本文選題：解吸機(jī)理 + 裂隙　； 參考：《內(nèi)蒙古科技大學(xué)》2015年碩士論文

【摘要】：我國(guó)煤層普遍具有低滲透性的特點(diǎn)，不利于煤層氣的開(kāi)采。為了提高煤層的滲透性，一些新的增透措施正在被研究利用，比如氣爆增透技術(shù)、超聲激勵(lì)煤層增透技術(shù)，其中包括高壓電脈沖技術(shù)。該項(xiàng)技術(shù)起初是被應(yīng)用于石油開(kāi)采中，后被嫁接到煤層氣開(kāi)采中，作為一種新的煤層增透技術(shù)，尚處于研究起步階段，因此存在許多問(wèn)題尚需解決。本文綜合利用力學(xué)理論知識(shí)、試驗(yàn)研究和有限元軟件模擬，對(duì)該項(xiàng)技術(shù)在鉆孔注水煤層中的增透效果進(jìn)行分析研究，得出以下成果： （1）理論分析認(rèn)為煤層中裂隙的密度、長(zhǎng)度、寬度以及貫通程度越發(fā)育，煤層的滲透性就越高，就越易于煤層氣的解吸。根據(jù)巖石力學(xué)相關(guān)理論，推導(dǎo)出在試驗(yàn)中，孔壁產(chǎn)生新裂隙的起裂壓力應(yīng)不低于5.5MPa，理論計(jì)算結(jié)果與試驗(yàn)結(jié)果相吻合。然后通過(guò)斷裂力學(xué)，對(duì)靜水壓和脈沖壓力作用下裂隙尖端應(yīng)力強(qiáng)度因子的變化過(guò)程進(jìn)行分析，了解了裂隙擴(kuò)展的演化規(guī)律。 （2）根據(jù)以上理論分析在實(shí)驗(yàn)室進(jìn)行了鉆孔注水高壓電脈沖煤層增透試驗(yàn)，模擬3MPa靜水壓以及3MPa靜水壓條件下施加10kv高壓電脈沖后對(duì)煤樣的致裂效果。然后利用CT掃描儀對(duì)試驗(yàn)試件進(jìn)行掃描分析。由掃描結(jié)果可知：原煤樣致密、硬度高、無(wú)裂隙分布。3MPa靜水壓作用下，煤樣孔壁以及周邊沒(méi)有裂隙產(chǎn)生，而在3MPa靜水壓中施放10kv高壓電脈沖后，孔壁以及周邊的裂隙數(shù)目明顯增多，說(shuō)明水中高壓電脈沖技術(shù)對(duì)煤樣能夠起到理想的增透效果。 （3）利用ABAQUS擴(kuò)展有限元法，對(duì)鉆孔注水高壓電脈沖煤層增透試驗(yàn)進(jìn)行模擬，分析不同的靜水壓以及不同脈沖壓力作用下，煤樣裂隙的擴(kuò)展情況。模擬結(jié)果表明：當(dāng)鉆孔內(nèi)靜水壓達(dá)到3MPa時(shí)，裂隙長(zhǎng)度未發(fā)生變化，寬度有一定的變化。而當(dāng)靜水壓達(dá)到7.541MPa時(shí)，裂隙開(kāi)始延長(zhǎng)。當(dāng)在靜水壓中施加脈沖荷載后，裂隙的延伸長(zhǎng)度相比靜水壓顯著增加，并且延伸長(zhǎng)度隨著初始放電能量的增大而增大，說(shuō)明高壓電脈沖對(duì)煤樣的致裂效果要優(yōu)于靜水壓致裂效果，且初始放電能量越高致裂效果越好。伴隨著靜水壓和脈沖壓力的作用，在裂隙尖端產(chǎn)生一定的拉應(yīng)力，且拉應(yīng)力值隨著孔內(nèi)壓力的增大而增大，，這是導(dǎo)致裂隙擴(kuò)展延伸的主要原因。
[Abstract]:Coal seam in our country has the characteristic of low permeability, which is unfavorable to the exploitation of coalbed methane. In order to improve the permeability of coal seam, some new antireflection measures are being studied, such as gas explosion antireflection technology, ultrasonic stimulation coal seam antireflection technology, including high-voltage electric pulse technology. This technology was first applied in petroleum exploitation, then grafted into coalbed methane production. As a new coal seam antireflection technology, it is still in the initial stage of research, so there are many problems still to be solved. In this paper, the antireflection effect of this technique in borehole water injection coal seam is analyzed and studied by comprehensive use of mechanical theory knowledge, experimental research and finite element software simulation. The following results are obtained: (1) theoretical analysis shows that the more developed the density, length, width and penetration degree of fractures in coal seam, the higher the permeability of coal seam and the easier the desorption of coalbed methane. According to the relevant theory of rock mechanics, it is deduced that the initiation pressure of new cracks in the hole wall should not be less than 5.5 MPA in the experiment, and the theoretical calculation results are in agreement with the experimental results. Then through fracture mechanics, the variation process of stress intensity factor at crack tip under hydrostatic pressure and pulse pressure is analyzed. The evolution law of fracture propagation is understood. (2) according to the above theoretical analysis, the antipenetration test of high pressure electric pulse coal seam with borehole water injection has been carried out in the laboratory. The cracking effect of coal samples under 3MPa hydrostatic pressure and 3MPa hydrostatic pressure with 10kv high voltage electric pulse was simulated. Then the CT scanner is used to scan and analyze the test specimen. From the scanning results, it can be seen that under the condition of dense coal sample, high hardness and no fracture distribution under hydrostatic pressure of .3MPa, there is no fissure in the wall of coal sample and around it, but the 10kv high pressure electric pulse is applied in the hydrostatic pressure of 3MPa. The obvious increase in the number of holes in the wall and the surrounding cracks shows that the high voltage electric pulse technique in water can play an ideal antireflection effect on coal samples. (3) Abaqus extended finite element method is used. The antireflection test of high pressure electric pulse coal seam with borehole water injection was simulated, and the crack propagation of coal sample under different hydrostatic pressure and different pulse pressure was analyzed. The simulation results show that when the hydrostatic pressure of the borehole reaches 3 MPA, the crack length does not change and the width changes to a certain extent. When the hydrostatic pressure reaches 7.541 MPA, the fracture begins to extend. When the pulse load is applied to the hydrostatic pressure, the fracture extension length increases significantly compared with the hydrostatic pressure, and the extension length increases with the increase of the initial discharge energy. The results show that the cracking effect of high voltage electric pulse is better than that of hydrostatic pressure, and the higher the initial discharge energy is, the better the cracking effect is. Along with the action of hydrostatic pressure and pulse pressure, a certain tensile stress is produced at the crack tip, and the tensile stress value increases with the increase of the pressure in the hole, which is the main reason leading to the extension of the fracture.
【學(xué)位授予單位】：內(nèi)蒙古科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TE37

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