【摘要】：煤層瓦斯是威脅礦井安全生產(chǎn)的主要災(zāi)害之一,其抽采效率在很大程度上取決于滲流特性。長期的低滲透油氣藏開發(fā)實踐表明,流體在低滲多孔介質(zhì)中的流動為帶有啟動壓力梯度的低速非達西滲流。但是,現(xiàn)行瓦斯抽采技術(shù)大多遵循線性滲流理論,往往忽略了低滲煤層內(nèi)存在的低速非線性滲流及擴散現(xiàn)象,導(dǎo)致抽采難易程度評價及抽采工藝選擇出現(xiàn)偏差。針對不同煤體結(jié)構(gòu)煤層,如何快速、準確地評價其抽采難易程度以及選擇適宜的抽采工藝,以實現(xiàn)瓦斯高效抽采,是亟待解決的問題。而解決該問題的前提及關(guān)鍵,在于對瓦斯在不同煤體結(jié)構(gòu)煤層內(nèi)流動狀態(tài)的把握。為此本文就低滲煤層瓦斯非達西滲流特征展開研究�；诿簶涌紫督Y(jié)構(gòu)分析結(jié)果,實驗探討了啟動壓力梯度與滲透率的關(guān)系;采用啟動壓力梯度測試系統(tǒng),以采自不同煤礦的具有不同煤體結(jié)構(gòu)的煤樣為對象,分別研究了圍壓、氣體性質(zhì)、含水率對啟動壓力梯度的影響。研究表明:(1)滲透率與啟動壓力梯度之間呈負指數(shù)關(guān)系;(2)不同破壞類型煤體之間啟動壓力梯度存在較大差異,表現(xiàn)為Ⅰ類煤和Ⅳ類煤的啟動壓力梯度最大。Ⅱ類煤的啟動壓力梯度最小。Ⅲ類煤的啟動壓力梯度介于中間;(3)對于每一類煤,圍壓越大啟動壓力梯度越大,同時圍壓較低時四類煤啟動壓力梯度值差異較大,圍壓較高時,四類煤啟動壓力梯度值逐漸接近;(4)對于Ⅰ類煤的每一個煤芯,三種氣體滲流時啟動壓力梯度的關(guān)系為:氮氣甲烷二氧化碳;(5)對于每一類煤,含水率在1%~7%范圍內(nèi)時,隨著含水率增加,啟動壓力梯度逐漸增大�；谧冃慰刂品匠膛c氣固耦合滲流方程,借助COMSOL-Multiphysics軟件探討了圍壓、不同氣體、進氣壓力對啟動壓力梯度的影響,數(shù)值模擬結(jié)果表明:(1)在一定范圍內(nèi)隨著圍壓增大,啟動壓力梯度逐漸增大。(2)不考慮吸附作用時,三種氣體滲流時啟動壓力梯度的關(guān)系為:氮氣甲烷二氧化碳�？紤]吸附作用時,三種氣體滲流時啟動壓力梯度的關(guān)系為:二氧化碳甲烷氮氣。造成這種現(xiàn)象的原因是吸附作用影響了試件的應(yīng)力敏感系數(shù),導(dǎo)致試件的強度發(fā)生改變。(3)在試件參考線L1和參考點B上,進氣壓力越大,試件下部出氣口流量越大,滲透性越強,啟動壓力梯度越小。基于GSI煤體分類體系,對采自沙曲煤礦的具有不同煤體結(jié)構(gòu)的煤樣進行了定量表征,探討了GSI與啟動壓力梯度的關(guān)系;在此基礎(chǔ)上,初步提出了基于啟動壓力梯度的低滲煤層瓦斯流態(tài)判識方法。研究表明:對于沙曲煤礦而言:當(dāng)GSI=46.58時,λ=0,瓦斯流態(tài)為線性滲流;當(dāng)GSI46.58時,λ=0.00189(46.58-GSI)1.49665,λ隨GSI的減小而增大;當(dāng)GSI46.58時,λ=0.00189(GSI-46.58)1.50559,λ隨GSI的增大而增大;對于GSI≠46.58時,若Δp/L≥λ,瓦斯流態(tài)為低速非線性滲流;若Δp/Lλ,瓦斯流態(tài)為擴散。
[Abstract]:Coal seam gas is one of the main disasters threatening mine safety production, and its extraction efficiency depends on seepage characteristics to a great extent. The long term practice of developing low permeability reservoirs shows that the flow of fluid in low permeability porous media is low speed non Darcy seepage with starting pressure gradient. However, most of the current gas drainage techniques follow the linear seepage theory and often ignore the phenomenon of low speed nonlinear seepage and diffusion in low permeability coal seams, which leads to the deviation of the evaluation of drainage difficulty and the selection of extraction technology. It is an urgent problem how to quickly and accurately evaluate the difficulty and ease of drainage and how to select the appropriate extraction technology to realize the high efficiency of gas extraction in different coal structure coal seams. The premise and key to solve this problem is to grasp the flow state of gas in coal seam with different coal structure. Therefore, the characteristics of gas non Darcy seepage in low permeability coal seam are studied in this paper. Based on the results of pore structure analysis of coal samples, the relationship between starting pressure gradient and permeability is discussed experimentally, and the confining pressure of coal samples with different coal body structure is studied by using starting pressure gradient test system. The effect of gas properties and moisture content on the starting pressure gradient. The results show that: (1) there is a negative exponential relationship between permeability and starting pressure gradient, and (2) there are great differences in starting pressure gradient between different failure types of coal. The starting pressure gradient of type 鈪，

本文編號：2191423