本文選題：凍土帶天然氣水合物 + 廣義混合率　； 參考：《中國科學(xué)技術(shù)大學(xué)》2017年博士論文

【摘要】：天然氣水合物是可持續(xù)發(fā)展的清潔能源,然而受開采技術(shù)等制約,全球水合物開發(fā)基本處于室內(nèi)試驗(yàn)和室外資源普查、試采階段。相比海域天然氣水合物,陸域水合物的勘探開發(fā)似乎更容易,然而目前世界上僅麥索雅哈氣田是唯一實(shí)現(xiàn)工業(yè)性開采的陸域水合物藏。作為世界第三大凍土國,我國的陸域天然氣水合物資源前景廣闊,但是由于起步晚,對陸域凍土帶天然氣水合物的成藏模式及其勘探技術(shù)均研究薄弱,至今僅青藏高原北部木里地區(qū)鉆獲水合物樣品。本文從復(fù)雜多相介質(zhì)聲學(xué)、電學(xué)性質(zhì)巖石物理模型出發(fā),建立起適合凍土區(qū)巖石物性的水合物模型。然后通過數(shù)值模擬,研究凍土帶天然氣水合物的地震學(xué)響應(yīng)和電磁響應(yīng),探索我國凍土帶天然氣水合物成藏模式及綜合地球物理勘探標(biāo)志。巖石物性是地球物理勘探的基礎(chǔ)。已有的天然氣水合物巖石物理模型適用于高孔隙度的海域沉積層,且多考慮為球狀孔隙。本文針對我國凍土帶沉積層孔隙度低的特點(diǎn),利用廣義混合率模型研究任意孔隙形狀的多相介質(zhì)聲學(xué)、電學(xué)性質(zhì),獲得了廣義混合率模型參數(shù)的變化規(guī)律及其與微觀結(jié)構(gòu)的關(guān)系,與廣泛應(yīng)用的差分有效介質(zhì)(DEM)模型和自洽(SC)模型比較,具有更好的普適性,其結(jié)果獲得大量實(shí)驗(yàn)數(shù)據(jù)的驗(yàn)證。相對于在測井上應(yīng)用廣泛的Archie公式,廣義混合率可以解決Archie公式參數(shù)多、僅限一項(xiàng)介質(zhì)導(dǎo)電、且僅適用于導(dǎo)電流體包圍固體顆粒(Water-wet grains)結(jié)構(gòu),而不適合弱導(dǎo)電流體包圍固體顆粒(Oil-Wet grains)等問題,第一次給出了關(guān)于弱導(dǎo)電流體包圍固體顆粒類型的廣義混合率參數(shù)表達(dá)式,并通過對已有的幾種水合物導(dǎo)電模型進(jìn)行數(shù)值模擬,結(jié)合水合物電導(dǎo)率實(shí)驗(yàn)數(shù)據(jù)表明,水合物導(dǎo)電機(jī)制為導(dǎo)電流體包圍在固體顆粒表面,推測水合物賦存模式為非固結(jié)型。含天然氣水合物儲層表現(xiàn)為高聲波速度和高電阻率特點(diǎn),這是陸域天然氣水合物勘探識別的基礎(chǔ)。本文根據(jù)已有地質(zhì)、地球物理資料和巖石物理模型,建立了陸域天然氣水合物模型,并通過數(shù)值模擬研究其地震學(xué)、電磁學(xué)響應(yīng)特征。彈性波振幅隨偏移距變化(AVO)正演模擬結(jié)果表明,含天然氣水合物儲層在近偏移距處的P波一次反射震相以及垂直地震剖面數(shù)據(jù)中直達(dá)P波震相的振幅均較弱,這種AVO弱振幅特點(diǎn)為陸域水合物地震響應(yīng)特征。電磁法在低阻金屬礦勘探中取得明顯效果,由于陸域天然氣水合物為高阻體,可控源電磁(CSEM)法目前尚未取得好的勘探效果。本文第一次將海洋CSEM的方法原理應(yīng)用于陸域天然氣水合物勘探中,數(shù)值模擬結(jié)果表明,其電場的振幅隨偏移距變化(MVO)在儲層位置獲得更大的振幅。因此,地震AVO相對弱振幅與可控源電磁MVO的強(qiáng)振幅結(jié)合,有可能構(gòu)成陸域凍土帶天然氣水合物綜合地球物理勘探的指示特征。直流電阻率法一般很少應(yīng)用于凍土帶地區(qū)的地質(zhì)勘探,因?yàn)殡娏麟y于穿透高阻的覆蓋區(qū)。我們對線電極源使用電流密度分配公式CDA(Current DensityAllocation),發(fā)展了基于CDA的任意長電極直流電阻率三維非結(jié)構(gòu)有限元數(shù)值模擬,并在此基礎(chǔ)上,借鑒已有線電極模型處理測量電極的方法,使用線電極代替圓柱體電極,形成了基于CDA方法的線電極供電、線電極接收的長電極三維電阻率模擬方法。本文將該方法應(yīng)用于陸域凍土帶天然氣水合物勘探中,結(jié)果表明,長電極在穿過水合物儲層上方,具有明顯的高阻異常。本文研究了裂隙對陸域水合物勘探中地震波速度的影響。結(jié)合巖石物理模型,實(shí)驗(yàn)數(shù)據(jù)以及測井響應(yīng),計算了沿測井縱向剖面的裂隙密度,結(jié)果表明陸域水合物的賦存狀態(tài)與裂隙密切相關(guān)。地震波在裂隙介質(zhì)中傳播的數(shù)值模擬表明,當(dāng)裂隙中流體(氣體或液體:)不連通時,地震波速度基本與頻率無關(guān),而受裂隙形狀影響較大。而當(dāng)裂隙中流體處于連通狀態(tài)時,地震波速度基本不受裂隙形狀影響,而與頻率有關(guān)。裂隙中流體通過裂隙相互連通的類型,其地震波速度與頻率的響應(yīng)為:高頻低速、低頻高速。裂隙中流體通過滲透性良好的孔隙骨架連通時,則表現(xiàn)為:低頻低速,高頻高速。根據(jù)凍土帶特點(diǎn),建立了水合物儲藏的裂隙模型,研究其地震剖面的AVO和頻率特點(diǎn),并與實(shí)際地震勘探響應(yīng)對比,結(jié)果表明流體通過裂隙相互流通的裂隙模型符合凍土帶天然氣水合物的儲藏特點(diǎn),可為凍土帶天然氣水合物成藏機(jī)制提供一些新的認(rèn)識。
[Abstract]:Natural gas hydrate is a clean energy for sustainable development. However, under the restriction of mining technology, the development of global hydrate is basically in the laboratory test and the survey of outdoor resources and trial production. Compared with the marine natural gas hydrate, the exploration and development of land hydrate seems to be easier than that of marine natural gas hydrate, but at present, only the maajakaha gas field in the world is the only one. As the third largest permafrost in the world, the land area natural gas hydrate resources in China are very promising. However, because of the late start, the reservoir formation model and exploration technology of the natural gas hydrate in the continental permafrost zone are all weak. The complex multi-phase medium acoustics and electrical properties of rock physics model set up the hydrate model suitable for the rock physical property of the frozen soil area. Then through numerical simulation, the seismological response and electromagnetic response of natural gas hydrate in the permafrost zone are studied, and the reservoir model and comprehensive geophysical prospecting mark of the natural gas hydrate in the permafrost zone are explored. Rock physical property is the basis of geophysical exploration. The existing petrophysical model of gas hydrate is suitable for high porosity marine sediments and more considered spherical pores. In this paper, in view of the characteristics of low porosity in the deposited layer of the permafrost zone in China, the multiphase medium acoustics with arbitrary pore shape are studied by the generalized mixing rate model and the electrical properties are studied. The variation of the parameters of the generalized mixture rate model and its relationship with the microstructure are obtained. Compared with the widely used DEM model and the self consistent (SC) model, the generalized mixture rate model has a better universality and the result is verified by a large number of experimental data. The generalized mixing rate can be solved compared with the widely used Archie formula in the log. The Archie formula has many parameters, only one medium is conductive, and it is only suitable for conducting fluid to encircling solid particles (Water-wet grains) structure, but not suitable for the weak conducting fluid to encircling solid particles (Oil-Wet grains). Several existing models of hydrate conduction are simulated, and the experimental data of the conductivity of hydrates show that the gas hydrate conducting mechanism is surrounded by solid particles on the surface of the solid particles, and it is speculated that the mode of hydrate accumulation is non consolidation. The gas hydrate reservoir containing natural gas is characterized by high acoustic wave velocity and high resistivity, which is the natural gas of land domain. Based on the existing geological, geophysical data and rock physical models, a land domain natural gas hydrate model has been established in this paper, and its seismological and electromagnetics response characteristics are studied by numerical simulation. The results of the elastic wave amplitude with the offset variation (AVO) show that the gas hydrate reservoir is near the bias. The amplitude of the direct P wave phase in the P wave and vertical seismic profiles at the distance is weak, and the weak amplitude of the AVO is characterized by the seismic response of the land domain hydrate. The electromagnetic method has achieved obvious effect in the exploration of low resistivity metals, because the land domain gas hydrate is a high resistivity body, and the controllable source electromagnetic (CSEM) method has not yet been found. For the first time, the method principle of marine CSEM is applied to the exploration of natural gas hydrate in the land domain. The numerical simulation results show that the amplitude of the electric field increases with the shift distance (MVO) in the reservoir position. Therefore, the relative weak amplitude of the earthquake AVO is combined with the strong amplitude of the controllable source electromagnetic MVO, and it may be constructed. The direct-current resistivity method is generally rarely applied to geological exploration in the permafrost zone, because the current is difficult to penetrate the high resistance coverage area. We use the current density distribution formula CDA (Current DensityAllocation) for the line electrode source to develop the CDA based arbitrarily. On the basis of the three-dimensional non structural finite element numerical simulation of the long electrode DC resistivity, and on this basis, using the wire electrode model to deal with the measuring electrode, using the wire electrode instead of the cylinder electrode, the three dimensional resistivity simulation method for the line electrode received by the wire electrode based on the CDA method is formed. This method is applied to this method in this paper. In the exploration of natural gas hydrate in the continental permafrost zone, the results show that the long electrode has obvious high resistivity anomalies over the hydrate reservoir. The effect of the crack on the seismic wave velocity in the exploration of land hydrate is studied. The results show that the occurrence of the marine gas hydrate is closely related to the fissure. The numerical simulation of the seismic wave propagation in the fractured medium shows that when the fluid (gas or liquid) is not connected in the fissure, the velocity of the seismic wave is irrelevant to the frequency, but is greatly influenced by the shape of the fissure. It is not affected by the shape of the fissure, but it is related to the frequency. The response of the fluid through the crack interconnected in the crack is the response of the velocity and frequency of the seismic wave: high frequency and low frequency, low frequency and high speed. When the fluid through the porous skeleton is connected by the good permeability in the fissure, the fluid is characterized by low frequency, low speed, high frequency and high speed. According to the characteristics of the permafrost zone, the hydration is established. The AVO and frequency characteristics of the seismic profile are studied and compared with the actual seismic response. The results show that the fissure model flowing through the fissure conforms to the storage characteristics of the natural gas hydrate in the permafrost zone, and can provide some new understanding for the gas hydrate formation mechanism of the permafrost zone.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：P618.13

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