Deformation bands and their impact on fluid flow in sandstone reservoirs: the role of natural thickness variations

Abstract

Cataclastic deformation bands, which are common in sandstone reservoirs and which may negatively affect fluid flow, are generally associated with notable thickness variations. It has been suggested previously that such thickness variations represent an important control on how deformation bands affect fluid flow. The effects of such thickness variations are tested in this study though statistical analysis and fluid flow simulation of an array of cataclastic deformation bands in Cretaceous sandstones in in the Bassin de Sud‐Est in Provence, France. Spatial outcrop data are statistically analyzed for incorporation in flow simulation models, and numerical simulations are used to investigate the effects of notable thickness variations on how the deformation bands influence effective permeability and flow dynamics. A suite of simulations is performed using a combination of fine‐scale and coarse‐scale grids, revealing that the effective permeability of the simulated reservoir is reduced by a factor of 15–25. More interestingly, the simulations further demonstrated that, as compared to the overall effect of the deformation band array on fluid flow, thickness variations along the bands proved to have negligible effects only. Thus, our simulations indicate that the configuration and connectivity of the deformation bands, together with the permeability contrast between the bands and the host rock and the mean band thickness, are the most important controls on the effective permeability. Our findings represent new insight into the influence of deformation bands on fluid flow in subsurface aquifers and reservoirs, indicating that thickness variations of individual deformation bands are of less significance than previously thought.

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

“…The reason for these differences is that the introduction of permeability heterogeneity in the models results in slower and more irregular waterfront propagation, compared to models where deformation bands are absent. Thus, at the local scale, deformation bands clearly affect flow patterns and the nature of waterfront propagation; similar finds were reported by Rotevatn et al (2013) for arrays of contractional deformation bands in porous siliciclastic rocks. Deformation band effects on the speed of flow Fachri et al (2013), based on flow simulations of larger-scale reservoir models of relay zones in siliciclastics with deformation band damage zones, reported a link between increasingly complex waterfront shapes (as a function of decreasing deformation band permeability) and a decrease in the speed at which fluid fronts propagate.…”

“…Similar variability has been shown for deformation bands in porous sandstones, and Torabi & Fossen (2009) argued that spatial variability of permeability or thickness within deformation bands may reduce their ability to retard flow. Rotevatn et al (2013) tested this assertion and demonstrated that the effects of such variability on aquifer-scale flow are limited; rather, deformation band connectivity as well as permeability contrast were identified as the most important controls on effective permeability and flow. Figure 4d shows a comparison of the relation between porosity and permeability in sandstone (data from Torabi et al 2013) and carbonate rocks (data from this study) both for host rock and deformation bands.…”

“…Deformation bands have, therefore, been suspected of causing production problems within siliciclastic subsurface reservoirs (Lewis & Couples 1993;Olsson et al 2004), although this has been difficult to prove given their small-scale nature. In response to this, previous studies have attempted to quantify and simulate the effect of deformation bands on fluid flow dynamics and production performance (Matthäi et al 1998;Sternlof et al 2006;Fossen & Bale 2007;Rotevatn et al 2009Rotevatn et al , 2013Rotevatn & Fossen 2011;Zuluaga et al 2016). In general these studies have demonstrated that deformation bands in siliciclastic reservoirs or aquifers may cause (i) perturbed flow patterns, leading to more tortuous fluid flow (Rotevatn et al 2009;Zuluaga et al 2016), (ii) pressure compartmentalization (Rotevatn & Fossen 2011), (iii) improved sweep efficiency (Rotevatn et al 2009;Zuluaga et al 2016), (iv) delayed water breakthrough (Rotevatn et al 2009), (v) anisotropic reservoir flow properties (Sternlof et al 2006), (vi) variable production efficiency (Sternlof et al 2006;Rotevatn et al 2009) and (vii) reduced effective permeability within the reservoir (Fossen & Bale 2007;Rotevatn et al 2013).…”

Permeability Evolution and Particle Size Distribution of Saturated Crushed Sandstone under Compression

“…Since then, many experiments on the water flow in fractured rocks had been carried out [1][2][3][24][25][26][27][28]. Specifically, Miao et al [1] analyzed the seepage properties of broken sandstone with different porosities; Ma et al [2,3] obtained the relationship between the permeability and variable grain diameters under variable axial displacements.…”

Sequential growth of deformation bands in carbonate grainstones in the hangingwall of an active growth fault: Implications for deformation mechanisms in different tectonic regimes

“…It is also well-established that deformation bands in porous sandstones may be associated with a bulk reduction in permeability in the range of 1e3 (occasionally up to six) orders of magnitude relative to host rock (e.g. Taylor and Pollard, 2000;Sternlof et al, 2004;Fossen et al, 2007;Rotevatn et al, 2008;Ballas et al, 2012;Rotevatn et al 2013); for pure compaction bands (sensu Mollema and Antonellini, 1996) in porous sandstones, up to 3 magnitude order permeability reductions have been reported Deng et al, 2015).…”