--> High Resolution Basin Modeling Insight Into Syndepositional Permian Reef Architecture Through Integrated Lidar-XRF Analysis, Slaughter Canyon, New Mexico

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High Resolution Basin Modeling Insight Into Syndepositional Permian Reef Architecture Through Integrated Lidar-XRF Analysis, Slaughter Canyon, New Mexico

Abstract

The classic Permian Capitan reef architecture and growth pattern seen in the Guadalupe Mountains of southeastern New Mexico have been described as product of continuous progradation and aggradation with increased steepening of the downdip talus until the onset of the Ochoan. However, does what one observe in outcrop today accurately reflect the paleodepositional morphology? Results from integrated LiDAR (Light Detection and Ranging), XRF (X-Ray Fluorescence), and SGR (Spectral Gamma Ray) analysis of the Late Guadalupian strata exposed on the eastern wall of Slaughter Canyon (approximately 2.25 km long by 0.60 km high) suggest the answer is “no” and contradict this notion of a simplistic model of continuous progradation and aggradation with increased steepening. Eight distinct algal-sponge bioherms with differing paleotopographic apexes can be identified on LiDAR reflectivity. High resolution analysis carried out in BasinMod 1-D and BasinMod 2-D of 76 virtual wells at approximately 30 m lateral distance intervals constructed along the canyon wall reveal alternating dip angles, gentle to steep to gentle, for the bioherm facies and associated basinward talus. Dip angles observed today in outcrop are an exaggerated product of post depositional compaction which can be restored following decompaction modeling. Several models were tested: varying the lithology of the reef body and varying the initial porosities for each bed in the model. Based on the geometries observed in the models along with field outcrop observations, the decompacted low energy, muddy boundstone bioherms are clearly located downdip of high energy back reef shoaling facies, defining the overall architecture as a shoal rimmed platform. Employing basin modeling at this resolution along with LIDAR geometric portrayal and XRF lithologic validation provides insights in the original pre-compaction architecture. Establishing proper Permian reefal geometries are a first order step in properly constraining subsurface reservoir quality as viewed on seismic.