A Consistent Method to Build and Use a 3D Mechanical Earth Model

The document presents a consistent method to build 3D Mechanical Earth Models (3D MEM). It is based on a rock physics study to derive field specific correlations between mechanical properties and interpreted petrophysical quantities. The 3D MEMs built using this methodology yield robustness and consistency when matching to the measured minimum stress. They also display good predictive capabilities making them valuable for operational design. This method consists of conducting a preliminary rock physics study in order to obtain correlations between the mechanical properties (elastic moduli and strength), of the various formations that are considered, and basic interpreted quantities which are readily available in most 3D geological models (porosity or mineralogy). The correlations are used to build a 3D MEM which is consistent with both the 3D geological model and the 1D geomechanical interpretation. It is also possible to extend the correlations by linking raw log data to rock mechanical properties. The model was tested against field case study to verify its predictiveness. Minimum stresses calculated by the 3D MEM matched well to the measured values obtained from mini-frac tests performed at various locations. Ultimately it permits to better forecast the material properties (in 3D) as well as the effective stress tensor (in 4D). The 3D MEMs were used to evaluate the risks for infill drilling, and for completion purposes. Performing this type of preliminary rock physics study has a number of benefits. Firstly, to help identify which logging suite should be run to characterize the geomechanical properties of a given formation, and secondly it can be used to derive correlations between raw log data and geomechanical properties. These correlations can be applied during operations for real time decision making purposes when there is not yet a petrophysical interpretation available. The novelty of the method introduced lies in the systematic and coherent integration of data to build a consistent geomechanical model (3D or 1D), that exhibits a robust predictive capability and shows the value of 3D MEM for the design of drilling and completion operations.