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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/79683


    Title: 以離散元素法模擬苗栗出磺坑地區構造演育與裂隙分布評估;Study of Structural Evolution and Fracture Distribution through Distinct Element Method in Chuhuangkeng Area, Miaoli
    Authors: 陳彥如;Chen, Yen-Ju
    Contributors: 應用地質研究所
    Keywords: 出磺坑背斜;離散元素法;構造演育;Chuhuangkeng anticline;Distinct element method;Structural evolution
    Date: 2019-01-03
    Issue Date: 2019-04-02 15:13:28 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 苗栗地區由東至西三個並列之背斜構造分別為八卦力構造、出磺坑背斜及錦水背斜。其中出磺坑背斜及錦水背斜已生產大量的天然氣以及凝結油,台灣中油公司推測八卦力構造亦有產油潛能。然而,八卦力構造位於內麓山帶,難以進行地物探勘及野外調查工作,在地質資料甚為缺乏的狀況下,無法直接評估其產油氣的潛能。油氣的探勘之故,過去已於出磺坑背斜區域,累積豐富地下地質資料及密集的地質構造剖面,本研究藉此優勢,進行本區之構造分析,以出磺坑背斜為檢核標的,進而針對八卦力地區地質構造的形成機制及裂隙分布的情形進行評估。其中以軟體─Move檢核所繪製剖面之合理性,同時帶入力學分層之觀念修繪此構造剖面,及以數值分析方法─顆粒流程式(Particle Flow Code, PFC),模擬出磺坑背斜與八卦力構造,進而分析裂隙之分布,並推算目標儲集層之孔隙率。
    研究結果顯示,苗栗西部麓山帶之向斜與背斜構造特徵與拱彎作用產生的褶皺特徵相符,可依此機制以數值模擬的方式模擬其形貌。透過彙整五指山層至卓蘭層地層柱,本研究依各地層岩性組成與力學特性將地層重新劃分為由老至年輕A、B、C、D、E、F、G及H層,共8個力學層。根據複層褶皺理論中,褶皺軸部軟硬層形貌特徵對地質構造剖面進行修繪。研究結果顯示,硬層強度分別為軟層強度之25倍與50倍且水平應變量達38%時,可成功模擬出八卦力構造與出磺坑背斜之構造形貌,同時顯示區域內之裂隙生成與水平應變量值呈正相關。根據不同硬軟層強度比進行模擬結果顯示,當硬層強度為軟層強度之25倍時,裂隙集中發育於錦水背斜西翼與八卦力構造西翼,於出磺坑背斜兩翼亦有零星裂隙發育,出磺坑背斜東翼孔隙率高於西翼,東翼木山層孔隙率達4.7~4.9%;八卦力構造區域,八卦力構造西翼孔隙率高於東翼,西翼木山層孔隙率達4.3~9.9%。當硬層強度為軟層強度之50倍時,裂隙發育於八卦力構造之西翼、軸部A層與出磺坑背斜背斜兩翼,且東翼裂隙較為密集,出磺坑背斜東翼孔隙率高於西翼,東翼木山層孔隙率達6.0~7.1%;八卦力構造區域,八卦力構造西翼孔隙率高於東翼,西翼木山層孔隙率達4.8~9.6%。將數值模擬中孔隙率分析結果與岩心孔隙率進行比較顯示二維模擬計算出之孔隙率皆小於岩心試驗與NMR試驗得到之孔隙率。
    ;The main oil and gas production structure is a series of parallel anticlines in NNE-SSW orientation in western foothills. Chinshui and Chuhuangkeng anticlines are the most productive structures among them. The CPC (Chinese Petroleum Corporation) surmises that Pakuali structure, which is east of Chuhuangkeng anticline, could also have the potential to be a production structure. Nevertheless, it is inefficient to carry out geophysical exploration and field investigation in the inner western foothills where Pakuali structure is located. Taking advantage of the abundant surface and subsurface geological data of anticlines west of the Pakuali structure, it is legitimate to reason the tectonic characteristics and structural evolution of Chuhuangkeng-Pakuali area. The aim of this study is to construct a geological cross-section which can be balanced kinematically and simulated mechanically by MOVE commercial software and PFC2D simulation software, respectively. Furthermore, fracture distribution analysis and porosity assessment are performed based on the simulation results.
    Based on my cross-section, the structural characteristics of crustal folds in the western foothills in Miaoli are similar to the folds produced by the mechanism of buckling. Accordingly, the numerical simulation of this study are founded on the buckling mechanism. The stratigraphic assemblage of the oldest Wuchishan Formation to Cholan Formation are collated and divided into eight structural lithic units, re-named as layer A to H, based on the difference of lithology and mechanical properties. According to the theory of multi-layer folding, the geological cross-section is modified as lobate and cuspate shapes for the contacts of the soft and hard layers at the fold axis, and the structural section is then used as a reference for the successful simulation of the Chuhuangkeng anticline and the Pakuali structure.
    The results show that when the hard layer strength is 25 times and 50 times greater than the soft layer strength and the horizontal shortening is 38%, the structural configuration of the Pakuali structure and the Chuhuangkeng anticline can be successfully simulated. For the case of layer strength ratio of 25 times, the cracks are concentrated in the western limb of the Chinshui anticline and the western limb of the Pakuali structure. There are also sporadic cracks in the both limb of the Chuhuangkeng anticline. The porosity of the eastern limb of the Chuhuangkeng anticline is higher than that of the western limb, and the porosity of the B layer in the eastern limb is about 4.7 to 4.9%. The porosity of the west limb of the Pakuali structure is higher than that of the east limb, and the porosity of the B layer in the west limb is about 8.8 to 9.6%. For the case of layer strength ratio of 50 times, cracks develop in the western limb of the Pakuali structure, both limbs of the Chuhuangkeng anticline and the cores of two structures at the A layer. The porosity of B layer at the eastern limb of the Chuhuangkeng anticline is about 6.0 to 7.1% while the porosity of B layer at the western limb of Pakuali structure is about 4.8 to 9.6%. Comparing the values of porosity from the numerical simulation with the values of porosity from the tests, the porosity values derived from the two-dimensional simulation are, in general, few percentages less than the porosity values obtained from the core test and the NMR test.
    Appears in Collections:[應用地質研究所] 博碩士論文

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