METHOD FOR WELL CONSTRUCTION IN COMPLICATED CONDITIONS Russian patent published in 2017 - IPC E21B21/08 E21B43/10 E21B33/14 

FIELD: oil and gas industry.

SUBSTANCE: method involves drilling and fixing a well bore with a casing string the cap of high-pressure formation, drilling and opening high-pressure formations using anti-flow measures. After the opening of the high-pressure formation, additional drilling of a sump is performed. A buffer liquid based on cooled salt water is injected into the formation bottomhole zone. The partially crystallized cooled salt water, obtained earlier while drilling the high-pressure formation, is used from the pit. A cement slurry based on magnesian-phosphate slurry is injected in a specified volume. It is pumped into the developing zone under pressure providing 5% margin over the pressure of the high-pressure formation. After pumping, the well is left on this counter pressure. If necessary, the operation is repeated. After development intensity of is reduced to 5-10 m³/h, drilling is continued at the overflow with this production rate with simultaneous injection of obtained salt water inflow into preformed absorption zone. When the bottom reaches design marks of target production formation with oil or gas saturation, additional casing string is lowered with crush strength characteristics exceeding formation pressure developing within heavy salt water. Said string is grouted with heavy cement and magnesium phosphate grout solution taking into account exceedance of hydrostatic pressure of the cement solution over pressure in the formation under development. The casing string pressure testing is performed not earlier than 3 days after cementing. Next, drilling is continued along the target oil or gas formation.

EFFECT: improving the efficiency of well construction and ensuring trouble-free oil and gas production.

1 ex, 3 dwg