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BP doing another Ugnu heavy oil test Producing oil at Milne Point S-pad test facility from a second horizontal well to further evaluate feasibility of cold extraction Alan Bailey Petroleum News
Following last year’s successful test of heavy oil production from the shallow Ugnu formation at Milne Point S Pad on Alaska’s North Slope, BP has been doing some further testing using another well at its heavy oil test facility. The new test well has been in operation since April 10, BP spokesman Steve Rinehart told Petroleum News May 29.
“It’s been producing steadily so far at around 350 barrels a day,” Rinehart said.
The Alaska Oil and Gas Conservation Commission has told Petroleum News that Ugnu heavy oil production totaled 4,123 barrels in April.
Major resource There are an estimated 12 billion to 18 billion barrels of heavy oil in the Ugnu, a potential major resource. But, with a thick syrupy consistency, the oil will not flow unaided through a pipeline and no one knows whether large-scale production of the material is technically feasible or commercially viable. In addition to the challenges of extracting the oil from underground rocks and transporting the oil from wellheads, the oil has a lower commercial value than conventional light crude.
Although there are several potential techniques for heavy oil production, some involving the heating of the oil to reduce its viscosity, BP thinks that the most favorable approach to producing the oil from the Ugnu at Milne Point is cold extraction using an augur-like downhole well pump to suck the oil to the surface. An electric motor at the surface rotates the downhole pump rotor using a rod that passes down the well.
In 2008 BP succeeded in producing some oil from the Ugnu from a test well at Milne Point S pad using a technique called cold heavy oil production with sand, or CHOPS, in which the downhole pump draws a mixture of sand and oil to the surface from a near vertical well. At the surface the mixture is heated in a tank to separate the oil from the sand.
Test facility Encouraged by this initial success, BP proceeded to build a $100 million heavy oil test production facility at S Pad. The company also drilled four wells — two vertical wells and two horizontal wells — to test various configurations of the cold production technique. The wells also penetrate different sections of the Ugnu reservoir — the Ugnu was laid down by an ancient river system, with the most promising reservoir rocks consisting of large, unconsolidated sand bodies occupying multiple, stacked river channels.
Last year’s test at S Pad involved the use of one of the horizontal wells, with the well producing oil from April through to August. Production from a horizontal well involves the use of the same type of downhole pump as is used in a vertical CHOPS well, but with the pump located at what is referred to as the “heel” of the well, the section of the well where the well bore steepens from the horizontal en route to the surface. Rather than producing oil along with sand, as in a CHOPS well, a slotted well liner in the horizontal well enables the pump to draw down the reservoir pressure, causing gas to effervesce from the subsurface oil and thus drive oil towards the well. As oil enters the wellbore, the pump pushed it towards the surface.
Another horizontal For this year’s test, BP is using the other horizontal test well. That well has a shorter horizontal section than the well used last year and is positioned to penetrate a different and slightly less permeable section of the reservoir, Rinehart said. The idea is to change some of the test variables, to gather more data about the Ugnu reservoir characteristics, hopefully repeating last year’s success while using a shorter well in a less permeable zone, he explained.
BP is mixing the heavy oil produced from the Ugnu with viscous oil produced from the Schrader Bluff formation at S pad, with the mixture being shipped to the Milne Point field production facility for processing.
But, although BP is glad to be producing oil from the Ugnu, the purpose of the test is to produce data about the technical viability of heavy oil production, rather than to produce oil, Rinehart emphasized. BP does not have a specific end date for its heavy oil pilot program and it will likely take several years to figure out the feasibility of commercial production, he said.
The next test well that BP plans to bring on line is one of the near-vertical CHOPS wells, Rinehart said.
“I don’t have a date on that yet but we hope to do that fairly soon,” he said.
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