3D Geomechanical Modeling for Wellbore Stability Analysis: Starfish, ECMA, Trinidad and Tobago

Abstract

Conventionally, a calibrated 1D geomechanical model is used to define the mud weight window required for the successful drilling and completion of a well. Utilizing depth stretch functionality, estimated rock properties and subsurface stresses, are ‘stretched’ from the corresponding offset well to the proposed well to be drilled. This approach will only suffice if the geological structure and wellbore trajectory are relatively simple. Even so, optimizing wellbore placement becomes an arduous exercise when using 1D geomechanical models because the workflow must be repeated for each new iteration of the proposed wellbore trajectory. Furthermore, as the geological structure and wellbore trajectory increases in complexity, severe distortion in topological properties, such as overburden stress and pore pressure, can render the one-dimensional solution inapplicable. In such circumstances, a calibrated 3D geomechanical model can be used. This paper introduces a generic workflow for developing a calibrated 3D geomechanical model that can be used for wellbore stability analysis. The workflow incorporates calibrated 1D geomechanical models and existing static geological modeling outputs, such as structural surfaces and facies model, to constrain the distribution of topological and primary properties within a 3D structural framework. The applicability of the workflow will be demonstrated by presenting the results of a case study from the Starfish field, ECMA, offshore Trinidad. It is intended for this paper to serve as a reference to geoscientists and engineers involved in brownfield and greenfield development planning. By extension, subsurface professionals who are involved in integrated reservoir modeling may also benefit from the work presented since geomechanics is often omitted from the modelling workflow.