發(fā)布時間：2018-04-30 16:05

  本文選題：頁巖 + 頁巖氣��； 參考：《西南石油大學》2015年碩士論文

【摘要】：頁巖氣藏屬烴源巖氣藏,儲層中含大量吸附氣,孔隙尺寸跨度大,有機孔、無機孔和微裂縫構(gòu)成了一個極為復(fù)雜的頁巖氣儲集和流動空間。因而,頁巖氣的產(chǎn)出是-個包括了解吸、擴散和滲流的多尺度傳質(zhì)過程。頁巖基塊中的氣體擴散作為這一過程的中間環(huán)節(jié),研究氣體擴散行為對認識頁巖氣的產(chǎn)出機理具有重要意義。同時,針對頁巖氣井水力壓裂后壓裂液返排率低、滯留嚴重的現(xiàn)象,開展壓裂液對頁巖中氣體擴散能力的潛在損害研究亦十分必要。 以四川盆地志留系龍馬溪組井下頁巖為研究對象,以頁巖中氣體擴散能力實驗描述為核心,建立了符合頁巖氣產(chǎn)出過程的擴散行為表征模型,設(shè)計了擴散系數(shù)實驗測試方法；對比分析了壓裂液自吸損害前后,甲烷在巖樣中的擴散系數(shù)變化,并給出了損害評價指標和預(yù)防控制措施。 分析表明,龍馬溪組井下頁巖(15組)礦物組成以石英、長石和黏土礦物為主,巖樣的平均孔隙度為3.45%,平均滲透率為0.056mD。儲層有機質(zhì)納米孔發(fā)育,孔隙直徑主要分布在3～100nm,其中直徑小于10nm的孔隙控制著50%-80%的孔隙空間。 明確了氣體在頁巖中的擴散類型和擴散階段。根據(jù)經(jīng)典的Kn數(shù)氣體流態(tài)劃分標準,頁巖基塊中的氣體擴散以Knudsen擴散為主。進一步,結(jié)合頁巖的微孔結(jié)構(gòu)特征和賦存狀態(tài),擴散過程可分為滑脫流中的Knudsen擴散、納米級孔隙氣體擴散和氣體向干酪根內(nèi)部的濃度擴散三個階段。 分析了KKnudsen擴散對頁巖中氣體滑脫流的貢獻率。推導(dǎo)了Knudsen擴散等效滲透率表征模型,并以甲烷低速滲流實驗數(shù)據(jù)驗證了模型的可靠性。通過引入氣測滲透率修正系數(shù)F,定量描述了KKnudsen擴散對整個傳質(zhì)過程的貢獻。隨著甲烷壓力和孔隙直徑的降低,F值可從略大于1升高到10以上。F的值越大,則表明Knudsen擴散的貢獻率越大。 建立了基于氣體壓力衰減的甲烷擴散系數(shù)實驗測試和損害評價方法。根據(jù)9組實驗數(shù)據(jù),損害前階段Ⅰ(納米級孔隙氣體擴散)中甲烷的擴散系數(shù)為3.78×10-13～7.04×10-13cm2/s,階段Ⅱ(干酪根中氣體擴散)中甲烷的擴散系數(shù)為2.89×10-17～3.29×10-16cm2/s；壓裂液自吸損害后,擴散系數(shù)明顯降低,階段Ⅰ的損害指數(shù)為0.18-0.65,損害程度為弱～中等；階段Ⅱ的損害指數(shù)為0.81-0.98,損害程度為強～極強。 討論了壓裂液致頁巖中氣體擴散能力損害的預(yù)防和控制措施。壓裂液配方優(yōu)化、氮氣伴注等工藝等能從減弱壓裂液自吸,促進返排等方面弱化壓裂液對氣體擴散能力的損害；非水基壓裂和高溫熱處理等則能以另一種技術(shù)思路抑制壓裂過程中的水相圈閉等儲層損害,且具有在更小尺度上改善氣體在頁巖基塊中擴散傳質(zhì)能力的作用。
[Abstract]:Shale gas reservoir belongs to source rock gas reservoir, which contains a large amount of adsorbed gas, large pore size span, organic pore, inorganic pore and micro-fracture, which constitute a very complicated shale gas reservoir and flow space. Thus, shale gas production is a multi-scale mass transfer process involving the understanding of absorption, diffusion and seepage. Gas diffusion in shale block is the intermediate part of this process. It is very important to study the gas diffusion behavior for understanding the mechanism of shale gas production. At the same time, it is necessary to study the potential damage of fracturing fluid to the gas diffusion ability of shale because of the low rate of back discharge and serious retention of fracturing fluid after hydraulic fracturing in shale gas wells. Taking the downhole shale of Silurian Longmaxi formation in Sichuan Basin as the research object and taking the experimental description of gas diffusion capacity in shale as the core, a diffusion behavior characterization model in accordance with the process of shale gas production is established, and the experimental test method of diffusion coefficient is designed. The variation of methane diffusion coefficient in rock samples before and after self-suction damage of fracturing fluid is analyzed, and the damage evaluation index and preventive measures are given. The analysis shows that the mineral composition of the downhole shales of Longmaxi formation is quartz, feldspar and clay minerals. The average porosity of rock samples is 3.45 and the average permeability is 0.056 mD. The pore diameter of the reservoir is mainly distributed in 3 ~ 100nm, and the pore size less than 10nm controls 50 to 80% of the pore space. The diffusion type and diffusion stage of gas in shale are defined. According to the classical Kn number gas flow state classification standard, the gas diffusion in shale block is dominated by Knudsen diffusion. Furthermore, the diffusion process can be divided into three stages: Knudsen diffusion, nano-pore gas diffusion and gas concentration diffusion to the interior of kerogen. The contribution of KKnudsen diffusion to gas detachment in shale is analyzed. The Knudsen diffusion equivalent permeability model is derived, and the reliability of the model is verified by the experimental data of methane percolation at low speed. The contribution of KKnudsen diffusion to the whole mass transfer process is quantitatively described by introducing the gas permeability correction coefficient F. With the decrease of methane pressure and pore diameter, the larger the value of F can be from slightly greater than 1 to more than 10, the larger the contribution of Knudsen diffusion is. An experimental test and damage evaluation method for methane diffusion coefficient based on gas pressure attenuation is established. According to the experimental data of 9 groups, the diffusion coefficient of methane in phase I (nano-pore gas diffusion) was 3.78 脳 10 ~ (-13) (7.04 脳 10 ~ (-13) cm ~ (2) / s, and that in stage 鈪，

本文編號：1825221