Borehole simulator G.E.O.S.I.M.: Software for the simulation of downhole and reservoir processes in deep geothermal projects

For the coupled simulation of flow and heat transport processes in the borehole and in the reservoir, G.E.O.S. developed the borehole simulator G.E.O.S.I.M.  This software can be used both in the planning phase and in the test phase of deep geothermal projects.

G.E.O.S.I.M.s was developed in 2010 for the test evaluation in the deep geothermal project Traunreut and later refined within the framework of the research project GEOFÜND. Since the completion of the GEOFÜND project, G.E.O.S.I.M. has been continuously developed to this day.

The main applications of the software are:

• Recalculation of hydraulic tests to identify parameters (production and injection tests as well as circulation tests for up to 6 boreholes)
• Optimisation of casing by simulating pressure losses as a function of casing schemes
• Well tests with consistent separation of geological (reservoir transmissivity and porosity) and technical factors (casing, production and injection pumps)
• Consistent calculation of thermal and electrical power for well tests

The following parameters and processes are considered in a coupled way:

• Geometry of the borehole
  
  • Complete casing scheme (pipe diameter, drilling diameter) including riser and injection string and consideration of material properties and geometries
  • Correlation MD-TVD
• Density and viscosity of the thermal water in the well as a function of pressure, temperature and mineralisation ( (NIST, 2014))
• Non-stationary calculation of the water levels
• Non-stationary heat transport via radially symmetric modeling of heat conduction
  
  • Temperature profile (possible in TVD or MD)
  • Depth-dependent rock parameters (heat capacity, thermal conductivity and density)
  • Material properties of casing and cementation
  • Non-stationary heat transport via convective transport in the borehole
  • Consideration of the different flow velocities
  • Heat capacity of the thermal water in the borehole
• Pipe friction losses
  
  • Dependence on flow rate, pressure and temperature
  • Consideration of pipe roughness
  • Optional consideration of pressure losses in the open-hole area, when inflow zones are known
  • Data transfer from the application Pressure Loss 7.2 or alternatively via implemented empirical approaches
• Non-stationary pressure changes in the reservoir as a function of non-stationary production and injection rates
  
  • By importing the pressure changes from the reservoir model: For this purpose, the pressure change is simulated non-stationarily with the reservoir model beforehand and the pressure changes are imported into G.E.O.S.I.M.
  • Alternatively: Calculation via integrated non-stationary well model: Any non-stationary production and injection rates can be taken into account. The non-stationary well model is based on the superposition of well functions using a convolution integral approach.
• Non-stationary coupling between production and injection wells
  
  • Accounting for the heat release in a heat centre
• Heat input by the pumps
  
  • Heat input of an submersible centrifugal pump as a function of the current output and its efficiency
  • Heat input of the injection pump as a function of the current output and its efficiency
• Empirical consideration of heat transfer in tubing-casing annulus around production or injection line  
• Effective heat conduction (partly multiphase heat transfer, partly free convection)
• Consideration of surface structure on heat transfer from the thermal water to the borehole wall
• Variable measuring depths of the water level sensors or memory tools
• Export of the time-dependent temperature into the reservoir - Integration of the temperature change over the course of the injection well