Dynamic investigation of the effect of a relay ramp on simulated fluid flow: geocellular modelling of the Delicate Arch Ramp, Utah

Abstract

A fluid flow simulation study was performed to investigate potential contrasts in reservoir performance between models displaying a soft-linked relay ramp vs. models with a continuous fault. The relay ramp model is based on a well-exposed outcrop analogue -the Delicate Arch Ramp, Arches National Park, Utah. In outcrop, the relay ramp exhibits a pervasive system of cataclastic deformation bands, which were mapped and incorporated into the reservoir simulation models. Several models were simulated, using deformation-band permeability as the main variable tested. Results show that when compared to flow across continuous faults, the presence of soft-linked relay ramps enhances net flow across the fault zone in all tested scenarios. Comparing models with deformation bands to the model that includes the ramp but no deformation bands illustrates that, although having an impact on flow tortuosity and sweep efficiency, deformation bands must have a very low permeability and be numerous before having a negative impact on recovery. Deformation bands with midrange permeabilities were shown to have a positive effect on recovery in the relay models, as they increase flow tortuosity and enhance sweep, causing later water breakthrough and prolonging production. Using very low-permeable deformation bands in the same models caused extremely poor pressure communication between the fault-breached compartments, despite the geometric connectivity provided by the sub-continuous relay beds.

From mechanical modeling to seismic imaging of faults: A synthetic workflow to study the impact of faults on seismic

“…We use the well detailed geomodel of the Delicate Arch Ramp in Utah made by Rotevatn et al (2009). Initial host rock properties of the sandstone are based on measurements from Antonellini and Aydin (1994): porosity 28%, horizontal permeability 1000mD and vertical permeability 100mD (Rotevatn et al, 2009).…”

“…We use the well detailed geomodel of the Delicate Arch Ramp in Utah made by Rotevatn et al (2009). Initial host rock properties of the sandstone are based on measurements from Antonellini and Aydin (1994): porosity 28%, horizontal permeability 1000mD and vertical permeability 100mD (Rotevatn et al, 2009). Based on the frequency of deformation bands within each cell of the geomodel (Rotevatn et al, 2009), these petrophysical properties are modified due to faulting, as following:…”

“…To compute the elastic properties after faulting, in papers 1 and 2, we modify the initial/base elastic properties (VP, VS and density) based on the finite strain of the DEM using a simple empirical relationship. In paper 3, the properties of the sandstone reservoir are modified by the frequency of deformation bands (Rotevatn et al, 2009) and the fluid content during simulated production.…”

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

“…Given the model choices (1 layer, vertically continuous deformation bands), our approach is largely two-dimensional, which is a fair approximation of flow across a network of bands confined to one geological layer (e.g. Rotevatn et al 2009). The model resulting from this semi-discrete inflated approach very closely replicates the exact geometry of the deformation band as mapped in outcrop (compare Fig.…”

“…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).…”