What is It About Shaly Sands? Shaly Sand Tutorial 1 of 3
- E. C. Thomas (Bayou Petrophysics)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- February 2018
- Document Type
- Journal Paper
- 7 - 14
- 2018. Society of Petrophysicists & Well Log Analysts
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- 226 since 2007
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Editor’s comment: This article is the second in a series of short “tutorial-like” notes styled to mentor users of digital well log data in becoming confident practitioners of Petrophysics.
Some may ask: Why do we need to understand the petrophysics of shaly sands? The best answer I can give is to relate a true story that happened to me while I was on a broadening assignment in the Coastal Division of Shell Oil Company, located in New Orleans. These offices were in Gentilly, and if I had rated a window, it would have overlooked the Jewish Cemetery. I was struggling to understand formation evaluation in practice with help from Brian Ausburn, John Stieber, Roy Coles and many others who freely mentored me while I was “learning the ropes.” I had quite a large learning curve coming from a laboratory environment. I made many, many mistakes and was teased about someone with a PhD not being able to master the “easy stuff.” So they gave me the nickname of ‘Easy’ until I could prove I had learned the easy stuff. After suffering through many false starts I finally understood how to interpret low-resistivity pay. My job entailed counting pay thickness and computing porosity and water saturation. It was fun finding pay where none had tried before. The first time I called a sand with a resistivity of 0.6 Ωm pay, the Division Production Engineer called me crazy and bet that if that zone was perforated it would flow all water. Of course I had an ace in the hole! Chris Clarke was the geologist on our team was the one to propose drilling the well. He knew this location was updip from a producing well and would find a section of the fault block that had not been swept. Well, he was right and so was I—the well flowed 95% oil. The Division Production Engineer came to my office to say he was sorry to have doubted me and would not have any more qualms about perforating intervals I selected. He then changed my nickname to ‘Easy Money,’ which I proudly wore the rest of my time in New Orleans. The Thomas- Stieber method was accepted and used by the staff to never miss a low-resistivity shaly sand again. Understanding how the geological deposition of the sand affected the logs and their resulting capillary pressure proved to be a very profitable technique. I hope these three tutorials will make understanding shaly sands much easier and remove the “magic” from their interpretation.
|File Size||6 MB||Number of Pages||8|