The global demand for energy continues to increase, which drives the need for exploration for future resources. Getting results responsibly, safely and costeffectively is the governing factor that defines success; it is a demand, not a wish. The world is watching everything that oil companies do, whether they do it themselves or use the services of a third party.
Polarcus is a marine geophysical company with a pioneering environmental agenda that seeks to deliver highend towed-streamer data acquisition and imaging services globally. Erik Godoy is the company’s engineering and technical manager. With more than 20 years of experience in and around the marine exploration industry, he has seen some major changes.
“We are one of the key stakeholders in the chain of delivering oil to the consumer, and today we must comply with every global and local environmental regulation,” Godoy said. “We are being tasked to go further than ever before and accept new challenges, for instance in environmentally sensitive sea areas, and at the same time meet stringent cost targets.”
Seismic surveys are one of the few feasible technologies available to accurately prospect for oil and natural gas reserves offshore and have been used for decades to assess the location and size of potential oil and natural gas deposits, which can lay several miles beneath the ocean floor.
Seismic vessels tow streamers to record the geophysical information. These streamers can be up to 10 km (6 miles) long and 1.4 km (.9 miles) wide.
“Around 1995 we started to experiment with ropes instead of the heavy chain and steel cable installations we were using,” Godoy said. “The goal was to reduce the towed weight so that we could increase the number of streamers to enlarge the area we could cover and improve the quality of the data.”
Ropes made from standard nylon and polyester fibers, though light in comparison to steel cable, stretch under load, which would defeat the object of improving the quality of the data. There also was the risk of breakage, which could only be overcome by increasing rope diameter and weight, thus making them difficult to handle and increasing towed drag.
Godoy and his colleagues started to experiment with ropes made with Dyneema from DSM Dyneema, a superstrong fiber made from ultrahigh molecular weight polyethylene with exceptionally low elongation properties. Ropes built from Dyneema have low diameters, which can enable seismic companies to meet their targets.
“We made mistakes in the beginning and had some failures, but we didn’t give up,” Godoy said. “The equipment onboard was already used for steel wire rope. There were sharp edges and damaged sheaves, and we didn’t know how to splice, join or attach equipment without causing abrasion or high stress points. We also had to train the operators to work with a completely new material.”
Today Dyneema is the standard fiber in ropes for seismic towing installations. Failures have been virtually eliminated, and if they do occur, they are often caused by foreign bodies in the water or by defective equipment. Towing installations can remain in the water for up to three months and are operated 24/7 by a two-shift crew system onboard specially designed seismic vessels.
The step change from steel wire to rope could not have happened without the expertise and partnership of the rope manufacturers. Suppliers such as Hampidjan, OTS and Mørenot have developed a range of high-performance ropes, rope covers and auxiliary products for seismic applications.
Today’s towing installations can produce a towed drag of 60 tons to 100 tons. Another significant factor is that the equipment in the water has a value of up to $40 million, and on it hangs the successful delivery of the project. Loss of equipment or damage that causes operational downtime or, worse, a trip back to shore comes at a punishing cost.
“I cannot remember the last time we had a failure with ropes made with Dyneema that was related to the material,” Godoy said. “We still have to contend with objects that get caught up in the towing installation, but we have been able to extend the standard rope replacement time from six months to 12 months or even longer. We still have a significant safety margin. We are not in this business to take unnecessary risks—the consequences are too great.”
“A rope is not just a rope,” added Jorn Boesten, segment manager offshore at DSM Dyneema. “In this case it is the reliable solution for seismic exploration. We have been very fortunate to have the partnership of three of the most innovative and dedicated rope manufacturers who were able to design products that use our fibers effectively. They have delivered ropes that are virtually fail-safe, and they continue to refine and adapt their product, incorporating some of our fiber innovations to meet the needs of the seismic companies.”
DSM Dyneema’s recently launched new products are tailored to meet the rope makers’ needs. Dyneema SK99 will allow them to make lower diameter, lighter weight ropes that are still easy to handle. Dyneema XBO Technology puts rope on a par with specialty steel wire-bending performance. This will allow ropes to run through sheaves that are smaller and reduces the risks of undue wear and tear through abusive operation.
Decreasing the CO2 footprint
Polarcus owns and operates seven ships that are among the most environmentally advanced in the world, all with Level 1 Triple-E accreditation from DNV GL. They are powered using marine gas oil (MGO) with a low sulfur content, and the engines are fitted with selective catalytic reduction systems.
Reducing drag is a major opportunity to improve fuel economy and lower emissions even further. Polarcus has a target of reducing drag by 15% by year-end 2015. At a speed of 4.5 knots to 5 knots, each ship will burn on average 40 cu. m to 50 cu. m (1,412.6 cf to 1,765.7 cf) of MGO per day. Every ton of towed drag that can be eliminated can help decrease the CO2 footprint. Reducing the diameter of the ropes will reduce the surface area being towed through the water, lower the drag and improve fuel economy.
“To do this we need to get to a fully engineered solution to take in all aspects of the installation,” Godoy said. “For that we will need to collaborate with the rope manufacturers and DSM Dyneema and bring in the material expertise and engineering capabilities of all parties. So far we have met every challenge that the oil industry and governments around the world have put before us. As leaders in our segment we want to continue to make improvements and reduce the overall impact that the work we do has on our world.”
There also is a cost benefit from using lightweight ropes due to the fuel saved, which during the last 20 years has increased dramatically. Added to that is the reliability and lower maintenance that can increase returns further, which can outweight any short-term savings from lower cost materials.
As the oil industry puts pressure on its suppliers to reduce costs while acknowledging the importance of reducing the impact on the environment, investments in technology, materials science and manufacturing processes by all partners in the industry help to provide the answers to responsible discovery of the energy resources that will be needed to meet global demand in the future.