Coalbed methane enrichment model of low-rank coals in multi-coals superimposed regions: a case study in the middle section of southern Junggar Basin

Hou, Haihai; Liang, Guodong; Shao, Longyi; Tang, Yue; Mu, Guangyuan

doi:10.1007/s11707-021-0917-6

Cited by 25 publications

(15 citation statements)

References 39 publications

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“…13, it was 1.723 m 2 /g (a difference of more than 20 times). Therefore, factors other than the coal macrolithotype (e.g., degree of metamorphism, pore filling, primary structure, and later structure) can also affect coal pore structures. ,, …”

Section: Discussionmentioning

confidence: 99%

Coal Macrolithotype Distribution and Its Genetic Analyses in the Deep Jiaozuo Coalfield Using Geophysical Logging Data

et al. 2021

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Coal macrolithotypes are closely correlated with coal macerals and pore–fracture structures, which greatly influence the changes in gas content and the coal structure. Traditional macrolithotype identification in coalbed methane (CBM) wells mostly depends on core drilling observation, which is expensive, time-consuming, and difficult for broken core extraction. Geophysical logging is a quick and effective method to address this issue. We obtained coal cores from 75 wells in the deep regions of the Jiaozuo Coalfield, northern China, quantitatively analyzed the logging cutoff number corresponding to various macrolithotypes, and established natural γ (GR), deep lateral resistivity (LLD), and γ–γ log (GGL) response rules for each coal macrolithotype. The formation mechanisms of different coal macrolithotypes are discussed from the perspective of coal facies and pore structures. The results show that GGL decreased but GR and LLD increased from bright coal to dull coal. Most coal macrolithotypes can be distinguished based on the established thresholds of various logging curves. However, excessively high or low ash yields significantly affect the validity of identification. The vertical coal macrolithotypes attributed to the peat marsh environment in Shanxi Formation mostly comprise three to six sublayers; dull or semi-dull coals are predominant close to the 2 1 coal seam, and the bright or semi-bright types usually appear in the middle part. The semi-bright and bright coals are usually vitrinite rich, whereas the semi-dull and dull coals are primarily inertinite rich. For pore structure arguments, the highest average specific surface area ( S BET ) and the total pore volume ( V BJH ) are found in bright coals, followed by dull and semi-bright coals; those of semi-dull coals are the lowest. However, S BET and V BJH change significantly for different samples, even though the coal macrolithotype is the same. Therefore, the macrolithotype is not the key factor determining the coal parameters of pore structures. Rapid and effective identification of coal macrolithotypes can help determine the CBM enrichment area, the CBM well location, and the exploration horizon.

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Section: Discussionmentioning

confidence: 99%

Coal Macrolithotype Distribution and Its Genetic Analyses in the Deep Jiaozuo Coalfield Using Geophysical Logging Data

et al. 2021

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“…The caprock might play more important roles in CBM accumulation than other sedimentary factors. 15 The sedimentary environment of the Taiyuan and Shanxi formations changed gradually from the tidal flat�lagoon and delta facies to fluvial facies. This variation creates distinguishable reservoir−caprock combinations, resulting in different sealing capabilities.…”

Section: Influence Of the Sedimentary Rock Sequence On Cbm Preservati...mentioning

confidence: 99%

“…7,8 China has made great progress in the CBM accumulation mechanism and development methods, such as in the Ordos Basin, 9−11 Qinshui Basin, 12,13 Basin. 14,15 However, to achieve China's goal of carbon neutrality by 2060, the scale of CBM development in China still needs to be urgently upgraded. Some areas with a low priority for exploration become the current focus of the investigation, such as the Zhuozishan coalfield at the western margin of the Ordos Basin.…”

Section: Introductionmentioning

confidence: 99%

Coalbed Methane Enrichment Characteristics and Exploration Target Selection in the Zhuozishan Coalfield of the Western Ordos Basin, China

et al. 2022

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The Zhuozishan coalfield at the western margin of the Ordos Basin is one of the main coal-mining areas in China, and recent explorations have revealed the great potential for coalbed methane (CBM) resources in its Carboniferous and Permian strata. In this paper, the controlling factors of CBM enrichment of the major coals are studied in this coalfield and the CBM resources are estimated based on the analysis of the coal petrology and compilation of literature data on the gas content. The result of the coal petrology analysis of 10 samples shows that the vitrinite content of No. 16 coal (71.9–77.3%) is higher than that of No. 9 coal (59.1–65.1%), and the inertinite content of No. 16 coal (18.9–23.5%) is lower than that of No. 9 coal (30.1–34.9%). The R o,max value of No. 16 coal (1.18–1.35%) is higher than that of No. 9 coal (1.04–1.13%), and both coals are of medium rank. Due to greater thickness, deeper burial depth, and better coal petrology characteristics, the No. 16 coal seam of the Taiyuan Formation is selected as the major coal seam for CBM resource estimation, which has a thickness of 1–6 m and a present-day burial depth of 200–1100 m. The gas content of this coal seam varies mostly between 4 and 10 m3/t. Positive correlation between the coal seam thickness as well as present-day burial depth and the gas content suggests that the thick and deeply buried coal seams are favorable for CBM preservation. The ash yield shows an insignificant negative correlation with the gas content, indicating that ash yield is not an important factor for CBM enrichment. The syncline hinges located below the thrust zones show higher gas content due to greater burial depths. In contrast, the anticline hinges at shallower depths tend to have lower gas contents. Based on the combined information about sedimentary environments, structural patterns, and hydrogeology, two CBM accumulation models are put forward in the study area that include synclinehydraulic plugging below thrust nappe and faultconfined aquifer plugging. The volumetric method is used to estimate the CBM resources, and results indicate that the CBM resource in the whole coalfield is 428.78 × 108 m3, and the total resource abundance is 0.74 × 108 m3/km2. Two favorable areas for the CBM exploration are optimized based on the resource amount and resource abundance. One of the favorable areas is the Kabuqi area in the northern part of the coalfield, and another is the Baiyunwusu area in the central part of the coalfield. These two areas will be the CBM priority exploration areas at the western margin of the Ordos Basin.

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“…Gas prevention is an important guarantee for safe and efficient production in mines, and as the mining depth increases, coal mining will face more and more gas prevention problems in the future. − At present, various technologies have been developed for gas extraction, such as coal seam preextraction, pressure relief gas drainage in the adjacent layer, bottom drainage roadway extraction, high alley pumping extraction, high level borehole extraction, goaf buried pipe extraction, large diameter drilling extraction, and so forth. The gas drainage technology and gas migration law complement each other. − Thick and high-gas coal seams are widespread in the United States, Australia, and China. − However, there are a few pieces of research on the gas extraction technology for slice mining of extra-thick coal seams that need to be carried out.…”

Section: Introductionmentioning

confidence: 99%

Research on Gas Extraction and Cut Flow Technology for Lower Slice Pressure Relief Gas under Slice Mining of Extra-thick Coal Seam

Shi

Hao

et al. 2022

ACS Omega

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For extra-thick coal seams, slice mining is a safer mining method than top coal mining, which can effectively reduce the strong mine pressure behavior caused by mining. However, in the slice mining of high-gas and extra-thick coal seams, the gas in the lower slice flows into the goaf, which increases the gas control difficulty on the upper slice working face. It is easy to cause the gas transfinite at the upper corner in the upper slice and reduce the mining efficiency. Therefore, it is of a great significance to carry out the research on gas control technology in slice mining of the extra-thick coal seam. There are some problems in the gas control of slice mining, such as a single gas control method, low control efficiency, and unclear gas migration law. Therefore, it is necessary to study the gas migration law and propose a targeted prevention and control the technical scheme. In order to improve the gas control efficiency of the extra-thick coal seam, the evolution law of permeability of the lower slice is obtained under mining through experimental research. The liquid–solid coupling seepage-flow model for gas migration is established in the lower slice. Comsol Multiphysics software is used to study the migration law of pressure relief gas in the lower slice. Based on the gas migration law, the gas extraction and cut flow technology for the lower slice long borehole is proposed. Through this technology, the amount of gas flowing into the upper slice goaf and the gas content of the lower slice are reduced, and the drilling horizon is optimized. The research results show that the determination of the optimal drilling horizon of the lower slice needs to balance the amount of gas flowing into the goaf and the total amount of gas extraction. The range of 3–7 m horizon in the lower slice is appropriate to the boreholes arranged. When the borehole is located in the lower slice −3 m horizon, the 360 day gas emission quantity of goaf can be reduced to 51.2% of the nondrilled emission quantity, and the total extraction amount is 1143 m 3 . When the borehole is located in the lower slice −7 m horizon, the 360 day gas emission quantity of goaf can be reduced to 95.31% of the nondrilled emission quantity, and the total extraction amount is 1461 m 3 . Considering the gas emission capacity of the upper slice and ensuring that the total extraction volume of the lower slice is maximized and the boreholes in the lower slice are not damaged, the boreholes are located in the −6 m horizon of the lower slice.

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Coalbed methane enrichment model of low-rank coals in multi-coals superimposed regions: a case study in the middle section of southern Junggar Basin

Cited by 25 publications

References 39 publications

Coal Macrolithotype Distribution and Its Genetic Analyses in the Deep Jiaozuo Coalfield Using Geophysical Logging Data

Coal Macrolithotype Distribution and Its Genetic Analyses in the Deep Jiaozuo Coalfield Using Geophysical Logging Data

Coalbed Methane Enrichment Characteristics and Exploration Target Selection in the Zhuozishan Coalfield of the Western Ordos Basin, China

Research on Gas Extraction and Cut Flow Technology for Lower Slice Pressure Relief Gas under Slice Mining of Extra-thick Coal Seam

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