共查询到20条相似文献，搜索用时 156 毫秒
1.
以四川盆地为例,通过分析沉积岩储藏系统中断层的发育特征和典型沉积岩断层形成前后岩石变形破坏过程的实验研究,探讨沉积岩层中小断层在油气田注水诱发地震中的作用及较大地震发生条件。首先,通过分析已有的有关四川盆地深部注水诱发地震活动情况的资料得到具有一定普遍性的认识:诱发地震的空间分布明显受已有断层或破裂的控制,有感地震尤其是可导致一定灾害的中强地震往往都是已有断层的重新活动所致。其次,结合石油地质资料及盆地边缘地区出露的一些未成熟小型断层的地质与构造特征观察分析,发现这些断层的存在具有普遍性而且是地下油气纵向运移的主要通道。进而,在实验室条件下对四川盆地几个典型沉积岩样本进行了三轴压缩破坏实验。采用多通道宽动态高速声发射观测技术与三维X射线CT成像技术分析断层形成过程及形成后的几何特征和摩擦系数的变化。最后,通过融合各方面研究结果分析注水诱发地震的发生机制和模型,探讨了较大地震发生条件,为提升注水诱发地震评估能力和建立安全注水操作管理指南提供理论基础。该结果有助于理解为何四川盆地油气田注水诱发地震活动如此剧烈。主要的前三叠系沉积岩(包括白云岩、页岩及白云质灰岩)均具有较高的破坏强度和脆性变形破坏特征,使四川盆地油气储藏系统有条件保持较高的应力水平和在一定条件下导致地震性断层破坏。一般,一条尺度达到几km的断层便足以产生M5级别的中强地震。这些条件使得该区具有发生破坏性注水诱发地震的可能。有必要在对注水孔周围的破裂及断层构造的空间分布、尺度大小及力学性质特征有基本了解的条件下,通过注水数值模拟和监测注水诱发地震的时空演化,建立适当的统计模型实现诱发地震的统计评估和预测,指导注水操作而达到减少灾害性地震发生的风险。 相似文献
2.
3.
《地球物理学进展》2016,(2)
二氧化碳驱油不仅可以封存二氧化碳以控制全球气候变暖,而且可以提高采油率,具有十分重要的研究意义.但目前仅能简单监测二氧化碳驱油的效果和二氧化碳采出情况,驱油过程的精细监测成为薄弱环节,制约着二氧化碳驱油的进一步发展.地震法作为一种相对成熟的地球物理勘查方法,具有实现二氧化碳气驱过程描述的技术可行性.本文参考国内外研究成果,从基础研究入手,应用胜利油田二氧化碳驱先导试验区的实际数据,通过流体替换及正演模拟方法,分别对理论模型、单井资料进行二氧化碳驱油过程岩石物理参数变化分析,并进一步研究了叠前叠后地震响应特征变化规律,取得了二氧化碳驱油地震响应特征的阶段性认识,对二氧化碳驱油的地震监测相关研究工作具有一定的借鉴意义. 相似文献
4.
结合地震岩石物理技术，研究了叠前频变AVO反演在四川盆地龙马溪组页岩储层含气性识别中的应用.首先，应用Backus平均理论将测井数据粗化为地震尺度储层模型，应用传播矩阵理论进行高精度地震正演及井震标定，分析页岩气储层地震响应特征.其次，基于岩心观测结果，应用Chapman多尺度裂缝理论设计页岩气储层理论模型，研究储层衰减、频散以及对应的地震反射特征.应用该理论模型测试频变AVO反演方法，计算结果表明：对于研究区地层结构和地震数据，区分流体类型的优势频率不是地震子波的主频，还受层间调谐干涉等储层结构因素控制，也进一步说明理论模型测试和标定的重要性.最后，将频变AVO反演技术应用到四川盆地龙马溪组页岩地层，计算得到的频散属性为页岩气储层含气性识别提供依据. 相似文献
5.
《地震地质》2017,(5)
针对岩样在外载荷作用下失稳破坏前有声发射、微震和电荷等信号的异常变化特性,运用声发射、微震和电荷感应等全波形综合监测设备对含断层带花岗岩在单轴压缩下变形破裂过程的信号进行同步监测。结果表明:含断层带花岗岩在弹性变形阶段有明显的声发射、微震和电荷感应同步前兆信号,在试样失稳破坏阶段有同步的声发射、微震和电荷感应大幅值前兆信号。断层带对花岗岩试件强度的影响是显著的,含断层带试件的单轴抗压强度大大降低。随着断层带倾角的减小,试样的单轴抗压强度降低,岩样更容易失稳,失稳破坏的能量也更大。随着断层带倾角的减小,试样变形破裂过程的声发射、微震和电荷感应信号都增多,试样出现同步的前兆信号时的应力降低,在试样失稳破坏阶段声发射、微震和电荷感应前兆信号事件的持续时间都增大。断层带倾角30°时,声发射、微震和电荷感应信号突变性增加,进入危险阶段大大提前,大震级事件也显著增多,在矿井大倾角断层处更为危险。在试样失稳破坏阶段前同步产生密集且大幅值的声发射、微震和电荷感应信号,持续时间较短;在试样失稳破坏阶段同步产生密集且最强的声发射、微震和电荷感应信号,持续时间较长。声发射监测数据能较好地反映岩石的微小破裂情况,对声发射、微震和电荷感应前兆信号相结合分析,可以更准确地获得岩石失稳破坏的前兆信息。 相似文献
6.
许多大地震前地震活动存在明显的平静现象,由于其普遍性,地震平静现象被认为是具有物理意义的地震前兆并被作为地震预报的重要依据.关于大震前地震平静现象的物理机制,国内外学者从不同角度进行了研究,其中包括用破裂强度的双峰式分布、扩容硬化、震前滑动造成的应力松弛、震源体内外介质性质的差异和相互作用等机制解释强震孕育过程中短期地震活动的平静现象.尽管在一些模型中把岩石力学实验结果作为证据之一,但来自与地震活动最相似的岩石变形声发射的实验证据并不多.因为以往大量的实验结果表明,在恒定的加载条件下(等位移速率、等应力速率等),岩石破坏失稳前声发射活动多表现为加速特征,尽管一些岩石破坏前声发射活动加速现象不明显,但也难以观测到平静现象.然而,在我们开展的一系列断层结构和介质不同的中尺度标本的声发射实验中,一些标本破坏失稳前声发射活动表现出明显的相对平静现象,据此我们对大地震前地震活动平静现象的物理机制进行了讨论. 相似文献
7.
8.
9.
近年来随着我国页岩气大规模开采,四川盆地南部活动构造相对稳定的地区出现了一系列微震和有感地震,甚至是破坏性地震。这些地震是否为工业开采所诱发,目前已有研究从时空相关性给出了一些统计推断,本文则从形变观测角度分析页岩气开采能否产生可以检测到的地面形变,以揭示形变信息与页岩气开采的关系,尝试为页岩气开采提供有效的监测手段。基于长波ALOS-2卫星雷达数据对长宁页岩气区块近两三年内的InSAR地表形变展开探测,检测页岩气大规模生产可能造成的地面形变及其基本特征,同时使用Sentinel-1卫星雷达数据分析页岩气开发活跃时段内的形变时间序列信息。结果显示:考虑到不同观测技术的误差水平和观测角度差异,两种卫星数据均反映了一致的地表形变分布,且形变场与页岩气开采井的空间分布有很好的对应关系;压裂注液过程会造成地表快速隆升,生产过程中随着流体扩散地表会出现沉降和水平运动,初步揭示出页岩气生产过程中地面形变的非稳态变形特征。这表明在四川盆地南部复杂的形变观测条件下,InSAR技术是页岩气开采有效的监测手段,能够弥补地震学观测的不足。 相似文献
10.
结合微震活动的流体作用强度检测及孔隙压扩散模拟,讨论了三峡库区不同时期微震活动的主要影响因素。以2008年9月蓄水季为界划分前、后期,前期流体渗透导致的孔隙压力增加,使裂隙或断层面强度降低,是库区微震活动的主要影响因素,这一时期微震频次及ETAS模型参数μ值有起伏地缓慢增大,与库水位加卸载过程关系不明显; 后期由于流体渗透引起的孔隙压力变化趋于零,在新的流体平衡条件下,库水位加卸载过程所导致的裂隙或断层面上的应力变化,成为库区微震活动的主要影响因素,这一时期微震频次及μ值显示出与水位变化明显的关联特征。库区小震震源深度的时间变化支持上述观点。在此基础上,进一步讨论了水库“诱发”和水库“触发”地震的力学差异,认为前者主要缘于流体渗透导致的裂隙或断层面强度的“主动”降低,后者则主要与库水加卸载所导致的裂隙或断层面上应力增强有关。进一步推论认为,流体对小地震“诱发”、“触发”皆可能发生,但中强地震缘于流体“诱发”的可能性非常小,对水库区发生的中强地震,流体仅可能对处于临界状态的断层系统起到“触发”作用。 相似文献
11.
Sergei Stanchits Jerome Fortin Yves Gueguen Georg Dresen 《Pure and Applied Geophysics》2009,166(5-7):843-868
We investigated initiation and propagation of compaction bands (CB) in six wet and four dry Bentheim sandstone samples deformed in axial compression tests with strain rates ranging from 3.2 × 10?8 s?1 to 3.2 × 10?4 s?1. Circumferential notches with 0.8-mm width and 5-mm depth served to initiate CB at mid-sample length. Wet samples were saturated with distilled water and deformed at 195 MPa confining pressure and 10 MPa pore pressure. Dry samples were deformed at 185 MPa confining pressure. Twelve P-wave sensors, eight S-wave sensors and two pairs of orthogonally oriented strain-gages were glued to the sample surface to monitor acoustic emission (AE), velocities and local strain during the loading process. Nucleation of compaction bands is indicated by AE clusters close to the notch tips. With progressive loading, AE activity increased and AE hypocenters indicated propagation of a single CB normal to the sample axis. CB propagation from the sample periphery towards the centre was monitored. Microstructural analysis of deformed samples shows excellent agreement between location of AE clusters and CBs. In both dry and wet samples the lateral propagation of CBs was about 100 times faster than axial shortening rates. At the slowest displacement rate, AE activity during band propagation was reduced and CB nucleation in wet samples occurred at 20% lower stresses. This may indicate an increasing contribution of stress corrosion processes to the formation of the compaction bands. In dry and wet samples inelastic compaction energy per area ranged between 16 and 80 kJ m?2. This is in good agreement with previous estimates from laboratory and field studies. 相似文献
12.
More than a thousand acoustic-emission (AE) hypocenters were determined in a cylindrical andesite specimen under two-stage uniaxial creep at stresses of 204 and 214 MPa. Strains were monitored for 6 peripheral points at the middle part of the cylindrical specimen's wall. The strain data indicate gradual increase of nonuniform deformation during steady creep and strong intensification of the nonuniformity during acceleration creep and, therefore, biased stress distribution within the specimen. The correlation between dilatant strain and AE hypocenters was investigated for whether or not tensile cracks emit AE. The region with high AE activity shows only a small dilatant strain. This negative correlation between AE and the dilatant region may eliminate tensile cracks as possible AE sources. A composite focal-mechanism solution of local AE events, covering a wide solid angle of the focal hemisphere, indicates that shear fractures emit AE waves. The direction of the compressional axis in this solution shows a significant deviation from that inferred from the applied external force, suggesting that the local stress field is governed by preexisting weak zones that are, presumably, produced by tensile cracks within the specimen. AE hypocenters tended to form clusters during steady creep under the constant compressional stress. During acceleration creep caused by a small step increase of the external stress, the preceding clusters disappeared while a new cluster appeared in an incipient fault plane. This suggests that changes in seismicity pattern such as migrations or quiescences of swarm—important clues for earthquake predictions—may be caused by an instantaneous change in the tectonic-stress levels. 相似文献
13.
本文在实验室对所获取的东营地区层理发育的低孔隙度页岩和泥岩的各向异性裂纹演化特性进行了研究,获得了各向同性条件下泥页岩的力学与超声波响应特性,分析了应力幅度对于页岩声波速度和各向异性的影响.主要结论包括:(1)泥页岩在循环载荷下存在滞后效应,表明其经历了去压实或油气产生导致的超压;(2)泥岩和页岩具有不同程度的各向异性,随着各向同性压力的增高微裂隙逐渐闭合,样品的各向异性程度减弱;(3)分析了岩石韧度和裂纹损伤参数随压力的变化特征,相比泥岩,页岩各向异性程度更高,随压力变化更明显,其裂纹导致的附加各向异性更强;(4)分析了各向异性岩石的动态弹性模量特征,由于软裂隙空间的闭合,动态弹性模量在低压条件下都随着围压的增加有硬化趋势. 相似文献
14.
人工诱发地震现象已经有很久的历史.水库蓄水、采矿、地热开发、从地下提取液体或气体,或将液体注入地球内部都可能诱发地震.大量地震监测数据与科学分析结果显示:美国俄克拉何马州的地震剧增主要与页岩油气开采的废水回注量相关;加拿大阿尔伯塔省的地震剧增主要与页岩油气开采水力压裂的工作量相关;而荷兰罗宁根天然气田的传统天然气开采也同样诱发了较强的地震活动.在中国四川盆地的页岩油气开发区域,地震活动近几年也大幅度增强,但目前监测与科研工作较少,对某些地震成因尚有争议.目前研究诱发地震问题已成为学术界与工业界的一门专业学科.推断诱发地震,除了分析时空分布与工业活动的相关性之外,本文综述了该领域基于地震学、地质动力学、构造地质学的多种分析方法.如何在油气开采过程中减少诱发地震的灾害影响成为当前相关各界极为关注的科研问题,本文介绍了多个国家或地区建立的控制诱发地震的管理系统、基于地震大数据的诱发地震概率预测方法,以及基于地球物理与地质信息的综合诱发地震风险评估方法,并对我国控制诱发地震问题提出建设性意见. 相似文献
15.
循环加载高压流变实验中塑性应变分析 总被引：1，自引：0，他引：1
在三轴应力下的流变实验中，通过循环加载方法测出轴向应变，轴向塑性应变和弹性模量随差应力的变化，再根据多孔介质有效弹模理论，计算出岩石变形中孔隙度的变化，在假定岩石骨架不可压缩下，得到体积膨胀应变，然后通过总塑性应变与扩容机制和位错机制应变的关系，分解出位错应变，结果表明：在低围压下（＜100MPa），扩容应变占优势，并伴随着部分位错应变，在高围压下（＞100MPa），位错应变占优势，只有较小的扩容应变。 相似文献
16.
对经过三向预加压的石灰岩试件所进行的试验研究表明,其声发射活动的特点与单向受力时的情况完全不同。此时,在一个试件的一次加载过程中会出现两次Kaiser效应,分别对应于载荷达到预加压时所施加的轴压与围压值之时。利用回归分析的方法来处理试验数据,可以使声发射活动对应力的响应关系用三条回归直线来近似。这三条直线的两个交点所对应的应力值,可以确定出预加压时岩石试件承受的应力状态 相似文献
17.
The seismic velocity and attenuation of fully saturated shales were measured for the first time under overpressured conditions, using the ultrasonic reflection technique. Shale cores from naturally overpressured horizons in the North Sea were tested in the laboratory, at confining and pore pressures relevant to in situ conditions.
A single-frequency tone-burst pulse wave was used to determine the seismic wave velocities and quality factors of the shale samples, with errors less than 0.3% and 0.1 dB/cm, respectively, at a frequency of 0.75 MHz. Sample length changes with varying confining and pore pressure were measured and the pore pressure equilibration time was monitored for each sample.
The anisotropy of the seismic attributes ( Vp , V s , Q p and Q s ) was determined over a range of differential pressures from 5 to 60 MPa, with respect to the predominant foliation. The ultrasonic velocity data followed a transversely isotropic pattern depending on the direction of wave propagation with respect to the laminations. The Poisson's ratio was found to rise by 5% as the shale material progressed from a normally pressured to an overpressured state. The quality factor ( Q ) characteristics were interpreted in terms of pore geometry and connectivity as well as the directional permeability of the transversely isotropic shale material. The results were converted to bulk and shear loss modulus defects, and a positive bulk loss was observed for waves propagating perpendicular to the lamination plane even above differential pressures of 20 MPa. This indicates different levels of Biot-flow and squirt-flow attenuation mechanisms acting within the shale structure, depending on the wave propagation and vibration directions. 相似文献
A single-frequency tone-burst pulse wave was used to determine the seismic wave velocities and quality factors of the shale samples, with errors less than 0.3% and 0.1 dB/cm, respectively, at a frequency of 0.75 MHz. Sample length changes with varying confining and pore pressure were measured and the pore pressure equilibration time was monitored for each sample.
The anisotropy of the seismic attributes ( V
18.
准确确定水力压裂诱发地震的震源机制对于描述裂缝破裂类型以及工区地应力状态十分重要.本文采用全波形匹配的方法确定诱发地震震源机制解，在拟合波形的同时对实际数据P波初动极性和纵横波振幅比也进行匹配，并在此基础上发展了一种基于邻域算法分级优化确定震源机制解的新方法.新方法的优势在于它对解具有更强的约束，并且能够解决现有方法中存在的权值系数选择问题.合成数据测试结果表明新方法能够得到可靠的震源机制解.本文将该方法应用于国内某页岩气田水力压裂诱发地震监测数据，反演结果表明诱发地震的震源类型以走滑破裂为主，表明该地区的最大水平主应力大于垂直主应力. 相似文献
19.
Karthala volcano is a basaltic shield volcano with an active hydrothermal system that forms the southern two-thirds of the Grande Comore Island, off the east coat of Africa, northwest of Madagascar. Since the start of volcano monitoring by the local volcano observatory in 1988, the July 11th, 1991 phreatic eruption was the first volcanic event seismically recorded on this volcano, and a rare example of a monitored basaltic shield. From 1991 to 1995 the VT locations, 0.5<Ml<4.3, show a crack shaped pattern (3 km long, 1 km wide) within the summit caldera extending at depth from –2 km to +2 km relative to sea level. This N-S elongated pattern coincides with the direction of the regional maximum horizontal stress as deduced from regional focal mechanism solutions. This brittle signature of the damage associated with the 1991 phreatic eruption is a typical pattern of the seismicity induced by controlled fluid injections such as those applied at geothermal fields, in oil and gas recovery, or for stress measurements. It suggests the 1991 phreatic eruption was driven by hydraulic fracturing induced by forced fluid flow. We propose that the extremely high LP and VT seismicity rates, relative to other effusive volcanoes, during the climax of the 1991 phreatic explosion, are due to the activation of the whole hydrothermal system, as roughly sized by the distribution of VT hypocenters. The seismicity rate in 1995 was still higher than the pre-eruption seismicity rate, and disagrees with the time pattern of thermo-elastic stress readjustment induced by single magma intrusions at basaltic volcanoes. We propose that it corresponds to the still ongoing relaxation of pressure heterogeneity within the hydrothermal system as suggested by the few LP events that still occurred in 1995.Editorial responsibility: H Shinohara 相似文献
20.
动三轴试验中,若在一定轴向静偏应力基础上施加对称正弦波荷载,土体会在荷载正半部分出现轴向压缩状态,而在荷载负半部分有可能因为侧向应力大于轴向应力而出现轴向等效拉伸状态,将此类荷载暂称为等效拉压荷载。为研究等效拉压荷载下饱和粉质黏土的弹塑性变形,设计了多级正弦波荷载室内不排水动三轴试验。依据试验数据揭示了围压、静偏应力、动偏应力和压实系数对土体弹塑性变形发展的影响,并提出用拉压效应系数来确定轴向塑性累积应变的发展趋势。研究表明:若取轴向压缩方向为正方向,拉压效应系数存在一临界值,当实际值大于临界值时,塑性累积应变向负方向发展,反之则向正方向发展或基本保持不变;同时Hardin模型可以较好地描述饱和粉质黏土的动弹模-动应变关系,且塑性累积应变向负方向发展时动弹模量普遍偏小。 相似文献