METHOD FOR PREPARING WELL TO LOWERING AND CEMENTATION OF CASING STRING Russian patent published in 2000 - IPC

FIELD: oil and gas production industry. SUBSTANCE: method particularly relates to fortifying wells by casing pipe strings. Method implies treating, washing, cleaning of well walls by means of scraper devices. After treating of well bore, undertaken is processing of clay drilling fluid. Reduced is static shear stress of clay drilling fluid down to value at which change of temperature and electric field in well at which there is no increase of it in time to values exceeding tangential along wall stresses at movement of plugging solution. Lowered into well is drilling tool provided with scraper devices. Previous casing string is cleaned of wall-adjacent structurized clay drilling fluid. Clay drilling fluid is additionally processed to obtain properties reached at first treatment. Casing pipe string is now lowered into well and its cementation is carried out. Application of method improves quality of cementation. EFFECT: higher efficiency. 1 tbl