Analysis of Thaw Subsidence Impacts on Production Wells

For the past few decades, with depletion of hydrocarbons in more readily accessible regions, petroleum operators have shown increasing interests in exploring onshore oil and gas reserves in Arctic areas, which are typically overlain by substantial permafrost layers on the order of 150 to 500 m thick. A key challenge to the completion of these wells is how to manage the impact of thaw subsidence of permafrost layers throughout expected well life.
This paper presents a methodology for analyzing well deformation under the thaw subsidence loading. The well evaluation methodology includes several analysis programs in sequence, such as wellbore hydraulic and heat transfer analysis, to determine the heat input to the permafrost interval due to the production of hydrocarbons; geothermal analysis, to estimate the extent of the permafrost thaw; geomechanical and soil deformation analysis, to calculate the thaw-induced soil stress and movement; and casing-formation interaction analysis, to evaluate the impact of thaw subsidence on the potential deformations and mechanical and hydraulic integrity of well casing systems. Two examples are presented to demonstrate potential well failures, such as buckling and shear, caused by thaw subsidence movement for single and multiple well design scenarios, respectively. The presented methodology is recommended for optimizing well completion designs to minimize the well failure potentials.