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Geological processes modeling (GPM) research Institute

FBCM

Fracture-Based Continuum Modeling (FBCM) describes a technology for modeling fractures explicitly in continuum analysis.

The domain element in FBCM consists of a continuum element with zero to six fracture segments that intersect at the element centroid. This picture shows a continuum element with six fracture segments. The fractures and stresses shown are symbolic only, to illustrate model relationships. For example, the stress conditions of an FBCM element may be tensile or compressive and need not be principal stresses.
  • The model domain is discretized into continuum elements (sub-volumes of the domain), referred to as domain elements.
  • Preexisting fractures are discretized into planar segments based on intersections with the domain elements.
  • New fractures are generated in planar segments based on mechanical conditions in the domain elements.
  • Each domain element can host up to six fracture segments
  • Four pre-existing fractures
  • Two new fractures
  • Each fracture segment intersects the element centroid;
  • Terminates on four element faces;
  • Has constant dip, dip direction, and aperture;
  • and the aperture may vary with time through an analysis.
  • The fracture dip, dip direction, and aperture may vary among domain elements, i.e., among fracture segments.
  • Each fracture segment is represented mathematically as a local transformation matrix that conveys the fracture behavior to the host element.
  • The host element, in turn, conveys the fracture behavior to neighboring elements through hydro-mechanical interactions.
  • In hydrologic analysis, the fracture transformation matrix is used to calculate fracture-to-element-face connection matrices to define hydrological interactions.
  • In mechanical analysis, the element mechanical conditions determine fracture initiation and deformation;
  • A new fracture initiates as shear or tensile;
  • Every fracture may deform in slip mode or opening mode.
  • Fracture aperture is initiated with the fracture and updated incrementally thereafter.
  • There is no model prescription for fracture tip phenomena, propagation, or coalescence.
  • Hydro-mechanical interactions among elements control fracture propagation and coalescence.
  • The hydro-mechanical relationships are enforced through piecewise tensorial aggregation over fractures and unfractured matter.
  • FBCM provides several business advantages because of features that can be summarized as follows.
  • FBCM models fracture initiation and propagation without re-meshing.
  • FBCM stores fracture geometry and aperture as continuum properties and uses the information internally to calculate parameters needed to model individual fractures explicitly.
  • Each FBCM model can incorporate large populations of preexisting fractures.
  • Incorporates three-dimensional fracture distributions seamlessly by using a continuum framework to store fracture geometry and aperture.
  • Calculates the location, dip, and dip direction of new (induced) fractures.
  • Calculates fracture aperture for new and preexisting fractures.
  • Models several realizations of the preexisting fracture distribution using the same domain grid, to support probabilistic analysis.
  • Models at real scale such that simulation results can be used directly in the target application.
  • The computer code CanFrac implements FBCM for mechanical analysis.
  • Computer code CanFracEnv implements FBCM for hydrological analysis.