Exploring for oil and gas in the western Black Sea off the coast of Romania hadn’t been going well.
Several companies had explored in the region, but the search for hydrocarbons in deep waters was elusive until recently, when a cutting-edge imaging technology helped ExxonMobil discover and appraise a significant natural gas reservoir.
The new technology—full wavefield inversion—played a central role in getting a better understanding of the geology below the ocean floor. It assisted in finding better locations for exploration wells and accurately estimating the size of the discovery. It also helped in designing plans to cost-effectively bring the gas to market to create electricity and to help consumers heat homes and cook meals.
“Full wavefield inversion was critical to help with planning and execution of Black Sea appraisal wells and ultimately resource characterization and definition,” says Michael Deal, the Geoscience Operations Manager for ExxonMobil Development Company.
Accurately drilling into an oil and gas reservoir is important because it reduces the need for additional wells. This lowers costs, reduces the environmental footprint and improves safety. And just as important as finding where to drill new oil and gas wells is finding clues of where not to drill. It isn’t foolproof, but full wavefield inversion does provide energy producers more assurance on what lies beneath the surface.
Making good better
ExxonMobil invented 3-D seismic in the 1960s—the company was later awarded the Distinguished Achievement Award by the Society of Exploration Geophysicists for what it said was “the most important geophysical innovation in the past 30 years.” Until now, 3-D imaging was the most accurate method for locating fossil fuel deposits. The challenge with 3-D seismic was that it was difficult to process all the information with traditional computer algorithms.
Developing a technology that used all the available data to significantly improve the 3-D images of the subsurface layers was critical because it would improve chances of finding oil or natural gas. But scientists estimated that even the fastest computers would take up to thousands of years to process all the data to create such a rich image of the subsurface. That is, unless someone came up with an algorithmic breakthrough that could, in effect, drastically compress the computing time.
That breakthrough was full wavefield inversion technology. The ramped-up imaging technology doesn’t just highlight oil and gas potential. It goes one step further by providing accurate insights to the actual geological and geophysical properties of the subsurface rock layers.
Full wavefield inversion technology is able to provide such insights by using all of the sound waves captured by the seismic imaging microphones that were left out by conventional imaging technology and creating a digital model of the subsurface. To ensure accuracy, simulations using the digital subsurface model are iteratively compared with the actual sound waves generated from the field until a match is found.
This improved process gives geoscientists far more insight into the characteristics of energy-rich geological formations. And that means that oil and gas resources will be easier to identify, which will reduce the need for extra, costly drilling and enable energy supplies to be brought to market more efficiently.
“Full wavefield inversion represents a step change in seismic technology,” says John Eastwood, Seismic Acquisition and Imaging Manager for ExxonMobil Upstream Research Company. “It is able to provide our geoscientists an unprecedented level of detail, enabling them to see opportunities faster and more distinctly.”