top of page

ParaGeo Reservoir Modelling

Coupled modelling of fluid flow and geomechanics, especially within commercial settings, has most commonly been conducted by soft-linking separate commercial geomechanical and fluid flow modelling software. In this case, information from one software package is passed to the other; pore volume and compressibility multipliers are transferred from the geomechanical simulation to the flow simulation; pore pressure, saturation and temperature are exchanged in the opposite direction. External coupling takes advantage of the strengths of the individual conventional flow and geomechanical simulators, i.e.

​

  • Flow simulator: Modelling phase behaviour and multiphase flow

  • Geomechanical simulator: Stress, nonlinear constitutive models and subsurface deformation

​

In many cases, this approach is close to optimal. Still, when investigating strongly coupled behaviour in conjunction with significant displacement, e.g. fault evolution, a fully-coupled single framework approach may be beneficial as:

​

  • A single mesh is used for all fields, reducing mapping dispersion and simplifying model creation.

  • All fields are solved using a moving Lagrangian grid; e.g. spatial and temporal changes in fault transmissibility are represented naturally.

  • The state variables for all fields are concurrently available, enabling tighter coupling and increased accuracy of field-dependent models in all fields.

  • Fluid and thermal flow along/across faults are represented within the same computational framework as fault deformation, which is critical to detailed studies of coupled fault flow and deformation.  

  • Implementation of optimisation/history matching routines for uncertainty analysis can be linked in a single package.

​

ParaGeo has methodologies for both ParaGeo – Reservoir Simulator Coupling (e.g., Intersect-ParaGeo) and ParaGeo-Only fully coupled modelling.

Modelling of injection-production wells in reservoir layer intersected by a fault surface

ParaGeo is a fully coupled Thermo-Hydro-Mechanical modelling framework. The flow field framework is currently being enhanced, specifically targeting applications in C02 sequestration and storage, in particular;

 

  • Improving the understanding of reservoir stress path evolution prior to and during CO2 injection;

  • Assessing the impact of temperature changes on subsurface deformation (faulting and fracturing), injectivity and seismic properties;

  • Predicting fault reactivation considering their single and multiphase flow properties;

  • Assessing whether self-sealing will occur if faults and fractures are accidentally formed in the caprocks

​

ParaGeo has several key benefits for this class of application, e.g.

​

  • A suite of advanced constitutive models for both continuum rock and discrete fault response, i.e. representation of the anisotropic elastoplastic time/temperature/saturation-dependent and the hysteretic response of reservoir and overburden rock mass;

  • Unified treatment of embedded fractures in the flow and geomechanical fields (e.g. Homogenisation);

  • Unified discrete fault modelling framework that enables high resolution, tightly coupled, phenomenological models for across/along fault flow and slip (e.g. Geothermal).

​

The key developments to extend this functionality to C02 applications is the implementation of multiphase flow for continuums and faults, together with a full equation of state for C02. Implementation of the continuum multiphase framework was completed in Q2 2022, and the extension to multiphase discrete fault flow will be finalised in Q4 2022. The framework will then be further enhanced via ongoing R&D collaborations in 2023.

Evolution of phase saturation in a water-flood benchmark using ParaGeo Multiphase Flow Algorithm 

ParaGeo Fully Coupled Reservoir Modelling

ParaGeo - Reservoir Simulator Coupling

ParaGeo has a reservoir modelling framework that may be coupled to an external reservoir simulator. This takes advantage of the advanced description of the geomechanical response of the system provided by ParaGeo, including the evolution of the full 3D stress tensor, while also adopting the advanced flow description provided by the reservoir simulator of your choice. In other words, the coupled model uses ParaGeo geomechanical capabilities to capture the constitutive response of the reservoir, overburden, underburden and side walls using the pore pressure distribution provided by the reservoir simulator.

​

In this workflow ParaGeo performs a geostatic initialisation phase using the stress, pore pressure and material distribution, in conjunction with the reservoir pore pressures. The incremental or iterative coupled procedure then follows: 

  1. The reservoir simulator solves the next flow step.

  2. The pore pressure, temperature and phase saturations are passed to ParaGeo.

  3. ParaGeo solves the geomechanical field and evaluates the update in stress, porosity and compressibility.

  4. ParaGeo updates the reservoir compressibility, permeability and pore volume.

Schematic of the interactions between the coupled fields

Note that generally the mesh discretization in the reservoir simulator and ParaGeo models are different. The geometry in ParaGeo model is updated due to deformation resulting from the evolving material, pore pressure, temperature and stress state. Both codes may also use different reference coordinate systems and units. Thus the ParaGeo-Reservoir communication interface includes:

​

  • Mapping algorithms between the two meshes to interpolate the updated values for the state variables between the two codes

  • Transformation algorithms for conversion between the two coordinate systems

  • Definition of input and output units for appropriate conversion of the state variable values

​

ParaGeo is currently coupled to IX reservoir simulator (Chevron, Schlumberger, Total) but may be coupled to any other reservoir simulation software on request.

Evolution of reservoir pore pressure (left) and vertical stress (right) in a model where ParaGeo is coupled to a third party reservoir simulator. 

bottom of page