Reservoir Performance Under Solution Gas - Drive and Gravity Drainage

This work examines the well and reservoir performance under both solution gas-drive and gravity drainage in homogeneous systems. Based on synthetic information obtained with a fully implicit black-oil simulator, the influence of different parameters like oil rate, position of the producing interval, wellbore pressure level, skin factor, and vertical permeability, for both constant oil rate and constant pressure production modes are documented. Analytical results for the reservoir performance during the boundary dominated flow period are derived. An approximate expression that describes the variation of oil saturation with average pressure is presented. For constant oil rate production, the influence of gravity drainage on the inflow performance relationships curves is studied, and a new correlation is presented. For constant pressure production, the decline curve behavior is analyzed and it is found that under favourable gravitational effects, the production behavior shows two decline stages such as double porosity systems; however, it does not follows the typical decline type curves for naturally fractured reservoirs. At certain backpressure values during the first stage an exponential decline behavior could be observed, while during the second stage values of the decline exponent less than zero are observed.