Step change approaches in coal technology and fugitive emissions research

International Journal of Mining Science and Technology 24(2014)363-367Contents lists available at Science DirectInternational Journal of Mining Science and TechnologyELSEVIERurnalhomepagewww.elsevier.com/locate/ijmstStep change approaches in coal technology and fugitive emissionsresearchAminossadati S M., Amanzadeh M, Rochon E, Kok., Adam SSchool of Mechanical and Mining Engineering, CRC Mining. The University of Queensland, Queensland 4072, AustraliaARTICLE INFOABSTRACTArticle historMulti-factor productivity(MFP)in underground coal mining has been on the decline for the last decade.Received 10 October 201Received in revised form 15 November 2013The mining industry requires a viable and sustainable approach to overcome the current downtrend. ThisAccepted 8 December 2013Available online 29 April 2014delivered through both incremental and step change technology development. Four technologies are pre-sented in this paper: fibre optic borehole sensing has been demonstrated to reveal detailed informaticabout gas flow influx, water level and borehole blockage events occurring along the length of a surfae-inseam lateral, Fibre optic gas sensing has also been investigated and this technology promises am gaFibre optic sensingremote intrinsically safe, distributed solution, Recent developments in continuous water jet drilling technology have demonstrated a step change increase in drilling rates and flexibility for coal seam degassing.applicable in both surface-to-inseam and underground in-seam applications. The application of water jetRoof boltingtechnology to the cable bolt drilling problem offers potential to address a serious health and safety andity issue in the roadway development procee 2014 Published by Elsevier B V, on behalf of China University of Mining Technology1 Introductionoptic-based system for borehole gas monitoring is being developedthat can provide gas flow event detection along the entire length ofSt Multi-factor productivity ( MFP) provides a comprehensive mea- a vertical or horizontal borehole. The information will enable coalof the efficiency with which combined labour and capital miners and coal seam gas producers to observe gas emissions alonginputs are transformed into output. The MFP index for the Austra- the length of the borehole, and identify non-producing zones. Thislian mining industry has been declining at an alarming rate since is critical information to increase gas production and avoid mining2002(Fig.1)in un-drained seams, which has high gas content and consequentlyStep change technologies are required to reverse this trend. The associated with higher costs, emission and risks during miningproposed strategy involves working towards research and develop-Currently, flow in a pre-mining gas drainage borehole is onlyment of revolutionary'step change' technologies in such a way that measured at the well collar, or seldom measured at all. This doesvaluable interim industry outcomes can be delivered in the process. not provide any information on where the gas flow originatedIn considering underground mining, technology development strat- and how effective the gas drainage was throughout a large regionegy should focus on contributing to addressing low productivity Gas flow inside well bores produces thermal signatures Based onhigh cost activities, particularly those activities carrying a high cost this phenomenon, distributed temperature sensing(DTS)is usedconsequence if not realised effectively during the mining process. in the oil and gas industries to identify the locations of reservoirsTwo such examples are pre-mine gas drainage and roadway deve l- and measure the total volume flow from each reservoir. DTS sysopment. Four technologies that target improvement of productivity tems have also been used in monitoring the underground ventila-and cost reduction in these activities are discussed hereintion environment, detecting the underground fire, monitoring thetrailing cables and developing the automatic underground alarm2. Distributed bore-hole gas production monitoringsystems[1-6]. Products already exist that utilise DtS for flow pro-filing. Manufacturers such as Silixa, Halliburton, AP Sensing, OPPre-mining gas drainage boreholes are routinely drilled to Sens Solutions, and Opta Sense have products as well as extensivereduce gas contents to safe statutory levels. a distributed fibre in-house expertise. Nonetheless, none of these products provide aready solution for pre-mining drainage in coal seams, and they alsoCorresponding author. Tel. +61 7 33653676.require significan中国煤化工 Thus, this is aE-mail address: uqsamino@uq. edu. au(S M. Aminossadati)-ng industry.CNMHGhttp://dx.doiorg/10.1016/j.ijmst.2014.03.0132095-2686 2014 Published by Elsevier B V on behalf of China University of Mining Technology64S.M. Aminossadati et aL. International Journal of Mining Science and Technology 24(2014)363-367180borehole did not perform adequately; and( 8)data that can help160validate and improve existing gas reservoir and drainage models140This includes important reservoir parameters such as relative per-meability, fracturing, and geological structures.rful technology with thesignificant benefit towards maximising pre-mining gas recovery20improving the quality and consistency of mine gas production,and providing continuous improvement of gas drainage practices尽8实§3. Fibre-optic based methane gas sensingMethane is a potentially hazardous gas which has contributedg. 1. Estimates of mining industry multifactor productivity.to numerous fatalities in the mining industry. The presence of sucha dangerous gas, which affects both safety and productivity in mineThe work that has been conducted so far by CRCMining has environments, calls for adopting an intrinsically safe, fastinvolved both the practical aspect of reliable deployment of the response, reliable, and accurate gas monitoring system. there arefibre in the borehole and developing techniques to interpret gas three primary incentives for maintaining accurate methane gasflow events from the DtS data. This will provide innovative ways measurements throughout underground coal mines, that is, toof observing gas flow events and the consistency of the flow over improve mine operation safety to reduce of the environmentaltime, but without the need to have expertise to apply complex impacts of methane emissions by providing adequate informationnumerical modelling in order to convert the dts data to a flow for more effective approaches to gas drainage, ventilation, and utilmeasure. Interpreting gas flow involves identifying the thermal isation, and to increase mine productivity by reducing downtimecharacterisation responses of gas flow events inside the borehole due to high methane levels [71and developing visual software tools for observing the eventsLately, there have been many research projects aimingThe prototype system has been trialled at a vertical well in the Ila- develop and take to trial fibre optic based methane gas monitoriyarra and a SiS well in central Queensland( Fig. 2). The results have systems using open-path gas cell sensor heads for undergroundbeen successful in identifying"signature"changes in temperature coal mine application [ 8-14]. Deploying an optical fibre sensor netinside the borehole that could be directly associated with events work provides a passive sensing element which can be remotelysuch as:(1)locations of localised gas emission into the borehole located and monitored, prong an intrinsically safe techniquethrough cleats and fractures; (2)locations of gas producing zones: in harsh underground coal mine environments. In addition, this)presence, source, and movement of water inside a borehole; capability can be expanded via multiplexing methods, where aand(4)location of partial collapses and blockagesgle control unit can monitor many passive sensors throughA final phase of the project will be conducted throughout 2014 optical fibre network. This offers a cost effective sensing solutionand 2015 to complete developing the product and to collect a large relative to the number of sensor heads. Thus far, fibre optic sensorvolume of data from multiple boreholes to continue demonstratisystems are still in the development stage and undergoing trials forthe effectiveness of the models. This system will deliver the follow- underground coal mine applicationsing benefits: (1) for pre-mining gas drainage applicationsIn the first stage of this project, the spectroscopic fibre opticimproved confidence that the whole targeted zone covered by sensing technique was developed using pre-filled open path gasthe borehole is drained; (2)ensuring a safer mining environment: cells with known concentrations of methane. the measurement of(3)improving mining productivity in gassy seams; (4)for commer- average methane concentration using a number of gas cells concial gas production, a valuable tool to assist operators in managing nected via a single optical fibre was also investigated The resultsoduction and to maximise gas recovery;(5)for goaf holes, the showed that open path gas cells had sufficient accuracy, fastability to determine the depth(s) above the goaf where gas flow response time and excellent sensitivity and robustness to have theis occurring;(6)assisting in taking ameliorative action to stimulate potential as a future underground mine gas sensing system. Thenon-producing zones;(7) reducing the uncertainties of fugitive second stage of the project involved the development and experigas emissions by knowing exactly which zones of the drainage mental analysis of three microstructure fibre optic sensor headsZonalonalYH中国煤化工CNMH Go 1150Borehole depth(m)orehole provide informaticS.M. Aminossadati et al International Journal of Mining Science and Technology 24(2014)363-367so that they can be further developed in those directions. In ordeto prevent any damage to the sensor heads and to ensure accuratereadings and fast response time, both sensors need to be filteredfrom underground contamination such as coal dust and diesel par-ticulate matter. The open path gas cells seem to be more practicalfor underground mine applications since they have faster responsetime and simpler and more robust structure than theHollow corehollow core fibre sensors. on the other hand the drilledcore fibre sensors are more amenable to forming part of a sensingnetwork that consists of many sensor heads connected via a singlehe technology ofdistributed gas sensing using back reflection isfuture4. Continuyater jet drillingA need exists for a low cost drilling technology, flexible in appliFig 3. Drilled single mode optical fibre 151.(a)Drilled hollow core fibre(b)Cross- cation, deployable from the surface or underground workings tosection of drilled hollow core fibre. (c)10 um drilled hole. (d)Close-up of drilled rapidly install in-seam boreholes for pre-mine gas drainage purholeposes. It is not uncommon for underground in-seam drilling torequire as much as 5 12-hour shifts to install a single 350 mtapered fibre, drilled single mode fibre and drilled hollow core fibre cross-panel lateral Conventional drilling systems use jointed pipe,and in the underground application manual handling and the asso-A methane gas concentration experimental setupFig 4)was ciated injuries persist.designed and manufactured to test all-fibre sensor heads in a safeContinuous waterjet drilling technology offers a step changecontrolled manner at various known methane concentrations [ 16]. alternative. a pure waterjet drill head employs the action of waterntrinsically safe fibre optic based prototype sensors were successets to cut the target rock. Ideally, no mechanical bit-rock interac-fully demonstrated to have the potential to accurately measure the tion occurs in the cutting process. Consequently, weight on bit andmethane concentration in underground coal mines within a rea- torque requirements for waterjet drills are orders of magnitudesonable response time. Four fibre optic based sensing techniques lower than conventional drilling techniques. It has been furtherwere developed and assessed: one using pre-filled open path gas demonstrated that waterjet drilling tools can be configured to gen-cells with known concentrations of methane(0. 1-10%)in nitrogenerate net forward thrust at the drill head(self-elled). As aand three based on microstructure optical fibres. Two methods for result it is possible to contemplate the use of continuous, flexiblemethane detection were tested for each sensor head: direct conduits to convey the drilling tool and pressurised drilling fluidabsorption andivelength modulation spectroscopy.into the boreholeTable 1 shows the results achieved for each of the sensor headsAll drilling systems must overcome the challenge of generatingdeveloped in this project [171a high quality borehole of uniform profile in a variety of rock typesBoth the open path gas cell and hollow core fibre sensor were and drilling conditions. This is particularly challenging in coalshown to have sufficient sensitivity, accuracy and response times drilling, considering the general variability in coal competencyto have the potential to be used as part of an underground minegas sensing system. This is a highly positive outcoms to mn sted th a 300 m in coal seams. The drilling tool is self-propelled, geneA compact water-jet drill head has been developed( Fig. 5)thatexperimental sensor head designs. It is likely that with industry ating sufficient net thrust to convey long high pressure hose wig a pconsultation, it will be possible to identify specific applications length of more than 300 m into the boreholefor which each of the two successful sensor heads are best suitedA compact survey electronics package is contained in the drillhead, and transmits summary survey and tool parameters to theoperator in real time. Typical drilling rates range from 1 to >4 m/Check valvemin, and is dependent on rock properties and drill head setup听The use of a flexible hose conveyed from the surface allows continuous drilling to be realised a number of advantages stem fromthe use of flexible hose when combined with a waterjet drill headGas inlet(1)Health and safety benefittion of manual handling hazards and complex machine-mangaugeated with jointed drill pipe. Continuousilling systems are eminently10:90remote operation and automation of drilling processes.Fibre inletinvolved in(2)Continuous中国煤化工iy. with currentChambersystems derCNMHGrals drilled in 6 h(3)Continuousboth highFig 4. Schematic of methane gas concentration setup[16-366S.M. Aminossadati et aL. International Journal of Mining Science and Technology 24 (2014)363-367Table 1Summary results of methane detection with different sensor heads.Sensor headDetection technique Sensitivity"(%)Relative Error"(%Response timeIth gas celnstantaneous67InstantaneousTapered fibreDirect absorptioNo responsedDirect absorptioNJADrilled hollow core fibre(85 mm in lengthirect absorption264559s0030.259sNotes:Sensitivity indicates the minimum methane concentration detectable above the background noise levels of the signal; relative error indicates the difference betweenthe measured methane concentration and the actual methane concentration, expressed as a percentage of the actual concentration; and response time indicates The time ittook for the signal to reach 90% of its final, steady state, signal upon exposure to a certain concentration of methaneCRCMEMulti axisFig. 5. High speed cross panel drilling rig.(4) The flexible high pressure hose can be used in radial drillingtechniques from within a pre-drilled vertical well, wherein aseries of horizontal laterals can be installed in multiple coalseams from a single vertical well. a tight radius drillingsystem( Fig. 6) has recently been demonstrated in a pre-commercial pilot scale project(5) Compact rig designs can be realised, with high pressure hosespooled tightly onto drums, for both underground in-seamand surface to in-seam drilling applicatiorCurrent research is focused on increasing range and applicationof waterjet drilling systems through improvements in steeringcontrol, borehole quality and survey accuracy. These improvements are expected to enable in-mine demonstration of a highspeed cross panel/ measure drilling5. Water jet cable bolt drillingCurrent cable bolt or long tendon installation practice forFig. 6. Tight radius drilling conceptunderground roof support is generally considered to be a highlyunproductive exercise, and presents a major bottleneck to roadwayA evelopment in underground coal mining. The predominant issues An urgent need exists for an improved and safer technique forelated to drilling for rock bolting includesmounted cable bolt drilling and installation systems to improvesafety and productivity. An innovative, continuous drilling system(1)Mounted rock bolt drill rod handling is a mechanically com- will potentially meet this requirement. Such a system is not cur-plex and time-consuming task. This significantly constrains rently available to the marketthe overall performance of rock bolt installation.The water jet drilling technology currently being developed by(2)Operators drilling rock bolt holes are exposed to a high CRCMining utilises a high-pressure water jet cutting head for rapiddegree of operational risk associated with rock falls andand continuous drilling of holes of varying length, without thencorrect operation of machines [18need for manually adding or removing of drill rods as part of the(3)Mounted roof bolting machines have a large operational cable bolt installationfootprint that can constrain other mining activities in theKey benefits of凵中国煤化工ude:measroductivity in cableCNMHGOf manual drill(4)There is an industry need to more rapidly accurately and rod handling, leading un lll uPeI dLUl IISKS; step improvesafely drill rock bolt holes ranging in length from 1.5 to ments to a process which is currently one of the biggest impediments to realising rapid roadway development in undergroundS.M. Aminossadati et al International Journal of Mining Science and Technology 24(2014)363-367ncrease mining productivity and safety concurrently through theimplementation of step change technologies. The water jet drillingand fibre optic sensing are core technologies to develop a new agein Australian mining industry through future research and industryBowen, Dr E. Sheridan for their contribution to fibre optic basedgas sensing projects. These research projects were founded by autralian Coal Association Research Program(ACARP), CRCMining'sFig. 7. Water jet drilling test in progresCoal Technologies and Fugitive Emissions Research program andty of QueenslandReferences[1 AmineSM, Mohammed NM, Shemshad ]. Distributed temperaturemeasurements using optical fibre technology in an underground minenvironment. Tunn Undergr Space Technol 2010: 25(3): 220-[2 Dubaniewicz TH, Chilton JE, Dobroski H. Fibre optic for atmospheric minemonitoring. 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AA subsequent development program is now required to engimicrofabricated fibre optic sensor for methane gas measurementer the capabilities demonstrated during this project into a singleunderground coal mines. In: Proceedings of IEEE Xplore Photonics Glob.prototype tool and deployment system. This system will then be [16] Amanzadeh M. Sheridan E, Aminossadati SM, Kizil Ms,deployed into a mining environment for proof-of-concept demonMicrofabricated hollow core fibres for gas sensing usingstration and assessment trials to examine long-hole deviation andlaser application and technology. San Jose: 2013response to strata conditions[171 Aminossadati SM. Bowen W, Sheridan E, Amanzadehnovative fibre optic based methane sensor. Australian6. Conclusionssearch program report: 2013. P. C20014ickR, Steiner L Opportunitieenting equipment relatednjuries in underground coal mines in the USAEng2007:20-32his paper provides a novel research vision for undergroundcoal mines. The described technologies show that it is possible to中国煤化工CNMHG