Page 196 - Introduction to Petroleum Engineering

ACTIVITIES 183
9.3 Suppose a density log is making measurements in a formation where the
density of sandstone is 2.70 g/cc and the fluid density of brine is 1.03 g/cc.
Use Equation 9.1 to plot porosity versus bulk density for the density log.
Assume bulk density ranges from 2 to 2.70 g/cc.
9.4 Suppose an acoustic log is making measurements in a water‐saturated
limestone formation. The limestone matrix has a transit time per foot of
−
44µs/ft = 4410 s/ft corresponding to an acoustic velocity of 23 000 ft/s.
×
6
−
×
6
The brine transit time per foot is 189µs/ft = 189 10 s/ft corresponding to an
acoustic velocity of 5300 ft/s. Use Equation 9.5 to plot porosity versus log
transit time for the acoustic log. Assume log transit time per foot ranges from
40 to 100 µs/ft.
9.5 Fill in the following table using Equation 9.11 to calculate formation resistivity
factor F for a resistivity log.
Sand Carbonate
a 0.81 0.81 1 1
m 2 2 2 2
Porosity 0.1 0.2 0.1 0.2
F

9.6 a. Fluid density for a volume with gas and water phases can be estimated
using ρ = S g × ρ + S w × ρ where ρ , ρ refer to gas density and water
f
w
g
w
g
density, S , S refer to gas saturation and water saturation, and
g
w
S + S = 1. Estimate fluid density when gas density is 0.00086 g/cc,
g
w
water density is 1.03 g/cc, and water saturation is 30%. Hint: Convert
water saturation to a fraction and calculate gas saturation from
S + S = 1.
g
w
b. Suppose bulk density ρ is 2.20 g/cc from a density log, and density of
b
rock matrix ρ is 2.62 g/cc. Use the fluid density ρ from Part A and
f
ma
Equation 9.1 to estimate porosity.
9.7 Estimate the regional dip using the well logs in Figure 9.9. Hint: Fill in the
table in the following. Use the RC trace to identify the top of the producing
formation and then estimate the dip angle using tangent (dip angle) = (difference
in depth between top of producing formation in Wells 7 and 9) divided by
(distance between Wells 7 and 9).
Well Number RC‐Top (ft) Distance from Well 7 (ft)
7 0
3 800
9 1400