Development of a Geomechanical Reservoir Modelling Workflow and Simulations

Abstract

A Geomechanical Earth Model (GMEM) is wanted for every field development and should be maintained for the life-time of the field. These models are needed in order to contribute to safe and optimum drilling and production in depleting and complex reservoirs. This strategy is only possible if an automated workflow is developed. Links between the stress simulator Abaqus and the geological software Irap RMS and between Abaqus and the reservoir simulator ECLIPSE are established in order to have; (1) faster and better generation of geomechanical reservoir simulation models, (2) to better account for geomechanical effects in the reservoir simulation and 4D feasibility studies. Abaqus scripting interface is used to link Irap RMS and Abaqus. The link consists of a set of Python scripts that rebuilds the reservoir geometry in the CAD, meshing and visualization program Abaqus/CAE. This is believed to be a unique feature of the developed workflow as opposed to earlier developments that reuse the reservoir grid. In addition, a link between Abaqus and ECLIPSE is developed transferring reservoir pore pressure data, initial porosity and degree of water saturation between ECLIPSE and Abaqus through the file system. Verification and demonstration of capabilities of the developed workflow is done using a faulted North Sea oil and gas field. Introduction Both commercial and research simulators that take the fully coupled nature of three-phase-flow and deformation into account exists today. Stone et al 2000 have extended ECLISPE-300Ô(trademark of Schlumberger) to include geomechanics in a finite difference context, while for instance Li and Zienkiewics 1992 have developed a similar approach using the finite element method. It is then natural to ask if this will make the partly coupled approach described here superfluous. Our experience is however that a partly coupled approach between a conventional reservoir simulator and a stress simulator is the best approach for the near future when advanced geomechanical issues must be taken into account. This is also the industry trend as for instance Schlumberger now is marketing the partly coupled approach between ECLIPSE and the finite element stress simulator VISAGEÔ(trademark of Schlumberger). The partly coupled approach benefits from the latest developments in physics and numerical techniques of both simulators. Computer programs from three vendors are involved in the geomechanical reservoir modelling workflow illustrated in Figure 1:Irap RMSÔ (trademark of Roxar Technologies) for geological modelling,ECLIPSEÔ(trademark of Schlumberger) for reservoir modelling andAbaqusÔ (trademark of Dassault Systèmes) for geomechanical reservoir modeling/stress analysis. A standard procedure is to build the faulted reservoir geometry with the geological tool Irap RMS. After gridding and upscaling a simulation ready model is exported to the reservoir simulator ECLIPSE. A similar coupling between the stress-simulator Abaqus and Irap RMS did not exist starting this project. Parts and assemblies can be imported into Abaqus/CAE (Computer Aided Engineering) from a third-party CAD (Computer Aided Design) system. However Irap RMS does not support the CAD industry standards implying that the reservoir geometry must be generated from scratch within Abaqus/CAE using the geometry creation tools: Solid features, cut features, shell features, wire features, datum geometry and partition tools.

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