發(fā)布時間：2018-01-30 23:21

  本文關鍵詞： 油頁巖 熱損傷 CT SEM 分形理論 力學性能 損傷模型 二次開發(fā)　出處：《吉林大學》2015年博士論文　論文類型：學位論文

【摘要】：油頁巖資源豐富，全世界油頁巖資源折算成頁巖油高達4000億t以上，是天然原油探明可采儲量的3倍左右。我國油頁巖資源預測儲量高達7199億t，排在全世界第四位，折算成頁巖油資源為476億t。由于經濟與人口的快速增長，能源需求正在急劇增加，而常規(guī)油氣資源卻在日益減少，在能源危機的背景下，油頁巖資源以其巨大的資源儲量以及光明的開發(fā)前景，得到越來越多的關注。 在油頁巖的開采方式中，原位開采技術雖然開始較晚，但是發(fā)展較快，目前已經有十幾種之多，核心都是通過對地下油頁巖儲層進行加熱，使油頁巖中的干酪根熱解產生油氣。對油頁巖層進行加熱，就必然會導致其出現熱損傷現象，力學性質產生劣化。由于油頁巖層處在地下一定深度，受到較為復雜的地應力作用，當熱損傷出現時，就可能導致油頁巖層出現較大變形甚至是破壞，對安全生產產生不利影響。因此，有必要對油頁巖的熱損傷過程展開研究，增加對油頁巖熱損傷劣化特性的認識。本研究結果可用于油頁巖原位開采過程中預測可能出現的地表沉降，防范可能出現的不利情況等方面，具有一定的理論意義和實際應用價值。 本研究選取吉林農安油頁巖作為研究對象，首先應用熱重分析儀測得油頁巖試樣的熱解失重曲線，通過對油頁巖試樣的熱解失重規(guī)律進行分析，確定了所要研究的溫度區(qū)間為常溫到700℃，在此區(qū)間內，選擇了8個溫度水平進行試驗，8個溫度水平分別為25℃（常溫）、100℃、200℃、300℃、400℃、500℃、600℃、700℃。 按照確定的溫度水平對油頁巖試樣進行加熱，然后分別采用CT掃描以及SEM技術測得不同溫度油頁巖試樣的細觀結構圖像。通過測得圖像對試樣孔隙、裂隙以及礦物顆粒的形態(tài)特征進行定性分析和定量計算，分析溫度作用下油頁巖試樣的損傷演化特性，在此過程中得到如下結論：隨著溫度的升高，油頁巖中的礦物發(fā)生了較大變化，礦物的數量出現減少，礦物形狀發(fā)生改變且尺寸在變�。慌c此同時，油頁巖中較大孔隙的數量在增加，其形狀也由長條形向橢圓形轉化，定向性逐漸明顯。這些變化都使得油頁巖內部的熱損傷逐漸加劇，力學性能逐漸劣化。應用數字圖像盒維數算法對不同溫度油頁巖的CT圖像以及SEM圖像進行分形分析，發(fā)現在25-700℃之間，分形維數D隨溫度升高呈現出先增大后減小的變化趨勢，并在400℃時達到最大值，說明400℃時油頁巖內部的孔隙形態(tài)最為復雜。 對加熱到不同溫度水平的油頁巖試樣進行物理力學性能測試，結合縱波波速、彈性模量、峰值強度等參數對油頁巖在溫度作用下的宏觀損傷劣化特性進行分析，研究發(fā)現：在溫度作用下，縱波波速和彈性模量出現了持續(xù)的下降，而峰值強度出現了先增大后減小的變化趨勢，并在400℃達到最大值，400℃是油頁巖宏觀力學性能發(fā)生改變的特殊溫度節(jié)點。分別根據縱波波速以及彈性模量定義了損傷變量，研究發(fā)現：損傷變量隨溫度升高而逐漸增大，兩者正相關。700℃時損傷變量最大，，兩種方法計算的損傷變量值分別為0.936和0.785，比較真實的反應了油頁巖的損傷情況。 最后，在實測試驗數據的基礎上，結合巖石損傷理論，推導出了針對油頁巖的熱損傷本構方程，然后應用Flac3D軟件進行二次開發(fā)，在軟件中自定義出考慮熱損傷的油頁巖本構模型（OsTd模型），并通過與單軸壓縮試驗的結果進行比較，驗證了OsTd模型的正確性。
[Abstract]:Oil shale is rich in resources, the world oil shale resources converted into shale oil up to more than 400 billion T, is a natural crude oil proven recoverable reserves of about 3 times. China's oil shale resources forecast reserves of up to 719 billion 900 million T, ranked in the world fourth, converted into shale oil resources for the 47 billion 600 million T. due to the rapid growth of economy and population, energy demand is increasing rapidly, while the conventional oil and gas resources are dwindling, in the context of the energy crisis, the oil shale resources to reserves its huge resources and a bright development prospect, has gained more and more attention.
In the oil shale mining method, in situ mining technology although started late, but rapid development, currently has more than a dozen, the core is through the heating of the underground oil shale reservoir, the pyrolysis of kerogen in oil shale to produce oil and gas. The oil shale layer is heated, it will inevitably lead to the the thermal damage phenomenon, caused deterioration of mechanical properties. The oil shale layer in certain depth underground, under stress is complex, when thermal damage occurs, it may cause the oil shale strata appear larger deformation or even destruction of production safety is adversely affected. Therefore, it is necessary to study the thermal damage process of oil shale the increase in understanding degradation characteristics of oil shale thermal injury. The results of this study can be used for surface subsidence prediction may occur in oil shale in the mining process, prevent the possible unfavorable situation. It has a certain theoretical significance and practical application value.
This study selected Jilin Nong'an oil shale pyrolysis as the research object, firstly the measured oil shale samples using TGA curves of weight loss, through the pyrolysis of oil shale samples were analyzed to determine the weight loss, the temperature range of the research is at room temperature to 700 DEG C, in this range, select 8 temperature level test, 8 temperature levels were 25 DEG C (normal temperature), 100 C, 200 c, 300 C, 400 C, 500 C, 600 C, 700 C.
Heating of the oil shale samples to determine the level of temperature, then using CT scanning and SEM technology of oil shale samples measured at different temperature. The microscopic structure of image obtained by the image on the porosity of samples, morphology of fracture and mineral particles by qualitative analysis and quantitative calculation, analyze the evolution characteristics of oil shale sample damage the effect of temperature, get the following conclusion: in this process, with the increase of temperature, changes in oil shale mineral, mineral quantity decreased, the change of the shape and size of minerals in smaller; and at the same time, the number of oil shale in the larger pores increase in its shape from strip to oval the transformation, directional gradually obvious. These changes make the thermal damage of oil shale inside gradually increased, gradually deterioration of mechanical properties. The application of digital image box dimension algorithm for different temperature The fractal analysis of CT images and SEM images of oil shale revealed that the fractal dimension D showed a trend of increasing first and then decreasing with increasing temperature at 25-700 D, reaching the maximum at 400 C, indicating that the pore morphology of oil shale is the most complex.
The physical mechanical performance test of oil shale samples with different temperature levels of heating, combined with the longitudinal wave velocity, elastic modulus, peak strength parameter analysis of oil shale under temperature macro damage deterioration found in temperature, the longitudinal wave velocity and elastic modulus has decreased continuously, and the peak intensity appeared first increased and then decreased, and reached a maximum value at 400 C, 400 C is a special node temperature of oil shale macro mechanical properties changes. According to the longitudinal wave velocity and elastic modulus of the damage variable is defined, the research found that the damage variable gradually increases with increasing temperature, a positive correlation between.700 DEG C when the maximum damage variable, damage variable values computed by two methods were 0.936 and 0.785, compared to the real response to the damage of oil shale.
Finally, based on experimental data, combined with the rock damage theory, deduced the damage constitutive equation for oil shale, then two times the development of application of Flac3D software in the software custom considering the thermal damage of the oil shale constitutive model (OsTd model), and compared with the results of compression tests the single axis, the OsTd model is verified.

【學位授予單位】：吉林大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TE662

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