Category: Hydrogeology

Making the most of Leapfrog for flow modelling: Part 2

By Jason McIntosh

Continued from part 1 – Making the most of Leapfrog for Flow Modelling.

Generate and evaluate a finite element grid

Finally to generate a FEFLOW model right click ‘Flow Models’ in the project tree and select ‘New 2D FEFLOW Model’. Set the element size and boundary from either a GIS line, polyline or a GM. Next expand the grid, right click ‘grid’ and select ‘New feature’. Within the dialogue add any ‘Point’, ‘Line’ or ‘Polygon’ features you wish to refine the grid with. Select ‘Simplify Feature’ to reduce or increase the number of points used for the boundary prisms. Next double click the grid, in the ‘Features’ tab and activate any features you wish to build detail around and the number of refinement steps. Within the ‘Boundary’ tab select either a rectangular boundary or a custom boundary by selecting ‘From another object’.

2D FEFLOW grid with refined cells about the collar locations.

2D FEFLOW grid with refined cells about the collar locations.

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Making the most of Leapfrog for flow modelling: Part 1

By Jason McIntosh

Simulating fluid flow, mass and heat transfer requires the synthesis of geological models with a multitude of parameters, the process is complex. So how can Leapfrogs modelling functionality be used to streamline it? 

Interoperability with FEFLOW and MODFLOW allows Leapfrog Hydro, Geothermal and Hydrology module users to interpolate initial simulation parameters and apply them to geologically constrained finite element and finite difference grids. For the purpose of this blog I will demonstrate the capabilities by modelling an aquifer system in Leapfrog Geo, simulating it in FEFLOW and viewing the time series in Leapfrog.

Aquifer systems are comprised of permeable porous water bearing aquifers and impermeable aquitards. Both have variable permeability and porosity within the sedimentary units they are comprised of, the units themselves pinch-out and diverge within stratified layers of sediment. Stratified drift aquifers are among the most challenging of such systems, as a result of the complex depositional environments they derive from.

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Optimum performance with Leapfrog projects

By Tim Schurr

Have you noticed the “.aproj_data” folder that always appears along-side your Leapfrog project file?

 aproj_data-folder in Leapfrog Geo

If you’ve ever had to move or copy a project to another location, you’ve probably come across it, opened folder using explorer and discovered a whole raft of sub-folders and files and thought “What’s all of this?  Is this really my Leapfrog project?”

.aproj_data folder beside Leapfrog project

In this article, I will explain the reason why Leapfrog saves projects in seemingly such a bizarre way, then I’ll give you a couple of tricks on how to get the best performance and reliability out of your Leapfrog projects.

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Tritium plume evaluation using a new geo-modelling approach

By Gordon P.L.Scott
Newcastle University, School of Civil Engineering and Geosciences

We’re pleased to be able to publish out first guest blog this week! Gordon P.L.Scott, from Newcastle University, School of Civil Engineering and Geosciences, has kindly let us use his current research paper for our Leapfrog blog. Have a read of this fantastic article and learn how Leapfrog software helped Gordon with his research.

 

Summary: Evaluating tritium plume

The evaluation of a developing tritium plume using a new approach through the 3D characterisation of the hydrogeology in a complex glacial environment is presented through the use of new geological modelling software and spatially varying Kh and Kv within a lithofacies method.

 

Why monitor?

The main tritium waste repository in the UK is at the Drigg Low Level Waste repository in West Cumbria (Figure 1), where the waste is stored in a series of vaults excavated into the shallow drift sediments. Over the years, it has been proven (Henderson and Smith 2011) that tritium has been leaking from the depository, and found its way into the groundwater system. The presence of ‘tritiated’ water in the groundwater system is undesirable as it is a radioactive compound that is easily absorbed into the body and poses a risk to our DNA.

The tritium concentration in groundwater can be used to check the degree of confinement of an aquifer and the rate of flow of groundwater and provide data with which to validate the hydraulic parameters of the numeric model used to monitor the tritium plume.

Drigg LLWR location map, West Cumbria.

Drigg LLWR location map, West Cumbria.

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Predictions at locations where there are no measurements

By Richard Lane

A key feature problem in geological modelling is how to take scattered measurements and use these to make predictions at locations where there are no measurements. The data may be measurements on the surface, or samples taken from drilling, or channel samples taken while excavating. Figure 1 shows the basic problem. Solving this problem is fundamental to how Leapfrog software works, and it underpins the geological and mineralization models that are produced.

Figure 1: A simple scattered data problem. Estimate the value at the red cross from the blue samples.

Figure 1: A simple scattered data problem. Estimate the value at the red cross from the blue samples.

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Interpolation and anisotropy

By Kirk Spragg

Introduction

In addition to interpolation, Leapfrog provides two tools that give the user control over the continuity of grade in their interpolants. These are the “Global Trend” and the more advanced “Structural Trend”.

The Global Trend can be effectively used to alter the results of an interpolant.  The Global Trend  is suitable to use in situations where the underlying geology implies that grade is continuous in a planar direction over large distances. If this is not the case, and the underlying geology implies that direction of grade continuity varies over space, then Leapfrog’s Structural Trend is a more appropriate tool to use when modelling your deposit or ore body.

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Is expensive video hardware for Leapfrog worth the cost?

By Kirk Spragg

The retail cost of video hardware is not a reliable guide to how well Leapfrog’s 3D visualisation functionality performs on that hardware. The more expensive workstation grade hardware solutions such as NVIDIA’s Quadro range of desktop cards are designed to accelerate operations that Leapfrog does not use. As a result, the 3D performance in Leapfrog is often no better than less expensive gaming and home grade video hardware.

In this post Applications Specialist Kirk Spragg compares five home and gaming grade video cards with a workstation grade Quadro 4000 by benchmarking the cards to determine their relative performance.

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Leapfrog interpolation basics

By Kirk Spragg

Introduction

The Leapfrog software suite uses a mathematical method called interpolation to produce dynamic implicit models.  An interpolation tool, FastRBF™ has been specifically developed by ARANZ Geo. FastRBF™ has revolutionised the way geologists produce geological models, as it dramatically speeds up the process and allows models to be updated dynamically. Although the mathematical details of how FastRBF™ works are somewhat complicated, the basic idea is relatively simple. This blog explains the process using simple examples.

Interpolation is a method that produces an estimate or “interpolated value” of a quantity which is not known at a point X say but is known at other points such as from drillhole data.  With the user’s expert guidance, Leapfrog uses FastRBF™ to “interpolate” or fill in the gaps where there is no data.  This is how Leapfrog creates deposits, intrusions and grade shells from the user’s data. Since FastRBF™ is fast, results can be quickly updated when new data is added, ensuring the implicit model is dynamic.

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