Multi-scale Geomechanics: How Much Model Complexity is Enough?

Abstract

Nowadays oil and gas exploration and production is often performed in geomechanically challenging enviroments where the risks can be high and problems are costly. Choosing the right scale and complexity of a model is critical for performing an effective and efficient geomechanical analysis that addresses the problem without unnecessarily expending resources like time, computation power or software license costs.In this paper different geomechanical modeling techniques are compared for their accuracy and efficiency using a relatively simple (continental slope) and a more complex geological setting (submarine canyon). This has been done by comparing the resulting state of stress of 1D well-centric geomechanical models with those of reservoir-scale 3D geocellular and 4D finite-element models.The more complex submarine canyon model shows that in relatively complex areas the 1D and 3D geomechanical models no longer give accurate stress results and a 4D model is needed to accurately simulate the state of stress. On the other hand, the continental shelf model shows that in a simple geological setting creating a 1D wellbore-scale geomechanical model is an efficient and effective way of calculating stress. The 1D model gives an accurate state of stress comparable with the more complex 3D and 4D reservoir-scale geomechanical models. Not having to create, simulate and analyze a reservoirscale model can save time for better analysis of the results, dealing with uncertainties of the model and/or doing a sensitivity analysis.The paper concludes that the initial step in a geomechanical study is assessing the geomechanical application of the model, taking the complexity of the geological setting into account and based on that assessment chosing the modeling complexity that is necessary to get accurate results, without unnecessarily spending resources.