Strategies for the management and treatment of coal seam gas associated water

煤层气伴生水控制与处理策略

Renewable and Sustainable Energy Reviews, Volume 57, May 2016, Pages 669-691

Abstract:Coal seam gas (CSG) is a growing industry in Queensland and represents a potential major employer and deliverer of financial prosperity for years to come. CSG is a natural gas composed primarily of methane and is found trapped underground in coal beds. During the gas extraction process, significant volumes of associated water are also produced. This associated water could be a valuable resource, however, the associated water comprises of various salt constituents that make it problematic for beneficial use. Consequently, there is a need to implement various water treatment strategies to purify the associated water to comply with Queensland’s strict guidelines and to mitigate environmental risks. The resultant brine is also of importance as ultimately it also has to be dealt with in an economical manner. In some ways it can be considered that the CSG industry does not face a water problem, as this has inherent value to society, but rather has a “salt issue” to solve. This study analyzes the options involved in both the water treatment and salt recovery processes. A brief overview of the constituents present in Queensland CS water is made to illustrate the challenges involved and a range of treatment technologies discussed. Water treatment technologies examined include clarification (ballasted flocculation, dissolved air flotation, electrocoagulation), membrane filtration (ultrafiltration), ion exchange softening and desalination (ion exchange, reverse osmosis desalination and capacitance deionization). In terms of brine management we highlighted reinjection, brine concentration ponds, membrane techniques (membrane distillation, forward osmosis), thermal methods, electrodialysis, electrodialysis reversal, bipolar membrane electrodialysis, wind assisted intensive evaporation, membrane crystallization, eutectic freeze crystallization and vapor compression. As an entirety this investigation is designed to be an important tool in developing CS water treatment management strategies for effective management in Queensland and worldwide.

Understanding coal seam gas associated water, regulations and strategies for treatment

煤层气伴生水研究与其处理策略

Journal of Unconventional Oil and Gas Resources, Volume 13, March 2016, Pages 32-43

Abstract:The coal seam gas (CSG) industry is globally of potentially great importance economically. This study exemplifies the complex relationship between land use and management, groundwater impact and associated water treatment especially in relation to Queensland where a significant increase in the amount of gas extracted over the past 6 years has occurred. In order to effectively manage the environmental impact of the CSG industry it is necessary to appropriately understand the nature of the gas deposits, methods for gas collection, the physicochemical composition of the by-product associated water and the technologies available for water remediation. Australia is mainly considered arid and semi-arid and thus there is a need to not only beneficially reuse water resources but also protect existing ground water reservoirs such as the Great Artesian Basin (GAB). This paper focussed primarily on the Surat Basin located in Queensland and northern New South Wales. The mechanism for CSG formation, relation to local geological features, extraction approach and the potential impact/benefits of associated water was discussed. An outline of the current legislative requirements on physical and chemical properties of associated water in the Surat Basin was also provided, as well as the current treatment technologies used by the major CSG companies. This review was of significance in relation to the formulation of the most appropriate and cost effective management of associated water, while simultaneously preserving existing water resources and the environment.

Behaviour of Natural Zeolites used for the Treatment of Simulated and Actual Coal Seam Gas Water

天然沸石在模拟与实际煤层气伴生水处理中的应用特性

Journal of Environmental Chemical Engineering, In Press, Accepted Manuscript, Available online 11 March 2016

Abstract:Coal seam gas operations produce significant quantities of associated water which often require demineralization. Ion exchange with natural zeolites has been proposed as a possible approach. The interaction of natural zeolites with solutions of sodium chloride and sodium bicarbonate in addition to coal seam gas water is not clear. Hence, we investigated ion exchange kinetics, equilibrium, and column behaviour of an Australian natural zeolite. Kinetic tests suggested that the pseudo first order equation best simulated the data. Intraparticle diffusion was part of the rate limiting step and more than one diffusion process controlled the overall rate of sodium ion uptake. Using a constant mass of zeolite and variable concentration of either sodium chloride or sodium bicarbonate resulted in a convex isotherm which was fitted by a Langmuir model. However, using a variable mass of zeolite and constant concentration of sodium ions revealed that the exchange of sodium ions with the zeolite surface sites was in fact unfavourable. Sodium ion exchange from bicarbonate solutions (10.3 g Na/kg zeolite) was preferred relative to exchange from sodium chloride solutions (6.4 g Na/kg zeolite). The formation of calcium carbonate species was proposed to explain the observed behaviour. Column studies of coal seam gas water showed that natural zeolite had limited ability to reduce the concentration of sodium ions (loading 2.1 g Na/kg zeolite) with rapid breakthrough observed. It was concluded that natural zeolites may not be suitable for the removal of cations from coal seam gas water without improvement of their physical properties.

Fully coupledthermo-hydro-mechanical modelfor extraction of coal seam gas withslotted boreholes

采用切槽钻孔煤层气抽采的全耦合热-水-力模型

Journal of Natural Gas Science and Engineering, In Press, Accepted Manuscript, Available online 3 March 2016

Abstract:China has abundant coal seams with high gas content and low matrix permeability, which is unfavorable for efficient gas extraction. Popular extraction technology that uses high-pressure water jet slotting can overcome this difficulty, increase the contact area of coal and air, and expand the influence radius of boreholes. Thus, this technology improves gas extraction rates and ensures mine safety. Although the high-pressure water jet slotting technology has been comprehensively investigated and tested, fewer studies have been conducted on coal seam gas extraction with slotted boreholes using a fully coupled thermo-hydro-mechanical model. Neglecting this coupled thermo-hydro-mechanical interaction may result in misleading estimates of the gas extraction effect, which could be detrimental to the production prediction, drainage optimization design and gas control.

A new technology for thedrilling of long boreholesfor gas drainage in a soft coal seam

软煤层瓦斯抽采长钻孔钻井新技术

Journal of Petroleum Science and Engineering, Volume 137, January 2016, Pages 107-112

Abstract:The geostatic stress, coal mine gas and disturbances produced by external loading can undermine the stability of a borehole and cause the borehole to collapse in a soft coal seam, which results in a poor efficiency of drilling long boreholes and draining gas in a soft coal seam. To improve the efficiency of drilling boreholes and draining gas in a soft coal seam, we propose a drilling technology of protecting the borehole by spraying foam concrete slurry onto the surface of borehole wall during drilling in a soft coal seam. To realize this process, we propose spraying foam concrete onto the borehole wall during drilling with a foldable drill bit and double drill pipes. Based on this new technology, the equipment and the material required for drilling long boreholes in a soft coal seam were studied. Finally, this new technology was tested in the Zhaozhuang mines in the Shanxi Province of China. The test results indicate the following: the process of spraying foam concrete on the borehole wall can relieve borehole collapse; the plant-based foam concrete has good air permeability, and has no effect on the permeability of the borehole wall; and the novel process of drilling boreholes and spraying foam concrete is an effective drilling process, which can relieve borehole collapse, improve the drilling efficiency and improve the draining efficiency.