A Study of Spatial Distribution of Induced Seismicity in the Upper Silesian Coal Basin

The Upper Silesian Coal Basin (USCB) is a region where high seismic activity is observed. Most of these seismic events have a local magnitude not exceeding 2.3. Their location and type of focal mechanism suggest that they are connected with new discontinuities in the rock mass caused by mining activity. Shocks with higher magnitude are also observed but their frequency is much lower. The strong events have a different focal mechanism than the low energetic events. The spatial distribution of shock epicentres is not uniform in the USCB area and shows the fractal character of seismic phenomena. Despite extensive mining activity throughout the area, the epicentres of strong events are concentrated in four regions belonging to different geological units. The temporal variability of epicentre co-ordinates and the general decrease of seismic activity points to the migration of seismicity across the investigated area. Analysing the spatial and temporal distributions of the strongest shocks, one can suppose this area to be critically self-organised. These facts suggest that induced seismicity in the USCB is triggered by a nonlinear dynamic process, having regional character and connected with recent tectonic activity.     

Seismicity and fault aseismic deformation caused by fluid injection in decametric in-situ experiments

Seismicity induced by fluid perturbations became an important societal concern since felt earthquakes (M_w up to 6) occurred after anthropogenic activities. In order to mitigate the risks associated with undesired seismicity, as well as to be able to use the micro-seismicity as a probe for in-depth investigation of fluid-driven processes, it is of crucial importance to understand the links between seismicity, fluid pressure and flow. We have developed a series of in-situ, decameter-scale experiments of fault zone reactivation by controlled fluid injection, in order to improve the near-source geophysical and hydromechanical observations. The deployed geophysical monitoring close to the injection allows one to cover the full frequency range of the fault responses from the static deformation to the very high-frequency seismic emissions (up to 4 kHz). Here, we focus on the microseismicity (M_w ∼ –4 to –3) recorded during two fluid injection experiments in low-permeable shale and highly-fractured limestone formations. In both experiments, the spatio-temporal distribution of the seismic events, the energy balance, and the seismic velocity changes of the fractured medium show that most of the deformation does not actually emit seismic signals. The induced deformation is mainly aseismic. Based on these high-resolution multiparametric observations in the near-field, we therefore proposed a new model for injection-induced seismicity: the seismicity is not directly induced by the increasing fluid pressure, but it is rather triggered by the stress perturbations transferred from the aseismic motion caused by the injection.     

Mechanism of Underground Fluid Injection Induced Seismicity and Its Implications for CCS Projects

CO₂ capture and storage projects must consider the potential possibility ofinjection induced seismicity. Moderate earthquakes and strong earthquakes may endanger human life and property, and even felt earthquakes and microquakes also pose a threat to seal integrity of CO₂ reservoir and increase the risk of leakage. Underground fluid injection induced seismicity usually happens in some geoengineering projects such as waste fluid disposal, EOR and EGS, and it occurs when fluid is injected along the fault. Therefore, it can be studied through stress analysis. The density of supercritical CO₂ is smaller than water, which may develop density flow in the deep strata or water-rock interactions in pre-existing structures, and cause the variation in permeability and pressure to induce a seismic activity. In this paper, we reviewed the mechanism of underground fluid injection induced seismicity with the focus of CCS, combined with fluid injection projects and seismic monitoring analysis in both commercial scale and experimental scale, to investigate its impact on the integrity of the cap rock of the reservoir. Finally, we summarized the appropriate site selection, injection methods and monitoring programs to prevent the occurrence of induced seismicity.     

基于SOS微震监测系统的综放工作面来压周期分析

针对综放回采工作面老顶来压时易发生冒顶冲击地压事故,某矿1305综放工作面采用波兰矿山研究总院研制的新一代SOS高精度微震监测系统,对工作面自开切眼回采开始进行全程时时连续监测。统计分析微地震事件、事件发生频率及事件总能量的周期性变化,从而推断出老顶断裂的周期性。再经过理论计算验证系统的准确性。结果表明:工作面的周期来压与矿震事件能量的周期变化存在相对应的关系; 强烈微震活动发生前有一段弱震活动时期,为强震的发生积蓄了更多的能量; 周期来压时释放的总能量在某一特定水平波动,但波动的变化不稳定性增强。该结论对工作面安全回采及预防矿震冲击地压的发生具有一定的现实指导意义。     

流体替代的地震反射振幅特征分析

在油田的开发阶段,注水或注气开采会引起储层物性的变化,同时储层所含流体也会发生改变,这就为时移地震监测提供了可能.笔者主要基于Gassmann方程,详细地论述了孔隙流体替代储层地震波速度和密度变化规律,并且根据预测的结果建立了含水饱和度变化地震地质模型.最后通过对该模型的振幅类地震属性分析,对地震属性进行了优选,找到了适合本工区时移地震监测的敏感性振幅属性,为预测工区剩余油的分布提供了基础.     

三维地震在铁法矿区的应用

以铁法矿区采区三维地震工程实践为例,论述了三维高分辨率地震勘探技术在采矿工作面合理布置等方面的作用。采掘实践证明,三维地震勘探成果的应用消除了地质风险,已回采的几个综采工作面,未发生意外及重大地质变化。      

A review of theories of mechanisms of induced seismicity

Theories of the physical processes leading to the stimulation of seismic activity by underground explosions, fluid injection, and reservoir impoundment are summarized. In all cases, the materials must be pre-stressed to a substantial fraction of their breaking strength in order for seismicity to be induced. Stress concentrations due to the presence of old faults or to inhomogeneities in the material properties play an important role in localizing induced seismicity.

For the few cases for which data are available, the stimulation of earthquakes by fluid injection in bore holes is adequately explained by a Coulomb-Mohr failure criterion and the concept of effective pressure in a water-filled porous mechanism. Reservoir-related earthquakes are most likely due to the same mechanism, but, in view of the low injection pressures, additional physical or chemical effects of the water on the materials may play an important role. There may be a weakening of the materials in old fault zones by the introduction of water or static fatigue in silicate rocks due to stress corrosion.     

储集层中高压流体引爆强地震的机理——以5.12汶川地震为例

目前产生地震的机制仍以弹性回跳说为主:地震是因为断层错断使岩层的弹性能释放而引发.但越来越多的学者开始质疑,仅断层错断后的弹性能,是否真能达到实际地震所释放的巨大能量.因此,有必要探讨地震初动后破坏性强震的性质及其真正的能量来源.文章根据沉积地层中的储集层及其压力的特点分析得出,储集层内含有大量的高压流体,其压力在一定...     

The relationship between seismic and aseismic motions induced by forced fluid injections

The injection of fluid into a rock mass results in variations of effective stresses that sometimes generate induced seismicity. These effective stress field variations depend on the diffusion process, which depends, in turn, on the magnitude of the pore pressure variation relative to the total stress. Four diffusion mechanisms are distinguished: diffusion through a poroelastic rock mass, and diffusion in preferential directions controlled either by slip along preexisting fractures, or by the development of fresh shear zones, or by hydraulic fracturing. More importantly, in some instances, this diffusion process also generates non-seismic motions that, in turn, influence the seismic activity, in particular when injection stops.     

“物探+遥感”技术在矿山生态修复中的应用——以邢台园博园为例

矿山经过多年开采,地下形成采空区,造成地面沉降,开展绿色发展、生态修复工作刻不容缓. 冀中邢东煤矿由于长期开采,造成不同程度地面塌陷,不适于人类长期居住和农业耕作,邢台市经研究决定在采煤塌陷区建设中央生态公园——邢台园博园. 基于此,通过收集分析研究区内的地震、电法等物探资料,确定煤矿煤层赋存形态、采空区范围及富水情况,指导地面进行生态公园选址;利用遥感技术监测矿山生态修复进度. 研究表明:在矿区开展地震、电法工作查明煤矿开采生产情况,对科学规划地面矿区生态修复工作具有指导意义;利用遥感技术实时动态监测矿山生态修复进程,可为生态环境修复提供数据基础,对治理前后生态环境变化对比分析及效果评价提供影像资料.     

The availability of hydrogeologic data associated with areas identified by the US Geological Survey as experiencing potentially induced seismicity resulting from subsurface injection

A critical need exists for site-specific hydrogeologic data in order to determine potential hazards of induced seismicity and to manage risk. By 2015, the United States Geological Survey (USGS) had identified 17 locations in the USA that are experiencing an increase in seismicity, which may be potentially induced through industrial subsurface injection. These locations span across seven states, which vary in geological setting, industrial exposure and seismic history. Comparing the research across the 17 locations revealed patterns for addressing induced seismicity concerns, despite the differences between geographical locations. Most induced seismicity studies evaluate geologic structure and seismic data from areas experiencing changes in seismic activity levels, but the inherent triggering mechanism is the transmission of hydraulic pressure pulses. This research conducted a systematic review of whether data are available in these locations to generate accurate hydrogeologic predictions, which could aid in managing seismicity. After analyzing peer-reviewed research within the 17 locations, this research confirms a lack of site-specific hydrogeologic data availability for at-risk areas. Commonly, formation geology data are available for these sites, but hydraulic parameters for the seismically active injection and basement zones are not available to researchers conducting peer-reviewed research. Obtaining hydrogeologic data would lead to better risk management for injection areas and provide additional scientific evidential support for determining a potentially induced seismic area.     

地下采矿诱发山体崩滑地质灾害研究现状与展望

地下采矿活动诱发的山区崩滑地质灾害已经对人类活动带来了重大影响.针对采动滑坡地质灾害的发生机制,总结了近年来国内外的主要研究工作与成果,并分别从现场监测、物理模型实验研究和数值模拟实验研究3个方面对采动滑坡失稳机理进行了归纳和总结,得出如下认识:(1)已有的研究对小规模不充分开采引起的山体移动规律研究不清楚.认为地下开...     

Seismicity and faulting attributable to fluid extraction

The association between fluid injection and seismicity has been well documented and widely publicized. Less well known, but probably equally widespread are faulting and shallow seismicity attributable solely to fluid extraction, particularly in association with petroleum production.

Two unequivocable examples of seismicity and faulting associated with fluid extraction in the United States are: The Goose Creek, Texas oil field event of 1925 (involving surface rupture); and the Wilmington, California oil field events (involving subsurface rupture) of 1947, 1949, 1951 (2), 1955, and 1961. Six additional cases of intensity I–VII earthquakes (M < 4.6) without reported faulting may be attributable to shallow production from other large oil and gas fields. In addition to these examples are thirteen cases of apparently aseismic surface rupture associated with production from California and Texas oil fields. Small earthquakes in the Eloy—Picacho area of Arizona may be attributable to withdrawal of groundwater, but their relation to widespread fissuring is enigmatic. The clearest example of extraction-induced seismicity outside of North America is the 1951 series of earthquakes associated with gas production from the Po River delta near Caviga, Italy.

Faulting and seismicity associated with fluid extraction are attributed to differential compaction at depth caused by reduction of reservoir fluid pressure and attendant increase in effective stress. Surface and subsurface measurements and theoretical and model studies show that differential compaction leads not only to differential subsidence and centripetally-directed horizontal displacements, but to changes in both vertical- and horizontal-strain regimes. Study of well-documented examples indicates that the occurrence and nature of faulting and seismicity associated with compaction are functions chiefly of: (1) the pre-exploitation strain regime, and (2) the magnitude of contractional horizontal strain centered over the compacting materials relative to that of the surrounding annulus of extensional horizontal strain.

The examples cited include natural systems strained only by extraction of fluids, as well as some subsequently subjected to injection. Faulting and seismicity have accompanied both decrease and subsequent increase of fluid pressures; reversal of fluid-pressure decline by injection may enhance the likelihood of subsurface faulting and seismicity due chiefly to earlier fluid pressure reduction. A consistent common denominator appears to be continuing compaction at depth; the relative effects of fluid extraction followed by injection are not easily separated.     

新郑矿区地温异常成因探讨

新郑矿区地温场具有高热流,高地温梯度的特点。其地温异常与深部地壳活动无关,是本区特殊的地质构造所导致局部聚热与水文地质条件所控制的相对高温热水向上运移两种作用叠另的结果。     

Analytical investigation of hydraulic fracture-induced seismicity and fault activation

More recent public discourse has taken place regarding the potential correlation between seismic activity and hydraulic fracturing in shale gas reservoirs. Public fears about the risk of seismicity stem mainly from past earthquakes induced by conventional deep injections because the two types of projects share similar mechanisms of rock failure and fault activation. Although previous earthquake risks associated with fluid injection were not serious, the situation would be far more problematic if hydraulic fracturing in a shale gas reservoir triggered a similar-sized earthquake due to potential environmental issues. In fact, almost all documented injection-induced earthquakes have been associated with long-duration and high-volume injection rather than short-term (hours) pressurization (e.g., hydraulic fracturing). In general, hydraulic fracturing operations mostly induce microseismic events through rock failure and activation of small fractures. Although shale reservoirs in tectonically active zones pose a high risk of inducing large-magnitude seismic activities, the internal geological conditions and external stimulation conditions are impossible to be satisfied simultaneously to trigger activation of an entire fault and to result in a destructive earthquake during hydraulic fracturing operations.     

采动微地震波传播与衰减特性研究

为分析采动地震波煤岩响应及其波场特性,构建顶板岩层和煤层2种传播介质接收采动地震波的多通道微震监测系统,研究2种介质采动地震波的传播和衰减特征。研究结果表明：顶板岩层接收到采动地震波的平均波速、加速度均高于煤层,2种介质中的地震波加速度均与爆破装药量成正相关,与传播距离、介质密度负相关。采动微地震波能量、信号时长随传播距离分别呈指数、线性衰减,近爆心处煤层传播微地震波能量、信号时长均高于顶板,超过一定距离后顶板高于煤层;采动微地震波传播距离有限,顶板的有效传播距离高于煤层,地震波有效传播距离与爆破装药量线性正相关。采动地震波低频部分的品质因子高于高频部分,顶板岩层的品质因子高于煤层。研究成果有助于地震波传播介质选取、检波器布设优化。     

北海盆地维京地堑渐新统砂岩侵入体形态特征及成因

砂岩侵入体是由处于浅埋藏阶段、尚未固结的砂质沉积物发生液化并侵入到上覆盖层所形成的一类软沉积物变形,在北海盆地维京地堑渐新统地层中非常发育。为探讨砂岩侵入体的形态特征及诱发机制,通过高分辨率三维地震及测井资料,利用地震反射结构分析、地震相干切片等手段对砂岩侵入现象进行了识别;并结合多边形断层系统、流体充注与砂岩侵入之间的关联性,对砂岩侵入体的成因机制进行了分析。结果表明:在地震剖面上可识别的砂岩侵入体多呈V型或W型强振幅反射特征,其横向展布规模约1~2 km,垂向侵入高度约100~200 m;流体的大规模充注及多边形断层诱发盖层破裂是形成砂体内部超压并诱发其发生液化的关键因素。砂岩侵入体在形成之后可以作为流体运移通道,对强化流体的垂向运移具有重要意义;并且砂岩侵入体本身即可作为油气的有利储集体。因此识别并分析砂岩侵入体的成因机理,对盖层封闭性评价及油气勘探具有重要指导意义。     

山西煤矿采区高密度三维地震勘探综述

在对国内外高密度三维地震勘探技术研究及应用现状进行系统阐述的基础上,对高密度三维地震勘探的3个关键参数及概念进行了讨论,认为高密度三维地震勘探技术是先进地震勘探技术的集成,具有组合性和相对性,应灵活应用,因地制宜地开展。在分析了山西煤矿采区的地震地质条件及技术特点的基础上,提出了在山西煤矿采区开展高密度三维地震勘探应遵循“小面元、高覆盖、宽方位（3,必要条件）和相应的关键采集及处理技术（X,必选项） ”的“ 3+X”技术路线;在数据采集中,应以提高信噪比为核心;在数据处理中,应以高精度静校正和叠前去噪为核心。将该技术运用到山西某矿工程实例中,取得很好的效果,证明该技术路线的有效性。研究成果可为同行提供技术参考,并促进高密度三维地震勘探技术在山西煤矿采区推广。      

The impact of technogenic factors on the seismicity of the Kuznetsk Basin region and Lake Baikal

Using the materials from the catalogue of seismic events in the Siberian region, we estimated the impact of man’s activity on natural seismicity. Local man’s intervention into natural processes has been studied by the examples of commercial explosions during the quarry mineral mining in the Kuznetsk Basin and the exploitation of the railroad site along the shore of Lake Baikal. Seismic emission is shown to change with time under the impact of powerful monochromatic vibrators on the environment.     

甘肃省矿山地质灾害及其基本特征

甘肃是矿产资源大省,矿产开发利用规模大、强度高,因而矿山地质环境问题突出,其中矿山地质灾害的危害和威胁尤其严重。本文基于实际调查数据,论述分析了甘肃省矿山地质灾害的主要类型、基本特征及其危害特点。根据调查结果,甘肃省主要发育五类矿山地质灾害:采空地面塌陷、滑坡、崩塌、泥石流和矿坑突水。在这五类灾害中,采空地面塌陷分布最广、造成的直接经济损失最严重,滑坡发生频次高、造成人员伤亡最大,矿坑突水灾害分布范围、发生频次和危害程度相对最低。各类灾害的分布和发育特征受地质环境条件及矿山开采规模和开采方式的控制,灾害的危害特点与其分布和发育特征和活动特点有关。