The five satellites in the western half of the Prudhoe Bay unit continue to see steady declines in production, and efforts to slow the trend could require technical fixes, according to a plan of development operator BP Exploration (Alaska) Inc. recently filed.
The five fields - Aurora, Borealis, Midnight Sun, Orion and Polaris - saw year-over-year declines in daily production rates ranging from 5 to nearly 17 percent, according to BP. While the declines are expected given the general lack of drilling in the past year, the future of those fields depends largely on efforts to develop viscous oil in the region.
Those efforts have been progressing for years, held up by technical, economic and political issues. Now, BP believes it needs to verify the effectiveness of sand control technology before it can build a proposed I pad or expand the existing S pad and M pad.
The Aurora field
Mobil Oil Corp. discovered the Aurora oil pool in the northwest corner of the Prudhoe Bay field in 1969, although BP brought the field online from S pad in November 2000.
As of July 2015, the Aurora field had 33 wells - 18 oil producers and 15 water-alternating-gas injectors, according to the most recent annual report. At the start of 2014, the field had 17 producers, 10 water injectors and six water-alternating-gas injectors.
Of the estimated 200 million barrels of oil in place at Aurora, BP had produced some 39.46 million through June 2015, according to the company. The field averaged 4,305 barrels of oil per day in the year ending June 30, 2015, down from an average of 4,655 bpd in the previous year and down from a peak of 14,000 bpd in August 2006.
During the recently completed year, BP drilled three new production wells at the Aurora field. The S-42A sidetrack will replace the S-108 producer, which BP plugged and abandoned after finding collapsed tubing and casing during a workover. The S-44A sidetrack is north of the existing S-101 injector, which was also repaired this year. BP expects to bring those two wells into production by the end of the year. The S-135 well was brought online in October 2014 at an initial rate of 884 barrels of oil per day.
The company said it is using geologic models to evaluate additional wells for future drilling during the coming year, including a potential producer to accompany the existing S-107 injector and a potential injector to accompany the existing S-105 producer.
Also during the year, BP repaired the suspended S-104 injector, converted the S-128 water-alternating-gas injector to miscible injectant and conducted a hydraulic fracturing operation on S-129, which yielded a post-frack production rate of 2,486 barrels per day.
The Borealis field
Mobil Oil discovered the Borealis oil pool along the western edge of the Prudhoe Bay field in 1969. BP brought the field online in 2001 from the Prudhoe Bay L pad, and expanded development to include the V pad in April 2002 and the Z pad in March 2004.
As of July 2015, the Borealis field had 57 wells - 25 from L pad (the same as last year), 22 from V pad (the same as last year) and 10 from Z pad (one more than last year), according to the most recent plan of development. Of the estimated 350 million barrels of oil in place at Borealis, BP had produced 77.8 million through June 2015, according to the company. Borealis produced 8,768 bpd during the year ending June 30, 2015, down from 9,932 bpd the year before and a peak of 38,150 bpd in May 2003.
During the previous year, BP repaired two wells at V pad and equipment associated with one well at Z pad and began preliminary maintenance on a well with communication issues. The company is planning to begin miscible injection at a well on Z pad.
The company also finished reprocessing the S3 3-D seismic survey earlier this year.
This year, the company is evaluating potential infill opportunities at Z pad.
The Orion field
Mobil Oil discovered the Orion oil pool in the northwest corner of the Prudhoe Bay unit in 1968. BP confirmed the accumulation in 1998 and brought the field online in 2002.
BP originally developed Orion from its V pad and expanded development in mid-2004 to include L pad. As of July 2015, Orion had 49 wells - 25 from V pad (the same as last year), 23 from L pad (the same as last year) and one new injector drilled from Z pad. Of those 49 wells, 12 are active multi-lateral producers and 34 are active injectors.
Of the 3.2 billion barrels of oil in place at Orion, BP had produced 32.1 million through June 2015. Orion produced 4,693 bpd in the year ending June 30, 2015, down from 5,483 bpd the previous year and down from a peak of 14,460 bpd in June 2007.
While BP did not drill at Orion this past year and has no plans to drill this coming year, the field is part of a larger regional endeavor to economically develop viscous oil. Orion produces from the same viscous Schrader Bluff formation present at the Milne Point unit to the north and portions of the ConocoPhillips-operated Kuparuk River unit to the west.
Many projects underway at Orion are related to the viscosity of its oil. For example, BP is currently studying ways to improve Gathering Center 2 to better accommodate viscous oil. The facility was designed for light oil and improvements in 2012 and 2013 to improve solids handling have “not yielded the desired level of improvements,” according to the company. Similarly, BP conducted geomechanical studies and enhanced dynamic models this year to better understand “subsurface uncertainties” related to viscous oil.
Those efforts are expected to continue this year, as is an ongoing program to reduce the rate of downtime for viscous wells, which has hit 50 percent in some sections of the field in recent years. For years, the company has been considering a multi-stage trial to better understand the project but has deferred the project “due to the current business climate.”
Another deferred project at Orion is the proposed I pad.
While BP had originally expected to bring the pad online by 2006, the company has since deferred the project twice: first until 2010 and currently until as late as 2020. The program presents considerable technical challenges but has also been at the center of political debates over the past decade. The two deferrals followed changes to the state oil production tax by the Murkowski and Palin administrations and was a prominent point of discussions during legislative hearings over then Gov. Sean Parnell’s tax code changes.
In its previous plan of development, BP told state officials that the original location for I pad had “proved to be unfeasible” because it was “constrained” by a Milne Point road to the west, a large lake to the east and a subterranean ice lens to the north. While that problem had a solution, the company also said the future of I pad “depends upon finding ways to more efficiently execute the project and reduce project uncertainty and risks.”
This year, BP said the future of I pad “will be informed by the results of sand control technology in the Schrader Bluff formation. If a trial of sand control technology is successful, the learnings will be considered in Orion development planning.”
An I pad could access 69 million to 144 million barrels of recoverable oil at Orion and 2.7 million to 3.9 million barrels of recoverable oil at Borealis, according to the state.
The Polaris field
BP discovered the Polaris oil pool in the western end of the Prudhoe Bay field in 1969, while delineating the field, and brought the field online in 1999 from W pad and S pad.
As of July 2015, Polaris had 28 wells - 21 from W pad and seven from S pad, the same as last year. Of the estimated 1 billion barrels of oil in place at Polaris, BP had produced 18.7 million through the end of June 2015. The field produced 3,890 bpd in the year ending June 30, down from 4,080 bpd the previous year and a peak near 7,000 bpd.
While BP drilled no Polaris wells last year and is planning none for this year, the company is dealing with many of the same issues occupying its attention at Orion.
And just as sand control technology is holding up the proposed I pad development at Orion, it is also holding up a proposed expansion of the S pad and M pad at Polaris.
The Midnight Sun field
BP discovered the Midnight Sun field at the center of the northern edge of the Prudhoe Bay unit in 1997 and brought the field online from the E pad in October 1998.
Through July 2015, BP had drilled six wells at E pad. The most recent was an injector drilled this year and was the first new well since 2001. Of an estimated 100 million barrels of oil in place at Midnight Sun, BP had produced some 20.4 million barrels through June 2013. Production is now 964 bpd, down from 1,106 last year.
After drilling the extended-reach P1-122i miscible injection well at the Midnight Sun field earlier this year, BP said it has no plans for drilling activity during the coming year.
