Novel laboratory setup for realistic wellbore cement and formation integrity studies

Abstract

Oilfield wellbore integrity relies on a good well cement formulation, placement, and resistance to solicitations when aging, either due to chemical or stress changes. Requirements are that the cement sheath and plugs remain as proper hydraulic barriers for all foreseeable future. Thus, to qualify the cement formulations with respect to various types of stress changes, it is important to carry out these tests in the field relevant conditions in the laboratory. These tests will contribute to improved understanding of the limiting factors influencing the well integrity and assist in design of remediation strategies. Hence, a new experimental setup designed for studying near wellbore systems in field conditions is introduced. The setup comprises of an advanced X-ray cell with the possibility of three independent pressure controls of casing, pore and formation pressures. The experiments are carried out under simultaneous X-ray Micro-CT imaging allowing to monitor the in-situ mechanical changes. Numerical calculations in the finite element domain are carried out for the same test conditions with first results showing the evolution of radial cracks in the cement sheath and the formation rock submitted to excessive well pressures. The test results confirm with the numerical simulation. These results may provide valuable input for near-wellbore integrity assessments. • A unique laboratory set-up with more relevant field conditions for study cement and near wellbore formation integrity. • X-ray imaging system can visualize radial fractures in the annular cement and formation in the laboratorysetup. • Fracture structures are qualitatively and quantitively different, with and without confinement pressure. • Using a finite element tool, OOFEM, to model the obtained experimental results.