Homework_Assignment_4 - Homework Assignment No. 4 February...

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Homework Assignment No. 4 February 16, 2010 Due on February 23, 2010 @ 2:00 PM PGE368 Spring Semester 2010 Fundamentals of Well Logging Instructor: Carlos T. Verdín, Ph.D. INTERPRETATION OF SPONTANEOUS POTENTIAL (SP) LOGS DESCRIPTION: The objective of this homework project is to make use of spectral gamma-ray, SP, and resistivity logs to qualitatively and quantitatively assess both lithology and potential hydrocarbon-bearing reservoir units. TASKS/QUESTIONS : 1. (a) Using the SP log shown in Figure 1 (also shown on page 20 of PGE368’s Well-Log Compendium), estimate the electrical resistivity of connate water in each of the two existing water-saturated sand units. (b) Determine the corresponding salinity of connate water in ppm. (c) Determine the salinity of mud filtrate in ppm. (d) Explain why the SP log is not null within hydrocarbon-bearing sands. Note the header of this log was included in Homework Assignment No. 3. Perform your calculations of water resistivity and salt concentration using both the formulae included in the Appendix and Schlumberger’s GEN-6 interpretation chart (available on Blackboard). [15 POINTS] 2. Consider the log example shown in Figure 2. (a) Explain whether the logs indicate a siliciclastic sedimentary sequence. (b) Draw the shale baseline on the SP, gamma-ray, resistivity, and sonic logs. (c) Identify sands and shales. (d) Why does the SP log fluctuate to the right of the shale baseline within sands? Carefully explain your answer in comparison to the log behavior shown in Figure 1. [10 POINTS]
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3. Consider the log example shown in Figure 3. Depths are given in ft MD. (a) Explain whether the logs indicate a siliciclastic sedimentary sequence. (b) Draw the shale baseline on the SP, gamma-ray, and resistivity logs. (c) Identify sands and shales. (d) Determine the salinity of mud filtrate in ppm. (e) Determine the corresponding salinity of connate water in ppm. Perform your calculations of water resistivity and salt concentration using both the formulae included in the Appendix and Schlumberger’s GEN-6 interpretation chart (available on Blackboard). For this example, surface temperature is 78 degF, the geothermal gradient is 1.5 degF/100ft, and
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Homework_Assignment_4 - Homework Assignment No. 4 February...

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