METHOD OF WELL HEAT INSULATION IN PERMAFROST ZONE Russian patent published in 2000 - IPC

FIELD: oil-and-gas producing industry; applicable in construction and operation of oil and gas hot wells in permafrost zone. SUBSTANCE: method includes installation of packer and formation of heat-insulating layer by injection of foam plastic into well. Foam plastic is used in the form of pellets in mixture with cement-sapropel binder. Heat-insulating layer is formed in thawed zone of casing string-borehole annular space by injection pipes installed at an acute angle to borehole. It is sound practice to have in foam plastic pellets material fraction with diameters d1=2-7 mm and d2= 7-10 mm with their ratio d1:d2=(20-30):(80-70) wt.%. It is also desirable to have cement-sapropel mixture with dry cement-sapropel ratio of (1-5):(1-3). Heat-insulating material is used the following components, wt.%: cement-sapropel binder, 0.4-0.5; cement-water mixture, 90-93; foam plastic pellets, 10-7. Lower bases of injecting pipes are secured in ground with the help of cement butt end, and pipe upper ends are interconnected with one another and with wellhead. EFFECT: prevented thawing of frozen ground round hot wells and higher stability of wellbore. 6 cl, 1 tbl