Question:
A drawdown test is analyzed to find the permeability and skin factor of a reservoir using a semi-log plot, where the flowing bottomhole pressure (in psi) is plotted on a linear scale against time (in hours). The flow rate is 1500 STB/day, the oil formation volume factor is 1.2 RB/STB, and the oil viscosity is 1 cP. The thickness of the producing bed is 10 ft. The slope of the straight line fitting the data in the middle time region of the semi-log plot is 60 psi/log cycle.
The permeability of the reservoir (in mD) is _______ (rounded off to one decimal place).
A drawdown test is analyzed to find the permeability and skin factor of a reservoir using a semi-log plot, where the flowing bottomhole pressure (in psi) is plotted on a linear scale against time (in hours). The flow rate is 1500 STB/day, the oil formation volume factor is 1.2 RB/STB, and the oil viscosity is 1 cP. The thickness of the producing bed is 10 ft. The slope of the straight line fitting the data in the middle time region of the semi-log plot is 60 psi/log cycle.
The permeability of the reservoir (in mD) is _______ (rounded off to one decimal place).
The permeability of the reservoir (in mD) is _______ (rounded off to one decimal place).
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Use the semi-log drawdown slope formula k = 162.6 q B mu / (m h) with field units for q, B, mu, m and h.
Updated On: Jul 28, 2026
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Verified By Collegedunia
Correct Answer: 487.8
Solution and Explanation
Step 1: List the given data:
Flow rate q = 1500 STB/day
Oil formation volume factor B = 1.2 RB/STB
Oil viscosity mu = 1 cP
Bed thickness h = 10 ft
Slope of the semi-log straight line m = 60 psi per log cycle
Step 2: Write the governing equation for semi-log drawdown analysis:
For a well producing at a constant rate, the permeability obtained from the slope of the middle time region of a semi-log plot of flowing bottomhole pressure versus the logarithm of time is given in field units by \[ k = \frac{162.6\, q\, B\, \mu}{m\, h} \]
Step 3: Substitute the given values into the formula:
\[ k = \frac{162.6 \times 1500 \times 1.2 \times 1}{60 \times 10} \]
Step 4: Simplify the numerator:
162.6 x 1500 = 243900
243900 x 1.2 = 292680
292680 x 1 = 292680
Step 5: Simplify the denominator:
60 x 10 = 600
Step 6: Divide the numerator by the denominator to get the permeability:
k = 292680 / 600
k = 487.8 mD
Final Answer:
\[ \boxed{k = 487.8 \text{ mD}} \]
Flow rate q = 1500 STB/day
Oil formation volume factor B = 1.2 RB/STB
Oil viscosity mu = 1 cP
Bed thickness h = 10 ft
Slope of the semi-log straight line m = 60 psi per log cycle
Step 2: Write the governing equation for semi-log drawdown analysis:
For a well producing at a constant rate, the permeability obtained from the slope of the middle time region of a semi-log plot of flowing bottomhole pressure versus the logarithm of time is given in field units by \[ k = \frac{162.6\, q\, B\, \mu}{m\, h} \]
Step 3: Substitute the given values into the formula:
\[ k = \frac{162.6 \times 1500 \times 1.2 \times 1}{60 \times 10} \]
Step 4: Simplify the numerator:
162.6 x 1500 = 243900
243900 x 1.2 = 292680
292680 x 1 = 292680
Step 5: Simplify the denominator:
60 x 10 = 600
Step 6: Divide the numerator by the denominator to get the permeability:
k = 292680 / 600
k = 487.8 mD
Final Answer:
\[ \boxed{k = 487.8 \text{ mD}} \]
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