METHOD OF CONSTRUCTION AND CASING OF BRANCH HOLE Russian patent published in 2001 - IPC

FIELD: casing of boreholes in construction of branch hole in course of operation of oil and gas holes. SUBSTANCE: method includes the following stages: installation of support in parent hole in point below location of formed branch hole; installation of whipstock on support; cutting out of window in casing of parent hole and beginning of making of branch hole with use of section mill directed by whipstock; removal of whipstock; installation of deflector on support. Deflector has main body whose diameter is less than inner diameter of casing string of parent hole; drilling of branch hole to required depth; introduction of casing string into branch hole by deflecting of parent hole casing string using deflector until casing string assumes position at which the first part of casing string is found in branch hole and the second part, in parent hole; cementing round said casing string; removal of material ring from parent hole for separation of casing string and cement at joint of holes; removal of deflector from parent hole to free parent hole for passing behind branch hole. EFFECT: higher efficiency of fastening of casing string. 6 cl, 13 dwg