--> Geologic Characterization and Facies Analysis of the Wolfcampian/Leonardian Succession in the Midland Basin, West Texas, USA: Impact on Horizontal Well Performance

AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

Geologic Characterization and Facies Analysis of the Wolfcampian/Leonardian Succession in the Midland Basin, West Texas, USA: Impact on Horizontal Well Performance

Abstract

The Midland Basin in West Texas represents a prolific petroleum province that historically produced from “low permeability/tight” reservoir rocks, interbedded with source rock-prone shales. By leveraging newly acquired core and log data, a high-resolution stratigraphic model was constructed for the Wolfcampian and Leonardian stratigraphy. Detailed facies analysis and mapping provide insight to the depositional environments associated with this deep-water, mixed carbonate-siliciclastic system. The influence of basin margin mass-transport-complexes, pro-delta terrigenous clay facies, and organic-rich facies act as performance drivers in the Wolfcamp Shale play demonstrated by a data set of 178 contemporary horizontal oil wells. Detailed whole core description (7 proprietary cores/4,622 ft.) provided a lithofacies classification scheme and paleo-depositional framework, constrained further by multiple FMI logs. Propagation of these facies regionally was undertaken by application of: (1) an extensive well-log database, (2) 3D seismic data, and (3) geo-cellular models. The result is a suite of interpretive geologic maps characterizing the main facies and depositional patterns of the Wolfcampian/Leonardian succession. Mass-transport complexes, of which the distribution was governed by slope-angle and geometry of the basin margins, dominate the Lower Wolfcamp (WCMP-B3). These deposits may form during low-stand conditions and are generally non-productive, commonly cited as frac-barriers or baffles. The Middle Wolfcamp (WCMP-B2/B1) is a “transgressive” succession, with inter-bedded distal turbidites, debrites and organic rich facies with a maximum-flood (WCMP-B1) capping the succession. The succeeding Upper Wolfcamp (WCMP-A) is dominated by thin-bedded carbonate turbidities, related to high-stand shedding from the basin margin as carbonate productivity on the platform increases. Facies distribution indicates minimal tectonic impact throughout this “lower-middle-upper” transition. Detailed description and mapping of lithofacies helped to characterize the reservoir potential of the Wolfcamp Shale and guide our ongoing development strategy. The distribution for mass-transport complexes and clay-prone facies is significant when predicting hydraulic fracture propagation and containment as well as potential communication between neighboring wells. These impact horizontal well placement, spacing, timing of stacked wells, and overall field development.