Cyclic Pressure Response of Deformed Casing after Discrete Geomechanically-Driven Shear Displacement in Multi-Fractured Horizontal Wells
Authors: Dall’Acqua D. , Yung V. Y. B. , Admiraal K. M. 
Published: September 2024

Geomechanically-driven casing deformation that limits well accessibility is known to occur in certain basins where hydraulic fracturing is employed to stimulate production. Completions teams are often faced with decisions relating to whether the well can still be operated at the original stimulation pressure, and the impact of remedial milling work on pipe capacity. This paper specifically explores the structural response of casing to cyclic pressure loading in situations where local deformation has previously been caused by discrete formation shear movement.

Discrete geomechanical shear generally manifests in casing as a combination of centerline offset and local pipe ovality, and can be quantified through appropriately-interpreted geometric logs. These logs can be used as input to numerical analysis work, which can provide estimates of the associated plastic strain distribution and loading state in the deformed tubular and insight into fundamental casing response after the deformation has occurred.

Using three-dimensional finite element analysis (FEA) of a typical tubular subjected to a shearing event and subsequent cyclic re-pressurization, a parametric approach is taken to estimate the impact of shear magnitude and axial extent on subsequent local strain development, pipe ovality evolution, and cyclic pressure capacity.

Numerical analysis generally indicates modest shear-induced casing deformation will not appreciably reduce the rupture pressure capacity of the casing, provided excessive wall thickness is not lost during milling operations and the casing retains its ductility in the well environment. Consequently, accessibility issues will tend to govern casing functionality before shear deformations compromise its integrity. This does not cover all possible scenarios or preclude the need for diligence in assessing the casing's capacity, and will benefit from appropriate characterization of the deformation before (and preferably after) re-pressurization and after any intervention operations that might compromise integrity. By contrast, industry experience indicates connections can be especially sensitive to shear loads, high local curvature loads, and axial tensile strain, and will generally be less tolerant to re-pressurization without seepage or parting if they are unfavorably located relative to the shear location.

While many simplifications and approximations are used in this work, the results provide an initial direction should a more rigorous evaluation basis be required to support completions team decisions.

This paper extends prior work by the authors to characterize burst and collapse susceptibility of tubular bodies in post-yield strain-based loading conditions, with the specific objective of assessing the potential need to reduce fracturing pressure for subsequent stages. Initial validation of the analysis results has been obtained by comparison to field experience with well-characterized deformation shapes, and will benefit from more comprehensive study to support confidence in field application.