[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Speaker: Nay wells are affected by a well\Nskin, a low permeability layer that
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,surrounds the well and causes the drawdown\Nin the skin to be less than- er to be
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,greater than the drawdown that\Nwould be expected otherwise.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So, we can see this in the, in the sketch.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,This line here is the expected drawdown\Nusing, uh, the Jacob analysis, or
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,perhaps some other analysis, but as we\Nget right in the vicinity of the well, we
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,see that there's a low permeability zone\Nhere, and the head goes like so, follows
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,this dashed line.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And as a result, this is the expected\Ndrawdown based on our theoretical analysis.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,It is using the properties of the aquifer,\Nuh, out here away from the well
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,[stammering] in this region, but in fact\Nwe observe that the drawdown at the well
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,is here, so the drawdown is greater, um,\Nand that results from the extra headloss
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,due to the well skin.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So we want to characterize this, and one\Nway to characterize it is to use the well
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,efficiency, which is the ratio of the\Nexpected drawdown from our theoretical
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,analysis to the observed drawdown,\Nwhat actually occurs in the field.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So we need a way to calculate what the\Nexpected drawdown is, and we can do
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,this with the Jacob analysis.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,What I'm showing here is a version of the\NJacob analysis that's set up to calculate
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,the head- er I guess this is the drawdown\Nhere, um, as a- at a particular time.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So, the important thing to recognize is\Nright here.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,The radial distance that we're using here\Nis the radius of the well.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,What we used in the previous analysis\Nwas the radial distance of the monitering
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,well, where our data were made.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,In this case, we need to use the radial-\Nthe radius of the well itself.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,This time here, that's the time, the\Nelapsed time, for a data point that we're
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,gonna use to determine the observed\Ndrawdown.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,The calculation goes like so: we put in\Nthe observed time and the radius
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,of the well, and everything else is pretty\Nmuch the same, the s and the t we've
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,calculated using a monitoring well out\Nhere in the formation.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,The performance here of the monitoring\Nwell, the head in the monitoring well, is
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,not effected by the skin, so when we\Ncalculate TNS from the monitoring well
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,data, we're getting something that's\Nreally just affected by the, um,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,formation properties.