1. A method for generating seismic fluid prediction data for a subsurface region, comprising: obtaining seismic data representative of the subsurface region; preconditioning the seismic data for amplitude-versus-offset (AVO) analysis, using a computer; generating, using the computer, seismic AVO attribute data for the subsurface region, including creating intercept (A) and gradient (B) seismic data using two or more angle stacks of the preconditioned seismic data; generating, using the computer, lithology prediction data with the two or more angle stacks of seismic data or with the intercept (A) and gradient (B) seismic data; generating, using the computer, an AVO crossplot for fluids to identify an initial AVO anomaly; and expanding the initial AVO anomaly using the lithology prediction data, thereby generating seismic fluid prediction data for the subsurface region; wherein expanding the initial AVO anomaly using the lithology prediction data comprises reversing a negative fluid prediction based on the initial AVO anomaly for a point indicated by the lithology prediction data to belong to the same lithology as a point having a positive fluid prediction.