A flow test...cylindrical reservoir...estimated porosity 0.2 – 0.23, viscosity 0.5 – 0.55 cp, permeability 100 – 110 md. Total compressibility 0.00002 1/psi. How long...to ensure...test reaches 2,000 ft?
See 12 WLT 6*. To "ensure" 2,000 ft, choose the most conservative estimates for the longest time. Viscosity & porosity directly correlate, so higher numbers mean longer time for them. But permeability is inversely correlated, so use the smaller number. Using the radius of investigation equation (12 WLT 6) we calculate:
t = 948(0.23)0.55(0.00002)(2000^2)/100 = 95.9 (D).
The info on 12 WLT 6 needed for this problem is in the new Reference Guide
(provided with the exam) on page 7 of chapter 1. Practice finding these equations quickly.
A quick note - in the 2019 SPE reference the equation uses .029 outside the radical instead of the implied .032 from the equation on 12 WLT 6. Therefore the answer using the SPE Reference Eqn (Earlougher 1977) I calculated is 120 hours. Hopefully this is helpful for others working through the problem set using Ali's reference
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