The Potential and Development Strategy of the Coalbed Methane 
in Guizhou Province

Bingbing Xu
(The Coalfield Geological Bureau of Guizhou Province, Anshun 561000)

1. The Coal Deposits in Guizhou Province
The total amount of coal deposits above 2000 meters of depth in Guizhou Province is more than 240 billion tons, 98% of which lies in the Permian Stratum. These coal reserves are mainly distributed in Liupanshui Coalfield, Zhina Coalfield, North Guizhou Coalfield, and Xingyi Coalfield (Figure 1). The types are mainly coking coal, lean coal, meager coal，and anthracite coal. 

Figure 1. The distribution map of the coalfields and coal deposits in Guizhou Province
I. Xingyi Coalfield; II. Liupanshui Coalfield; III. Zhina Coalfield; IV. Guiyang Coalfield; V. The Northwest Guizhou Coalfield; VI. The North Guizhou Coalfield; VII. The Northeast Guizhou Coalfield; VIII. The Southeast Guizhou Coalfield; IX. The South Guizhou (no coal deposits)

2. The Coalbed Methane Deposits in Guizhou Province
The estimated total coalbed methane deposits in the province amount to 31,511′108 m3. The coalbed methane deposits in each coalfield are summarized in Table 1. They are mainly distributed among the 15 synclinal structure units in Liupanshui, Zhina and North Guizhou Coalfileds, reaching more than 21,000′108 m3 in total (Figure 2). The overall coalbed methane deposits and geologic features in each major gasfield (i.e. structure unit) are summarized in Table 2. 

Table 1. The estimated coalbed methane gas deposits in Guizhou Province
Unit: ′108 m3
Coalfield CH438 m3/t 4 m3/t￡ CH4<8 m3/t Sum
Liupanshui 13,341 895 14,236
Zhina 7,073 538 7,611
North Guizhou 6,868 524 7,392
Xingyi 1,111 121 1,232
Guiyang 705 213 918
Northwest Guizhou 116 6 122
Total 29,214 2,297 31,511


Figure 2. The major coalbed methane gasfields in Guizhou Province (the Coalfield Geological Bureau of Guizhou Province, 1996)

Table 2. The overall coalbed methane deposits and geologic features of the major gasfields (i.e. structure unit) in Guizhou Province
Structure unit Coalbeds Explorable coalbeds Coal type CH4 content above 500 m (ml/g.r) Abundance (′108 m3/ km2)
Geologic period Thickness (m) Number of Strata / thickness (m) Number of main target strata / thickness (m) 
Panguan syncline P2 250 18/23 12/3.8 (west)QM-JM(east)PM-WY (west)13.90(east)13.55 3.24
Tucheng syncline P2 330 20/25 12/3 FM 14.86 
Jiupuan syncline P2 430 13/29 18/7 SM.PM 26.55 
Qingshan syncline P2 260 9/20 19/5.5 SM- WY 12.35 2.30
Gemudi syncline P2 426 22/27 C18/3.2 JM-PM 27.93 
Dahebian syncline P2 265 11/13 409/4.2 JM 20.55 
Langdai syncline P2 492 9/19 7/5 JM 20.30 
Liuzhi syncline P2 476 9/15 7/5.7 JM.SM 21.05 
Bulang syncline P2 421 6/7 14/1.6 WY 38.40 2.44
Caiguan syncline P2 427 3/4.8 6/1.3 WY 1.49
Bide-Santang syncline P2 399 12/21.7 6/4.2 WY 20.70 3.35
Jinlong syncline P2 240 7/10.6 6up/2.2 WY 16.85 2.03
West Guizhousyncline P2 120 4/5.2 9/1.5 WY 0.65
Piaoerjing syncline P2 200 7/7.6 6mid/1.4 WY 1.34
Zhoushiba syncline P2 140 7/10(west) 9/1.8 WY 14.65 2.07
Total 
* From Yi, Tongsheng et al, 1997 (deposit above 2,000 meters of depth).


3. Analysis on the Gas-Controlling Geological Factors
3.1 Coalbeds and Coal Formation
As the intergrowth or associated mineral of coal, the coalbed methane gas is thus controlled by the coal accumulation mechanism, including its amount and distribution. The main coalbed in this region is P2 l+c. The deposit in this stratum accounts for 98% of the total provincial coal reserves. The Liupanshui, Zhina and North Guizhou Coalfields are located at the coal accumulation centre of the Yangzi coal rich basin formed during the Late Permian Period. The total coal deposits above 2,000 meters of depth in this region are about 210 billion tons which is approximately 87% of the total provincial amount. Their reserve abundance values are 18.22, 11.34 and 4.28 Mt/km2 respectively. 

3.2 The Sedimentation History
The base rock of the coalbed is the Emei Mountain Basalt (P2 b) or the Mao Mountain Limestone (P1 m). The coal strata above it transit from the marine facies in the east to the land facies in the west. They mainly lie in the rocks that were consecutively deposited during the alternate land-marine facies, including mudstone, fine clastic rock and coal-rock mixed layer with occasionally a bit thin but hard limestone at some points. There is no obvious interruption and denudation in these rocks. The direct upper layer of the coal rich stratum is the Feixianguan (T1 f) or Yelang (T1 y) rock groups in the Late Triassic. The Feixianguan rock group, 350-700 meters thick, is the pink calcium arenaceous mudstone, mudstone with thin marl and limestone. For the Yelang rock group of 100-400 meter thick, the lower part is mudstone and pink arenaceous rock with thin mud limestone (at Shanbaowan), while its upper part is mudstone, pink arenaceous rock and coal-limestone mixed layer. The Feixianguan and Yelang rock groups and, as well, their lower coalbeds are all consecutively deposited with a good confining bed. 

3.3 The Tectonic History
After the Dongwu Tectonic movement featured as cracking and subsidence and base magma extrusion, frequent land-marine interaction happened in the East side of the Kangqian ancient land, so that there exists strong coal accumulation process in the transition zone. Marine facies fine clastic rock and terrain carbonate deposition got well developed at the start of the Indo-China Period due to the expanded marine intrusion. The late terrain arising movement ended this marine facies deposition. There is interruption between T3-J3 but the P2 rock group is not basically denuded by the ancient weathering. The K1 is normally absent and all the strata before K2 were folded due to the crustal movement (i.e. the principal period of the Yan Mountain Movement) occurred between K2 and J3, which formed the basic frame of the geologic structures in the region. The Xi Mountain Period is featured mainly by the differential terrain arising and cracking with locally light folding and strong anticlinal denudation. The coalbeds were mainly deposited in negative structures (i.e. syncline and multi-synclines), while the plateau terrain topography then formed. 

3.4 The Thermal Evolution and Hydrocarbon Generation History
The Liupanshui and East Guizhou Coalfields are the normally formed ancient earth temperature background areas. The depth of P2 and its upper strata is about 4,000 meters thick, where gas and coking coals were formed; the North Guizhou, Zhina and Southwest Guizhou Coalfields are relevant to the special location of the regional massif structures held by the Jialidong "X" fault; the North Guizhou and Zhina Coalfields are related to the terrain arising in central Guizhou, meager coal and anthracite coal formed due to the anomaly higher ancient earth temperature (5-5.50 C/100m); the Southwest Coalfield (i.e. the Xingyi Coalfield) is related to the You River folding belt, where the depth of P2 and its upper strata is over 6,000 meters thick and meager coal and anthracite coal formed due to the normal higher ancient earth temperature; the widespread middle and lower temperature hot liquid minerals and corrosion phenomena (including gold mineralization) in the early Permian stratum in the North Guizhou, Zhina and Southwest Guizhou Coalfields show that hydrocarbon formed twice due to the overlay of the Yan Mountain movement and deep magma movement, large area anthracite coal formed. 

3.5 The Regional Hydrogeologic Conditions
The Emei Mountain basalt, coalbed rocks, late Triassic Feixianguan and Yelang rocks in Shabaowang are all water isolated or weak water content strata (Table 3). For those regions with the base rock of the coalbeds as the Mao Mountain limestone, there is normally no hydraulic linkage because of the weak permeability of the upper coalbed rock although limestone is a strong karst water content layer. The overall hydrogeologic conditions are simple and belong to the rock hydraulically closed type of gasfield. 


Table 3. The hydrogeologic parameters of the early Permian stratum and its upper and lower strata in west Guizhou Province
Stratum q (l/s.m) K (m/d) M (g/l)
T1 l 0.0177-0.0490.033 0.005-0.190.097 0.2-1.10.65
P2 l 0.019-0.06380.0414 0.003-0.020.0115 0.098-0.50.299
P2 b 0.00156-0.0270.014 0.0019-0.060.031 0.03-1.20.615
* From Zuo, Jun, 2000 (unpublished material) 


4. The Potential of the Coalbed Methane Reserves and Current 
Situations of Development
4.1 The Reserve Potential
There are following advantages regarding to the coalbed methane deposits in Guizhou Province:

1) Large amount: it reaches 31,511′108 m3 which accounts for 22% of the country's total deposits (China Coalfield Geologic Bureau, 1998) and ranks the second in the country.

2) Spatially concentrated: it is dominantly distributed among the 15 coal rich synclinal structures in west Guizhou with a total deposit of 21,036′108 m3 that is 66% of the province's total.

3) Good quality: the gas rich deposit (CH438 m3/t) accounts for 94% among the total and the average abundance value of the major gasfileds reaches approximately 2′108 m3/km2.

4) Ideally located: with rich hydropower resources, high quality coal and coalbed methane deposits and adjacent to the well developed but short of energy South China (i.e. Guangdong and Guangxi Provoinces), Guizhou Province is the energy and raw material bases for the whole Southern China in the national economic development plan. Its construction of an integrated coal, hydropower and gas production network is thus of great significance to the sustainable regional economic development. 

5) Helpful to environmental protection and coal mine safety: replacing the high surphur content coal with the clean coalbed methane can help control the pollution caused by the current severe acid rain and surphur dioxide and improve the ecological environment and water and soil conservation of the Pearl River and the upper Yangtze River, and can also essentially improve the production conditions in coalmines.

Several issues concerning the coalbed methane development in Guizhou Province still need to be further studied, such as 1) multiple but thin coalbeds; 2) possibly lower regional poor permeability coalbeds due to the favorite regional tectonic environment for the formation of the structural coal after the Mesozoic Era; and 3) difficulty in exploitation and construction of surface facilities due to the rugged terrain topography, etc. 

4.2 The Current Situations of Development
There is a good base already in methane gas extraction in the state-own key coal mines in Guizhou. A gas holder of 5,000 m3 of storage was first built in Liuzhi Coal Mining Administration in 1985 and up to now has be extended to a 20,000 m3 gas storage center, supply gas to peoples living in a special zone. Domestic coalbed methane utilization projects have also been set up one after another in Shuicheng and Panjiang Coal Mining Administrations. The coalbed methane deposit evaluation in Guizhou is basically at the same level as other provinces in the country. A report on the prospective reserves and development plan of the oil and gas (include coalbed methane) deposits was completed in 1993 by the Land Resources Department of the Provincial Planning Commission. In 1996, the Guizhou coalbed methane resource assessment project was completed by the provincial Coalfield Geologic Bureau. The estimated resources based on the national technical requirement for the coalbed methane evaluation (see China Coalfield Geologic Bureau, 1995) is 31,511′108 m3. With this result as a base, the project of the coalbed methane assessment in the Panguan syncline was completed in 1997. In 1996, the Guizhou shallow natural gas survey project was approved, and afterwards the Liupanshui City coalbed methane demonstration project was implemented with five shallow natural gas wells drilled. However, the current coalbed methane geological exploitation is still in its initial stage only, which falls more than 5 years behind other provinces. 

5. Strategy of the Coalbed Methane Development in Guizhou Province
5.1 The Geological Exploitation
The top priority in Guizhou's coalbed methane development is to start geological exploitation as soon as possible, including regional survey, selected pre-exploitation and small well network exploitation. The survey scope should cover the whole west coal rich region with the emphasis on the 15 synclinal structure units. The pre-exploitation should take the target coalbeds as the basic units. Its result should meet the requirement for initial feasibility evaluation and set a geological base for the small well network exploitation, which can be started once a profitable industrial gas yield is obtained. Based on the necessary technical and economic information from the above result, commercial development can then be considered. 

5.2 The Development Arrangement
A combined extraction approach of the coalmine drainage and surface wells development is suggested, with emphasis on the surface extraction. This should be implemented jointly with those big-sized key coalmines, starting from a point and gradually expanding to a region on the base of rolling development. The possible plans at the initial stage include:

1) Undertake preliminary study at the Panjiang syncline together with the Panjiang Coal Power Company (Group).

2) Undertake preliminary study at the Gemudi syncline together with the Shuicheng Coal Mining Administration.

3) Undertake preliminary study at the Liuzhi (or Langdai) syncline together with the Liuzhi Industrial and Coal Mining Company.

It is aimed to realize an annual gas production of 5′108 m3 in about 5 years time. The coalbed methane gas extracted from coalmines can be supplied mainly to domestic users or to gas power generation plants, while the gas from surface wells can be used mainly for chemical engineering. Proper sized plants for synthetic ammonia production can be considered. This industrial chain can even also be extended to produce phosphate ammonia and other chemical products of wide market perspectives by use of Guizhou' rich phosphorus ore deposits. 

5.3 Suggestions
1) Strengthen inter-organizational Coordination. As a pair of intergrown natural deopsits, coal and coalbed methane reserves are inseparable in terms of their evaluation, exploitation and development. Therefore, they must be treated together in an integrated way. In those intensively explored coalmines where many relevant sectors are involved, the cooperation between the coal production sector and the coalfield geologic sector will be a decisive factor in the early period of the coalbed methane development. Hence it is a necessity to set up an authoritative organization to coordinate among different sectors and companies involved in the coalbed methane development. For example, the early exploitation within coalmines can be entitled to the coal production sector while the deep part to oil exploitation sector, etc. 

2) Promote Sino-foreign cooporation. In order to enlarge the opening to outside, it is implored that China United Coalbed Methane Corporation with the exclusive trading rights pay more attention to the coalbed methane development in Guizhou province and promote joint development with foreign companies. 

3) Governmental financial support. The coalbed methane development is an industry of high tech, high investment and high risk. The high risky huge capital input at the early stage, in particular, is unstandable for normal companies and must be financially supported by the central government. The central government can set a special fund to support the early coalbed methane exploitation based on the overall consideration of Guizhou's role in regional economic development and the actual demand for Guizhou's coal and coalbed methane resources in the nation's new western development strategy.