2D Restorations and Basin Modeling Provide Insight Into Formation Maturation

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 2021-5434, “Delaware Basin Wolfcamp Formation Maturation and Post-Permian Basin Evolution Based on 2D Restorations and Basin Modeling,” by Rachel Hoar, Mauro Becker, and Alan Yu, Texas A&M University. The paper has not been peer reviewed. _ The Permian Delaware Basin is a complex system in which the maturation of organic matter is affected by events not evident in the post-Permian available data. In this study, the authors aim to identify the effect of various geologic controls on hydrocarbon maturation in the Delaware Basin by restoring regional cross sections and performing simulations of organic-matter maturity. Integration of these data with seismic interpretation of the stratigraphic intervals present in the basin is used to refine the structural restorations and calibration of resulting 2D thermal models. Methods As a direct source of information for the initial evaluation of the post-Permian layers, surface geological maps, residual thickness maps, and structural information collected from the literature were examined. Next, four regional cross sections were selected and restudied with this objective. For the cross-sectional analysis, the data sets available were surficial geological and shallow-formation-thickness maps, subsurface seismic interpretation of the main stratigraphic intervals (proprietary data in the Delaware Basin sector), well logs, vitrinite reflectance evaluations, and apatite fission track analysis (AFTA) data available from the literature. In this Delaware Basin thermal-maturity study, the Wolfcamp formation was the unit selected and analyzed; however, the whole stratigraphic column needed to be included to produce the most-accurate and consistent model. With a major objective of this work being to evaluate the controls that post-Pennsylvanian depositional and erosional history have had on Delaware source-rock thermal maturity, this study focused on constraining the syn- and post-tectonic phase of the Ouachita/Marathon thrusting event. As such, the deformed rocks of the “known” phase (Carboniferous and older formations) were not considered, except for the paleogeomorphology resulted from the tectonic deformation and inherited by the lower Permian depositional phase. Previous work in the literature presented a comprehensive revision of the post-Permian sedimentary rocks and the patterns of erosion for the major post-Permian unconformities. The thickest post-Permian unit is the Triassic Dockum Group, a nonmarine red bed succession that paraconformably covers the Permian rocks. The Wichita paleoplain, an extensive unconformity, is recognized as an important exhumation and nondepositional period between the Triassic and the Cretaceous (Albian) in the area. Later Cretaceous carbonate strata also were deformed and exhumed at the Laramide contraction (Maastrichtian to Paleocene). The latest deformations that affected the area were the Miocene Basin Range event and Rio Grande Rift faulting complex. The work detailed in the complete paper details the cross section named the Diablo Platform/Central Basin Platform (CBP). All other cross sections followed the same methodology.