Modelling of Stimulation Fluid Placement and Flow in Carbonate Reservoirs

We report the development of a model to support matrix-based stimulation treatments in limestone reservoirs that takes information directly from data obtained during core flooding, such that the model can be calibrated against a variety of novel stimulation fluids under conditions directly representative of the candidate field. The model builds on an earlier stimulation model developed for clastic reservoirs, which primarily addressed stimulation as a formation-damage-removal phenomenon; it maintains the 3-dimensional aspects of the earlier model but incorporates the substantially greater complexity required in coupling the damage-dissolution reactions to the hydrodynamic phenomena associated with the formation of wormholes. Wormholes are an ideal method of stimulating carbonate reservoirs (in the absence of massive hydraulic fracturing) but their formation is stochastic, anisotropic, and involves greater morphological changes. Hence, successful stimulation depends on formulation chemistry, application rates, rock morphology, pressure, and temperature. This initial model has been calibrated to describe the behaviour of a selection of non-standard stimulation fluids, which have been evaluated in part through core-flood performance. The reaction-rate data for these novel fluids was abstracted from a series of core flood experiments with effluent and morphological analyses. The user interface provides easy condition input and selection and provides a clear output of results. Future developments will expand the model to a broader range of conditions and chemical formulations.