Breaking of a Paradigm: The Simultaneous Production of the Gascap and Oil Column

Abstract

Abstract The conventional way to produce an oil reservoir that has a gascap is to produce only from the oil column while keeping the gascap in place so that it can expand to provide pressure support. Depending upon the geometry, reservoir dip angle, and oil production rates, gas can either cone down to the oil producers or breakthrough as a front, leading to substantial increases in the gas-oil ratios of the oil producers. This paper presents a unique production methodology of simultaneously producing the gascap and oil column while injecting water at the gas-oil contact to create a water barrier to separate the gascap and oil column. This methodology has application in reservoirs with a low-dip angle, relatively large gascap, and a low residual gas saturation to water. It is demonstrated that the net present value of the project is improved if there is an immediate market for gas. The work also demonstrates that the recovery from the gascap is minimally affected by heterogeneities in the reservoir. This is shown using geostatistical reservoir models. The effect of heterogeneities on oil recovery is also documented. P. 431