A pressure build-up test was conducted in a well after 1000 days of producing oil at a constant rate of 0.01 reservoir-m3/s

Q. A pressure build-up test was conducted in a well after 1000 days of producing oil at a constant rate of 0.01 reservoir-m³/s. The two shut-in bottom-hole pressure readings taken at 0.5 day and 1 day after shut-in are 150 × 10⁵ Pa and 151 × 10⁵ Pa, respectively. These pressure points correspond to the linear region of the Horner’s plot. The reservoir thickness is 100 m and oil viscosity is 0.001 Pa.s. The permeability of the reservoir is      mD (round off to 1 decimal place). [1 mD = 10^-15 m²].

Ans: 55.97mD

Sol:

Q = 0.01 m3/sec = 0.0629 bbl/sec = 5434.56 bbl/day
Tp = 1000 days
∆t1 = 0.5 days
∆t2 = 1 day

P1 = 150 x 105 pa = 2175.56 psi
P2 = 151 x 105 pa = 2190 psi
h = 100 m = 328 ft
µo = 0.001 pa-sec = 1 cp
Horner time-1 = (1000+0.5)/0.5 = 2001
Horner time-2 = (1000+1)/1 = 1001