【摘要】：致密氣、煤層氣和頁(yè)巖氣等非常規(guī)油氣資源在日益增長(zhǎng)的低碳燃料供應(yīng)方面起著越來(lái)越重要的作用。這主要得益于水平井鉆井和水力壓裂技術(shù)在低滲透性儲(chǔ)層中的發(fā)展應(yīng)用。水力壓裂誘發(fā)的微地震能夠幫助我們了解水壓致裂的裂縫幾何分布狀況,估計(jì)經(jīng)過(guò)壓裂改造的巖石的體積。通過(guò)對(duì)非常規(guī)油氣開(kāi)采中誘發(fā)的微地震進(jìn)行定位和震源機(jī)制研究,我們不僅能夠刻畫(huà)水壓致裂的破裂過(guò)程,而且可以對(duì)鉆井孔周邊區(qū)域的斷裂分布情況進(jìn)行描述,這為我們構(gòu)建斷裂儲(chǔ)層模型提供了非常重要的先驗(yàn)信息和約束。 目前,人們常用P波初動(dòng)極性法、振幅比法和波形矩張量反演方法進(jìn)行地震的震源機(jī)制研究工作。由于微地震震級(jí)小,破裂釋放的能量有限,僅有少數(shù)臺(tái)站能夠記錄到震動(dòng)信息,利用常規(guī)的P波初動(dòng)極性和振幅比方法不能準(zhǔn)確得到微小事件的震源機(jī)制解。所以本文使用了矩張量反演方法,其主要基于全波形匹配的思想,利用理論地震圖和實(shí)際地震記錄的最佳匹配擬合反演來(lái)確定震源機(jī)制解。全波形匹配方法的目標(biāo)函數(shù)中不僅包含波形的振幅和相位信息,而且加入了P波初動(dòng)和縱橫波振幅比信息,既充分利用了波形信息,也可以對(duì)反演加以約束,避免僅靠部分波形數(shù)據(jù)反演導(dǎo)致的不確定性。 首先,為了驗(yàn)證波形匹配方法的穩(wěn)健性,我們使用不同地區(qū)的速度模型和震源參數(shù)進(jìn)行了合成數(shù)據(jù)測(cè)試。兩類模型測(cè)試結(jié)果都表明此波形匹配方法穩(wěn)定可靠,可用于解決微地震的震源參數(shù)確定問(wèn)題。然后,我們將波形匹配方法應(yīng)用于美國(guó)猶他州中西部的Cove Fort-Sulphurdale地?zé)豳Y源富集區(qū)。震源機(jī)制反演結(jié)果顯示,所選取地震的斷層面解的走向大部分趨于南北向,與區(qū)域應(yīng)力圖顯示的最大水平主應(yīng)力優(yōu)勢(shì)取向—南北方向,具有較好的一致性。前人研究結(jié)果表明該地區(qū)處于近東西向的拉張應(yīng)力作用下,南北方向應(yīng)該是主壓應(yīng)力的優(yōu)勢(shì)取向,與基于震源機(jī)制的應(yīng)力分析得到結(jié)果比較一致,符合目前人們對(duì)該地區(qū)的構(gòu)造認(rèn)知。為了更清楚地了解Cove Fort-Sulphurdale地?zé)釁^(qū)的斷裂構(gòu)造特征,我們也對(duì)該區(qū)域進(jìn)行了各向異性研究。橫波分裂分析結(jié)果說(shuō)明各向異性主要存在于淺部區(qū)域；各臺(tái)站快波的極化方向指向南北向,說(shuō)明如果各向異性主要是由該地區(qū)的斷裂構(gòu)造引起,那么該地區(qū)的主要斷層或裂縫的方向應(yīng)該是南北向。 最后,鑒于文章討論的震源機(jī)制反演主要是基于雙力偶點(diǎn)源假設(shè),它雖然簡(jiǎn)化了問(wèn)題,減小了介質(zhì)各向異性等不均勻性存在時(shí)反演的不確定性。然而,它得到的解并不完整,不包含體積變化和補(bǔ)償線性向量偶極(CLVD)成分。對(duì)非雙力偶成分的認(rèn)知,特別是體變成分,對(duì)理解破裂過(guò)程、評(píng)價(jià)壓裂工作效率非常重要。為此,我們將斷層面解反演拓展為基于波形匹配的全矩張量反演,以確保震源機(jī)制反演結(jié)果的準(zhǔn)確性�？紤]到精度和準(zhǔn)確性,矩張量參數(shù)的搜索間隔較小,網(wǎng)格搜索效率較低。為此,我們使用差分進(jìn)化算法進(jìn)行改進(jìn),加速反演過(guò)程。合成數(shù)據(jù)測(cè)試結(jié)果表明,與斷層面反演相比,經(jīng)過(guò)DE改進(jìn)的矩張量反演也能夠準(zhǔn)確得到震源機(jī)制解信息,計(jì)算效率與網(wǎng)格搜索相比提高了幾十倍。
[Abstract]:The unconventional oil and gas resources such as tight gas, coal bed gas and shale gas are playing an increasingly important role in the growing supply of low carbon fuel. This is mainly due to the development and application of horizontal well drilling and hydraulic fracturing in low permeability reservoirs. The micro earthquake induced by hydraulic fracturing can help us to understand the cracks in water pressure. We can not only describe the fracture process of hydraulic fracturing, but also describe the distribution of fracture in the surrounding area of the drilling hole, which provides us with the construction of fractured reservoir. The model provides very important prior information and constraints.
At present, P wave initial dynamic polarity method, amplitude ratio method and wave moment tensor inversion method are used to study the source mechanism of earthquake. Due to the small magnitude of the microseismic, the energy of the fracture release is limited, only a few stations can record the vibration information, and the small events can not be obtained by the conventional P wave initial motion polarity and amplitude ratio method. Therefore, this paper uses the moment tensor inversion method, which is mainly based on the idea of full waveform matching, and uses the optimal matching inversion of the theoretical seismogram and the actual seismic record to determine the source mechanism solution. The objective function of the full waveform matching method not only contains the amplitude and phase information of the wave shape, but also adds the P wave. The information of the amplitude ratio of the initial and the longitudinal and transverse waves can not only make full use of the information of the waveform, but also restrain the inversion to avoid the uncertainty caused by the inversion of the partial waveform data.
First, in order to verify the robustness of the waveform matching method, we use the velocity model and the source parameters in different regions to test the synthetic data. The two model test results show that the waveform matching method is stable and reliable, and can be used to solve the problem of the source parameters of microseismic. Then, we apply the waveform matching method to the United States. The Cove Fort-Sulphurdale geothermal resource enrichment area in central and Western Utah state. The result of seismic source mechanism inversion shows that the direction of the fault surface solution of the selected earthquake tends to North and south, and has good consistency with the north and south direction of the maximum horizontal principal stress orientation in the region. The results of previous studies show that the region is located in the region. Under the near East-West tensile stress, the north-south direction should be the dominant orientation of the main pressure stress, which is consistent with the stress analysis based on the source mechanism, which conforms to the current tectonic cognition of the region. In order to know more clearly the characteristics of the fracture structure of the Cove Fort-Sulphurdale geothermal area, we also carry out the region. The results of the shear wave splitting analysis show that the anisotropy mainly exists in the shallow region; the polarization direction of the fast waves at each station points to the north-south direction, indicating that if the anisotropy is mainly caused by the fracture structure in this area, the direction of the main faults or cracks in this area should be north-south.
In the end, the source mechanism inversion is mainly based on the double couple point source hypothesis, which simplifies the problem and reduces the uncertainty of the inversion when the anisotropy of the medium exists. However, the solution is not complete, and does not contain the volume change and compensatory linear vector dipole (CLVD) component. The cognition, especially the body variable component, is very important for understanding the fracture process and evaluating the efficiency of the fracturing work. Therefore, we extend the inversion of the fault surface to the full moment tensor inversion based on the waveform matching to ensure the accuracy of the inversion results of the source mechanism. Therefore, we use the differential evolution algorithm to improve and accelerate the inversion process. The results of synthetic data test show that, compared with the broken layer inversion, the DE improved moment tensor inversion can also get the exact information of the source mechanism solution, and the calculation efficiency is a few times higher than the grid search.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P315.6

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