Multiple Influences of Paleogeography, Sequence Stratigraphy, and Fold Structure on Coalbed Methane Accumulation in the Lopingian (Late Permian) of Junlian Coalfield, SW China

Junlian coalfield is one of the main targets for coalbed methane (CBM) exploration and development in the southwest China. Based on field geological survey, core observation, gas content statistics, coal maceral composition, vitrinite reflectance ( R O ), proximate analysis and trace element test, lithological types, lithofacies, sedimentary environment, and structural analysis, this research established the sequence stratigraphy frame, revealed the plane distribution characteristics of sedimentary facies, and defined CBM accumulation mode. The results show that six rock types were identified and further subdivided into twenty lithofacies types. Four types of sedimentary systems such as alluvial plains, delta, lagoon-tidal flat, and carbonate platform were summarized according to their combination characteristics. Additionally, 12-14 fourth-order sequences and three third-order sequences CSI, CSII, and CSIII were divided, and a sequence stratigraphic framework of the Lopingian coal-bearing series was established. Among them, the features of third-order sequence CSIII paleogeography from west to east are alluvial plains, deltas, lagoon-tidal flats, and limited carbonate platforms. Thick coal seams are mainly developed in the sedimentary environment of tidal flats, delta plains, and floodplains behind banks. Closely related to coal seam thickness, gas contents of Lopingian coal seams are generally higher than 8 m3/t, except the low level in northwest and partial denudation areas. CBM accumulation is significantly controlled by the fold structure, and the hydraulic plugging effect makes the syncline core favorable for CBM accumulation. Furthermore, favorable geostress conditions enable the secondary anticline to become a favorable area for CBM accumulation when the sealing conditions are better. This research will provide a theoretical guide for the exploration and development of CBM in the study area.

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Study on geological controls and enrichment models of coalbed methane in the Wuwei Basin in eastern North Qilian, northwestern China

Energy Exploration & Exploitation ◽

10.1177/0144598718803693 ◽

2018 ◽

Vol 37 (1) ◽

pp. 429-452

Author(s):

Wenchao Shen ◽

Longyi Shao ◽

Wenguang Tian ◽

Gang Chen ◽

Fei Chen ◽

...

Keyword(s):

Coalbed Methane ◽

Sedimentary Environment ◽

Controlling Factors ◽

Gas Content ◽

Methane Formation ◽

Coal Seams ◽

Mineral Contents ◽

The North ◽

Taiyuan Formation ◽

Lagoon Environment

The Wuwei Basin is located in the Gansu Corridor, which has abundant coalbed methane resources of 2.75 × 1011 m3. However, a low degree of coalbed methane exploration exists, and only a few wells have been drilled in local regions due to insufficient understanding of coalbed methane enrichment and its main controlling factors. This study analyzed the controlling factors of coalbed methane enrichment, including coal reservoir characteristics, hydrogeological conditions, and the original sedimentary environment of the coal-bearing strata. The results showed that the main coal seams were developed in the Taiyuan Formation, and were mostly concentrated in the Yingpan Sag in the south and the Ermahu Sag in the north of the study area. The macrolithotype of the coals in this basin was mainly semi-bright coal with a medium to high rank. Coal macerals were mainly vitrinite, ranging between 65.1% and 91.6% (averaged 81.70%), followed by liptinite, ranging between 1.9% and 29.5% (averaged 8.82%), and inertinite, ranging between 0.2% and 16.5% (averaged 3.66%). Mineral contents varied from 2.5% to 15.1% (averaged 6.16%). The macrolithotype and microlithotype of the Taiyuan Formation coals were favorable for coalbed methane formation. Through comparative analysis of moisture content, ash yield, gas content, and coal-forming sedimentary environments, it was found that the coal formed in the lagoon environment had a higher gas content and lower ash yield than that of the coal formed in the tidal flat environment. The high contents of total dissolved solids in aquifers around coal seams (1.75–16.70 g/L) reflected the closed hydrodynamic environment and were favorable for the preservation of coalbed methane in the Yingpan Sag. Considering various controlling factors (i.e., structure, sedimentation and hydrogeology), three coalbed methane enrichment models were proposed. The model of coalbed methane enrichment in the synclinorium was the most favorable for the enrichment of coalbed methane in the Yingpan Sag.

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CBM Resources Estimations for the Development of Coal Mine Methane in the Asturian Central Basin, Spain

Proceedings ◽

10.3390/proceedings2231404 ◽

2018 ◽

Vol 2 (23) ◽

pp. 1404

Author(s):

Pablo Cienfuegos-Suárez ◽

Efrén García-Ordiales ◽

Diego Alonso-Fernández ◽

Jorge Enrique Soto-Yen

Keyword(s):

Coal Mine ◽

Coalbed Methane ◽

Technological Development ◽

Gas Content ◽

Central Basin ◽

Economic Interest ◽

Coal Seams ◽

Coal Basin ◽

Coal Mine Methane ◽

Made In

New technological development and a best knowledge of the basin allow to have justified expectation to find coalbed methane reserves. Measurements of gas content in unexploited coal seams are made in order to estimate the CBM could revive the economic interest of the Asturian Central Coal Basin (ACCB). According to first estimations based on the studies accomplished, the minimum resources of coalbed methane in the whole of the Asturian Central Coal Basin are in the order of 25,000 Mm3 and the gas content of the coal seams range from 6 m3 to 14 m3/t. The introduction should briefly place the study in a broad context and define the purpose of the work and its significance.

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Coal-bearing strata sequence stratigraphy of Paleogene Meihe Formation, Meihe Basin, NE China

International Journal of Coal Science & Technology ◽

10.1007/s40789-020-00381-6 ◽

2020 ◽

Author(s):

Yueyue Bai ◽

Qingtian Lü ◽

Zhaojun Liu ◽

Pingchang Sun ◽

Rong Liu ◽

...

Keyword(s):

Sedimentary Environment ◽

Seismic Profiles ◽

Coal Seams ◽

Third Order ◽

Sequence Stratigraphic ◽

Delta Plain ◽

Accommodation Space ◽

Geochemical Properties ◽

Stratigraphic Framework ◽

System Tracts

AbstractThe Meihe Basin is an important Paleogene coal-bearing basin located in the Dunhua-Mishan Fault Zone, northeastern China. Based on a comprehensive study of well logs, seismic profiles, cores and rock geochemical properties, the coal distribution, paleoenvironment evolution within a sequence stratigraphic framework and the accumulation model to explain how coal seams developed in small fault basin were discussed in detail. Three-third-order sequences were identified in the Paleogene Meihe Formation of Meihe Basin and the two coal-bearing sequences are the Lower Coal-bearing Member of Sequence I and the Upper Coal-bearing Member of Sequence III. All three types of system tracts are developed in both sequences, i.e., the lowstand systems tract (LST), the transgressive systems tract (TST), and the highstand systems tract (HST). In LST of Sequence I, fan delta plain marsh is the main coal accumulating environment where coal seams are thin, discontinuous and therefore uneconomic for mining, and it is the same with all coal seams developed in Sequence III. While in TST and HST of Sequence I, lake swamp is the main sedimentary environment where coal seams are thick, continuous, widely distributed, and thus economically attractive for mining. In the study area, the nice thick economical coal seams are usually developed in an ideal stable depositional environment where organic matter accommodation space grows at a balanced rate with peat, in other words, free of sediment input or channel migration. The key findings of this study could provide guidance for the exploration of coal seams in the Meihe Basin and other similar basins.

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A Study on the Heterogeneity Characteristics of Geological Controls on Coalbed Methane Accumulation in Gujiao Coalbed Methane Field, Xishan Coalfield, China

Geofluids ◽

10.1155/2021/6629758 ◽

2021 ◽

Vol 2021 ◽

pp. 1-20

Author(s):

Taotao Yan ◽

Shan He ◽

Yadong Bai ◽

Zhiyong He ◽

Dameng Liu ◽

...

Keyword(s):

Coalbed Methane ◽

Large Scale ◽

Gas Content ◽

Hydrocarbon Generation ◽

Burial History ◽

Gas Distribution ◽

Coal Seams ◽

Gas Generation ◽

Himalayan Orogeny ◽

Coal Reservoir

Commercial exploration and exploitation of coalbed methane (CBM) in Gujiao coalbed methane (CBM) field, Xishan coalfield, have rapidly increased in recent decades. The Gujiao CBM field has shown strong gas distribution heterogeneity, low gas content, and wide distribution of wells with low production. To better understand the geological controlling mechanism on gas distribution heterogeneity, the coal reservoir evolution history and CBM accumulation process have been studied on the base of numerical simulation work. The burial history of coal reservoir can be classified into six stages: shallowly buried stage; deeply buried stage; uplifting stage; short-term tectonic subsidence stage; large-scale uplifting stage; and sustaining uplifting and structural inversion stage. Mostly, coal seams have experienced two-time thermal metamorphisms with twice hydrocarbon-generation processes in this area, whereas in the southwest part, the coal seams in there suffered three-time thermal metamorphisms and hydrocarbon-generation processes. The critical tectonic events of the Indosinian, Yanshanian, and Himalayan orogenies affect different stages of the CBM reservoir accumulation evolution process. The Indosinian orogeny mainly controls the primary CBM generation. The Yanshanian orogeny dominates the second and third gas generation and migration processes. The Himalayan orogeny mainly affects the gas dissipation process and current CBM distribution heterogeneity.

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Coal-bearing strata sequence stratigraphy of Paleogene Meihe Formation, Meihe Basin, NE China

10.21203/rs.3.rs-22238/v3 ◽

2020 ◽

Author(s):

Yueyue Bai ◽

Qingtian Lü ◽

Zhaojun Liu ◽

Pingchang Sun ◽

Rong Liu ◽

...

Keyword(s):

Sedimentary Environment ◽

Seismic Profiles ◽

Coal Seams ◽

Third Order ◽

Sequence Stratigraphic ◽

Delta Plain ◽

Accommodation Space ◽

Geochemical Properties ◽

Stratigraphic Framework ◽

System Tracts

Abstract The Meihe Basin is an important Paleogene coal-bearing basin located in the Dunhua-Mishan Fault Zone, northeastern China. Based on a comprehensive study of well logs, seismic profiles, cores and rock geochemical properties, the coal distribution, paleoenvironment evolution within a sequence stratigraphic framework and the accumulation model to explain how coal seams developed in small fault basinsw were discussed in detail. Three third-order sequences were identified in the Paleogene Meihe Formation of Meihe Basin and the two coal-bearing sequences are the Lower Coal-bearing Member of Sequence I and the Upper Coal-bearing Member of Sequence III. All three types of system tracts are developed in both sequences, i.e., the lowstand systems tract (LST), the transgressive systems tract (TST), and the highstand systems tract (HST). In LST of Sequence I, fan delta plain marsh is the main coal accumulating environment where coal seams are thin, discontinuous and therefore uneconomic for mining, and it is the same with all coal seams developed in Sequence III. While in TST and HST of Sequence I, lake swamp is the main sedimentary environment where coal seams are thick, continuous, widely distributed, and thus economically attractive for mining. In the study area, the nice thick economical coal seams are usually developed in an ideal stable depositional environment where organic matter accommodation space grows at a balanced rate with peat, in other words, free of sediment input or channel migration. The key findings of this study could provide guidance for the exploration of coal seams in the Meihe Basin and other similar basins.

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Geological Characteristics of Coalbed Methane Reservoir in Southern Shizhuang Block, Southeastern Qinshui Basin

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.295-298.3209 ◽

2013 ◽

Vol 295-298 ◽

pp. 3209-3212

Author(s):

Li Ren Xing ◽

Yan Bin Yao ◽

Da Meng Liu ◽

Jun Gang Liu ◽

Lu Lu Zhou ◽

...

Keyword(s):

Coal Seam ◽

Local Structure ◽

Coalbed Methane ◽

Simple Structure ◽

Gas Content ◽

Burial Depth ◽

Coal Seams ◽

Structure Characteristics ◽

Geological Characteristics ◽

Coalbed Methane Reservoir

Southern Shizhuang Block has simple structure characteristics, relatively thick coal seams (3.1-10.5 m, 6 m in average), and favorable burial depth (450-900 m). The gas content of the No.3 coal seam in the Shanxi formation ranges from 6-20 m3/t, and it increases from the southeast to northwest area in the southern Shizhuang Block. Gas content is high in the structural low in the area, which means the gas accumulation is controlled by the geological characteristics of local structure and hydrogeologic conditions.

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Productivity subarea of CBM field and its key controlling factors: A case study in the Hancheng pilot test area, southeastern Ordos Basin, China

Energy Exploration & Exploitation ◽

10.1177/0144598718798091 ◽

2018 ◽

Vol 37 (1) ◽

pp. 102-124 ◽

Cited By ~ 1

Author(s):

Yanfei Liu ◽

Dazhen Tang ◽

Song Li ◽

Hao Xu ◽

Shu Tao ◽

...

Keyword(s):

Coalbed Methane ◽

Ordos Basin ◽

Gas Production ◽

Test Area ◽

Gas Content ◽

Pilot Test ◽

Coal Seams ◽

Geological Factors ◽

Drop Rate

The Hancheng block in the southeastern Ordos Basin is one of the earliest and the most important areas for coalbed methane exploration and development in China. However, there are significant production variations in different wells or even some adjacent wells in the Hancheng block. To reveal the reasons of production differences in such a small scale, further detailed studies of coalbed methane productivity in the Hancheng pilot test area, a precursor trial area in Hancheng block with mature, well-characterized coalbed methane reservoirs and long-term production database, were conducted. The influence of nine factors (including engineering and geological factors) on gas production was analyzed. By introducing the rough set theory, which is applicable to the vague, imprecise, and incomplete information system, this paper presents a method for quantitative evaluation of the influencing factors on gas production. The results indicate that there are certain distribution characteristics of productivity in Hancheng pilot test area, which can be partitioned into four zones. The degressive order of the influencing degree of these nine factors is (i) the distance between the well and the fault, (ii) the structure curvature of the coal seams, (iii) the gas content, (iv) the critical reservoir ratio, (v) the volume of the fracturing liquids per meter, (vi) the volume of the fracturing sand per meter, (vii) the dynamic liquid level drop rate, (viii) the depth, and (ix) the thickness. Geological factors, especially the influence of fault, structural curvature of the coal seams and gas content, play a major role in controlling long-term gas production. Engineering factors (effect of fracturing and dynamic liquid level drop rate) have always been integral parts of coalbed methane development.

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Technologies extraction of coalbed methane in the Qinshui basin of China

Moscow University Bulletin. Series 4. Geology ◽

10.33623/0579-9406-2018-6-102-108 ◽

2018 ◽

pp. 102-108

Author(s):

Lu Yanjun ◽

Han Jinxuan ◽

V. V. Shelepov ◽

E. Yu. Makarova ◽

Li Kai ◽

...

Keyword(s):

Coalbed Methane ◽

Electric Pulse ◽

Gas Content ◽

Low Permeability ◽

Reservoir Pressure ◽

Vertical Wells ◽

Coal Seams ◽

Qinshui Basin ◽

Multi Stage ◽

Total Resource

Coalbed methane (CBM) is a new clean and unconventional energy that has broad space for development. In Qinshui basin, CBM reserves reach 3,97·1012m3, which is 10,8% of the total resource in China. Compared to the main coal basins of USA, Australia, Canada and Russia, coal seams in Qinshui basin have the characteristics of high metamorphism, high gas content, low porosity, low permeability and low reservoir pressure. Therefore, effective stimulation treatments must be used in Qinshui basin to realize industrial exploitation of CBM. At present, vertical wells with hydraulic fracturing are dominated in Qinshui basin. In addition, injection CO2, electric pulse, multi-stage fracturing and other technologies are also applied to the CBM exploitation.

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