Dr. Enayatpour and Dr. van Oort will present their new well abandonment paper at the 2019 SPE ATCE Conference in Calgary (Sept.30 – Oct.2, 2019), titled “Exploiting Shale Creep Deformation to Create Annular Barriers for Well Plugging and Abandonment: Experimental Investigation and Numerical Simulation “. The paper (SPE 195966) presents the first results of an experimental investigation and numerical modeling study into the nature of the “shale-as-a-barrier” phenomenon. Specifically, focus is on laboratory and field scale numerical simulation of creep behavior of North Sea Lark shale rock for oil and gas well plug and abandonment purposes. In Finite Element simulations of the shale creep phenomenon, the authors have used the time-hardening creep model, which assumes a non-linear relationship between creep strain and stress, temperature and time. The model parameters were obtained from a curve fit of laboratory experimental results conducted for a creeping shale. Then, using the experimentally-derived parameters, numerical simulation was performed for a laboratory scale model and result was validated against laboratory results. Once this validation had taken place, the model size was extended to the field scale for prediction of annular closure time and barrier formation. Simulations show a strong correlation between rock stiffness and annular gap closure time, as expected; hence, the success of any “shale-as-a-barrier” project is a distinct function of shale rock stiffness. Lowering near-wellbore stiffness artificially may accelerate annular barrier creation of slowly creeping shale formations.
