Then company geologists have to turn hundreds of millions of points of this vibrational or seismic data into a 3-D map for determining whether or not oil deposits lie below. Such map-making is an iterative process. First, a computer processes the raw data. Then, looking at vertical sections, the map maker picks out a few points where he or she sees something interesting – where it looks like the sound waves have echoed off a particular kind of geological structure, such as a salt deposit.
The new algorithms developed by Willsky’s group and in use by Shell can define statistical relationships between the data points selected by the map makers, and use these relationships to connect the dots and create a map. The algorithms also calculate the uncertainty of each data point.
“The computer can take days to generate a complex surface, and the interpreter takes days to go through the data,” says Sears.
“One hundred percent success is a rare circumstance,” says Ron Masters, a senior staff geophysicist at Shell. “You have to drill a lot of prospects,” some of which will not bear out map makers’ predictions.
Shell and Willsky hope that ever-more-sophisticated algorithms will help the map makers do their job more quickly and with greater accuracy, especially as the company continues to look for oil in more geologically complex areas, such as those around salt deposits.
According to Masters, salt deposits are a dominant characteristic of the deep waters of the Gulf of Mexico. But he says the mapping algorithms developed by Willsky should apply to other geologically complex deposits elsewhere in the world’s oceans.