Mechanical Analyze of Casing Failure with Sand Production in Loose Sandstone Reservoir

Abstract

Sand and fluid may both run into the wellbore during the production of loose sandstone reservoir, but cavities around the wellbore are prone to form when sand is produced, which makes the casing lost the protection of the formation and casing failure comes about. The limitation of thin cylindrical shell buckling model is analyzed and a mechanical model for casing under sand production is established by M.M.протодьяконоВ’ theory and the pressures of the casing where cavities exist are determined by numerical method. The research shows the cavity height and sand production volume are in a power relationship; the cavity height and axial force are in a linear relationship. With the increase of the overburden pressure, higher steel grade have to be used to keep the reliability of the casing. The research provides theoretical foundation for production casing design and casing strength verification with reasonable sanding.