METHOD OF DRILLING OFFSHOOTS FROM AN OPENHOLE WELL HORIZONTAL PART Russian patent published in 2019 - IPC E21B7/04 

FIELD: soil or rocks drilling.

SUBSTANCE: invention relates to the field of oil and gas wells offshoots drilling. Prior to drilling of offshoots at the mouth of horizontal well with open bore, assembly is assembled from below upwards: telesystem, one weighted drill pipe, whipstock with inclination angle of working surface 4°, assembly is lowered on the tubing string to the main horizontal uncased hole so that the whipstock is in the interval of offshoot cutting, the whipstock is oriented. Then, at the well head, assemblage is assembled from below upwards: milling cutter, downhole drilling motor (DDM), hydraulic emergency disconnector, assembly is lowered to the tubing string on the flexible pipe string. Offshoot is drilled and drilled with load at cutter to 1.0 t. Drilling process is stopped, and assembly is performed on horizontal string on flexible pipe string. Geophysical instrument is lowered to tubing string to borehole of drilled offshoot on flexible pipe string to define minimum distance from drilled offshoot to oil-water contact (OWC). At minimum distance from drilled offshoot to OWC from 5 to 10 m, tubing string is lowered into tubing string, equipped with rotary spherical head fitted on end, to the bottomhole of the drilled offshoot and acid treatment of the bottomhole zone of the drilled offshoot. At a minimum distance from the drilled offshoot to OWC of more than 10 m, a string of flexible pipes with DDM is lowered into the tubing string, oscillator-turbulence promoter and bit at the end, and drilling of the offshoot is continued with the bit load up to 1.5 t to the specified face. After the offshoot bottom is reached, the drilling process is stopped and the assembly is lifted to the flexible pipes from the tubing string, string of flexible pipes with rotating spherical nozzle at the end to the depth of the drilled bottom of the offshoot is lowered into the tubing string and acid treatment of the bottomhole zone of the drilled offshoot is performed. Pressure of treatment of bottomhole area of offshoot may vary for each offshoot.

EFFECT: enabling accuracy of orientation direction of sidetracking to the right relative to the main horizontal uncased wellbore, exclusion of deviation of trajectory of offshoot during drilling, exclusion of opening of water-bearing formation, higher efficiency of treatment of side wells with hydrochloric acid solution using flexible tube with spherical nozzle, improving treatment quality of bottomhole zone of well, reducing duration of drilling of offshoot.

1 cl, 7 dwg