Coalbed methane system potential evaluation and favourable area prediction of Gujiao blocks, Xishan coalfield, based on multi-level fuzzy mathematical analysis

Wang, Gang; Qin, Yong; Xie, Yiwei; Shen, Jian; Zhao, Liang; Huang, Bo; Wen-qiang, Zhao

doi:10.1016/j.petrol.2017.10.042

Cited by 44 publications

(33 citation statements)

References 34 publications

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“…The Gujiao block has a CBM reserve of 82 billion m 3 (Mo et al., 2012). At present, a total of 400 CBM wells in the Gujiao block have been put into production, and the average production capacity of these wells is close to the average for all Chinese CBM wells, although the production capacities of individual CBM wells vary significantly (Mo et al., 2012; Wang et al., 2018a).…”

Section: Geological Settingmentioning

confidence: 99%

“…Prediction and evaluation of high-quality CBM reservoirs is dependent on how the major parameters and prediction methods are chosen. Previous studies reported that the CBM content, permeability, coal seam thickness, reservoir pressure gradient, and hydrogeological conditions are major qualitative or quantitative parameters for CBM reservoir evaluation (Wang et al., 2018a; Zhang et al., 2016), but a key geological factor, coal structure, has been neglected in these studies. As a key geological factor for CBM reservoir evaluation, quantitative identification of the coal structure is necessary for the prediction of high-quality CBM reservoirs (Bai et al., 2012).…”

Section: Introductionmentioning

confidence: 99%

“…For example, the differences between the mechanical properties of the coal and those of the roof and floor fuzzily correspond to other geological factors. Using fuzzy mathematical methods, contradictory geological factors can be transformed into compatible geological factors (Wang et al., 2018a; Yao et al., 2009). Gray system theory focuses on the study object with definite extension and ambiguous intension (Ning and Duan et al., 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Stratigraphic column of the Permo-Carboniferous coal-bearing strata in the Gujiao blocks (modified fromWang et al, 2018a).…”

mentioning

confidence: 99%

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Prediction of high-quality coalbed methane reservoirs based on the fuzzy gray model: An investigation into coal seam No. 8 in Gujiao, Xishan, North China

Huang

Qin

Zhang

et al. 2020

Energy Exploration & Exploitation

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Coalbed methane (CBM) resources are abundant in the Gujiao block, Xishan coalfield, China. However, few studies have been conducted on the coalbed methane geology of the Gujiao block. In the present study, based on logging responses and numerical simulations, the coal structures of coal seam No. 8 of this block were identified, and the mechanical properties of the coal and its roof/floor were calculated. The geological factors influencing the coalbed methane reservoir were quantitatively characterized according to the fuzzy gray model. High-quality coalbed methane reservoirs in the No. 8 coal were predicted and classified using the model, and some suggestions on rational exploitation were determined. Reservoirs of the No. 8 coal are dominated by the III-type, followed by the II- and IV-types. The III-type reservoirs are the most common, and primarily developed at the Xiqu, Zhenchengdi, Malan, and Tunlan coal mines in the north of the studied area. The III-type reservoirs represent low coalbed methane contents, high thickness proportions of granulated-mylonitized coal, and low burial depths. The II-type reservoirs are primarily developed close to the axis of the Malan syncline and in the south and northwest of the studied area, and have low permeability, less significant differences between the mechanical properties of coals and their roofs and floors, and low reservoir pressure gradients. The IV-type reservoirs have a scattered development, dominance of granulated-mylonitized coal, and low permeability, indicating low potential to improve reservoir permeability. Targeted exploitation technology and drainage systems corresponding to the different types of coal reservoirs should be proposed to improve coalbed methane production.

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Section: Geological Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Stratigraphic column of the Permo-Carboniferous coal-bearing strata in the Gujiao blocks (modified fromWang et al, 2018a).…”

mentioning

confidence: 99%

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Prediction of high-quality coalbed methane reservoirs based on the fuzzy gray model: An investigation into coal seam No. 8 in Gujiao, Xishan, North China

Huang

Qin

Zhang

et al. 2020

Energy Exploration & Exploitation

Self Cite

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show abstract

“…During coalbed methane (CBM) exploration and development, the reservoir petrophysical properties, particularly the permeability, are crucial for potential and productivity evaluation of CBM resources . The low‐permeability characteristic of coal reservoirs in China requires reservoir stimulation during CBM exploitation.…”

Section: Introductionmentioning

confidence: 99%

Postfracturing permeability prediction for CBM well with the analysis of fracturing pressure decline

Zhang

Wang

et al. 2019

Energy Science & Engineering

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Hydraulic fracturing is a widely used reservoir stimulation technique to exploit CBM in China. Compared with the original permeability of coal reservoir, the postfracturing permeability is more critical for the productivity evaluation of CBM wells. Based on hydraulic fracturing, microseismics monitoring, and well test data of the CBM wells in Zhengzhuang block of Qinshui Basin, this paper proposes a simple method to obtain the fitting pressure by the classic fracturing pressure decline analysis theory under the condition of corrected dynamic overall leakoff coefficient. In addition, the postfracturing permeability of coal reservoir is predicted by the injection well testing theory. The morphology of hydraulic fractures in the study area is mainly determined by in‐situ stress, and most fractures are vertical ones propagating along the direction of the maximum principal stress. The fracturing curves of the study area can be classified into stable curves, stably fluctuating curves, descending curves, ascending curves, and fluctuating curves, where the stable and descending fracturing curves represent better fracturing effect. The length of hydraulic fractures is much greater than the height. The PKN model has been selected as the hydraulic fracture propagation model to analyze the fracturing pressure decline. The slope value of liner segment of G(δ,0) curve is proposed as the criterion for the fitting pressure calculation. The postfracturing permeabilities of coal reservoir range from 1.55 to 8.83 × 10−3 μm2, all of which are remarkably higher than that of the original reservoir.

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Evaluation of closed gob methane sweet spots: A case study of the Tiefa mining area

Wang

Huang

Sang

et al. 2020

Energy Science & Engineering

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The coal seam gas development in closed gob zone is still in the exploratory stage in China, and potential evaluation and sweet spots selection are the key issues. This paper establishes a complete evaluation system for selecting sweet spots for closed gob methane extraction with surface wells in the Tiefa mining area to reduce the blindness of area selection. The one‐vote veto system, the comprehensive evaluation index system, and the AHP‐entropy combined weight model are used to screen and evaluate the closed gob zones in the Tiefa mining area. A total of twenty evaluation units are evaluated and the development potential of which is classified as three levels by the optimal segmentation method. The relationship between the results of the assessment and the closed gob methane resource is also discussed, as well as the combined weight distribution coefficient. The results show that the development potential of the block cannot be estimated simply by the closed gob methane resource because the consistency between the comprehensive evaluation value and the closed gob methane resource is poor. The size of the combined weight distribution coefficient has little effect on the comprehensive evaluation values and only affects the ranking of evaluation units in a small range.

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Coalbed methane system potential evaluation and favourable area prediction of Gujiao blocks, Xishan coalfield, based on multi-level fuzzy mathematical analysis

Cited by 44 publications

References 34 publications

Prediction of high-quality coalbed methane reservoirs based on the fuzzy gray model: An investigation into coal seam No. 8 in Gujiao, Xishan, North China

Prediction of high-quality coalbed methane reservoirs based on the fuzzy gray model: An investigation into coal seam No. 8 in Gujiao, Xishan, North China

Postfracturing permeability prediction for CBM well with the analysis of fracturing pressure decline

Evaluation of closed gob methane sweet spots: A case study of the Tiefa mining area

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