摘要：天然氣水合物(gas hydrate)是在低溫高壓的環境下由水分子組成似冰晶般的籠狀晶體架構，並將甲烷等氣體分子包裹於構造空隙中所成。因其中所含的氣體絕大部份是甲烷，常被稱為甲烷水合物（methane hydrate）。在自然界中甲烷水合物存在於低溫高壓的環境下，如極區永凍層及大陸斜坡處。由於其在常溫常壓下會解離產生水和天然氣，且其全球蘊藏量所含的天然氣中的有機碳量為目前已知全球化石燃料等能源有機碳總儲量之兩倍，已被視為二十一世紀最有希望的新能源。
在海域中辨識甲烷水合物的分布多根據震測剖面中所觀察到的海底仿擬反射（bottom simulating reflection, 簡稱BSR），台灣西南海域也發現有廣泛分布的海底仿擬反射(BSR)信號。計畫主持人目前正進行台灣西南海域BSR分布及特性檢視研究。初步結果顯示台灣西南海域不僅存在廣泛分布的海底仿擬反射(BSR)信號，且其分布向北延伸到水深八百多公尺處，離高雄市僅五十餘公里。如證實甲烷水合物儲量豐富，應有開發潛力。然在目前缺乏直接觀測及採樣的情況下，要估算甲烷水合物儲量，就只有仰賴地球物理資料了。近年來，利用震測速度分析來推估甲烷
Abstract: Naturally occurring gas hydrate is a solid, ice-like substance, composed of rigid cages of water molecules that enclose molecules of gas (clathrate). Since most of the gas hydrate contains methane molecule, it is often being call methane hydrate. Natural methane hydrates have been found in polar region and in submarine continental slopes (high pressure and low temperature environment). Due to the enormous amount of gas hydrate existed on earth, methane hydrate has been regarded as a potential energy resources. Taiwan lacks its own energy resources. However, geophysical data has indicated that gas hydrate is widely distributed underneath the sea floor offshore southwestern Taiwan. Recent compilation of the BSR distribution by the principal investigator of this proposal provides a basic framework for further investigation of gas hydrate's energy potential. In this proposal, we intend to establish techniques for gas hydrate quantity estimation from seismic velocity information. This is the most logical approach, as no direct observ tion or sampling has been conducted (due to the high cost of those investigations).
Two problems existed in deriving gas hydrate quantity from seismic velocity information. The first problem is how to obtain accurate velocity for the hydrate-bearing sediment and its surrounding sedimentary layers. The second problem is how to estimate the amount of gas hydrate in place based on velocity information alone. We will evaluate and select the most suitable seismic velocity analysis techniques to derive velocity structure of the gas hydrate-bearing sediment. More importantly, we will examine the physical properties of the gas hydrate-bearing sediments from Ocean Drilling Program (ODP) drilling results to derive the characteristics of the hydrate-bearing sediment in an accretionary wedge setting, then to formulate relationships between these characteristics and seismic velocities. This study will provide an economic way to evaluate the energy potential of the gas hydrate detected offshore southwestern Taiwan.
Seismic velocity analysis
Ocean Drilling Program
Bottom simulating reflection (BSR)
Offshore southwestern Taiwan