Page 85 - A Practical Companion to Reservoir Stimulation

DESIGN AND MODELING OF PROPPED FRACTURES

EXAMPLE E-14
Three conclusions can be drawn:
Leakoff Coefficient and Injection Rate
The lower leakoff coefficient would result in consis-
For the I -md reservoir, calculate the impact of the injection tently higher NPV.
rate on the 1 -yr NPV for two leakoff coefficients equal to 5 x The problem can be remedied by using a larger injec-
ft/G and 9 x 10-4ft/6, respectively. tion rate. For example, the same NPV for CL= 9 x
ftls and 10 BPM can be realized for CL = 5 x
Solution (Ref. Sections 8-3 and 8-4) lo-' ft/6 and 20 BPM ($2.19 million).
Five injection rates were used (10, 20, 40, 60 and 80 BPM),
and all other variables were held constant as given in Table The impact of increasing the injection rate is far more
E-6. (This is not entirely realistic since the fracture height pronounced in the higher leakoff coefficient. This is
would be different for these injection rates. However, for the shown by the steeper slope in the curve for CL = 5 x
purpose of this comparison, the fracture height is held constant.) 10-3 ftl6.
The two leakoff coefficients would depend on the Success or (Note that the optimum fracture half-lengths were 1500 ft for
failure of the deposited filter cake or the intensity of thief all injection rates for CL=9 x ftlG. For CL= 5 x
zones. Such a disparity can be observed in actual treatments ftlG, they were 1300 ft for 10 and 20 BPM and
within the same reservoir. 1400 ft for the other three injection rates.)
Figure E-12 is a graph of the optimum 1-yr NPV for the
range of injection rates and the two leakoff coefficients.

E-25