Seismic attribute analyses of lower Permian (Wolfcampian-Leonardian) carbonate buildups, SW Midland, Texas

Abstract

A trend of Wolfcampian-Leonardian carbonate buildups is located in the southwestern Midland Basin, Upton County, Texas. The buildup trend is located east of the eastern faulted margin of the Central Basin Platform and north of the Ozona Arch. Carbonate deposition began during lowstand times, within or just below wave base. In the Southwestern Midland Basin, the Wolfcampian-Leonardian carbonate interval is lithologically heterogeneous due to the presence of abundant lithoclastic debris that was shed from the uplifted Central Basin Platform. The lithologic heterogeneity makes it difficult to identify the buildups on seismic profiles. Several inferred buildups have been drilled in the past, but many boreholes only penetrated lithoclastic facies, not true buildup facies. Analyses of various seismic attributes were conducted for the Wolfcampian-Leonardian interval in the SW Midland Basin in an attempt to improve the recognition and imaging of the carbonate buildups. The objective was to identify a set of attributes that directly indicate the buildup locations. After extensive trial of various attributes, the variance attribute was selected as the optimum seismic attribute. The resultant 3D variance volume was used to detect the buildup locations, and some aspects of their internal stratigraphy, and to establish the fault framework in the Amacker survey. The instantaneous frequency attribute, combined with the variance attribute was also marginally useful for imaging the buildups. The variance attribute and instantaneous frequency were compared. Images generated from the variance attribute are better than those generated using the instantaneous frequency because on these images, it is possible to localize the buildups. The instantaneous frequency attribute combined with the variance attribute allows recognition of lithologic heterogeneities inside the buildup interval.