Laserfiche WebLink
Appendix B - Packer Test Methods and Results <br />where: K = hydraulic conductivity [LV] <br />r = radius of the drill hole [L] <br />L = length of the test interval [L] <br />To = time at which Who is 0.37 [T] <br />To determine To, the ratio of the measured head to the initial head (h/ho) is plotted arithmetically on the y <br />axis vs. time which is plotted logarithmically on the x axis. The pressure decay vs. time should plot as a <br />straight line, and To is determined directly from the graph. <br />The Hvorslev method assumes that water is injected into the interval at flow rate Q, which is based on the <br />geometry of the well: <br />Q=7r-r2.d?t <br />Packer tests in low-permeability rock are configured such that a pulse of water is injected using a hand <br />pump or water hose. The Q is measured for each stroke of the hand pump, and the compressibility of the <br />system (packer interval) is calculated: <br />Q = c. (dht) <br />The log-linear Hvorslev solution is then modified to: <br />K = c ln(Ir) <br />2•L•To <br />• where: c = the compressibility [LZ] <br />4.6 Shut-in Test Analysis (Horner, 1951) <br />The shut-in tests are analyzed in the manner developed by Horner (1951) (see Domenico and Schwartz, <br />1990) for permeability testing in oil fields. In this case, tests are conducted at ground surface and the <br />packer interval is subject to some natural static pressure which is greater than that surface. The interval is <br />shut in until pressures equilibrate, then a valve is opened and the flow rate and time are measured. Then <br />the discharge pipe is closed, and the interval is "shut-in". The rise in pressure is measured over time. The <br />pressure measurements (in feet of head) are plotted against the log of time, and the transmissivity is <br />determined by: <br />T 2.3- Q <br />= <br />4•71 •(P-PO) <br />where: T = transmissivity VV] <br />Q = volumetric flow during open portion of test [L'V] <br />P = pressure at end of log cycle [L] <br />Po = pressure at start of log cycle [L] <br />The Horner analysis is similar to the Jacob "straight-line" recovery analysis, except that the "pumping" rate <br />(Q) is the natural flow rate from the borehole, measured prior to the shut-in test. <br />• <br />4109B.071116 Whetstone Associates