Oil Well Testing Handbook
Providing real-life examples and cases, this resource contains the basics of well testing methods as well as all of the latest developments in the field, including testing for horizontal wells.
TABLE OF CONTENTS Oil Well Testing Handbook
5.9: Variable-Rate Pressure Buildup Analysis
5.9 Variable-Rate Pressure Buildup Analysis
The pressure buildup behavior is described by
where t t n?1 = ?t, time after shut-in and q n?1 is the production rate just before shut-in. Eq. 5-84 is based on the fact that for t = t p1 + t P2 + +t pn?1 + (t ?t n?1) the reservoir is infinite-acting. The following analysis
procedure can be used. Plot p ws versus on ordinary (Cartesian coordinate) graph paper, where plotting function is
Determine the slope m of the plot and calculate the formation permeability by the equation
Calculate the skin factor s from the equation
The original reservoir pressure p i is the value of p ws on the MTR line extrapolated to = 0. Figure 5-22 shows the schematic representation of rate variation preceding a pressure buildup test.
Figure 5-22: Schematic representation of rate variation preceding a pressure buildup test
Example 5-14: Analyzing Variable-Rate Pressure Buildup Test
A variable-rate flow test was run on a well with the given properties. From these properties and the data in Tables 5-11 and 5-12, determine k, s,
( ?p) skin, p *, and flow efficiency. Well and reservoir data: depth = 5250 ft; average pressure = 3000 psi; ? 0 = 0.80 cP; ? 0 = 1.136 rb/stb; h = 11 ft; ? = 0.12; c t
Copyright Elsevier Inc. 2004 under license agreement with Books24x7
