Vertical permeability estimation in heterolithic tidal deltaic sandstones

Abstract

A method for estimation of vertical permeability in heterolithic tidal deltaic sandstones is proposed. Three-dimensional, stochastic, process-based models of sedimentary bedding are used to give estimates for the effective permeability of heterolithic tidal sandstone units where heterogeneities in the sandstone and mudstone components are evaluated explicitly.Subsurface core (probe permeameter) data from two contrasting reservoir intervals in the Tilje Formation, offshore mid-Norway, have been used to derive representative petrophysical properties for the models. These data illustrate the nature of petrophysical variability in heterolithic sandstones and provide estimates of the mean and standard deviation of sandstone permeability at the lamina scale. The coefficient of variation, C v , for permeability within sandstone beds is found to be around 0.5 while the C v for heterolithic units is in the range of 1.0 to 4.0 (i.e. very heterogeneous). Measurement of mudstone permeability is a challenge; however, a limited set of mudstone (pulse-decay) measurements gives values in the range of 10 6 mD to 10 2 mD.Effective vertical permeability is mainly a function of mudstone fraction with different characteristics above and below the percolation threshold. Vertical permeability functions have been integrated with conventional well logs and compared with available subsurface estimates for vertical permeability.

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

“…The sandstone and mudstone lithologies are each 154 modelled with uniform, isotropic permeability and the value is zero in mudstone, consistent 155 with minipermeameter measurements that show mudstone permeability is often below 156 instrument resolution (< 1 nd) and at least five orders of magnitude lower than sandstone 157 permeability in a given sample (e.g. Ringrose et al, 2005). This approach yields models in 158 which toesets contain laterally extensive sandstone laminae separated by mudstone drapes, 159 analogous to wavy-bedded toesets.…”

Study of the Scale Effect on Permeability in the Interlayer Shear Weakness Zone Using Sequential Indicator Simulation and Sequential Gaussian Simulation

“…Ringrose et al [42] proposed flow upscaling regimes to determine the Vs in a twocomponent heterogeneous porous medium. Nordahl et al [41] extended their findings, which are different from some observations obtained by this study.…”

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

“…Cross-90 stratification is defined by the preserved remnants of the bedform-bounding surfaces, while 91 lithologies are distributed according to the local current velocities during deposition. This 92 process-based methodology has been used to generate highly realistic models of near-93 wellbore regions (with dimensions of the order 0.3 x 0.3 x 2 m) (Nordahl et al, 2005; 94 Ringrose et al, 2005). However, process-based methodologies suffer from two problems.…”