台灣西南海域永安海脊天然氣水合物好景區降壓生產模擬研究

Depressurization on Gas Production from Gas Hydrate Prospect on Yuan-An Ridge Offshore Southwest Taiwan

吳政岳(C.Y. Wu) ； 謝秉志(B.Z. Hsieh)

《鑛冶：中國鑛冶工程學會會刊》 60卷4期 (2016/12) Pp. 46-61

https://doi.org/10.30069/MM.201612_60(4).0005

摘要

天然氣水合物是低溫高壓時所存在的固態晶體，是由天然氣被水的結晶體包覆而存在的能源礦物。近年來的調查指出，台灣西南海域存在適合天然氣水合物的生成環境。由於台灣的能源主要仰賴進口，若能有效地開採西南海域的水合物資源，對於台灣的能源自主將有莫大的助益。本研究的目的是利用降壓生產開採法，進行天然氣水合物的生產開發數值模擬，本研究結果可提供未來天然氣水合物礦區開採時參考。本研究以台灣西南海域永安海脊的天然氣水合物好景區作為研究標的，設定不同的生產操作條件來模擬評估水合物礦區的開採效益。研究結果顯示，在生產井井底壓力固定為9MPa、5MPa與3MPa時（地層的初始壓力為16.4MPa），天然氣採收率為0.26%、49.45%及74.04%，而水合物的熔解百分比為，10.26%、63.84%及86.94%。本研究也針對不同地層滲透率與水平垂直滲透率比進行敏感度分析，由結果指出，地層滲透率越低，水合物的熔解效益越差，採收率也較差，而水平-垂直滲透率比對水合物的熔解影響較小，在本研究中相對滲透率曲線中之不可移棲氣體飽和度越高會使水合物的產收率較差。

關鍵字

非傳統油氣 ； 敏感度分析 ； 數值模擬

並列摘要

Gas hydrate are consist of methane and water mixtures, which are newly energy sources, and are crystalline, formed at high pressure and low temperature conditions. The latest investigation shows that, there is a suitable environment in offshore southwest Taiwan for gas hydrate exist. As the energy demand in Taiwan is depend on imported energy, with the development of hydrate resources offshore southwest Taiwan may improve the energy independence situation. The purpose of this study is to use numerical simulation to estimate the gas production from a gas hydrate deposit by depressurization method. The results of this study are able to be a reference for the future field development. The study target is set to a gas hydrate prospect on Yuan-An ridge offshore southwest Taiwan. In this study, different production operating conditions are set to evaluate the production efficiency. As the results shows, when the well bottomhole pressure is dropping from 16.4MPa to 9MPa, 5MPa or 3MPa, the recovery factor is 0.26%, 49.45% or 70.04%. The hydrate decomposition ratio is 10.26%, 63.84% or 86.94%. The sensitivity analysis results shows, the lower permeability leads to a smaller recovery factor. The permeability ratio in this study has little influence on gas recovery. The higher irreducible gas saturation will cause a smaller recovery factor.

並列關鍵字

Unconventional gas ； Sensitivity analysis ； Numerical Simulation