鹽水層碳封存盆地模擬研究 - 以澳洲西北海域 Roebuck盆地為例

Abstract

隨著溫室效應加劇，尋找合適的地質封存場址已成為全球關注焦點。鑒於澳洲碳封存政策開放及我國於澳洲礦區取得探勘權之現況，本研究針對澳洲 Roebuck 盆地進行鹽水層碳封存之模擬研究。透過鄰近盆地的儲集層類比，選定中侏羅紀三角洲沉積之 Depuch Formation 為儲集層，其中南側 Bedout 次盆地具理想封存深度，並由早白堊紀泥岩層作為區域性蓋層。 由於缺乏足夠的岩石物理資料，本研究將 Depuch Formation 細分為 20 個子層，利用七條二維地質剖面透過 PetroMod 進行盆地模擬。預測結果顯示，扣除深度大於 3200 公尺區域後，儲層平均厚度為 442.4 m、平均孔隙率 22.6 %、平均溫度 72.7 ℃、平均壓力 21.1 MPa。在儲存效率因子 2 % (P50) 的假設下，估算最終儲存資源量達 361.3 億噸。 在注入模擬方面，針對 JN87-20 剖面之儲層進行單井注入情境分析，結果顯示在每年注入 25 萬、50 萬及 100 萬噸二氧化碳且持續 50 年的情境下，超壓及羽流最終均未觸及儲層頂部。然而，當年注入量達 100 萬噸時，局部壓力增加可能導致岩石破裂，進而影響儲層穩定性，且大部分二氧化碳仍處於自由態，危險性較高，此結果可能與模擬的滲透率結果有關，推估每年 50 萬噸為目前該模型之安全極限。另外，雙井模擬結果證實井距越近壓力疊加效應越顯著，當井距達 15 公里以上時方能有效降低壓力干擾。 本研究以初步探勘資訊建立模型，尚可透過探勘資料來持續調整模型獲得更符合實際狀況的結果。將碳封存模擬應用至台灣碳封存開發中，會面臨到地質條件更加複雜的狀況，應針對地質探勘要有更深入的了解以作為建立及校正模型的參數設定。

As global warming intensifies, identifying suitable geological storage sites has become a global priority. Given Australia's proactive carbon storage policies and Taiwan's acquisition of exploration rights in Australian mining areas, this study conducts a simulation of saline aquifer carbon sequestration in the Roebuck Basin, Australia. Through reservoir analogy with adjacent basins, the Middle Jurassic deltaic Depuch Formation was selected as the target reservoir. The Bedout Sub-basin in the south provides ideal storage depth, while Early Cretaceous mudstone layers serve as regional seals. Due to limited petrophysical data, the Depuch Formation was subdivided into 20 sub-layers, and basin modeling was performed using PetroMod across seven 2D geological sections. Results indicate that after excluding areas deeper than 3200 m, the predicted average reservoir thickness is 442.4 m, with an average porosity of 22.6%, temperature of 72.7°C, and pressure of 21.1 MPa. Assuming a storage efficiency factor (E) of 2% (P50), the total storage resource is estimated at 36.13 billion tonnes. Regarding injection simulation, single-well scenarios were analyzed for the JN87-20 section. Results show that after injecting 250,000, 500,000, and 1,000,000 tonnes of CO2 per year for 50 years, the overpressure and plumes did not reach the top of the seal. However, at an annual rate of 1,000,000 tonnes, localized pressure increases could lead to rock fracturing, potentially compromising reservoir stability. Furthermore, as most CO2 remains in a free state, posing higher risks potentially linked to simulated permeability, 500,000 tonnes per year is estimated as the safety limit for this model. Additionally, dual-well simulations confirm that closer well spacing intensifies pressure interference; a minimum spacing of 15 km is required to effectively mitigate these effects. This study demonstrates the feasibility of establishing models using preliminary exploration data, which can be continuously refined as further data becomes available. Applying carbon sequestration simulations to Taiwan’s development involves navigating more complex geological conditions. Consequently, a deeper understanding of geological exploration is essential to provide accurate parameters for model construction and calibration.