Theoretical study of skin effect on multilevel slug tests in highly permeable aquifer 指導教授 : 陳家洵 老師 報告者 : 謝頤祥 報告日期 :

Damaged Zone Around a Well Damaged zone

What is Skin Effect? A damaged zone caused by drilling mud invasion is less permeable than the native aquifer; K skin < K aquifer as for “positive” skin. A damaged zone caused by overdevelopment is more permeable than native aquifer; K skin > K aquifer as for “negative” skin. Neglecting the skin effect results in over- or under-estimate of aquifer hydraulic conductivity.

(I) Finite Thickness Skin Zone, K 1, S S1, and r 1 l s, test interval length b, aquifer length r w, radius of well r 1, radius of skin

(II) Infinitesimal Thickness Skin Zone, Skin Factor (S k ) l s, test interval length b, aquifer length r w, radius of well

Skin Effect Positive Skin : Negative Skin :

S S1 Sensitivity in Confined Aquifer

S S1 Sensitivity in Unconfined Aquifer

Same Results from Two Models (Confined Aquifer with Positive Skin)

Same Results from Two Models (Confined Aquifer with Negative Skin)

Same Results from Two Models (Unconfined Aquifer with Positive Skin)

Same Results from Two Models (Unconfined Aquifer with Negative Skin)

Conclusions The influence of S S1 is negligible as skin zone thickness is relatively small. Infinitesimal skin approach is valid for both positive and negative skin effects, and can replace the finite thickness model.

Future Work To investigate partially penetrating effects under negative skin on MLST response. To estimate the skin factor from field pumping tests.

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