Experimental and finite element modelling evaluation of cement integrity under diametric compression

Abstract

With the increased exploration activity in unconventional and extreme operational environment, well integrity is becoming a challenging problem. Cement sheath, being an important barrier element, should be designed properly for adaptation of complicated loads surrounding the wellbores. This experimental and modelling study evaluates casing-cement-formation system under diametrically compressive load.Digital image correlation (DIC) technique was employed to examine the strain distribution and failure in experimental setup. A 3D numerical model was developed and the comparison between simulation and experimental results indicated a reasonable match. Using validated model, the effect of cement elastic properties on stresses in cement was studied. The stress distribution in the cement-formation system shows that casing-cement interface is the weakest point in the system, thus it has the highest risk of failure. The failure initiates at orientation parallel (θ = 0°) to the applied load followed by in perpendicular (θ = 90°) direction. Hoop stress is more sensitive to Young's modulus and Poisson's ratio than radial stress, so it is more critical for the failure assessment. In general, flexible cement with low Young's modulus and high Poisson's ratio has low risk of failure.