An investigation is presented on the use of Flow Control Valves (ICVs, FCVs) to control steam placement in the early stages of a Steam Assisted Gravity Drainage (SAGD) process. The two parts of this process that are examined in this paper are the steam circulation preheating period and the early stages up to one year of injection/production in which the steam chamber is beginning to form. Steam injection and production in this and other thermal processes can be difficult to control because steam has a high mobility ratio and tends to establish flow paths that may be difficult to break once established. This is especially pronounced in heterogeneous reservoirs. Two SAGD case studies have been designed that accurately model the initial preheating period in which both wells circulate steam through an inner tubing and outer annulus in order to conductively and, to a lesser extent convectively, heat the region around the well pair in order to establish communication. After this initial circulation period, the wells switch to injection and production. Both cases have the same base configuration but differ in the degree of reservoir heterogeneity. In the injection well, ICV devices are placed to control steam/water flow through the outer screens. In the producer, FCV valves are used to flatten the production profile along the well. Two methods are examined to change valve apertures. One uses proportional-integral-derivative (PID) controllers while the second applies an optimization algorithm directly on each individual connection productivity index. A preliminary investigation is presented here into using feedback controllers and optimization with instantaneous reservoir parameters to improve a SAGD process in the presence of reservoir heterogeneity.
This paper describes the modeling of single and dual tubing wells in a full-field reservoir simulator. The tubings associated with each well are modeled in terms of one primary and one or more secondary wells. The multi-segment well modeling techniques incorporated in the simulator have been extended to model multi-tubing systems thereby avoiding the requirement to model special grid blocks representing a wellbore. Wells with two or more tubings present a significant challenge to reservoir simulation where traditionally the coupling of the well with the reservoir, however complex, is solved in terms of a single surface inlet or outlet.The case studies have been selected to demonstrate that injectors and producers can both be modeled in terms of primary and secondary wells both with targets and constraints. Comparisons are presented showing the differences between single and dual tubing injection and production schemes. An example of a multi-tubing production schemes is also included. These demonstrate that modeling wells with two or more tubings using the multi-segment well approach is practicable for the simulation of hydrocarbon recovery processes.
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