| 摘要: | 所有的含水層都具有某種程度的異質性，而水力傳導係數的空間分佈 K(x,y,z)強烈影響地下水流場，溶質傳輸，與有機液體遷移現象。多深度微水試驗(MLST)技術已被廣泛用於調查含水層異質性；亦即，K(x,y,z)。此技術藉用雙封塞組合在所需深度將井篩隔絕成單一測試段；在每一測試段進行定深度微水試驗並量測其壓力反應。分析每一深度的壓力反應可得知K(z)垂直變化。高K 與低K 的壓力反應截然不同；高K 情況下的壓力反應呈震盪變化，低K 則呈單ㄧ變化。震盪或單一變化的壓力反應均容易受到薄壁效應(井邊局部性水文地質改變)影響。已有相當多研究探討薄壁效應對微水試驗壓力反應的影響，但均限於低K 情況。故本研究目的是瞭解高K 情況下薄壁效應對MLST 壓力反應得影響。為達成此目的，我們將在一非受壓含水層進行現場測試並且發展相關理論模式。將在不同井中執行一系列有薄壁效應和無薄壁效應的 MLST，所得資料將揭示薄壁效應對MLST 壓力反應的衝擊。在理論探討部份將發展兩個數學模式；ㄧ個假設薄壁為無限薄厚度另ㄧ則假設薄壁有限厚度。兩種途徑均適合處理薄壁效應。無限薄模式特別利於資料分析因其僅使用一薄壁因子參數來反應薄壁效應。限厚度模式則特別利於瞭解薄壁層水文地質特性對壓力反應的影響。兩個模式不限於高K 情況，亦可處理低K 情況。綜合使用此兩模式和現地試驗資料可提供辨識薄壁效應方法和建立資料分析中處置薄壁效應的方法，強化使用MLST 決定含水層異質性的準確性。 All aquifers are heterogeneous to a certain degree, and the spatial variability of hydraulic conductivity K(x,y,z) significantly influence the groundwater flow field, solute transport phenomena, as well as migration of hydrocarbon liquids. The multilevel slut test (MLST) technique has been widely used to characterize aquifer heterogeneity. It utilizes a double-packer assembly to isolate the well screen to an individual test section at depths of interest. For each such depth, a depth-specific slug test is performed and the pressure response measured. Analyzing the pressure responses of each depth yields the possible vertical profile of K(z). The pressure response is distinct in the high- and low-K conditions; that is, it is oscillatory in the high-K conditions while monotonic in the low-K conditions. The pressure response, oscillatory or monotonic, is prone to the influence of skin effects. Many studies have been made to study the skin effects on the slug test pressure response; but they are for various concerns under the low–K conditions. Therefore, the purpose of this project is to investigate the skin effect on the oscillatory response of the MLST. To achieve this goal, both field and theoretical studies will be conducted. In a permeable unconfined aquifer, a series of MLST will be performed at wells with and without the skin effect. The data produced will reveal the skin effect on the pressure response. In the theoretical study, two models will be developed by assuming the skin zone to be of infinitesimal thickness or of finite thickness. Both assumptions are valid approaches in dealing with the skin effect. The infinitesimal-thickness model is particularly useful for data analysis as the skin effects is accounted for by one single unknown a priori parameter, the skin factor. The finite-thickness model is conducive to understand how the hydraulic properties of the skin zone will influence the pressure response. Not limited to the high-K conditions, both models can handle the low-K conditions as well. The combined use of both models along with the field data will help identify the skin effect in pressure response and establish a method to deal with it in data analysis, thereby securing more accurate determination of aquifer heterogeneity by the MLST. 研究期間：10008 ~ 10107 |
