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1、 SPE 114992 Development of Coalbed Methane in Australia: Unique Approaches and Tools Y. Ham and A. Kantzas, University of Calgary Copyright 2008, Society of Petroleum Engineers This paper was prepared for presentation at the CIPC/SPE Gas Technology Symposium 2008 Joint Conference held in Calgary, Al
2、berta, Canada, 1619 June 2008. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by
3、 the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permiss
4、ion to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright. ABSTRACT Coalbed Methane (CBM), also known as Coal Seam Gas (CSG) or Coal Seam Methane (CSM) in Australia is fast
5、 becoming a significant contributor to the countrys energy needs. The potential coal seams for methane production in Australia are found in coal zones that are Jurassic to Permian in age with coal ranks ranging from sub-bituminous to low volatile bituminous coals. Many Australian coal seams contain
6、high volumes of methane gas upto 25 m3 per tonne. Australia began producing CBM in 1988 but it was not until 1996 when the commercial CBM production started in the state of Queensland. Australia has total CBM reserves of about 300 to 500 Tcf (8.6 to 14.3 trillion m3). With the total amount of CBM in
7、-place reserves worldwide estimated to be between 3,500 and 95,000 Tcf (100 and 272 trillion m3), CBM is considered one of the worlds largest sources of fossil fuel. In the United States, the total CBM in-place reserves are estimated at 749 Tcf (21.4 trillion m3), and CBM now represents almost 10% o
8、f its domestic natural gas production. Canada has just begun producing gas from CBM reservoirs and its estimated in-place CBM reserves are about 1,300 Tcf (37 trillion m3). In Australia, as CBM is seen as a clean and pipeline- quality energy, it is rapidly developing. Along with the large CBM resour
9、ce, the main drivers for this move are the continuously reducing cost of coal seam gas production, and the depleting conventional energy resources. A number of sophisticated CBM reservoir simulation and exploitation tools have been developed by the University of New South Wales and CSIRO to simulate
10、 the conventional CBM production as well as the CBM recovery using multi-component gases. In the field, Australia looks toward enhancing CBM recovery by injecting nitrogen and or carbon dioxide to increase CBM extraction. This paper will focus on how Australia is maximizing its CBM production. INTRO
11、DUCTION Coal is “the black rock that burns” (Land and Rice, 1993). It is defined as a readily combustible rock that contains more than 50% by weight and more than 70% by volume of carbonaceous material including inherent moisture formed by compaction and induration (hardening of sediment) of various
12、 altered plant remains. The type of plant materials, degree of metamorphism, and the range of impurity characterize coal (Bates and Jackson, 1980). A coal seam is a bed of coal, and the natural gas or methane produced from coal seams is referred to as coalbed methane (CBM). CBM production began init
13、ially to keep coal mining safe from explosions. If the methane-air mixture was in the range of 5 to 15%, methane would be explosive (Cervik, 1967). However, with the global oil production decline and the coalbed methane being a clean-burning fuel compared to the conventional fossil fuels, it has bec
14、ome an important resource that can assist in addressing the worlds growing energy needs. In Canada, since 2000, there has been an increase in CBM exploration due to increasing natural gas prices, increased natural gas demand both domestically and internationally, development of new technologies, and
15、 the maturation of the Western Canadian Sedimentary Basin (Beaton, 2007). It is expected that CBM will contribute significantly to future natural gas supply. Currently, it is contributing nearly 10% of the U.S. gas needs. 2 SPE 114992 WHAT IS COALBED METHANE? Coalbed methane (CBM) is a natural bypro
16、duct of the coalification process, which converts organic matter like wood, and peat to coal. CBM consists mostly of methane (CH4) but there may be some minor amounts of carbon dioxide, nitrogen, water vapour, and heavier hydrocarbons like propane, and ethane. CBM is considered “sweet” not “sour” as
17、 it does not contain hydrogen sulphide (H2S) (Alberta Energy, 2007). CBM is an unconventional gas that is different from natural gas from a conventional sandstone reservoir in that, unlike petroleum resources, it is both generated and stored within the coalbeds. Therefore, it is an attractive resour
18、ce that can be produced from coal, which is the most abundant fuel in the world. According to the World Coal Institute (2006), coal reserves are available in almost every country worldwide providing 25% of the global primary energy needs, with recoverable reserves in around 70 countries. At the end
19、of 2006, the recoverable coal reserves amounted to around 998 billion tons, which is equal to about 4,417 billion barrels of oil equivalent, and at current production levels, the proven coal reserves are estimated to sustain production for 164 years (Wikipedia on Coal, 2007). CBM is physically adsor
20、bed on the molecular surface of the coal and stored in micropores. Although coal pore volume is small ( 95 CMM 35 - 75 AMM 5 - 90 Mine ventilation air 0.05 0.8 8 SPE 114992 Figure 1 Australian coal-bearing basins (ITAM Coal, 2003) Figure 2 Oaky Creek Envirogen power plant (World Coal Institute, 2007) Figure 3 Appin tower power station in New South Wales, Australia Figure 4 Worldwide projects on ECBM (sequestration) (Reeves, 2003)