WATER INFLUX The aquifer–reservoir system is characterized by the following data:
radius, ft h, ft k, md φ, % µw , cp cw , psi−1 cf , psi−1
Reservoir
Aquifer
2000 25 60 17 0.55 0. 7 × 10−6 0. 2 × 10−6
∞ 30 80 18 0.85 0. 8 × 10−6 0. 3 × 10−6
If the encroachment angle is 360◦ , calculate the water influx as a function of time by using: (a) the van Everdingen and Hurst method; (b) the Carter and Tracy Method. 5. The following table summarizes the original data available on the West Texas water drive reservoir: Oil zone Aquifer Geometry Area, acres Initial reservoir pressure, psia Initial oil saturation Porosity, % Boi , bbl/STB Bwi , bbl/STB co , psi cw , psi−1
Circular 640 4000 0.80 22 1.36 1.00 6 × 10−6 3 × 10−6
Semicircular Infinite 4000 0 – – 1.05 – 7 × 10−6
The geological data of the aquifer estimates the water influx constant at 551 bbl/psi. After 1120 days of production, the reservoir average pressure has dropped to 3800 psi and the field has produced 860 000 STB of oil.
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The field condition after 1120 days of production is given below: p = 3800 psi, Np = 860 000 STB, Bo = 1. 34 bbl/STB, Bw = 1. 05 bbl/STB, We = 991 000 bbl, tD = 32. 99 (dimensionless time after 1120 days), Wp = 0 bbl It is expected that the average reservoir pressure will drop to 3400 psi after 1520 days (i.e., from the start of production). Calculate the cumulative water influx after 1520 days. 6. A wedge reservoir–aquifer system with an encroachment angle of 60◦ has the following boundary pressure history: Time (days)
Boundary pressure (psi)
0 365 730 1095 1460
2850 2610 2400 2220 2060
Given the following aquifer data: h = 120 ft, cw = 4 × 10−6 psi−1 , k = 60 md, reservoir area = 40 000 acres aquifer area = 980 000 acres,
cf = 5 × 10−6 psi−1 , µw = 0. 7 cp, φ = 12%, T = 140◦ F
calculate the cumulative influx as a function of time by using: (a) the van Everdingen and Hurst method; (b) the Carter and Tracy method; (c) the Fetkovich method.
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