Gas encroachment has halved the drawdown rate for the U.S. Strategic Petroleum Reserve.
DOE discovered last year it would have to pump 200 million bbl of oil from the 577.3 million bbl SPR and degasify it (OGJ, May 3, 1993, p. 130). But the department said the SPR's 4.3 million b/d potential drawdown rate would be reduced only 400,000 b/d.
However, DOE told the House appropriations committee it could pump only 2 million b/d from the SPR in the event of a supply emergency.
THE PROBLEM
DOE said over the years, gas from surrounding formations has penetrated some of the salt dome storage caverns at Bayou Choctaw and West Hackberry in Louisiana and most of the caverns at Big Hill and Bryan Mound in Texas.
The stored oil contains 1-5 cu ft/bbl, which will have to be removed before the oil can be used. Also, some of the crude has an increased vapor pressure due to geothermal heating.
To lower the oil temperature, heat exchangers will be installed on pipelines that carry crude from the SPR sites. DOE, which is seeking bids for the equipment, plans to complete the $25 million modification by February 1995.
DOE plans to award a degassing service contract in August. Degassing would begin in February 1995 at the rate of 200,000 b/d. Treatment of all oil containing excess gas will take about 3 years at a cost of about $35 million.
DOE said 65 million bbl of SPR oil contains too much gas, and another 135 million bbl has excess gas, elevated temperature, or both.
INTERIM SOLUTION
"Until that oil is degassed and heat exchangers are installed," DOE said, "the SPR program would make that oil available by blending hot, gassy oil with remaining oil to reduce the overall gas and heat content to an acceptable level and slow the drawdown flow rate of the oil to allow natural cooling to take place while the oil is still contained in pipelines under pressure.
"As a result, the initial drawdown rate for the SPR is now 2 million b/d. After installation of heat exchangers in March 1995, the capability will be increased to 2.5 million b/d. The drawdown rate will steadily improve as gas is removed from oil at a rate of 200,000 b/d through 1997."
The SPR's overall distribution capability increased to 4.1 million bid from 3.9 million b/d in May 1993 when the Big Hill pipeline was connected to the Texaco Inc. pipeline system from Port Arthur to Houston. And it rose to 4.3 million b/d last October when Unocal Corp. completed a marine terminal at Nederland, Tex.
Copyright 1994 Oil & Gas Journal. All Rights Reserved.
