Subcore Scale Fluid Flow Behavior in a Sandstone With Cataclastic Deformation Bands

Abstract

Accurate determination of petrophysical and multiphase flow properties in sandstones is necessary for reservoir characterization, for instance for carbon dioxide and hydrogen storage in geological formations or for enhanced oil recovery. Several studies have examined the effect of heterogeneities, such as fractures, bedding planes, and laminae, on core-scale fluid flow. However, the influence of deformation bands that commonly occur in high porosity sandstones is poorly understood. In this study, we consider a core sample of Navajo sandstone characterized by diagonally oriented deformation bands and two laminae perpendicular to the core axis, as determined from micro X-ray computed tomography (micro-CT). Positron emission tomography is used to derive the single phase hydrodynamic properties of the core. A CO 2 drainage experiment is conducted in the water-saturated core and imaged with a medical X-ray CT scanner. Medical CT enables CO 2 saturation quantification with increasing CO 2 injection rate. Experimental results and the accompanying numerical simulations indicate that both the laminae and the deformation bands act as capillary barriers, with the laminae forming weaker capillary barriers than the deformation bands. The deformation bands have lower permeability and porosity due to grain crushing, and a very high capillary entry pressure that inhibits CO 2 migration across the bands. At the reservoir scale, deformation bands form conjugate sets and are often present in thick anastomosing clusters that define lozenge-shaped compartments. These findings have important consequences for subsurface fluid flow. For example, the presence of deformation bands may reduce the storage capacity and injectivity in carbon storage reservoirs.

Structural control on fluid flow and shallow diagenesis: insights from calcite cementation along deformation bands in porous sandstones

“…The mechanisms discussed above explain how and why cement precipitation would occur within the band and in its proximity, as observed on-site. Our field observations confirm the theoretical and flow simulations as well as the analog experiments, which demonstrated that DBs can negatively affect the fluid flow in porous sandstones (e.g., Rotevatn and Fossen, 2011;Antonellini et al, 2014;Romano et al, 2020) and enhance cement precipitation (e.g., Lander et al, 2009;Williams et al, 2015).…”

“…The petrophysical properties (porosity, permeability, capillary entry pressure) of DBs influence fluid flow and localize diagenesis and cement precipitation. Cataclastic DBs increase flow tortuosity in reservoirs and produce capillary barriers that severely baffle the flow at the reservoir scale and limit cross-flow between host rock compartments (Harper and Mofta, 1985;Edwards et al, 1993;Lewis and Couples, 1993;Leveille et al, 1997;Gibson, 1998;Antonellini et al, 1999Antonellini et al, , 2014Sternlof et al, 2004;Rotevatn and Fossen, 2011;Ballas et al, 2012;Medici et al, 2019;Romano et al, 2020). Smaller pores within bands result in higher capillary forces than in the host rock.…”

“…In most cases, however, they are associated with significant porosity and permeability reduction relative to the host rock Fisher and Knipe, 1998;Shipton et al, 2002;Sternlof et al, 2004;Balsamo and Storti, 2010;Ballas et al, 2015;Fossen et al, 2017;Del Sole and Antonellini, 2019), thus inducing permeability anisotropy and reservoir compartmentalization. This might negatively impact production from faulted siliciclastic systems (Edwards et al, 1993;Lewis and Couples, 1993;Leveille et al, 1997;Antonellini et al, 1999;Wilkins et al, 2019) and flow-based models and simulations (Sternlof et al, 2004;Rotevatn and Fossen, 2011;Fachri et al, 2013;Qu and Tveranger, 2016;Romano et al, 2020).…”

EXTREME CAPILLARY HETEROGENEITIES AND IN SITU FLUID COMPARTMENTALIZATION DUE TO CLUSTERS OF DEFORMATION BANDS IN SANDSTONES

“…In situ characterization studies of sub-core scale multiphase fluid properties in heterogeneous rocks to date have typically focused on simple structures, such as fractures, bedding planes, laminae (Alemu et al, 2013;Hingerl et al, 2016;Krevor et al, 2011;Li et al, 2020;Ni et al, 2019;Shi et al, 2011) and individual deformation bands (Romano et al, 2020). However, a combination of geologic structures is often present in the subsurface, leading to more extreme heterogeneities with complex geometries.…”

“…In all cataclastic bands, fine crushed grains fill available pore spaces, decreasing porosity and permeability of the host rock by several orders of magnitude (Aydin and Johnson, 1978;Antonellini and Aydin, 1994;Ballas et al, 2015;Deng et al, 2015;Fossen et al, 2007;Taylor and Polland, 2000). Cataclastic deformation bands are usually characterized by higher capillary entry pressure values when compared to the surrounding rock (Romano et al, 2020;Torabi et al, 2013;data from Fisher et al, 2005, summarised in van Ojik et al, 2020). A single deformation band is only able to accommodate few millimeters, or rarely a few centimeters of displacement (Aydin and Johnson, 1978).…”