Here is a generalized stratigraphic column and cross section of the Northern Delaware Basin. One can see the series of stacked reef complexes dissecting the upper half of Permian strata (Guadalupian & Ochoan). The Bone Spring and Wolfcamp make up the lower half (Leonardian & Wolfcampian).
Delaware Wolfcamp (Wolfcampian): Behaves as a reservoir and source rock due to ideal mineralogy and grain size distribution. Industry publications cite mineralogy at 50-90% quartz and carbonate, with 10% clay. Other stats include a pressure gradient of 0.7 psi/ft, porosity around 5-9%, and TOC about 2-5%.
Avalon Shale (Leonardian): Organic-rich shale and siltstone lying in between the top of the Bone Spring Formation and the top of the First Bone Spring sandstone. In Loving County, Avalon net pay is up to 600 feet thick. The shale has good TOC at 5-6% with low permeability generally less than .1md and production occurs where logs indicate high gamma ray (>75u). Porosity is around 16-18% and contains 105 MMboe in place per section.
Bone Spring (Leonardian): The entire Bone Spring group averages roughly 3,500 feet thick. It can be subdivided into alternating carbonate and clastic (sand) members deposited in slope and basin settings. This reciprocal sedimentation is thought to be the result of sea level changes where carbonates were deposited in transgression (high stand) and clastics in regression (low stand).
Yeso (Leonardian): The Yeso Formation is said to be comprised of four subplay members: The Upper Yeso (Glorieta and Paddock members), Blinebry subplay, Tubb subplay, and Drinkard subplay. The entire formation consists of 1000 feet of shales, sandstones, reddish colored siltstones and thin beds of limestone and gypsum.
Abo (Wolfcampian-Leonardian): The Abo formation is typically interbedded with reddish brown siltstone, shale and sandstone; the sandstone said to become more arkosic to the north and northeast.
Below are a series of maps, generated with data from DI Analytics and DI Desktop, to get some spatial insight on the geology, productivity and operator activity.
This is a pretty general overview of the Delaware Basin and Northwest Shelf strata. This is simply what I like to do when first analyzing a basin. Check back soon for a follow up blog where I plan to investigate further into specific formations of the Permian Basin.
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