1、翻译部分英文原文Simulation of an enhanced gas recovery field trial for coal mine gas managementRussell Packham a,*, Yildiray Cinar b, Roy Moreby aa School of Mining Engineering, University of New South Wales, Sydney, NSW 2052, Australiab School of Petroleum Engineering, University of New South Wales, Sydney
2、, NSW 2052, AustraliaArticle infoArticle history:Received 30 September 2010Received in revised form 27 November 2010Accepted 27 November 2010Available online 13 December 2010Abstract: Coal mine gas management has evolved from being predominantly dependant on mine ventilation systems to utilising sop
3、histicated surface based directional drilling for pre-drainage of coal seams. However the advent of enhanced gas recovery techniques in the coalbed methane industry has provided an opportunity to address gas management objectives hitherto impractical. Specifically: achieving very low residual gas co
4、ntents to mitigate against frictional ignitions and fugitive emissions; the means to accelerate gas drainage to accommodate mine schedule changes; and to enable pre-drainage of coal reserves with very low permeability. This article examines a possible enhanced gas recovery field trial at an Australi
5、an mine site. Production data from four surface to inseam medium radius gas drainage boreholes was modelled and history matched. The resulting reservoir characteristics were then used to model the performance of the boreholeusing an enhanced recovery technique. One of the boreholes is modelled as an
6、 (nitrogen) injection well and two flanking wells are modelled as production wells.The model results suggest that accelerated gas flow rates as well as very low residual gas contents are achievable using typical coal mine gas drainage infrastructure and goaf inertisation systems.Keywords: Enhanced g
7、as recovery , Coal mine gas management , Pre-drainage , Methane drainage , Nitrogen1.IntroductionAs underground coal production rates increase, and the seamsworked become deeper and gassier, the practise of gas drainage has been progressively adopted. Gas drainage involves capturing the seam gases,
8、before they enter the mine ventilation system, and using a reticulation system to dispose of the gases safely. Gas drainage includes pre-drainage of gas prior to mining commencing and post drainage(also known as goaf or gob drainage) of gas from fracturedand de-stressed strata associated with coal e
9、xtraction.Adoption of medium radius drilling for surface pre-drainage of coal seams has allowed drainage lead times in excess of 3 years. Typically this degree of pre-drainage achieves residual gas levels that do not impede mining operations. There are, however, some scenarios that still provide dif
10、ficulties from a coal mine gas management perspective:Localised regions of low permeability requiring extended drainage time not compatible with mine development and extraction schedules.Changes in mine development schedules requiring accelerated drainage.Lowering residual gas levels to very low lev
11、els as a possible mitigation of frictional ignitions and fugitive emissions.A promising technique referred to as “enhanced gas recovery” was described by Puri and Yee (1990). The technique was proposed for use in the coalbed methane industry to both increase cumulative production of methane from coa
12、l seams and to improve the rate of recovery. Recognition of the potential value of this technique with respect to coal mining has largely been overlooked by coal mining industry although two references to the possibilities have been found(Brunner and Schwoebel, 2007; Thakur, 2006).The technique invo
13、lves injecting a gas, which is different to the seam gas, into the coal seam to stimulate methane (or other seam gas) production. The injectant is introduced into the coal seam via an injector borehole and the seam gas is collected at separate production borehole(s).Four field trials involving using
14、 nitrogen as an injectant gas have been identified. The Tiffany unit trial (Reeves and Oudinot, 2004) which ran for 3 years demonstrated a 5-fold increase in gas flow rate arising during the trial. The Alberta Fenn Big Valley micro pilot trial (Mavor et al., 2004) demonstrated increases of absolute
15、permeability from initial conditions of 1.2 mD to 13.8 mD resulting from nitrogen injection. During the Yubari CO2 sequestration trial (Shi et al., 2008),in an attempt to improve the CO2 injection rate, N2 was introduced to the reservoir. Modelling of the results indicated that an improvement in wel
16、l block permeability of 0.1 mD to 40 mD accrued.One trial involving nitrogen injection has been conducted at an underground coal mine in China (Yang et al., 2010). The trial involved injection of nitrogen at 500 kPa into closely spaced, 1520 m long gas drainage boreholes at the face of a development heading. The gas flow rate from the production boreholes demonstrated a 2 fold increase after 16 h of injection.The stimulation of t
