Lawrence Berkeley National Laboratory

Abstract Assessing large‐scale pressurization at the regional scale—a possible outcome of large subsurface storage applications such as wastewater injection and geological carbon sequestration—presents significant computational challenges. These challenges are particularly pronounced when accounting for complex geologic structures with multiple reservoir and caprock layers, fault zones, and wells. This study introduces a computationally efficient model that integrates single‐phase semi‐analytical solutions with a boundary element (BE) approach. The model simulates pressure propagation in multilayered 3D systems, including vertical faults, caprock, basement, and confining units. We apply this new model to a representative scenario involving CO 2 injection near a partially sealing fault with verification against an independent two‐phase flow model. Results demonstrate that our model accurately captures far‐field pressure responses and that, outside the CO 2 plume zone, pressure predictions from single‐phase and two‐phase models are nearly identical. This supports the use of single‐phase models like ours for efficient estimation of far‐field pressure changes. Additionally, we demonstrate its effectiveness at a large scale, incorporating multiple wells and faults. With its ability to represent multiple wells, fault zones, and geological heterogeneity, our model is well suited for assessments of basin‐scale pressurization. Its computational efficiency also makes it a promising tool for integration with optimization frameworks aimed at designing and managing injection strategies in faulted storage systems. Plain Language Summary Large‐scale injection of wastewater or CO 2 underground can increase pressure across sedimentary basins, potentially affecting wells and faults. Predicting these effects is challenging because of complex geology with multiple reservoir layers, caprock, and fault networks. We present a fast, efficient model that combines semi‐analytical solutions with a boundary element approach to simulate basin‐scale pressure changes from multiple wells and faults. The model accurately captures far‐field pressures and shows how flow through partially sealing or anisotropic faults influences pressure behavior. Its speed and flexibility make it a powerful tool for assessing basin‐scale injection, managing operations, and evaluating risks in faulted systems. Key Points Introduces a computationally efficient model combining semi‐analytical solutions with a boundary element method Enables simulation of multiple wells and faults across basin‐scale systems Demonstrates that flow through anisotropic fault zones critically affects injection‐induced pressure behavior in basins with vertically stacked reservoirs