FIELD OF THE INVENTION

The invention relates to the field of geological simulation, and more particularly to a computer-implemented method, a computer program and a computer system for designing a geological simulation grid, for example a grid configured for reservoir simulation such as flow simulation.

BACKGROUND

Geological simulation refers to all techniques for performing computer simulations related to a geological environment. These techniques assist actors by providing them with computerized representations of real, estimated or predicted states and/or processes related to the geological environment. For example, in the context of hydrocarbon production (e.g. oil and/or gas production), flow simulation may provide useful information as to how hydrocarbons flow in a reservoir environment. Flow simulation may for example represent real, estimated or predicted flow paths, flow rates, flowing compositions, and/or evolutions of these quantities over time.

In many existing solutions, geological simulation is performed with finite element processing based on geological simulation grids. Geological simulation grids comprise a geometrical grid which conforms to shapes of geological structures, such as horizons, fault surfaces, channels and/or reservoirs. For example, horizons correspond to layer structures of the geometrical grid and fault surfaces correspond to stair-stepped structures of the geometrical grid. Geological simulation grids further comprise parameters which represent geological properties of the geological structures, such as flow parameters, and which are assigned to geometrical structures of the geometrical grid. A geological simulation grid may be inputted to a finite element simulator which performs geological simulations, such as flow simulation, according to the values of the geological properties conveyed by the parameters and to the shapes of the geometrical grid.

Because of the size of the geological environments and the numbers of geological structures at stake, designing a geological simulation grid is a tedious task. Designing a geometrical grid in particular is time-consuming. Geometrical grids may indeed comprise more than ten million of cells in some situations. For this reason notably, the result is most often inaccurate, in the sense that simulations performed on the basis of a designed geological simulation grid are most often inaccurate.

Document US 2016/0103246 A1 for example recognizes that there may be a spatial discrepancy between a stair-stepped grid structure and a surface representing a discontinuity in a geological environment, such as a fault surface. The document proposes mapping the stair-stepped grid structure and the surface. This way, properties associated with the stair-stepped grid structure may be adjusted based on the mapping to compensate for the spatial discrepancy.

However, although such improvements are provided, there is still a need for solutions to design in a relatively simple way geological simulation grids which are relatively accurate.

SUMMARY OF THE INVENTION

It is therefore provided a computer-implemented method for designing a geological simulation grid. The method comprises providing a geometrical grid that conforms to a set of geological structures of a geological environment. The method also comprises providing a geometrical surface that represents a geological surface of the geological environment. The geological surface is outside the set of geological structures. The method also comprises identifying geometrical structures of the geometrical grid that each correspond to a respective location of the geometrical surface. The method also comprises transferring to each identified geometrical structure one or more respective parameters. Each parameter is a value of a respective property of the geological surface.

Such a method improves the field of designing geological simulation grids, by allowing to design in a relatively simple way a geological simulation grid which is relatively accurate.

Notably, the method allows configuring a geological simulation grid with respect to a geological surface. For that, the method comprises identifying geometrical structures of the geometrical grid that correspond to the geological surface and accordingly transferring to the geometrical grid parameters that represent properties of the geological surface. Examples that allow addressing particularly efficiently the algorithmic complexity of the task of identifying the relevant geometrical structures are provided later.

As opposed to the solution disclosed by document US 2016/0103246 A1, the method provided herein does not necessitate that an existing structure of the geometrical grid conform to the geological surface. The method provided herein indeed processes a geological surface which is outside the set of geological structures. The method thus allows late-addition of information related to a geological surface to a geological simulation grid having an already-designed geometrical grid.

Such addition of information is performed in a relatively simple way, that is, by identifying relevant geometrical structures and transferring parameter data directly to such identified structures (instead for example of re-designing the geometrical grid to make sure that a structure of the geometrical grid conforms to the geological surface as well). The method thus offers a computationally cheap alternative to re-designing the geological simulation grid from scratch.

Furthermore, the method may perform whichever the geometry of the geological surface. The method may perform notably even if the geometrical structures of the geometrical grid corresponding to the geometrical surface do not form a stair-stepped grid structure. The method can thus be applied for any type of geological surface. Similarly, the method may perform whichever the geometry of the geometrical grid. The method may perform notably even if the geometrical grid is irregular or yet unstructured.

The method may comprise one or more of the following:the geometrical surface is provided based on data obtained after a determination of the geometrical grid;the geometrical grid is provided with an initial set of parameters each assigned to a respective geometrical structure of the geometrical grid, the identifying and the transferring being performed based on a result of a geological simulation performed with the geometrical grid and the initial set of parameters;the method includes comparing the result of the geological simulation performed with the geometrical grid and the initial set of parameters with corresponding real data;for at least one identified geometrical structure that corresponds to a respective location of the geological surface, at least one parameter of the transferred one or more respective parameters depends on a size of said respective location;at least one property of the geological surface varies locally, each of the transferred one or more respective parameters that are a value of the at least one property being a local value;the geometrical surface is composed of discrete elements, the identifying including determining cells of the geometrical grid that each intersect a respective discrete element;the identifying further includes determining pairs of cells each including a respective first cell that intersects a respective discrete element and has a center located on one side of the geometrical surface and a respective second cell that is a neighbor of the respective first cell and has a center located on the other side of the geometrical surface;at least one of the identified geometrical structures is an interface between a determined pair of cells;the determining of cells of the geometrical grid that each intersect a respective discrete element is iterated over the discrete elements via one or more neighborhood propagations over the discrete elements of the geometrical surface;at each non-starting iteration of each neighborhood propagation over the discrete elements of the geometrical surface, the determining (S310) of cells of the geometrical grid that each intersect a respective discrete element includes using cells determined at the previous iteration;at each non-starting iteration of each neighborhood propagation over the discrete elements of the geometrical surface, the determining of cells of the geometrical grid that each intersect a respective discrete element is performed via a neighborhood propagation on the cells of the grid; and/orat each determining of a cell of the geometrical grid that intersects a respective discrete element, the method comprises transferring to the determined cell one or more respective parameters.

In examples, the method may comprise, with the same provided geometrical grid, providing a plurality of geometrical surfaces. The plurality of geometrical surfaces may represent, as a whole, one or more geological surfaces. The method may then perform for each geometrical surface the identifying of geometrical structures of the geometrical grid that each correspond to a respective location of the geometrical surface, and then transferring to each identified geometrical structure of one or more respective parameters.

In examples, the identifying and the transferring may be performed after initially constructing a space search structure. The construction may be performed only once, such that the same initial space search structures may be used for all the geometrical surfaces.

In examples, the plurality of geometrical surfaces may comprise more than 1000 or 500 or 50.

It is further provided a simulation process which comprises performing a geological simulation based on the designed geological simulation grid, for example according to any finite element simulation technique. The simulation process may comprise performing the method for designing the geological simulation grid before performing the geological simulation, for example with the same system as the one that performs the geological simulation, or alternatively providing the already-designed geological simulation grid, for example by receiving the already-designed geological simulation grid from a distant system. The simulation process may be a hydrocarbon flow simulation process.

It is further provided a computer program comprising instructions for performing the method and/or the simulation process.

It is further provided a data structure representing a geological simulation grid obtainable by the method.

It is further provided a data storage medium having recorded thereon the computer program and/or the data structure.

It is further provided a system comprising a processor coupled to a memory, the memory having recorded thereon the computer program and/or the data structure. The system may further comprise a display configured for displaying outputs of the computer program and/or a graphical user interface for entering inputs of the computer program.

It is further provided a hydrocarbon production process which comprises performing one or more simulation phases according to the (e.g. flow) simulation process and one or more production phases. The simulation phases and the production phases may be interlaced. In other words, the production process may comprise alternations between simulation phases and production phases. The alternations may comprise overlaps. One or more of the production phases may be based on a result of one or more of the simulation phases, for example a result of the last simulation phase. A production phase may be based on a result of a simulation phase for example by setting a production parameter as a function of said result.

The geological simulation grid used at different simulation phases may be different. Notably, the geological simulation grid used at a simulation phase may be obtained by performing the method for designing a geological simulation grid starting from the geological simulation grid of a previous simulation phase and adding information related to a given geological surface, optionally after having deleted other information. The given geological surface may be outside the set of geological structures to which the geometrical grid of the geological simulation grid of said previous simulation phase was initially designed to conform.

For example, the production process may comprise acquiring information on the geological surface (e.g. by detecting the given geological surface from measurements on the geological environment, for instance seismic data) and/or detecting inconsistency between data measured during a production phase and a result of a preceding simulation phase. In such cases, the production process may comprise performing the method to refine the geological simulation grid with information related to the given geological surface. The production process may then comprise a new simulation phase based on the refined geological simulation grid and/or then a new production phase based on the new simulation phase.

