Poromechanics Modeling Forecasts Production, Analyzes Productivity Decline

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 212200, “Accurate Production Forecasting and Productivity Decline Analysis Using Coupled Full-Field and Near-Wellbore Poromechanics Modeling,” by Yan Li, Bin Wang, and Jiehao Wang, Chevron, et al. The paper has not been peer reviewed. _ Productivity index (PI) decline is caused by different mechanisms in both the wellbore region and the far field. Damage in the wellbore region can be simulated by detailed wellbore modeling. A newly developed full-field and near-wellbore poromechanics coupling scheme is used in the complete paper to model PI degradation against time. Near-wellbore damage and field and well interactions are identified when applying the coupling scheme for a deepwater well. History matching, production forecasting, and safe drawdown limits are derived for operational decisions. Full-Field Reservoir Model and Near-Wellbore Poromechanics Model Coupling Full-field and near-wellbore modeling involves coupling the simulation of a full-field reservoir model with one or more near-wellbore poromechanics models. In the coupled simulation, the full-field reservoir model dictates the changing flow or thermal boundary conditions for the embedded near-wellbore models. Meanwhile, near-wellbore phenomena affect well productivity in the full-field reservoir model, altering the flow and thermal boundary conditions on all near-wellbore models in the same field. While capturing the dynamic interactions between the full-field model and all embedded near-wellbore models is of vital importance, the traditional near-wellbore modeling work flow considers only one-way coupling. This work flow is labor-intensive and lacks the dynamic interplay between the reservoir and near-wellbore models. A novel near-wellbore coupling framework is developed to automate data exchange and capture dynamic interactions between the full-field model and the near-wellbore model. In the full-field reservoir and geomechanics coupling applications, only a reservoir simulator solves reservoir flow and thermal equations and a geomechanics simulator solves solid mechanics equations. The reservoir and geomechanics simulators exchange 3D field data. Because solid mechanics equations are quasistatic, the geomechanics simulator does not take timesteps in full-field coupling. In near-wellbore coupling, however, both reservoir and geomechanics simulators solve reservoir flow and thermal equations. The near-wellbore geomechanics model also may solve solid mechanics or other equations coupled to flow or thermal equations in the near-wellbore model. All physics are included in the near-wellbore model for the coupling. Both field properties (3D) and transient boundary conditions (2D) must be mapped onto the near-wellbore model. It is important to ensure that the full-field and near-wellbore models are consistent. A 3D data-mapping module is developed to map flow and rock properties and initial conditions from the full-field model to the near-wellbore model. During the simulation, the transient pressure/temperature boundary conditions (2D) at the external boundary of the near-wellbore model must be mapped from the full-field model to the near-wellbore model to update transient boundary conditions. The automated data mapping in the coupling scheme eliminates the need for manual mapping of field properties and transient boundary conditions.