Small‐Scale Capillary Heterogeneity Linked to Rapid Plume Migration During CO2 Storage

Samuel J Jackson,Samuel Krevor

doi:10.1029/2020gl088616

Abstract

AbstractUnpredicted, rapid plume elongation has been observed at subsurface CO2 storage projects worldwide, exemplified by the Sleipner project. We show that conventionally ignored centimeter‐meter scale heterogeneity in capillary pressure characteristics can manifest as rapid field‐scale, decameter‐kilometer, plume migration. We analyze the effect in the Goldeneye field, UK, a proposed storage site with a unique combination of sample/data accessibility and generality as an archetype sandstone reservoir. We overcome previous barriers by characterizing in greater detail over larger scales—the 65 m reservoir height at cm‐m resolution—and through use of an upscaling scheme which resolves small‐scale heterogeneity impacts in field‐scale simulations. These models reveal that significant early time retardation of buoyantly rising CO2 plumes is followed by rapid migration under the caprock in the presence of anisotropic, layered heterogeneities. Lateral migration speeds can be enhanced by 200%, placing first‐order controls on fluid flow and providing a mechanistic explanation for field observations.

Highlights

CO2 plume migration remains difficult to accurately simulate and predict at industrial scale, subsurface storage projects
We show that conventionally ignored centimetre-metre scale heterogeneity in capillary pressure characteristics can manifest as rapid field-scale, decametre-kilometre, plume migration
Past work on nonaqueous phase liquid (NAPL) contamination has shown that these heterogeneities can result in significant enhancements in lateral migration; with NAPL, this can occur with a sinking dense contaminant plume (Braun et al, 2005)

Summary

Introduction

CO2 plume migration remains difficult to accurately simulate and predict at industrial scale, subsurface storage projects. Williams & Chadwick, 2012); In Salah, Algeria (Ringrose et al, 2013); Frio stage I and II projects, Texas, USA (Hovorka et al, 2006; Daley et al, 2011); Cranfield, Mississippi, USA (Hosseini et al, 2013); and the Otway stage 2 project, Otway, Victoria, Australia (Dance et al, 2019) In all of these examples, the seismically imaged CO2 plume has extended laterally away from injection points along pathways and at rates neither predicted nor matched by conventional approaches to reservoir simulation. Past work on nonaqueous phase liquid (NAPL) contamination has shown that these heterogeneities can result in significant enhancements in lateral migration; with NAPL, this can occur with a sinking dense contaminant plume (Braun et al, 2005). This is used in the creation of numerical models in an upscaling workflow that allows us to evaluate the kilometre-scale impacts of the fine-scale heterogeneity in a model of the Goldeneye field

Scaling analysis for small-scale heterogeneities

Findings

The impact of small-scale heterogeneities on lateral plume migration