Microseismic Monitoring Technology Research Articles

Microseismic Monitoring and 3D Finite Element Analysis of the Right Bank Slope, Dagangshan Hydropower Station, during Reservoir Impounding

The right bank slope of Dagangshan hydropower station in China has complex geological conditions and is subjected to high in situ stress. Notably, microseismic activities in the right bank slope occurred during reservoir impounding. This paper describes the microseismic monitoring technology, and three-dimensional (3D) finite element analysis is used to explore the microseismic activities and damage mechanisms in the right bank slope during reservoir impounding. Based on data obtained from microseismic monitoring, a progressive microseismic damage model is proposed and implemented for 3D finite element analysis. The safety factor for the right bank slope after reservoir impoundment obtained from the 3D finite element analysis, which included the effects of progressive microseismic damage, was 1.10, indicating that the slope is stable. The microseismic monitoring system is able to capture the slope disturbance during reservoir impounding in real time and is a powerful tool for qualitatively assessing changes in slope stability over time. The proposed progressive microseismic damage model adequately simulates the changes in the slope during the impoundment process and provides a valuable tool for evaluating slope stability.

First arrival time picking for microseismic data based on shearlet transform

Automatic identification and first arrival time picking of microseismic data play an important role in microseismic monitoring technology, and it is the precondition for real-time microseismic hypocenter location. This paper presents a novel first arrival time picking method based on shearlet transform (ST), which aims to get satisfactory results in low signal-to-noise ratio data. The ST is used to decompose noisy microseismic data. By the coefficient differences between the signal and noise at fine scales, the signal points can be preliminarily selected from the noise. To further improve the accuracy of the signal recognition, a correction to the selected signal points is made by utilizing the scale correlation between adjacent scales. The realization of the correction depends on the distances between the signal points at one scale and those at its adjacent scale. After the correction, the moment of the first identified signal point is the first arrival time. This proposed method can produce a superior performance in the accuracy of the first arrival time picking, compared with the other methods, as demonstrated using synthetic and field microseismic data. The actual picking performance of the method is further verified by receiver operating characteristic curves.

Mechanism of Integrated Dynamic Disaster of Rockburst and Water Inrush: A New Type of Integrated Dynamic Disaster in China

As the mining depths increase, an increasing number of mines in China encounter a new type of integrated dynamic disaster of rockburst and water inrush, causing great casualties and economic losses. This occurs constantly due to lacking understanding of its occurrence mechanism. This study investigated the mechanism of rockburst and water inrush as a new type of integrated dynamic disaster that has occurred in several mining areas in China. Mechanism of rockburst and water inrush mutually induced was proposed. A theoretical formula for vertical stress and floor failure depth was established and the formula indicates that dynamic stress increase lead to the floor failure depth increase, meanwhile, the thickness of aquiclude decrease. Microseismic monitoring technology was used to examine the effect of dynamic stress induced by overlying strata movement on floor failure and the results showed that the depth of microseismic events in coal floor reached the maximum 28 m when the dynamic stress reached the maximum. The finite element method was used to verify the effect of dewatering on stress distribution and the displacement of surrounding rock, and the results indicated that dewatering leads to the formation of the overlying strata settlement, vertical stress decrease in the region above the area, and vertical stress increase in the boundary region of water-rich area.

Real-time microseismic monitoring technology for hydraulic fracturing in shale gas reservoirs: A case study from the Southern Sichuan Basin

Zipper hydraulic fracturing in multiple wells with long horizontal sections is a primary solution means to increase the shale gas production rate and efficiency and to reduce the cost in Southern Sichuan Basin. Microseismic based fracturing monitoring can be used for real-time imaging of hydraulic fractures, so it has been widely used to evaluate the fracturing effect of shale gas reservoirs and to direct the optimization and adjustment of fracturing parameters. In China, however, the microseismic fracturing monitoring on fracturing of shale gas reservoirs cannot be used to evaluate the fracturing results until the fracturing operation in the pad wells is completed according to the parameters which are designed prior to the fracturing monitoring. Its evaluation results can merely provide a guidance for the fracturing parameters of the next pad wells instead of the wells in operation. As a result, the real-time effect of microseismic fracturing monitoring is out of work. In view of this, the fractures induced by zipper hydraulic fracturing in multiple shale gas wells with long horizontal sections in the southern Sichuan Basin, was real-time imaged by using the combined technology of radially arranged microseismic surface monitoring and microseismic well monitoring on the basis of real-time positioning method. The fracturing results were assessed and used in real time for the optimization of prepad fluid parameter, perforation and temporary plugging additive releasing time, so as to effectively avoid repeated fracturing and uneven fracturing effects and improve fracturing stimulation effects. This method is applied in two well groups. It is shown that the average shale gas production rate is increased by 2–5 times. Furthermore, microseismic fracturing real-time monitoring plays a vital role in real-time evaluation of fracturing effect and real-time optimization of fracturing parameters, so it can be used as the reference and should be popularized further.

Application of surface–downhole combined microseismic monitoring technology in the Fuling shale gas field and its enlightenment

The Fuling shale gas field in the Sichuan Basin, as a national shale gas demonstration area, is the largest commercially developed shale gas field in the world except those in North America. The fracturing technology in the mode of “well factory” has been applied widely in the gas field, but it is necessary to perform further investigation on the way to evaluate effectively the fracturing effect of multi-well platform “well factory” and the distribution laws of its induced fracture networks. In this paper, the fractures induced by the “well factory” at the JY 48 platform were real-time monitored by a surface–downhole combined microseismic monitoring technology. The geometric size and extension direction of artificial fractures induced in the model of “well factory” fracturing in the Jiaoshiba block of Fuling Shale Gas Field were preliminarily understood. Moreover, the fracturing parameters under the mode of “well factory” were recognized by using the comprehensive interpretation results of surface–downhole combined microseismic monitoring technology, together with the SRV fracturing prediction chart. Eventually, the distribution laws of artificial fractures during the “well-factory-zipper” fracturing in the Fuling Shale Gas Field were clarified definitely. This paper provides guidance for the optimization of fracturing parameters at the later stage.

Fractal characterization for the mining crack evolution process of overlying strata based on microseismic monitoring technology

In order to study the evolution laws during the development process of the coal face overburden rock mining-induced fissure, we studied the process of evolution of overburden rock mining-induced fissures and dynamically quantitatively described its fractal laws, based on the high-precision microseismic monitoring method and the nonlinear Fractal Geometry Theory. The results show that: the overburden rock mining-induced fissure fractal dimension experiences two periodic change processes with the coal face advance, namely a Small→Big→Small process, which tends to be stable; the functional relationship between the extraction step distance and the overburden rock mining-induced fissure fractal dimension is a cubic curve. The results suggest that the fractal dimension reflects the evolution characteristics of the overburden rock mining-induced fissure, which can be used as an evaluation index of the stability of the overburden rock strata, and it provides theoretical guidance for stability analysis of the overburden rock strata, goaf roof control and the support movements in the mining face.

Microseismic monitoring of hydraulic-fracturing programs in the Cooper Basin, Australia

In 2014, the Santos-operated Cooper Basin Joint Venture hydraulically fracture-stimulated 465 zones from tight-gas-sand and unconventional reservoirs. Microseismic monitoring technology was introduced to reduce the technical risk associated with frack programs through higher confidence in calibrated and optimized frack models for conventional-sand, tight-sand, and shale targets. This would provide cost reductions through minimizing zones of frack overlap and reserves enhancement via optimized field-development planning through targeted infill field development via early recognition of well placement, spacing and identified drainage patterns, and frack-stage spacing.

Early-Warning Model of Gas Outburst Hazard in Excavation Roadway Based on Microseismic Parameters

In order to evaluate and give a early-warning about the gas outburst risk during excavation, comprehensive indexes used to evaluate the gas outburst risk are put forward and a gas outburst early-warning model based on the normal distribution function (2σ) is created; a typical working face with gas outburst risk in Xinzhuangzi Mine of Huainan Mining Area is selected as the object of tracking and monitoring, and a microseismic monitoring system is created to track and monitor comprehensively the destruction process, destruction degree, and distribution of the coal mass ahead of the tunnel during excavation; the gas outburst risk is evaluated according to the monitoring data and using the comprehensive gas outburst risk evaluation indexes and early-warning model, and a timely and effective early warning about the gas outburst risk is given; the gas outburst indexes are used to check the effect of the gas outburst risk evaluation and early warning. The results show that the microseismic monitoring technology can provide reference for gas outburst evaluation and early warning; the comprehensive gas outburst evaluation indexes and the early-warning model (2σ) can reflect the variation trend of the outburst risk, accurately and effectively evaluate and give an early warning about the outburst risk during the excavation, and optimize the advance gas drainage drill hole design parameters to improve the gas drainage ratio, thus providing effective guidance for taking risk removal measures and ensuring safe and rapid tunnel excavation.

Study on the Underground Storage of Hazardous Waste of the Micro-seismic Signal Based on the S-transform Time-Frequency Analysis

In the disposal of hazardous waste treatment technologies due to some solid waste is difficult, costly, often stored in deep underground storage. However, the impact of surrounding rock stability of these traits would waste rock fracture can cause leakage of waste, leading to environmental pollution. Micro-seismic safety monitoring technology is an effective means to solve this problem, but to the surrounding multi-source monitoring signal is a major difficulty for signal analysis. In this paper, the optimized ST (S Transform) is introduced into the analysis of micro-seismic signal, has high-quality time domain and frequency domain information to analyze various vibration signals. The method used in micro-seismic signal processing in the underground storage of hazardous waste. The result shows that the method can be used to automatically identify and analyze micro-seismic signals.

Performance analysis of a composite dual-porosity model in multi-scale fractured shale reservoir

The multiple mechanisms of adsorbed gas and free gas lead the complexity flow in shale porous media. Shale gas reservoirs exhibit stress sensitivity permeability characteristics that are expected to have a significant effect on well performance. Meanwhile, micro-seismic monitoring technology has demonstrated that hydraulic fracturing could create only a limited complex fracture network area around fractured horizontal wellbores in unconventional reservoirs, which is very complicated and is often overlooked in mathematical models. In this paper, we conduct a comprehensive consideration of gas flow in shale reservoirs to improve the performance analysis of multistage horizontal fractured wells (MFHW). To account for the quasi-steady cross-flow between fracture and matrix consisting of viscous flow and the steady adsorption and desorption process, a dual-porosity model is employed for a stimulated reservoir region. Specifically, the stress-sensitivity effect of a fracture system was considered. An unstimulated reservoir region follows the single-porosity medium, which represents sealed natural fractures. Duhamel's theorem, the perturbation method, the superposition principle, the numerical discrete method and the Stehfest numerical inversion algorithm are employed to obtain semi-analytical solutions of the composite model. According to type curves analysis, MFHW flow regimes are given to the flow patterns, and the basic flow regimes are categorized in terms of in which time region they occur. Furthermore, the sensitivity analysis of pressure responses and early transient flow curves, including stimulated reservoir volume (SRV), stress sensitivity, fracture half-length and Langmuir adsorption volume, are carefully studied. The composite model and results can be used to expand the analysis models for multistage fractured horizontal wells in shale gas reservoirs.

Monitoring and evaluating the volume fracturing effect of horizontal well

The volume fracturing technology has been the key technology to develop extra-low permeability, ultra-low permeability, and even the tight oil and gas reservoirs. Based on the real case of a volume fracturing horizontal well in Jilin Oilfield, the microseismic (MS) technology was used to monitor the effect of volume fracturing, and the MS monitoring results were analyzed. Using the data of fracturing operation and MS monitoring, a single-well numerical simulation model with stimulated reservoir volume (SRV) was built, to evaluate the volume fracturing effect of horizontal wells. The results of the study show that the MS monitoring technology can predict the fracture distribution, size, and direction of the volume fracturing horizontal well. The volume fracturing technology of horizontal well can enhance the initial oil yield of single wells and cumulative oil production. Both of the volume fracturing and CO2 miscible flooding technologies are effective methods to develop tight oil reservoirs.

Microseismic Monitoring and Numerical Simulation Research of Floor Failure Depth in Extra-Thick Coal Seam

Based on the condition of fully mechanized caving face in one mine, two methods of microseismic monitoring and numerical analysis were combined to study the evolution characteristics and development law of floor failure depth in extra-thick coal seam. Microseismic monitoring results show that the number of microseismic events partly reflects the influence of mining disturbance in the roof and floor rock mass. The distribution of microseismic events are intensive near the coal mining face, which show the floor rock mass is seriously damaged during the coal mining. The greatest floor failure depth estimated from mine microseismic monitoring is 31 meters. Numerical analysis indicate that the rock stress around the mine stope is redistributed during the coal mining, due to the effect of mining disturbance. The abutment pressure increases in front of the coal mining face and the stress reduces in the mined areas. The concentration and release of the stress makes contribution to the destroy of the floor rock. The maximum floor failure depth is up to 28 meters calculated from numerical simulation. The consistency of microseismic monitoring results and numerical analysis improve that it is effective and reliable to obtain floor failure depth and considerably possible to predict the water inrush using microseismic monitoring technology with its inherent ability to remotely monitor the progressive failure caused by mining. The research results have great popularization and application values for the similar mine.

A short history of the shale gas phenomenon in North America

SUMMARY The oil and natural gas energy supply situation changed dramatically in the United States and in North America between 2000 and 2013. A new ability to extract economically both natural gas and oil from shale resource rocks has recently made the United States the world’s largest producer of natural gas and reversed a long-term decline in oil production. The economic impact of these changes is not only being felt in North America, but throughout the world, as the United States supplies more of its energy needs from domestic sources and prepares to export liquefied natural gas (LNG) globally. The technology and business models that created this revolution are now being tested to various degrees throughout the world. Even if the export of these models is only partially successful, it will have a profound impact on many of the current producers and consumers of fossil fuels, and on industries which support shale resource exploitation. A major beneficiary of the shale resource explosion is microseismic monitoring technology. Monitoring fracture stimulations in shale is a large and growing service industry with rapidly evolving capabilities, and concerns about induced seismicity associated with the disposal of waste water from fracture stimulation operations are starting to create a similar demand for long-term microseismic monitoring services.

Tunnel Support Parameters Optimization Based on Micro-Seismic Monitoring

The monitoring is important to keep tunnel engineering construction stability. But, regular monitoring means cannot detect the position of the rock which has much stress accurately, accordingly, cannot monitor the influence of the construction process. In order to detect the local surrounding rock cracking due to excavation, a new method named micro-seismic monitoring is proposed to identify the elastic wave of rock bursting. Micro-seismic monitoring technology can find the bursting position by use the elastic wave of the rock, then, it can make an evaluation about the stability of the rock. In the method, using several sensors monitoring data of elastic wave identifies the bursting location. Then, the stability of the rock is analyzed and tunnel support parameters are optimized. At last, the method is used to monitor the Yuanyanghui tunnel located in Shanxi Province, China. The monitoring results identified the relatively stable and relatively unstable area. In-situ measurements on the surrounding rock have been used in the two areas, and therefore we use the analysis results to improve the initial tunnel support parameters.

Application of micro-seismic monitoring technology in mining engineering

Micro-seismic phenomena, occurring when rock masses are subjected to forces and failures, allow the determination of their unstable states and failure zones by analyzing micro-seismic signals. We first present the principles of micro-seismic monitoring and location, as well as an underground explosion-proof micro-seismic monitoring system. Given a practical engineering application, we describe the application of micro-seismic monitoring technology in determining the height of a “two-zone” overburden, i.e., a caving zone and a fracture zone, the width of a coal-pillar section and the depth of failure of a floor. The workfaces monitored accomplished safe and highly efficient mining based on our micro-seismic monitoring results and provide direct proof of the reliability and validity of micro-seismic monitoring technology.

Microseismic Monitoring System Establishment and its Application to Xinzhangzi Coal Mine

Microseismic monitoring technology is the important method for safety monitoring of coal mine. The Xinzhuangzi coal mine is high gas and outburst mine, in order to ensure safety in process of mining and tunneling, the microseismic monitoring system is built. Waveform analysis database of microseismic information and interference signal is built, the results of microseismic monitoring is preliminary analyzed. The results showed that microseismic monitoring system is stable and reliable, and the results are accurate. Microseismic monitoring technology provides a new monitoring tool and method for coal mining.

Research on inversion high mining pressure distribution and technology of preventing dynamic disasters by MS monitoring in longwall face

Under two rock strata combination conditions, over 10,000 microseismic events were received with microseismic location monitoring technology which possessed by the author’s studying team, used in fully mechanized coal face of Huafeng Mine of Xinwen Coal Mining Group Co., Shandong Province. On the basis of the achievement of the location results, the conclusions were drawn as follows: On the basis of the achievement of 3D strata fracturing situation and the section plane of microseimic events in different areas, the relationship between spatial structure of overlying strata and mining pressure field was found, and we might describe distribution range of dynamic pressure of advance pressure and lateral stress around long face, and range of structure ad-tivation. Quantitative guidance to prevent dynamic disasters was provided. The practice in coal mine got a effective results. According to the FLAC3D soft numerical simulation of diameter drilling hole (the diameter is 300 mm) to relieve pressure in specified geological condition in Huafeng Mine, the right distance of two dirlls is 2.5 m and the right depth is 12 m. The research pro-vided basic guiding and practical experiences for the underground microseismic monitoring and disaster prevention in side slopes or tunnels engineering.

Focal mechanism caused by fracture or burst of a coal pillar

As a regional, real-time and dynamic method, microseismic monitoring technology is quite an appropriate technology for forecasting geological hazards, such as rock bursts, mine tremors, coal and gas outbursts and can even be used to prevent or at least reduce these disasters. The study of the focal mechanisms of different seismic sources is the prerequisite and basis for forecasting rock burst by microseismic monitoring technology. Based on the analysis on the mechanism and fracture course of coal pillars where rock bursts occur mostly, the equivalent point source model of the seismicity caused by a coal pillar was created. Given the model, the seismic displacement equation of a coal pillar was analyzed and the seismic mechanism was pointed out by seismic wave theory. The course of the fracture of the coal pillar was simulated closely in the laboratory and the equivalent microseismic signals of the fractures of the coal pillar were acquired using a TDS-6 experimental system. The results show that, by the pressure and friction of a medium near the seismic source, both a compression wave and a shear wave will be emitted and shear fracture will be induced at the moment of breakage. The results can be used to provide an academic basis to forecast and prevent rock bursts or tremors in a coal pillar.

Local seismicity due to rockbursts and near-field attenuation of ground motion in the Kolar gold mining region, India

In rock engineering, microseismic monitoring technology has been extensively applied for the interpretation and forecast of rockburst hazards. However, highly stressed hard rocks could suffer dynamic geological hazards (rockburst) and gravity-driven geological hazards (fall of ground), both of which have distinct developmental processes and precursory features that await comprehensive exploration. Hence, in this study, we adopted microseismic monitoring and an advanced method based on the source parameters of seismic energy, seismic moment, and apparent stress (the EMS method). The source parameter space was constructed to ascertain microseismic events as stress-adjusting, deformation-driven, or energy-releasing type. The evolution of the event type and the microseismic path precisely revealed the characteristics of the hazard development. In a case study of a deeply buried tunnel, we analyzed the process by which high-stress hazards occur using the proposed method and distinguished between the respective microseismic characteristics of the rockburst and fall of ground in the development and occurrence stages. Finally, we proposed the key precursory of rockburst and fall of ground in high-stress rock masses. While deformation-driven events increase notably in rockburst, stress-adjusting events are dominant in fall of ground. Overall, this study could facilitate precise interpretation and warning about different high-stress hazards and provide effective measures to curb the development of hazards.