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非常规油气开采中实施的储层改造,通常是利用水力压裂技术向储层注入高压流体,改变储层原有的孔缝连通结构,实现油气开采.水力压裂会改变储层应力并使岩石破裂,从而产生微地震事件.微地震研究的重要内容之一是其震源破裂的机制.通过对微地震震源机制的研究,可揭示微地震的产生机理和地下储层的应力变化规律,有效地优化水力压裂和储层改造... 相似文献
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精确确定地震的震源机制解、震源深度和序列的相对位置是地震危险性分析的重要基础.2010年10月24日和2011年3月8日,河南太康地区分别发生MS4.6和MS4.1显著地震,为分析该弱震、少震区的地震危险性,本文利用CAP方法反演了震源机制解和震源深度,并结合深度震相波形记录进一步确认了深度的可靠性.结果显示,两次地震的震源机制解较为接近,均以走滑为主,深度也均为13km左右.此外,以主震作为参考事件,采用主事件法对余震的水平位置进行了相对定位,定位结果显示余震空间上分布的走向分别与主震震源机制解两个节面走向大致相同.本文结果为研究当地地震危险性提供了一定依据. 相似文献
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岩石微破裂震源过程的声发射研究进展 总被引:8,自引:0,他引:8
从岩石微破裂的破裂模式和震源机制、声发现事件波形的振幅频谱特征、介质特征等方面,对地震研究领域岩石微破裂声发射近期的一些研究结果进行了简单综述。 相似文献
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应用2011年1月-2015年4月柯坪块体及周边数字地震台站(38°-42.5°N,75°-80.5°E)记录的3.0 ≤ M ≤ 5.0地震事件,结合柯坪块体介质品质因子和各台站场地响应,计算各地震应力降、地震矩、震源破裂半径、拐角频率等新震源参数,并研究各背景值变化特征及彼此间对应关系。结果表明:柯坪块体地区地震震级与地震矩、矩震级、震源尺度之间表现为较好的正相关性,与地震拐角频率之间呈负相关。地震矩与震源破裂尺度整体呈正相关,但当震源破裂尺度较小时,地震矩变化不大,当震源破裂尺度大于250 m时,地震矩随震源破裂尺度的增大变化较快。由柯坪块体应力降时间分布特征分析可知,研究区具有地震前应力降呈现高值异常、震后缓慢恢复低值的演化过程。 相似文献
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本文利用2007年5月-2010年6月间龙岗火山地震台网记录的火山区46个地震资料,采用Brune(1970)模式,通过几何扩散校正、介质衰减校正、仪器校正等将速度记录谱归算为震源位移谱,使用遗传算法计算拐角频率及零频极限,进而计算震源半径、地震矩等小震震源参数,并系统分析了各种参数之间的关系。研究中使用地震事件的震级为ML1.6~5.0,震源深度为5~10km。结果表明:地震矩范围为10^11~10^15N.m,震源半径为74~658m,地震应力降为0.14~13.1bar。地震矩与近震震级表现出半对数关系,拐角频率与地震矩呈现对数关系,应力降随震级变化不明显。 相似文献
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收集2008年以来海南测震台网记录的M_L 2.5以上地震及爆破资料,利用Brune圆盘模型,计算得出震源参数,发现地震、爆破的震源参数特征为:地震的拐角频率绝大多数大于爆破;地震应力降大于1,爆破应力降小于1;地震震源尺度绝大多数小于爆破。对一个有感疑爆事件,利用其拐角频率、应力降、震源尺度等参数,判定该事件为天然地震,与前人研究结果一致。由此可见,利用震源参数在地震速报、日常分析中判定事件类型具有实际意义。 相似文献
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用Pg波初动求解中小地震的震源参数 总被引:1,自引:0,他引:1
依据震源理论,根据我国数字化地震台网目前的实际情况,在前人研究成果的基础上,提出一种用Pg波初动求中小地震震源参数的实用方法.可以用三个台的Pg波初动(初动峰值和峰值时间),较简便地计算出地震的震源参数, 从而为以震源和介质动态变化为依据的地震预报,提供一个用于日常监测预报的方法. 相似文献
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Yang Zhang Leo Eisner William Barker Michael C. Mueller Kevin L. Smith 《Geophysical Prospecting》2013,61(5):919-930
We develop a methodology to obtain a consistent velocity model from calibration shots or microseismicity observed on a buried array. Using a layered 1D isotropic model derived from checkshots as an initial velocity model, we invert P‐wave arrival times to obtain effective anisotropic parameters with a vertical axis of symmetry (VTI). The nonlinear inversion uses iteration between linearized inversion for anisotropic parameters and origin times or depths, which is specific to microseismic monitoring. We apply this technique to multiple microseismic events from several treatments within a buried array. The joint inversion of selected events shows a largely reduced RMS error indicating that we can obtain robust estimates of anisotropic parameters, however we do not show improved source locations. For joint inversion of multiple microseismic events we obtained Thomsen anisotropic parameters ε of 0.15 and δ of 0.05, which are consistent with values observed in active seismic surveys. These values allow us to locate microseismic events from multiple hydraulic fracture treatments separated across thousands of metres with a single velocity model. As a result, we invert the effective anisotropy for the buried array region and are able to provide a more consistent microseismicity mapping for past and future hydraulic fracture stimulations. 相似文献
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Anisotropy Effects on Microseismic Event Location 总被引:2,自引:0,他引:2
Seismic anisotropy in sedimentary environments is significant—microseismic waveforms often show strong shear-wave splitting,
with differences reaching 40% between horizontally and vertically-polarized shear-wave velocities. Failure to account for
this anisotropy is shown to result in large microseismic event location errors. A method is presented here for determining
the five elastic parameters of a homogeneous, vertical transverse-isotropic (VTI) model from calibration shot data. The method
can also use data from mining-induced seismic events, which are then simultaneously located. This simple model provides a
good fit to arrival times from coal-environment data, and results in dramatic shifts in interpreted event locations. 相似文献
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薄储层的叠前地震响应特征研究,特别是针对具有速度各向异性的含流体薄层,对储层描述具有十分重要的意义.文中基于波动方程数值模拟方法,正演得到各向同性弹性、各向同性衰减、速度各向异性、各向异性衰减模型的地震波场,并对比分析了四种模型的纵波(PP)和转换横波(PS)地震反射特征.研究结果表明:在衰减介质背景下,引入各向异性,PP和PS波的反射波振幅较弹性介质均减弱,且衰减因素对薄层振幅的影响强于各向异性.同时,VTI各向异性衰减在单频PS振幅曲线上表现出强差异性,而HTI各向异性衰减则会影响PP和PS波单频振幅曲线的极值点幅值和位置,通过分析单频振幅曲线的极值点振幅和极值点位置对各向异性衰减薄层预测有指导作用,尤其对平时较难分辨的VTI各向异性衰减薄层,单频分析方法的优势更明显. 相似文献
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由于地面微地震监测台站布设在地表,会受到地表起伏、低降速带厚度和速度变化的影响,降低了微地震事件的识别准确度和定位精度,限制了地面微地震监测技术在复杂地表地区的应用.因此,将三维地震勘探技术的思路引入到地面微地震监测中,提出了三维地震与地面微地震联合校正方法,将油气勘探和开发技术更加紧密地结合在一起.根据三维地震数据和低降速带测量数据,通过约束层析反演方法建立精确的近地表速度模型,将地面微地震台站从起伏地表校正到高速层中的平滑基准面上,有效消除复杂近地表的影响.其次,根据射孔数据和声波测井速度信息,通过非线性反演方法建立最优速度模型,由于已经消除复杂近地表的影响,在进行速度模型优化时不需要考虑近地表的影响,因而建立的速度模型更加准确.最后,在精确速度模型的基础上,通过互相关方法求取剩余静校正量,进一步消除了复杂近地表和速度模型近似误差的影响.三维地震与地面微地震联合校正方法采用逐步校正的思路,能够有效消除复杂近地表的影响,提高微地震数据的品质和速度模型的精确度,保证了微地震事件的定位精度,具有良好的应用前景. 相似文献
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Research Note: Sparsity‐Aware Multiple Microseismic Event Localization Blind to the Source Time‐Function 下载免费PDF全文
Zijian Tang Xander Campman Alexander Droujinine Geert Leus 《Geophysical Prospecting》2015,63(1):70-77
We consider the problem of simultaneously estimating three parameters of multiple microseimic events, i.e., the hypocenter, moment tensor, and origin time. This problem is of great interest because its solution could provide a better understanding of reservoir behavior and can help to optimize the hydraulic fracturing process. The existing approaches employing spatial source sparsity have advantages over traditional full‐wave inversion‐based schemes; however, their validity and accuracy depend on the knowledge of the source time‐function, which is lacking in practical applications. This becomes even more challenging when multiple microseimic sources appear simultaneously. To cope with this shortcoming, we propose to approach the problem from a frequency‐domain perspective and develop a novel sparsity‐aware framework that is blind to the source time‐function. Through our simulation results with synthetic data, we illustrate that our proposed approach can handle multiple microseismic sources and can estimate their hypocenters with an acceptable accuracy. The results also show that our approach can estimate the normalized amplitude of the moment tensors as a by‐product, which can provide worthwhile information about the nature of the sources. 相似文献
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《中国科学:地球科学(英文版)》2021,(3)
Reservoir reconstructions implemented in unconventional oil and gas exploration usually adopt hydraulic fracturing techniques to inject high-pressure fluid into the reservoir and change its pore-fracture connection structure to enhance production. Hydraulic fracturing changes the reservoir stress and causes the rocks to crack, thus generating microseismic events.One important component of microseismic research is the source mechanism inversion. Through the research on the microseismic focal mechanism, information on the source mechanisms and in-situ stress status variations can be quantitatively revealed to effectively optimize the reservoir reconstruction design for increasing production. This paper reviews the recent progress in hydraulic fracturing induced microseismic focal mechanism research. We summarize their main principles and provide a detailed introduction of the research advances in source modeling, microseismic data synthesis, and focal mechanism inversion. We also discuss the challenges and limitations in the current microseismic focal mechanism research and propose prospects for future research ideas and directions. 相似文献
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近年来,海洋可控源电磁法(MCSEM)被引入油气勘探领域以降低勘探风险.在海洋环境中,受沉积因素所造成的电阻率各向异性的影响,地电模型往往会非常复杂.为更好地反映地下电性结构,本文实现了基于VTI各向异性介质的频率域海洋可控源电磁三维反演.其中,正演采用基于Yee氏交错网格的三维有限差分算法,所形成的离散线性系统通过大规模并行矩阵直接求解器(MUMPS)进行求解.反演采用基于不等式约束的有限内存BFGS(L-BFGS)算法.最后,利用VTI各向异性介质合成数据,分别进行了电阻率各向异性覆盖层和电阻率各向异性高阻层的三维反演,结果表明:(1)基于并行直接法的MCSEM非常适用于海洋电磁所特有的多场源问题;(2)针对各向异性覆盖层模型进行三维各向异性约束反演,提高了解的可靠性;(3)针对电阻率各向异性高阻层,Inline和broadside数据覆盖的反演结果对异常体位置有很好的反映. 相似文献
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A challenge in microseismic monitoring is quantification of survey acquisition and processing errors, and how these errors jointly affect estimated locations. Quantifying acquisition and processing errors and uncertainty has multiple benefits, such as more accurate and precise estimation of locations, anisotropy, moment tensor inversion and, potentially, allowing for detection of 4D reservoir changes. Here, we quantify uncertainty due to acquisition, receiver orientation error, and hodogram analysis. Additionally, we illustrate the effects of signal to noise ratio variances upon event detection. We apply processing steps to a downhole microseismic dataset from Pouce Coupe, Alberta, Canada. We use a probabilistic location approach to identify the optimal bottom well location based upon known source locations. Probability density functions are utilized to quantify uncertainty and propagate it through processing, including in source location inversion to describe the three-dimensional event location likelihood. Event locations are calculated and an amplitude stacking approach is used to reduce the error associated with first break picking and the minimization with modelled travel times. Changes in the early processing steps have allowed for understanding of location uncertainty of the mapped microseismic events. 相似文献
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微地震监测被广泛应用于非常规油气资源的水力压裂作业、油藏描绘和水驱前缘监测工程中.微地震定位采用的初始速度模型一般是基于地震测井记录和射孔数据建立,该速度模型的不准确性易引起定位误差.为降低这种定位误差,本文发展了一种微地震定位和各向异性速度结构同时反演的方法.研究对象为1-D的层状TI介质,其中对称轴方向任意.利用改进的分区多步最短路径算法计算qP、qSV和qSH波的到达时间和射线路径,结合共轭梯度法求解带约束的阻尼最小二乘问题.数值模拟结果表明,该算法能同时进行各向异性速度结构模型(每层的Thomsen参数和界面深度)和微震震源参数(空间坐标和发震时刻)的反演,并且对随机噪声不敏感,有利于实际工程应用. 相似文献