Page 97 - A Practical Companion to Reservoir Stimulation

PRACTICAL COMPANION TO RESERVOIR STIMULATION

EXAMPLE F-8
The slope of the straight line on Fig. F-3 is equal to 249 psi/
Moderate-Permeability Oil Well- hr0.2s. Using Eq. 1 1 - 12 the kfw product can be calculated.
Interpretation of Posttreatment Tests

A moderate-permeability oil well (k z 2 md) flowed for 30 k,f w = [ (44.1)(375)( 1.1)( 1.2) 1
(53)(249)
days at an average rate of 375 STB/d. This was followed by a
10-day pressure buildup test. Figure F- 1 is a summary of the r 1
measured rate and pressures for this test. Table F-4 contains I I
the relevant well and reservoir data. Interpret this test and L(0.12)( 1.2)(9x 10-6)(2) J
calculate fracture geometry and/or conductivity variables. = 1030md-ft. (F-28)

Solution (Ref. Section 11-6) Since the fracture was designed for xj = 700 ft, then the F&
As with all pressure transient tests, the first step is flow can be approximated:
regime identification through a pressure and pressbre deriva-
tive log-log diagnostic plot. This is shown in Fig. F-2. As (F-29)
should be expected, for such a moderate-permeability (high
by fracture candidate standards) reservoir, the fracture con- The latter is only an estimate since the actual fracture length
ductivity should be low (FcD z l), and thus only bilinear flow cannot be determined from the test.
should be evident. This is clear on Fig. F-2. After the end of
wellbore storage effects, denoted by the early-time 45"
straight line, a lengthy quarter-slope straight line appears.
This is marked on the figure. No linear flow is evident, and k = 2md I
therefore the calculation of fracture half-length is not pos- fp = 1 month
sible for the duration of this test. (Long-term flow data may
allow the calculation of the fracture length if pseudoradial d = 0.12
flow appears. This method is outlined in Section 11-8.) I
The analysis shown in Fig. F-2 leads to the specialized plot q = 375STBld
shown in Fig. F-3, where the quarter-root of time is plotted h = 53ft I
against the pressure on Cartesian coordinates. This should ~ pwr = 2125 psi (at At=O)
form a straight line through the points identified on the log-log
plot forming a quarter slope. ct = 9 x psi-'
I
I r, = 0.328 ft
I Bo = 1.1 resbbl/STB I
Table F-4-Well and reservoir data for Example F-8.

F-6