DEVICE AND METHOD FOR PROTECTION AGAINST LOOSE MATERIAL Russian patent published in 2016 - IPC E21B7/08 E21B33/10 

FIELD: mining.

SUBSTANCE: group of inventions relates to systems and methods of protection of the lower part of the main well bore against accumulation of debris. Well system unit comprises a deflecting tool installed in a casing string and determining the deflecting surface and an inner channel passing in longitudinal direction from the deflecting surface; one or more sealing units arranged on the inner surface of the internal channel of the deflecting tool; and a protective device for the well bore, located on the inner surface of the internal channel over one or several sealing units and made with a possibility of expansion during transition from a non-swollen state into a swollen state.

EFFECT: there is ensured protection of one or more sealing units from accumulating debris formed during drilling.

20 cl, 6 dwg