Lattice Boltzmann methods applied to large‐scale three‐dimensional virtual cores constructed from digital optical borehole images of the karst carbonate Biscayne aquifer in southeastern Florida

Abstract

Digital optical borehole images at approximately 2 mm vertical resolution and borehole caliper data were used to create three-dimensional renderings of the distribution of (1) matrix porosity and (2) vuggy megaporosity for the karst carbonate Biscayne aquifer in southeastern Florida. The renderings based on the borehole data were used as input into Lattice Boltzmann methods to obtain intrinsic permeability estimates for this extremely transmissive aquifer, where traditional aquifer test methods may fail due to very small drawdowns and non-Darcian flow that can reduce apparent hydraulic conductivity. Variogram analysis of the borehole data suggests a nearly isotropic rock structure at lag lengths up to the nominal borehole diameter. A strong correlation between the diameter of the borehole and the presence of vuggy megaporosity in the data set led to a bias in the variogram where the computed horizontal spatial autocorrelation is strong at lag distances greater than the nominal borehole size. Lattice Boltzmann simulation of flow across a 0.4 3 0.4 3 17 m (2.72 m 3 volume) parallel-walled column of rendered matrix and vuggy megaporosity indicates a high hydraulic conductivity of 53 m s 21 . This value is similar to previous Lattice Boltzmann calculations of hydraulic conductivity in smaller limestone samples of the Biscayne aquifer. The development of simulation methods that reproduce dual-porosity systems with higher resolution and fidelity and that consider flow through horizontally longer renderings could provide improved estimates of the hydraulic conductivity and help to address questions about the importance of scale.

Lithofacies and sequence stratigraphic description of the upper part of the Avon Park Formation and the Arcadia Formation in U.S. Geological Survey G–2984 test corehole, Broward County, Florida

“…Classifications of porosity were assessed by using schemes developed by Choquette and Pray (1970) and Lucia (1995Lucia ( , 1999. A total of 276 airpermeability measurements (Cunningham and others, 2006) and calculated lattice Boltzman permeability values of both Pleistocene and Cretaceous carbonate rocks others, 2009, 2012;Sukop, 2011, 2012;Sukop and others, 2013;Sukop and Cunningham, 2014) were used as reference material for the purpose of visual comparison to the Avon Park and Arcadia Formation core samples from the G-2984 test corehole in order to visually estimate the permeability of these samples. The Pleistocene and Cretaceous carbonate rock samples have similar lithofacies and pore types as the core samples described herein from the G-2984 test corehole.…”

“…Estimates of permeability: Based on comparison of Avon Park Formation lithofacies and pore types to 276 Pliocene and Pleistocene eogenetic carbonate rock specimens with similar lithofacies and pore types and their air-permeability measurements (Cunningham and others, 2006) and lattice Boltzmann permeability calculations of both Pleistocene and Cretaceous carbonate rocks others, 2009, 2012;Sukop, 2011, 2012;Sukop and others, 2013;Sukop and Cunningham, 2014) Colors: Colors based on comparison to Munsell rock color chart (Geological Society of America, 1991) Ichnofabric: Index based on Droser andBottjer (1986, 1989) Top of Avon Park Formation: 1,067.60 ft bls (obi depth) and 1,066.0 ft bls (driller's depth) obi depth: 1,067.60-1,068.30 ft bls Driller's depth: 1,066.0-1,066.7 ft bls…”

Geostatistical Borehole Image‐Based Mapping of Karst‐Carbonate Aquifer Pores

“…The U.S. Geological Survey's Carbonate Aquifer Characterization Laboratory and its academic partners at Florida International University have designed methods to simulate carbonate aquifer pore systems and calculate intrinsic permeability by LBM at core scale (Cunningham et al , ; Cunningham and Sukop ; Sukop et al ), and borehole scale (Sukop et al ; Cunningham and Sukop ; Sukop and Cunningham ). Here, we report on experiments with geostatistical methods for mapping megaporosity and matrix porosity within the dual‐porosity Biscayne aquifer at the interwell scale to provide explicit models of aquifer matrix porosity and megaporosity that can be used for LBM calculation of intrinsic permeability and for simulation of groundwater flow in carbonate aquifers.…”

“…Third, the presence of boundaries, such as canals, may complicate the analysis. Finally, Darcy's Law may not provide an accurate basis for permeability determination due to departures from laminar flow in the Biscayne aquifer when hydraulic gradients are larger than about 10 −5 (Sukop et al 2008;Cunningham and Sukop 2011;Sukop and Cunningham 2014). Here, we report on experiments with geostatistical methods for mapping megaporosity and matrix porosity within the dual-porosity Biscayne aquifer at the interwell scale to provide explicit models of aquifer matrix porosity and megaporosity that can be used for LBM calculation of intrinsic permeability and for simulation of groundwater flow in carbonate aquifers.…”

Simple Models for Underdamped Slug Tests in High Permeability Aquifers

“…The vugs are commonly 2 centimeters in diameter and the porosity is frequently 50% or more. Recognizing that there is no single value for the hydraulic conductivity of the Biscayne Aquifer, the widespread existence of the extreme permeability, large diameter touching-vug facies has repeatedly been observed and its relevance to the overall hydraulic conductivity of the aquifer has been demonstrated (Sukop and Cunningham, 2014). …”