【摘要】：頁巖儲集層納米級孔喉直徑為5～200nm,滲透率為1×10-9～1×10-3μm2,與常規(guī)儲集層流體流動具有明顯不同,頁巖氣在頁巖中的流動不僅有滲流過程,還存在解吸、擴散、滑移流動,氣體在低滲透及致密氣藏孔隙喉道中流動規(guī)律也不適用于頁巖氣藏。為此,本文將針對頁巖氣儲層自生自儲和納微米孔隙尺度的特點,充分考慮多種流動機理,建立頁巖氣儲層多尺度流動模型,并在此基礎(chǔ)上形成頁巖氣儲層多級壓裂水平井非線性滲流理論。 本文針對頁巖氣儲層具有納微米級孔隙流動特點,采用連續(xù)介質(zhì)力學(xué)與分子運動學(xué)相結(jié)合的方法進行描述。根據(jù)努森數(shù)判斷流體的流態(tài),繪制了流態(tài)圖版,闡明了不同區(qū)域的流動機理和流態(tài)特征,計算分析了滲透率校正因子隨著努森數(shù)的變化關(guān)系。建立了考慮擴散、滑移特性的頁巖氣儲層多尺度流動模型,并結(jié)合頁巖滲流規(guī)律實驗,進行對比驗證。在此基礎(chǔ)上推導(dǎo)出考慮解吸、擴散和滑移作用的非線性流動方程。 考慮不同縫網(wǎng)形態(tài),運用保角變換及等值滲流阻力方法建立了考慮擴散、滑移及解吸吸附作用的基質(zhì)-裂縫耦合多尺度流動壓裂井產(chǎn)能方程,并對頁巖氣壓裂直井及多級壓裂水平井產(chǎn)能影響因素進行了分析。考慮解吸吸附隨壓力及時間變化,基于質(zhì)量守恒,建立了新的不穩(wěn)定控制方程。由于縫網(wǎng)區(qū)域和基質(zhì)區(qū)域滲透率等性質(zhì)差別較大,引入復(fù)合區(qū)模型,一區(qū)為裂縫-縫網(wǎng)區(qū),二區(qū)為基質(zhì)區(qū),建立模型并進行求解。建立了含連續(xù)微裂縫表面層基質(zhì)-裂縫雙重介質(zhì)球形模型,通過Laplace變換和Stehfest數(shù)值反演,求解得到了水平井井底流壓及壓裂水平井產(chǎn)量曲線。 數(shù)值計算結(jié)果表明：游離氣產(chǎn)量占總產(chǎn)氣量的85%-90%,對總產(chǎn)氣量貢獻較大。有機質(zhì)孔隙內(nèi)氣體解吸使頁巖氣井產(chǎn)量遞減減慢,解吸量越大,頁巖氣井產(chǎn)量越大,產(chǎn)量遞減越慢,并對生產(chǎn)中、后期氣體產(chǎn)能影響較大。通過對水平井縫網(wǎng)壓裂模型的計算,隨著產(chǎn)量的增加,地層壓力下降越快,基質(zhì)區(qū)的壓力波傳播邊界最大為縫網(wǎng)區(qū)外150m。產(chǎn)量呈現(xiàn)“L型”曲線,生產(chǎn)初期產(chǎn)量下降速度較快。該模型具有很強的理論及工程應(yīng)用性,為頁巖氣產(chǎn)能預(yù)測及開發(fā)指標優(yōu)化提供了理論依據(jù)。
[Abstract]:The pore throat diameter and permeability of shale reservoir are 5 ~ 200nm and 1 脳 10 ~ (-9) ~ (-1) 脳 10 ~ (-3) 渭 m ~ (2) respectively. The flow of shale gas in shale is different from that of conventional reservoir fluid. The flow of shale gas in shale has not only percolation process, but also desorption, diffusion and slip flow. Gas flow in the pore throat of low permeability and tight gas reservoirs is also not suitable for shale gas reservoirs. In this paper, according to the characteristics of self-generation self-reservoir and nanometer-pore scale of shale gas reservoir, the multi-scale flow model of shale gas reservoir is established by fully considering various flow mechanisms. On this basis, the nonlinear seepage theory of multistage fracturing horizontal well in shale gas reservoir is formed. In this paper, according to the characteristics of pore flow in shale gas reservoir with nanometer-order, the method of combining continuum mechanics with molecular kinematics is used to describe the reservoir. According to the Knudsen number, the flow pattern is drawn, the flow mechanism and characteristics in different regions are explained, and the relation between the permeability correction factor and the Knudsen number is calculated and analyzed. A multi-scale flow model of shale gas reservoir considering diffusion and slip characteristics was established and compared with the experimental results of shale percolation law. On this basis, a nonlinear flow equation considering desorption, diffusion and slip is derived. Considering different fracturing patterns, the productivity equations of matrix fracture coupled multi-scale fluid fracturing wells with diffusion, slippage and desorption adsorption are established by using conformal transformation and equivalent seepage resistance method. The factors affecting the productivity of the straight and multistage fracturing horizontal wells are analyzed. Considering the change of desorption adsorption with pressure and time, a new unstable governing equation is established based on mass conservation. Due to the great difference in permeability between the fracture network area and the matrix area, the composite zone model is introduced. The first zone is the fissure-fracture zone, the second zone is the matrix area, and the model is established and solved. A spherical model with continuous microfracture surface layer matrix and fracture is established. By Laplace transform and Stehfest numerical inversion, the bottom hole flow pressure and the production curve of fractured horizontal well are obtained. The numerical results show that the free gas output accounts for 85-90% of the total gas production and contributes greatly to the total gas production. The gas desorption in the pores of organic matter slows down the production of shale gas wells, and the larger the desorption amount, the larger the production of shale gas wells and the slower the decline of production, which has a great influence on the gas productivity in the later stage of production. Through the calculation of fracture pattern fracturing model of horizontal wells, with the increase of production rate, the formation pressure decreases more quickly, and the maximum pressure wave propagation boundary in the matrix area is 150 m outside the fracture net area. The yield showed "L type" curve, and the yield decreased rapidly at the beginning of production. The model has strong theory and engineering application, which provides theoretical basis for shale gas productivity prediction and development index optimization.
【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TE312

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