Preliminary evaluation of the coalbed methane production potential and its geological controls in the Weibei Coalfield, Southeastern Ordos Basin, China

Yao, Yanbin; Liu, Dameng; Tang, Dazhen; Tang, Shuheng; Yao, Che; Huang, Wenhui

doi:10.1016/j.coal.2008.09.011

Cited by 189 publications

(91 citation statements)

References 29 publications

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“…In a recent research, Liu (2007) and Huang (2008) found that gas content is linear with coal rank in terms of the maximun vitinite reflectance (R o,max ). Yao et al (2009b) researched four coal types (that is bright, semi-bright, semi-dull and dull coals) and revealed that the Langmuir volume (V L ) of those coals followed a "V-shaped" correlation with increasing coal rank. Considering that the coal rank increasing as the coal seam buried depth increasing, gas content will increase with increased coal buried depth.…”

Section: Coal Rankmentioning

confidence: 99%

Vertical Diversity of Coalbed Methane Content and its Geological Controls in the Qingshan Syncline, Western Guizhou Province, China

Qin

Gao

et al. 2012

Energy Exploration & Exploitation

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The distribution of methane content in the coalbed is complex in the Qinshan Syncline of western Guizhou Province. Analyses of factors controlling on the distribution of gas content are made in this paper. Coal ranks and geo-structure in the region showed strong controls on the gas distribution. Coals with higher degree of metamorphism or located in syncline most likely have higher gas content. With the concept of coalbed methane content unite thickness (CBMCUT), those factors such as coal seam buried depth and coal structure present positive relations with gas content. Results indicated that the variation of CBMCUT is not fixed in different research areas or in different coal structures. Namely, the variation follows "v-shaped" correlation with the increasing coal buried depth in the region of Qinshan Syncline. However, the trend is smooth for the coals in the Panzhuang mining area. Usually, the critical value for primary-texture coal and mylonitized is different based on the analysis of the relationship between coal structure and CBMCUT in those two areas described above. The value is commonly higher in mylonitized coal and lower in those mainly primary-texture and fragmented coals.

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Section: Coal Rankmentioning

confidence: 99%

Vertical Diversity of Coalbed Methane Content and its Geological Controls in the Qingshan Syncline, Western Guizhou Province, China

Qin

Gao

et al. 2012

Energy Exploration & Exploitation

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“…The distribution of coal gas in the same coal seam may vary greatly even at the same depth. The changes in load stress and fracture systems in coal masses by geological structures (Li et al, 2003;Han et al, 2012) are one factor controlling the migration of coal gas and the consequent distribution of coal gas (Pashin, 1998;Ayers, 2002;Yao et al, 2009;Groshong et al, 2009;Cai et al, 2011). These changes created conditions conducive to outbursts, particularly largescale outbursts backed by tremendous amounts of energy stored in the gas.…”

Section: Abnormal Presence Of Coal Gas and Associated Geologic Structmentioning

confidence: 99%

An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas

Wang

2014

Nat. Hazards Earth Syst. Sci.

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Abstract. Large-scale coal and gas outbursts pose a risk of fatal disasters in underground mines. Large-scale outbursts (outburst of coal and rock greater than 500 t) in recent years in China indicate that there is abundant gas in areas of outbursts containing large amounts of potential energy. The adequate sealing properties of the roof and floor of a coal seam are required for local abundant gas around the site of an outburst, but an annular low-permeability zone in a coal seam, which prevents the loss by gas migration through the coal seam itself, is also required. The distribution of coal gas with this annular zone of low permeability is described, and it is proposed that the annular zone of low permeability creates conditions for confining the coal gas. The effect of this lowpermeability zone on the gas distribution is analyzed after allowing for simplifications in the model. The results show that the permeability and length of the low-permeability zone have a great impact on the gas distribution, and the permeability is required to be several orders of magnitude less than that of normal coal and enough length is also in demand. A steep gradient of gas pressure in the low-permeability zone and the high-pressure gas in the abundant zone of gas can promote coal mass failure and coal wall deformation, thereby accelerating the coal and gas outburst. The high-pressure gas in abundant zone of gas will lead to a large-scale outburst if an outburst occurs.

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“…Thus, unsaturated CBM reservoirs refer to those reservoirs in which gas content is less than their maximum gas adsorption in the reservoir conditions. Most coal reservoirs can be substantially unsaturated with thermogenic gas [45][46][47][48][49][50][51][52][53][54][55][56][57][58]. Gas saturation of coal reservoirs in the Weibei CBM field ranges from 39.2%~87.2% [55,56].…”

Section: Recovery Mechanism Of Unsaturated Cbm Reservoirsmentioning

confidence: 99%

“…Additionally, the third Klinkenberg effect has seldom been considered in permeability variation of the recovery of CBM reservoirs. It is widely thought that coal can be substantially unsaturated with thermogenic gas if not augmented by hydrocarbon migration or late-stage bacterial methanogenesis [45][46][47][48][49][50][51][52][53][54][55][56][57][58]. In consideration of this fact, we improved the existing permeability models in this paper to make them more suitable for describing permeability dynamic variation in unsaturated CBM reservoirs based on the production performance of those reservoirs, and discuss the sensitivity of various parameters, including the gas content, initial reservoir pressure, Langmuir volume and pressure, Poisson's ratio, Young's modulus, Langmuir strain, and Klinkenberg coefficient, to permeability dynamic variation in the recovery of unsaturated CBM reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Permeability Variation Models for Unsaturated Coalbed Methane Reservoirs

Tang

et al. 2015

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-A large number of models have been established to describe permeability variation with the depletion of reservoir pressure to date. However, no attempt has been made to draw enough attention to the difference in the effect of various factors on permeability variation in different production stages of unsaturated CoalBed Methane (CBM) reservoirs. This paper summarizes the existing and common permeability models, determines the relationship between various effects (effective stress effect, matrix shrinkage effect and Klinkenberg effect) and desorption characteristics of the recovery of unsaturated CBM reservoirs, then establishes two improved models to quantificationally describe permeability variation, and finally discusses the effects of various factors (gas saturation, cleat porosity, Poisson's ratio and shrinkage coefficient) on permeability variation. The results show that permeability variation during the recovery of unsaturated CBM reservoirs can be divided into two stages: the first one is that permeability variation is only affected by the effective stress effect, and the second is that permeability variation is affected by the combination of the effective stress effect, matrix shrinkage effect and Klinkenberg effect. In the second stage, matrix shrinkage effect and Klinkenberg effect play much more significant role than the effective stress effect, which leads to an increase in permeability with depletion of reservoir pressure. Sensitivity analysis of parameters in the improved models reveals that those parameters associated with gas saturation, such as gas content, reservoir pressure, Langmuir volume and Langmuir pressure, have a significant impact on permeability variation in the first stage, and the important parameters in the second stage are the gas content, reservoir pressure, Langmuir volume, Langmuir pressure, Poisson's ratio, Young's modulus and shrinkage coefficient during the depletion of reservoir pressure. A comparative study of the improved models indicates that the improved SD model has a greater sensitivity to various parameters than the improved PM model and the improved models describe permeability dynamic variation more exactly than the original ones.Résumé -Modèles de variation de perméabilité pour des réservoirs de gaz de houille insaturé -Un grand nombre de modèles ont été établis à ce jour pour décrire la variation de perméabilité en fonction de l'épuisement de la pression du réservoir. Toutefois, aucune tentative n'a été faite pour attirer suffisamment l'attention sur la différence d'effet des différents facteurs sur la variation de perméabilité dans différentes phases de production des réservoirs de gaz de houille insaturés (CoalBed Methane, CBM). Le présent article résume les modèles de perméabilité existants et usuels, détermine la relation entre les différents effets (effet de contrainte effective, effet du rétrécissement

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Preliminary evaluation of the coalbed methane production potential and its geological controls in the Weibei Coalfield, Southeastern Ordos Basin, China

Cited by 189 publications

References 29 publications

Vertical Diversity of Coalbed Methane Content and its Geological Controls in the Qingshan Syncline, Western Guizhou Province, China

Vertical Diversity of Coalbed Methane Content and its Geological Controls in the Qingshan Syncline, Western Guizhou Province, China

An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas

Permeability Variation Models for Unsaturated Coalbed Methane Reservoirs

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