Gov. Deval Patrick will have a new chief of staff for the final months of his administration.

Officials said Thursday that Richard Sullivan, who currently serves in Patrick's cabinet as Secretary of Energy and Environmental Affairs, would take over next month as the governor's chief of staff, replacing Brendan Ryan, who is leaving the governor's office.

Sullivan is the former mayor of Westfield. He has served as the energy and environmental affairs since the start of Patrick's second term.

Undersecretary Maeve Vallely Bartlett will take over for Sullivan. Bartlett has also held several other posts in state government and with the U.S. Environmental Protection Agency.

Patrick is not seeking re-election and will be leaving office in January.