# Petroleum Engineering Questions

## Transcribed Text

1) GR, bulk density and neutron porosity in SS scale logs of well from interval 5000 to 5100 ftis presented here. Also the log data is included in the Excel file. a) Calculate the apparent density porosity in sandstone, limestone and dolomite scale for the interval (5000- 5100) foot by foot Assume fluid is fresh water b) Calculate the apparent neutron porosity in limestone and dolomite scale for the interval (5000-5100) foot by foot. Use the equations on slide 33 c) On single graph, plot density porosity and neutron porosity in sandstone scale vs. depth. For that, make sure I) The porosity scale is from 0% to 60% increasing right to left (standard presentation of SS scale). II) Depth is increasing from top to bottom (standard presentation of depth track). Based on the crossover/overlay of density and neutron curves, do you see any distinctive lithology or gas presence? Do you see any differences between the log presented here and the plot you have? (YOU SHOULD NOT!) d) Repeat part "C" for limestone scale and set the range of porosity from -15% to 45% increasing right to left Now, identify the zones and report the lithology and any fluid change and fluid type you observe. Hint: Refer to slides 34 & 35. e) Repeat part "C" for Dolomite scaleand set the range of porosity from -15% to 45%increasing right to left. f) Find the apparent neutror porosity in limestone and dolomite scale for the following depths using chart Por-5 and compare them with your results from part "b" the following table. Log Part b Chart por-5 Depth PHIN (SS) PHIN(LS) PHIN(DOL) PHIN(LS) PHIN(DOL) 5010 5030 5050 5070 5090 g) If there is any gas zone(s), report the interval of gas zone and calculate the True porosity of gas zone interval (average porosity for the gas zone). h) Is there any oil or water zones? Can you make decision eitheri is oil or water just based on the available logs? Whatmore logs you need to finalize your decision? Formation Evaluation PNGE 450 GR (API) 1.65 RHOB (gr/cm3) 2.65 o 150 60 PHIN (P.U) SS scale o 5000 5010 5020 5030 5040 5050 5060 5070 5080 5090 5100 2) Presence of gas results densityporosity to beread higher than the true porosity value To calculate the true porosity flushed zone saturation is required By referring to the slides 17-18 of Density notes, and your knowledge of Archie's law, prove: (pmp -pg) (oma pg) Important Notes: 1) Show your calculations. If the same calculationis repeated just show one example of the calculation. 2) Include charts being used and show your work on those charts. 3) Submit your HW only in MS Office word format.

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Question 1)
Calculation of apparent density porosity at depth of 5000 ft (as an example):

φ_D=(ρ_ma-ρ_b)/(ρ_ma-ρ_f )
Sandstone → φ_D=(2.65-2.049)/(2.65-1)=0.36
Limestone → φ_D=(2.71-2.049)/(2.71-1)=0.39
Dolomite → φ_D=(2.87-2.049)/(2.87-1)=0.44
The rest of calculations are presented at the end of this question.

Calculation of apparent neutron porosity at depth of 5070 ft (as an example):
φ_NLS=φ_NSS-4P.U=27.28-4=23.28%
φ_NDol=φ_NLS-7.5P.U=23.28-7.5=15.78%
The rest of calculations are presented at the end of this question.

The plot and identification of lithology and zones are given below. A gas zone is detected from 5000 to 5020 ft where density porosity is significantly higher than neutron porosity. Depths 5020 to 5040 and 5090 to 5100 ft show shale zones where GR is high and neutron porosity is abnormally high due to presence of hydrogen of water bound in the shale zones. There is no difference between the log presented in this homework and this below plot....
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