本文選題：低階煤 + 內(nèi)在水分��； 參考：《中國(guó)礦業(yè)大學(xué)》2017年博士論文

【摘要】：目前針對(duì)中高階煤的理論研究和勘探開(kāi)發(fā)已較為成熟,盡管我國(guó)的低煤階煤層氣儲(chǔ)量也相當(dāng)可觀,但是目前仍處于科研攻關(guān)階段。低階煤具有不同于中高階煤的物化性質(zhì)和孔裂隙構(gòu)成等特征,并顯現(xiàn)出高含水率的特點(diǎn),從而導(dǎo)致低階煤在煤巖力學(xué)性質(zhì)及固氣相互作用等方面與中高階煤存在較大差異。以園子溝井田低煤階儲(chǔ)層2#煤層(Ro,max=0.65%)為研究背景,針對(duì)2#煤層的高內(nèi)在水分含量和“高壓力、低含量”的瓦斯賦存特征,綜合運(yùn)用巖石力學(xué)、損傷力學(xué)、滲流力學(xué)和吸附科學(xué)等理論方法,開(kāi)展了煤、氣、水共存條件下,水分對(duì)煤的吸附與解吸特性、力學(xué)損傷特征和滲透率演化規(guī)律的影響研究,進(jìn)而分析內(nèi)在水分對(duì)抽采過(guò)程中瓦斯運(yùn)移的影響。主要獲得以下結(jié)論:1)低階煤具有含量較多的羥基等含氧官能團(tuán)以及較為發(fā)達(dá)的微孔孔隙,使得園子溝低階煤的持水能力明顯高于中高階煤的,最高內(nèi)在水分含量為9.91%;水分對(duì)低階煤吸附能力的弱化影響顯著,Langmuir體積從干燥狀態(tài)的39.97cm3/g以68.7%幅度降低至含水率6.90%時(shí)的12.51cm3/g,這與低階煤的強(qiáng)持水特性有關(guān);相比傳統(tǒng)的線性式,負(fù)指數(shù)式能更好地描述濕煤吸附量與含水率的關(guān)系。低階煤的擴(kuò)散系數(shù)與含水率表現(xiàn)出增減交替的變化趨勢(shì),這與氣態(tài)水在煤孔隙內(nèi)集聚后對(duì)瓦斯擴(kuò)散的阻礙,以及瓦斯吸附量降低的綜合作用有關(guān)。2)黏聚力降低是導(dǎo)致型煤和原煤遇水后強(qiáng)度弱化的主因;在常規(guī)三軸壓縮試驗(yàn)中,不含瓦斯時(shí),型煤和原煤的強(qiáng)度分別表現(xiàn)為指數(shù)式以及近似線性的降低趨勢(shì);原煤的黏聚力為3.49~7.93MPa,是型煤的大約6倍,并且水分對(duì)兩種煤的內(nèi)摩擦角影響不明顯,而黏聚力均表現(xiàn)出顯著降低的趨勢(shì)。氣-水共存時(shí),煤吸附氣體和水分造成了煤表面能的降低,導(dǎo)致煤的強(qiáng)度弱化;當(dāng)瓦斯壓力不變時(shí),水分增加導(dǎo)致瓦斯吸附作用對(duì)煤強(qiáng)度的弱化影響逐漸減弱,因此隨含水率增加,煤強(qiáng)度仍在降低,而瓦斯對(duì)煤強(qiáng)度的軟化系數(shù)表現(xiàn)出增大趨勢(shì)。3)構(gòu)建了基于Drucker-Prager強(qiáng)度準(zhǔn)則并服從Weibull函數(shù)分布的含瓦斯煤巖細(xì)觀統(tǒng)計(jì)損傷模型。該模型可較好的反演含水瓦斯煤的應(yīng)力應(yīng)變關(guān)系,并反映出水分和瓦斯氣體誘發(fā)并促進(jìn)煤體損傷發(fā)展的特征。水分比瓦斯氣體對(duì)聲發(fā)射活動(dòng)的抑制作用更顯著,相比干燥煤樣,不含瓦斯時(shí)飽水煤樣的AE計(jì)數(shù)和能量累計(jì)值分別降低了14.32倍和23.42倍;并且隨著含水率增加,煤巖的破壞呈現(xiàn)出由突然破裂型向穩(wěn)定破裂型轉(zhuǎn)變,脆性減弱而塑性破壞特征增強(qiáng)的趨勢(shì)。4)煤基質(zhì)吸附瓦斯氣體和內(nèi)在水分的膨脹變形效應(yīng),和有效應(yīng)力共同影響著滲透率的動(dòng)態(tài)演化。靜水壓條件等圍壓時(shí),當(dāng)內(nèi)在水分含量較高時(shí),煤的滲透率表現(xiàn)出隨瓦斯壓力增加而逐漸增大趨勢(shì),這是由于煤吸附瓦斯的膨脹變形效應(yīng)因水分的吸附作用而變?nèi)?此時(shí)有效應(yīng)力起控制作用。全應(yīng)力應(yīng)變過(guò)程中,煤巖聲發(fā)射活動(dòng)和損傷變量與滲透率演化整體上表現(xiàn)出一致性,壓密和彈性階段,聲發(fā)射平靜,損傷變量基本為0,滲透率降低了數(shù)倍;峰后階段,聲發(fā)射密集,干、濕煤的滲透率驟增約2~3個(gè)數(shù)量級(jí);損傷變量迅速增加,并趨近于1。5)構(gòu)建了基于單軸應(yīng)變假設(shè),表征彈性階段內(nèi)煤巖滲透率演化并考慮水分影響的SD滲透率改進(jìn)模型。利用該模型計(jì)算得到低階煤吸附瓦斯的極限膨脹變形量與含水率符合負(fù)指數(shù)關(guān)系;結(jié)合煤的吸附參數(shù)、變形參數(shù)及滲透參數(shù)與含水率的關(guān)系,SD改進(jìn)模型可較好的反演靜水壓下滲透率數(shù)據(jù)變化規(guī)律,并且能反映出不同內(nèi)在水分含量條件下煤巖滲透率動(dòng)態(tài)演化特征。全應(yīng)力應(yīng)變過(guò)程中,結(jié)合細(xì)觀統(tǒng)計(jì)損傷模型和SD改進(jìn)模型,并引入損傷變量和滲透率驟增系數(shù),構(gòu)建了應(yīng)力擾動(dòng)作用下考慮水分影響的滲透率模型。6)基于煤的“雙孔-單滲”彈性介質(zhì)特性,結(jié)合擴(kuò)散方程、滲流方程和SD滲透率改進(jìn)模型以及煤體變形方程,構(gòu)建了煤、氣、水耦合作用下的煤層瓦斯運(yùn)移模型。COMSOL軟件解算結(jié)果表明,初始瓦斯含量相同時(shí),煤的吸附能力和初始滲透率對(duì)抽采過(guò)程中瓦斯運(yùn)移以及煤層相對(duì)瓦斯含量的影響最大。因此,對(duì)于原位低煤階儲(chǔ)層,初始滲透率一定時(shí),內(nèi)在水分含量較高導(dǎo)致煤吸附能力較低、游離氣含量比例增大而瓦斯壓力也較大,對(duì)于煤層瓦斯抽采具有一定的積極作用。
[Abstract]:At present, according to the theoretical research and the exploration and development of high rank coal has been mature, although the low rank coal gas reserves in China are also considerable, but it is still in the research stage. The low rank coal has physical and chemical properties and pore fracture in high rank structure characteristics, and shows the characteristics of high moisture content the resulting low rank coal in the coal and rock mechanics and solid gas interaction with high rank differences. In the garden Gou mine low rank coal reservoirs in 2# coal seam (Ro, max=0.65%) as the research background, according to the 2# coal seam in high water content and high pressure gas occurrence characteristics low content, comprehensive use of rock mechanics, damage mechanics, seepage mechanics and adsorption science theories and methods to carry out coal, gas and water under the condition of coexistence, adsorption and desorption characteristics of coal with water, affecting the mechanical damage characteristics and permeability evolution law The research, then analyze the effect of internal water drainage in the process of gas migration. The main conclusions are as follows: 1) the low rank coal has higher content of hydroxyl functional groups containing oxygen and micro pore is more developed, so that the water holding capacity of garden ditch of low rank coal was significantly higher than that in high rank coal, high inherent moisture content 9.91%; water weakening of low rank coal adsorption capacity significantly affect the volume of Langmuir from the dry state at 68.7% 39.97cm3/g to reduce the moisture content is 6.90% 12.51cm3/g, and the low rank coal with strong water holding characteristics; compared to the traditional linear, negative exponential can better describe the relationship between adsorption quantity and wet coal moisture diffusion coefficient and moisture content. The low rank coal rate showed a trend or alternate, the obstacles of the gas diffusion and the water vapor concentration in coal pores, comprehensive cooperation and reduce the volume of a gas adsorption .2) is a major cause of cohesion decreases the strength weakening of coal and raw water; in conventional triaxial compression tests of the three, without gas, coal and raw strength respectively for the performance index and the approximate linear decrease trend; cohesion of coal is 3.49~7.93MPa, is about 6 times higher than coal, and the water of the two coal internal friction angle and cohesion effect is not obvious, showed significant decreasing trend. The coexistence of gas and water, coal gas and water adsorption resulted in the decrease of coal surface energy, resulting in the weakening of the strength of coal; when the gas pressure is constant, the increase of moisture leads to weakening of gas adsorption on coal the strength of the effect gradually weakened, so with the increase of water content, coal strength is still lower, and the gas of coal strength softening coefficient showed increasing trend of.3) Drucker-Prager was constructed based on strength criterion and obey the distribution function of Weibull containing gas The coal rock meso statistical damage model. The model of coal gas water inversion shows the relationship between stress and strain, and reflect the characteristics of water and gas induced damage of coal and promote development. More significant inhibition of water gas ratio on the acoustic emission activities, compared to dry coal samples, AE count and energy the gas containing water saturated coal samples of the cumulative values were decreased by 14.32 times and 23.42 times; and with the increase of water content of coal and rock damage by showing a sudden rupture to stable fracture transformation, brittle weakened and plastic damage characteristics of increased.4) expansion deformation of coal matrix adsorption gas and moisture the effective stress and affect the dynamic evolution of permeability. The hydrostatic pressure conditions of confining pressure, when high inherent moisture content, the permeability of coal showed a gradually increasing trend with the increase of gas pressure, which is due to The swelling deformation effect of gas adsorption of coal by adsorption of water becomes weak, the effective stress control. The complete stress-strain process, coal rock acoustic emission and damage variable and permeability evolution integralaffections consistency, compression and elastic stage, AE quiet, as the basic damage variable 0, the permeability decreased by several times; after peak phase, the acoustic emission intensity, dry, wet coal permeability increased about 2~3 orders of magnitude; the damage variable is increasing rapidly, and close to 1.5) was constructed based on the assumption of uniaxial strain, improved SD permeability characterization in elastic phase permeability evolution and considering effects of moisture model. The calculated ultimate low rank coal gas adsorption using the model of swelling deformation and moisture content accords with negative exponential relationship; combined with the coal adsorption parameters, deformation parameters and permeability parameters and water content, improved SD model can better anti Do the static permeability change rule data under pressure, and can reflect the dynamic evolution characteristics of coal permeability of different inherent moisture conditions. The complete stress-strain process, combined with the meso statistical damage model and improved SD model, and the damage variable and the permeability coefficient increased, constructed.6 permeability model under the action of force disturbance considering the effects of moisture) of coal "double - and single permeability" elastic medium characteristics based on the combination of the diffusion equation, flow equation and SD equation model and improved permeability deformation of coal, coal gas, construction, water coupling for coal layer gas migration model.COMSOL software calculation results show that the initial gas content of the same and the influence of coal adsorption capacity and initial permeability on the recovery process of gas migration and coal seam gas content. Therefore, for in situ low rank coal reservoir, the initial permeability of a timing, internal Higher moisture content leads to lower adsorption capacity of coal, higher free gas content and higher gas pressure, which plays a positive role in coal seam gas drainage.

【學(xué)位授予單位】：中國(guó)礦業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TD712
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本文編號(hào)：1750898