Seismic innovations aid BP at Milne, could spur viscous oil development

Shallow-draft boats shot 3-D seismic this summer; 3-D vertical profile seismic planned for five injector wells in early 2002 will be first for BP, North Slope

Kristen Nelson

PNA Editor-in-Chief

Innovative three-dimensional seismic is part of BP's work plan at Milne Point. After BP Exploration (Alaska) Inc. acquired Milne Point from Conoco in 1994, a 3-D seismic program was shot at the field. It was part of the Milne Point expansion program that created the big step change in production, from 20,000 barrels per day to today's 55,000 bpd field, Ed LaFehr, BP's Milne Point asset manager, told PNA Dec. 14.

There were a couple of small 3-D seismic surveys shot later, he said, and then this summer, in the Milne lagoon north of F pad, seismic was shot from shallow-draft boats using ocean-bottom cable. The work was done over a three-week period because of environmental restrictions, LaFehr said.

The shallow-draft boats let the crew get “into shallower water than we've been able to get in before.” LaFehr said that seismic shot from ice in the winter is problematic if the ice isn't grounded because the data will have noise in it. Some new equipment was brought in for the ocean-bottom cable shoot this summer and using the shallow-draft boats, BP got “quite a good picture of Milne Point off to the north.”

Extended reach drilling to the north of the field has never found an oil-water contact, LaFehr said: “It's a very flat and broad structure off to the north.”

The new seismic will let BP go after the area to the north with minimal environmental impact, he said: “This is what we call our BP brand at work.” BP will be able to go after the oil from existing onshore infrastructure without building an island. Using the new 3-D seismic, BP will be able to “target the patterns, where the producers and injectors would go.” But LaFehr said extended reach drilling has its own set of issues. BP is still working on reducing the cost of extended reach drilling, he said, and isn't planning to drill these projects next year.

3-D VSP will be first for BP, North Slope

Vertical seismic profiles, or VSP, are shot all over the world in exploration wells, LaFehr said: “They hang a string of acoustic phones down a well and then they collect data with vibrator trucks as they back off around the well and shoot. And they come up with a data set that's essentially a cone around the well.”

This winter, he said, BP is going to do a simultaneous shoot around five or more injectors. This is a new technique. A company out of California uses special equipment and special processing to shoot 3-D VSP, LaFehr said. They have only done a couple of these surveys, one in California and one in West Texas.

The technique is new to both BP and the North Slope. In fact, he said, “we're paving the way for some of our biggest developments in the world in the deepwater Gulf of Mexico and other areas.”

“We believe this technology has tremendous potential for helping us to see the viscous reservoir and at the same time we're sort of the guinea pig to try and make this fly for other areas of BP worldwide,” LaFehr said.

The S-pad injectors will be drilled in January and the survey will be shot in March.

Once the Milne Point VSP survey is shot, the data will be processed and interpreted to create a 3-D image of the earth. It costs less than a surface survey, LaFehr said, and “it's environmentally extremely friendly because you're not putting geophones out all over the tundra…

“It's easy to permit, it's easy to do, it costs less and it may provide us a better image of the reservoir,” he said.

What BP will be getting will be “a detailed high-resolution picture of the shallow earth” — this survey is aimed at viscous oil at Milne Point. Further application of this technology is designed to take the permafrost out of the picture entirely because the phones sit below the permafrost, LaFehr said.

It's a first for the slope, a first for BP, and if the technique is successful, it could be used at other developed fields. Prudhoe Bay is “looking at it pretty hard,” said LaFehr.