Project: Delta Pressure and Caprock Integrity Study

Geofirma was contracted to prepare an engineering and modelling study to assess the feasibility of increasing the pressure (delta pressuring) of several underground natural gas storage reservoirs.  Work involved in this assessment included the advancement of one deep borehole above the gas reservoir in order to better characterize geomechanical and petrophysical properties of the rock (strength, porosity, permeability, retention curve) as well as to permit in-situ hydraulic testing of cap rock and installation of a depth discrete multi-level piezometer to record the evolution of pressure above the caprock during fluctuations of reservoir pressure due to injection or withdrawal activities based on market demand for the natural gas.

To assess the potential for pressure and gas propagation in the cap rock a two-phase flow model was developed and calibrated with data collected on-site.  The mechanical response of the caprock to delta pressuring was completed using FLAC3D to assess the distribution of induced stresses surrounding the reservoir.  Outputs from the two-phase flow model were used as inputs to the geomechanical model, allowing direct assessment of the mechanical effects of delta pressuring.

For additional information contact Robert Walsh, P.Eng.