Coalbed methane resources and reservoir characteristics of ...197099/UQ197099_OA.pdf · ENERGY...

ENERGY EXPLORATION & EXPLOITATION · Volume 27 · Number 5 · 2009 pp. 307-331 307

Coalbed methane resources and reservoir characteristicsof NO. II1 coal seam in the Jiaozuo coalfield, China

Xiaodong Zhang 1*, Yanhao Liu1, Geoff Wang2 and Hao Liu1

1 College of Resources & Environment, Henan Polytechnic University, Jiaozuo 454000, China2 School of Chemical Engineering, the University of Queensland, Brisbane, 4072, Australia

* Author for corresponding. E-mail: [email protected]

(Received 2 September 2009; accepted 26 October 2009)

AbstractJiaozuo coalfield is located in the northwest of Henan province, China, andclose to the Southern Qinshui coal basin, the most successfully commercialCBM resource developed area in China. The No. II1 coal seam is the maineconomic coal seam in Jiaozuo coalfield and its average thickness exceeds5.36m. The maximum reflectance of vitrinite (RO,max) of the No. II1 coal acrossthe Jiaozuo is between 3.16% and 4.78%. The coalbody structure of the No. II1

coal seam changes greatly in different part and can be generally divided into 1~3sub-layers. The micropores in the No.II1 coal seam is the major pores, secondlyare transitional pores, and then less macropores and mesopores. The No. II1 coalseam has stronger adsorption, and the reservoir natural permeability has anevident heterogeneity vary from 0.0001 to 83.71mD. High permeability regionis often near fault structure or the boundary of fault block. The CBM genetictype is homologous thermal cracking gas of humic coal with high matunity. Gascontent with the burial depth of 163~1070m varies very greatly from 4.65 to45.75m3/t, with an average value of 18.3m3/t, and gradually increases fromnortheast to southwest. According to the latest evaluation for CBM resource inJiaozuo coalfield, the existing total in-place CBM resources in the No. II1 coalseam with the depth of shallower than 2000 m are close to 1.2 × 1012m3, mostof them mainly distribute in the depth of 1000 ~ 1500 m. The existing total in-place CBM resources is dominated by the inferred CBM resource reserves(more than 70%), which distribute the undrilled places with few coal geologicalknowledge and deeper than 1000m. The resource concentration of the No. II1

coal seam in Jiaozuo coalfield is in the range of (0.513–3.478)×108 m3/km2, withan average value of 1.805×108 m3/km2. Based on the CBM resourceinvestigation and reservoir evaluation, the most prospective target zones forCBM production in Jiaozuo coalfield include Guhanshan coal mine, Jiulishancoal mine and the west part of Qiangnan coal district.

Keywords: Coalbed methane, Jiaozuo coalfield, reservoir characteristics, CBMresource assessment

1. INTRODUCTIONCoal is a source, reservoir and trap for significant quantities of methane and minoramounts of other gases (Bustin and Clarkson, 1998). Coalbed methane(CBM) mainlyoccurs in the coal seam and its surrounding rock, and its make-up is primarily methane,with minor amounts of heavier hydrocarbons, carbon dioxide, nitrogen, oxygen,hydrogen, and helium. Because of its explosive and outburst hazard during the mining,the gas was recognized as harmful gases and directly emitted into atmosphere,contributing to the greenhouse effect. It has generally been overlooked as an economicresource mainly used as unconventional natural gas by the oil and gas industry sincethe 1970s, when CBM got its start in Pennsylvania with the drilling of degasificationholes prior to mining (Antonette and Markowski, 1998). Commercial utilization ofthese resources is mostly limited to basins where enough knowledge and experience aswell as adequate reservoir properties exist (Karacan and Okandan, 2001).

China has abundant coal and CBM resources. According to the newest oil and gasresource assessment by Ministry of Land and Resources in 2008, the CBM resource ismore than 10.9×1012m3 (shallower than 1500m) and 36.8×1012m3 (shallower than2000m) in China (Li et al, 2009). That is to say, more CBM resource exists in the depthbetween 1500-2000 m in China, which makes the CBM development more different.With the development of geological research and exploration technology, more CBMresources have achieved commercial development in different coalfields, where thecoal ranks are even different. for example, Jincheng Coalfield, located in Southeast ofQinshui basin, Shanxi Province, China, the coal classification being anthracite coal,having the largest drainage well groups in China and more than 500000 m3/d CBMproduction, has been the first basin to be developed commercially in China.

Jiaozuo coalfield is situated in the northwest of Henan province, China, and adjoinsto Jincheng Coalfield separated by Taihang Mountain. The coalfield is 60-km long (E-W) and 15-km wide (N-S), with a total area of 970km2. It is one of most importanthigh-quality anthracite producing mines in China. Many estimations about the CBMresources have been done since 1970s in Jiaozuo coalfield, and the potential gasresources have been estimated from 1100×108m3 (shallower than 2000 m, deeper thanthe weathered zone, and with a gas content >4m3/t) to more than 1733×108m3

(shallower than 2000 m) (Ye et al., 1998; Zhang et al., 2002). The latest estimation byDepartment of Land and Resources of Henan Province in 2007 shows the total CBMresource of No. II1 coal seam (shallower than 2000 m, deeper than the weathered zone,and with a gas content >8m3/t) was more than 1184×108m3 and the resourcesabundance near to 1.3×108m3/km2 in Jiaozuo coalfield, indicating a very favorablepromise for CBM exploration and development. In addition, Jiaozuo coalfield is oneof most serious areas of coal and gas outburst accidents in China. A total of 276 coaland gas outburst accidents occurred in 11 pairs Out of the 13 pairs of mines from 1955to 2000 (Zhang et al., 2008). Moreover, there is an increasing tendency of coal and gasoutburst with the increasing of the mining depth.

In Jiaozuo coalfield, there are near 1000 coal exploration bores and approximately42 CBM wells identified as being drilling prior to the end of 2008 and manyinvestigations have been published on the geology of CBM reservoir in Jiaozuocoalfield (Qin et al., 1990; Zhang et al., 1998; Meng and Peng, 1998; Song and Meng,

308 Coalbed methane resources and reservoir characteristics of NO. II1 coal seamin the Jiaozuo coalfield, China

2002; Yan, 2003; Yuan, 2005; Zhang, 2007; Gao and Wang, 2008), so manygeological data is available for evaluating the characteristic of coal reservoir and withthe progress of the old coal mine depth and increase of new coal mines, more and moredata will be available. In the paper, coal geology and CBM reservoir properties of theNo. II1 coal seam in the study area were comprehensively studied. The CBM resourcesin-place were calculated and prospective areas of CBM resources recovery wereplotted out. This paper aims to be a guide to the further exploration and developmentof CBM in Jiaozuo coalfield.

2. GEOLOGICAL SETTING2.1. Regional tectonics and formationJiaozuo coalfield lies in the south of late Paleozoic North China coal-accumulatingBasin. According to unit of tectonics dividing, it’s also at the south margin of Taihangfault-uplift zone of Taihang tectonic region in North China plate. There are widelyvarious structural features formed since Yanshanial Movement within the study area.Relatively, fault structures, including regional and small faults, developed very muchin the field, but folds develop very weak and only several widely slow folds spread onthe eastern part and southern part of the coalfield. Fault structures are mainly high-angle normal faults in the study area. The whole coalfield is divided into two tectoniczones by Phoenix fault, which is near EW strike. The south zone is latitudinal tectonicbelt, where the main structure features are near EW fractures and the near EW-axisfolds. The north part is New Nathaysian tectonic belt where mainly structural featureis near NE fracture, followed by NW fracture and rarely NNE fractures (Fig. 1).

Figure 1. Location map of Jiaozuo coalfield in China and the structure contour mapof the floor of the No. II1 coal seam.

ENERGY EXPLORATION & EXPLOITATION · Volume 27 · Number 5 · 2009 309

The strata, in order of geologic time, are Archean, Jixian System ofMesoproterozoic, Cambrian and Ordovician System of Lower Paleozoic,Carboniferous and Permian System of Upper Paleozoic, Triassic System of Mesozoic,Neogene and Quaternary System of Cenozoic (Dai et al., 2002, 2003, 2006).Generally, the strata is a monoclinic structure which strikes NE-NNE, dips to SE anddip angle changes from 5° to 20° controlled by region structure.

2.2. Coal-bearing formation and coal distributionThe North China Craton basin was eroded from Silurian to Mississippian time butsubsided and received sediment from Pennsylvanian to Triassic time. The coal-bearingformation includes Pennsylvanian Benxi and Taiyuan Formation, the Permian Shanxi,Xiashihezi and Shangshihezi, of which the Taiyuan and Shanxi formation areaveragely 170m thick and main coal-bearing units (Dai et al., 2006; Sun et al., 2002;Sun, 2003; Sun and Horsfield, 2005).

There are 15 coal-bearing formations in the study area, and average total coalthickness is about 16m. Two coal seams, including No. II1 coal seam of the Shanxiunit, No. I2 seam of the Taiyuan unit, are minable within Jiaozuo coalfield, of whichthe No. II1 coal seam develops the most widely and stably with a thickness from 0 mto 19.64 m and an average thickness of 5.36 m and is the main economic coal seam.The No. I2 seam is partially minable with thickness is from 0 m to 5.14 m and withaverage thickness of 1.34 m, which is minable in south and west part of the coalfield.Generally, the depth of the No. I2 seam is about 100 m deeper than that of the No. II1

coal seam (Fig. 2).Many researches in China reveal that there are great differences in coal body

structure under different stress and structure setting and put forward manyclassification of coalbody structure (Yuan, 1985; Jiang et al., 2004; Ju et al., 2005).According to coal morphological appearance and coalbody destruction degree, Yuan etal. divided coal into four primary constructional coal (also named undeformed coal),cataclastic coal, granular coal and mylonitic coal, of which the former two are oftencalled hard coal and the latter soft coal (Yuan, 1985) and the classification is generallyrecognized in China. By the coal profile observation under all mines within Jiaozuocoalfield, coalbed structures show regular change.

In the middle part of the coalfield, the coal seam shows different coalbody structurewith the Jiulishan fault and Beibei fault as the border. Coalbed structure can beclassified into three sub-layers in southwest part of Jiulishan fault: The top is myloniticcoal sub-layer with nearly 0.3 m~1.0 m thick, the middle is a massive undeformed coalsub-layer with 3.0 m~4.5 m thick and the bottom is mylonitic coal or granular coal sub-layer with 0.25~1.5 m thick. Between the northeast part of Jiulishan fault and the eastpart of Beibei fault, mylonitic coal is main coal body structure, followed by granularcoal and then small lump hard coal.

In the west part of the coalfield, including the part between in the northeast ofJiulishan fault and the west part of Beibei fault, the coalbed structure can be generallydivided into two layers: The top coal seam widely develops a mylonitic coal seam beltwith 0.5 m to 2 m thickness and the low part does undeformed coal seam belt withabout 3~4m thick.


In the east part of this coalfield, the coalbody only show slightly deformed and thereare dominated by undeformed coal, and then rare mylonitic coal or granular coal.

Figure 2. Stragraphic column of the Permo- Carboniferous coal-bearing sequence inJiaozuo coalfield.


3. EXPERIMENTAL METHOD3.1. Coal sampleIn this study, a total of 47 fresh samples of the No. II1 coal seam were investigated from10 underground mines in Jiaozuo coalfields, of which 17 samples can be chosen asmeasured ones in this study (see Table 1. for sampling locations). Except FangzhuangCoalmine, Baizhuang Coalmine and Xiaoma Coalmine, two coal samples includingone undeformed coal and one mylonitic coal could be chosen each coal mine in theother coalmines. Most of the selected undeformed coals were big blocks with a weightof about 8 kg each, some of which can be applied to the permeability testing. All thesamples were collected following the Chinese Standard Method GB/T 19222-2003,carefully packed and immediately carried to the laboratory for testing. For the samplesused for permeability testing, the original occurrences were recorded and tagged.

Table 1. The position of coal samples and their petrographic constituent,proximate and ultimate analyses, and coalbody structure types in Jiaozuo

coalfield.

Abbreviations: V, I, MM are the percentage content of vitrinite, inertinite and mineralmatter (vol.%), respectively; Cdaf, Hdaf, Odaf are the percentage content of Carbon,Hydrogen and Oxygen (%, dry ash-free basis), respectively; Mad is the moisturecontent (vol. %, air dried basis), Ad is ash yield (vol. %, air dried base), Vdaf(%) is thevolatile matter content (vol. %, dry ash-free basis); ARD is apparent of coal samples(103kg/m3); BDS denotes the coalbody structure type, U is undeformed coal and M ismylonitic coal.

No Coalmine Rmax V I MM Cdaf Hdaf Odaf Mad Ad Vdaf ARD BDS

G-1 Guhanshan 3.413 72.1 22.8 5.1 93.2 3.1 2.16 2.68 7.99 7.1 1.46 M

G-2 Guhanshan 3.391 48.3 40.3 11.4 94.61 3.21 0.53 1.81 10.47 9.44 1.49 U

J-1 Jiulishan 3.542 38.7 52.4 8.9 93.51 3.14 1.87 1.92 9.17 6.2 1.47 U

J-2 Jiulishan 3.609 58.6 35.6 5.8 93.59 2.99 1.98 2.52 9.82 6.54 1.48 M

Y-1 Yanma 3.553 62 31.9 6.1 92.94 3.2 2.53 2.4 12.28 6.9 1.49 M

Y-2 Yanma 3.401 45.2 40.7 14.1 93.71 3.34 1.48 1.96 13.2 7.33 1.49 U

Z-1 Zhongma 3.569 57.8 33 9.2 93.03 3.43 2.19 2.88 17.57 7.04 1.53 M

Z-2 Zhongma 3.627 57 33.3 9.7 93.69 3.15 1.55 2.38 9.22 6.74 1.49 U

H-1 Hanwang 3.658 41.2 47.5 11.3 93.39 2.95 2.36 2.28 14.74 6.81 1.53 M

H-2 Hanwang 3.742 42.1 48.1 9.8 94.64 2.99 0.89 2.2 8.67 6.54 1.49 U

F-1 Fengying 3.511 60.9 34.1 5 94.02 3.08 1.44 1.96 5.55 6.17 1.42 M

F-2 Fengying 3.498 49 36.3 14.7 94.19 3.21 0.99 2.1 13.67 8.1 1.51 U

FZ-1 Fangzhuang 3.562 58.8 32.9 8.3 94.18 3.23 0.71 1.9 7.15 6.99 1.45 U

Bai Baizhuang 3.55 37 51.2 11.8 93.57 3.47 1.47 1.52 8.23 6.74 1.44 U

ZC-1 Zhucun 3.98 32 53.3 14.7 94.47 2.71 1.33 2.1 11.23 4.88 1.54 M

ZC-2 Zhucun 3.81 59 32.9 8.1 94.35 2.48 1.8 1.89 7.2 4.36 1.53 U

X-1 Xiaoma 3.89 52.1 31.6 16.3 94.55 3.02 0.64 1.98 13.59 7.18 1.53 U


3.2. Experiments3.2.1. Conventional testIn this study, ultimate analysis (by GB/T 476-2001) was applied to measure thecontents of main elements, including carbon, hydrogen, oxygen, and proximateanalysis (by GB/T 212-2001) includes four tests for: ash, volatile matter, fixed carbonand moisture of the 17 samples (Table 1).

Vitrinite reflectance and coal maceral composition of these samples were performedunder a Leitz Laborlxe 12 POL microscope. The two testing was done by GB/T6948-1998 and GB/T15588-2001(Table 1), respectively.

3.2.2. Pore structure testMercury injection experiment (by Sy/T 5346-2005) was done to test the pore structureparameters, including pore volume, pore specific surface area and pore size of thesamples. The experiment device model is No 9310 manufactured by MicromeriticsInstrument Corp, in the USA. Its working pressure range is 0.0035 ~ 206.843 MPa,resolution 0.1 mm3, Dilatometer volume of powder 5.1669 cm3, and lower pore-radiuslimit of 7.2nm.

In the study, all the samples must be dried at 106°C for 24h before the testing andthe usage is about 3g per testing. Volume intrusion/extrusion curves wereautomatically obtained, and the data, including the change of pore radius and pressureand the amount of mercury, were collected by computer. But the parameters, forexample pore volume, pore specific surface area and pore radius distribute, need to befuture analyzed based on data or curves above.

3.2.3. Permeability testGas phase absolute permeability is also named Kleinberg permeability andapproximately equal to the Helium gas-phase permeability (Fu and Qin, 2003).Absolute permeability of coal samples (by SY/ T 5843—1997) was tested under theWhole Core flow System, manufactured by Terra Tek Inc., USA. The device includespressure system, temperature system, control system and the core holder, etc. Theexperimental system also has a complete set of rock sample preparation and routinecore analysis equipment. The maximum of surrounding pressure and fluid pressure ofthe instrument is respectively 70MPa and the max is 65MPa.

In the study, 5 undeformed blocky coal samples with very few cracks were selectedto measure the single-phase permeability of helium and water and the gas-waterrelative permeability. Before the testing, all the samples were drilled paralleling to thebedding direction into cylindrical shape with a diameter of 25 mm and a height of 50mm. The gas used in the testing was Helium and each experiment was performed inroom temperature and 6 different pressure spots.

All the measurements were under simulated in-situ stress conditions using a tri-axialcell with isotropic ambient pressure of 2.5 MPa and 3.5 MPa. During the testing, thegas permeability in coal was calculated in each pressure under no change of effectivestress and temperature according to the following formula:

(1)Kp q L

A p pg

g g=×

−( )2 100

2

12

02

µ


Where, Kg is the gas permeability under each pressure spot, 10-3×m2; p0 is standardatmospheric pressure (ATM), MPa; qg is the gas flux, cm3/s; µg is the gas viscosity,mPa·s; L is the coal sample’s length, cm; A is the coal sample’s cross section, cm2; p1is the entrance pressure, MPa.

Further, the gas absolute permeability can be calculated by the following formula:

(2)

Where, Kg is the same as formula (1); K0 is the absolute permeability, 10-3×m2; pmis the average pressure; b is a constant relevant to the gas property and pore structure.

3.2.4. Adsorption test Adsorption testing is performed under the Isothermal Adsorption/Desorption SystemModel IS-100 made by Terra Tek Company in USA. The upper temperature limit ofthe instrument is 50°C and the upper pressure limit is 30 MPa. In this study, all thesamples were made into equilibrium moisture sample by the ASTM D1412-1999. Theabsorbate is methane with a purity of 99%, and the maximum initial pressure is 15MPa.The experiment temperatures are 30°C for all samples, 40°C and 50°C for 4 samplesof these samples. Qian et al. (1996) described experimental equipment and methods indetail.

The principles of the instrument testing are the volume method and the Langmuirequation [Langmuir] used to draw isothermal adsorption curves and calculate relatedparameters. The gas sorption isotherms in coal were modeled using the Langmuirisotherm:

Or,

Where P is the equilibrium gas or vapor pressure, MPa; V is the volume of gasadsorbed, commonly reported at standard temperature and pressure (STP), per unitmass of coal, m3/t or cm3/g; VL is the Langmuir monolayer volume, m3/t or cm3/g; bis an empirical constant, MPa-1; PL is the Langmuir pressure, equal to 1/b, MPa.

4. RESULTS AND DISCUSSIONS4.1. Geological characteristics of CBM reservoirs4.1.1. Coal petrography In Jiaozuo coalfield, macroscopic lithotypes of the No. II1 coals are dominated bybright coals and semi-bright coals, but the No. I2 coal is dominated by semi-bright andsemi-dark coals. The main body of the coal seam is a uniform sequence of clarain and

VV P

P PL

L

=+

P

V bV

P

VL L

= +1

K Kb

pgm

= +

0 1


durain, and thin layers of vitrain and fusion are restricted to these intervals showinglenticular shape. The No. II1 coal composition is dominated by more than 86% organicmacerals components, in which vitrinite reachesr 38~76% and the rest is inertinite(Table 1).

4.1.2. Coal rank and coal qualityThe maximum reflectance of vitrinite (Rmax) of the No. II1 coal across the Jiaozuo isbetween 3.16% and 4.78% (Fig. 3) (Qin et al., 1990). The distribution of coal rank iscontrolled by the burial history and the Superposition of palaeoheat flow imported bythe fracture and shows obvious coal-class sub-zone (Qin et al., 1990; Su et al., 2005).The coal metamorphism gradually increases trend from the east to the west, thenortheast to the southwest, and the same coal rank occurred as northeast-strike. Coalquality data across Jiaozuo coalfield are listed in Table 1. The coal quality of the No. II1

coal shows distribution Law in plane scale to a certain extent as follows: the volatilematter content and H-element content have an increase tendency but the C-elementcontent presents downtrend from the west to the east. The distribution tendency of coalquality is in keeping with that of coal rank. On the whole, the No. II1 coal belongs toanthracite and No. 3 shows the characteristics of lower ash-content, especially lowersulfur-content, lower phosphide-content, and mid-to-high caloric value (Hao et al.,2005).

Figure 3. Rmax distribution map of the No. II1 coal in Jiaozuo coalfield(modified from Qin et al., 1990).

4.2. Physical properties of CBM reservoirs4.2.1. Pore and crackCoal is a complex polymeric material with a complicated porous structure that isdifficult to classify (Clarksona and Bustinb, 1999). Previous studies (C1ose, 1993;Gamson et al., 1998) show coal is a double porous medium which includes matrixpores and cracks. The size, shape, porosity, permeability and connectivity of the poresand cracks determine the reservoir, migration and output of CBM, thereby constrainingthe flow of CBM and its production.


4.2.1.1. Crack In study area, the cracks in the coal seam develop heterogeneously. The observationunder the mines shows that various creaks with different sizes develop in coal,including the large cracks through the whole coal seam and even into the roof and thefloor or through the tonsteins but suspending in the roof and the floor, the small creaksdistributing in different coal delaminations and suspending in the tonsteins and themicro creaks only developing in vitrain strips. These cracks mainly are oriented inNNW, NE, NNW, NNE or near SN directions (Fig. 4), and most of them are high-obliquity cracks with inclination of over 50°. There are two sets of cracks oriented indifferent directions in most of coal mines, of which the larger often cut the smaller, andthe same set of creaks show en echelon style with 0.2~7 cm interval. But there are threesets of creaks in local area, such as Guhanshan mine field.

The observation to hand specimen by the naked eye and to polished specimen bymicroscope reveals that cleats of the No. II1 coal are a little weak and only develop invitrain strips, some of which are filled or half-filled by kaolinite and calcite. Further,the secondary interstices of different section even in the same mine have differentdistribution, showing the heterogeneity in creak development and permeability of thecoal seam. The micro-cracks are mainly NE, near EW and NEE strike, roughly thesame to regional fractures and macro-creaks (Fig. 4).

a bFigure 4. The rose diagram of microfracture strikes (a) and trends (b) in the No.II1

coal seam in Jiaozuo coalfield.

4.2.1.2. PorePore structure includes the pore size, size distribution and geometry/morphology of theinterconnecting pore network (Liu et al., 2009). Previous studies put forward manyclassification methods according to the pore size and the action in gas storage and thepore into many types (XoπoT, 1966; Sang et al., 2005). XoπoT divided the pore intofour types: micropore (pore diameter: <10 nm), transitional pore (pore diameter:10~100 nm), mesopore (pore diameter: 100~1000 nm) and macropore (pore diameter:>1000 nm). The decimal classification has been the most widely used. In order to avoidthe influence on macropores’ statistics by the gap between the particles during the


testing process, the pores, with a diameter of more than 10000 nm, were excluded frommacropores’ statistics in the study.

Previous results showed that the porosity of the No. II1 coals was moderate inJiaozuo coalfield. The porosity values generally range from 7% to 12% and show anincrease trend from the east to the west, the shallow to the deep (Meng and Peng,1998).

The data shows micropores and transitional pores contribute to the specific surfacearea of the whole coal sample much larger than mesopores and macropores (Table 2).In the measure scope of mercury injection experiment, the specific surface area isdominated by 58.6% micropores with an average of 42615 cm2/g, followed by 40.4%transitional pores with an average value of 29265 cm2/g, and then 0.9% mesopores and0.1%macropores. The contribution to the pore volume follows the sequence astransitional pores (average percentage: 49.3%) > micropores (average percentage:32.2%) > mesopores (average percentage: 10.8%) > macropores (average percentage:0.7%). Thus, the small diameter pores are much richer than large diameter pores in theNo. II1 coal.

In the study area, the whole pore volume and the whole specific surface area of themylonitic coal samples range from 273 to 534×10-4 cm3/g, 6.6~8.7m2/g, more than thoseof the undeformed coal samples. The two parameters of different pore sizes in myloniticcoal samples have a similar contrast between two kinds of coal samples (Fig. 5).

Table 2. The pore-structure parameters of the No. II1 coal in Jiaozuo coalfield.

Additional information for pore structures can be obtained from their mercuryintrusion/extrusion curves. This method has been widely used as a petrophysical toolfor evaluating traditional petroleum reservoir such as sandstones and carbonates, andit is also useful for coals (Qin, 1994; Chen and Tang, 2001; Zhang, 2005). Accordingto the hysteresis loops formed by the difference between the intrusion curves and theextrusion curves, the basic shape and the connectivity of pores in coal can be evaluated(Qin, 1994). But in view of the pores complexity and all kinds of pores coexist in thesame pore diameter, the hysteresis loops only reflects the main pore types and thewhole properties of all the pores (Zhang, 2005). The evident hysteresis loops of all thecoal samples in Jiaozuo coalfield show that there are many open pores. For the largepore diameter range, the half- closed pores in mylonitic coals is less than those in

Items Macropore Mesopore transitional pore Micropores Total

cm2/g 0 ~183 0 ~2063 24735 36655 34908 ~ 61745 61710 88556

average 48 685 29265 42615 72613

% 0 ~ 0.23 0 2.5 29.9~46.7 52.7 69.7

specific surface

areaaverage 0.1 0.9 40.4 58.6

10-4cm3/g 0 ~100 0 145 96 ~ 206 36 128 214 597

average 30 43 147 91 311

% 0 ~19. 5 0 ~27.2 35.1 58.8 18.1 46.6pore volume

average 7.7 10.8 49.3 32.2

~

~

~

~

~

~

~

~

~


undeformed coals, but the open pores in mylonitic coals are more than those inundeformed coals (Fig. 6). However, for the small pore diameter range, the comparisonbetween the contents of open pores and half-closed pores in two kinds of coalbodystructure coals are On the contrary.

Precious study show that micropores in coal provide the gas with adsorption space,transitional pores with the area of capillary condensation and diffusion, andmacropores and mesopores with the area of seepage and laminar (Sang, 2005). Thus,the No. II1 coals have stronger adsorption and diffusion capacity, but the capacity ofseepage and laminar flow are weaker. The gas storage capacity in mylonitic coals ismore than that in undeformed coals, but the gas migration in mylonitic coals is moredifficult than that in undeformed coals.

a bFigure 5. The distribution curve of the pore size of mylonitic coal (a: G-1) and

undeformed coal (b: G-2). Compositional data for these coals are summariazed inTable 1.

Figure 6. The mercury intrusion/extrusion curves of mylonitic coal (G-1) andundeformed coal (G-2). Compositional data for these coals are summariazed in Table 1.


4.2.2. PermeabilityPermeability is a critical factor controlling CBM production and an importantparameter for evaluating the economic production of natural gas from coal seams(Clarkson and Bustin, 1997; Thomas et al., 2007; Andrew et al., 2006). Thepermeability of coals can be calculated by many methods, such as coal core samples’testing in laboratory, conversion of the geophysical logging curve, conversion of in-situ permeability coefficient, well-test in CBM well and numerical simulation of CBMreservoir. Because of the difference in testing principles, methods and coal samples ortest position, the measure results have great differences, which have their ownadvantages and disadvantages.

Results from the 6 groups of well-tests, which distribute in Guhanshan coal mineand Zhongma coal mine in the center and Encun coal mine in the south, show that thereservoir natural permeability vary greatly from 0.0001 to 83.71 mD. Besides, thepermeability value of CBM well could be increased 5~10 times by using hydraulicfracture (Table 3). Moreover, the permeability coefficient, tested under the coalminesin the center and the south of the study area, shows the permeability value also varygreatly from 0.004~3.6 mD.

Table 3. The well-test permeability of the CBM wells in Jiaozuo coalfield.

In this study, 5 blocks of coal samples were chosen to test the permeability. In theexperiment, the gas-water relative permeability curve in 5 coal samples could beobtained because the permeability value of other coal samples is so low that the testingresult could not be obtained in the experiment (Table 4; Fig. 7). The testing resultsshowed the single-phase permeability of all coal samples was low: the gas-phasepermeability vary greatly from 0.02 to 0.945mD under isotropic ambient pressure of2.5 MPa and from 0.013~0.552mD under isotropic ambient pressure of 3.5 Mpa. Thewater-phase permeability was lower and the water-phase permeability values of 2 coalsamples with the lowest gas-phase permeability value were too low to be measured.The water-helium relative permeability values obtained from the water-helium relativepermeability curve is only 2.4 mD, far lower than the areas with better conditions inCBM development, for example, San Juan Basin and Black Warrior in United Statesand Warrior Basin in Australia.

Coal mine Guhanshan Z hongma Encun

Well code T1 T2 T3 T4 ZM1 CQ6

natural permeability(mD) 1.58 3.16 3.82 76.79 ~ 83.71 21.88 0.001 ~ 0.081 0.002

Permeability after hydrofrac treatment(mD)

16.18 0.091 ~ 0.772

~


Figure 7. The relation of helium-water relative permeability and gas saturation inJiaozuo field.

Table 4. The permeability testing results of the coal samples in the laboratory.

Abbreviations: K, Kw are respectively the single-phase permeability tested by helium and water in the Lab

Based on the analysis of several kinds of the permeability testing results and theobservation on cores and coal mines, the permeability is mainly controlled by severalfactors: coalbed depth, regional structure, cleat development, coalbody structure.Generally, there is higher permeability near fault structure or the boundary of faultblock in the study area. For example, the four CBM wells in Guhanshan coalmine arelocated the downthrown Block of normal faults. Thus the well-test permeability arehigher than that in the other coalmines, where are in a state of tensile stress and thefactures generally develop because of the tensile stress of the boundary faults.However, the well-test permeability values vary greatly from 1.58 to 83.71mD because

No coalmine burial depth(m) ambient pressure(MPa) K(mD) Kw(mD)

2.5 0.199G-2 Guhanshan 530

3.5 0.1410.035

2.5 0.0599FZ-1 Fangzhuang 512

3.5 0.0283

2.5 0.264FZ-2 Fangzhuang 160

3.5 0.1210.033

2.5 0.933Bai Baizhuang 246

3.5 0.5450.036

2.5 0.0199ZC-2 Zhucun 200

3.5 0.0132


of the difference in the fracture development level. As the higher well-test permeabilityvalue in the four CBM wells, The T3 and T4 wells are closer to Tuanxiang fault zone,so their well-test permeability value are higher than those of the other two CBM wells.Moreover, the permeability of syncline axle is very low because of the action ofextrusion stress. For example, the well CQ6 is located near the Shaft of QiangnanSyncline, and its well-test permeability is only 0.001~0.08mD, the minimumpermeability value in 6 groups of well-test. According to the permeability-test resultsin laboratory, the helium permeability under isotropic ambient pressure of 2.5 MPa areall higher than that under isotropic ambient pressure of 2.5 MPa, and the heliumpermeability of coal sample from the depth of 160 m is much higher than that of coalsamples from the depth of 520 m. Thus, we can draw a conclusion that the permeabilityis inverse relationship with the burial depth. Precious study showed that thepermeability of undeformed coal seam is better than tectonic coal seam (Su and Sheng,1999; Zhong et al., 2004; Peter et al., 1998). Therefore, the reservoir permeability ofthe No. II1 coal seam in the east coalfield is better than that in the middle and the west,and can be inferred according to the coalbody structure distribution.

In a word, the reservoir permeability in Jiaozuo coalfield is generally low and hasan evident heterogeneity. There are higher-permeability region for CBM exploration,for example, near fault structure or the boundary of fault block. Moreover, the reservoirpermeability may be so significant improved after hydraulic fracture. All of theseindicate that high permeability districts for CBM exploration and development may beworkable in the study area.

4.3. Coal adsorptionIn the study area, the No. II1 coals have high adsorption capacity. The testing results ofisotherm adsorption experiment in previous study and this study show Langmuirvolume parameter (VL) of equilibrium-moisture-bearing coal samples of the No. II1

range from 22.68~46.67 cm3/g, with an average value of 38.07 cm3/g, under thetemperature of 30°C and Langmuir pressure parameter (PL) from 1.17 to 4.96 MPa,with an average value of 3.18 MPa.

Gas sorption by coal is closely related to its physical and chemical properties (Peteret al., 1998; Sun et al., 2009). Generally, the adsorption capacity of coal is influencedby many factors, including coal rank (coal metamorphism), maceral composition,macro- and micro-lithotype, pore, moisture, temperature, pressure, and so on. For thestudy area, the parameter VL of mylonitic coals varies from 33.23 to 45.97 cm3/g, withan average value of 38.33cm3/g. It is a little higher than that of undeformed coals, withan average value of 36.85 cm3/g. The parameter PL varies from 2.37 to 3.98MPa, withan average value of 3.63cm3/g, and is far higher than that of undeformed coals, with anaverage of 3.04 MPa. Thus, the conclusion can be draw that mylonitic coal has strongeradsorption capacity than undeformed coals (Fig. 8). The main reason of the differenceis that the mylonitic coal has larger pore content, especially macropore content thanundeformed coals.


T=30°C T=40°C T=50°CFigure 8. High-pressure methane adsorption isotherms for the mylonitic coal (G-1)

and undeformed coal (G-2) coal. Samples with different coalbody structure indifferent temperature. Compositional data for these coal are summariazed in Table 1.

The symbol “�” and “�” refers to the mylonitic coal and the undeformed coalrespectively.

Temperature is another factor on the change of coal adsorption. In general, as thetemperature increases, the adsorption capacity of coal dropped. This experiment alsoproved this conclusion (Fig. 8). Further study shows that, as temperature increase, thedeclination of adsorption volume of coals under higher pressure section is faster thanthat under lower pressure section. For example, under the pressure range of 0~4 MPa,the decay rate for the coal sample from the Guhanshan coal mine is 0.18 m3/(t·°C) from30 to 40°C, about 1.8 times of the decay rate of 0.10 m3/(t·°C) from 40 to 50°C. Butunder the higher pressure range of 4~20 MPa, the decay rate is about 0.28 m3/(t·°C)from 30 to 40°C, about 1.4 times of the decay rate of 0.20 m3/(t·°C) from 40 to 50°C.Moreover, as temperature increases, the difference in adsorption capacity betweenmylonitic coal and undeformed coal decreases.

4.4. Gas content and compositionGas content determination techniques generally fall into two categories: (1) directmethods which actually measure the volume of gas released from a coal sample sealedinto a desorption canister and (2) indirect methods based on empirical correlations, orlaboratory derived sorption isotherm gas storage capacity data. (William and Steven,1998)

In the study area, more than 1000 coal bores had been drilled in nearly 100 years,providing with many data, including the burial depth, coal thickness, the roof and thefloor, gas content, gas composition, and so on. The gas content in the No. II1 coal seamwith the burial depth of 163~1070 m varies very greatly from 4.65 to 45.75 m3/t, withan average of 18.3m3/t. Generally, gas content gradually increases from northeast tosouthwest (Fig. 9 and Table 5), and the highest gas content region distributes in thesouth-central coalfield. The gas content in the deep fault blocks is higher than that inthe shallow. In the same fault block, the gas content increases as the burial depth ofcoal seam increases, but not in an unlimited increase, such as Encun mine field, thehighest gas-content region is not synclinal axis but on the north side of synclinal.


Therefore, the gas content must tend to a saturation value when coal seam reaches acertain depth in the same fault block with little tectonic transformation.

In the study area, gas composition in the No. II1 coal seam varies very greatly.Under the CH4 weathering zone, in general, the gas composition is mainly CH4,followed by N2 and CO2, and then less than 1% heavy hydrocarbon, and the CH4

percentage in the whole gas composition increases from the shallow to the deep. Theδ13 value of methane is -3.41%, the δ13 value of C2H6 is -2.879%, the δ13 value of CO2

is -2.483%, and the C1/C1-5 value is 0.99. These data show that the genetic type ofCBM in the study area is homologous thermal cracking gas of humic coal with highmatunity.

The factors controlling on gas content mainly include the structure, coalbed depth,effective burial depth, the roof and the floor, and so on. More analysis can be seen inthe paper by Zhang (2007).

Table 5. In-place CBM resource and CBM abundance in Jiaozuo coalfield.Qiannan-W, -E and –N are respectively the west part, the east part and the

north part of the Qiangnan coal mine.

CoalmineArea

(Km2)Coal thickness

(m)Coal reserve

(106t)Gas content

(m3 /t)CBM resource

(108m3)CBM abundance

(108m3/km2)

Encun 65.99 5.55 564.22 28.41 160.30 2.43

Zhongma 8.73 5.53 70.89 13.75 9.75 1.12

Guhanshan 19.66 4.52 137.12 16.89 22.17 1.13

Qiangnan-W 12.67 6.93 130.77 29.09 38.04 3.00

Qiangnan-E 19.55 7.50 218.37 34.60 75.56 3.86

Qiangnan-N 7.28 5.51 58.19 14.48 8.42 1.16

Jiulishan 10.92 5.49 89.05 15.27 13.29 1.22

Jiaonan 22.04 4.99 163.91 22.38 36.68 1.66

Yanma 7.39 7.13 83.69 12.76 9.67 1.31

Xinhe 13.96 5.91 119.57 13.43 16.06 1.15

Fengying 5.51 3.86 30.73 15.76 4.94 0.94

Fangzhuang 4.48 4.03 41.81 9.07 2.96 0.61

Xiuwu 60.41 6.25 562.57 37.34 210.08 3.48

Zhaojing 89.92 5.32 788.73 29.84 143.07 1.59

Dazhaoying 16.99 4.89 166.63 32.55 23.60 1.40

Zhaogu 20.18 4.18 81.65 9.55 12.26 0.61

Fangzhuang 16.54 5.39 130.91 14.53 19.02 1.15

Wuliyuan 54.06 5.02 393.24 26.26 103.27 1.91

Fengcheng 106.43 4.86 750.03 32.88 210.15 1.98

Kuaicunying 13.91 5.90 119.85 9.55 11.45 0.82

Chizhuang 24.99 4.38 158.75 16.00 25.79 1.03

Bobi 54.08 4.13 318.58 8.50 27.72 0.51

Total 1184.24 1.81


Figure 9. Gas-content contours (in m3/tone) of the No. II1 coal seam in Jiaozuocoalfield.

4.5. CBM RESOURCE AND PRODUCIBILITY POTENTIAL4.5.1. CBM resourceThe geologic reserves of CBM resources are calculated based on the usual volumetricmethod (Charles et al., 1998; Drobniak et al., 2004; Langenberg et al., 2006). Thismethod can briefly be as follows:

Gi = A i×H i×D×Ci (1)

Where Ai is surface area of the block (km2); H represents average net coal thicknessof the block (m); D is average coal density (t/m3); C is the gas content from estimationor direct test of the block (m3/t); and Gi is the GIP by volumetric resource estimationmethodology of the block (m3).

Firstly, according to region structure, coal thickness and whether they are mined, 4large blocks were divided into. On this division basis, 24 sub-blocks and 79 smallestcalculated blocks divided into. In each smallest calculation blocks, the gas resource canbe obtained by the volumetric equation (1).

Then the geologic reserves in the study area can be estimated by the equation (2)

(2)G = Gi


Where G is the geologic reserves of the No. II1 coal seam (m3); n is the calculationblocks, equal to 79 here.

Since the collected data are from the shallow basin, with less than 1000 m deep, andthe drilled area mainly during the coal geological exploration, we could use differentmethods to estimate for the deep and undrilled areas: 1) for the shallow coal seam withless than 1000 m deep, where there is undrilled but many data can be available nearby,the gas content gradient method can be used; 2) for the undrilled area, where few datacan be valid or the deep with more than 1000 m, the adsorption isotherm method canbe used (Saulsberry et al., 1996; Yao et al., 2009).

In the calculation on gas resource, the coal density was chosen according to theaverage density of the every block or nearby blocks, and the values range from 1.45 to1.49t/m3. And the coal thickness in undrilled area can be calculated by interpolationmethod in coal thick isoline chart.

The existing total in-place CBM resources in the No. II1 coal seam presented inJiaozuo coalfield are estimated to be 1184.24×108 m3 (Table 5), most of them mainlydistribute in the depth of 1000 ~ 1500 m, followed by the depth of 1500 ~ 2000 m and500~100m, and then the depth of shallower than 500m (Table 6). The existing totalCBM resources in-place are dominated by more than 70% the inferred CBM resourcereserves, which distribute the undrilled places with few coal geological knowledge anddeeper than 1000m. There are six coal districts with the total in-place CBM resourcesof more than 100×108m3, respectively. The six coal districts are Fengcheng coaldistrict, Xiuwu coal district, Encun coal mine, Zhaojing coal district, Qiangnan coalmine and Wuliyuan coal district (Table 5).

Gas resource concentrations (gas-in-place in m3/km2), an important index fordividing the target CBM area, are given in Table 5 and Figure10. The resourceconcentration of the No. II1 coal seam in Jiaozuo coalfield is in the range of(0.513–3.478)×108 m3/km2, with an average of 1.805×108 m3/km2. The areas with highCBM resource concentration (generally higher than 2.0×108 m3/km2) in Jiaozuocoalfield include (1) Xiuwu coal district, (2) Qiannan coal mine and (3) Encun coalmine.

Table 6. CBM resource in different depth and different level reserves.

4.5.2. CBM resource producibility potentialCBM resource producibility potential relate to economic and geological factors. Thegeological factors, including geological properties and reservoir physical properties,play important action on the CBM resources recoverability. Based on the fuzzymathematics and comprehensive analysis of main geological parameters, the CBMresources assessment indexes in Jiaozuo coalfield have been put forward (Table 7).

Depth(m) <500m 500 ~ -1000m 1000 ~ 1500m 1500 ~ 2000m

CBM resource(108m3 ) 46.14 312.97 523.52 301.6


Figure 10. Isopach map (in m3/km2) of CBM resource abundance in Jiaozuocoalfield.

Table 7. Comprehensive assessment criteria of for favorable CBM resourceexploration areas selected in Jiaozuo coalfield.

Explanation: Pc is the critical desorption pressure, and P is the reservoir pressure. The number of the symbol“+” expresses the importance of the parameter, more numbers of symbol “+”, more important.

The classified criteriatype Parameter

II III IVParameter

wight

Coal thickness(m) > 6 6 ~ 5 5 ~ 3 < 3 + +

Gas content(m3/t) > 25 25 ~ 15 15 ~ 10 < 10 + + +CBM abundance

(108m /km ) > 2 2 ~ 1.5 1.5 ~ 0.5 < 0.5 +

Area(km2) > 40 40 ~ 20 20 ~ 10 < 5 +Res

ourc

epr

oper

ties

Burial depth(m) 300 ~ 800 800 ~ 1000 1000 ~ 1500 > 1500 + +Pressure gradient

(kPa/m) > 10 10 ~ 6 6 ~ 4 < 4 +

Pc/P(%) > 0.8 0.8 ~ 0.5 0.5 ~ 0.2 < 0.2 + +natural

permeability(mD)

> 10 10 ~ 1 1 ~ 0.1 < 0.1 + + +

Gas saturation(%) > 80 80 ~ 60 60 ~ 40 < 40 + +

Coalbody structure Undeformed Cataclastic Granular Mylonitic + + +

Tectonic development level

Simple.Undeveloped

structure

Relative simple.Few faults and

larger folds

Relative complex.

Developed largefolds

Very complex.Discontinuous

coal seam+ +

Wor

kabl

epr

oper

ties

Hydrogeologycondition

Simple.Easier to reduce

pressure by drainage

Relative simple,Larger

displacement,Stable

groundwater source

Relative complex.

Water-bearing distribution

controlled by faults

Very complex.Greatly change

in Water-bearing

+ +

23


In the assessment system, in the light of concrete conditions, the four parametersincluding coal seam thickness, gas content, primary permeability and coalbodystructure are the most important in all parameters, and influence on the CBM resourceestimation. In other words, if coal seam thickness is less than 3m, or gas content of thecoal seam lower than 10m3/t, or natural permeability of the coal seam lower than0.1mD, or the whole coal seam belongs to mylonitic coal, the coal seam can beclassified to non-extraction coal seam. Further, according to the hierarchical priorityprinciple of the other parameters, the CBM resources recoverability in Jiaozuocoalfield has been estimated and favorable zones for CBM exploration anddevelopment have been indicated.

According to the assessment results, four types of CBM exploration anddevelopment prospects in Jiaozuo coalfield are identified: Type I is chosen as the mostfavorable zone; and it is the highest priority to mine the CBM resources areas innowadays mining and technical conditions. Type II is a favorable zone; and its miningpriority is lower than type I and can be used as back-up of the minable area in the nearfuture. Type III is a relatively favorable zone; it is the non-minable area in the shortrun. Type IV is an unfavorable zone. It is non-minable area.

To a certain extent, there is a great potential for CBM production when it is withhigh gas content, high CBM resource concentration in Jiaozuo coalfield. The mostfavorable zones in Jiaozuo coalfield are Guhanshan coal mine, Jiulishan coal mine andthe west part of Qiangnan coal district, in which there are better permeability, mainlyundeformed coal, higher gas-content and gas saturation, relatively simple tectonic andhydrogeology condition, and especially more information available in Guhanshan andJiulishan coalmines.

5 CONCLUSIONS(1) The No. II1 coal seam, with an average thickness of 5.36 m, is the main

economic coal seam of CBM in Jiaozuo coalfield. Macroscopic lithotypes ofthe No. II1 coals are dominated by bright coals and semi-bright coals, and itsorganic macerals components are dominated by vitrinit. The coalbodystructure of the No. II1 coal seam is very different in different part and can begenerally divided into 1~3 sub-layers.

(2) The cracks in the study coal seam develop heterogeneously and mainly areoriented in NNW, NE, NNW, NNE or near SN directions, and most of themare high-obliquity cracks with inclination of over 50°. The micropores in theNo. II1 coal seam are the major pores, secondly are transitional pores, andthen less macropores and mesopores. The No. II1 coal seam has strongeradsorption with an average maximum adsorption capacity of 38.07cm3/g, andmonlyitic coals have stronger adsorption than undeformed coals, and thedifference in adsorption capacity between mylonitic coal and undeformedcoal decreases as the temperature increases. The permeability of the No. II1

coal seam is generally lower and has an evident heterogeneity. But there arehigher-permeability region for CBM exploration, for example, near faultstructure or the boundary of fault block. Moreover, the reservoir permeabilitymay be so significant improved after hydraulic fracture. All of these indicate


that high permeability districts for CBM exploration and development may beworkable in the study area.

(3) The genetic type of CBM in the study area is homologous thermal crackinggas of humic coal with high matunity. Generally, gas content with the burialdepth of 163~1070 m varies very greatly from 4.65 to 45.75 m3/t, with anaverage of 18.3 m3/t, and gradually increases from northeast to southwest.The highest gas content region distributes are in the south-central coalfield;the gas content in the deep fault blocks is higher than that in the shallow. Inthe same fault block with little tectonic transformation, the gas content maytend to a saturation value when coal seam reaches a certain depth.

(4) The existing total in-place CBM resourcess of the No. II1 coal seam presentedin Jiaozuo coalfield are close to 1.2 ×1012 m3. Most of them distribute in thedepth of 1000 ~ 1500 m. The existing total CBM resources in-place aredominated by the inferred CBM resource reserves (more than 70%), whichdistribute the undrilled places with few coal geological knowledge and deeperthan 1000 m. The resource concentration of the No. II1 coal seam in Jiaozuocoalfield is in the range of (0.513–3.478)×108 m3/km2, with an average of1.805×108 m3/km2. The areas with high CBM resource concentration existmainly in the southern-east part of Jiaozuo coalfield.

(5) To a certain extent, Jiaozuo coalfield has an optimum CBM productionpotential. The most favorable zones in Jiaozuo coalfield are Guhanshancoalmine, Jiulishan coalmine and the west part of Qiangnan coal district, inwhich there are better permeability, mainly undeformed coal, higher gas-content and gas saturation, relatively simple tectonic and hydrogeologycondition, and especially more information available in Guhanshan andJiulishan coalmines.

ACKNOWLEDGEMENTSThis research was financially supported by the National Science Foundation of China(Grant No. 40602017), Nation Basic Research Program of China (Grant No.2006CB202204) and the Ph.D. Programs Foundation of Henan Polytechnic University(Grant No. 648513).

REFCRENCEDrobniak A., Mastalerz M., Rupp J. and Eaton N., 2004. Evaluation of coalbed gas

potential of the Seelyville Coal Member, Indiana, USA. International Journal ofCoal Geology 57(3-4), 265-282.

Andrew B., Willem L. and Cristina P., 2006. Coalbed methane resources and reservoircharacteristics from the Alberta Plains, Canada. International Journal of CoalGeology 65(1-2), 93-113.

Antonette K. and Markowski K., 1998. Coalbed methane resource potential andcurrent prospects in Pennsylvania. International Journal of Coal Geology38(1-2), 137-159.

Charles M., Boyer II. and Bai Q.Z., 1998. Methodology of coalbed methane resourceassessment. International Journal of Coal Geology 35(1-4), 349-368.


C1ose J.C., 1993. Natural fracture in coal. In: Law B.E. and Rice D.D. (eds.),Hydrocarbons from Coal: AAPG Studies in Geology 38, pp. 119-132.

Clarkson C.R. and Bustin R.M., 1997. Variation in permeability with lithotype andmaceral composition of Cretaceous coals of the Canadian Cordillera.International Journal of Coal Geology 33(2), 135-151.

Clarksona C.R. and Bustinb R.M., 1999. The effect of pore structure and gas pressureupon the transport properties of coal: a laboratory and modeling study. 1.Isotherms and pore volume distributions. Fuel 78 (11), 1333-1344.

Chen P. and Tang X.Y., 2001. The research on the adsorption of nitrogen in lowtemperature and micro-pore properties in coal. Journal of China Coal Society26(5), 552-556 (in Chinese with English abstract).

Dai S.F., Ren D.Y., Tang Y.G., Shao L.Y. and Li S.S., 2002. Distribution, isotopicvariation and origin of sulfur in coals in the Wuda coalfield, Inner Mongolia,China. International Journal of Coal Geology 51(4), 237-250.

Dai S.F., Hou X.Q., Ren D.Y. and Tang Y.G., 2003. Surface analysis of pyrite in theNo. 9 coal seam, Wuda Coalfield, Inner Mongolia, China, using high-resolutiontime-of-flight secondary ion mass-spectrometry. International Journal of CoalGeology 55(2-4), 139-150.

Dai S.F., Ren D.Y., Chou C.L., Li S.S. and Jiang Y.F., 2006. Mineralogy andgeochemistry of the No. 6 coal (Pennsylvanian) in the Junger Coalfield, OrdosBasin, China. International Journal of Coal Geology 66(4), 253-270.

Fu X.H. and Qin Y., 2003. Theories and Techniques of Permeability Prediction ofMultiphase Medium Coalbed-Methane Reservoirs. China University of Miningand Technology Press, Xuzhou, pp.327 (in Chinese).

Gamson P., Beamish B. and Johnson D., 1996. Efect of coal microstmcture andsecondary mineralization on methane recovery. Geological Special Publication199, 165-179.

Gao Z.Q. and Wang G.Z., 2008. The characteristic and its gas-bearing properties of gasstorage layer in coalbed gas in jiaozuo coalfield. Geology of Chemical Minerals30(1), 1-8 (in Chinese with English abstract).

Hao J.S., Wei G.Y. and Liu Q.X., 2005. Characteristics of coal quality andgeochemical in jiaozuo coal basin. Journal of Jiaozuo Institute of Technology24(3), 193-195 (in Chinese with English abstract).

Langenberg C.W., Beaton A. and Berhane H., 2006. Regional evaluation of thecoalbed-methane potential of the Foothills/Mountains of Alberta, Canada.International Journal of Coal Geology 65(1-2), 114-128.

Liu D.M., Yao Y.B., Tang D.Z., Tang S.H., Che Y. and Huang W.H., 2009. Coalreservoir characteristics and coalbed methane resource assessment in Huainanand Huaibei coalfields, Southern North China. International Journal of CoalGeology 79(3), 97-112.

Li J.M., Chao H.Y., Li. X.J. and Liu H.L., 2009. Characteristics of coalbed methaneresource and the development strategies. Natural Gas Industry 29(4),9-13 (in Chinese with English abstract).


Jiang B. and Ju Y.W., 2004. Tectonic coal structure and its petrophysical features.Natural Gas Industry 24(5), 27-29.

Ju Y.W., Jiang B. and Hou Q.L., 2005. Structural evolution of nano-scale pores oftectonic coals in Southern North China and its mechanism. Geological Society ofChina 79(4), 269-285.

Karacan and Okandan, 2001. Adsorption and gas transport in coal microstructure:investigation and evaluation by quantitative X-ray CT imaging. Fuel 80(4),509–520.

Meng Z.P. and Peng S.P., 1998. Assessment of coal seam II1 reservoir in jiaozuomining Area. Journal of China University of Mining & Technology 27(2),162-166 (in Chinese with English abstract).

Peter J., Crosdale B., Beamish B.and Valix M., 1998. Coalbed methane sorptionrelated to coal Composition. International Journal of Coal Geology 35(1-4),147-158.

Qian K., Zhao J. and Wang Z., 1996. Coalbed Methane Exploration and DevelopmentTheory and Experimental Testing Technology. Petroleum Industry Press,Beijing, pp. 119-142 (in Chinese).

Qin Y., 1994. Micropetrology and structural evolution of high-rank coals in China.China University of Mining & Technology Press, Xuzhou, China. pp. 216(in Chinese).

Qin Y., Hou S.N. and Li D.H., 1990. Zoning features of shanxi formation coal II1 rankand its geological significance in Jiaozuo coalfield. Coal Geolog & Exploration5, 36-39 (in Chinese with English abstract).

Bustin R.M. and Clarkson C.R., 1998. Geological controls on coalbed methanereservoir capacity and gas content. International Journal of Coal Geology38(1-2), 3-26.

Sang S.X., Zhu Y.M. and Zhang S.Y., 2005. Solid-gas interaction mechanism of coal-adsorbed gas (I)—coal pore structure and solid-gas interaction. Natural GasIndustry 25(1), 13-15 (in Chinese with English abstract).

Saulsberry J.L., Schafer P.S. and Schraufnagel R.A. (eds.), 1996. A Guide to CoalbedMethane. Reservoir Engineering, Gas Research Institute Report GRI-94/0397,Chicago, Illinois, pp. 376.

Song Z.M. and Meng Z.P., 2002. Discussion on geological controlling factors ofcoalbed methane content in jiaozuo mining area. Journal of China University ofMining&Technology 31(2), 179-181 (in Chinese with English abstract).

Su X.B., Lin X.Y., Liu S.B., Zhao M.J. and Song Y., 2005. Geology of coalbedmethane reservoirs in the Southeast Qinshui Basin of China. InternationalJournal of Coal Geology 62(4), 197-210.

Su X.B. and Sheng J.H., 1999. Coalbed methane reservoir description of II1 coal inshanxi formation (low permian), henan province. Journal of Jiaozuo Institute ofTechnology 18(1), 9-13 (in Chinese with English abstract).

Sun Y.Z., Püttmann W., Kalkreuth W. and Horsfield B., 2002. Petrologic andgeochemical characteristics of Seam 9-3 and Seam 2, Xingtai Coalfield, NorthernChina. International Journal of Coal Geology 49, 251– 262.


Sun Y.Z., 2003. Petrologic and geochemical characteristics of ‘‘barkinite’’ from theDahe mine, Guizhou Province, China. International Journal of Coal Geology56, 269– 276.

Sun Y.Z. and Horsfield. B., 2005. Comparison of the Geochemical Characteristics of“Barkinite” and Other MaceralsFrom the Dahe Mine, South China. EnergyExploration & Exploitation 23 (6), 475–494.

Sun Y.Z., Liu C.Y., Lin M.Y., Li Y.H. and Qin P., 2009. Geochemical evidences ofnatural gas migration and releasing in the Ordos Basin, China. EnergyExploration & Exploitation 27(1), 1-13.

Thomas G., Nathan D., Richard J. and Chalaturny K., 2007. Geomechanical propertiesand permeability of coals from the Foothills and Mountain regions of westernCanada, International Journal of Coal Geology 69(3), 153-164.

William P.D., Steven J.S., 1998. Measuring the gas content of coal: A review.International Journal of Coal Geology 35(1-4), 311-331.

XoπoT, B.B., 1996. Coal and gas outburst mechanism. In: Song S.Z. and Wang Y.A.,(translated) Industry Press, Beijing, China (in Chinese).Yan C.Z., 2003. Simple review on coalbed gas resources of shanxi formation in

Jiaozuo coalfield and its exploitation. Coal Geology of China 15(1), 25-26 (inChinese with English abstract).

Yao Y.B., Liu D.M., Tang D.Z., Tang S.H., Che Y. and Huang W.H., 2009.Preliminary evaluation of the coalbed methane production potential and itsgeological controls in the Weibei Coalfield, Southeastern Ordos Basin, China.International Journal of Coal Geology 78(1), 1-15.

Ye J.P., Qin Y. and Lin D.Y., 1998. Coalbed methane resource in China. ChinaUniversity of Mining and Technology Press, Xuzhou, pp.197 (in Chinese).

Yuan S.Q. and Tian Z.L., 2005. Gas reservoir characteristics of II1 coal seam and CBMresource potential assessment in jiaozuo mining area, Henan. Coal Geology ofChina 17(6), 13-16.

Yuan C.F., 1985. Tectonic coal and coal and gas outburst. Gas Geology 1, 45-52(in Chinese with English abstract).

Zhang P.H., Jin X.L., Meng Z.P. and Zhao C.M., 1998. Comprehensive geologicevaluation on the coalbed methane development in jiaozuo mining district. CoalGeolog & Exploration 26(2), 22-25 (in Chinese with English abstract).

Zhang X.D., Gao Z.Q., Lu Y.D., 2008. Investigation and Evaluation report on thepotential of coalbed methane resource of Jiaozuo coalfield in Henan provience(in Chinese).

Zhang X.D., Lu Y.D. and Wang L.L., 2007. Existence characteristic of CBM inGuhanshan coalmine of Jiaozuo Coalfild. Journal of Henan PolytechincUniversity 26(1), 27-31 (in Chinese with English abstract).

Zhang X.D., 2005. Adsorption response to fractional extraction of coal and itsgeochemistry mechanism: Doctoral Thesis, China University of Mining &Technology, Xuzhou, China, pp. 263 (in Chinese).


Zhong L.W., Yuan Z.R. and Li G.H., 2004. The relationship between coal structureand permeability in main coal bearing areas in China. Coal Geology &Exploration 32(2), 77-81 (in Chinese with English abstract).


Date post:	02-May-2020
Category:	Documents
Upload:	others
View:	6 times
Download:	0 times

Coalbed methane resources and reservoir characteristics of ...197099/UQ197099_OA.pdf · ENERGY...

Documents