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New seismic will produce better wells BP winter 3-D program at Alaska’s Prudhoe Bay field included area never before shot at Deadhorse airport Kristen Nelson Petroleum News Editor-in-Chief
BP Exploration (Alaska) has completed a seismic survey over most of the Prudhoe Bay reservoir, updating seismic data from the 1980s and 1990s, and shooting areas at Deadhorse never before surveyed.
Gordon Pospisil, field-wide depletion and forecasting manager, Greater Prudhoe Bay, told Petroleum News April 30 that even though the company had seismic over most of the area, it was older technology.
Newer technology uses a network of geophones, he said, and “you get information from all the different angles… that allows you to build a three-dimensional picture of these layers.”
In the past, he said, we might be able to see something — like a fault — as little as 80-feet thick, but using new technology and a higher density of signal receivers, “now we can see something that’s down in the 40 to 50 foot thick zone.”
The new seismic will help BP “to much better resolve what the remaining oil targets are throughout Prudhoe Bay,” Pospisil said.
The seismic acquisition has just been completed, he said, and between now and September it will be processed and used to create new cross sections and maps. After that, he said, “we’ll be generating field-wide maps and starting to influence the wells that we’re drilling.”
BP already sees the potential that “we’ll have on the order of 200 wells that will benefit from this new, improved picture. We’ll drill better and different wells than we would have without the data,” Pospisil said.
Those penetrations, which he characterized as “200 — plus or minus 50,” will be drilled as part of ongoing programs over the next five to eight years.
The purpose of the survey, he said, “is to improve the quality of future wells.”
BP has been drilling 50 to 70 new penetrations a year in Prudhoe Bay, mostly “sidetracking wells that have played out, that have reached low oil rates either because the gas has migrated to the well bore or water has broken through from offset water injectors. So we’re actually sidetracking to new targets within the same region where we can identify higher oil saturation.” There are now some 1,300 wells in the Prudhoe field.
Some new areas surveyed The seismic survey covered 180 square miles and included all of the facilities at Prudhoe Bay and the Deadhorse Airport, “which has never been surveyed before” because of logistics problems involving airport operations. Seismic was also shot through Deadhorse itself, involving coordination with contractors and local and state leaseholders.
Pospisil estimated that the area never before surveyed was probably some 600 to 800 acres, “several well spacings where we didn’t have information.”
Since this is all within Prudhoe Bay “and within the footprint of the existing facilities,” targets identified can be reached from existing pads. The improved imaging, he said, “lends itself to what we now understand is a game of pursuing smaller and smaller targets … the remaining interval areas that haven’t been swept effectively.”
Most of these targets will be drilled with coil tubing, Pospisil said: “We’re actually using existing well bores, tubulars, and drilling out of the tubing to a new location, running smaller tubing and then creating a new well, a new penetration, and it’s very cost effective.”
Prudhoe wells cost an average of $1.5 million for a coil tubing well to $7 million for a new well, he said, with an average well costing in the range of $3 million. Zero days away from work incidents Pospisil said the survey, which took place over 100 days, involved 130,000 man hours of work from some 100 on the WesternGeco crew and involvement from some 400 others who were contacted in the course of the operation, and 200 different entities “just to let people know essentially that we were operating equipment in the vicinity of their area and try to do it in a safe way without impacting operations.”
BP was pleased with the health, safety and environmental results from the operation. There were, Pospisil said, “zero days away from work incidents and essentially zero injuries, zero recordable injuries.”
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