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In this paper, two well management schemes are proposed for rate forecasting of production streams under multi-level rate constraints. Each rate stream may be obtained from decline analysis, simulation or other means and may represent that from an individual well, a group of wells, or a separate field. in the first scheme, the well management problem was formulated as a linear programming (LP) problem and solved by the standard Simplex method. Although the solution is rigorous, the computer time for repeated solution of the problem over many time steps can be excessive. A second, approximate scheme was developed that gave results in close agreement with the LP results (within 5%) for most cases. in addition, this scheme reduces the computing time for a solution by about a factor of 4, which makes it more suitable for incorporation in a reservoir simulator. A computer program, based on the approximate scheme, was developed and used for predicting rates for several North Slope reservoirs. A second computer program, using the LP approach, was used to check the accuracy of the approximate scheme as well as another approximate scheme proposed in the literature.
In addition to being a stand-alone tool for rate forecasting, the approximate well management logic has been incorporated in a black-oil reservoir simulator with an explicit formulation. With this type of formulation, the well management logic ensures that the field oil rate is maximized at every time step in the simulations provided lift gas is unimportant.
Many producing reservoirs have some production and/or injection constraints that limit oil production. It is quite common on the North Slope and on offshore platforms that production is restricted by facility limits. A well management routine is necessary in a reservoir simulator to model the facility limitations because it could have a large impact on any rate forecast made by a reservoir simulator. Alternatively, if a reservoir simulator is not used, rate forecasting under production constraints can be carried out by a well management program if multiple streams of production are provided from wells, fields and/or drillsites, etc. These rate streams may be obtained by analogy, decline curve analysis of actual production data, simulation, or other means.
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