![]() The time at which the flattening of the pressure change curve (and corresponding downward movement of the derivative) becomes apparent is a function of the producing time before shut-in. Notice the significant difference in the shapes of both the derivative and pressure change curves for buildup and drawdown tests, with the pressure change curves flattening for buildup tests and the derivatives moving downward with an ultimate slope of –1. Wellbore storage distortion is not included in any of the diagnostic plots in this section.įig. Both pressure and time are in terms of dimensionless variables. For these plots, the derivative was taken with respect to shut-in time and derivative and pressure change curves are plotted vs. Infinite-acting, radial flow reservoirs are described on this page. Some pressure transient test analysis software allows the user a choice in the time function used in taking the derivative and another choice in time plotting function for other software, the time functions used are "hard-wired." The results can be bewildering. either of these time functions, and the shape differs for each plotting function. The derivative of pressure change may be taken with respect to the logarithm of either shut-in time or equivalent time. To further complicate matters for buildup test analysis, the shape of the derivative curve depends on how the derivative is calculated and plotted. (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. These relationships are useful for estimating hydraulic characteristics that are needed for the designs of wells and well fields and for preliminary water-resources management.Recognizing the influence of boundaries can be as important as analyzing the test quantitatively. Relationships between well losses constant for 30 wells with transmissivity and specific capacity, are constructed. The causes for high well losses (entrance velocity (Vn) through water well screen and the distance from the point of water entrance in the well to the point of intake in the pump) are discussed and the relationships are constructed, which seem a positive linear correlation. On the other hand, the drilled wells in El Shab area exhibit relatively high well losses (25%). Relationship of specific capacity and transmissivity is constructed and the established empirical equations can be used to predict the transmissivity of the Nubian aquifer in all new proposed sites for well drilling at which the specific capacity measured without performing pumping tests. In El Shab area, the Nubian Sandstone aquifer has a large range of transmissivity (from 483.12 to 1489.24 m2/day) and, also, specific capacity (from 203 to 486.32 m2/day). Nubian Sandstone Aquifer Transmissivity Specific Capacity Well Loss Entrance Velocity Well EfficiencyĪBSTRACT: For proper water management in the new reclaimed areas, hydraulic parameters of both aquifer and wells related to transmissivity, specific capacity, well loss, formation loss, and water entrance velocity, as well as the relationship between these parameters are the main target after construction of production wells. Relationships between Hydraulic Parameters of the Nubian Aquifer and Wells in El Shab Area, South Western Desert, Egypt (A Case Study) Rorabaugh, “Graphical and Theoretical Analysis of Step Drawdown Test of Artesian Well,” Proceedings of the American Society of Civil Engineers, Vol.
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