My former colleague John Smith, an expert on Pacific Region decommissioning, advises me that production has ceased at Platform Irene in the Santa Maria Basin offshore California. Irene, the first platform installed in the Santa Maria District in 1985, was a milestone in Pacific OCS development.
Only 7 of the 23 Pacific OCS platforms are still producing. Attached is an updated summary table that John prepared for an upcoming SPE event in Alaska.
More on California OCS decommissioning.
Bud's Offshore Energy (BOE) 
Why and when did production stop at platform Irene? Depletion? Economics? Regulatory?
Charlie, I’m not sure what the shut-in date was, but there was no production as of the first quarter of this year. I think it was largely a depletion/economics issue. The facility was installed in 1985 when I was working out there, and was the first platform in the Santa Maria Basin.
Thank you for the response. I was just curious if there was a specific event that lead to the shut in such as the Refugio beach pipeline spill that lead to the shut in of platforms Hondo, Harmony & Heritage. Depletion and economic factors are certainly a possibility.