熱激勵法應用於第三型天然氣水合物儲集層之數值模擬研究

Numerical Study of Thermal Recovery on Class-3 Gas Hydrate Reservoir

黃奕鈞(Y. J. Huang) ； 吳政岳(C. Y. Wu) ； 張勛和(S. H. Chang) ； 謝秉志(B. Z. Hsieh)

《鑛冶：中國鑛冶工程學會會刊》 62卷4期 (2018/12) Pp. 27-41

https://doi.org/10.30069/MM.201812_62(4).0002

摘要

天然氣水合物的開採方法中，降壓法是目前公認最具潛力的生產方式，然而在高水合物飽和度的第三型水合物儲集層中，由於儲集層中可流動的物質（水）較少，可提供的壓力降有限，故降壓法的效率較差。而熱激勵法雖然在生產水合物時需要額外注熱，但是生產效益較不受壓力降影響。因此，本研究針對不同熱源供應，在第三型水合物儲集層中，運用熱激勵法探討水合物熔解行為及生產效率。本研究使用CMG公司開發的STARS模擬器進行研究，STARS具有耦合熱力學、多相流體流動、岩石力學與地球化學的能力。在本研究中，設計一對800公尺長的水平井在飽和度為70%的水合物地層中，利用不同熱源設計，包含：電子加熱器、蒸氣注入（300℃）、溫水注入（85℃），來進行生產模擬。模擬結果顯示，生產初期由於注入流體能直接貫入水合物區，因此流體注入法產氣量較高。但當注入流體前鋒貫穿至生產井，使得注入流體迅速產出，導致熱流在地層停滯時間縮短，降低熔解驅動力，最終氣產量較不樂觀。模擬計算出各種生產情境下的採收因子分別是：電子加熱器為32.22%、熱蒸氣注入法為14.2%以及溫水注入法為26.04%。

關鍵字

熱激勵法 ； 天然氣水合物 ； 非傳統天然氣

並列摘要

Among all of exploitation strategies, it is a general consensus that depressurization is the most potential recovery strategy. Nonetheless, depressurization is technically inefficient in the formation with high gas hydrate saturation having insufficient pressure drop due to the lack of mobile fluid (water) in the reservoir. Instead, the effect of pressure drop is relatively negligible in thermal recovery, though extra heat energy is supplied during production. Consequently, in this study different thermal stimulation methods were performed during simulations for examining melting behavior and production rate of gas hydrate. CMG STARS, which possesses capability of thermodynamic coupling, multiphase fluid flow, geochemical, and geomechanical calculation, is utilized for simulations. A pair of 800-meter-long horizontal wells with different heat resources injected, which include heater, 300℃ hot steam and 85℃ warm water, are designed separately in a formation with 70% of gas hydrate for simulations. According to results, high gas production appeared in cases with fluids injected into formations due to fluid influx. Nevertheless, when the fluid front penetrated the production well, it was produced rapidly resulting in insufficient time for hydrate fusion and leading to undesirable results. Based on different heat resource, the recovery factor of heater, hot steam and warm water are 33.22%, 14.2% and 26.04% separately.

並列關鍵字

Thermal Recovery ； Gas Hydrate ； Reservoir Simulation ； Unconventional gas