fallstudie_kandel

Geomechanical case study in the central Upper Rhine Graben

PhD thesis C. Wagner

Seismic interpretation and geomechanical reservoir modeling of a case study from the Upper Rhine Graben.

Faults and lithological changes can affect the tectonic stress regime in the subsurface and cause local variation in stress magnitude and orientation. In order to minimize exploration risks and optimize drilling, a prediction of such stress perturbations is desirable. For a realistic prediction a corresponding geomechanical model based on Finite Element techniques has to incorporate data such as reservoir geometry, regional tectonic stress field and mechanical properties of the different lithologies and faults involved. The modeling results can be used for a wide range of applications, e.g. borehole stability, hydraulic frac planning and permeability anisotropies in stress-sensitive reservoirs.

The study area to apply the above mentioned workflow to the real world is located in the central part of the Upper Rhine Graben, northwest of Karlsruhe/Germany. The geometry of the geomechanical model is based on a 3D seismic survey covering an area of 7.5 x 9.5 km. Following seismic interpretation with respect to faults and lithostratigraphic horizons the structural model is transferred to the geomechanical simulation software and populated with reservoir-specific mechanical properties. In addition to the full 3D stress tensor for each part of the model, the numerical simulation also provides some indications for the slip and dilatation tendencies and the hydraulics of the fault which can be compared to observational data.

Left: View on the incorporated faults of the geomechanical reservoir model. Fault geometry gained from 2D and 3D seismics. For instance, two horizons and one seismic inline (blue rectangle) are also shown. Right: Example of geometry transfer from Petrel (software for seismic interpretation) to ANSYS (Finite-element software) executed for two fault blocks. A point cloud in Petrel is used as data origin to generate the fault blocks (A). The point cloud can be gained from the intersection lines between fault surfaces and horizons. Using the coordinates of each point the transfer can be performed. In ANSYS the intersection curves are recreated with spline functions (B). Based on the shapes of boundary curves a new surface is created by the coons patch method. (C).The created surfaces are used as basis to generate the volumes by joining them vertically (D). Thus, for this example, each fault block consists of four volumes. (Fig. Ch. Wagner)
Left: View on the incorporated faults of the geomechanical reservoir model. Fault geometry gained from 2D and 3D seismics. For instance, two horizons and one seismic inline (blue rectangle) are also shown. Right: Example of geometry transfer from Petrel (software for seismic interpretation) to ANSYS (Finite-element software) executed for two fault blocks. A point cloud in Petrel is used as data origin to generate the fault blocks (A). The point cloud can be gained from the intersection lines between fault surfaces and horizons. Using the coordinates of each point the transfer can be performed. In ANSYS the intersection curves are recreated with spline functions (B). Based on the shapes of boundary curves a new surface is created by the coons patch method. (C).The created surfaces are used as basis to generate the volumes by joining them vertically (D). Thus, for this example, each fault block consists of four volumes. (Fig. Ch. Wagner)

This project is partly funded by GDF SUEZ E&P Deutschland GmbH.

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