An investigation of the effects of casing erosion and cement elastic modulus on the casing collapse phenomenon: a case study on an oil field in southwest Iran

Casing collapse phenome during the production of boreholes drilled in high-pressurized reservoirs are a common challenge that the petroleum industry is facing universally. Such a problem has been observed 21 times in the boreholes drilled at one of the high-pressurized fields in Southwest Iran whose 56-production-well consequently reduced to 38 (by losing 18 producers due to the casing failure). Based on the studies conducted on the collapse phenomenon different factors contribute to the occurrence of such a problem. The important factors have been reviewed, analysed, and reported in the literature are:  The stresses applied due to point-load on the wellbore and the casing by geomechanical and tectonic effects  Casing erosion  The presence of void spaces between the casing and the wellbore wall  Casing type and quality  Cement type and quality  Pore pressure (related to Geomechanical effect?)  The quality of cementing bondage In the present study, taking advantage of ABAQUS, the efforts have been put to analyse and study the effects of the casing erosion and cement elastic modulus on the stress distribution around the borehole by simulating formation-cement-casing system considering in-situ stress. The cement displacement and the consequent stress tensor applied on the casing have been investigated. The numerical studies have been conducted in two cases considering the cement elastic modulus higher and lower than the formation elastic modulus. The results showed that the point-erosion of the casing has a stronger effect than that of the cement elastic modulus on the stress distribution around the borehole and the displacement of the surrounding cement.