The deal looks like bringing in value and earnings in the long term for investors. BP will bring in it’s technical expertise and help RIL to optimize. RIL stock trades currently at forward (FY 12 estimated) P/E ratio of 12.8. Once the deal goes through, stock valuations may dip on account of shedding 30% share in east coast blocks. But this is expected to be recovered by cash consideration and rerating of blocks with BP’s technical expertise meeting RIL efficiency.

One may buy stocks of RIL for target price of Rs.1,175-1200 in next 1 year. I would update the valuations after regulatory approvals and more clarity on financials involved in deal.
Reliance Industries & British Petroleum deal : Stock recommendation