3D Geomechanical Modeling and Fault Reactivation Risk Analysis for a Well at Brage Oilfield, Norway

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Abstract The objective is to investigate potential fault reactivation caused by high-volume injection into a North Sea well to assess the risks associated with converting a production well into a water injection well. The well is located within the Brage Field less than 100 meters from a major fault and there is concern for fault reactivation due to high volume water injection near this fault. An integrated 3D geologic, fluid flow and geomechanical model was developed for the area of interest to evaluate fault reactivation risks. The 3D integrated models were constructed based on seismic horizon data and well logs. The 3D fluid flow model was calibrated and history matched using the pressure and temperature data from the current well and other adjacent wells. The developed 3D fluid and heat flow model was used to estimate pressure and temperature distributions adjacent to the fault after water injection in the target well. The results of the 3D fluid flow model were then imported into the 3D geomechanical model to predict the induced stresses and displacements near the injection zone and on the face of the fault. The results of the integrated geologic, fluid flow and geomechanical models indicate that the poro-elastic stresses induced by high volume injection into the proposed well are not sufficient to induce major slip on the nearby main fault, considering a wide range of reasonable physical and material property assumptions for the fault. The results of this study are used in specifying the maximum daily water injection rates in the proposed well without the fault reactivation concerns. With the proposed water injection rate, the sealing capacity of the major fault will be guaranteed and the injected water will be directed into the reservoir for pressurization and water flooding purposes.