Estimation of CHOPS Wormhole Coverage From Rate/Time Flow Behaviors

Abstract

Summary In wormholed reservoirs with cold-heavy-oil-production-with-sand (CHOPS) wells, regions covered by wormhole networks are estimated by analyzing rate/time flow behaviors along with pressure and sand-production data. In this work, the concept of effective wormhole coverage is proposed as a proxy of the drainage region of CHOPS wells with complex wormhole networks. The wormhole intensity is defined as the total length of wormholes per unit effective wormhole coverage. A CHOPS flow model is developed by use of the boundary-element method (BEM) to account for various boundary conditions, wormhole morphologies, and effects of wormhole dynamic growth. Transient pressure and rate responses calculated by the model are validated by comparing with analytical solutions and numerical simulations. Modeling results show that the effective wormhole coverage and wormhole intensity within the region dominantly affect the characteristics of pressure and rate/time behaviors, regardless of the detailed wormhole morphologies. Accordingly, dimensionless pressure and rate type curves are developed to match flow behaviors, such as wormhole linear- and transitional-flow regimes to estimate effective wormhole coverage of CHOPS wells with available field data. This work extends the literature with fast type-curve matching of pressure and rate/time behaviors instead of generally practiced numerical-simulation routines. A field case with rate and sand-production data is successfully analyzed to show great potential of applying the proposed approach to characterize CHOPS wormholes.