Do deformation bands matter for flow? Insights from permeability measurements and flow simulations in porous carbonate rocks

Abstract

We investigate the permeability and flow effects of deformation bands in porous granular carbonate rocks in Malta and use results from flow simulations to discuss the practical implications of deformation bands in carbonate and siliciclastic reservoirs rocks in general. Image-and laboratory-based analyses of deformation bands show permeabilities that are 1 -2 orders of magnitude lower than the adjacent host rocks. Small-scale outcrop-based flow models (1 × 1 m) focus on the effect of deformation band on flow at the scale of individual bands. Two-phase flow simulations (water displacing oil) show that at the local scale a decrease in deformation band permeability led to increasing flow complexity, reduced and irregular waterfront propagation and reduction in sweep efficiency. A reduction in host rock permeability is associated with increased sensitivity to deformation bands. In low-permeable host rocks, a single magnitude-order reduction of deformation band permeability significantly delays flow, whereas in higher-permeable host rocks the effect is less pronounced. Hence, in some cases, deformation bands may represent a significant impediment to flow already when they are only 1 -2 orders of magnitude less permeable than host rock. Consequently, deformation bands may have greater practical implications than previously thought, particularly in reservoir rocks with moderate to low host rock permeability.

The Role of Stratigraphy and Loading History in Generating Complex Compaction Bands in Idealized Field‐Scale Settings

“…The importance of compaction bands is linked to many geophysical and geo‐engineering applications, including fault mechanics, hydrocarbons extraction (Hettema et al., 2002), aquifer production (Deng et al., 2015; Sternlof et al., 2006; Zuluaga et al., 2016), and underground CO 2 sequestration (Raduha et al., 2016; Rass et al., 2017; Torabi et al., 2015b; Wawersik et al., 2001). In fact, these structures constitute zones of energy dissipation in faulting systems, and, because of their low permeability (David et al., 2011; Pons et al., 2011; Sternlof et al., 2006; Sun et al., 2011), can impact the local and regional hydraulic conductivity of geological reservoirs (Antonellini et al., 2014; Ballas et al., 2012; Rotevatn et al., 2017; Zuluaga et al., 2016).…”

Dynamic Evolution of Permeability in Response to Chemo‐Mechanical Compaction

“…The overall chemo‐mechanical process forms a localized compaction band, which is perpendicular to the loading direction acting as a structural heterogeneity. Pore connectivity is thus retained only in the marginal salt layers, thus inducing permeability anisotropy (Figures a, d, supporting information Figure S4) (Olsen (); Faulkner & Rutter (); Clennell et al (); Bayesteh & Mirghasemi (); Rotevatn et al ()).…”

The Relationship between Fluid Flow, Structures, and Depositional Architecture in Sedimentary Rocks: An Example-Based Overview

“…(3) Deformation bands: described as tabular, millimeterwide zones of localized but nondiscrete and distributed shear and/or compaction, and are typically low-permeable structures (generally 2-3, but occa-sionally up to 6 orders of magnitude lower permeability than host rock) that adversely affect flow properties [2,[46][47][48][49][50][51] (4) Iron oxide precipitates (IOPs): used herein as a term to cover both Liesegang-type reaction-diffusion systems (Liesegang bands, e.g., [39]) and other iron oxide deposits (e.g., [20,52]). IOPs are a common by-product of fluid flow in rocks such as sandstone, limestone, and mudstone.…”