A Clearer Image

Glenn G. Wattley and Joseph T. Duncan

World Coal December 2002

Palladian Publications Ltd15 South Street

FarnhamSurrey

GU9 7QUUK

Tel: +44 (0)1252 718999Fax: +44 (0)1252 718992

TThe day that man harnessed the beast toshare his burden, the pursuit to improveproductivity began in earnest. With theadvent of the steam engine, the industrialrevolution created a quantum leap inhuman output and our standard of living.Information technology (IT), coupledwith advanced technology, has againaccelerated productivity. The impact ofthis extends beyond the office, includingin the mine.

This article addresses how the integra-tion of IT with exploration technologiescan reduce the miner’s burden andincrease output. Software applications ofadvanced geologic modelling can now pro-duce 3-D and 4-D images, with the fourthdimension in real time. The benefits aremeasurable and include reduced risk,improved health and safety, higher pro-ductivity and better financial performance.

Imaging the coal seam Probably the most significant operationalrisk in coal mining is probably dealingwith the unknown factors, such as the loca-tion and size of geologic anomalies hiddenin the reserve. This risk increases as miningoperations become larger in scale andmove deeper into the earth. In order toadequately assess the geologic and mininghazards that may be encountered, miningengineers seek greater information thanborehole data can provide.

Standard practice for using exploratorydrill holes is to assume that each hole has aradius of influence of 0.25 miles. Withinthis radius, the coal seam is projected tohave physical properties equal to that partof the seam drilled through. However, theobvious question still remains: does thatone hole really provide the data needed toreveal anomalies within the measured

distance, or is it possible that anomalousconditions may exist just inches away?Exploration holes certainly identify andconfirm a property’s potential for miningbased on a statistical analysis of the bore-hole pattern. However, to adequately dealwith the risks of confronting sandstonechannels, dikes, faults, etc., a small sampleof boreholes cannot pinpoint a troubledarea unless they are actually drilled intothe formation. Certainly, more informationthan a coring with an area of perhaps1.61 m2 (25 in2) is needed to represent con-ditions of 125 acres.

Fortunately, technologies exist that pro-vide information beyond the borehole. Onesuch system, the radio imaging method(RIM™), is based on electromagnetic (EM)waves at radio frequencies and a geologicregime’s effect on its propagation behav-iour. Since its introduction into mining in

Reprinted from World Coal • December 2002

A clearer imageGlenn G. Wattley and Joseph T. Duncan, Stolar Horizon, Inc., US, explain how information technology can be used to produce geologic images, thereby improving productivity and reducing risk.

Figure 1. RIM tomographic image of a longwall coal panel. Figure 2. Downhole RIM IV being used in a vertical borehole.

the early 1980s, over 500 surveys have beenperformed in the US, Canada, the UK andAustralia. Coal seams act as waveguidesfor low-frequency EM waves (20 kHz - 1MHz), and any changes in an EM wave’ssignal strength or phase position can pro-vide the data needed to identify and locategeologic anomalies. The data, processedthrough tomographic inversion modelling,can provide 2-D and 3-D images of the coalseam and any anomalous zones that it maycontain (Figure 1).

The industry trend is to mine widerfaces (approximately 1100 ft) and longerpanels (over 15,000 ft) to improve longwallproductivity. The greater surface area of amining face provides greater production tto amortise fixed costs such as equipmentinvestment and setup, but larger panelsgreatly increase the probability of encoun-tering anomalies. Based on StolarHorizon’s database at the Stolar GlobalCenter for Geologic Interpretation(SGCGI), on average a coal seam anomalyis encountered every 1000 ft within a long-wall panel. In 20% of these cases, theanomaly is serious enough to reduce orstop production. In fact, many mines haveexperienced costly interruptions of pro-duction because of bad, unforeseen geolog-ic conditions.

To reach the wider panels, the RIM equip-ment has been upgraded (RIM IV). Thismakes it possible to traverse the width ofmost panels (capabilities up to 1800 ft) andto use the signal’s phase-shift information

to improve its signal-to-geologic noise(S/N) ratio. The combination of a highS/N ratio and the ability to process phaseshift and signal strength means that RIMimages can be produced with greater reso-lution than ever before.

Fortunately, IT and software modelshave developed alongside the need forenhanced imaging. Formulated byresearchers at Sandia NationalLaboratories, a Full-Wave Inversion Code(FWIC) software-modelling package canbe used to process data collected on RIMIV surveys. FWIC processing creates thehighest resolution 3-D images available forRIM data. The practice of such imaging isalready common in the oil and gas indus-try. The use of IT tools greatly improves thepicture of the coal reserve, which willgreatly improve the mining engineer’smine plan and avoid costly encounterswith anomalies.

In addition to enhancing the images andcontent of 3-D RIM, the IT revolution isreducing the time it takes to process surveyresults. Notebook computers and theInternet are truly ‘shrinking’ the world. Atthe SGCGI, a virtual organisation is able tosave considerable time in deliveringresults.

IT in action In two recent assignments, considerabletime was saved, providing mine manage-ment with critical geologic informationfor immediate operations decisions by

management. RIM surveys were conduct-ed in remote locations, but were supportedby experts ‘distributed’ around the world.The onsite teams used notebook computersto transfer field data via the Internet toother experts, who are part of the virtualSGCGI organisation. Preliminary interpre-tation and analyses were conducted anddelivered back to the onsite teams within a24 hour period. One team incorporated theanalysis into a PowerPoint presentation,which was presented to the mine manage-ment so that they could receive a briefingof preliminary results before the field teamleft the mine. The preliminary resultsenabled the management to make the deci-sion to continue mining through an anom-aly, to better mining conditions, instead ofabandoning the longwall panel.

Following the survey, communicationvia the Internet continued as the SGCGIexperts (based in Raton, New Mexico, US;Boston, Massachusetts, US; and NewCastle, Australia) worked to enhance theinterpretation. They electronically drafted,assembled and edited final reports, com-plete with figures of the mine maps, panelseam thickness and positions of anomalies.The final reports were delivered to the cus-tomer via e-mail within a week. Five yearsago, the process would have taken at leastthree to four weeks. In the near future,geologists and mining engineers at remotemine sites will be able to interact with theSGCGI proprietary models in real time viathe Internet.

View of the future Too often, a thorough assessment of geol-ogy is neglected until it is too late. Overthe past few years, there have been sever-al examples around the world where theadvance of a longwall shearer wasslowed considerably or stopped altogeth-er due to uncharted anomalies and faults.Finding a sandstone channel in a long-wall panel after the shearing machine hasstarted mining on the face is an expensiveand disheartening experience. A morecost-effective exploration program inadvance of mine planning can establish amore comprehensive understanding ofthe reserve.

To develop reserve information as earlyin the process as possible, RIM surveys canbe conducted downhole well in advance ofmining (Figure 2). Many such surveyshave already been carried out. Downholesurveys have proven to be cost-effective inidentifying and locating geologic anom-alies and abandoned mine workings

Reprinted from World Coal • December 2002

Figure 3. DSR assembled for field testing.

within coal seams. Such techniques can establish the integrity of barrier pillars; therecent underground flood at the QuecreekMine in Western Pennsylvania, US, hashighlighted the need for a serious evalua-tion of the process of reserve definition.Governor Mark Schweiker’s SpecialCommittee investigation into the detectionof old mine works has made many recom-mendations in this area.

With the increase in drilling for coalbedmethane (CBM), new opportunities existfor enhancing reserve information. Thetrend is to perform directional drillingfrom the surface with horizontal holesmid-seam. Horizontal holes will enhanceCBM recovery without sterilising theseam. Advanced guidance and detectiontools are being developed and tested towork with existing RIM probes for cross-well imaging. The benefit for mine (or oiland gas) planners is that the CBM opera-tion can be viable and profitable with newtechnology support by IT. In the future, acomplete assessment of the reserve (seamthickness, anomaly locations, etc.) willessentially be provided as a free byprod-uct of CBM drilling.

The logging of geologic data willbe ‘information intensive,’ i.e. critical

communication and data processing willtake place. A CBM guidance unit calledthe Drill-String Radar (DSR™) will be a‘measurement while drilling’ (MWD)tool (Figure 3). Using the DSR on a drillstring just behind the downhole drillmotor, enables critical geologic data suchas coal seam thickness and roof and floorstructure to be measured in real time.Results have indicated that the DSR withMWD capability will reduce wellheadcost by up to 45%. In a case study of aproject at a western US field, wellheadcosts fall from approximately US$ 1.05 toUS$ 0.57/million Btu. Up to 30% of thedrilling cost reduction will be realised bykeeping the drill string mid-seam. Theother 15% will be realised throughenhanced recovery.

In addition, the MWD data (collectedin real time as the fourth dimension) andcrosswell RIM signals can be used todevelop 3-D images of the entire propertyprior to final mine planning efforts.Considerable risk reduction will takeplace when mining engineers are provid-ed with such complete reserve informa-tion. Longwall panels will be designed toavoid major faults, igneous dikes andsedimentary channels. With more

accurate reserve definition, more appro-priate equipment selection can be made,all driven by enhanced IT equipment andsoftware.

One final benefit of using enhanced ITand advanced technology for better plan-ning and risk reduction is that the financialcommunity will respond with better termsof investment. Future projects may indeedfind it difficult to secure funding if the riskassociated with geology is not adequatelyaddressed.

ConclusionThe advancement of geologic investigativetechnologies coupled with upgraded ITsoftware/models and hardware has had asignificant impact on improving the quali-ty of geologic intelligence. This improvedknowledge greatly reduces risk andimproves operational and financial perfor-mance. Advanced RIM systems and theSGCGI are delivering greater intelligencein less time, so mine management canmake more informed decisions. With CBM,the DSR reduces wellhead cost and pro-vides useful seam information for futuremining activity as a free byproduct. Theadvancement of IT is paying off in the min-ing industry._________________________�

Reprinted from World Coal • December 2002