Analysis of Uncertainty in Seismic Geomechanics Workflow: Towards 4D Seismic Calibration of 4D Geomechanical Models

Time-lapse (4D) seismic data provides spatially rich information on production induced stress changes. Unlike reservoir models that are often extensively calibrated using 4D seismic and production data, geomechanical models are typically very loosely calibrated to available 4D data. The purpose of this study is to develop a greater understanding of a typical 4D geomechanical model and what affect the uncertainty in typical input parameters have on modelled effective stress changes. Understanding how different modelling parameters effect stress change is extremely important if extensive 4D seismic calibration is to be possible. We use a Global Sensitivity Analysis technique on a sample of 1540 geomechanical models to assess the sensitivity of model inputs on the resultant vertical effective stress change. We successfully map each parameter to a sensitivity space and argue that by doing this we can reduce our initially considered ‘important’ inputs by 50%. Thus, by reducing the number of calibration parameters and gaining a greater understanding of the model parameter sensitivity to stress and displacement allows a better understanding of what and how geomechanical models can be calibrated using time-lapse seismic data.