分散式光纖溫度感測器在地下水污染場址之高解析度井下水文地質調查(II)

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Project title

Translated Name/計畫中文名

分散式光纖溫度感測器在地下水污染場址之高解析度井下水文地質調查(II)

Project Coordinator/計畫主持人

Yung-Chia Chiu

Funding Organization/主管機關

Environmental Protection Administration

Department/Unit

Institute of Earth Sciences

Website

https://www.grb.gov.tw/search/planDetail?id=13372399

Year

2020

Start date/計畫起

01-01-2020

Expected Completion/計畫迄

31-12-2020

Bugetid/研究經費

1299千元

ResearchField/研究領域

地球科學

創新的分散式光纖溫度感測器（fiber-optic distributed temperature sensor, DTS）量測方法已被證明可適用於井下水文地質調查工作，憑藉著其在空間、時間上的高解析度量測，可對土壤及地下水污染場址在整治作業上提供高效能的調查與評估。本研究計畫於第一年度執行期間，在現地污染場址進行三次現地試驗。由第一次試驗可觀察到在監測期間因降雨事件，造成井下溫度急劇下降，藉由溫度回升的過程中可以判識不同深度地層的透水區段。以此概念為基準，第二次與第三次現地試驗針對監測井進行熱水注入試驗，藉由停止注水後溫度回復的過程判釋透水與不透水區段。此外，以地下水數值模式MODFLOW與MT3DMS模擬停止注水後溫度回復的過程，並藉由PEST率定模式參數，量化水文地質參數。根據DTS量測結果顯示，於注水井可觀察到在停止注水後，不同深度之溫度回復情況各不相同，藉由溫度回復速率可判釋透水區段。經由地下水數值模式與參數率定後之結果顯示，量測值與模擬值具有高度相關性，且誤差極小，量化後之水平向水力傳導係數具有一定之可信度。本研究計畫於第二年度將於現地污染場址進行主動式（active）DTS量測試驗，主動式DTS與被動式的感測器相同，皆須使用雷射脈衝分析儀主機與光纖，唯一的差異在於光纖的加熱控制系統（heating pulse controller, HPC），主動式DTS可藉由加熱控制系統對不同區段的光纖分別進行加熱，在不擾動自然地下水流的前提下，針對井內水體進行加熱，HPC的另一優勢在於針對地下水流流速較緩慢或溫度變化較不顯著之區段進行加熱，強化熱能傳輸的擴散情形，增加判識細小優勢水流路徑的能力，提昇井下透水區段的解析能力。第二年度的另一個工作項目為以線性熱源之熱傳輸解析解量化驗證主動式DTS試驗結果，並同時優化第一年度所建立的地下水數值模型，經由修改邊界條件設定與模式參數，使得模型能更真實反映現地情況。本研究計畫期透過兩年的研究成果，評估DTS在地下水汙染場址進行高解析度井下水文地質調查之可行性，提供污染場址改善與整治上一重要評估，同時，以此創新量測技術未來可提升水文地質調查能力。The innovative technique of fiber-optic distributed temperature sensor (DTS) has been approved to applicablely investigate downhole hydrogeological survey. It can provide a high efficient assessment of remediation in a groundwater contaminated sites by means of high resolution in space and time. In the first year, three field tests were conducted. In the first test, the rainfall events caused the large variation of temperature in the well and the permeable zone at different depths can be identified via different rates of temperature recovery. Accordingly, the injection of heated water into the wells was conducted in the second and third tests. After stopping injecting the hot water, the rates of temperature recovery at different depths in a single well were monitored and used to evaluate the permeabilities of the aquifers at each depth. Besides, the coupled numerical model of MODFLOW and MT3DMS was applied to simulate the process of heat transfer after ceasing injecting the hot water. The automatic parameter estimation software of PEST was used to calibrate the numerical model and the hydraulic conductivities were identified. The results show that, the permeable zone can be identified by temperature recovery after ceasing injecting the heated water. The simulated results showed that the simulated temperatures can match the observations well and the hydraulic conductivities can be quantiied. In the second year, the active-DTS will be applied in the groundwater contaminated sites. The active-DTS can heat different sections of fiber cable by the heating pulse controller (HPC). The advantage of the HPC is to heat the well water without disturbing the natural groundwater flow direction. It can heat the groundwater with slow velocity and significantly induce the perturbation of temperature. The change of temperature can strengthen the heat transfer to identify the preferential flow and thin permeable zone. Besides, the active-DTS measurements will be verified by the analytical solution of heat transfer with a heated line source. The coupled numerical model will also be refined. The modification will focus on the boundary condition and parameters to represent the situation more realisitically. The results obtained from the two-year project implement will be expect to provide the improved investigation and assessment of a groundwater contaminated sites. The innovative measurement technique can enhance the capability of hydrogeological survey in the near future.

Keyword(s)

分散式光纖溫度感測器
熱能示蹤劑
地下水污染
水文地質
模場試驗
fiber optic distributed temperature sensor
heat tracer
groundwater contamination
hydrogeology
filed experiment

DSpace CRIS

分散式光纖溫度感測器在地下水污染場址之高解析度井下水文地質調查(II)

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