System and method for automatic local grid refinement in reservoir simulation systems

A computer-implemented reservoir simulation system, the system comprising:

• a processor;
• a non-transitory, computer-readable storage medium accessible by the processor;
• and
• software instructions stored on the storage medium and executable by the processor for:
• applying a coarse grid to a reservoir, the coarse grid having a plurality of coarse grid blocks;
• identifying a fracture of interest disposed in the reservoir;
• determining an average permeability and an average porosity for a local region adjacent the fracture;
• determining a fine grid zone around the fracture based upon a time period for flow simulation of the reservoir and the average permeability and the average porosity of the local region adjacent the fracture, the determining including:
• calculating a distance Xval away from the fracture at which the fine grid zone terminates based upon the time period for simulation and the average permeability and the average porosity of the local region adjacent the fracture;
• and
• defining the fine grid zone by the coarse grid blocks within the distance Xval in a direction away from the structure;
• and
• applying a local grid refinement (“LGR”) to the coarse grid blocks encompassed by the fine grid zone,
• wherein the calculating the distance Xval is in accordance with the equation:
• X
• val
• =
• 10
• a
• *
• time
• *
• k
• por
• ,
• wherein time=the time period for flow simulation, k=average permeability for the local region adjacent the fracture, por=average porosity of the local region adjacent the fracture, and a=an empirical constant determined through calibration simulation of a linear subset of the reservoir.

A computer-implemented reservoir simulation system, the system comprising:

• a processor;
• a non-transitory storage medium accessible by the processor;
• and
• software instructions stored on the storage medium and executable by the processor for:
• applying a coarse grid to a reservoir, the coarse grid having a plurality of coarse grid blocks;
• identifying a fracture of interest disposed in the reservoir;
• determining a fine grid zone around the fracture based upon a time period for simulation of the reservoir, porosity of a region adjacent the fracture and permeability of the region adjacent the fracture;
• and
• applying a fine grid to the coarse grid blocks encompassed by the fine grid zone,
• wherein determining the fine grid zone includes calculating a distance Xval away from the fracture in accordance with the equation:
• X
• val
• =
• 10
• a
• *
• time
• *
• k
• por
• ,
• wherein time=the time period for simulation, k=average permeability for the region adjacent the fracture, por=average porosity of the region adjacent the fracture, and a=an empirical constant determined through calibration simulation of a linear subset of the reservoir.

A method for drilling a wellbore in reservoir, the method comprising:

• applying a coarse grid to a geologic formation of interest, the coarse grid having a plurality of coarse grid blocks;
• identifying a structure of interest disposed in the geologic formation;
• determining a fine grid zone around the structure based upon a time period for flow simulation of the geologic formation and a an average permeability and an average porosity of the geologic formation in a local region adjacent the structure;
• applying a fine grid to the coarse grid blocks encompassed by the fine grid zone to determine flow adjacent the structure;
• based on the determined flow, selecting a position and trajectory for a wellbore in the formation;
• preparing equipment to construct a portion of said wellbore;
• and
• drilling a wellbore in accordance with the selected trajectory,
• wherein determining the fine grid zone includes calculating a distance Xval away from the structure at which the fine grid zone terminates, the calculating based upon the time period for flow simulation and the average permeability and the average porosity of the geologic formation in the local region adjacent the structure, and
• wherein the calculating the distance Xval is in accordance with the equation:
• X
• val
• =
• 10
• a
• *
• time
• *
• k
• por
• ,
• wherein time=the time period for simulation, k=average permeability for the local region adjacent the structure, por=average porosity of the local region adjacent the structure, and a=an empirical constant determined through calibration simulation of a linear subset of the geologic formation.