Joint processing of surface and underground microseismic monitoring data in hard mineral mining (original) (raw)
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Applied Sciences
In the case of mining in an inclined intrusion using the block caving method, the highest stress is usually concentrated in the seismogenic and abutment zones, especially in the front of the sloping area. In an inclined intrusion of more than 40°, the seismometer network is usually distributed in the facility area where the footwall area is also located. This causes a limitation in microseismic monitoring due to ray coverage. In this study, we conduct a seismometer deployment outside a mining facilities area with borehole seismometers. The study aims to maximize the resolution and minimize the monitoring uncertainty of underground mines. We created two scenarios of seismometer deployment: (i) seismometers are deployed following the intrusion mining level in the mining facility area; and (ii) additional seismometers are deployed in off-facilities areas. Both areas were tested for their raypath responses and sensitivity using the Checkerboard Resolution Test (CRT). The monitoring reso...
Routine Micro-Seismic Monitoring in Mines
Routine seismic monitoring in mines enables the quantification of exposure to seismicity and provides a logistical tool to guide the effort into the prevention and control of, and alerts to, potential rock mass instabilities that could result in rock bursts. One can define the fol-lowing five specific objectives of monitoring the seismic response of the rock mass to mining: rescue of personnel, prevention, seismic hazard rating, alerts -including short term response to unexpected strong changes in certain parameters -and back analysis to improve the efficiency of both the mine layout design and the monitoring pro-cess. A quantitative description of seismic events and of seismicity are necessary, but not sufficient, in achieving the above objectives. The paper describes the basis of a modern digital seismic technol-ogy and seismological parameters used to quantify seismic sources and seismicity for seismic hazard assessment and rock mass stability analysis.
Relocation method of microseismic source in deep mines
Transactions of Nonferrous Metals Society of China, 2016
A new method, named relocation, was proposed to reduce the impact of sensor errors systematically, especially when available data of sensors are abundant. The procedure includes evaluating the reliability of every sensors datum, processing the initial location by the credible data, and selecting a set of equations with optimal noise tolerance according to the relative relationship between the initial location and sensors location, then calculating the final location by k-mean voting. The results obtained in this research include comparing traditional location method with the presented method in both simulation and field experiment. In the field experiment, the location error of relocation method reduced 41.8% compared with traditional location method. The results suggested that relocation method can improve the fault-tolerant performance significantly.
Application Of Microseismic Monitoring In Underground Block Caving Mine
2018
Induced mine activities could make impact to the rock’s stability. Block cave mine has some area where development of the progressing cave line and heading are disturbing and having risk to harm people working in the surrounding area. Rock mass in massive solid rock generates movement in order acting the stress that applied in the environment. Local movement in the mine where it’s caused by blasting – artificial source or passively occurs when the rock finds its stability is generating acoustic P and S waves. Microseismic monitoring system has been applied in the active mine area to ensure a safety production. This paper describes an application of real time microseismic monitoring system in underground mine operation to support a safety production.
Proceedings of the 8th International Symposium on Rockbursts and Seismicity in Mines, RaSiM8
Whilst some research has been completed in the area, the industry still does not have an accepted reliable means of locating trapped miners. A technique for locating trapped miners was developed in which miners would hit the wall or support of an excavation with a hammer or similar sized object, which would then be detected by the (pre-existing) microseismic monitoring system in the mine. As part of the project, field testing was carried out at three underground mines in Australia in conjunction with the Institute of Mine Seismology. The collected data was processed and subsequently analysed using statistical tools. Back analysis of the data from Tasmania mine was used to estimate the detection reliability as a function of distance from the sensors. A reliability of 100% was achieved up to 65 m, 90% at 84 m and 0% further than 250 m. For test sites with three sensors within 200 m, the location of the miner could be located within 46 m of accuracy 90% of the time and within 35 m 80% of the time. The average location accuracy over all located test sites was 23 m. The experience of the field testing and the results suggest that the technique could be implemented in operating underground mines (which use a microseismic monitoring system) without significant cost or effort.
Journal of Geophysics and Engineering
Precise and fast location of microseismic events plays an important role in the real-time hydro-fracturing monitoring. It provides an effective guidance to evaluate the fracturing effect, adjust the fracturing design and determine the exploitation scheme for low permeability and dense reservoir. However, currently used hypocenter location methods have some problems of either low accuracy or low efficiency especially in low signal to noise ratio (SNR) circumstances. So it is very difficult to meet the processing requirement for real-time monitoring during the hydro-fracturing operation. To solve this problem, we have developed an improved global grid search method, which simultaneously reduces the grid search range and step size upto its half until the search step size drops below a threshold during searching the optimal solution. Subsequently, this method is further extended by using back azimuth constraint and the objective function based on combination time difference in order to improve the location accuracy. The method has been successfully applied to synthetic data as well as on real microseismic data obtained from a single monitoring well which was acquired during a hydro-fracturing well stimulation. The synthetic and field data tests indicate that the proposed method is more feasible and robust than existing classical methods in low SNR circumstances. Furthermore, the proposed method may successfully find the events locations much faster and more accurately.
Advance detection of Slope Failures in Opencast Coal Mines using Microseismic technology
The application of microseismic monitoring in opencast coal mines provides an ideal method for the analysis of slope status. Since slope angles are critical to the economics of open pit mining, microseismic monitoring of fracturing within a slope can add significant knowledge to assess the status of slopes in terms of stability. An advanced high dynamic range microseismic instrumentation with latest computer methods/analysis will help to investigate strata behavior in real time. In the present study, an array of high frequency 15 Hz triaxial geophones were installed in boreholes in Opencast Coal Mine in highwall as well as dumps for monitoring the slope movements. The microseismic energy generated due to rock movements is continuously recorded by these geophones. The recorded events are stored in seismic recorder. The stored data will be transferred into a data acquisition and processing system via wireless repeater station. The data recorded are later processed for their origin of ...
2000
Experiments carried out in a working iron mine validated the microseismic monitoring technique as a means of detecting fracture noise emissions regarded as signals indicating an incipient collapse. In the experiment surface recordings were made of the microseismic signals corresponding to fractures and local collapse phenomena generated at the mine bottom by deliberately destroying pillars. The pillar removal operations and the collapse of the roof were systematically correlated with a series of microseismic events. The experiment served to validate the microseismic monitoring technique as a means of detecting surface precursors of a collapse, to demonstrate the effectiveness of the technique, and to calibrate the principal parameters of a microseismic monitoring System adapted to detection and monitoring in areas where there is a risk of collapse.
Microseismic Event Location Using Multiple Arrivals: Demonstration of Uncertainty Reduction
Proceedings of the 3rd Unconventional Resources Technology Conference, 2015
Event location is the basis of hydraulic fracture characterization using microseismic data. However, the traditional method of using direct arrival times and Pwave polarizations leads to increased error due to the large uncertainty in polarization. Due to shale's low velocity nature and the configuration of horizontal stimulation and monitoring wells, the head wave can often be the first arrival rather than the direct arrival. Finite difference modeling was used to validate the character of head waves in field data gathered from the Marcellus shale and the situations under which a head wave can be the first arrival were carefully analyzed. With careful processing, we reveal the presence of high number of head waves in the Marcellus Shale. Head wave and direct arrivals were used instead of the conventional Pwave polarization to estimate microseismic event location. A Bayesian inference program was also developed for joint event location and velocity model calibration. Validation of the developed method was performed on perforation shots and shows that using head waves instead of polarization can achieve much better resolution in microseismic event location. The application of the developed method on field data shows a more reasonable result than that provided by contractor. Our results show that the head wave can be a contributor instead of a detractor in the process of accurate event location. This will eliminate the necessity for polarization which has large uncertainty due to poor geophoneborehole coupling, multiple arrivals, and low signal to noise ratio. The developed method can effectively improve the accuracy of microseismic event location and proposes a better acquisition geometry and strategy to reduce microseismic monitoring cost and improve event location accuracy.