A Fast Workflow for Uncertainty Assessment of Well Spacing and Pad Sequence in the Permian Basin Available to Purchase

Determination of well spacing and pad sequence are critical factors for maximizing production and yet remain challenging in unconventional plays. Data analysis of existing well performance provides an extensive knowledge base of ever changing designs, impact on performance and locations, however, integrated modeling has gained more attention despite the increase in time and effort. The scope of this paper is to illustrate a practical workflow alternative for rigorous multiple uncertainty analysis and optimization study that have been successfully applied to our unconventional reservoir factory-model development in the Permian Basin.

Considering scenarios of multiple wells and pads with different sequences of completions and production, the workflow consists of three key phases. First, complex hydraulic fractures with a discrete naturally fractured network is modeled and converted to an unstructured reservoir simulation grid fitting simulator. The simulated well production performances then serve as a reference case. Second, the hydraulic fractures are further characterized by a logarithmic local grid refinement approach through an in-house reservoir simulation package designed for creating multiple realizations for history matching, uncertainty assessment, and optimization study, given reservoir heterogeneity and fracture variability. The whole section with different well spacing and pad sequence is then evaluated. Third, an in-house uncertainty analysis package is linked to both hydraulic fracture modeling and the in-house reservoir simulation platform for a variety of parameters including pad sequencing strategy/timing, well spacing, economic limit, matrix permeability, fluid type, and drawdown pressure.

This workflow is fast and systematic while capturing the fracture geometry from complex hydraulic fracture modeling. Results from recent Midland Basin evaluations demonstrated that well interference should be considered at section level with all the wells to ensure proper section EUR consideration and different scenarios of pad sequences noticeably affect the section EUR, depending on the time differences, matrix permeability, fluid type and drawdown management.

The novelty of this workflow is that 100s of realizations of different scenarios are created with the run time that is much faster yet results very similar to the more complex model’s result.