Lessons Learned in Permian Core Analysis: Comparison Between Retort, GRI, and Routine Methodologies


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SPWLA Distinguished Speaker Series. In today’s competitive cost environment, core acquisition and analysis is too often dismissed as unaffordable. This forces the petrophysicists to make every dollar count in core evaluation. Tough choices, then, have to be made – many people chase the lowest bid, cheapest methodologies, reduced oversight, and less sampling. In this paper, insights will be shared from a comprehensive round-robin study directly comparing the results of the most common techniques (GRI/Retort/RCA) utilized by major vendors. Understanding differences in technique early in an evaluation process can help efficiently direct technical spend.

As with many comparison studies, this project started with the reconciliation of analysis sourced from different laboratories using different methodologies.

There was a significant business driver to this work as we noticed differences in porosity and fluid saturations which contribute to (~25%) difference in hydrocarbon pore volume among vendors using alternative techniques. These differences directly impact log calibration objectives as well as estimations of hydrocarbons in place.

We began to ask simple questions -- should we use crushed samples or routine core plugs? What is the impact of analytical technique on the results? What role does lithology and organic content play in the results from different analytical techniques? What is the role of sample size? What is the variability between vendors for identical procedures? If there is variability, what is the apparent cause?

Ten twin Permian samples from the Delaware Basin will be discussed in-depth using a plethora of available information including X-Ray Diffraction (XRD), Total Organic Carbon (TOC)/RockEval, Retort, and Dean- Stark/Gas Research Institute (GRI) protocol analysis from two labs and RCA from one lab. These 10 samples were picked to represent varying lithofacies with a range of organic, mineralogical, and water/oil content. The level of oversight at each data source was also tracked.

Through detailed analysis of the raw data from these measurements, we address the questions above. With these results, we hope to 1) maximize every dollar spent in core analysis, 2) focus oversight where it is truly required, and 3) accurately and consistently evaluate the core analysis in the Permian play for fast and value- driven business decisions.

Your Instructor

Aidan Blount, SPWLA
Aidan Blount, SPWLA

Aidan Blount is a Petrophysicist and Opportunity Advisor with Shell. He joined the company in 2013 after graduating from The University of Texas at Austin with a B.S. in Petroleum Engineering. Since joining Shell, Aidan worked on several basins as part of a regional exploration team before joining the Permian Asset in 2015. Aidan has been an active member of SPWLA over the same time period, receiving the “Best Paper” award at the 2017 Symposium and serving as an SPWLA Distinguished Lecturer.