METHOD OF WELL STAGE CEMENTING Russian patent published in 2002 - IPC

FIELD: drilling of oil and gas wells, particularly, methods of well strong cementing where producing formations are presented by fissured or high-permeability reservoirs. SUBSTANCE: method includes running into well casing string with device for stage cementing installed above producing formation, cementing valve with seat and shoe in lower part; injection of cement mortar of the first stage, removal of excessive amount of cement by direct flushing through said device and letting cement setting injection of cement mortar of the second stage through said device; reduction of pressure after forcing of cement mortar and removal of its excessive amount through tubing string and letting the cement setting. Device for stage cementing is located on hollow plugs which are installed on casing string. Hollow plugs protrude by their bottom part inside it and have weak cross-section. After running of casing string down to designed depth, introduced into its cavity is tubing with blind sealing plunger and perforated branch pipe at end and shearing coupling. Injection of cement mortar of the first stage is performed through tubing with closed interpipe annulus. Then tubing is lowered and hollow plugs are broken by shearing coupling. Sealing plunger is simultaneously landed onto seat above cementing valve. After removal of excessive amount of cement mortar, tubing is raised so that perforated pipe is located somewhat below the device for stage cementing. Cement mortar of the second stage is also injected through tubing with closed interpipe annulus. EFFECT: simplification and reduced cost price of the method. 4 dwg