Skip Navigation

lab

Skip Side Navigation

Reservoir Geomechanics and Seismicity Research Group

Overview:

    The Reservoir Geomechanics and Seismicity Research (RGSR) Group at The University of Oklahoma is the largest reservoir geomechanics research group in North America. The director of RGSR is Prof. Ahmad Ghassemi, a widely recognized geomechanics specialist with extensive teaching and research experiences of more than 20 years. Currently, there are 12 PhD students, 7 Master students, 3 undergraduate students, 3 Postdoctoral Researchers and 1 Lab Technologist in the group. The RGSR develops and applies new knowledge of geomechanics and rock mechanics through experimental and modeling activities to develop solutions for a variety of engineering problems related to conventional and unconventional reservoirs and geothermal systems, such as hydraulic fracturing, induced seismicity, wellbore stability, DFIT, injection geomechanics, EGS development, etc.  The students within the RGSR have a unique opportunity to carry out cutting-edge research and to pursue their professional development.

Experimental Research and Testing:

    The RGSR group has a world-class rock mechanics facility consisting of a number of MTS Material Testing Systems, 3 Polyaxial Testing units, 1 TTK Triaxial Test System, 1 Creep Test System, 1 API Fracturing Conductivity Test System, 3D laser Scanning System and some Rock Preparation Tools (Diamond Cutting and Coring systems), etc. In addition to conventional rock mechanics testing such as  uniaxial/triaxial compressive, static/dynamic, tensile strength, AE monitoring, hardness, fracture conductivity, etc., we perform advanced/novel rock mechanics tests such as large-scale hydraulic fracturing test under true triaxial condition, tracer test, high temperature and high pressure test, triaxial shear test, direct shear test, fracture propagation and coalescence test.  

Numerical Modeling:

    Our modeling infrastructure “GeoFrac” consists of thermo-poro-mechanical hydraulic fracturing and fracture network models that have been developed for large-scale fracture studies, considering natural fractures, thermo-poroelastic processes, and thermal fracture propagation. “GeoFrac” has 2D and 3D modules. The 2D version considers rock anisotropy and the fractures can be oriented at any angle with respect to the directions of elastic symmetry. A 3D height correction factor has been derived for anisotropic rock and is implemented in the program. For 3D modeling both FEM and BEM are available, the latter considers rock heterogeneity and non-linearity and allows for proroelasticity, thermoelasticity, and mixed-mode propagation, and natural fractures. The BEM modules explicitly consider hydraulic fracture/natural fracture interactions. The solution algorithm and propagation condition are advanced. The system of non-linear equations of fluid flow and fracture deformation are solved rapidly for large-scale problem in a fully-coupled manner. The quasi-static propagation of fractures is accurately captured using LEFM. Fluid partition into each fracture is implemented using a wellbore fully coupled with the fracture elements. When modeling multiple stages, different conditions for previous stage fractures, and tip asymptotes can be considered. In the multi-stage fracturing simulations, previous fractures can be kept either pressurized or propped while simulating the next stage fractures. The model has the capability to distinguish between viscosity and toughness dominated propagation regimes, and takes into account their corresponding tip solutions.

  • Anisotropic HF model in fractured rock (fracture network/HF in anisotropic formations)
  • 3D Anisotropic HF modeling
  • 3D Poroelastic multiple HF modeling
  • 3D fracture network modeling of stimulation and induced seismicity
  • Inversion of seismic data to characterize NF properties
  • State-of-the-art 3D poroelastic analysis of Re-frac and Parent-Child well systems
  • 3D thermo-poroelastic FEM for wellbore stability and fracture modeling in heterogeneous rocks
Simultaneous fracturing in the presence of natural fractures. Left: high differential stress case, sigma H= 60 MPa, sigma h = 40 MPa; Right: low differential stress case, sigma H= 60 MPa, sigma h = 59 MPa.
Fracture network obtained from zipper fracturing simulations in isotropic and anisotropic rocks. Stimulation of Well-2 is carried out after Well-1. Growth of inner fractures is highest in isotropic rock. Whereas in anisotropic rock, larger special extent of stress shadow inhibited growth of inner fractures especially when Psi=00. In the case of anisotropic rock with non-uniform fracture toughness, inner fracture growth is relatively enhanced, and fractures appear to deviate slightly towards the plane of least fracture toughness (x’-axis).
Zipper fracturing of deviated wells not aligned with minimum horizontal stress direction (i.e., x-axis), and deviated from the x-axis by 20º. Spacing between stages = 35 m, well spacing = 80 m. Simulation time = 42.9 min, propagation time = 225 s.