结合地震学和地质力学对微地震数据的研究

发布时间：2018-04-26 09:33

本文选题：微地震 + 定位　；参考：《中国科学技术大学》2015年博士论文

【摘要】：近年来多阶段注水压裂已经被广泛的应用在致密油气的开采中。在注水压裂中诱发的微地震可以显著的帮助提高致密岩石的渗透率,从而提高了非常规油气的产能。微地震监测技术,因为其可以给注水过程提供重要的信息,已经被应用在实际的工区中。目前来说,微地震技术监测的主要结果包括对微地震事件的定位和对其震源机制解的反演两大方面。在本文,我们把地震学中的原理和方法应用到微地震数据的研究中,并对微地震的震源反演结果进行了地质力学角度的分析。我们的研究主要体现在以下几个方面：1.对微地震事件定位不确定性的讨论首先我们讨论了微地震中常用的两大类定位方法,即基于走时拾取的定位方法和基于偏移叠加的定位方法。在分析了这两种常用方法的优缺点以后,我们探讨了只利用S波定位的可能性。模拟实验的结果显示,在微地震事件与检波器距离较近时,如果P波拾取困难,可以只采用S波的信息进行定位。另外,由于速度模型的不准确性是造成微地震事件定位不确定性的最主要原因,我们又探讨了联合反演速度和位置的可能性。在使用三个微地震事件的情况下,联合反演抗噪音能力不强。但是可以推测,如果使用上百个事件的信息,则可以较好的同时约束速度和微地震事件的位置。2.震源机制解的反演我们对基于两口井观测的微地震数据进行了震源机制解的反演,模拟实验表明,我们发展的基于两口井的反演方法可以有效的反演微地震震源参数。然后我们对美国德克萨斯州某工区的微地震数据进行了震源机制解的反演。在论文最后一章,我们使用地震搜索引擎的办法对新疆某地区进行了震源机制解的反演。结果显示,使用地震搜索引擎可以在接受到地震波形以后的1秒之内快速的给出震源参数的信息。这对建立地震早期预警系统意义重大。3.结合地质力学分析微地震的震源机制解我们引入了地质力学的方法和原理对反演出的微地震震源机制解进行研究。首先我们应用微地震震源断层面解反演了地下的应力场信息,然后我们利用摩尔库伦滑动破裂准则选取了微地震事件的实际破裂断层面,最后我们估计了微地震事件处的孔隙压力的扰动分布。结果显示,在注入的高压液体作用下,地下的孔隙压力随着离注水口的距离的增大而减小。
[Abstract]:In recent years, multi-stage water injection fracturing has been widely used in the production of dense oil and gas. The microearthquakes induced by water injection fracturing can significantly improve the permeability of tight rocks and thus improve the productivity of unconventional oil and gas. Microseismic monitoring technology, because it can provide important information for water injection process, has been applied in practical areas. At present, the main results of microseismic monitoring include the localization of microseismic events and inversion of the focal mechanism solutions. In this paper, the principles and methods of seismology are applied to the study of microseismic data, and the source inversion results of microearthquakes are analyzed from the perspective of geomechanics. Our research is mainly reflected in the following aspects: 1. In this paper, we discuss the uncertainty of microseismic event location. Firstly, we discuss two kinds of localization methods, that is, the location method based on walking time pickup and the location method based on migration stacking. After analyzing the advantages and disadvantages of these two common methods, we discuss the possibility of using S wave localization only. The simulation results show that when the distance between the microseismic event and the geophone is close, if the P wave is difficult to pick up, the information of S wave can be used for localization only. In addition, because the inaccuracy of velocity model is the main reason for the uncertainty of microseismic event location, we also discuss the possibility of joint inversion velocity and location. In the case of three microseismic events, the joint inversion is not robust to noise. But it can be speculated that if we use the information of hundreds of events, we can better constrain both the velocity and the location of the microseismic events. Inversion of the focal mechanism solution we have done the inversion of the focal mechanism solution of the microseismic data based on the observation of two wells. The simulation results show that the inversion method based on the two wells can effectively invert the microseismic focal parameters. Then we invert the focal mechanism solution of the microseismic data in a Texas area, USA. In the last chapter, we use seismic search engine to retrieve the focal mechanism solution in a region of Xinjiang. The results show that the seismic search engine can quickly give the source parameter information within 1 second after receiving the seismic waveform. This is of great significance to the establishment of earthquake early warning system. Combined with geomechanical analysis of focal mechanism solutions of microearthquakes, we introduce the method and principle of geomechanics to study the focal mechanism solutions of microearthquakes. First, we use the source fault plane solution of the micro-earthquake to retrieve the underground stress field information, and then we use the Moore Coulomb sliding fracture criterion to select the actual rupture fault plane of the micro-earthquake event. Finally, we estimate the perturbed distribution of pore pressure at microseismic events. The results show that the pore pressure decreases with the increase of the distance from the injection nozzle under the action of the injected high pressure liquid.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE357.6;P631.4

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