苗栗地區儲集層孔隙率與滲透率特性評估

Evaluation characteristics of porosity and permeability of reservoir rocks over Miaoli area

王玲絲(Ling-Sui Wang)

指導教授 ： 蔡龍珆

國立中央大學/地球科學學院/應用地質研究所/碩士(2012年)

摘要

為達成二氧化碳地質封存的目標，儲集岩層不僅需要適當之地質構造、地層深度及厚度等條件，岩層的孔隙率與滲透率亦為重要之評估因素。本研究採集苗栗地區北寮砂岩、觀音山砂岩、東坑層、上福基砂岩、關刀山砂岩、魚藤坪砂岩及卓蘭層砂岩為樣本，以孔隙率/滲透率儀測量不同圍壓下之孔隙率與滲透率，利用岩石光薄片分析礦物組成及顆粒組織，並配合掃描式電子顯微鏡觀察孔隙結構，探討砂岩層孔隙率與滲透率之影響因素，作為二氧化碳地質封存之評估參考。分析結果以上福基砂岩之礦物組成以石英所佔比例最高、平均粒徑最大且顆粒間之孔隙亦較大，具最高孔隙率及滲透率，圍壓5MPa下孔隙率20.8%、滲透率3.0E-13m2。東坑層的淘選度較上福基砂岩好，但平均粒徑較小，因此孔隙率及滲透率居次，圍壓5MPa下孔隙率14.8%、滲透率3.4E-15m2。整體而言，儲集岩層孔隙率與滲透率除了受埋藏深度之壓密應力影響，也受礦物組成、顆粒大小、淘選度及膠結、溶解等成岩作用所影響。埋藏深度愈深使有效應力愈大，孔隙率與滲透率亦隨之變小；礦物組成及顆粒大小、形狀、排列等則會影響孔隙的大小與連通性，進而影響孔隙率與滲透率。壓密作用及膠結作用使孔隙減少，溶解作用則使孔隙增加，在成岩作用不同階段中，原生孔隙及次生孔隙影響並控制岩層的孔隙率及滲透率。

關鍵字

岩象分析 ； 孔隙率 ； 滲透率 ； 儲集層

並列摘要

In order to achieve the goal for geological storage of CO2, important assessment factors for reservoir rocks include not only suitable geological structure, thickness and depth, but also high porosity and permeability. This study is aimed to determine porosity and permeability, mineral compositions and pore structures of reservoir sandstones by using porosity/permeability measurement, thin section and SEM analysis. Characteristics and influencing factors of porosity and permeability of reservoir sandstones in Miaoli area were studied, so as to evaluate their storage potential for CO2 sequestration. Samples from seven different sandstone formations in Miaoli area were collected, including Beiliao Sandstone, Kuanyinshan Sandstone, Tongkeng Formation, Shangfuchi Sandstone, Guandaoshan Sandstone, Yutengping Sandstone and Cholan Formation. According to the analytic results, Shangfuchi Sandstone exhibits the highest porosity (20.8%) and permeability (3.0E-13m2) under 5 MPa confining pressure as well as the largest quartz content, grain size and pore size. In addition, Tongkeng Formation stands the second place in porosity (14.8%) and permeability (3.4E-15m2) under 5 MPa confining pressure. Overall, porosity and permeability were influenced not only by burial depth, but also by mineral composition, grain fabric and diagenetic processes. Increased burial depth usually leads to increased compaction as well as decreased porosity and permeability. Furthermore, mineral composition, grain size, shape, and packing influence the connectivity and size of pores and fractures, and then the porosity and permeability. Compaction and cementation could reduce porosity and permeability, but dissolution could increase them. Primary and secondary porosity of reservoir rocks were affected during different stages of diagenetic processes.

並列關鍵字

petrographic analysis ； reservoir ； permeability ； porosity

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