Integrated interpretation, an interactive approach to forward modelling and inversion

Exploration is becoming harder, with greater focus at depth or under cover. Decisions must be made to eliminate ambiguity and maximize the benefits from various types of collected data. In terms of integrating geological and geophysical data, the essential goal is to interpret the available geophysical data based on a 3D geological model populated with physical properties. The key is to develop an understanding of the relationships between geology, geophysical responses, and rock properties. That information can then be used to create 3D geological domains with very little ancillary information, and often no drillhole data whatsoever.

Geologically-based forward modelling and inversion of geophysical data plays a vital role in quantifying these relationships, but it is important to emphasize that inversion is only one part of the interpretation process. Integrated interpretation requires an interactive approach to forward modelling and inversion. Therefore, the process demands a shift in mindset when it comes to geophysical inversion. Rather than inverting a geophysical data set once, forward modelling and inversion are performed according to the required geological hypotheses that need to be tested. Integrating geological and geophysical data, particularly in cases with limited subsurface control, also requires a practical, adaptive, and objective-driven approach to interpretation.

The following case study was developed by James Reid, Director Asia-Pacific, Consulting and Principal Geophysicist at Mira Geoscience, who worked closely with Tim Chalke and Daniel Eden on the project featured below. This case study was then presented by Glenn Pears, Principal Geophysicist at Mira Geoscience during the DMEC Exploration17 conference.

Case study:

Cave Rocks nickel and gold project area, Australia

This is a great example of producing an integrated 3D geological model based on existing geological mapping, very sparse exploration drilling, and airborne geophysical data. When tested against geophysics, the gravity, magnetics, and AEM data conflicted with the originally modelled geology. The objective was to first combine the modelled geological contact and structural surfaces, and overburden cover, in a 3D geological block model, attribute it with homogeneous properties, optimize it through inversion, and assess the computed gravity and magnetic responses.

The first impression was that the correlation between the measured and calculated responses was reasonable, but areas existed where the geophysical data conflicted with the modelled geology. The originally supplied geological information depicted the main, central fold as a south-plunging anticline, but from modelling the geophysical data, it became clear that the overall plunge direction was a north-plunging syncline. Considering that a key aim was attempting to identify the basal contact of the ultramafics, this overall change in geological understanding had a major impact on the targeting strategy and any subsequent drillhole planning. Surfaces were remodelled, the geological model was attributed with optimised homogeneous properties, and the computed response was assessed. The comparison between observed and calculated improved, particularly where the syncline plunges towards the north, as showcased in the figures below.

Figure 1: First geological model with anticline fold

Figure 2: Updated synclinal geological model.

Meet the author:

James Reid – Director Asia-Pac, Consulting and Principal Geophysicist at Mira Geoscience
James has an extensive expertise in the planning and quantitative interpretation of electromagnetic and electrical methods, particularly the application of airborne electromagnetics to mineral exploration. He has broad experience in airborne, surface, and downhole geophysics, including survey design, data acquisition, processing, and interpretation using GOCAD Mining Suite, Geoscience ANALYST, UBC-GIF, and VP Suite inversion codes.

Latest news

March, 16 2020

View neighbourhoods in 3D

You can display your neighbourhoods in Geoscience INTEGRATOR 3D viewer, making it easier to understand spatial distribution of the data.
Read more
Geoscience ANALYST
May, 05 2021

3D seismic data and survey designer tools

Coming soon to Geoscience ANALYST, tools for hard rock seismic...
Read more
Case studies
April, 30 2019

ERO Copper Curaçá Valley, Brazil

Maximizing value: 3D data integration and interpretation. One of the main challenges in exploration is increasing our subsurface knowledge...
Read more
July, 15 2019

Extracting property names from a CSV

In Geoscience INTEGRATOR, extract the property names directly from a CSV file to speed up the process and reduce errors...
Read more
May, 11 2022

Effective date field

Geoscience INTEGRATOR v3.7 offers the Effective date upload field for files and maps...
Read more
August, 01 2021

Search for Objects – find anything, anywhere, anytime

In GOCAD Mining Suite find any objects you're looking for in no time...
Read more
Mineral systems interpretation and targeting
July, 13 2022

Generating exploration models from a detailed structural interpretation and Artificial Intelligence

This approach uses the comment field of the logging table to extract general topics that can then be used as learning features in a supervised machine learning classification approach.
Read more
Geoscience ANALYST
July, 07 2022

Inverting time domain data in Geoscience ANALYST version 4.0 – Virtual Lecture

Kristofer inverts TEM data in 1D through Geoscience ANALYST Pro Geophysics to recover conductivity in Geoscience ANALYST 4.0...
Read more
July, 13 2022

Monitoring folders

Geoscience INTEGRATOR's monitoring folders can be used to automatically import files to a project to save time and streamline regular updates.
Read more
February, 09 2022

Roles and permissions

In Geoscience INTEGRATOR, system administrators give users different levels of permission by role-based access...
Read more
May, 28 2020

Reshape using spiderwebs

GOCAD Mining Suite v19 allows you to reshape your surfaces and 2D Grids with a spiderweb editing tool...
Read more
Geoscience ANALYST
October, 28 2020

What’s new in Geoscience ANALYST v3.2

Past event, view here or on our YouTube channel...
Read more

Please contact our team for additional information about our products and services