Mechanical Stratigraphy and Natural Deformation in the Permian Strata of West and Central Texas and New Mexico, 20-R8511
David A. Ferrill
Kevin J. Smart
Ronald N. McGinnis
Alan P. Morris
Inclusive Dates: 01/05/15 – 05/05/15
Background — With rapid development of self-sourced (often referred to as "shale") and low-permeability reservoirs, work focusing on mechanical stratigraphy, structural geology, and geomechanical analysis of these plays has expanded. With a shift in emphasis from drilling and production from the highly productive Eagle Ford Formation to the Permian Basin, there is a growing need to understand the Permian reservoir strata, specifically, the mechanical characteristics, natural deformation, and tectonic setting of relevant strata within the production areas. This information is important to making cost-effective decisions regarding vertical placement, direction, spacing, and completion strategies of horizontal wells ("laterals").
Approach — The objectives of this project were to locate geologic outcrops of Permian strata that could serve as suitable analogs for reservoir intervals and deformation styles within the Permian Basin, and conduct reconnaissance-level field characterization activities to generate a data set suitable for demonstrating the outcrop-analog relevance to potential joint industry project member companies and for use in field seminars for the oil industry. We started by compiling data on geologic outcrops of Permian strata in Texas and New Mexico along with structural and tectonic data throughout the region. Reconnaissance-level characterization was then conducted at suitable outcrop exposures to document lithology and thickness of bedding; collect representative Schmidt hammer rebound measurements to represent mechanical stratigraphy; and measure structures such as bedding, faults, folds, and fractures.
Accomplishments — Project accomplishments included developing an overview presentation summarizing the suite of geologic outcrops, including key stratigraphic and structural features; building an ArcGIS database of outcrop locations and data as the foundation for a new joint industry project; and preparing regional deformation maps showing the distribution of fault, joints, and folds and their geologic context. Surface exposures of lithologically varied Permian strata around the southern, western, and eastern margins of the Permian Basin in west Texas reveal a broad spectrum of bore-hole scale deformation styles that reflect their tectonic histories and that apply to both conventional (limestone and sandstone) reservoirs and unconventional (fine-grained mudrock) reservoir facies of the Permian Basin.
Collectively, data gathered from these exposures document that structural styles vary with tectonic context around the margins of the Permian Basin, and document a systematic 30-degree rotation of dominant strike trends around the basin. These results are directly relevant to predicting the distribution and style of sub-surface, small-scale deformation features that influence the permeability architecture and the potential for induced hydraulic fracturing of hydrocarbon reservoirs throughout the Permian Basin. An invited abstract and oral presentation were prepared for the West Texas Geological Society 2015 Fall Symposium (Midland, Texas), and an abstract was prepared and submitted for the 2016 Annual Conference and Exhibition of the American Association of Petroleum Geologists (Calgary, Alberta).