SECTIONAL CASING OF WELL Russian patent published in 1997 - IPC

FIELD: oil and gas production industry. SUBSTANCE: this relates to construction of oil, gas and other wells drilled in zones of plastic rocks in conditions of abnormally high external pressure. Well drilled in interval of plastic rock deposition is provided with system of concentric casing strings with strengthening rings installed on outer surface of tubes. Distance between neighboring side faces of rings is determined by formula: , where R - average radius of casing tube, m; σ_y - yield point of casing tube material, MPa; h - equivalent thickness of casing tube sector subjected to contact rock pressure, m, determined by formula: h=R_o-0,866R_i, where R_o - outer radius of casing tube, m; R_i - inner radius of casing tube, m; R_c - contact pressure of plastic rock, MPa. Axes of strengthening rings on tubes of subsequent casing string are displaced relative to side faces of neighboring rings on tube of preceding casing string to half of design distance. Overall dimensions of rings are equal to overall dimensions of sleeve joints of casing strings. EFFECT: high efficiency. 1 dwg