#Well drawdown test eastern washington full

(There are different equivalent time functions for radial flow, linear flow, and bilinear flow, as discussed in more detail in Fluid flow in hydraulically fractured wells.)īasically, equivalent time functions apply rigorously only to situations where either the producing time and the shut-in time both lie within the middle-time region or, as is commonly the case, the shut-in time is much less than the producing time before shut in. This problem is augmented by the common use of 'equivalent time' functions to analyze buildup tests on drawdown type curves. However, boundary effects can cause quite different shapes for a given reservoir model at late times in buildup and drawdown tests. The shapes of the diagnostic plots for a buildup test and a drawdown test are essentially identical during the early- and middle-time regions for most tests. Once the proper reservoir model has been determined, test analysis may be relatively straight-forward type-curve matching or regression analysis using modern well-test analysis software. The model selected to interpret the test quantitatively must be consistent with geological and geophysical interpretations. However, a problem in recognition is that many reservoir models may produce similar pressure responses. An additional pipe, installed for providing thermistor access, allows recording of the geothermal gradient in the well which provides a basis for estimating vertical ground-water movement in the area.Recognizing the influence of boundaries can be as important as analyzing the test quantitatively. The pipes also permit chemical quality monitoring of water in the various aquifer zones. In the completed well each aquifer zone is isolated by cement seals, and piezometer pipes installed to zones B through H allow a basis for defining the vertical hydraulic gradient and ground-water movement in the area. The tests indicate that most of the water available to the well is from the deepest aquifer (zone H).īorehole geophysical logging supplemented the drillers log of the well and provided information on natural gamma radiation, water temperature and resistivity, and borehole diameter.

#Well drawdown test eastern washington full

Test pumping during drilling showed that the well had specific capacities of (1) 4-8 gpm (gallons per minute) per foot of drawdown when at the 255-foot depth and open to aquifers A through D, (2) 5.6 gpm per foot of drawdown when at the 640-foot depth and open to aquifers A through G, and (3) 76 5 gpm per foot of drawdown when at the full 750-foot depth and open to all eight aquifers. The well was drilled by air-rotary methods and penetrates eight aquifer zones (A through H) the upper 75 feet of the well is cased, and the remainder of the hole is open in basalt. The well provides information on aquifer characteristics in this area which are not available from existing deep irrigation wells. The 750-foot test-observation well drilled near Davenport, Wash., is one of several drilled to date (1972) to provide information on ground-water conditions in selected areas of the State.