SAN RAMON — Chevron has revealed plans to slash several hundred East Bay jobs, a wrenching downsizing that arrives on the heels of the energy giant’s decision to move its headquarters to Texas and exit California.

The Texas-based oil company decided to chop 600 jobs in San Ramon, where Chevron once maintained its headquarters over a period of decades.

“Chevron is taking action to simplify our organizational structure, execute faster and more effectively, and position the company for stronger long-term competitiveness,” Henry Perea, Chevron’s manager of state government affairs, wrote in an official WARN notice the company sent to the state labor agency.

The first rounds of the 600 job cuts are slated to occur on June 1 of this year, Chevron told the state Employment Development Department.

“We will have fewer positions and unfortunately, fewer people,” Perea stated in the WARN notice filed with the EDD.

The staff reductions will affect workers at Chevron’s large office hub at 5001 Executive Parkway in San Ramon, the WARN notice stated. Chevron referred to the San Ramon office site as Chevron Lakeside.

The vast Chevron refinery in western Richmond was not part of these staff cuts, which were confined to San Ramon.

More job cuts could occur, Chevron warned state government officials.

“We also expect further layoffs, but the scope and number for Chevron Lakeside have not yet been determined,” Chevron stated in the WARN notice.