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Hybrid Spreads for Seismic Excellence

Robin Ellis - Sercel
Vice President of Sales and Marketing

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Sat, 05/12/2018 - 11:48

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Q: How has Sercel coped with the industry downturn?

A: When money is tight, operators spend on production rather than exploring for new fields. The fact that we are starting to see green shoots is encouraging. Our marine product range based on the Seal acquisition system and Sentinel solid streamer has a very large installed base and so we have enjoyed steady business through sales of spare parts and replacement for attrition. On the land side, we have sold more than 20 508X-Tech systems worldwide, a pretty good performance through such an extreme downturn. That said, we still do not have one in Mexico but I am hopeful that will change over the course of 2018.

With traditional land acquisition systems, data is transmitted via cable back to a central location, usually a recording truck. The other typical option for land-based acquisition is wireless nodal systems, which have become particularly fashionable in North America. In the past, we have produced both types of products with our Unite and 428 XL systems. As the name suggests, the 508 X-Tech is a new generation hybrid of both these system types, cable and nodal. X-Tech has been a success story for us and I think it will be an excellent tool in the future for Mexico.

Q: What are the main advantages of such hybrid systems? A: What has been attractive about nodal systems to the contractors in the field is that they can often achieve higher levels of production compared to traditional cable systems. In a big 3D survey there are tens of thousands of meters of cable out there, connecting tens of thousands of sensor points. If a cable is cut in the live acquisition portion of the spread, which often covers a very large area, production has to be stopped until the cable is physically replaced because all the data is being transferred back in real time. This is, of course, time consuming. The attraction of nodal wireless systems is that there are no cables. The data is stored locally in the field unit’s memory and it is possible to simply continue shooting or vibrating and gather all the data when the field units are picked up a couple of days later. The flexibility of nodal systems is also advantageous when a spread is intersected by roads and rivers, for example. With nodal there is no requirement to lay cable across the obstacle. 

The disadvantage of nodal is that every box needs a battery, usually a lithium battery, which is fairly expensive and has a limited lifetime. Between a third and halfway through the life of a system, operators will need to reinvest in new batteries. Taking into account that some systems have over 100,000 nodes, this is hugely expensive. Apart from batteries, another major disadvantage of nodal is that many of these systems, though not ours, are completely blind. This means data is acquired over a number of days or weeks before the field geophysicists can actually see the data. During that time, the sensors may be exposed to rain, wind or vehicle noise, which can greatly compromise the data quality. 

The 508 X-Tech system is both nodal and cable-based, allowing data to be retrieved in real time along with realtime quality control and monitoring. The 508 X-Tech also has the flexibility of nodal in that cable damage does not require production to sto nor are cables required to cross roads and rivers. 

Q: What new technologies has Sercel introduced offshore?

A: There has been a lot of discussion among different environmental bodies about the potential effect of seismic surveying and air guns on marine wildlife. With that in mind, Sercel has produced its Quiet Sea Passive Acoustic Monitoring system (PAM), which allows the operators of seismic systems to adapt their activities when there are marine mammals in the vicinity. The beauty of PAM is that it is seamlessly incorporated into the seismic acquisition system, taking advantage of the acoustic listening array that is towed behind the vessel anyway. While the operator is acquiring seismic data, the system is also listening for the calls and chirps of marine mammals. 

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