Integrating Pressure Understanding with Geology in Unconventionals for Development Optimization – Case Study from Haynesville Basin

Abstract The Haynesville basin currently supplies ∼15% of total natural gas production in the United States. Demand is expected to rise significantly by 2030 to meet domestic needs and support growing LNG opportunities. ExxonMobil holds a contiguous acreage position in the southern part of the basin that has not been fully developed. In this study, we present an innovative workflow which integrates pressure and geologic data to predict production trends and optimize development in the Haynesville Basin. To understand pressure trends across the basin, we mapped reservoir pressures from well flowback data and seismic velocities across the field. We also mapped breakdown pressures recorded from fracking operations to understand the correlation with reservoir pressures, structural features and production performance to identify regions favorable for development. Our data from the pressure mapping study suggests that the damage zones associated with listric fault complexes cause degradation in reservoir and breakdown pressures resulting in degraded production performance in wells drilled adjacent to the faults. Breakdown Pressures can also tend to decrease due to presence of natural fractures associated with fault zones without impacting reservoir pressures, suggesting that regions with high reservoir pressures and low breakdown pressures are the best areas for development. The second part of this study focused on understanding the cause and effect of parent-child interactions, specifically the impact of modern well completions (2018 or newer) near vintage completions (2010-2014), to assess the impact on well performance for both completion types. Parent-Child interactions analyzed in the field using breakdown pressures and production trends suggests both intra-bench (Haynesville-Haynesville and Bossier-Bossier) and inter-bench (Haynesville-Bossier) communication resulting in as much as ∼5-15% production uplift in older vintage parent wells without impacting performance on child wells. This is a unique behavior observed in the Haynesville Basin contrary to the parent-child effects generally observed in unconventional plays resulting in performance degradation. We suggest that production uplift on older well vintages occur due to 1) new stimulated rock volume created near the parent wellbore in case of intra-bench interactions, and 2) reservoir re-pressurization due to child well completion in case of inter-bench and wider spaced intra-bench interactions. In the former case, fractures from parent and child producers in the same formation may grow together forming integrated networks to stimulate a larger rock volume and drain additional gas from the under-stimulated parent well without impacting the performance of the child well. In the latter case, it is unlikely that parent and child fractures become connected, and therefore increased productivity in the parent wells is likely the result of elevated pore pressures. The latter case phenomenon is the possible explanation of inter-bench communication between Haynesville and Bossier formations and intra-bench communication observed at wider spacing (3000-4000 feet). We also observed that the uplift in the vintage parent wells increases as a function of distance from the child well suggesting strong communication at lower distances. Interpreting under-utilized datasets in unconventional domain (breakdown pressures, seismic velocities, etc.) and integrating it with fundamental geoscience interpretation has been a key driver in this approach. Observations discussed in this paper can help optimize our development plans in terms of 1) correctly sequencing and down-spacing the wells to capture the additional value from the under-stimulated vintage completions, and 2) incorporating the production uplift in pre-drill and post-drill well economic analysis. Identifying such opportunities and integrating them with our development strategy can help optimize development plans and maximize value.