【摘要】：天然氣水合物作為一種儲(chǔ)量豐富、能量密度高、燃燒清潔的潛在能源被越來越多的國家所關(guān)注，目前世界上有許多國家都已經(jīng)展開對天然氣水合物的研究，其中包括天然氣水合物開采技術(shù)的研究以及水合物應(yīng)用技術(shù)的研究等，并且已經(jīng)取得了巨大的進(jìn)展。 天然氣水合物在自然界中主要儲(chǔ)藏在海底沉積層及永久凍土帶，復(fù)雜的地質(zhì)環(huán)境給水合物的開采造成了嚴(yán)重的困難。水合物的開采是一個(gè)復(fù)雜的過程，影響因素眾多，且分解過程中氣、水兩相流動(dòng)會(huì)極大的影響水合物的分解過程，本文通過數(shù)值模擬方法，研究了天然氣水合物在多孔介質(zhì)中的分解過程，以滲流力學(xué)理論和孔隙網(wǎng)絡(luò)模型為基礎(chǔ)，從微觀層次出發(fā)，得出以下研究結(jié)論： 建立了三維立方體孔隙網(wǎng)絡(luò)模型，研究了水合物飽和度、孔徑分布對水合物相平衡的影響，采用達(dá)西定律作為研究的理論基礎(chǔ)，模擬了多孔介質(zhì)中水合物生成位置不同時(shí)導(dǎo)致的滲透率變化，研究結(jié)果表明，無論水合物是生成于中心還是生成于壁面，滲透率都隨水合物飽和度的增加而減小，并且生成于中心時(shí)滲透率的減小幅度大于生成于壁面時(shí)。 同時(shí)研究了不同的孔隙率，不同的水合物飽和度條件以及水合物在孔隙中不同的位置生成時(shí)氣、水兩相相對滲透率的變化。當(dāng)水合物生成位置是孔隙壁面時(shí)，兩相相對滲透率下降較慢，而水合物生成位置是孔隙中心時(shí)，滲透率下降較快，且在壁面生成時(shí)的兩相滲透率等滲點(diǎn)高于中心生成時(shí)，同時(shí)發(fā)現(xiàn)水合物無論在中心還是在壁面生成，氣、液兩相滲透率都不隨孔隙率及水合物飽和度的變化而變化。 對微觀尺度下多孔介質(zhì)中天然氣水合物分解特性進(jìn)行了影響因素敏感性分析，結(jié)果表明，水合物分解速度常數(shù)、多孔介質(zhì)孔隙率、初始溫度、出口壓力、初始飽和度等均會(huì)影響多孔介質(zhì)中天然氣水合物分解速率，而多孔介質(zhì)孔徑分布對分解速率影響不大。 本文通過數(shù)值模擬的方法研究了多孔介質(zhì)中水合物飽和度與滲透率之間的關(guān)系及水合物分解特性，對于正確的進(jìn)行天然氣水合物開采評(píng)價(jià)具有重要的借鑒意義，，為水合物開采方法及開采技術(shù)的確定提供理論支持。
[Abstract]:As a kind of potential energy with rich reserves, high energy density and clean combustion, gas hydrate has been paid more and more attention by more and more countries. At present, many countries in the world have carried out research on gas hydrate. It includes the research of gas hydrate exploitation technology and hydrate application technology, and has made great progress. Natural gas hydrate is mainly stored in marine sediments and permafrost zones in nature. The complex geological environment makes it difficult to exploit gas hydrate. The extraction of hydrate is a complicated process, and there are many influencing factors, and the gas and water two-phase flow will greatly affect the decomposition process of hydrate. In this paper, the method of numerical simulation is used. The decomposition process of natural gas hydrate in porous media is studied. Based on the theory of percolation mechanics and pore network model, the following conclusions are drawn from the microscopic level: a three-dimensional cubic pore network model is established. The effects of hydrate saturation and pore size distribution on the phase equilibrium of hydrate are studied. Darcy's law is used as the theoretical basis to simulate the permeability change caused by the different position of hydrate formation in porous media. No matter whether the hydrate is formed at the center or on the wall, the permeability decreases with the increase of hydrate saturation, and the decrease of permeability at the center is larger than that at the wall. At the same time, the changes of relative permeability of gas and water are studied under different porosity, different hydrate saturation conditions and gas and water relative permeability when hydrate is generated at different locations in the pores. When the formation position of hydrate is on the pore wall, the relative permeability of two phases decreases more slowly, while when the location of hydrate formation is the center of the pore, the permeability decreases more quickly, and the equipermeability point of the two phase is higher than that of the center when the gas hydrate is formed on the wall. At the same time, it is found that the permeability of gas and liquid does not change with the change of porosity and hydrate saturation, regardless of the formation of hydrate in the center or on the wall. The factors influencing the decomposition characteristics of natural gas hydrate in porous media are analyzed. The results show that the rate constant of hydrate decomposition, porosity of porous media, initial temperature, exit pressure, and so on. Initial saturation and so on will affect the decomposition rate of natural gas hydrate in porous media, but pore size distribution in porous media has little effect on the decomposition rate. In this paper, the relationship between hydrate saturation and permeability in porous media and the characteristics of hydrate decomposition are studied by means of numerical simulation, which is of great significance for the correct evaluation of natural gas hydrate exploitation. It provides theoretical support for the determination of hydrate mining method and mining technology.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TE312

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本文編號(hào)：2198790