| 摘要: | 本研究顯示位於中部台灣的台西盆地中，晚期中新世至更新世的厚砂岩及頁岩，適合地下儲集二氧化碳。具有潛能的二氧化碳封存之儲集層及蓋層，由晚期中新世至更新世之桂竹林層、錦水頁岩及卓蘭層所組成，並出露在三義斷層上盤大甲溪河床。藉由野外露頭研究，可了解地層特徵，包含地層厚度與沉積物粒徑大小。研究結果指出，由關刀山砂岩段、十六分頁岩段及魚藤坪砂岩段所組成的桂竹林層，出露厚度約為319公尺，可成為良好的二氧化碳儲集層；錦水頁岩厚度約為187公尺，可成為良好地蓋層；而下部卓蘭層的厚度約為300公尺。
我們研究上述地層之礦物及化學組成，研究樣本包含桂竹林層32個、錦水頁岩12個以及卓蘭層10個。岩相分析的結果顯示，主要的二氧化碳儲集砂岩中，顆粒主要以石英（55-60%）、沉積岩岩屑（15-25%）及長石（5-7%）所組成，此外還有一些細粒基質礦物或膠結物（5-10%）。礦物X光繞射分析結果顯示，砂岩主要黏土礦物組成及其比例為伊萊石（30-70%）、綠泥石（20-40%）、高嶺石（20-30%）及混層黏土（0-10%）；在錦水頁岩中，主要的黏土礦物組成比例則為伊萊石（20-50%）、綠泥石（25-45%）、高嶺石（15-30%）及混層黏土（0-15%）。此外，藉由X光螢光分析所測量的微量元素結果顯示，岩石樣本中含非常微量（～206 ppm）的可溶性元素（Cu, Co, V, Cr, Sr, Ba, Pb），其總量可忽略不計；其中難以溶解於地層水中的元素（Cd, Zn, Se, Mo）之濃度則更低，介於2.5-110 ppm之間。
在桂竹林層中，許多層砂岩的厚度大於20公尺，並含有石英、沉積岩屑、長石及細粒基質礦物，為一套良好的二氧化碳儲集層。此儲集層被錦水頁岩所覆蓋，厚度沿大甲溪河床測量約為187公尺。下部卓蘭層的特徵為砂頁岩互層，單層的砂岩厚度達10-15公尺；夾層的頁岩厚度達3公尺，可做為多層蓋岩之二氧化碳封存系統。
;Studies show that a few Miocene to Pleistocene pairs of thick sandstone and shale formations of the Taihsi Basin in central Taiwan are suitable for implementing CO2 geosequestration. Potential CO2 reservoir and seal rocks of the Kueichulin Formation, Chinshui Shale and Cholan Formation of late Miocene to early Pleistocene in age are exposed in the hanging wall of the Sanyi Fault and along the Tachia River bed. We investigated the stratigraphic characteristics of the exposed formations, including bed thickness and grain size by establishing a stratigraphic and sedimentologic column on the hanging wall of the Sanyi Fault. Our results show that the Kueichulin Formation, consisting of Kuantaoshan Sandstone Member, Shihliufen Shale Member and Yutingping Sandstone Member, is floored by the Sanyi Fault and reaches ~319 m in thickness. The Chinshui Shale, considered as the main seal rock, is around 187 m thick while the measured lower part of the Cholan Formation is ~300 m in thickness.
We collected 32 samples from the Kueichulin Formation, 12 samples from the Chinshui Shale and 10 samples from the Cholan Formation to study their mineralogical and chemical compositions. Petrographic analyses reveal that the framework grains for the main CO2 reservoir sandstones consist predominantly of quartz (55-60%), sedimentary rock fragments (15-25%) and feldspar (5-7%) in addition to fine-grained matrix minerals or cement (5-10 %). X-Ray Diffraction (XRD) analyses show that predominant clay minerals in sandstones are illite (30-70%), chlorite (20-40%), kaolinite (20-30%) and mixed-layered clays (0-10%). The Chinshui Shale serves as the main seal rocks, whose clay minerals and abundance are as follows, illite (20-50%), chlorite (25-45%), kaolinite (15-30%) and mixed-layered clays (0-15%). Moreover, trace elements from X-Ray Fluorescence (XRF) results reveal that rock samples contain negligible total amount (~206 ppm) of dissolvable elements (Cu, Co, V, Cr, Sr, Ba, Pb). Elements that are not easily dissolved in the formation water, such as (Cd, Zn, Se, Mo) are even less with concentration ranging from 2.5-110 ppm.
Many individual sandstone beds of the Kueichulin Formation are more than 20 m in thickness and contain quartz, sedimentary rock fragments, feldspar and fine-grained matrix minerals, serving as good CO2 reservoirs. The reservoir layer is capped by the Chinshui Shale, a thick succession of seal rock, up to 187 m along the Tachia River. The lower Cholan Formation is characterized by interbedded sandstone and shale layers, with an individual sandstone bed up to 10-15 m thick and an individual shale bed up to 3 m thick, serving as a possible multi-sealing CO2 geosequestration system. |
