Flexible and adaptive formulations for complex reservoir simulations
First Claim
1. A method of performing a simulation of a subsurface hydrocarbon reservoir, the reservoir being approximated by a reservoir model having a plurality of cells, each cell having associated therewith an equation set representing a reservoir property, the method comprising:
- (a) determining a stability limit for each of the plurality of cells;
(b) assigning each cell to one of an explicit formulation or an implicit formulation;
(c) providing an initial guess to a solution for a system of equations formed using the equation set for each cell in the plurality of cells;
(d) using the initial guess to solve for a solution to the system of equations using an explicit formulation for cells assigned thereto and an implicit formulation for cells assigned thereto;
(e) establishing a list of unconverged cells, the unconverged cells having equation sets that have not satisfied a convergence criterion;
(f) calculating a stability limit for each of the converged cells, the converged cells having equation sets that have satisfied the convergence criterion;
(g) when the number of unconverged cells is greater than a predetermined amount, constructing a reduced nonlinear system with the list of unconverged cells, the reduced nonlinear system being assigned to be solved with the implicit formulation and other cells being assigned to be solved with the explicit formulation;
(h) repeating parts (d), (e), (f) and (g), substituting the solved solution for the initial guess or the most recent solved solution and substituting the equation sets corresponding to the cells in the list of unconverged cells for the system of equations or equation sets from the most recent iteration, until all equation sets satisfy the convergence criterion and a stability criterion; and
(i) when all equation sets satisfy the convergence criterion and the stability criterion, outputting the solved solution as a result for a timestep of a simulation of the subsurface reservoir.
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Abstract
A method for performing a simulation of a subsurface hydrocarbon reservoir is disclosed. Each cell in a reservoir model has an equation set representing a reservoir property. A stability limit is determined for each cell. Each cell is assigned to an explicit or implicit formulation. A solution to the system of equations is solved for using an initial guess and an explicit or implicit formulation. A stability limit is calculated for the converged cells. When the number of unconverged cells is greater than a predetermined amount, a reduced nonlinear system is constructed with a list of unconverged cells. The reduced nonlinear system is solved with the implicit formulation, and other cells are solved with the explicit formulation. Parts of the method are repeated until all equation sets satisfy a convergence criterion and a stability criterion, and the solved solution is output.
310 Citations
24 Claims
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1. A method of performing a simulation of a subsurface hydrocarbon reservoir, the reservoir being approximated by a reservoir model having a plurality of cells, each cell having associated therewith an equation set representing a reservoir property, the method comprising:
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(a) determining a stability limit for each of the plurality of cells; (b) assigning each cell to one of an explicit formulation or an implicit formulation; (c) providing an initial guess to a solution for a system of equations formed using the equation set for each cell in the plurality of cells; (d) using the initial guess to solve for a solution to the system of equations using an explicit formulation for cells assigned thereto and an implicit formulation for cells assigned thereto; (e) establishing a list of unconverged cells, the unconverged cells having equation sets that have not satisfied a convergence criterion; (f) calculating a stability limit for each of the converged cells, the converged cells having equation sets that have satisfied the convergence criterion; (g) when the number of unconverged cells is greater than a predetermined amount, constructing a reduced nonlinear system with the list of unconverged cells, the reduced nonlinear system being assigned to be solved with the implicit formulation and other cells being assigned to be solved with the explicit formulation; (h) repeating parts (d), (e), (f) and (g), substituting the solved solution for the initial guess or the most recent solved solution and substituting the equation sets corresponding to the cells in the list of unconverged cells for the system of equations or equation sets from the most recent iteration, until all equation sets satisfy the convergence criterion and a stability criterion; and (i) when all equation sets satisfy the convergence criterion and the stability criterion, outputting the solved solution as a result for a timestep of a simulation of the subsurface reservoir. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of performing a simulation of a subsurface hydrocarbon reservoir, the reservoir being approximated by a reservoir model having a plurality of cells, each cell having associated therewith an equation set representing a reservoir property including at least one of fluid pressure, saturation, and fluid flow, the method comprising:
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(a) determining a stability limit for each of the plurality of cells; (b) assigning each cell to one of an explicit formulation or an implicit formulation; (c) providing an initial guess to a solution for a system of equations formed using the equation set for each cell in the plurality of cells; (d) using the initial guess to solve for a solution to the system of equations using an explicit formulation for cells assigned thereto and an implicit formulation for cells assigned thereto; (e) establishing a list of unconverged cells, the unconverged cells having equation sets that have not satisfied a convergence criterion; (f) calculating a stability limit for each of the converged cells, the converged cells having equation sets that have satisfied the convergence criterion; (g) when the number of unconverged cells is greater than a predetermined amount, adding, to the list of unconverged cells, converged cells with one or more reservoir properties exhibiting changes greater than a preset amount, converged cells that do not satisfy the stability criterion, and any cell that is neighbor to a cell in the list of unconverged cells and that does not satisfy the stability criterion, and constructing a reduced nonlinear system with the list of unconverged cells, the reduced nonlinear system being assigned to be solved with the implicit formulation and other cells being assigned to be solved with the explicit formulation; (h) repeating parts (d), (e), (f) and (g), substituting the solved solution for the initial guess or the most recent solved solution and substituting the equation sets corresponding to the cells in the list of unconverged cells for the system of equations or equation sets from the most recent iteration, until all equation sets satisfy the convergence criterion and a stability criterion; and (i) when all equation sets satisfy the convergence criterion and the stability criterion, outputting the solved solution as a result for a timestep of a simulation of the subsurface reservoir. - View Dependent Claims (17, 18)
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19. A computer program product comprising a non-transitory computer readable storage medium and computer executable logic recorded on said non-transitory computer readable storage medium, the computer program product further comprising:
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(a) code for determining a stability limit for each of a plurality of cells in a reservoir model that approximates a subsurface hydrocarbon reservoir, each cell having associated therewith an equation set representing a reservoir property; (b) code for assigning each cell to one of an explicit formulation or an implicit formulation; (c) code for providing an initial guess to a solution for a system of equations formed using the equation set for each cell in the plurality of cells; (d) code for using the initial guess to solve for a solution to the system of equations using an explicit formulation for cells assigned thereto and an implicit formulation for cells assigned thereto; (e) code for establishing a list of unconverged cells, the unconverged cells having equation sets that have not satisfied a convergence criterion; (f) code for calculating a stability limit for each of the converged cells, the converged cells having equation sets that have satisfied the convergence criterion; (g) code for constructing a reduced nonlinear system with the list of unconverged cells when the number of unconverged cells is greater than a predetermined amount, the reduced nonlinear system being assigned to be solved with the implicit formulation and other cells being assigned to be solved with the explicit formulation; (h) code for repeating parts (d), (e), (f) and (g), substituting the solved solution for the initial guess or the most recent solved solution and substituting the equation sets corresponding to the cells in the list of unconverged cells for the system of equations or equation sets from the most recent iteration, until all equation sets satisfy the convergence criterion and a stability criterion; and (i) code for outputting the solved solution as a result for a timestep of a simulation of the subsurface reservoir when all equation sets satisfy the convergence criterion and the stability criterion. - View Dependent Claims (20, 21)
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22. A method of managing hydrocarbon resources, comprising:
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(a) approximating a subsurface hydrocarbon reservoir with a reservoir model having a plurality of cells, each cell having associated therewith an equation set representing a reservoir property; (b) determining a stability limit for each of the plurality of cells; (c) assigning each cell to one of an explicit formulation or an implicit formulation; (d) providing an initial guess to a solution for a system of equations formed using the equation set for each cell in the plurality of cells; (e) using the initial guess to solve for a solution to the system of equations using an explicit formulation for cells assigned thereto and an implicit formulation for cells assigned thereto; (f) establishing a list of unconverged cells, the unconverged cells having equation sets that have not satisfied a convergence criterion; (g) calculating a stability limit for each of the converged cells, the converged cells having equation sets that have satisfied the convergence criterion; (h) when the number of unconverged cells is greater than a predetermined amount, constructing a reduced nonlinear system with the list of unconverged cells, the reduced nonlinear system being assigned to be solved with the implicit formulation and other cells being assigned to be solved with the explicit formulation; (i) repeating parts (e), (f), (g) and (h), substituting the solved solution for the initial guess or the most recent solved solution and substituting the equation sets corresponding to the cells in the list of unconverged cells for the system of equations or equation sets from the most recent iteration, until all equation sets satisfy the convergence criterion and a stability criterion; (j) when all equation sets satisfy the convergence criterion and the stability criterion, outputting the solved solution as a result of a timestep of a simulation of the subsurface reservoir; and (k) managing hydrocarbon resources using the simulation of the subsurface reservoir. - View Dependent Claims (23, 24)
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Specification