive mercury curves, tectonically deformed coal can be divided into parallel, open and occluded types. The parallel type has poor connectivity and is relatively closed; the open type reflects uniformly developed open pores with good connectivity while the occluded type is good for coalbed methane enrichment, but has poor connectivity between pores. Ó 2011 Published by Elsevier B.V. on behalf of China University of Mining & Technology. 1. Introduction Coal is a special kind of rock that is uniquely sensitive to stress and strain. Tectonically deformed coal with various structural characteristics and types form under different stress–strain condi- tions and tectonic stresses [1,2]. The distribution of tectonically de- formed coal in a coal seam is relatively limited, but it is widely developed in China’s coal fields and is the main factor affecting the distribution and enrichment of coalbed methane (CBM) [3]. The development of tectonically deformed coal enhances the het- erogeneity and porosity of coal seams and also reduces their per- meability and mechanical strength. The feasibility of CBM exploitation and the possibility of coal and gas outbursts are signif- icantly affected by late structural transformations and pore-frac- ture structural characteristics of coal seams [4–7]. This provides a basis for further discussion of deformation characteristics and pore structures of tectonically deformed coal, necessary for further CBM exploitation, safe mining and production. The Puhe and Shanchahe coal mines are located in the west of Guizhou province, near Puding and Anshun cities (Fig. 1). They be- long to the Zhina coal field, which is located in the southwest of the Zunyi fault arch [8]. Structural traces in this zone trend mainly in a northeasterly direction. The folds are mainly gentle folds. The faults are well developed and move mainly in a normal sense. The geological structure in the Puhe and Shanchahe coal mines is relatively simple and exhibits several normal faults with a near north–south trend. The Longtan formation of the upper Permian is a major coal-bearing section in the study area, between 300 and 490 m thick, containing 10–22 coal seams. Coal seams Nos. 22, 23 and 34 are the main mineable coal seams in this coal field with anthracite rank. The semi-bright and semi-dull coals are of the dominant lithotypes, with secondary amounts of dull and bright coal. 2. Materials and methods In the Puhe and Shanchahe coal mines, the coal seams are bur- ied to a shallow depth, their geological structure is simple and the type of tectonically deformed coal is not complex [9]. Based on geological surveys of the coal mine within a limited underground mining space, different types of typical tectonic coal samples were collected, as shown in Table 1. Systematic observations and descriptions of the mesoscopic deformation features of tectonically deformed coal, including bed- ding, joint, fracture and degree of development, were made on the 1674-5264/$ - see front matter Ó 2011 Published by Elsevier B.V. on behalf of China University of Mining & Technology. doi:10.1016/j.mstc.2011.05.002 ⇑ Corresponding author. Tel.: +86 13151981375. E-mail address: cumtmingli@hotmail.com (M. Li). Mining Science and Technology (China) 21 (2011) 353–357 Contents lists available at ScienceDirect Mining Science and Technology (China) journal homepage: www.elsevier.com/locate/mstc