Managing exploration portfolios on spreadsheets

Let’s say you’re an exploration portfolio manager. Your role (or at least 1 of them) is to oversee prospects in your portfolio. Those coming into your portfolio, prospects evolving through your portfolio, approving the best ones to be drilled, and reporting a summary of all this information to the Board as and when required.

Managing the risked volumes of a single prospect is quite straightforward. An explorationist in your team has identified and mapped a prospect (Figure 1A), they have calculated some deterministic GRV volumes to work out the rough size of the prospect, and then calculated the probabilistic resources by varying unknown parameters such as porosity, hydrocarbon saturation, and chance of success of the play elements etc. (Figure 1B). The output to this process is currently a spreadsheet which is presented to you (Figure 1C).

managing risked volumes

Figure 1: The general workflow for reporting the resources in 1 prospect. A – create a prospect map. B – Calculate the risk and resource volumes using Monte-Carlo. C – present the output on a spreadsheet.

Next Step: More data

Some seismic has just been reprocessed over the area and it’s clear with the better imaging that the closure doesn’t extend as far north as hoped. The probabilistic volumes are run again with a smaller closer but with greater certainty. You now have 2 versions of the spreadsheet to manage. The original (Figure 2A) and the revised volumes (Figure 2B). As the exploration portfolio manager, this change is easy to understand. Your team have shown you the original volumes, the new volumes from the reprocessed seismic and explained what has happened.

REP managing spreadsheets

Figure 2: 2 spreadsheets now to manage. A – The original resource output. B – The revised resource output

Next Step: Peer Review

You call your team in for a peer review of the prospect and you ask to see the maps and data for this prospect. It’s a detailed and rewarding technical discussion on the prospect. It seems like the team may have missed an opportunity to target a deeper reservoir which has been known to produce in the basin. Good news for the company but bad news for the team – they now must go back and map the deeper target. They return to you with 2 additional spreadsheets for the volumetric calculations: 1 for the deeper target, and 1 for the overall prospect. You now have 4 spreadsheets to manage.

REP managing spreadsheets x 4

Figure 3: 4 spreadsheets now to manage. A – The original resource output. B – The revised resource output for Target 1. C – The new resource output for (the deeper) Target 2. D – The new resource output for the overall prospect

Next Step: JV partner meeting

A JV partner in an adjacent block has just drilled a well into the same plays as this prospect. It shows that the source rock may actually be a shallower biogenic gas source and not the deeper thermogenic oil you were hoping for. In addition, the primary porosity in both plays has been badly affected by diagenesis and the reservoir quality is not looking great. Your team create yet more spreadsheets. There are 3 new spreadsheets to cover the new information on the porosity of each play. A further 3 spreadsheets are created to model the possible scenario where the hydrocarbon type is pure biogenic gas. Your team presents you with a further 6 spreadsheets. As the exploration portfolio manager, you fear that a mistake has been made and you hope that your team has given you the correct, up-to-date versions of each target/prospect/scenario.

REP managing spreadsheets

Figure 4: The number of spreadsheets continues to grow as new information and new theories about the prospect evolves

Next Step: Decision Gate

You have another peer review meeting and the prospect has passed the decision gate – it is approved and ready to be added to the portfolio. You ask someone in the portfolio team to update your portfolio spreadsheet with the key numbers and mark the prospect in this year’s portfolio as ‘approved’.

However, this isn’t the only prospect your team have been investigating. There are 4 in this license block so the total number of spreadsheets to handle has quadrupled.

Spreadsheets and prospects

Figure 5: Approximately the same number of spreadsheets have been generated for each of the 4 prospects in this license

To make things harder for you, this isn’t the only team who report to you. Your company is exploring in 3 different areas so the total number of spreadsheets trebles again.

Figure 6: The number of spreadsheets expands as your team work on the 12 prospects in your portfolio.

The Board has asked you to present an overview of the portfolio next week.

You worry that your portfolio is disconnected from any database or geological data sources. The visibility over the entire exploration portfolio is poor and you fear that sooner or later, you will miss some incorrect resource estimation and, therefore, make a poor decision for where to invest your companies limited resources.

Surely there must be a solution to your problems?

There is, and it’s called PLDB.

Get in touch

If you would like to know more about PLDB contact our team of experts.

Petrosys Virtual User Group

Petrosys Virtual User Group 2020

The Petrosys 2020 User Group is Going Virtual

Petrosys will be hosting two half-day user group sessions on 22nd and 23rd September 2020, U.K (BST). Whether you are a seasoned Petrosys user, a novice, or just wanting to learn more about the latest developments in the industry and stay in touch with colleagues, we are extending an open door for all to attend our virtual user event.

With many events, trade shows, and conferences canceled or postponed this year many of us will have missed out on the usual opportunities to network with peers and keep up-to-date with industry news.  Join us for this user forum where you will be able to talk with the Petrosys experts and listen to colleagues as you find out more about what is new and coming up next in Petrosys PRO. Dig deeper into new features and parts of PRO that you may be unfamiliar with but which could revolutionize your workflows, with our ‘how to’ and ‘did you know’ sessions.

We will also explore the data management capabilities of the Petrosys Prospects and Leads Database, PLDB, and take a more in-depth look at new features such as the new REP loader – a game-changer for those working with spreadsheets.

We are excited to have guest speakers from partners GLOBEClaritas and Interica. Find out more about GLOBEClaritas and the latest new features and significant enhancements to the software. While the team at Interica will explain about the collaboration between Petrosys and Interica with the powerful map archiving in Interica OneView and their ongoing work with the OSDU.


Everyone who attends the user group will be entered into our prize draw to win a genuine piece of North Sea Core courtesy of

Registration closes on Monday 21st September 2020 at 12 noon UK (BST) after which meeting invites will be sent out.

If you would still like to attend the Virtual User Event please email


Agenda for the two half-day sessions

Register for the full event and then feel free to drop in and out for the talks and sessions you are interested in. 

Petrosys Virtual User Group Agenda 22nd Sept

Petrosys User Group Agenda


Dear Steve..Is there a better way to manage our portfolio?

Dear Steve, portfolio management

Dear Steve,

Q. I have been using the Probabilistic Resource Calculator (PRC) in Petrosys PRO successfully to create risked volumes of my prospects. However, I now find myself struggling to manage our exploration portfolio on spreadsheets. Is there a better way to manage the evolving portfolio?

A. Yes, there is. It’s called the Prospects and Leads Database (or PLDB for short) and calculations from the PRC can feed straight into this repository.

The risked volumes don’t necessarily need to come from the PRC either. PLDB is designed to store prospect information from a variety of spreadsheet sources. For example, Logicom E&P’s Resource Evaluation Programme (REP) spreadsheets can also be stored and managed in this repository. We can also customise the loader to work with any other spreadsheet format.

Here’s How

1. Calculate the resources as normal (for example in the PRC, in REP, or elsewhere) and generate an output spreadsheet

PLDB Spreadsheets Reserves

2. Login to PLDB (each user will have different levels of permission)

3. Select ../Admin/Data Exchange/Import…

4. Select the relevant loader (here the REP loader has been used)

REP Loader in PLDB

5. Click on ‘Choose File’ and find the spreadsheet from Step 1

6. Fill in information about the prospect using the ‘lookup’ tables

7. [An example of a lookup table]

8. Press the Load button to load the resources into the prospect

Here’s Why

Spreadsheets are isolated and static.

  • Isolated – as you need a separate spreadsheet for each prospect (possibly a separate spreadsheet for each target within a prospect)
  • Static –  as you need a new spreadsheet for each new updated calculation as your knowledge about the prospect grows.

Your portfolio is connected and dynamic.

  • Connected –  as new information about 1 prospect has significant effects on another. For example, if a new well proves a new play, the chance of success of any prospect containing this same play must increase.
  • Dynamic –  as new and better information is continually evolving. Re-calculations are common to provide management with the latest knowledge to make the best decisions possible

PLDB is connected and dynamic.

  • Connected –  as play information is shared between prospects. Targets also have linked dependencies such that if 1 is successful, the likelihood that another will succeed increases.
  • Dynamic –  as the ‘chronology’ feature tracks the changes through time, allowing the evolution of the prospect to be tracked. This also means that version management is not an issue.

Find out more about the Petrosys Prospects and Leads Database, PLDB.

Get in touch

Speak to our team of experts about PLDB today.

Adjust. Succeed. Deliver – A message from the CEO

It never ceases to amaze me how adaptable we all are in our ability to not just keep going despite challenges, but to adjust, succeed, and deliver on our promises to clients and business partners.

Within the Petrosys Group, this is clearly evidenced by the level of productivity that has been achieved by our teams, who like many are working from home and have worked tirelessly to develop and produce new software releases Petrosys PRO 2020.1 and dbMap/Web 2020.1, deliver a range of technical and informative webinars, as well as create multiple helpful videos and product articles.

The high level of appreciation for this creative output has been marked in the 5* support feedback rating we have received from our users throughout 2020. It has similarly been very pleasing to see the increase in demand from clients who have been able to take advantage of the work from home initiative offered and the continued engagement we have had with users across all fronts. Your input on future roadmap developments is crucial and many will recognise the results of this feedback in the recent software releases.

Please keep telling us your business needs and drivers for the future of the software and we will continue doing our very best to deliver.

The oil and gas sector continues to face challenging times causing a demand for technology that can enable efficiency and improve workflows. I’d like to take this opportunity to impart Petrosys’s on-going commitment to the industry. We continue to invest organically and beyond in an effort to help companies do more with resources that are scarce.

PRO 2020.1Petrosys PRO is renowned for its geoscience integration and connectivity with 3rd party sources and this brilliant work has gone from strength to strength with the help of our partners, in recent months evidenced by the addition of the Ellis Palesocan connector.  The excellence of the Surface Modeling module keeps shining through with new functionality such as the Fault Clipping Distance controls, meaning more accurate grid surfaces around fault zones, read more about working with faults in, ‘Mapping with Faults using Autotracked Interpretation‘. While our industry leading Mapping simply just gets better and better, you can now directly display PDFs on the map canvas, take advantage of FMI logs in the log signature map displays, and extract raster images directly into grids – see the latest Dear Steve.  ‘Using Colour to Communicate‘ explains in detail about the new perceptually uniform colour gradients added to PRO 2020.1.

The Petrosys Client Portal is also a fantastic resource for users and the team has been busy collating pdfs and videos into useful workflows to allow for easy searching of ‘how-to’ documentation, helping you find what you need faster.

The role of sound data management and data quality is the backbone of all that we do and not only have we made advances in the latest release of dbMap/Web 2020.1 with the expansion of the well log viewer to display multi-value log curves such as FMI data; but also to our Prospects and Leads database PLDB, where users can now import data from REP and new data loaders for production data and well test have been added.

Interica OneViewEarlier in the year, Petrosys acquired Interica, a respected data management software company with strengths in analysis of the data landscape around many data sources and applications and data archive/optimisation. It has been inspiring to see how smoothly the teams have managed the integration of Interica into the wider group with version 6.2 of Interica OneView released at the end of June. The new ideas, opportunities, and synergies that develop from the wider collective as we build on the collaboration across all sectors of the companies is exciting, the benefits of which to our clients are highlighted already in the existing capability to support Petrosys project archiving. We are now working on ideas to deepen this R&D synergy for client benefits around data landscapes, 3rd party integration, and capturing key knowledge at important project gates and milestones. We look forward to growing and expanding this shared offering and welcome your input to shape the direction.

The innovation keeps coming with the GLOBEClartias team who are doing some exciting work, for example, the AI based methodology recently released for denoising seismic records, with the new DENOISE_TF module. The latest version of GLOBEClaritas V7.1 is out now, along with completely re-vamped tutorials for the new version. It is easy to see why GLOBEClaritas is fast becoming a leader in seismic processing software through continuous and frequent software releases and new features.


We are also extremely proud of the client feedback received for our GPinfo products, maps, and the great service they deliver on a consistent basis. To me it demonstrates the day-in-day-out commitment to data management excellence and map product quality – we practice what we preach at the Petrosys group when it comes to delivering quality data frequently! I find the quotes from clients both humbling as well as motivating, they drive us to serve, to innovate, and to continue to deliver on a monthly/quarterly and yearly basis. It is clear the products the GPinfo team provide are extremely valuable to existing and prospective investors in the Australia-Pacific region.

From everyone at the Petrosys group, we encourage you to contact us if you need help, we thank you for your continued support and we look forward to the days we can meet again in person.

I hope you, your colleagues, and families keep safe and well. If you have questions or need any help – please just ask me.

Scott Tidemann

CEO Petrosys

Mapping with Faults using Autotracked Interpretation

Mapping with faults

Kevin Ward, Petrosys Europe

In the latest software release of Petrosys PRO 2020.1 new functionality has been added to improve quality and efficiency when mapping faulted horizons.

Often tricky and problematic for geoscientists, I thought it would make sense to write a short summary of how we see these improvements fitting into the wider workflows for today’s geoscientists and ask for your thoughts on what else we could be doing to make your life easier.

The challenge comes from how we interpret seismic horizons near to faults.

In the past, resolution was the main issue. What I’ve seen in the industry more recently is that imaging is not as problematic as it used to be, however, interpreting around faults is still an issue due to the prevalence of autotracking and AI/ML workflows.

Seismic section

Figure 1: Seismic section with some sketch interpretations. The Yellow line is a fault. The Blue line is indicative of human interpretation. The orange line is indicative of autotracked interpretation

In Figure 1, for example, the imaging around this fault is pretty good. A human would know to interpret the horizon up to and ‘snap’ [the blue line] onto the edge of the yellow fault. However, when using (even some of the more sophisticated) autotracking technology, without manual intervention, there is a tendency for the horizon to be continuous and ‘bend’ [the orange line] through the yellow fault zone.

The problem

When you use mapping technology to generate faulted surfaces from the autotracked horizons, it creates a twofold problem:

  • Firstly, tools which convert fault sticks to fault polygons will struggle because there is no physical separation of the horizon to define the footwall and hangingwall of the fault [see orange box in Figure 2].
  • Secondly, the artificial ‘bend’ in the horizon will lead to erroneous data points and hence artefacts near to the fault [see blue box in Figure 1].

It’s difficult to put this into words so, as I usually do, let me try to show this using a map….

Grid with seismic interpretation

Figure 2: Creating a grid using seismic interp and fault sticks as input. Left: The ‘human-picked’ interp where there is a gap at the hangingwall and footwall intersections. Right: The ‘autotracked’ interp with no gaps at the faults

The solution

One of the new features for PRO 2020.1 is the ability to remove input data points within a user-defined buffer around faults. This solves both of the original problems:

  • Firstly, it creates a physical separation in the hangingwall and footwall horizon-fault intersections, generating more realistic fault polygons.
  • Secondly, the surface generated near to and within the fault polygon is more realistic as the erroneous data points are now excluded.

Of course, in reality, geology never has a ‘one-fits-all’ solution but by varying the user-defined buffer and making use of powerful workflow functionality, it’s fairly straightforward to generate some iterations and decide on the best way forward without any manual intervention. This is shown in Figure 3 below, where the image on the right no longer suffers from the collapsed fault polygon or artefacts that the original ‘autotracked’ surface had problems with.

cleaning input around data faults

Figure 3 – Cleaning the input data around the faults. Left: The ‘autotracked’ interp. Right: The ‘autotracked’ interp but this time using a 50m fault cleaning buffer

The difference

But does this functionality actually make a difference? From a subjective point of view I would argue in Figure 3 the map on the right gives a much clearer and more accurate representation of the prospect than the map on the left (i.e. the fault cleaning has done a good job).

There is also a difference in the volumes of the prospect in each map as the closure behaves differently in each. It’s difficult to use volumetric evidence alone to say which volumetric number is the best one to use. The point, however, is that some sound technical thinking about how the horizon actually interacts with the fault in the subsurface, combined with access to some powerful technology of course, will lead to a meaningful improvement in the accuracy of the prospect volumetric calculation.

Taking it a step further

We ran this functionality over some real-world data and presented it back to the client who had provided the data. In addition to some fine-tuning of the functionality above, it was also suggested that the raw fault polygons may not be useable for further operations. For example, the narrow fault polygons may be too thin to satisfy the requirements of an upscaled dynamic simulation model. Also, the thin heave in the raw polygon might not capture the full extent of the area of deformation. We therefore also added in some control on the heave of the fault polygon being generated.

minimum heave

Figure 4 – The ‘minimum heave’ option. Left: no minimum heave specified. Right: A minimum heave has been chosen. Notice the fault has widened in areas where the original heave is less than the chosen distance but identical in areas which already had wider heave

As you can see in the maps above, the user has the ability to use the raw heave (from the horizon to fault interpretation) or alternatively specify minimum heaves to suit future operations.


In my opinion, mapping in faulted horizons is going to continue to be problematic for geoscientists, even if the types of problems evolve as we get further into automated, scanning technology. Petrosys PRO has always had some tangible strengths in mapping of faulted horizons and I believe the changes we’ve made for PRO 2020.1 will allow this to continue for modern interpretation workflows. Even better, as they are part of the ‘surface modelling’ module, they can be added to workflow so that manual interaction is kept to a minimum, which is the whole point of autotracking in the first place.

However, these are just my thoughts. What are your thoughts on mapping in faulted horizons? The idea to allow widening of fault polygons only came about late on in the development phase so there may be other problems out there that we need to be solving for our industry – I’m looking forward to discussing what they are.

Get in touch

If you would like to know more about Petrosys PRO contact our team of mapping gurus.

Dear Steve

Q. Dear Steve… Can I display raster images as a grid in Petrosys PRO?

A. Yes, now you can!

With the release of Petrosys PRO 2020.1, users are now able to display raster imagery with XYZ data as grids in Mapping and, in general, use across the software as part of any workflow.  The new functionality will allow users to quickly add and use these types of georeferenced images into their maps and workflows without having to import them into one of the traditional grid formats.

raster images

To be able to directly display raster images as grids, two conditions need to be met:

  • Images need to be georeferenced
  • A ‘digital value’ needs to be assigned to each pixel in the image. This is the value that would be used as ‘z’ when displayed as a grid.

For users to take advantage of this functionality in Petrosys PRO Mapping, all they need to do is to follow the same workflow to display any grid in PRO:

  1. In Mapping, go to Display > Grid… or click the relevant icon.
  2. Set the data source to ‘Raster file’.
  3. Point to the raster image.
  4. If needed, override the CRS. This option is available as not all raster formats store this info.
  5. Then, tread as any other grid and set the parameters accordingly. Note you will be able to generate contours ‘on the fly’ from the Contours

display grid

To query the raster metadata, click on the ‘information’ icon on the right side of the file box

A panel like the below one will be presented. Checking and understanding the raster metadata is important as users need to be aware of which ‘band’ contains the relevant info to be displayed.

raster details

To query detailed grid statistics, click on the ‘information’ icon on the right side of the statistics section. A panel like the below one will be displayed.

detailed dispcription

In addition, rasters can also be displayed as grids using any of the display options you would have for any grid: colorfill, values, sun shaded, highs and lows, and even orthocontours.

primary window

The use of raster imagery as grids is not only restricted to Mapping but can be used across the software both in Surface Modeling and the 3D Viewer.

In the below screenshots from Surface Modeling, it can be seen that in any workflow where there is the ability to select grids in various formats, the ‘raster file’ has now been added as one of the input options. The ‘Surface Modeling’ application can also now import raster files with non-square cells.

data source selection

And same goes for the 3D Viewer

display grid

File types supported include DEM, GeoTiff, ECW, Arc BinaryGrid, ERDAS Imagine and BIL files.

 Read about more new functionality in the release notes or users can find numerous workflows in pdf or short video format are available in the Client Portal.

Get in touch

If you would like to know more about Petrosys PRO contact our team of mapping gurus.

Interica OneView and Petrosys PRO Map & Project Data Landscape

Interica OneView provides a clearer picture of the Petrosys PRO Map and Project data landscape

Petrosys acquired Interica in early 2020*, as an oil and gas sector leading, subsurface data management software company, and as Petrosys CEO Scott Tidemann explained, «Collectively we have industry leading 3rd party data connectors and R&D experience with a broad range of oil and gas subsurface knowledge.»

Upstream Oil and Gas Companies generate vast volumes of complex data through the use of diverse petrotechnical application workflows. These applications range from seismic processing and interpretation through to full static and dynamic reservoir modeling, with multiple discipline led workflow applications in between. The analysis, interpretation, and modeling completed through these applications become the Intellectual Property of the Oil and Gas company. This ultimately is the foundation of their value and what differentiates one company from another.

Petrotechnical data volumes continue to grow rapidly. It is critical for companies to design & deploy comprehensive and standardised data management strategies that result in a holistic view across this core and complex data landscape. Torbjørn F. Folgerø, SVP, and Chief digital officer at Equinor recently stated “Our operations generate huge quantities of data—26 petabytes per year, 50 times the US gene database. It’s not improbable that we will reach 2500 petabytes by 2030.” (1)

Interica OneView delivers a unique, single pane of glass view across the entire petrotechnical application environment. Dynamically liberating rich data and metadata from applications, giving immediate insight into application, data, and user footprints. Interica OneView also offers out of the box connectivity to 35 petrotechnical applications from companies such as Schlumberger, Halliburton, Petrosys, IHS, CGG, Paradigm, Eliis, and many more. The metadata and spatial data collected from these applications is normalized to enable querying across all applications, additionally, any application specific metadata to also collected. This enables:

  • Live data discovery – quickly ascertain data usage by application or user, detect data duplication across projects, understand quality, and explore data lineage all from a single interface or set of consistent APIs.
  • Automated actions – archive projects at agreed milestones and/or migrate projects & data when inactive, or support data migration projects. Build and simulate policies and their effect, based on the collected metadata. For example, to archive all data for a given field or license, to migrate all active Petrel data to file storage and all inactive to object storage or to archive all data relating to users that have recently left the organization.
  • Easy Restore – When organisations choose to move or archive these datasets to low cost object/blob storage, they can use the metadata to explore the project content without needing to bring project or dataset back online first. This reduces cost and results in the restoration of datasets users know they need – with confidence.

Current OneView Integration with Petrosys PRO

Interica OneView quickly identifies all Petrosys PRO projects that have been created within an organization before collecting any available metadata, spatial data, and images that are available within the projects. This includes Petrosys PRO reports, map sheets, project summary information, and associated geospatial and CRS data.


Users can quickly see all the data sources that were used to create their Petrosys PRO project, captured from an audit trail available in the summary information. All information is stored in Interica OneView and is continually updated with any subsequent scans.

Interica OneView and Petrosys PRO

Users can query their Petrosys PRO projects individually or in the context of other applications and datasets and use the Interica OneView charting, spatial, and query tools to analyse their Petrosys PRO data landscape.

Interica OneView

Interica OneView archives your valuable Petrosys PRO maps at key milestones in your project’s lifecycle. These milestones can include: reaching an important conclusion, completion of the project, a major joint venture investment, or as part of reserves redetermination. If referenced data is held externally to the project in applications such as Schlumberger Petrel, IHS Kingdom or other 3rd party systems Petrosys PRO connects to, these references are stored with the archive.

Interica PARS software

Interica PARS

The Interica OneView capability can work in harmony with the Petrosys PRO project crawler – a utility for extracting and collating summary information about large collections of Petrosys PRO files, such as all the grid files in a Petrosys PRO project. Regularly running the project crawler and keeping the associated metadata reports, will enrichen the data knowledge and information archived for Petrosys PRO projects (helpful on future restore) when used in combination with the Interica OneView setup.  Read More about the Petrosys PRO Crawlers.

Looking ahead. The roadmap for how these trusted technologies could evolve – input welcome!

The team is working collaboratively on the vision for extension of the present capability of Interica’s Petrosys PRO connector, with a focus on:

  1. A one button press intelligent map archiving capability – to help archive associated map and workflow data. The focus being to deepen the capture of maps at milestones, key audits, for JV meetings, and similar mission critical processes.
  2. An automated map archiving capability – tying into the popular Petrosys PRO surface modeling and volumetrics workflows. In particular, this is focused at the capture and management of deterministic and stochastic resource assessments.
  3. We are also considering the value in a wizard that guides the selected capture and archiving of a series of project maps and milestone information. Both to help feed a “map catalog” understanding of key knowledge and ensure vital data is effectively managed at project milestones.

Naturally, we anticipate making the data landscape, analysis, and archive tools richer through time based on active client needs and inputs. Our team is gathering the desired project needs now to plan the next innovation steps. If you have ideas and requirements to share or are interested to outline business challenges associated with this initiative – please pass them along to the teams.

Contact your account manager and our technical support staff to find out how Interica OneView can further support your organisation’s challenges or to share your input on the roadmap.


*Petrosys and Interica are part of Vela, an operating group of Constellation Software Inc. (TSX:CSU)


Using Colour to Communicate

New colour gradients in PRO 2020.1

Susanna Willan, Petrosys

Improve your mapping standards by taking advantage of the latest scientific colour gradients. We have added a number of perceptually uniform and ordered gradients to new release Petrosys PRO 2020.1, created by Fabio Crameri – a data visualisation scientist.

When assigning a colour gradient to a subsurface map, do you think about how this gradient is interpreted? Or how accessible it is for all users? Or do you apply the prettiest colours (I use this term loosely) and click publish? Research on data visualisation and scientific colour gradients has been carried out for decades and numerous authors have lamented the misuse and overuse of the rainbow colour palette, also known as the jet colour palette.

Despite this, the application of appropriate colour gradients by many geoscientists has lagged behind. I must confess that I was also late to the party. Why is this? Perhaps there has been a misconception that using the full RGB spectrum for subsurface maps will highlight the detail required for interpreting geological structures? On top of this, the rainbow colour gradient has also stubbornly embedded itself as the gradient ‘default’ for numerous software vendors. We are creatures of habit and this visual familiarisation has led to an acceptance of the ‘norm’. All I can say to that is STOP. Explore your data and explore your options, don’t accept the default just because it’s the default. Please read on…

So why is the rainbow colour palette bad for subsurface mapping?

We use visualisation methods to understand trends, patterns and structures in the underlying data. For geoscientists, colour is one of the most powerful techniques for visualising the subsurface geology in depth/time maps. Colour (along with contours) is used to quickly identify structural highs and lows, erosional and depositional features and stratigraphic thickness changes. On top of this, geoscientists use maps to analyse attributes such as porosity and net pay. Therefore, a colour palette should:

  • reflect the data distribution in a uniform and ordered manner
  • be accessible for those who are colour blind
  • be legible in black and white print.

The rainbow gradient does none of these things. Have a look at Figure 1. Do you find yourself focussing on specific parts of the spectrum, such as the sharp contrasts at the cyan and yellow wavelengths? These are caused by a non-linear increase in brightness and result in artificial boundaries forming where none are present in reality.

rainbow gradient

Figure 1: Rainbow gradient

To illustrate this further I will compare three subsurface grids. Each grid covers the same area at a different scale. They have been displayed with the rainbow gradient and a perceptually uniform and ordered gradient. In the small-scale maps that show the regional structure of the Top Latrobe grid (Figure 2), the rainbow gradient introduces a significant amount of ‘banding’. Within these bands, our eyes are desensitised to smaller changes, especially within green and yellow wavelengths. This hides the detail that is otherwise picked up by the lapaz gradient, such as the sinuous channel that trends NW-SE before reaching the basin.

lapaz gradient

Figure 2: Top Latrobe regional grid displayed in the rainbow gradient (left) and the lapaz gradient (right).

On the medium-scale and large-scale maps, the rainbow gradient introduces two artificial boundaries to the subsurface. One has formed where the cyan and dark blue hues meet and the second where yellow and red hues meet. These unequal contrasts occur even where the contours indicate that there is little topographical change (Figure 3).

Bamako gradient

Figure 3: Intra Flounder grid displayed in the rainbow gradient (left) and the bamako gradient (right).

At prospect scale (Figure 4), this distortion makes it harder to discern the size and scale of potential structural traps. As a first pass assessment, I certainly feel more confident identifying the lowest closing contour in the right-hand map. Or rather, my eyes can interpret the subsurface geometry more accurately.

Batlow gradient

Figure 4: Intra Flounder grid displayed at prospect scale in the rainbow gradient (left) and the batlow gradient (right).

Improve your mapping standards

To avoid data misrepresentation, I would encourage you to look beyond the default colour gradients used by many software vendors. For PRO 2020, Petrosys have added a number of sequential and divergent gradients, created by Fabio Crameri. These gradients are perceptually uniform so they do not distort the underlying data and they are perceptually ordered so you can see which direction the data decreases and increases. They are suitable for people with colour vision deficiencies and they can be read in black and white prints.

So the next time you pick up a Petrosys PRO project, have a look at the new gradients added to our Gradient Selector and test these out to see how accurately they pick up erosional and structural features. Try not to settle for the default, go forth and create some beautiful scientific maps.

New Petrosys PRO gradients

Figure 5: New gradients available in Petrosys PRO.

I want to finish with this last tip. In PRO, each new gradient is set as dynamic by default, meaning that it will automatically fit the range of the gradient to the minimum and maximum value in the input data. However, you can also fix the gradient to a user-defined minimum/maximum, or clip the range to the map extent.  This is a useful function when setting a small map extent over a large regional grid. The colour gradient will reset when the map extent is moved and will display the detail required for a smaller data range (Figure 6).

dynamic colour range

Figure 6: Difference between setting a dynamic colour range (middle) and clipping the range to the map extent (right) when displaying large regional grids. Dataset Acknowledgment: J. Takaku, T. Tadono, K. Tsutsui : Generation of High Resolution Global DSM from ALOS PRISM, The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, pp.243-248, Vol. XL-4, ISPRS TC IV Symposium, Suzhou, China, 2014. Data Access granted by the Open Topography Facility (

Fabio Crameri dataset and blog post
Peter Kovesi
Matteo Niccoli
Ed Hawkins

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