High-resolution visualization of flow velocities near frac-tips and flow interference of multi-fracked Eagle Ford wells, Brazos County, Texas

Abstract

This study outlines a workflow that combines reservoir characterization and decline curve-based production analysis with a physics-based drainage model that quantifies where fluid is drained from, based on the fracture treatment architecture. Decline curve analysis, applied to production data from four multi-fracked wells in the Eagle Ford formation (Brazos County, East Texas), provides forecasts for the estimated ultimate recovery (EUR). About 50% of EUR is realized in the first 1000 days (∼3 years) of the well-life. The drainage model shows where in the reservoir the produced fluid is actually drained from, based on the estimated reservoir parameters. This study includes several fundamental assessments of factors that may impact any drainage model, such as (1) the pressure front propagation time responsible for the depth of investigation, (2) pressure effects due to up-scaling of fracture patterns into a reduced number of fractures, and (3) interaction of fluid velocity patterns with pressure depletion zones. The drainage model for the Eagle Ford wells in our case study suggests that the first generation of hydraulic fractures recovers less than 1% of the original oil in place. With recovery factors so low, a repetitive schedule of periodic refracking the wells - provided the first refracks prove successful - is highly recommended.