Abstract
摘要:本計畫為執行中央地質調查所推動之4年期「天然氣水合物資源潛能調查:震測、地熱及地球化學調查」工作,以震測、地熱以及地球化學等探測技術及分析方法在台灣南部與西南海域進行天然氣水合物之調查與探勘研究,一以了解台灣南部過去未曾進行過天然氣水合物調查的海域中是否亦有天然氣水合物的資源潛能,二則以過去在台灣西南海域天然氣水合物調查的成果為基礎,在擇定的探勘好景區內進行天然氣水合物儲集層之資源特性調查。為達成計畫目標,本計畫結合了過去執行中央地質調查所天然氣水合物調查計畫中地球物理與地質、地球化學團隊成員,組成一堅強的調查分析團隊來執行此計畫。除了總計畫負責整個計畫之規劃、協調工作以及維護與擴充天然氣水合物資料庫外,另有8個分項計畫:
(1)反射震測與海底回聲剖面調查研究:本年度將在指標海脊探勘好景區收集一組仿3維震測資料以及在台灣南部海域普查區進行2維震測調查,沿測線並收集海底回聲剖面資料。此外,亦將整合分析長支距反射震測與仿3維資料來建立永安海脊與前緣海脊天然氣水合物儲集層的速度構造剖面。(2)海底地震儀對天然氣水合物研究的應用:本年度計畫目標是整合在永安海脊區域收集的海底地震儀震測資料(2004、2008、2009)及3維反射震測資料(2010),建立含天然氣水合沈積層的仿3維P波及S波速度構造、BSR深度與天然氣水合物飽和度分布,進而評估永安海脊區域天然氣水合物的資源量。(3)天然氣水合物賦存區流體移棲模式研究:本年度預計針對102與103年度收集來的前緣海脊仿3維震測區塊進行溫度場模擬討論。此外,也將納入102年度P-Cable震測系統所收集到3維震測資料,完成福爾摩沙海脊以及四方圈合海脊區域的溫度場模擬解釋。(4)天然氣水合物賦存區之地熱調查:本年度將在台灣南部2維震測普查區進行地熱量測,利用地溫梯度與地熱資料推估天然氣水合物穩定帶的深度,並探討天然氣水合物的分布情形。(5)天然氣水合物賦存區之地層構造與沈積特徵研究:本年度將分析解釋102年度在台灣南部海域2維震測普查區所收集來的反射震測資料,並針對擇定之探勘好景區建立天然氣水合物賦存模式。(6)台灣西南海域海水與沈積物之地球化學組成:本年度將於恆春海域102年度震測普查區進行系統普查工作,採集活塞沈積物與底水樣品;接著對岩心樣品進行岩性描述及基本物理性質分析;另進行沈積物與海洋底水之甲烷氣體分析,以瞭解該地區海床淺處甲烷氣體滲漏情形、及其氣體來源;以及對沈積物岩心樣品中之孔隙水進行地球化學成分分析,以瞭解流體組成、來源、及可能移棲方式。(7)台灣西南海域沈積物之磁學性質及年代研究:本年度將量測岩心沈積物的磁學性質、鑑定磁性礦物,期能有助於瞭解沈積物岩心樣品是否已受到與甲烷活動有關的還原作用;另對完整岩心樣品進行碳-14定年,以瞭解當地可能的沈積速率,有助於瞭解天然氣水合物的生成機制。(8)台灣西南海域沈積物自生礦物之電子顯微分析:本計畫擬針對臺灣西南海域MD178-10-3293岩心特定標本進行自生礦物高解析度電子顯微分析,特別著重鐵膨潤石之顯微岩象分析,以瞭解鐵膨潤石產狀、化學組成及其與硫化鐵礦物之生成關係和可能延伸之意義,特別是與天然氣水合物解離或冷泉活動之關聯性。本度計畫另將進行沈積物中硫化鐵礦物之電子背向散射繞射分析試驗。
Abstract: This proposal requests the 3rd year support of the 4-year gas hydrate project entitled “Investigation of Gas Hydrate Resource Potential: Seismic, Heat Flow and Geochemical Studies”. Seismic, heat flow and geochemical investigations will be carried out in the area offshore south and southwestern Taiwan with 2 purposes in mind: 1. To explore the areas where no gas hydrate investigation has been conducted before to see if there are gas hydrate energy potentials existed in those areas; 2. To investigate potential gas hydrate reservoir characteristics in the gas hydrate prospects delineated in the previous gas hydrate investigation projects of the Central Geological Survey (CGS). To achieve these goals, a team which consists of 10 scientists/researchers has been formed to carry out this project. The team members are experts in gas hydrate research and all have been involved in the previous gas hydrate investigation projects of CGS. Based on the needs of applying various investigation techniques and approaches, this project will be carried out by one master project and 8 sub-projects. The master project is responsible for the project planning and coordination among different sub-projects, also to maintain and continuous developments of the gas hydrate database. The 8 sub-projects and their respective roles in this project are described below: 1. Seismic reflection and chirp sonar investigations. This sub-project will collect both 2D and 3D seismic reflection data and underway chirp sonar data in the reconnaissance survey area offshore southern Taiwan and in the gas hydrate prospects off SW Taiwan. In addition, joint analyses of both large-offset seismic data and 3D seismic data will be performed to establish good velocity model along seismic profiles across the Yung-An Ridge and the Frontal Ridge gas hydrate prospects. 2. Ocean bottom seismometer investigation. This sub-project will analyze seismic data recorded by OBSs near the proposed gas hydrate drilling sites in the Yung-An Ridge prospect to derive both P- and S- wave velocity information of the substrata, and to extract other important geophysical properties of the substrata, such as the thickness and the amount of gas hydrate saturation of the hydrate-bearing substrata. 3. Fluid migration modeling of the gas hydrate provinces. This sub-project will build 3D fluid migration models for 3 gas hydrate prospects where 3D seismic data have been collected, using heat flow, seismic and bathymetry data. This modeling approach will help us to better understand the properties of possible gas hydrate reservoirs. 4. Heat flow investigation of the gas hydrate province. This sub-project will conduct heat flow measurements in the 2D seismic reconnaissance survey area offshore southern Taiwan. Geothermal data will be analyzed and interpreted to provide information regarding the gas hydrate stability zone and factors affecting geothermal structures, such as fluid flows and gas hydrates. 5. Stratigraphic analyses and sediment deposition characters of the gas hydrate prospects. This sub-project will interpret the 2D seismic data collected last year in the reconnaissance survey area offshore southern Taiwan, and to establish gas hydrate reservoir characteristics of the selected gas hydrate prospects. 6. Geochemical composition of sea water and sediments offshore SW Taiwan. This sub-project will collect and analyze the sea water and seafloor sediment samples to understand various geochemical characters of gases in the sub-strata, and to establish fluid migration models based on the observations and analysis results. 7. Magnetic properties, age and microfossils of the sediments offshore SW Taiwan. This sub-project will measure the magnetic susceptibility, hysteresis curve, identify magnetic minerals and forams, and determine the carbon-14 ages of cored sediments. 8. Electronic microscopic analyses of authigenic minerals in the sediments offshore SW Taiwan. This study will carry out a high-resolution electron microscope study for authigenic minerals, specifically ferric smectite found in selected specimens of long piston cores MD178-10-3293.
Overall, this project will continue to investigate and to better define the gas hydrate prospects in the area offshore SW Taiwan for energy resource potential evaluation, and to prepare for future drilling investigation. Also, this project will survey other areas offshore southern Taiwan to find new gas hydrate prospects.
Keyword(s)
天然氣水合物
台灣西南海域
反射震測
海底地震儀
合成震波
天然氣水合物飽和度
海底仿擬反射
3維熱流模擬
地溫梯度
地熱量測
地層構造
沈積環境
天然氣水合物賦存模式
硫酸鹽還原
自生性碳酸鹽
磁學
Gas hydrate
Offshore Southwestern Taiwan
Seismic exploration
Ocean Bottom Seismometer
Synthetic Seismogram
Gas hydrate saturation
Bottom simulation reflector
3-dimentional heat flow modeling
Geothermal gradient
Heat flow measurement
Stratigraphi