6th Jul, 2023

The fundamental lessons learned from recent onshore nodal seismic survey projects

Truck behind node in sand 2

Nodal technology has transformed the way exploration teams gather seismic data, with STRYDE’s innovative nodes unlocking the ability to efficiently explore a variety of terrains and environments with fewer risks, lower environmental impact and in a more cost effective way than using alternative cabled or nodal systems.

In our recent webinar, STRYDE’s technical experts, Tom O’Toole, Kevin O’Connell and Chris Einchcomb joined forces with Jürgen Hoffmann, Geoscience Manager for DNO and Tom Rayment, Chief Geophysicist for DUG in a panel discussion on their vast knowledge and combined expertise in the field of onshore seismic acquisition.

This article shares a sneak peek into the most critical lessons they have collectively learned from recent onshore nodal seismic surveys, which can be uncovered in full by watching the webinar on-demand, as well as how these learnings can inform the way land seismic is acquired going forward…

Moving from cables to nodes

The efficiencies that nodal technology offers far outweigh the real-time data transmission of traditional cable acquisition

A question which often comes up, especially from those who are new to nodal acquisition, is how nodal data compares to conventional geophone data? The answer is that sensor to sensor, the two datasets are identical, the key difference is that compact single sensor nodal systems allow you to significantly increase the receiver sampling thanks to the reduced cost and increased efficiency of the seismic operation, especially on difficult access terrains.

In the webinar, Jürgen Hoffmann, Geoscience Manager for DNO, shared his experience with using nodal technology for a project they recently concluded in Northern Iraq, where his team acquired 3D seismic data across 250 square kilometres, where they used nodes, as opposed to cabled geophones for the first time.

Historically when using cabled geophones, DNO experienced quite a few challenges, ranging from high technical downtime caused by troubleshooting the active spread to high cost and logistical challenges.

The parameters of the project (tight timeframe, restrictive weather windows, challenging terrain, etc) meant that a different approach was required, one which was more efficient and flexible than the conventional cable surveys they had previously delivered. So, why did Juergen and his team choose lightweight nodes?

  • The node recording system was readily available allowing rapid mobilisation and compliance with the project timeline
  • It was an affordable option
  • Enable time savings in deployment, which was 3 x faster than any previous survey
  • Ability to increase in receiver density for better image uplift, at no extra cost
  • The continuous recording meant they didn't have to wait until everything was up running before they could start shooting seismic data - a significant time saving
  • Less equipment weight and volume meant that there was less effort and costs required for vehicles and crew (50% less on this survey even though the receiver density was double that of previous surveys)
  • The operations were very efficient and safe - the team didn't have any HSE incidents during the whole operations
  • Nodal technology ensured minimal environmental footprint as the team could lay out the nodes mainly on foot
  • The flexible receiver geometry also meant that they didn't experience cable limitations due to the length, and they didn't have to make complicated deviations around obstacles such as roads or rivers

Overall, the team achieved source productivity of about three times higher than previous 3D seismic surveys using cables. They also gained up to 1500 EPS towards the end of the survey - a record compared to their previous projects - and acquired the data in just 28 days, while they formally would have estimated about three months for such a survey.

It is clear that although data and image quality between nodal and cable acquisition methods are identical, the operational efficiencies that nodal technology unlocks is revolutionary for seismic acquisition teams, making the process faster, easier and more cost effective.

Processing high-density land seismic data: challenges and opportunities

Nodal technology makes data processing significantly faster with the ability to increase sampling

There’s a growing need towards higher density for land surveys to de-risk decisions, which has been exponentially driven by the use of blended acquisition and an increase in receiver count. As a result of this change, another common question or concern that people have when they're considering moving to high density acquisition is whether or not they can handle the vast amount of data that is recorded by the system.

Tom Rayment, Chief Geophysicist of DUG, highlighted in our recent webinar that from a data processing perspective, an increase in density poses a number of challenges that should be considered before increasing the receiver density - from loading and storing tens, or hundreds, of Terabytes of data, to being able to efficiently move it through a conventional processing sequence which can be overcome with software and hardware.

Comparing a 2009 and a 2019 survey in the webinar, it was clear that the more recent survey had many more shots and receivers per square mile compared to the 2009 data, as well as much longer offsets. This resulted in a trace density that was two orders of magnitude larger than the legacy data set from 2009, and a clear increase in image resolution - illustrating that the benefits of high-trace density far outweigh the hurdles a company may face during processing if the right software and hardware isn't available.

A key lesson that can be learned from this example is that data is going to be much easier and faster to process if a larger sample size is acquired in the field, and therefore will deliver higher resolution, interpretation ready seismic data faster than ever achieved before. One of the main reasons for this relates to noise attenuation: removing noise can pose significant challenges on poorly sampled data and requires various processing sequences to be applied in a number of domains, such as applying interpolation techniques to fill gaps in data.

Single sensor data often appear noisier than array data, but the increase in sampling makes it a lot easier to handle all the noise that can be found in land data at the processing stage. A simple process applied in one domain on densely sampled data can remove a lot more noise than if it was applied on a sparse dataset.

To learn more about the power of nodal technology and to hear from the experts on lessons learned from recent onshore nodal seismic survey projects, you can take a look at their responses to attendees' questions and watch our recent webinar on-demand…

Read the answers to the questions posed by the audience during the webinar