Stranded gas and environmental concerns are leading more operators to consider gas reinjection which, if poorly planned, could lead to a loss in reserves. This paper reports on extensive compositional simulation studies which were performed on a high permeability turbidite reservoir to investigate ways of obtaining benefit from the injection of an apparently immiscible gas stream.

A lean alternating rich horizontal gas flood scheme, using separator streams, was identified as being attractive. The ratio of lean to rich gas was examined and an optimum identified which allowed the greatest volume of lean gas to be sequestered into the reservoir whilst increasing recovery by 10% OIIP above a base waterflood for the reservoir studied.

In addition, sensitivities were performed to investigate the impact of geological uncertainties, the use of water as a buffer, and varying injection rates and total injection volumes.

This paper illustrates that the latest high definition geology and simulation models can now unlock the potential of such novel gas injection schemes. In the past, models were too coarse and numerical dispersion dominated the process. This effect was investigated in the grid refinement sensitivities that were done in preparation for this project.

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