A Model Approach of Controlling Coning in Oil Rim Reservoirs

Abstract

Water and gas coning in oil rim reservoirs poses serious hindrance to optimizing oil production in the thin oil beds as unwanted fluids tend to replace oil in the production stream. This invariably limits the ultimate oil recovery. In this study, semi-analytical models of estimating critical rate and optimum horizontal well placement were developed to control coning tendencies in oil rim reservoirs. The models were developed through semi-analytical analysis of applying the principle of Nodal analysis to graphically combine gas-oil reservoir system and oil-water reservoir system respectively with a view to controlling gas and water coning phenomena in gas-oil-water reservoir system. The result was compared with an existing correlation with field data obtained from the Niger-Delta oil field. The models are simple for fast calculations for reservoirs with thin oil zones sandwiched between gas cap and bottom water. It is concluded that the developed models can be used as a tool to make a first pass assessment in the development of oil rim reservoirs anticipated to experience water and/or gas coning during production.

Keywords: Oil rim reservoirs, coning, critical rate, horizontal well placement