Stress prediction using 1D and 3D geomechanical models of a tight gas reservoir—A case study from the Lower Magdalena Valley Basin, Colombia

Abstract

The characterization of the mechanical properties and stress state of a hydrocarbon or geothermal reservoir and its overburden is crucial for its optimal exploration and exploitation. We present a geomechanical modeling study from the Lower Magdalena Valley Basin in northern Colombia that integrates various borehole and seismic data-sets to build a 3D model for a robust prediction of the mechanical property distribution and the pre-production stress state. The workflow includes the analysis of log and core data as well as hydraulic tests leading to detailed 1D mechanical earth models (MEM) for each of the five wells currently available in the study area. Subsequently, this information is upscaled to and integrated with a structural model derived from 3D seismic interpretation. For this 3D MEM we test two different property population methods and compare the resulting stress prediction. The first method uses a geostatistical approach based exclusively on well data for property interpolation, whereas the second method additionally utilizes seismic inversion techniques to account for the vertical and horizontal differences in mechanical rock properties. The results include a mechanical characterization of the subsurface as well as the complete stress tensor for the reservoir and encompassing formations in the model domain. The simulation results show that the dominant stress regime in the study area is a normal faulting regime with a governing orientation of SHmax in the WNW–ESE direction. At reservoir depth, the vertical stress gradient (Sv) has a mean value of 23.29 MPa/km, SHmax is on average 1.08×Shmin and 0.8×Sv. Comparison of the two property population methods shows substantial enhancements by using the seismic-driven approach to distribute log-derived elastic properties. This worked geomechanical modeling example from Colombia illustrates the potential of 1D and 3D MEM’s for mechanical and stress characterization and can be used as template for similar studies elsewhere.