So, what will save the industry this time around, you ask?
Look back for a minute at the downturn of the 1980s. Research and development continued in 3-D seismic technology, which was already in use, albeit still costly and needing refinement, during the earlier boom times. As the technology advanced and became more affordable, it revolutionized the way oil and gas is found, leading the industry out of the dark times.
Just as the present is the key to the past in geology, conversely, the past is going to be the key to the future in technology, according to Marc Lawrence, senior vice president at Fairfield Industries.
"New seismic technology is going to impact exploration and production the way 3-D did, and it's already in the works, and the next technology appears to us to be shear wave.
"In fact, we're now at the same juncture with shear wave that 3-D was in the 80s, with some research papers and case histories just starting to come out."
Conventional seismic technology measures reflected pressure waves, providing data to help delineate the reservoir. Introduction of a shear wave component provides information about what is going on inside the reservoir. Because of the unique propagation features of the two wave types, they respond differently to the geology -- and shear waves, unlike the pressure component, are largely unaffected by reservoir fluids.
Taken together, the two can be used to distinguish between lithology and pore fluid effects as a direct hydrocarbon indicator, among other applications.
Multicomponent seismic surveys, which record both shear and pressure wave data, are implemented on land as well as the marine environment.
In water, stationary sea bottom cable systems with sensor receptors comprised of a hydrophone and a three-component geophone are commonly used to capture the data. Node systems with sensor packages linked by an electrical cable also may be deployed.
Because the shear waves do not propagate through water, air guns can be used, and the shear waves are created by conversion of pressure waves at rock property boundaries.
Although shear waves are regularly set up by conversion of pressure waves from any seismic source used in the water, they were ignored in the past because of the lack of proper recording equipment to deal with them, according to Lawrence.
Lures to the Gulf
Marine multicomponent seismic technology, or 4-C, originated in the North Sea, where it continues to thrive.
"Maybe 80 to 90 percent of the commercial marine 4-C has been done there, and the North Sea is driving the technology now," said Walter Sognnes, senior geophysical advisor at PGS Reservoir.
The commonplace occurrence there of shallow gas and fluids in fields wreak havoc with conventional seismic surveys. The gas causes signal attenuation and travel path distortion of the pressure waves, making it impossible to image deeper hycrocarbon reservoirs.
The addition of the shear wave component provides a clearer image beneath gassy zones.
"Imaging beneath gas is probably the lowest risk application that the industry overall has seen," said Jack Caldwell, reservoir solutions manager at Geco-Prakla. "It's been done successfully just about everywhere it's been tried."
Contractors are beginning to make a case for 4-C seismic in the Gulf of Mexico, where a few programs are under way. The goal of a couple of the Geco-Prakla projects is to see if a difference can be detected between "fizz water" -- or that water with little gas -- and economic gas. These data are still being processed and analyzed, according to Caldwell.
The seismic data nemesis, salt, is another lure to try this technology in the Gulf.
The base of the salt is a strong mode converter, which results in both a shear wave picture and a pressure wave picture, using multicomponent technology. It is anticipated that combining the two images will give a better image of the base of salt.
Getting Down to Business
To date, the deepest marine multicomponent survey has been about 2,000 meters, but that's clearly only a harbinger of what's to come.
"The deep water is a primary driver for this technology development," said Gene Sparkman, director of the Energy Research Clearing House (ERCH). "The interest is to project the knowledge gained to use in the deep water arena where you can't afford mistakes, so you want a better knowledge of the reservoirs and drilling hazards."
Indeed, identification of shallow water flow hazards looms high on the wish list of the deep water players.
"These shallow water flows, which occur within the top 2,000 feet of the sea floor, become unstable and start flowing into the well when drilled through," explained Sparkman, "and they're encountered in about 79 percent of the deep-water wells.
"Drilling hazards both from these and from pore pressure changes are of interest to the drilling engineers," he continued, "and maybe multicomponent can give a better understanding of where these high pressure zones exist."
Myriad issues must be resolved before the ocean bottom cables used for 4-C data acquisition become commonplace in the deep water environment.
"An issue we all face in deep water is knowing where the cables are," Caldwell said.
This is because of the effect of the deep water on the acoustic waves triggered by the cable transponder when it responds to a transmitter set off with the pinger system used for cable location.
Also, the deep water cables must be exceptionally strong, and work remains to be done on the cable handling systems, according to Caldwell
He noted that one thing keeping the deeper water cost high is the small amount of equipment to work with compared to shallow water, where systems have a lot of capacity of the type cable to allow the jobs to be done more efficiently.
Equipment issues -- along with the fact that industry is low on the learning curve -- contribute significantly to the current high cost of multicomponent seismic surveys relative to the towed streamer, where multiple streamers make for cost-efficiency. Even the multicomponent phones are ten times more expensive than hydrophones, according to Lawrence at Fairfield.
In the onshore arena, only the three-part geophone is needed to record the data, so the application becomes a three component, or 3-C, technique. Multicomponent seismic has been used there for about 20 years, particularly in the 2-D milieu, where BP Amoco (nee Amoco) has long been at the forefront.
"The methodology is robust in determining fracture intensity and also orientation from polarization of shear waves," said Mike Mueller, senior geophysical associate, "and this has been our most common application, along with reservoir characterization issues."
Looking Ahead, Looking Good
Onshore 3-D multicomponent seismic was first implemented in 1987 by the Colorado School of Mines Reservoir Characterization Project, which is now busy evaluating the first onshore time-lapse multicomponent, or 4-D, 4-C, survey.
The project kicked off in 1995 at Vacuum Field in New Mexico, where the objective is carbon dioxide flood monitoring.
Results are looking good.
"We see quite a distinguishable anomaly associated with the flood, and we think this opens new territory for CO2monitoring and other types of production process monitoring as well," noted Tom Davis, director of the Reservoir Characterization Project. They continue to shoot surveys as the flood expands, and Davis said they are currently using a telemetry recording system that records the same amount of data in 12 hours that they formerly acquired in 24 hours.
Time lapse multicomponent is in its infancy offshore. After acquiring a 3-D survey at Eugene Island Block 354 in 1997, Texaco initiated what became a joint consortium effort under the auspices of the ERCH to conduct a time lapse project there.
A not uncommon ocean bottom cable problem occurred early on. Instruments were left in a permanent location to improve repeatability, and much later it was discovered that two of three cables of instruments were missing, presumably dragged away by shrimpers in the 280 feet of water, according to Sparkman.
"In the last month, we have deployed buried cables to try to make them more permanent and protect them," Sparkman said, "and the data will be acquired by early April."
The industry is optimistic these types of projects can lead to better reservoir description and management.
Noteworthy for oil and gas finders, also, is the potential for other ocean bottom cable applications, which tends to be overshadowed by the euphoria over shear wave technology.
"Multicomponent doesn't just mean converted or shear wave, but it implies new pressure wave methods as well," Mueller said. "An ocean bottom seismic survey can acquire data in different ways than do streamers, and this opens up new techniques for all seismic modes -- pressure, shear and converted."
Meanwhile, even though 2-D multicomponent seismic results are available in the public domain, widespread availability of 3-D results is a ways off. According to Caldwell, the first 3-D, 4-C data sets have only recently been delivered, and early results are highly encouraging.
And while the technology is subject to growing pains now with a need for new equipment and skilled processors and interpreters, optimism is high for the future.
"Multicomponent technology should be able to provide another increase in success rates like 3-D did," Lawrence said. "It's out there, it's been proven, and I predict the entire Gulf of Mexico will be re-shot with multicomponent at some point in time in the near future.
"It will be economically driven, like any other thing."