Abstract

In this paper, a radial-composite CHOPS well model, integrating foamy oil flow and complex wormhole configurations, tends to investigate how wormholes and foamy oil can affect pressure responses of CHOPS wells simultaneously. Heavy oil starts containing dispersed gas and forming relatively continuous foamy oil when pressure drops below certain point. Such foamy oil with high compressibility and pressure-dependent properties makes the partial differential equations highly nonlinear and existence of wormholes makes them more difficult. Pseudo variables of pressure and time, introduced in this paper, aim at solving such nonlinear problems. Unsteady state problems of this model were solved semi-analytically using source and sink function methods. Generated type curves provide new transient pressure behaviours of mature CHOPS wells with wormholes and foamy oil flow. They show that effects of wormholes mainly dominate the early time flow period, while distinct fluid properties between foamy oil and original heavy oil zones start affecting late time flow period when pressure disturbance has reached the interface. Foamy oil compressibility can affect pressure responses significantly during late time flow period because it is very different from original heavy oil. With known foamy oil properties, this model provides new perspectives of transient pressure analysis of field pressure data to estimate wormhole coverages and drainage areas of foamy oil zones, which are very important in post-CHOPS development such as infill well drilling and EOR planning.

You can access this article if you purchase or spend a download.