METHOD OF WELL STAGE CEMENTING Russian patent published in 2003 - IPC

FIELD: drilling of oil and gas wells, particularly, methods of stage cementing of wells producing formations presented by fissured or high-permeability reservoirs. SUBSTANCE: method includes running of casing string with devices for stage cementing, cementing valve with seat and shoe in lower part into well. Devices for stage cementing are installed above producing formation and located on hollow plugs installed on casing string. Bottom part of hollow plugs protrudes inside casing string, and hollow plugs have weak cross-section. Cement mortar of the first stage is injected higher than devices for stage cementing. Initial position of cement mortar of the first stage is injected with setting retarder, and the last portion together with setting accelerator. After injection of full volume of the first stage mortar, run inside casing string is tubing string with shear coupling at its end. Hollow plugs are destroyed Cement mortar located above devices for stage cementing is washed out through hollow plugs with closed annular space. Cement mortar is left for its setting. Then cement mortar of the second stage is injected through hollow plugs. Cement mortar is left for its setting. EFFECT: excluded formation of water bags behind casing string in stage cementing of wells, and higher quality of cementing. 2 cl, 4 dwg