Placerita oil field operator Berry Petroleum Corp. posted a third-quarter net profit Thursday of $134 million ($2.45 per share) – a reversal of a year-ago $3 million loss.

But the improvement wasn’t enough to prevent stock prices from slipping more than 12 percent on the day to $37.66 due to the announcement that state regulatory requirements were slowing the pace of future oil exploration in a Kern County field where it recently gained approval to drill.

“Like other California producers, we are being impacted by today’s regulatory environment in California,” Berry President Robert Heinemann said. “While Berry received approval for our full diatomite development in the third quarter, the pace of drilling and steam injection is being slowed by the new, more stringent operating requirements of the state regulatory agencies. While this will impact our development pace in the near term, our estimates of well performance and ultimate recovery for the asset remain unchanged.”

“We are investing additional capital in our other assets to compensate for the slower pace of development in the diatomite,” he said. “We were not able to shift our capital soon enough to make up for this impact and are lowering our production forecast to approximately 10 percent growth for 2011 with full-year capital expenditures of over $500 million. Looking forward to 2012, we plan to maintain our strategic focus on oil development, expect to deliver double-digit growth in production and cash flow, and invest capital within cash flow.”

During the third quarter, the company boosted earnings by increasing production of oil and gas from existing reserves and selling it at higher prices. Oil production increased 6 percent on the year and 4 percent since the second quarter to 36,916 barrels per day, with an operating margin of $47 per barrel during the latest quarter.

Founded a century ago in Taft, Berry owns and operates multiple California assets including the Placerita field west of Sierra Highway in Newhall. Now headquartered in Denver, the company expanded beyond the Golden State in 2003 with operations in California, Colorado, Texas and Utah.