本文選題：煤層氣　切入點(diǎn)：液氮壓裂　出處：《西南石油大學(xué)》2015年碩士論文

【摘要】：水力壓裂是煤層氣儲(chǔ)層增產(chǎn)改造的重要措施。我國的煤層氣增產(chǎn)改造技術(shù)是建立在中、低階煤層氣開發(fā)理論、經(jīng)驗(yàn)基礎(chǔ)之上,對(duì)高階煤層氣儲(chǔ)層的適應(yīng)性較差,導(dǎo)致開發(fā)過程常面臨單井產(chǎn)量低的難題。高階煤層氣儲(chǔ)層孔滲性差,增產(chǎn)改造過程需增加煤層破碎程度,提高煤層氣解吸和滲流能力,才能大幅提高單井產(chǎn)量�；谔岣呙簩悠扑槌潭鹊睦砟�,本文提出了煤層氣井液氮壓裂技術(shù)。在前人關(guān)于液氮壓裂增產(chǎn)機(jī)理和工藝研究的基礎(chǔ)上,通過實(shí)驗(yàn)、模擬、理論計(jì)算等手段對(duì)液氮壓裂過程中溫度場(chǎng),液氮注入對(duì)煤層巖石滲透率、巖石力學(xué)性質(zhì)、地應(yīng)力及應(yīng)力敏感性等方面的影響進(jìn)行了研究,主要得到以下成果： (1)調(diào)研分析了沁水盆地南部高階煤層氣儲(chǔ)層特征、液氮壓裂技術(shù)優(yōu)勢(shì)及液氮作為壓裂液的經(jīng)濟(jì)適用性,得出液氮壓裂技術(shù)具有可行性,并提出了液氮壓裂的工藝流程及液氮注入導(dǎo)致煤層破壞的五種模式。 (2)建立了油管注液氮、油套環(huán)空注氮?dú)獾木矞囟葓?chǎng)計(jì)算模型,通過編制Matlab程序計(jì)算了不同條件下井筒內(nèi)液氮的溫度分布。采用COMSOL Multiphysics軟件建立了考慮近井多裂縫、割理及地層流體相變的流熱耦合溫度場(chǎng)模型,計(jì)算得到了不同條件下近井和近縫地帶儲(chǔ)層的溫度分布。 (3)實(shí)驗(yàn)得到了不同凍融溫度范圍條件下,干燥與飽和水煤巖樣凍融前后滲透率的變化規(guī)律。凍結(jié)時(shí)間不變的條件下,凍融溫度范圍越大,煤巖樣滲透率升高幅度越大；飽和水煤巖樣滲透率升高幅度高于干燥煤巖樣。 (4)實(shí)驗(yàn)得到了飽和水煤巖樣在不同凍結(jié)溫度下的抗拉強(qiáng)度及不同凍融溫度范圍下凍融前后抗拉強(qiáng)度；還得到了不同凍融溫度范圍下飽和水煤巖樣凍融前后的楊氏模量、泊松比。凍結(jié)導(dǎo)致飽和水煤巖樣抗拉強(qiáng)度升高,溫度越低,抗拉強(qiáng)度越高；凍融導(dǎo)致煤巖樣楊氏模量降低、泊松比升高,抗拉強(qiáng)度降低,且凍融溫度范圍越大,抗拉強(qiáng)度降低越多。 (5)基于現(xiàn)有地應(yīng)力計(jì)算模式,建立了考慮溫度和一次凍融影響的地應(yīng)力計(jì)算模式,計(jì)算得到了不同凍結(jié)溫度和不同凍融溫度范圍條件下煤層水平地應(yīng)力的大小。溫度降低,煤層最大水平主應(yīng)力先減小后增大,最小水平主應(yīng)力減小,水平應(yīng)力差增大；低溫引起的水平地應(yīng)力變化能夠使煤層割理發(fā)生剪切破壞。凍融導(dǎo)致煤層最大、最小水平主應(yīng)力升高,最小水平主應(yīng)力升高幅度更大。凍融導(dǎo)致煤巖應(yīng)力敏感性增強(qiáng),且應(yīng)力敏感性隨凍融溫度范圍增大而增強(qiáng)。 (6)針對(duì)目前缺乏液氮壓裂現(xiàn)場(chǎng)試驗(yàn)的問題,根據(jù)論文的研究成果對(duì)現(xiàn)有的煤層氣井液氮壓裂增產(chǎn)工藝提出了改進(jìn)建議。
[Abstract]:Hydraulic fracturing is an important measure to increase the production of coalbed methane reservoir. The technology of increasing production of coalbed methane in our country is based on the theory and experience of developing coal bed methane of middle and low order, and its adaptability to high order coalbed methane reservoir is poor. As a result, the development process often faces the problem of low production rate of single well. The porosity and permeability of high order coalbed methane reservoir is poor, and the degree of coal seam fragmentation and the ability of desorption and percolation of coal bed gas should be increased in the process of increasing production and reforming. Based on the idea of increasing the degree of coal seam breakage, this paper puts forward the liquid nitrogen fracturing technology for coalbed methane wells. Based on the previous researches on the mechanism and technology of liquid nitrogen fracturing, through experiments, simulation, The effects of temperature field and liquid nitrogen injection on permeability, rock mechanical properties, in-situ stress and stress sensitivity during liquid nitrogen fracturing are studied by means of theoretical calculation. The main results are as follows:. The characteristics of high-order coalbed methane reservoirs in the southern Qinshui Basin, the advantages of liquid nitrogen fracturing technology and the economic applicability of liquid nitrogen as fracturing fluid are investigated and analyzed, and the feasibility of liquid nitrogen fracturing technology is obtained. The process flow of liquid nitrogen fracturing and five modes of coal seam failure caused by liquid nitrogen injection are put forward. (2) the wellbore temperature field calculation model for tubing injection of liquid nitrogen and oil ring air nitrogen injection is established, and the temperature distribution of liquid nitrogen in wellbore under different conditions is calculated by compiling Matlab program. COMSOL Multiphysics software is used to establish a multi-fracture model for near well. The fluid-heat coupled temperature field model of cleat and phase transition of formation fluid is used to calculate the temperature distribution of the reservoirs in the near well and near fracture zone under different conditions. The permeability of dry and saturated water coal samples before and after freezing and thawing is obtained under different freezing and thawing temperature ranges. The larger the freezing and thawing temperature range is, the greater the permeability of coal and rock samples is under the condition of constant freezing time. The permeability of saturated coal samples is higher than that of dry coal samples. The tensile strength of saturated water-coal samples at different freezing temperatures and the tensile strength before and after freezing and thawing at different freezing and thawing temperatures were obtained by experiments, and the Young's modulus of saturated water-coal samples before and after freezing and thawing were obtained under different freezing and thawing temperatures. Poisson's ratio. Freezing causes the tensile strength of saturated coal and rock samples to increase, and the lower the temperature, the higher the tensile strength. Freezing and thawing cause the Young's modulus of coal and rock samples to decrease, Poisson's ratio to increase, tensile strength to decrease, and the range of freezing and thawing temperature to increase. The more the tensile strength decreases. 5) based on the existing calculation model of in-situ stress, a calculation model of in-situ stress considering the influence of temperature and primary freezing and thawing is established, and the horizontal ground stress of coal seam under different freezing temperature and different freezing and thawing temperature range is calculated. The maximum horizontal principal stress of coal seam decreases first and then increases, the minimum horizontal principal stress decreases and the horizontal stress difference increases, the variation of horizontal ground stress caused by low temperature can cause shear failure of coal seam cleats, and freezing and thawing results in the largest coal seam. The minimum horizontal principal stress increases and the minimum horizontal principal stress increases more. Freezing and thawing increase the stress sensitivity of coal and rock, and the stress sensitivity increases with the increase of freezing and thawing temperature. (6) in view of the lack of liquid nitrogen fracturing field test at present, according to the research results of the paper, some suggestions for improving the existing liquid nitrogen fracturing technology of coalbed gas wells are put forward.
【學(xué)位授予單位】：西南石油大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TE357

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