Pacific Coast Energy Co., a private entity run by the founders of BreitBurn Energy Partners, late Wednesday announced a secondary offering of 13.5 million existing units in its publicly traded Pacific Coast Oil Trust.

Net proceeds from the sale will be used to pay down debt and for general corporate purposes.

Pacific Coast Oil Trust has royalty interests in certain California oil and gas properties in the Los Angeles and Santa Maria basins.

BreitBurn Energy Partners has energy-related interests inside and outside of California. All of the companies are based in downtown Los Angeles.

Pacific Coast Oil Trust closed down 1 cent, or less than 1 percent, to $17.98 on the New York Stock Exchange. Shares fell 6 percent in after-hours trading.