Hudson, Samuel M.¹, Tim Lawton², Brenda Buck¹ 
(1) University of Nevada Las Vegas, Las Vegas, NV 
(2) New Mexico State University, Las Cruces, NM 

ABSTRACT: New Geochemical Evidence of Hydrocarbons Along the La Popa Salt Weld, La Popa Basin, Northeastern Mexico

New geochemical data indicate concentration of hydrocarbons along the La Popa salt weld in northeastern Mexico, reinforcing the idea that salt diapirs and welds significantly affect the migration pathways of hydrocarbons. Geochemical testing (TOC, Rock-Eval, and molecular organic geochemistry) of samples taken along the length of the weld indicate that at least some of this material is not in situ, but has migrated along the weld. TOC values between 0.5 and 1.0 weight percent, although not high from a production standpoint, do indicate that organic carbon is present. Rock-Eval results from the majority of these samples show S1peaks that exceed the corresponding S2 peaks, indicating that the organic matter migrated to its current position along the weld. Molecular organic geochemistry for the same samples, including biomarker analysis, reveals hydrocarbon compounds with mature signatures. Many of the samples show significant degradation, probably as a result of near-surface exposure or advanced thermal maturity. 
Biomarkers within samples collected along the weld suggest a clay-rich source rock for the hydrocarbons. None of the potential source rocks within the section yielded results indicative of a good source rock. However, we extracted organic matter from five of the organic lean source rocks and completed biomarker analyses on them. Of the samples analyzed, the Parras Shale and Upper Mudstone Member of the Potrerillos Formation are most similar to the migrated material based on biomarker analysis. In addition, our vitrinite reflectance data suggest that these units are within the peak- to late-oil generation window.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.