本研究探討岩性與孔隙組織在不同壓力環境下對砂岩彈性行為的影響。使用孔隙率較高（約14-17 %）之澳洲砂岩與孔隙率較低（約5-10 %）的山東砂岩作為研究對象。兩種岩樣皆具有明顯紋理組織，其中山東砂岩又可區分出均勻無紋理區域與明暗分層條帶組成的紋理區域。透過薄片觀察及配合拉曼光譜與X光粉末繞射鑑定，分析砂岩主要組成礦物、顆粒大小與其組織結構。再以X光電腦斷層掃描（XCT）建構岩石中孔隙幾何形狀及三維空間分布關係，並估計岩體之孔隙率。同時利用吸滲法（imbibitions method）與氦氣高壓孔隙儀（Helium Porosimeter）分別量測常壓與高壓下的孔隙率。岩體波速（VP、VS）以超聲波方法量測，同樣分為常壓與高壓實驗，並比較經高壓與未經高壓樣品之差異。
　　本研究使用XCT技術分析砂岩樣品的孔徑大小、孔隙幾何形狀並與速度量測結果進行討論。本研究樣品孔隙幾何形狀上可被分辨的主要來自孔徑大於0.02 mm的孔洞，並為雙峰式分布（bimodal distribution），主要為α=0.5與1兩群。兩岩樣之常壓下速度與孔隙率呈反比關係。澳洲砂岩孔隙率分布較分散但速度分布較集中；山東砂岩無紋理樣品孔隙率與速度分布都很分散；山東砂岩紋理樣品的孔隙率則集中在約8 %。而在VP、VS部分，實驗樣品的整體呈線性分布，並與前人研究的分布趨勢相符合，其中澳洲砂岩分布在高VP、VS的區域，山東砂岩則在低VP、VS的區域。非均向性質則以山東砂岩紋理樣品最為明顯（>10 %），其非均向性主要受孔隙密度的疏密分布所影響。
　　高壓孔隙率實驗中在約30 MPa以內，所有樣品皆觀察到孔隙率明顯的變化，但持續加壓至實驗最大壓力150 MPa，孔隙率與常壓下相比僅相差2-3 %。高壓超聲波實驗選用常壓下的速度皆相近之岩樣，當加壓至最高壓力時山東砂岩的速度明顯高於澳洲砂岩，但相差不超過5 %，雖然澳洲砂岩的起始孔隙率約為山東砂岩的兩倍。經由高壓速度測量中觀察得知，無紋理的樣品（澳洲砂岩、山東砂岩無紋理樣品），經高壓實驗後僅改變平均速度，而對其速度非均向性質則改變不明顯。但在有紋理的樣品內（山東砂岩紋理樣品），由剪力波的速度變化顯示平均速度與速度非均向性皆有明顯改變，此現象應該與不同方向的孔隙閉合有關。

　　Depositional environments and tectonic activities determine the overall reservoir properties of sandstones, which have been reflected from the seismic data. It has been long recognized that the seismic velocity is sensitive to critical reservoir parameters, such as lithofacies, porosity, pore fluids and pore pressure.
　　In this study, laboratory measurements of elastic waves （Vp and Vs） and porosity at ambient conditions and under confining pressures up to 150 MPa were carried out on two different sandstones: Australia sandstone （AS） with higher porosity （14-17%） and Shandong sandstone （SDS） with lower values （5-10%）. Three sets of rock specimens were cored from AS （non-textured） and SDS （non-bedding and bedding texture）. The mineral phases in the sandstone were analyzed using Raman spectroscopy and X-ray diffraction. The lithological description of studied sandstones were provided by the observations of thin sections using optical microscopy. Moreover, the X-ray Computed Tomography （XCT） technique was employed to characterize the geometry of pores and their distribution in 3-D that helps to estimate the porosity of studied sandstones. Furthermore, the porosity of sample was measured using imbibitions method at ambient conditions and helium porosimeter at high pressure （up to 150 MPa）.
　　At ambient conditions, the XCT analysis showed that these three tested rocks all possessed large proportion of micropore which size is smaller than 20 microns, and the aspect ratio of pores showed strong bimodal distribution （α=0.5 and 1）. The porosity and velocity measurements in these three sets of specimens showed that compared with the non-textured specimens between AS and SDS, the porosity for both specimens exhibits a wide range distribution but AS measured velocity showed scattering within narrow range, and opposite trends in SDS. The measured P and S wave velocities of this set specimens presented a linear function, the velocity varying from 3.20 km/s to 4.26 km/s for P wave and 2.08 km/s to 2.83 km/s for S wave, yielding a value of 1.5-1.7 for Vp/Vs ratio.
　　At high pressure experiments, the porosity measurements in three types of specimens studied here presented markedly decreasing at lower pressure range （< 30 MPa）. The amount of porosity decrease in those specimens was about < 3% when reaching the peak pressure （150 MPa）. The high pressure velocity measurements were performed on the selected specimens from three different sets of rocks, which the bench-top velocity started with similar values but with low- and high-porosity. Although the porosity of AS is two times of SDS, the measured velocity at peak pressure condition （150 MPa） showed that the lower porosity specimens from SDS have slightly higher values compared with those of AS, but only less than 5% higher.
　　Basically, the changing of velocity of porous rock is due to the variation of porosity and pore features. The obtained results suggested that non-bedding samples （i.e., AS and SDS non-textured samples） only changed average velocity after high pressure experiments. The bedding samples （i.e., SDS textured samples） not only changed average velocity but also velocity anisotropy.

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