METHOD OF DRILLING PILOT HOLE IN INCOMPATIBLE DRILLING CONDITIONS Russian patent published in 2025 - IPC E21B33/10 E21B7/04 E21B7/20 

FIELD: earth or rock drilling.

SUBSTANCE: invention relates to oil and gas industry, in particular to methods of drilling and device of pilot shafts in incompatible drilling conditions. Method of drilling a pilot borehole in incompatible drilling conditions involves drilling a well with the main casing string and its cementing above the first zone with a complication, drilling below the main casing with crossing of the first zone with a complication without crossing the second zone with a complication, which provides the occurrence of incompatible drilling conditions, the installation of the temporary casing below the main casing with the intersection of the first zone with a complication, cementing the lower part of the temporary casing with the formation of a cement sleeve, drilling of cement sleeve and drilling of pilot borehole with crossing of second zone with complication, which provides occurrence of incompatible drilling conditions, at that, after the end of use of the pilot borehole, the pilot borehole is eliminated by installing a cement bridge with its entry into the temporary casing string, part of the temporary casing is removed above the cemented section of the temporary casing with its extraction from the well, further drilling is performed using the well section above the cemented section of the temporary casing string. Effective overflow, lost circulation, gas and oil seepage zones are provided, and as a result, safety at the stage of drilling and further operation of wells is provided.

EFFECT: simplified process of drilling additional boreholes from initial pilot borehole due to removal of part of casing string, as well as saving of consumables due to removal of part of casing string from well.

7 cl, 10 dwg