本文選題：煤層氣　切入點(diǎn)：超臨界二氧化碳　出處：《太原理工大學(xué)》2015年碩士論文

【摘要】：煤層氣是煤層形成過程中伴生的產(chǎn)物，俗稱瓦斯。主要成分與常規(guī)天然氣相同，都為甲烷氣體。眾所周知，瓦斯氣體的存在對(duì)井下作業(yè)人員的人身安全以及煤炭資源的財(cái)產(chǎn)安全都有重大威脅。瓦斯積聚達(dá)到一定濃度，一旦遇到明火就會(huì)引起爆炸，會(huì)給礦井作業(yè)帶來巨大的災(zāi)難。瓦斯危害一直是困擾我們的一個(gè)重大問題。另外，由于煤層氣的主要成分與天然氣相同，且在煤層中儲(chǔ)量豐富，如果能夠得以有效利用，我們目前這個(gè)資源短缺的現(xiàn)狀將會(huì)得到巨大改善。所以，如何將煤層氣變廢為寶，具有很大的現(xiàn)實(shí)意義和經(jīng)濟(jì)意義。 針對(duì)以上情況，本文進(jìn)行了氦氣測(cè)煤樣滲透率、溫度解吸、不同狀態(tài)下的二氧化碳驅(qū)替、驅(qū)替前后滲透率測(cè)定等試驗(yàn)，系統(tǒng)地研究了煤樣的滲透性能及對(duì)煤樣的驅(qū)替或解吸效率。主要的研究內(nèi)容和結(jié)果如下： 1）利用He測(cè)煤樣彈性階段、塑性階段直至斷裂破壞整個(gè)過程的滲透率，國內(nèi)煤層大多數(shù)是低滲煤層，瓦斯驅(qū)替對(duì)煤層滲透率有一定的要求，所以在驅(qū)替實(shí)驗(yàn)前，先進(jìn)行煤樣的滲透率測(cè)定實(shí)驗(yàn)。實(shí)驗(yàn)結(jié)果表明：試件在彈性階段，滲透率基本保持不變，進(jìn)入塑性階段后，煤體結(jié)構(gòu)、孔隙及裂隙呈現(xiàn)不規(guī)則變形，滲透率出現(xiàn)了較為明顯的波動(dòng)。隨著軸向應(yīng)力進(jìn)一步增大，試件進(jìn)入形變強(qiáng)化階段，在這一過程試件發(fā)生了大量而均勻的變形，裂隙通道進(jìn)一步被打開，滲透率急劇增大。 2）根據(jù)溫度越高，煤樣對(duì)氣體的吸附能力越差，把含甲烷飽和煤樣置于不同溫度的水浴中，溫度分別設(shè)為40℃、60℃、80℃，充分解吸。得出：溫度越高，解吸地越快，解吸出來的量也越多。將三個(gè)溫度下的驅(qū)替效率對(duì)比得出，在保溫階段，三組實(shí)驗(yàn)的解吸效率差距很小，是因?yàn)楸仉A段，雖然溫度高有利于氣體解析，但高溫同時(shí)會(huì)導(dǎo)致煤體膨脹，壓縮氣體運(yùn)移通道。而在升溫階段由于溫度一直在改變，煤體膨脹不均勻，會(huì)產(chǎn)生新的裂隙，導(dǎo)致解析效率差距明顯。 3）煤樣吸附甲烷至飽和，用常規(guī)二氧化碳驅(qū)替。發(fā)現(xiàn)吸附的甲烷量小于進(jìn)入的二氧化碳量，煤樣對(duì)二氧化碳的吸附能力大于對(duì)甲烷的吸附能力；設(shè)定孔隙壓分別為7MPa、8MPa，孔隙壓越大，驅(qū)替完成所需要的時(shí)間越短，并且驅(qū)替效率越高。在滲透率方面，驅(qū)替前的滲透率為0.0125mD，驅(qū)替后滲透率變?yōu)?.0067mD，滲透率明顯變小。所以常規(guī)二氧化碳驅(qū)替會(huì)使煤層滲透性能降低。 4）在亞臨界二氧化碳驅(qū)替飽和煤樣時(shí)，，由于CO2臨界溫度為31.26℃，臨界壓力為72.9atm。將孔隙壓設(shè)為7MPa，溫度分別設(shè)為40℃、60℃、80℃。發(fā)現(xiàn)40℃驅(qū)替效率最低，且到驅(qū)替完全用時(shí)最多，80℃驅(qū)替的驅(qū)替效率最高，但與60℃驅(qū)替差距很小。在滲透率方面：驅(qū)替后的滲透率為0.01496mD，與驅(qū)替前的滲透率0.01126mD相比，滲透率略微變大。所以亞臨界二氧化碳驅(qū)替會(huì)使煤層滲透性能提高，但提高的幅度很小。 5）在超臨界二氧化碳驅(qū)替時(shí)，將孔隙壓設(shè)為8MPa，溫度分別設(shè)為40℃、60℃、80℃。在驅(qū)替速率和驅(qū)替效率方面，與亞臨界驅(qū)替規(guī)律相近，都是40℃最低，80℃最高，且60℃和80℃驅(qū)替速率和效率都十分接近。但超臨界狀態(tài)的二氧化碳的驅(qū)替速率和效率都優(yōu)于亞臨界狀態(tài)的二氧化碳。在滲透率方面，驅(qū)替前的滲透率為0.01033mD，驅(qū)替之后的滲透率為0.01824mD，與驅(qū)替前的滲透率相比，滲透率變化很大，所以超臨界二氧化碳驅(qū)替會(huì)使煤層滲透性能大幅提高。
[Abstract]:Coal bed gas is associated with the formation process of coal seam , commonly known as gas . The main component is the same as that of conventional natural gas , it is methane gas . As is well known , the existence of gas gas has serious threat to the personal safety of underground operation personnel and the property safety of coal resources . As the main components of coal bed gas are the same as natural gas , and the reserves are abundant in the coal seam , the present situation of gas shortage will be greatly improved . Therefore , it is of great practical significance and economic significance to change the coal bed gas into treasure .

In view of the above conditions , the permeability , temperature desorption , carbon dioxide displacement and permeability determination of coal samples under different conditions are studied systematically . The permeability properties of coal samples and the displacement or desorption efficiency of coal samples are systematically studied . The main research contents and results are as follows :

1 ) Using He to measure the elastic phase of coal samples , the permeability of the whole process is destroyed by the plastic stage until the fracture , most of the domestic coal seams are low permeability coal seams , and the gas displacement has certain requirements on the permeability of the coal seam . The experimental results show that the permeability of the coal body is basically unchanged after the displacement experiment . The experimental results show that the coal body structure , the pores and the cracks exhibit irregular deformation after the displacement experiment , and the permeability has been obviously fluctuated . As the axial stress increases , the test piece enters the deformation strengthening stage , and the fracture channel is further opened and the permeability increases sharply .

2 ) According to the higher the temperature , the worse the adsorption capacity of the coal sample to the gas , the higher the temperature , the faster the desorption is , the more the desorption efficiency is .

3 ) the coal sample adsorbs methane to saturation , and is driven by conventional carbon dioxide , and the adsorption capacity of the coal sample on the carbon dioxide is larger than that of the incoming carbon dioxide , and the adsorption capacity of the coal sample to the carbon dioxide is larger than that of the methane ;
Setting the pore pressure is 7 MPa , 8 MPa , the greater the pore pressure , the shorter the time required for the completion of displacement and the higher the displacement efficiency . In terms of permeability , the permeability before displacement is 0.0125mD , the permeability after displacement becomes 0.0067mD , the permeability is obviously smaller . Therefore , the conventional carbon dioxide flooding can reduce the permeability of the coal bed .

4 ) At subcritical carbon dioxide displacement saturated coal sample , the critical temperature is 31.26 鈩

本文編號(hào)：1671877