Category: Hydrogeology

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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Viewing multiple images projected on topography

By Sam Bain

Leapfrog allows users to import a range of images into a project so they can be viewed on topography. These include but are not limited to topographic maps, satellite imagery, aerial photos, and geological maps.

Imported images can be viewed projected on topography by adding the topography to the scene and then selecting them from the GIS data drop-down box below the topography object in the shape list (Figure 1).

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Modifying your drillhole data: Interval Selections

By Sam Bain

The “Interval Selection” tool in Leapfrog combines most of the abilities of Grouping and Splitting (as discussed in previous blogs) with fewer restrictions. The Grouping and Splitting tools provide workflows for combining or splitting existing lithologies exclusively. The intervals selection is ideal when elements of both the grouping and splitting workflows need to be combined. For example, perhaps assay data indicates some intervals have been incorrectly logged and need to be assigned to a new lithology. If these intervals have been logged as several different lithologies then they need to be split from their old lithologies and then grouped to a single new lithology. The interval selection tool allows you to do this.

Figure 1: Right click the interval table and select the "Interval Selection" option

Figure 1: Right click the interval table and select the “Interval Selection” option

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Modifying your drillhole data: Splitting lithologies

By Sam Bain

The “Split Lithology” tool (available in Leapfrog Geo, Geothermal, and Hydro) creates a new lithology column by sub-dividing lithologies in an imported column. Often simple logging will result in repeating intervals on each drillhole and these will need to be separated for modelling purposes. As an example, perhaps three unique limestone units at different depths are encountered by exploratory drilling. These might all be logged simply as “Limestone”. In this case the splitting tool could be used to divide the “Limestone” intervals into “Upper”, “Middle”, and “Lower” units. Then each unit can be modelled separately. It is important to note that the original logged intervals are preserved, and the new splits are made in a new interval column. The modeller can correct or re-interpret the logging without altering the original field data.

This blog explains how the “Split Lithology” tool works by walking through a simple example.

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Modifying your drillhole data: Grouping

By Sam Bain

A standard workflow in Leapfrog is building a geological model from the interval columns of imported drillholes. This workflow requires the importation of a collar locations file, a survey file with drillhole geometry, and an interval table with the observed lithological contacts. In addition, other down-hole information such as from geophysical logging or drill core assays can be imported as interval tables.

Often there will be problems with the drillhole data. Perhaps the logging in the field was inaccurate and two unique units were incorrectly lumped into one. Of course, the opposite could happen if an eager geo sub-divides a single sandstone deposit into separate poorly sorted and well sorted units. In these situations, the drillhole data needs to be edited so that a new unit is defined or existing units are combined. The “Group Lithologies” and “Split Lithologies” tools in Leapfrog allow you to create a new interval column based on edits of an existing interval column. An additional tool called “Interval Selection” has been developed that uses elements of the grouping and splitting workflows to create a new interval column. In this post we will look at the “Group Lithologies” tool.

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Drillhole Data Errors: Acknowledging a reality and dealing with it

By Sam Bain

Introduction

Everyone would like accurate and correct data. A lot of money is spent on trying to ensure the accuracy of data, whether it is from core logging, field mapping, or geophysical surveys. However, the reality is that mistakes and accidents will happen and some data will be wrong. Accepting that errors are always going to get in somehow, it makes sense to create systems and software that identify these errors, and then provide the tools to fix them. Good software packages help deal with data quality by identifying common errors on import of data and providing automated correction of these problems. Ideally there should be a person in the loop to ensure the identified data is an error and to decide how they should be dealt with.

Leapfrog software automatically highlights recognised data errors and in most cases provides automated or semi-automated correction tools for you. The principle source of errors is drillhole information and the drillhole interface prominently highlights recognised issues and offers you the ability to correct errors. Leapfrog software will also recognise errors and potential errors in imported locations and prompt user input to fix them.

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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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Kickoff for the new Leapfrog blog

By Shaun Maloney

Shaun Maloney CEO ARANZ Geo Limited

Welcome to Leapfrog’s blog

I‘m fortunate to be asked to write the first Leapfrog blog and to set the scene for what we hope will be many thought-provoking blogs to come. No pressure then! Seriously though, we want this blog spot to open up a dialogue between anyone interested in geology and geological modelling in particular. So if that’s you, please get involved, we’re interested in what you have to say!

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