COALBED METHANE RESOURCES IN THE PERMIAN OF EASTERN AUSTRALIA AND THEIR TECTONIC SETTING

The Bowen and Sydney Basins in eastern Australia contain vast coal resources which provide a source for coalbed methane. Through studies of the spatial and temporal distribution of the sedimentary packages, the structural geometry and tectonic setting of the sedimentary packages, and the maturation and burial history, the Australian Geological Survey Organisation (AGSO) is mapping the distribution and structural styles of the sources of methane, in particular, the Late Permian coal measures. AGSO's results from the Bowen Basin show at least two distinctly different structural styles of potential targets for coalbed methane drainage: on the Comet Ridge, the Permian coal measures are essentially subhorizontal and tectonically undisturbed, whereas in the western Taroom Trough, the coal measures are folded into a series of anticlines, each of which occurs above a thrust fault which in turn forms part of an imbricate thrust fan. Both of these styles occur at depths of less than 1000 m.Calculations by the Bureau of Resource Sciences (BRS) indicate that the inferred coalbed methane resources-in-place are 62 trillion cubic feet (1760 billion m3) for Australia, in which the Bowen and Sydney Basins are currently the only potential provinces of coalbed methane. The low permeability of the coal seams hinders attempts to utilise this vast amount of energy resources.Further exploration is necessary to delineate commercially feasible areas. This delineation is the only process that will be able to determine demonstrated coalbed methane resources.

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Environmental Risk Related to the Exploration and Exploitation of Coalbed Methane

Energies ◽

10.3390/en13246537 ◽

2020 ◽

Vol 13 (24) ◽

pp. 6537

Author(s):

Barbara Uliasz-Misiak ◽

Jacek Misiak ◽

Joanna Lewandowska-Śmierzchalska ◽

Rafał Matuła

Keyword(s):

Coalbed Methane ◽

Environmental Risks ◽

Risk Category ◽

Burial History ◽

Exploration And Exploitation ◽

Coal Seams ◽

Mining Operations ◽

Environmental Threats ◽

And Migration ◽

Coal Macerals

In coal seams, depending on the composition of coal macerals, rank of coal, burial history, and migration of thermogenic and/or biogenic gas. In one ton of coal 1 to 25 m3 of methane can be accumulated. Accumulation of this gas is included in unconventional deposits. Exploitation of methane from coal seams is carried out with wells from mining excavations (during mining operations), wells drilled to abandoned coal mines, and wells from the surface to unexploited coal seams. Due to the low permeability of the coal matrix, hydraulic fracturing is also commonly used. Operations related to exploration (drilling works) and exploitation of methane from coal seams were analyzed. The preliminary analysis of the environmental threats associated with the exploration and exploitation of coalbed methane has made it possible to identify types of risks that affect the environment in various ways. The environmental risks were estimated as the product of the probability weightings of adverse events occurring and weightings of consequences. Drilling operations and coalbed methane (CBM) exploitation leads to environmental risks, for which the risk category falls within the controlled and accepted range.

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Optimization of Coal Seam Connectivity via Multi-Seam Pinpoint Fracturing Operations in the Walloons Coal Measures, Surat Basin

10.2118/204190-ms ◽

2021 ◽

Author(s):

Vibhas J. Pandey ◽

Sameer Ganpule ◽

Steven Dewar

Keyword(s):

Coal Seam ◽

History Matching ◽

Design Matrix ◽

Coal Seams ◽

Major Step ◽

Well Completion ◽

Eastern Australia ◽

Treatment Designs ◽

Coal Measures ◽

Gas Bearing

Abstract The Walloons coal measures located in Surat Basin (eastern Australia) is a well-known coal seam gas play that has been under production for several years. The well completion in this play is primarily driven by coal permeability which varies from 1 Darcy or more in regions with significant natural fractures to less than 1md in areas with underdeveloped cleat networks. For an economic development of the latter, fracturing treatment designs that effectively stimulate numerous and often thin coals seams, and enhance inter-seam connectivity, are a clear choice. Fracture stimulation of Surat basin coals however has its own challenges given their unique geologic and geomechanical features that include (a) low net to gross ratio of ~0.1 in nearly 300 m (984.3 ft) of gross interval, (b) on average 60 seams per well ranging from 0.4 m to 3 m in thickness, (c) non-gas bearing and reactive interburden, and (d) stress regimes that vary as a function of depth. To address these challenges, low rate, low viscosity, and high proppant concentration coiled tubing (CT) conveyed pinpoint stimulation methods were introduced basin-wide after successful technology pilots in 2015 (Pandey and Flottmann 2015). This novel stimulation technique led to noticeable improvements in the well performance, but also highlighted the areas that could be improved – especially stage spacing and standoff, perforation strategy, and number of stages, all aimed at maximizing coal coverage during well stimulation. This paper summarizes the findings from a 6-well multi-stage stimulation pilot aimed at studying fracture geometries to improve standoff efficiency and maximizing coal connectivity amongst various coal seams of Walloons coal package. In the design matrix that targeted shallow (300 to 600 m) gas-bearing coal seams, the stimulation treatments varied in volume, injection rate, proppant concentration, fluid type, perforation spacing, and standoff between adjacent stages. Treatment designs were simulated using a field-data calibrated, log-based stress model. After necessary adjustments in the field, the treatments were pumped down the CT at injection rates ranging from 12 to 16 bbl/min (0.032 to 0.042 m3/s). Post-stimulation modeling and history-matching using numerical simulators showed the dependence of fracture growth not only on pumping parameters, but also on depth. Shallower stages showed a strong propensity of limited growth which was corroborated by additional field measurements and previous work in the field (Kirk-Burnnand et al. 2015). These and other such observations led to revision of early guidelines on standoff and was considered a major step that now enabled a cost-effective inclusion of additional coal seams in the stimulation program. The learnings from the pilot study were implemented on development wells and can potentially also serve as a template for similar pinpoint completions worldwide.

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Mapping horizons and fracture patterns in coal measures using magnetics for coalbed methane exploration in Queensland

The APPEA Journal ◽

10.1071/aj14078 ◽

2015 ◽

Vol 55 (2) ◽

pp. 443

Author(s):

Irena Kivior ◽

Stephen Markham ◽

David Warner ◽

Leslie Mellon

Keyword(s):

Coalbed Methane ◽

Magnetic Data ◽

Mapping Technique ◽

Stress Regime ◽

Rock Fabric ◽

Fracture Patterns ◽

Eastern Australia ◽

Hill Area ◽

Well Data ◽

Coal Measures

High resolution magnetic data has successfully been used to map the top and base of coal measures, related faults and fracture patterns across the Red Hill area in the northern Bowen Basin, eastern Australia. A horizon mapping technique, based on energy spectral analysis (ESA), was used to detect magnetic susceptibility contrasts that were laterally merged to form two magnetic interfaces, corresponding to the top of the Fair Hill Formation and base of the Goonyella Middle Seam in the Permian Moranbah coal measures. The depth estimates were made at stations on a regular mesh of 400 m x 400 m and at nine wells. The final detailed mapping of both horizons was constructed from spectral depth estimates on a regular mesh of 100 m x 100 m. Major faults, associated structures and fractures were mapped in 3D from the magnetic data by using automatic curve matching (ACM). This technique was applied to detect single magnetic anomalies produced by inter-sedimentary sources. These results were used to interpret magnetic lineaments in, above and below the coal measures to produce a rock fabric model. The results obtained from the interpretation of the magnetic data are consistent with structures mapped from existing seismic and well data. The mapped rock fabric was also confirmed by well results to be a fair representation of the open fracture set, which has an orientation that is consistent with the existing stress regime.

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Investigation on the CBM Extraction Techniques in the Broken-Soft and Low-Permeability Coal Seams in Zhaozhuang Coalmine

Geofluids ◽

10.1155/2021/1163413 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Zhaoying Chen ◽

Xuehai Fu ◽

Guofu Li ◽

Jian Shen ◽

Qingling Tian ◽

...

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Coalbed Methane ◽

Research Result ◽

Horizontal Stress ◽

Gas Production ◽

Vertical Stress ◽

Low Permeability ◽

Coal Seams

To enhance the coalbed methane (CBM) extraction in broken-soft coal seams, a method of drilling a horizontal well along the roof to hydraulically fracture the coal seam is studied (i.e., HWR-HFC method). We first tested the physical and mechanical properties of the broken-soft and low-permeability (BSLP) coal resourced from Zhaozhuang coalmine. Afterward, the in situ hydraulic fracturing test was conducted in the No. 3 coal seam of Zhaozhuang coalmine. The results show that (1) the top part of the coal seam is fractured coal, and the bottom is fragmented-mylonitic coal with a firmness coefficient value of less than 1.0. (2) In the hydraulic fracturing test of the layered rock-coal specimens in laboratory, the through-type vertical fractures are usually formed if the applied vertical stress is the maximum principal stress and is greater than 4 MPa compared with the maximum horizontal stress. However, horizontal fractures always developed when horizontal stress is the maximum or it is less than 4 MPa compared with vertical stress. (3) The in situ HWR-HFC hydraulic fracturing tests show that the detected maximum daily gas production is 11,000 m3, and the average gas production is about 7000 m3 per day. This implies that the CBM extraction using this method is increased by 50%~100% compared with traditional hydraulic fracturing in BSLP coal seams. The research result could give an indication of CBM developing in the broken-soft and low-permeability coal seams.

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Origin of large-scale crossbeds in the late permian coal measures of the Sydney and Bowen basins, eastern Australia

International Journal of Coal Geology ◽

10.1016/0166-5162(85)90026-6 ◽

1985 ◽

Vol 5 (3) ◽

pp. 231-245 ◽

Cited By ~ 6

Author(s):

P.G. Flood ◽

S.A. Brady

Keyword(s):

Large Scale ◽

Late Permian ◽

Eastern Australia ◽

Permian Coal ◽

Coal Measures

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Why Low Permeability and How Does It Affect Coalbed Methane Supply in Coal Seams in China

10.2118/37382-ms ◽

1996 ◽

Author(s):

Y.F. Meng ◽

P.Y. Luo ◽

L. Jin

Keyword(s):

Coalbed Methane ◽

Low Permeability ◽

Coal Seams

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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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HYDROCARBON GENERATION IN THE FLY LAKE—BROLGA AREA OF THE COOPER BASIN

The APPEA Journal ◽

10.1071/aj78012 ◽

1979 ◽

Vol 19 (1) ◽

pp. 108

Author(s):

Michelle Smyth

Keyword(s):

Organic Matter ◽

Sedimentary Basins ◽

Depositional Environments ◽

Fluorescent Light ◽

Hydrocarbon Generation ◽

Coal Seams ◽

Clastic Sediments ◽

Permian Coal ◽

Coal Measures ◽

Cooper Basin

The Cooper Basin is a major gas producing basin in Australia. Organic material in sediments from its Permian coal measures has been studied using transmitted, reflected and fluorescent light microscope techniques of analysis. In the Fly Lake—Brolga area, of the Patchawarra Trough, Cooper Basin, the interseam sediments of the Patchawarra Formation contain three types of kerogen or dispersed organic matter (d.o.m.): exinitic, vitrinitic and inertinitic. Exinitic d.o.m. is most abundant near the top of the Formation, vitrinitic d.o.m. is more abundant in the middle and lower parts of it, and inertinitic d.o.m. occurs throughout.A correlation between the type of d.o.m. in the sediments and the petrography of associated coals is emerging. Exinitic d.o.m. appears to be associated with coals that have high vitrite-plus-clarite contents, whereas vitrinitic d.o.m. is associated with high "intermediates" coals. Further examples are needed to establish these relationships more firmly.On the basis of results of coal petrographic studies in other Australian Permian sedimentary basins, depositional environments have been proposed for the coal seams in the Fly Lake—Brolga area. These environments are compared with those proposed by Thornton (1978) using the clastic sediments of the Patchawarra Formation.

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METHANE DRAINAGE POTENTIAL OF THE NORTHERN BOWEN BASIN

The APPEA Journal ◽

10.1071/aj86022 ◽

1987 ◽

Vol 27 (1) ◽

pp. 281 ◽

Cited By ~ 1

Author(s):

R. M. Bell

Keyword(s):

Physical Parameters ◽

Transport Costs ◽

Coal Seams ◽

Commercial Development ◽

Methane Drainage ◽

Reducing Gas ◽

Considerable Research ◽

Differential Flow ◽

Area North ◽

Coal Measures

Large volumes of methane plus some other gases are generated during the coalification process. Under suitable conditions some of this gas is adsorbed within the microporosity of coals. The rate at which the gas can desorb is a function of the permeability, degree of fracturing or cleating, moisture content, geochemistry of the coals, and the pressure differential. Flow rates from coals are generally low but can be dramatically improved by artificial stimulation and techniques such as lateral drilling.Methane drainage or coal de-methanisation has been carried out for many years, primarily for safety reasons. The resource value of methane in coal seams is now being recognised and considerable research is being undertaken both overseas and in Australia.In the Northern Bowen Basin, several million tonnes of coal are mined each year. The main seams of the Permian Collinsville, Moranbah, German Creek, and Rangal Coal Measures are generally thick and laterally extensive. The area north of Blackwater probably contains more than 100 billion tonnes of coal from which several hundred billion m3 (several Bcf) methane could conceivably be recovered in those areas where the coals are too deep for commercial exploitation.The coals of the Northern Bowen Basin are considered to have better physical parameters for the commercial development of methane drainage projects than those of the central and southern Bowen Basin where methane drainage projects were undertaken several years ago. It is estimated that more than 85 million m3 (3 Bcf) of recoverable gas per square km could be present in some areas. This gas can probably be produced for less than $1.50/GJ (1 Mcft, a figure which compares favourably with many conventional natural gas sources.The Northern Bowen Basin is well-situated with respect to potential gas markets at Townsville and Gladstone. The gas could also be used as a chemical feedstock for products such as ammonia, fertilisers, explosives or synfuels, with the plants located close to the producing wells, thus significantly reducing gas transport costs.

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