Dallas Geological Luncheon

Permian Basin Wolfcamp Formation,

Geologic Characterization and Well Performance Drivers

Donny Loughry, Dan Lancaster, Paul Clarke, Alex Torres


The Midland Basin in West Texas represents a prolific petroleum province that historically produced from Wolfcampian to Leonardian-age, low permeability reservoir rocks, interbedded with source rock-prone shales.  These organic-rich shale sequences vary both vertically and laterally in terms of their overall thickness, depth, mineralogy, hydrocarbon storage, fluid saturations, thermal maturity, and pore-pressure gradients. Understanding the performance of horizontal wells targeting these successions is best achieved by a comprehensive knowledge of completion effectiveness, lateral lengths, configuration of multiple wellbores, and the interaction of various geologic drivers in combination.

In order to understand the impact of depositional processes, newly acquired core and an extensive log dataset was leveraged to construct a stratigraphic model for the Wolfcampian stratigraphy.  The result is a suite of interpretive geologic maps characterizing the main facies and depositional patterns of the Wolfcampian succession. Detailed description and mapping of lithofacies helped to characterize the reservoir potential of the Wolfcamp Shale.  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.

It is important to note that geologic drivers may vary independently and at differing resolutions. For example, changes in the level of thermal maturity vary over a long wavelength (basin scale), whereas changes in clay content vary over relatively short distances (1 to 3 miles) due to changes in sediment input and depositional processes. Because shale performance drivers are scale-dependent, only when the reservoir is characterized at the sub-regional scale is it possible to identify lower amplitude performance drivers.  This paper demonstrates the importance of identifying geologic performance drivers at multiple spatial scales and provides technical context for the emerging Wolfcamp Shale “sweet-spot” within the Midland Basin.

Mapping of pore pressure gradients and initial reservoir pressures, collected from nearly 2000 vertical wells with multi-stage completions, reveals that pore pressure (correlation to normalized well performance, R2=0.7) is a highly predictable regional-scale performance driver.  Examining horizontal performance within like pressure regimes reveals that secondary drivers such as facies type and bulk volume hydrocarbon are influential on local scales.  Understanding and mapping geomechanical barriers to hydraulic fracture propagation, along with primary and secondary performance drivers, allows for the delineation of geologically analogous areas within which well performance can be predicted with high confidence.  Within a given analogous area, tests (completion type, well spacing, stratigraphic target) for optimal development can be performed and applied throughout.

Location: Brookhaven College Geotechnology Institute
3939 Valley View Lane
Farmers Branch , TX 75244

Date: Sept. 12, 2017, 11:30 a.m. - Sept. 12, 2017, 1 p.m.