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Jet pumps put S pad on production
Kristen Nelson PNA Editor-in-Chief
BP Exploration (Alaska) Inc. put its new Milne Point S pad viscous oil development on production Sept. 1. S pad reflects a commercialization strategy for development of the Milne Point shallow Schrader Bluff accumulation that BP developed in 1999, David Jenkins, BP Exploration (Alaska)’s viscous team leader, told PNA Oct. 2.
There is viscous oil — thicker than the conventional oils at Prudhoe Bay and Kuparuk — on the North Slope from Kuparuk into Prudhoe Bay, and what BP has done at S pad could form the basis for other developments. At Orion, a west side Prudhoe satellite, “they’re looking to what we’ve done at S pad in terms of ideas they want to evaluate for how they put that development together,” Jenkins said.
BP purchased Milne Point in 1994 from Conoco, but for the deeper Kuparuk oil, not Schrader Bluff. Conoco had made a run at developing the shallow Schrader Bluff, Jenkins said, with a conventional approach that looked at “carpet drilling the area,” required a number of new drilling pads and came it at about a billion and a half dollars.
BP tried to improve on conventional development ideas and came up with a plan that had five new pads, 75 miles of new pipeline, 10 miles of new road and a price tag of more than a billion dollars. It just wasn’t economic.
A new plan What was economic is the plan BP implemented when S pad construction began in 2001: one new pad, 7.5 miles of new pipeline and one mile of new road.
In 1999 BP developed an approach to Schrader Bluff development focused on tripling well productivity from 300 barrels a day to 1,000 barrels a day and more; reducing life-cycle costs by half; reducing drilling costs by 30 percent; and reducing infrastructure costs.
Productivity was tackled with horizontal wells.
BP had drilled some initial horizontal wells into the shallow viscous formation in 1998 to prove the concept, Jenkins said: “And in 1999, we began a very focused development specific to long horizontal wells, with a move toward multilateral wells.” The first multilateral well at Schrader Bluff was drilled in 2000, and “by 2001 we were getting good at it,” he said.
The long horizontal wells push the limits of shallow extended reach drilling, and extend the reach from a pad from 7,500 feet with conventional wells to 10,000 feet, allowing drillers to reach the accumulation from one new pad, S pad, and extensions on some existing pads.
Jet pumps Life-cycle costs were a problem because electric submersible pumps, used to lift the oil, weren’t sand tolerant — Schrader Bluff wells produced a lot of sand — and “cost about $300,000 to replace every time they break. They break every two to three years,” he said, and viscous wells are expected to have 20-30 year producing lives. Compounding the problem is the production pattern of viscous wells, which have “a very long tail where the flow rate is relatively low,” below 200 barrels a day. The rate required to support a workover to replace an electric submersible pump is more than 200 barrels, so reserves are lost at the end of a well’s life because it isn’t economic to replace the pump.
Jet pumps solved that problem: the technology is “extremely sand tolerant” and “there are no moving parts down hole,” Jenkins said. The business end — a couple of feet long — can be replaced using a wire line unit, and the average cost to change it out is about $10,000, whereas a workover is required to change out an electric submersible pump and the work costs about $300,000.
“S pad is … the only pad on the slope where the sole artificial lift mechanism is jet pumps,” he said.
Five producers on line Five producers are on line, Jenkins said Oct. 2, and the second injector is ready to go on line. A sixth producer has been drilled but is not yet in production and a seventh producer is being drilled and will be completed before the end of October.
There have been challenges at S pad. “In actuality construction is a little bit behind,” he said. Most of the physical construction is complete, but not the functional checkout, which “means the actual facilities at the pad won’t begin production until about mid-November.”
BP’s target had been Sept. 1 production, and at the beginning of August the company tackled the problem of production with incomplete pad facilities.
“And it turns out,” Jenkins said, “there’s another benefit to these jet pumps… you can drive them all the way from the central processing facility instead of just driving them from on pad.”
A bypass was built around the artificial lift facilities on S pad — the surface end of the jet pumps. “We were able to take water directly from the central processing facility out to the pad, bypass all these facilities, go straight down the well, and take all the fluid directly back to the plant, bypassing the (pad) facilities,” he said.
BP was able to get its S pad wells on line on schedule, although at only about half capacity because the full facility isn’t up and running.
The five wells are each producing more than 1,500 barrels a day and the combined wells 8,000-10,000 barrels a day on about half of their lift capacity.
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