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Permian Basin Case Study: Frac Design Using SciCat® Stress
Far-field stress variability from SciCat® is driven by in-situ 3D seismic geomechanics defined by lithofacies and mechanical stratigraphy of the rocks which ultimately governs fracture geometry including height and length.
For example, stacked horizontal wellbores landed in the Lower Spraberry formation, seen here from the Permian Basin, are typically separated vertically by just 200 ft. with stress differentials greater than 1,200 psi (red to purple). The black curves define individual vertical stress profiles extracted from the same section which are vertically sampled at 1 ft.
The upper landing is characteristic of higher stress rocks due to the addition of clay and organics by volume warranting a tighter spacing of 200 ft. totaling 22 stages. The lower "landing2" zone is characteristic of lower stress (more brittle) due to proportionally less clay and more carbonates, thus warranting a relatively wider spacing of 250 ft. totaling just 17 stages.
With less frac stages, the lower landing completion costs are reduced by ~$350,000 per well, a significant savings for a 12-well pad and without compromising production. Optimal stage spacing from stress heterogeneity can be confirmed using fracture modeling as seen below.
SciCat® Stress is Input Directly into Fracture Simulation
E&P’s operating tight oil and gas plays continue to implement development strategies that involve cookie-cutter completion designs that use identical geometric stage / cluster spacing. Such development strategies fail to account for changes in geology, specifically minimum stress heterogeneity near wellbore and far-field which governs stimulated fracture complexity. The measured stress can be input directly into 3D fracture geometry simulators like GOHFER® .
The same Lower Spraberry example from the Permian shows stacked horizontal wellbores with stress heterogeneity measured in-situ by seismic geomechanics (bottom section), contrary to interpolated stress from vertical logs without seismic which fails to account for the vertical stress differential separating the stacked wellbores (middle section). Without accounting for stress heterogeneity, modeled fracture lengths appear equal and the stacked wellbores would have otherwise been completed identically at significantly increased cost.
Stress Heterogeneity for Optimal Completions Design
Near wellbore minimum horizontal stress from SciCat® can be input directly into completion modeling software in 1D and 3D space for optimal stage and cluster spacing determined by stress differentials for enhanced treatment sensitivity analysis that is data driven, resulting in optimized fracture stimulation with mitigation of stage-to-stage and interwell frac hits. Example here is from CORDAX ® using stress input from SciCat.