METHOD FOR BOREHOLE ENLARGEMENT, ASSEMBLY OF TOOLS FOR IMPLEMENTATION OF METHOD, EXPANDABLE HYDRAULIC UNDERREAMER, CENTRALISER AND STABILISER Russian patent published in 2014 - IPC E21B7/28 E21B17/10 

FIELD: oil and gas industry.

SUBSTANCE: group of inventions pertains to drilling of wells and can be used for their enlargement and also in process of repair in wells. Assembly of tools is placed in a well transferring it from transport position to the operating one. Section of the well borehole is enlarged bottom-up with centring of the tool assembly in regard to the casing string. In the process of the well borehole enlargement the tool assembly is centred additionally in regard to the surface of the well borehole formed as a result of its enlargement. Centring of the tool assembly in regard to the casing string is made at least in two points located above the expandable hydraulic underreamer of the tool assembly. Enlargement is made up to the diameter equal or exceeding the initial diameter of the well, whereupon section of the well borehole is enlarged up to the required diameter. Centring of the tool assembly made in regard to the surface of the well borehole formed as a result of enlargement is carried out at least in one point located below the expandable hydraulic underreamer of the tool assembly and in regard to the casing string additionally at least in one point located below the expandable hydraulic stabiliser of the assembly. The tool assembly is used that includes expandable hydraulic underreamer, expandable hydraulic stabiliser installed directly under the expandable underreamer. In the tool assembly at least two centralisers are made expandable and hydraulic and installed directly over the expandable underreamer. In the lower part of expandable hydraulic centraliser there is a choking unit.

EFFECT: improving new surface quality of the well received as a result of its enlargement, enhancing productivity and efficiency of works on bottom-up enlargement of the well borehole.

17 cl, 23 dwg