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Appendix B - Packer Test Methods and Results 7 <br />material at a measured flow rate (Q), and then measure the head loss (DH) that occurs as a result of that flow <br />over a measured distance (L) parallel to the flow. <br />There are many of ways to measure hydraulic conductivity. The fundamentals for each approach remain the <br />same: to measure hydraulic conductivity, it is necessary to have (1) a flow into (or out of) the formation and (2) <br />a resulting head gradient or head change in the formation. <br />When the more popular hydraulic conductivity test methods are examined, it becomes clear that the methods <br />all comprise various ways to induce a flow and measure a resulting head gradient or change in the formation. <br />The methods of permeability evaluation fall into two categories: (1) tests where the flow and the measured <br />head impact are time-coincident and (2) tests where they are not. <br />4.2 Steady-State Flow (Theim Analysis) <br />When the flow from the isolated (packed off) interval is steady, the hydraulic conductivity (K) can be <br />calculated using the steady-state radial flow equation (Theim, 1906). For tests conducted in vertical wells <br />and in moderate-permeability packer test intervals, the standard solution to the Theim equation is as follows: <br />_ 27rKHL <br />Q ln(R// <br />where: Q = volumetric flow rate [L3V] <br />K = hydraulic conductivity [LT-'] <br />H = water head above static water level [L] <br />L = length of packer interval [L] <br />R = radius of influence of test [L] <br />r = radius of drill hole [L] <br />A common approximation is to equate the radius of influence of the test to the length of the packed off <br />interval, as it is assumed that drawdown beyond this distance is not significant. The Theim (1906) equation <br />can be solved for hydraulic conductivity as given in the following equation: <br />K = Qln(Ir) <br />21rL H <br />For underground test holes in very low permeability rock, the Theim solution is modified to account for the <br />compressibility of the system and the geometry of the test situation. <br />4.3 Determination of Compressibility <br />The compressibility of the drill hole and packer assembly must be determined, if the test interval is of very <br />low permeability. The compressibility will be derived from the relationship between injection volume and <br />resulting pressures. <br />4.4 Constant Head Injection Test <br />In moderate permeability test intervals, injection tests may be performed under conditions of relatively <br />constant head. In time, the flow rate becomes constant when conditions equilibrate. If the head (H) and <br />flow rate (Q) of water into the pipe are measured under these quasi-equilibrium conditions, the hydraulic <br />conductivity (K) can be calculated from the following equation: <br />• <br />4109B.071116 Whetstone Associates