Systems, methods, and apparatus for transient flow simulation in complex subsurface fracture geometries

A system for simulating a subterranean region having fracture geometries, comprising:

• at least one processor;
• a non-transitory memory linked to the processor, the memory having instructions stored therein, which when executed cause the processor to perform functions including to:
• a) input data from a digital simulator module, the data representing a subterranean region and comprising a matrix grid and fracture parameters representing fractures in the subterranean region;
• b) produce a computational domain separate from the digital simulator module;
• c) input the data from the digital simulator module into the computational domain;
• d) identify, in the computational domain, gridblocks close to fractures in the matrix grid produced by the simulator module;
• e) refine, in the computational domain, the size of gridblocks among the identified matrix gridblocks;
• f) determine, in the computational domain, if the refined gridblocks meet a specified criterion;
• g) repeat, in the computational domain, steps (d)-(f) if the criterion of step (f) is not met;
• h) proceed to step (i) if the criterion of step (f) is met;
• i) calculate, in the computational domain, intersections between the refined gridblocks and the fractures;
• and
• j) input the calculated intersections from the computational domain into the digital simulator module;
• and
• k) generate a simulation of the subterranean region with the digital simulator module using the calculated intersections.

A method for simulating a subterranean region having fracture geometries, comprising:

• obtaining by a processor data produced by a digital simulator module, the data representing a subterranean region and comprising a matrix grid and fracture parameters representing fractures in the subterranean region;
• producing, by the processor, a computational domain separate from the digital simulator module;
• inputting, by the processor, the data produced by the digital simulator module into the computational domain;
• detecting, in the computational domain, geometrical intersections between matrix grid blocks and fractures in the data produced by the simulator module;
• cutting, in the computational domain, the fractures into segments along matrix gridblock boundaries;
• applying, in the computational domain, a pore-volume cutoff for small fracture segments;
• calculating, in the computational domain, connections between segments inside a fracture and between connected segments belonging to intersecting fractures;
• calculating, in the computational domain, intersections between well trajectories associated with the subterranean region and fracture segments;
• computing, in the computational domain, transmissibility factors for non-neighboring connections and well indices associated with the subterranean region;
• creating, in the computational domain, gridblocks in a grid domain and modifying the gridblock properties to represent fracture segments;
• canceling, in the computational domain, connections and adding non-neighboring connections for the created gridblocks;
• adding, in the computational domain, well perforations on the gridblocks;
• inputting, by the processor, the gridblocks from the computational domain into the digital simulator module, and
• generating a simulation of the subterranean region a with the digital simulator module.