Typical recovery factor for conventional heavy oil primary production has been reported about 1-5% of original oil in place. The recovery factor of cold production can be improved up to 5-20% using other techniques, Cold Heavy Oil Production with Sand (CHOPS) being one of them(1,2). CHOPS is a deliberate sand production with oil in unconsolidated sand reservoirs with an oil viscosity of 500 to 15000 cP. It is believed that sand production increases oil rate and makes the well to remain at the economic limit of cold production. Based on field observations and laboratory experiments, it creates cavity and wormholes at least around the well and possibly far further in the reservoir. This wormhole pattern not only increases the oil production rate, but also alters reservoir characteristics in a dramatic fashion.
Based on current literature, CHOPS offers a very low OPEX and CAPEX compared to thermal methods and surface mining. During CHOPS, many of the important properties of the reservoir change. Mathematically, it means a need for predictive and dynamic models and simulations for CHOPS. Unfortunately, due to dynamic changes of reservoir properties, no valid model is available to simulate CHOPS production. But, it is believed, after certain sand production period and in the beginning of subsequent enhanced oil recovery processes, these dynamic changes become very rare. Hence, a dual porosity approach can be practically employed for post-CHOPS studies.
In this paper, we present a partial dual porosity modeling approach with selective wormhole patterns, depending on the well perforations and geological properties. First, wormhole patterns are generated and introduced into a static model. It is assumed that wormhole properties are a function of its radius and it can be controlled along with its length and pattern, which facilitates history matching process. After validation of the model with available field data, different post-CHOPS scenarios are studied. Proposed simulation approach to create post-CHOPS is flexible and can be applied in both black-oil and compositional simulators.