Environmental performance plays a critical role in all WesternGeco operations. We are justifiably proud or our record and work tirelessly to help our clients achieve their environmental objectives.
WesternGeco has operated an integrated quality, health, safety and environmental (QHSE) management system since 1996, based on the model described by the OGP (International Association of Oil and Gas Producers). This management system has been adopted across all Schlumberger Oilfield Services, bringing significant synergy benefits among the oilfield sectors, and giving WesternGeco access to a wide range of in-company expertise.
Air emissions
Air emissions, primarily from the main engines and generators, are the most significant environmental impact of shipping. A typical seismic vessel has up to 8000 kw of engine propulsion power, consuming 20 to 30,000 liters of fuel per day. Each 1000 liters of fuel produces between 2800 and 3100 kg of green house gases (GHG), therefore, more fuel-efficient operations significantly reduce this impact.
Fuel oil
All WesternGeco vessels run on marine gas oil, which offers considerable environmental advantages. The table gives an approximate comparison of air emissions per liter from the two main types of fuel. This table demonstrates that a seismic vessel running on heavy fuel oil emits approximately 9% more GHG than a WesternGeco vessel. More significantly, the other vessel will also emit at least 800% more sulfur oxides, the major contributor to acid rain. Marine gas oil costs twice as much as the heavy fuel oil used by some seismic contractors.
Towing technology
The WesternGeco Monowing* streamer diverting device makes the greatest contribution to energy efficient operations. Although the Monowing was first introduced in 1995, continuous improvement now enables WesternGeco to tow spreads up to 1600 m wide. After comparing fuel consumption on similar vessels over a 12-month period, we can show that a Monowing-equipped vessel consumes 6000 to 8000 fewer liters of fuel per day than a vessel using conventional diverter technology. The comparison included transit time between survey areas, so if only actual towing time was compared, excluding transit and port calls, the difference would be even greater. Based on this technology alone, WesternGeco vessels are 20 to 25% more fuel-efficient and emit 20 to 25% less GHG than other seismic contractors.
Streamer technology
Streamer technology advances have reduced drag, largely through reduced diameter. The table shows the drag created by a 40-km spread for five streamers, demonstrating that Q-Technology is clearly leading the industry.
As the number of towed streamers has increased from 6 to 8, to 10, to 12, the number of traverse kilometers per square kilometer has decreased, and despite the increased drag, we see an overall decrease in fuel consumption.
Other seismic contractors must generate at least 25% more engine power to tow streamer spreads than a Monowing-equipped vessel. Seismic data quality is also affected due to increased perturbation of the water behind the vessel, resulting in acoustic tow noise on the near traces at levels approximately 50% higher than an equivalent WesternGeco vessel.
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What is a Monowing?
The Monowing is a proprietary WesternGeco highly efficient, controllable single hydrofoil wing that is towed vertically a few meters below the surface. It generates enough 'lift' to pull streamers out to a 1600-meter separation. Operators onboard can monitor its position and attitude and make adjustments as required. As the streamer is towed directly from the Monowing, it needs no additional tow wires.
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. . . and conventional diverters?
There are several variations on conventional streamer-diverting devices, but unlike the single-wing Monowing, the others use multiple hydrofoil wings connected together, one behind the other, attached to the underside of a surface float. These diverters are typically towed from a heavy wire running parallel with the streamer lead-in.
Spill control
All WesternGeco vessels have an externally certified shipboard oil pollution prevention plan in place and perform oil-spill drills to a regular schedule. Any spill incidents or near incidents are reported into the main reporting and remedial action database, QUEST.
Based an independent risk assessment of offshore vessel refueling, WesternGeco developed robust procedures that have been successfully used for many years.
Waste management
The Schlumberger environmental standard establishes minimum environmental risk management expectations for each work site. This includes assessment, pollution prevention, waste management, and record keeping. All WesternGeco marine vessels operate to this standard, introducing the standard site environmental history file, providing training, and performing environmental audits on all vessels. Additionally, all WesternGeco-owned vessels have a waste plan in place whereby all waste streams have been identified. These include: regulated waste such as batteries, used oil and filters, hazardous materials such as chemical solvents, paint, and flares, food waste, recyclables, and general trash (burnable and non-burnable). Each of these waste streams requires specific procedures to handle waste and mitigate the risks associated with disposal.
International Maritime Organization regulations allow for discharge of some wastes at sea, such as food, wood, paper, and others; however, WesternGeco works to a zero discharge policy for such wastes.
Lithium batteries have powered cable depth controllers for many years. WesternGeco has a long-term strategy to eliminate this requirement. With Q-Technology, cable depth controllers are powered through the streamer, eliminating the need for non-reusable lithium batteries. As a shorter term measure to reduce the use of batteries, in 1996 using Schlumberger in-house expertise, WesternGeco developed the SLB150 lithium battery, which increased battery changing intervals from 30 to more than 150 days, and combined with a specialized recycling process, allowed much better control of the disposal of depleted lithium batteries. Today, all vessels still using conventional cable depth controller technology send their depleted lithium cells to a recycling plant.
WesternGeco continues to improve waste management processes with increased auditing of waste disposal contractors, improved waste handing equipment on support vessels, and initiatives to eliminate non-biodegradable solvents.
Noise emissions – marine fauna
The potential impact of the noise we create in the underwater environment is being studied. Non-governmental organizations have challenged the industry regarding the impact sound source arrays may have on marine fauna. In the Caspian Sea, there is concern for seals, in east Canada, the Bottlenose whale, in the Gulf of Mexico, whales and turtles, and in Norway, there is concern for fish. WesternGeco is working proactively with industry associations and regulatory authorities to emphasize scientific analysis of the impact of noise emissions. We have participated in the sperm whale seismic study research project in the Gulf of Mexico, consulted on proposed new regulations, and are contributing to the OGP/IAGC joint white paper that will attempt to identify the latest science on both sides of the argument.
WesternGeco is familiar with the frameworks laid down by regulatory bodies such as the US Department of the Interior Minerals Management Service (MMS), the UK's Joint Nature Conservation Committee, the Australian Government Depart of Environment and Heritage, and the Canada-Nova Scotia Offshore Petroleum Board, and fully complies with prescribed mitigation measures. The following list identifies some of the prevention and mitigation measures available:
- Marine mammal observers – Depending on regulatory requirements, WesternGeco can either subcontract third party observers or ensure that WesternGeco personnel on the crew are correctly trained. An established training program is in place and approved by the MMS for the Gulf of Mexico. WesternGeco also has a documented observation reporting procedure that complies with existing regulatory requirements, and also allows the adoption of industry best practice where no local regulations exist.
- Soft start of marine sound source – A WesternGeco soft-start procedure complies with existing regulatory requirements and allows for adoption of industry best practice where no local regulations exist.
- A WesternGeco training program covering both general issues and marine mammal awareness supports the importance of environmental issues at all levels of the crew.
- WesternGeco can offer an integrated project design service. Part of this process optimizes the amplitude and bandwidth of acoustic energy, based on modeling using heritage data where available. This ensures that sound source array volumes meet geophysical objectives without dispersing excess energy
- By application of its quality management system, WesternGeco continuously improves practices and equipment reliability, thereby reducing rework and infill.
- Passive acoustic monitoring – In some regions of the world, passive acoustic monitoring (PAM) of marine fauna is required. WesternGeco has used this monitoring equipment since its first testing in 1998, and used PAM in Australia, Canada, and the North Sea in the past year.
- By capitalizing on proprietary technology, WesternGeco can ensure that a survey area can be covered with the minimum number of traverses, thereby reducing source effort.
Conclusion
While it has been widely acknowledged that WesternGeco is a market leader in health and safety management, we also claim leadership in environmental management. Rather than just meeting regulatory requirements and industry guidelines, our target is "Beyond Compliance".