Publicly-available fault data for the Delaware basin is used to simulate a detailed map of maximum stress direction at a scale of 1000ft x 1000ft throughout the Delaware basin. The resulting maps highlight the complexity of stress fields in the Delaware basin and the importance of accounting for the interaction of entire fault systems with regional stresses. This underscores a dire need for the industry to better quantify structural features in and around unconventional reservoirs. When commercially-available seismic data is used for a refined interpretation of the structural features that affect the stress field, geomechanical models can be refined to provide valuable information at the well and pad scale to influence and optimize well spacing and completion decisions to minimize frac hits and other undesirable well interferences. Multiple data collected at the wells are used to validate the predicted stress orientation and their impact on the performance of hydraulic fracturing jobs. These results were enabled by the use of validated geomechanical modeling that is able to easily handle the faults and natural fractures. This is implemented by using the material point method to address the computational challenges introduced by the presence of these earth discontinuities in the general continuum mechanics equations representing the static and dynamic variations of stress in unconventional reservoirs.

Introduction

Production of unconventional wells is dictated by both the geological (resource) and geomechanical (recoverability) properties of the reservoir. The geomechanics of a reservoir can be broken down into the rock mechanical properties, which near the wellbore primarily control fracture initiation potential, and the current stress state, which away from the wellbore controls the propagation of successfully induced hydraulic fractures and their interaction with natural fractures and layer interfaces. The consequential properties of the stress state can be further refined and represented as the differential stresses and the maximum horizontal stress orientation. In the Permian basin where a normal fault regime is common, it is critical that an unconventional horizontal well be drilled nearly perpendicular to the maximum horizontal stress direction (MHSD) in order to induce transverse hydraulic fractures and thereby maximize its stimulated reservoir volume (SRV). Additionally, maximum horizontal stress orientation is a major control on fault stability and a primary concern when quantifying the induced seismicity potential in a given area. Stress rotations have been documented at regional, basin, field, and pad scales (Umholtz & Ouenes, 2015, Umholtz & Ouenes, 2016, Ouenes et al., 2016). What cannot be ignored, is the reciprocal relationship between fault networks and stress fields. While fault quantification is readily available at field scales (when seismic data exists), operators rarely disclose these interpretations to be used in comprehensive regional studies. This study will initially focus on quantifying stress rotations at basin and county scales using publicly-available data, and further refine these estimates by integrating interpreted fault information from readily-available seismic data.

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