本文關(guān)鍵詞： CO_2地質(zhì)封存 兩相滲流 溶解 相對滲透率 巖心與微觀模型　出處：《中國地質(zhì)大學(xué)(北京)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：CO_2地質(zhì)封存被認(rèn)為是目前減輕溫室效應(yīng)的有效途徑之一。深部咸水含水層由于其分布廣泛,儲存空間巨大,被認(rèn)為是進(jìn)行CO_2地質(zhì)封存的理想場所。在進(jìn)行CO_2咸水含水層封存數(shù)值模擬研究時,CO_2和地層水間的溶解被認(rèn)為是瞬時完成的平衡溶解過程。然而由于巖石多孔介質(zhì)孔隙、孔隙網(wǎng)絡(luò)結(jié)構(gòu)的復(fù)雜性,以及超臨界CO_2(scCO_2)和地層水之間粘度差異,很可能導(dǎo)致scCO_2/水兩相無法自由接觸,有限的接觸面積將極大地限制scCO_2的溶解過程,出現(xiàn)非平衡溶解的現(xiàn)象。值得一提的是,scCO_2的非平衡溶解受到兩相滲流的影響,溶解也會對兩相滲流具有一定的反饋?zhàn)饔?即發(fā)生兩種機(jī)制的耦合。為了系統(tǒng)全面的研究scCO_2與水間的溶解及滲流場和化學(xué)場的耦合過程,分別進(jìn)行了巖心尺度和孔隙尺度微觀模型驅(qū)替實(shí)驗(yàn)。巖心尺度驅(qū)替實(shí)驗(yàn)是利用采集自鄂爾多斯盆地的典型低滲透砂巖,在8-10 MPa,40°C條件下完成的。實(shí)驗(yàn)過程中首先將巖心飽和水并進(jìn)行scCO_2驅(qū)替實(shí)驗(yàn)。在建立殘余水飽和度后,進(jìn)行純水驅(qū)替實(shí)驗(yàn)。通過收集和測定巖心出口端流出水中溶解CO_2含量,得到了scCO_2-水在低滲透砂巖巖心中的溶解過程。實(shí)驗(yàn)結(jié)果表明,水中溶解CO_2含量隨著驅(qū)替時間變化,并小于實(shí)驗(yàn)條件下的CO_2溶解度1-2個數(shù)量級,證明了CO_2-水的非平衡溶解過程。通過改變驅(qū)替水中溶解CO_2含量背景值和注水速率,對該非平衡溶解過程進(jìn)行了敏感性分析,建立了CO_2溶解速率隨濃度變化的數(shù)值模型。為進(jìn)一步解釋巖心尺度觀測結(jié)果,進(jìn)行了孔隙尺度微觀模型驅(qū)替實(shí)驗(yàn)。首先在一單晶硅芯片上,利用微觀孔隙刻蝕技術(shù),重現(xiàn)真實(shí)砂巖巖心的2D孔隙網(wǎng)絡(luò)結(jié)構(gòu)。在該微觀模型中,在9 MPa和40°C條件下,進(jìn)行了與巖心尺度實(shí)驗(yàn)過程相似的水驅(qū)替實(shí)驗(yàn)。利用微觀顯微鏡成像技術(shù),捕捉到了實(shí)時的孔隙尺度scCO_2-水兩相滲流與溶解過程。通過圖像分析,得到了scCO_2-水非平衡溶解的最直接證據(jù):由于孔隙網(wǎng)絡(luò)結(jié)構(gòu)的非均一性引起水流的優(yōu)勢流,導(dǎo)致scCO_2-水之間非常有限的接觸面積。水中溶解CO_2含量小于實(shí)驗(yàn)條件下的CO_2溶解度1-3個數(shù)量級。此外,與傳統(tǒng)相對滲透率曲線模型和觀測結(jié)果不同,孔隙尺度實(shí)驗(yàn)還觀測到了溶解參與下的水相相對滲透率與水相飽和度之間呈現(xiàn)非單調(diào)性的變化規(guī)律。其原因歸結(jié)于孔隙網(wǎng)絡(luò)的雙滲透性模式及CO_2的非平衡溶解過程�？紫冻叨葘�(shí)驗(yàn)為巖心尺度驅(qū)替實(shí)驗(yàn)結(jié)果提供了很好的解釋與論證,加深了人們對CO_2束縛氣封存與溶解封存機(jī)制間轉(zhuǎn)換的理解。兩相滲流與溶解耦合過程的研究結(jié)果也會對其他資源開采(如頁巖水力壓裂、CO_2提高石油、煤層氣采收率、CO_2開發(fā)地?zé)岬?過程中的多場耦合問題有所啟發(fā)。
[Abstract]:CO_2 geological storage is considered to be one of the effective ways to reduce Greenhouse Effect. Because of its wide distribution, deep salt water aquifer has huge storage space. It is considered to be an ideal place for CO_2 geological storage. In the numerical simulation of the storage of CO_2 salt water aquifer, the dissolution between CO-2 and formation water is considered to be an instantaneous equilibrium dissolution process. However, due to the pore of porous medium in rock, The complexity of the pore network structure and the viscosity difference between the supercritical COSP _ 2 scCO _ 2) and the formation water are likely to lead to a lack of free contact between the scCO2 / water phases, and the limited contact area will greatly limit the dissolution process of the scCO_2. It is worth mentioning that the non-equilibrium dissolution of scCO2 is affected by the two-phase seepage, and the dissolution will have a certain feedback effect on the two-phase seepage. In order to study the dissolving process between scCO_2 and water and the coupling process of seepage field and chemical field, The core scale displacement experiments were carried out on the micro model of core scale and pore scale respectively. The core scale displacement experiment is based on the typical low permeability sandstone collected from the Ordos Basin. The experiment was carried out under the condition of 8-10 MPA ~ (40 擄C). In the experiment, the saturated core water was first saturated and the scCO_2 displacement experiment was carried out. After the residual water saturation was established, the pure water displacement experiment was carried out. The dissolved CO_2 content in the effluent water from the outlet of the core was collected and measured. The dissolution process of scCO2- water in low permeability sandstone core is obtained. The experimental results show that the dissolved CO_2 content in water varies with the displacement time and is less than 1-2 orders of magnitude of CO_2 solubility under experimental conditions. The non-equilibrium dissolution process of CO2-water was proved. The sensitivity of the disequilibrium dissolution process was analyzed by changing the background value of dissolved CO_2 content and the water injection rate. A numerical model of the variation of CO_2 dissolution rate with concentration was established. In order to further explain the core scale observation results, the pore scale micro model displacement experiment was carried out. Firstly, the micro pore etching technique was used on a single crystal silicon chip. The 2D pore network structure of the true sandstone core is reproduced. In this microscopic model, water displacement experiments similar to the core-scale experimental process are carried out under 9 MPa and 40 擄C conditions. The microscopic imaging technique is used. The real time pore scale scCO2- water two-phase seepage and dissolution process is captured. By image analysis, the most direct evidence of scCO-2- water non-equilibrium dissolution is obtained: the dominant flow caused by the heterogeneity of pore network structure. This leads to a very limited contact area between SCCO2- water. The dissolved CO_2 content in the water is smaller than the CO_2 solubility of 1-3 orders of magnitude under experimental conditions. In addition, it is different from the traditional relative permeability curve model and the observed results. The porosity scale experiment also observed that the relative permeability of water phase and the saturation of water phase show the variation law of non-monotonicity under the participation of dissolution. The reason is attributed to the double permeability model of pore network and the non-equilibrium dissolution of CO_2. The pore scale experiment provides a good explanation and demonstration for the experimental results of core displacement. The results of two-phase percolation and dissolution coupling process will also improve the oil production of other resources (such as shale fracturing and COSP _ 2). The problem of multi-field coupling in the process of coal bed methane recovery is enlightening.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：X701;X141

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本文編號：1547829