The sublease will expire when BP's lease for the space expires in November 2013, says Robert Sevim, corporate managing director at Studley, which represented both law firms in the lease transactions.

Robert Goldwater & Associates, a Phoenix-based firm that specializes in personal injury, has already moved into its space, which is its first Chicago office, Sevim says. Petra is expected to move into their space in about six to eight weeks, Sevim says. The minority-owned law firm is currently using temporary space. The firms chose the Aon Center because of the reputation of the building and cache of having the Aon Center as an office address and because of the economic benefits of subleasing space, Sevim says. The normal asking lease rate is between $14 per sf to $16 per sf net for the mid-rise portion of the building. The firms were able to receive a more favorable rate by subleasing the space as opposed to if they were leasing the space outright, he says.

BP leases 600,000 sf in the building, which it vacated in 1999 when BP and Amoco merged. The two law firms subleased the last full remaining floor of space from BP but there are still full floors of space that can be leased in the building. The 2.7 million-sf building, which was constructed in 1972 and is owned by Wells Real Estate Investment Trust, is currently about 87% leased. Major tenants include Aon Insurance, DDB Chicago, Edelman and Xerox. "There are some significant leases expiring in the next couple of years at the Aon Center," Sevim says. Large chunks of space will become available when tenants move out, such as Kirkland & Ellis, which is scheduled to move into 600,000 sf of space at 300 N. LaSalle St. in 2009.