The Role of Deformation History of Buckle Folds on Sustainable Pore Pressure Magnitudes

Subsurface engineering applications such as waste water disposal or CO2 sequestration require the selection of suitable injection sites which depends critically on the assessment of geomechanical risks such as fracture initiation or fracture reactivation. As an analogue to hydrocarbon production sites, buckle fold structures are a preferred structural trap for fluid storage and become of interest for waste water disposal or CO2 sequestration. In this contribution, 3-dimensional finite element analysis is used to quantify the influence of different permeability distributions in a multi-layer visco-elastic buckle fold system on the resulting state of stress throughout the deformation history of the fold. Based on the advanced, tensor based concept of pore pressure – stress coupling, pre-injection analytical estimates of the maximum sustainable pore pressure change, ΔPc, for fluid injection scenarios can be calculated if the state of stress of a geologic structure can be quantified using numerical models. The results of this study show that the minimum ΔPc is varying throughout the deformation history of multilayer buckle folds and different locations within the structure show great variability in ΔPc. Furthermore, the permeability distribution of the various layers in the multilayer fold system has great influence on minimum ΔPc. It is concluded that geomechanical risk assessment for active fold belts needs to consider the complete deformation history of geologic structures such as buckle folds