【摘要】：近年來,隨著常規(guī)能源的日益枯竭和碳排放的增加,頁巖氣等非常規(guī)能源的開發(fā)成為世界能源研究的焦點之一。目前對于儲層變形與氣體運移機制的研究尚不成熟,這極大地限制了頁巖氣開采技術(shù)的發(fā)展。本文基于多孔彈性力學(xué)和滲流力學(xué)等理論,建立了頁巖三重孔隙結(jié)構(gòu)下包含頁巖變形、干酪根基質(zhì)分子解吸與擴散、無機質(zhì)系統(tǒng)粘性流、以及裂隙系統(tǒng)粘性流的多物理場耦合模型。此外,建立了多孔吸附介質(zhì)的有效應(yīng)力準(zhǔn)則。主要取得以下研究成果。(1)提出多孔含裂隙頁巖儲層的三重孔隙力學(xué)模型。根據(jù)氣體在頁巖中的運移及吸附儲存特征,建立了頁巖儲層的三重孔隙度數(shù)學(xué)模型以及各自系統(tǒng)的擴散和滲透率數(shù)學(xué)模型,并建立了三重孔隙結(jié)構(gòu)下有效應(yīng)力及吸附膨脹引起的變形控制方程、干酪根基質(zhì)系統(tǒng)的氣體擴散控制方程、無機質(zhì)系統(tǒng)以及裂隙系統(tǒng)的流動控制方程�？刂品匠讨邪隧搸r變形、氣體滲流、氣體吸附等多物理場耦合作用。(2)揭示了由于三重介質(zhì)導(dǎo)流能力的差異而引起的壓力場演化不同步現(xiàn)象:裂隙快于無機質(zhì),并快于干酪根。研究結(jié)果表明產(chǎn)氣過程中氣體的交換類型屬于干酪根-無機質(zhì)-裂隙的“串聯(lián)”流動模式:氣體由濃度高(壓力較大)的有機孔向無機質(zhì)系統(tǒng)擴散,再由無機質(zhì)系統(tǒng)向裂隙系統(tǒng)(壓力較小)流動;但當(dāng)干酪根基質(zhì)的擴散系數(shù)相對較大時,其壓力演化幾乎與無機質(zhì)同步,且均慢于裂隙系統(tǒng)的壓力演化,此時氣體的交換類型服從“并聯(lián)”模式:裂隙系統(tǒng)中的氣體同時來源于干酪根和無機質(zhì)系統(tǒng)。(3)通過與現(xiàn)場水平井產(chǎn)氣率的匹配,驗證了該模型的數(shù)值模擬結(jié)果。敏感性分析結(jié)果表明,裂隙滲透率對初始產(chǎn)氣率的影響至關(guān)重要,而干酪根基質(zhì)的TOC含量和擴散系數(shù)是保證頁巖氣持續(xù)高效開采的重要參數(shù)。(4)通過引入吸附膨脹模量的概念,建立了考慮吸附膨脹效應(yīng)下多孔吸附介質(zhì)的有效應(yīng)力準(zhǔn)則,將多孔吸附介質(zhì)的非線性變形問題簡化成無孔非吸附介質(zhì)的線彈性變形問題,并通過煤體的無約束實驗和單軸應(yīng)變實驗證明了有效應(yīng)力系數(shù)的統(tǒng)一性。(5)吸附膨脹模量是衡量多孔吸附介質(zhì)吸附變形難易程度的指標(biāo)。吸附膨脹模量越小,相同孔壓情況下的吸附膨脹越明顯。實驗證明低孔壓條件下(7 MPa),煤體對甲烷或二氧化碳的吸附膨脹模量比固體顆粒體積模量小一個數(shù)量級,這側(cè)面反映了低孔壓儲層產(chǎn)氣過程中的吸附效應(yīng)對變形或滲透率的影響占主導(dǎo)地位。
[Abstract]:In recent years, with the depletion of conventional energy and the increase of carbon emissions, the development of unconventional energy such as shale gas has become one of the focuses of energy research in the world. At present, the study of reservoir deformation and gas migration mechanism is still immature, which greatly limits the development of shale gas production technology. Based on the theory of porous elasticity and percolation mechanics, this paper has established shale deformation, molecular desorption and diffusion of kerogen matrix, viscous flow in inorganic system under shale triple pore structure. And the multi-physical field coupling model of viscous flow in fracture system. In addition, the effective stress criterion for porous adsorption media is established. The main achievements are as follows: (1) the triple pore mechanics model of porous fractured shale reservoir is proposed. According to the characteristics of gas migration and adsorption and storage in shale, the mathematical model of shale reservoir's triple porosity and the mathematical model of diffusion and permeability of their respective systems are established. The governing equations of effective stress and adsorption expansion under triple pore structure, gas diffusion control equation of kerogen matrix system, flow control equation of inorganic system and fracture system are established. The governing equation includes the coupling of shale deformation, gas percolation and gas adsorption. (2) it is revealed that the evolution of the pressure field is out of sync due to the difference in the conductivity of the triplet medium: the fracture is faster than the inorganic mass. And faster than kerogen. The results show that the type of gas exchange in the process of gas production belongs to the "series" flow pattern of kerogen, inorganic substance and fissure: the gas diffuses from organic pores with high concentration (high pressure) to inorganic system. However, when the diffusion coefficient of cheese is relatively large, the pressure evolution is almost synchronized with inorganic matter, and both of them are slower than the pressure evolution of fracture system. At this time, the gas exchange type follows the "parallel" model: the gas in the fracture system comes from both kerogen and inorganic system. (3) the numerical simulation results of the model are verified by matching the gas production rate of the field horizontal well. The sensitivity analysis results show that the influence of fracture permeability on the initial gas production rate is very important, and the TOC content and diffusion coefficient of the kerogen are important parameters to ensure the shale gas sustainable and efficient production. (4) the concept of adsorption modulus of expansion is introduced. In this paper, the effective stress criterion of porous adsorption medium considering the effect of adsorption and expansion is established, and the nonlinear deformation problem of porous adsorption medium is simplified as the linear elastic deformation problem of porous non-adsorbed medium. The unity of effective stress coefficient is proved by unconstrained and uniaxial strain tests. (5) the adsorption modulus of expansion is an index to measure the difficulty of adsorption deformation in porous adsorption medium. The smaller the modulus of adsorption expansion is, the more obvious the adsorption expansion is at the same pore pressure. The experimental results show that at low pore pressure (7 MPA), the adsorption modulus of expansion of methane or carbon dioxide on coal is one order of magnitude smaller than that of solid particles. This side reflects the dominant effect of adsorption on deformation or permeability during gas production in low pore pressure reservoirs.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TE31

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