Effective flow properties heterolithic, cross-bedded tidal sandstones: Part 2. Flow simulation

Abstract

Here we investigate the impact of mudstone drape distribution on the effective permeability 26 of heterolithic, cross-bedded tidal sandstones using three-dimensional (3D) surface-based 27 "mini-models" that capture the geometry of cross-beds at an appropriate scale. The impact 28 of seven geometric parameters has been determined: (1) mudstone fraction, (2) sandstone 29 laminae thickness, (3) mudstone drape continuity, (4) toeset dip, (5) climb angle of foreset-30 toeset surfaces, (6) proportion of foresets to toesets, and (7) trough or tabular geometry of 31 the cross-beds. 32We begin by identifying a representative elementary volume (REV) of 1 m 3 , confirming 33 that the model volume of 9 m 3 yields representative permeability values. Effective 34 permeability decreases as the mudstone fraction increases, and is highly anisotropic: vertical 35 permeability falls to c. 0.5% of the sandstone permeability at a mudstone fraction of 25%, 36 while the horizontal permeability falls to c. 5% and c. 50% of the sandstone value in the dip 37 (across mudstone drapes) and strike (parallel to mudstone drapes) directions, respectively. 38There is considerable spread around these values, because each parameter investigated can 39 significantly impact effective permeability, with the impact depending upon the flow 40 direction and mudstone fraction. The results yield improved estimates of effective 41 permeability in heterolithic, cross-bedded sandstones, which can be used to populate 42 reservoir-scale model grid blocks using estimates of mudstone fraction and geometrical 43 parameters obtained from core and outcrop-analog data. 44 45

A novel flow-based geometrical upscaling method to represent three-dimensional complex sub-seismic fault zone structures into a dynamic reservoir model

“…pseudo relative permeability and pseudo capillary pressure) upscaling procedures 1,3–8 for dealing with small-scale volume-filling petrophysical variability. Small-scale geometrical features which occupy only a small fraction of the volume they are contained in, such as sub-seismic faults or shale-draped sedimentary structures, have received less attention and if they are considered in upscaling studies it is generally only with reference to establishing effective permeabilities due to low permeability fault rock or shale drapes 9–11 . However, low permeability fault rock is not the only characteristic of faults to consider, and shear displacements across sub-seismic faults can be very significant on reservoir flow.…”

Introduction to the sedimentology of paralic reservoirs: recent advances

“…Such intercalations have repeatedly been shown to have a significant impact on fluid flow (e.g. Jackson et al 2005;Ringrose et al 2005) and remain an area of active research (Massart et al 2016). Accordingly, the second group of papers in the Special Publication reviews and extends the literature that describes tide-influenced paralic reservoirs and their outcrop analogues.…”

Effective flow properties heterolithic, cross-bedded tidal sandstones: Part 1. Surface-based modeling

“…The method to calculate effective permeability is presented in the companion paper 460 (Massart et al, 2016) and we report only the results here for the two models shown in 461…”