SHERIDAN - A Canadian-based oil company that specializes in underground oil drilling is laying off more than half its work force, most of them in Wyoming.

The layoffs by Rock Well Petroleum Inc. resulted from a weakening economy and postponement of the company's plans for initial public stock offering on the London Stock Exchange, company spokeswoman Phoebe Buckland said.

Based in Calgary, Alberta, Rock Well announced Friday that it will lay off 180 people out of a total of 300 employees. Most of the layoffs are miners and drillers in Wyoming where the company's two largest projects are located.

However, Buckland said all positions in the company are affected.

John Hoak, the company's chief executive officer, said in a statement that the layoffs were "extremely difficult and painful."

"Economic uncertainties and capital constraints have forced us to revise our business plan and realign staffing levels to meet the needs of the company moving forward," Hoak said.

The company has been producing oil at two old fields in Wyoming by tunneling hundreds of feet underneath the fields and drilling up into oil that could not be extracted by traditional surface drilling methods. Gravity causes the oil to flow down the underground wells where it is collected.

Rock Well says it will continue to produce oil at the Osage and Greybull fields in Wyoming while it revises its business plan.

Within the last year the company has acquired mineral rights in northwest Pennsylvania and western Texas.