Prudhoe-Lisburne commingling at well OK’d

Kristen Nelson

Petroleum News

The Alaska Oil and Gas Conservation Commission has approved commingled downhole production between the Prudhoe oil pool and the Lisburne oil pool in a Prudhoe Bay unit well, PBU L5-21, responding to a request from Prudhoe operator BP Exploration (Alaska).

The Lisburne oil pool, in production since 1982, is “a complex carbonate reservoir” underlying the Prudhoe oil pool, the commission said in its April 22 order. The Prudhoe oil pool, “an immense oil rim overlain by a massive gas cap,” has been in production since 1977.

The commission said the L5-21 well was completed in the Lisburne oil pool and has produced some 1.8 million barrels of oil since it began production in 1987.

“The L5-21 well intersects the POP in an area that contains liquids-rich gas,” the commission said, with commingling providing two benefits. The Prudhoe oil pool gas would “act as an in-situ gas lift” for Lisburne oil production, improving ultimate recovery from the Lisburne oil pool and would allow a small liquids-rich gas accumulation not swept with lean gas reinjection into the Prudhoe gas cap to be produced, increasing ultimate recovery from Prudhoe.

“These unswept gas accumulations are typically not large enough to warrant drilling of dedicated wells, but they are targets of opportunity when identified in existing wellbores,” the commission said.

The commission said crossflow between Prudhoe and Lisburne was possible, but “is not expected to be significant due to similar reservoir pressures in this portion of the Prudhoe Bay Field.”

Since the L5-21 is completed in the Prudhoe gas cap and the Lisburne oil rim, BP proposed that 100% of the oil and water production from the well be allocated to Lisburne and 100% of the natural gas liquids to Prudhoe.

The commission said in approving the request that downhole commingling between Prudhoe and Lisburne would “improve resource recovery from the Prudhoe Bay Unit by encouraging production of resources within the POP that would not be recoverable as a standalone development and by improving recovery from the existing LOP completion of L5-21.”

- KRISTEN NELSON