Coal seam gas and associated water: A review paper
煤层气与伴生水研究综述
Renewable and Sustainable Energy Reviews, Volume 22, June 2013, Pages 550-560
Abstract:Coalbed methane (CBM) or coal seam gas (CSG) as it is known in Australia is becoming an increasingly important source of energy around the world. Many countries such as United States, Canada, Australia and China are investing in the CSG industry. A rise in the cost of conventional natural gas and many other energy resources, along with a decline in these conventional resources and issues such as climate change have encouraged a global interest in alternative sources of energy like CSG. The estimated quantity of CSG worldwide is around 1.4×1014 m3, it is clear that coal seam gas is a significant source of energy. The first section of this paper will discuss the production size of CSG worldwide and the future of the industry. The usage of the coal bed seam for the sequestration of CO2 is also an added benefit. The reduction of CO2 released to the environment may help in the future mitigation of global warming. In addition, the re-injecting of the co-produced CO2 enhances the commercial recovery and production of CSG wells. In the second section, the impact of the CSG industry's by-products on the environment, the freshwater ecosystem and human health are analysed. The second section includes issues associated with the large volume of co-produced water with undesirable composition in the CSG industry. The management of this enormous amount of water requires cost effective technologies and methods. Many methods for dealing with water problems are discussed and analysed in this paper.
Groundwater methane in a potential coal seam gas extraction region
潜在煤层气抽采区域的地下水甲烷
Journal of Hydrology: Regional Studies, Volume 4, Part B, September 2015, Pages 452-471
Abstract：Study region This study investigates dissolved methane distribution in groundwater from the Richmond River Catchment (New South Wales, Australia) before proposed coal seam gas (CSG, or coal bed methane) development.
Study focus Unconventional gas exploration has rapidly expanded in recent years. However, the impact of these operations on groundwater systems is poorly understood. A total of 91 groundwater samples were analyzed from 6 geological units. Our observations act as regional baseline research prior to CSG extraction and may assist with long term impact assessment.
New hydrological insights for the region
Methane was found in all geological units ranging between 0.26 and 4427 μg L−1 (median 10.68 μg L−1). Median methane concentrations were highest in chloride-type groundwater (13.26 μg L−1, n = 58) while bicarbonate-type groundwater had lower concentrations (3.71 μg L−1). Groundwater from alluvial sediments had significantly higher median methane concentrations (91.46 μg L−1) than groundwater from both the basalt aquifers (0.7 μg L−1) and bedrock aquifers (4.63 μg L−1); indicating geology was a major driver of methane distribution. Methane carbon stable isotope ratios ranged from –90.9‰ to –29.5‰, suggesting a biogenic origin with some methane oxidation. No significant correlations were observed between methane concentrations and redox indicators (nitrate, manganese, iron and sulphate) except between iron and methane in the Lismore Basalt (r2 = 0.66, p < 0.001), implying redox conditions were not the main predictor of methane distribution.
Inferring the Shape of Fractures and Hydraulic Properties of the Coal Seam Using Inverse Modeling on Pumping Test Results –Broke, NSW, Australia
抽水试验结果反演模拟在澳大利亚新南威尔士Broke煤层断裂形状与水文特性推理中的应用
Procedia Environmental Sciences, Volume 25, 2015, Pages 11-18
Abstract:Coal seam gas or coal bed methane production is becoming a significant industry in Australia. The area around the Broke township (located in the north-west of the Sydney Basin) has had coal seam gas exploration activities over the last decade. One methodology of well stimulation, hydraulic fracturing, has the potential to cause some environmental problems. The Broke region includes 4 aquifers (3 confined and semi-confined), more than 3 major coal seams (3 gas bearing) and has been covered by variety of different sedimentary rocks of Permian age. The groundwater system, with the gas bearing deposits is the function of conductivity and storativity (K and S) of the coal seam and geometry of properties of the fractures. The required data to investigate the hydraulic properties in the fractured zone includes; corehole data to assessment the geology and underground system, micro-seismic data to infer the fracture properties, pumping tests results, and monitoring wells data to evaluate the hydraulic properties of the coal seams. This paper investigates the shape of drawdown curves, resulting from the hydraulic pumping tests at Broke performed to determine the hydraulic and fracture properties, such as length, width, conductivity of fractures, and the proportion of the water and gas contained in the targeted coal seam. In order to reduce data uncertainty and increase the reliability of the hydraulic property estimation the Generalized Likelihood Uncertainty Estimation (GLUE) will be applied. Finally, with investigation of the shape (length and width) and conductivity of the fractures, the best monitoring method to ensure public safety of provide assurances that if problems occur the monitoring system will provide early warning for this study area will be determined.
Chemical variabilityof groundwater samples collected from a coal seam gas exploration well,Maramarua, New Zealand
新西兰Maramarua煤层气开采井地下水样本的化学变化规律
Water Research, Volume 47, Issue 3, 1 March 2013, Pages 1021-1034
Abstract:Coalbed methane (CBM) or coal seam gas (CSG) as it is known in Australia is becoming an increasingly important source of energy around the world. Many countries such as United States, Canada, Australia and China are investing in the CSG industry. A rise in the cost of conventional natural gas and many other energy resources, along with a decline in these conventional resources and issues such as climate change have encouraged a global interest in alternative sources of energy like CSG. The estimated quantity of CSG worldwide is around 1.4×1014 m3, it is clear that coal seam gas is a significant source of energy. The first section of this paper will discuss the production size of CSG worldwide and the future of the industry. The usage of the coal bed seam for the sequestration of CO2 is also an added benefit. The reduction of CO2 released to the environment may help in the future mitigation of global warming. In addition, the re-injecting of the co-produced CO2 enhances the commercial recovery and production of CSG wells. In the second section, the impact of the CSG industry's by-products on the environment, the freshwater ecosystem and human health are analysed. The second section includes issues associated with the large volume of co-produced water with undesirable composition in the CSG industry. The management of this enormous amount of water requires cost effective technologies and methods. Many methods for dealing with water problems are discussed and analysed in this paper.
A comprehensive model to history match and predict gas/water production from coal seams
煤层气/水生产的历史拟合与预测综合模型
International Journal of Coal Geology, Volume 146, 1 July 2015, Pages 79-90
Abstract:Coalbed methane (CBM) currently accounts for approximately 5% of U.S. annual gas production. The performance prediction of CBM is very complex. It is highly affected by the complexity of porosity–permeability variation, reduction due to formation compaction, enhancement due to matrix shrinkage, and the two-phase flow effects. An additional complexity is added if the initial gas content, permeability, and porosity are not available. In this paper an integrated model was developed to simulate the behavior of CBM. A developed generalized material balance equation is used to account for the solubility of the methane in water, and the changes of porosity and permeability with pressure depletion. The equation is formatted similarly to the conventional material balance of oil reservoirs.
An optimization algorithm was also used with the integrated model. The model could be used as a history matching tool to estimate the original gas-in-place (the adsorbed gas-in-place and the free gas-in-place), the initial formation permeability, the gas and water relative permeability exponents, and the matrix shrinkage coefficient that reflected the permeability changes.
The developed model was validated by use of different simulation cases generated with a commercial simulator. The results show a good match between the simulation cases and the integrated model. The model was then used to analyze the production data of different CBM formations (the Fruitland and the Upper Pottsville Formations, USA). The model was used to match the production history data (gas and water rates) in order to estimate the gas-in-place and the formation properties. These parameters were then used to predict the production performance. The model can be run with different production control conditions such as the constant water rate or the constant bottom-hole flowing pressure.
This model could be used as a helpful tool in CBM investment and development. It can also be used to obtain the key reservoir parameters for newly discovered reservoirs such as gas-in-place, initial water-in-place, water production rate, gas production rate, and the peak gas rate. With this information, an investor will better determine the feasibility of a project. Also, this model can be used to optimize the dewatering rate (initial water production rate) in order to optimize the time taken to reach the peak gas rate.
Hydrochemical processesin a shallow coal seam gas aquifer and itsoverlying stream–alluvial system: implications forrecharge and inter-aquifer connectivity
浅煤层气含水层及其上覆河川冲积层系统的水文化学过程：补给与含水层之间相互导通性之含义
Applied Geochemistry, Volume 61, October 2015, Pages 146-159
Abstract:In areas of potential coal seam gas (CSG) development, understanding interactions between coal-bearing strata and adjacent aquifers and streams is of highest importance, particularly where CSG formations occur at shallow depth. This study tests a combination of hydrochemical and isotopic tracers to investigate the transient nature of hydrochemical processes, inter-aquifer mixing and recharge in a catchment where the coal-bearing aquifer is in direct contact with the alluvial aquifer and surface drainage network. A strong connection was observed between the main stream and underlying alluvium, marked by a similar evolution from fresh Ca–Mg–HCO3 waters in the headwaters towards brackish Ca–Na–Cl composition near the outlet of the catchment, driven by evaporation and transpiration. In the coal-bearing aquifer, by contrast, considerable site-to-site variations were observed, although waters generally had a Na–HCO3–Cl facies and high residual alkalinity values. Increased salinity was controlled by several coexisting processes, including transpiration by plants, mineral weathering and possibly degradation of coal organic matter. Longer residence times and relatively enriched carbon isotopic signatures of the downstream alluvial waters were suggestive of potential interactions with the shallow coal-bearing aquifer. The examination of temporal variations in deuterium excess enabled detection of rapid recharge of the coal-bearing aquifer through highly fractured igneous rocks, particularly at the catchment margins. Most waters collected from the coal-bearing aquifer also showed an enhanced influence of weathering during the wet season, which was likely triggered by the water–rock interaction with fresh recharge waters. An increase in both residual alkalinity and carbon isotopic ratios at two locations indicated inter-aquifer mixing between alluvium and bedrock during the wet season. The results of this study emphasise the need for conducting baseline hydrochemical surveys prior to CSG development in order to describe the transient nature of recharge and inter-aquifer mixing processes.
