Welcome to SCT's own publications library which contains a collection of recent publications and other resources with reliable research about our technology.
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Understanding Fracture Distribution within Intrusive Sills the Cordeaux Crinanite a Case Example from the Illawarra Coal Measures - Luc Daigle
Published Aug, 2017Recent diamond drill hole coring by BHP Billiton Illawarra Coal was used to characterise the distribution of fracturing within the Cordeaux Crinanite intrusive body. Geological data obtained from recent exploration boreholes and surface outcrops provided sufficient information to determine the pattern and history of fracture emplacement within the intrusive body.
The Cordeaux Crinanite is an intrusive sill complex consisting primarily of thick olivine rich dolerite (crinanite) sills and thinner olivine cumulate (picrite) sills. Outcrop exposures of the complex are present along parts of Cordeaux Reservoir and form the bedrock to the Upper Cordeaxu Number 1 Dam and Upper Cordeaux Number 2 Dam and much of their catchments.
The intrusive body is roughly circular in plan with a domed top and largely planar base with local bowl shaped features. The intrusive is commonly referred to as a sill but drill intersections show that it gradually cross-cuts stratigraphy. The base ranges from approximately the Balgownie Seam to above the Bulli Seam and into the Coalcliff, the roof may extend up to the Stanwell Park Claystone. Understanding-Fracture-Distribution-within-Intrusive-Sills-the-Cordeaux-Crinanite-a-case-example-from-the-Illawarra-Coal-Measures-L.Daigle.pdf312 KB -
Sand Propped Hydraulic Fracture Stimulation of Horizontal In seam Gas Drainage Holes at Dartbrook Coal Mine - Rob Jeffrey
Published Jan, 2004Longwalls 107, 108 and 109 at Dartbrook Coal Mine contained coal with a high gas content and low permeability. Horizontal in-seam drain holes were found to have low gas production rates compared with drainage rates in previous panels. Hydraulic fracture stimulations, using water and sand, were therefore carried out in three boreholes in Longwalls 109 and 108 at Dartbrook to assess the effectiveness of sand propped fractures in stimulating gas drainage from in-seam boreholes. Boreholes 108-10-10 and 108 -7-1 were stimulated with 20 and 10 fractures respectively and, on average, 100 kg of sand was placed into each fracture. The fractures placed into LW 109 were to be mined and mapped, but operational constraints precluded mapping of these fractures.
The stimulations produced a significant increase in gas drainage rates from the two boreholes. Hole 108-10-10, which ran perpendicular to the major joint system in the seam, increased its early gas rate by a factor of about 180 while hole 108-7-1, which was drilled parallel to the joint set, increased its rate by about 22 compared to pre-stimulation rates. The stimulated gas rates continuously increased for several weeks and the higher rates were sustained for the entire period the holes were monitored. Based on the higher stimulation effect achieved in hole 108-10-10 (drilled perpendicular to the jointing) compared with hole 108-7-1 (drilled parallel to the jointing), target drainage holes drilled perpendicular (northsouth) to the jointing are better stimulation candidates.
Fracture modeling suggests the sand proppant bank may extend to 15m from the borehole. The unpropped portion of the fracture may extend to more than 40m. A purpose-built fracturing system was developed and used at Dartbrook to stimulate holes that covered most of LW109. This full-scale enhancement of gas drainage was successful and allowed efficient mining of that panel.
[Coal Operators' Conference, University of Wollongong & the Australiasian Institute of Mining and Metallurgy, 2004] Sand-Propped-Hydraulic-Fracture-Stimulation-of-Horizontal-In-seam-Gas-Drainage-Holes-at-Dartbrook-Coal-Mine-R.Jeffrey-2004.pdf265 KB -
Rock Damage Characterisation from Microseismic Monitoring - Winton Gale
Published Sep, 2017This paper outlines the concepts used to correlate rock failure with microseismic events and presents examples of microseismic monitoring together with associated computer modelling of the rock failure. This study is motivated by the need to develop improved ways to reduce ground control hazards in underground mining. Toward this end we present and compare results from numerical modelling and microseismic monitoring studies conducted at several different mine sites. Emphasis is on integrating results obtained with these tools to characterize, and thus increase our understanding of, important mine deformation processes. The ultimate goal is to use this knowledge to design mine structures, and develop mitigation
measures, that minimize specific ground control hazards. Rock-Damage-Characterisation-from-Microseismic-Monitoring-W.Gale.pdf700 KB -
Hydraulic Fracturing Applied to Stimulation of Gas Drainage From Coal - Rob Jeffrey
Published Sep, 2017Hydraulic fracturing is routinely applied to stimulation of oil, gas, and coalbed methane wells around the world. The stimulation effect is achieved in coal seams as in other reservoirs, by producing a conductive fracture, connecting the well to the coal reservoir. The conductivity of the fracture is usually maintained by placing a round and sieved sand proppant in the fracture channel. The proppant prevents the fracture faces from closing back completely on one another after the treatment. The design of the fracture treatment, therefore, centers on selecting fluids, injection rates, and slurry concentrations that will produce the desired propped fracture channel. Hydraulic-Fracturing-Applied-to-Stimulation-of-Gas-Drainage-From-Coal-R.Jeffrey.pdf501 KB -
Propogation of a Penny Shaped Hydraulic Fracture Parallel to a Free Surface, with Application to Inducing Rock Mass Caving for Mining - Rob Jeffrey
Published Sep, 2017In this paper, the problem of a penny-shaped hydraulic fracture propagating parallel to the free surface of an elastic half-space is studied. The fracture is driven by an incompressible Newtonian fluid injected at a constant rate. The flow of viscous fluid in the fracture is governed by the lubrication equation, while the crack opening and the fluid pressure are related by singular integral equations. We construct two asymptotic solutions based on the assumption that the energy expended in the creation of new fracture surfaces is either small or large compared to the energy dissipated in viscous flow. One important outcome of the analysis is to show that the asymptotic solutions, when properly scaled, depend only on the dimensionless parameter R, the ratio of the fracture radius over the distance from the fracture to the free-surface. The scaled solutions can thus be tabulated and the dependence of the solution on time can be retrieved for specific parameters, through simple scaling and by solving an implicit equation. Propogation-of-a-Penny-Shaped-Hydraulic-Fracture-Parallel-to-a-Free-Surface-with-Application-to-Inducing-Rock-mass-Caving-for-Mining-R.Jeffrey.pdf376 KB -
Estimation of the Hydraulic Conductivity of the Overburden above Longwall Panels in Coal Mines - Winton Gale
Published Feb, 2012The aim of this paper is to summarise and update the results of Australian Coal Association Research Project (ACARP) Report C13013 which relate to water inflows into a mine which occur through the overburden above and adjacent to longwall panels. The study assessed available data of inflows into underground coal mines and utilised computer simulation of water flow through fracture networks. The study concluded that flow into mines is typically via an interconnected network of pre-existing and mining induced fractures. The height above the coal seam that mining induced fractures extend is typically related to the width of the panel and the thickness of the coal extracted. However the potential for those fractures to form a connected network which can facilitate flow, is related to the amount of subsidence and the depth of mining. The study compares model simulations with measured data and provides guidelines to estimate the average hydraulic conductivity of the overburden above extracted longwall panels in Australia. Estimation-of-the-Hydraulic-Conductivity-of-the-Overburden-above-Longwall-Panels-in-Coal-Mines-W.Gale.pdf979 KB -
Hydraulic Fracturing Applied to Inducing Longwall Coal Mine Goaf Falls - Rob Jeffrey - Ken Mills
Published Sep, 2017This paper describes the first successful use of hydraulic fracturing to induce a goaf event and control the timing of caving events in Australia. Hydraulic fractures are initiated at 7 to 10m above the bottom of a thick conglomerate roof and, because of the low vertical stress magnitude relative to the other two principal stressed, grow as horizontal fractures. The fractures extend radially outward from the injection borehole into the rock until a goaf fall occurs. Hydraulic fracturing has provided a means to control the timing of windblast events and thereby significantly improved safety. The successful implementation of hydraulic fracturing at Moonee Colliery to control the timing of goaf events has enabled the mine to continue operating. Hydraulic-Fracturing-Applied-to-Induce-Longwall-Coal-Mine-Goaf-Falls-R.Jeffrey-K.Mills.pdf240 KB -
Rock Fracture Caving and Interaction of Face Supports Under Different Geological Environments. Experience from Australian Coal Mines - Winton Gale
Published Oct, 2017This paper is presents a summary of recent investigations into fracture and caving about longwall panels. The results of these investigations indicate that rock failure initiates well ahead of the longwall face. Rock fracture typically forms in response failure through the material and bedding planes. Tensile fractures also form in massive units. These fracture patterns typically create a fracture network which determines the caving characteristics encountered at the faceline. The action of longwall face supports under such conditions is to maintain confinement to the fractured ground and develop a consistent caving line. The confinement developed above the canopy under these conditions can be variable on a shear by shear basis and the operational face support procedures play an important role in stability about the face area. Rock-Fracture-Caving-and-Interaction-of-Face-Supports-Under-Different-Geological-Environments.-Experience-from-Australian-Coal-Mines-W-Gale.pdf2 MB -
Successful Application of Hydraulic Fracturing to Control Windblasts at Moonee Colliery - Ken Mills
Published Oct, 2017This paper describes the first successful use of hydraulic fracturing to induce caving events “on demand” in Australia. Moonee Colliery operate a longwall immediately below a thick conglomerate strata. This strata temporarily bridges across the extracted longwall panel to create a large area of standing goaf. When this standing goaf eventually collapses, the windblast generated presents a significant hazard to men working on and around the longwall face.
Hydraulic fracturing has been successfully introduced to take control of the timing of these caving events so as to eliminate the risk of windblast injury. The longwall face area is completely evacuated during the treatment. Water is pumped into an injection point located in the conglomerate strata above the standing goaf.
A horizontal fracture is generated and grows outward from the injection point, separating the conglomerate strata below the fracture horizon. At some point the strata can no longer span and a goaf fall is initiated. After a treatment, mining can be recommenced with the windblast hazard eliminated. Successful-Application-of-Hydraulic-Fracturing-to-Control-Windblasts-at-Moonee-Colliery-K.Mills.pdf221 KB