【摘要】：目前已有大量的宏觀實驗進行多孔介質(zhì)中壓敏效應的研究,但是壓敏效應的微觀機制仍較缺乏。多孔介質(zhì)的孔喉結構復雜,尤其是致密砂巖等非常規(guī)儲層,壓敏效應會導致相應的孔喉結構發(fā)生大幅度變化,因此對孔隙級多孔介質(zhì)的壓敏效應進行系統(tǒng)的研究有重要意義。本文基于可以真實描述巖石內(nèi)部結構特征的CT掃描技術,結合數(shù)字巖心和孔隙網(wǎng)絡模型理論進行分析,獲得有效應力變化與孔隙結構的變化關系;同時,建立了孔隙尺度上滲流場-應力場的流固耦合模型。在實驗方面,首先,本文建立了基于CT掃描法構建數(shù)字巖心的理論與方法。CT掃描獲得巖心的三維圖像,經(jīng)過濾波、二值分割處理得到數(shù)字巖心,提取孔隙網(wǎng)絡模型,分析巖心的幾何結構特征和拓撲結構特征,并進行流動模擬獲得絕對滲透率等參數(shù)。然后,基于人造砂巖形成了一套基于CT掃描的應力敏感實驗及分析方法。根據(jù)行業(yè)標準,在碳纖維巖心夾持器中進行應力敏感實驗,在不同壓力下對巖心進行CT掃描,構建不同應力下的數(shù)字巖心,進而提取不同應力下的孔隙網(wǎng)絡模型,研究相應的孔隙結構特征和滲流規(guī)律。最后,將該套方法應用到實際油田的中高滲砂巖和致密砂巖,進行不同類型砂巖的應力敏感實驗,并對兩種砂巖的應力敏感進行對比分析。在模擬方面,基于不可壓縮的N-S方程和Biot應力應變方程,構建了孔隙尺度上流固耦合數(shù)學模型,利用有限元方法進行了二維孔隙級流體流動計算,物理模型選用二維規(guī)則圓模型、二維不規(guī)則圓模型和實際SEM圖像模型,得到了滲透率和孔隙度隨圍壓以及流動壓差的變化規(guī)律。通過本文研究,形成了較為完整的基于CT實驗的應力敏感評價方法,對油氣田開發(fā)提高采收率具有重要應用價值。
[Abstract]:At present, a large number of macroscopic experiments have been carried out to study the pressure-sensitive effect in porous media, but the microscopic mechanism of the pressure-sensitive effect is still lacking. The pore throat structure of porous media is complex, especially in unconventional reservoirs such as tight sandstone, the pressure sensitivity effect will lead to the corresponding pore throat structure change greatly, so it is of great significance to systematically study the pressure sensitivity effect of porous media. Based on the CT scanning technique which can describe the internal structure of rock, the relationship between the effective stress change and the pore structure is obtained by combining the theory of digital core and pore network model. At the same time, the fluid-solid coupling model of percolation field and stress field on pore scale is established. In the aspect of experiment, firstly, the theory and method of constructing digital core based on CT scanning method are established. Three dimensional image of core is obtained by CT scan, digital core is obtained by filtering and binary segmentation, and pore network model is extracted. The geometric and topological characteristics of the core are analyzed, and the parameters such as absolute permeability are obtained by flow simulation. Then, a set of stress-sensitivity experiments and analysis methods based on CT scanning are developed based on artificial sandstone. According to the industry standard, stress sensitivity experiments were carried out in carbon fiber core gripper, and the core was scanned by CT under different pressures to construct digital core under different stress, and then the pore network model under different stress was extracted. The pore structure characteristics and percolation law are studied. Finally, the method is applied to the medium and high permeability sandstone and tight sandstone in actual oilfield, and the stress-sensitivity experiments of different types of sandstone are carried out, and the stress sensitivity of the two types of sandstone is compared and analyzed. In the aspect of simulation, based on the incompressible N-S equation and Biot stress-strain equation, the fluid-solid coupling mathematical model on pore scale is constructed, and the two-dimensional porous fluid flow is calculated by finite element method. The physical model consists of two dimensional regular circle model, two dimensional irregular circle model and actual SEM image model. The variation of permeability and porosity with confining pressure and flow pressure difference is obtained. Through the research in this paper, a relatively complete stress-sensitive evaluation method based on CT experiment has been developed, which has important application value in oil and gas field development and improving oil and gas recovery.
【學位授予單位】：中國石油大學(華東)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TE312

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本文編號：2331198