WELL OPERATING PROCEDURE Russian patent published in 2009 - IPC E21B43/00 E21B33/13 

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil industry and can be implemented at well operating. The essence of the invention is as follows: the procedure consists in boring from under surface casing, and in lowering and cementing a casing string with a tail piece of diametre smaller, than diametre of the casing string. According to the invention boring with a bore bit of one size is performed to a lower water saturated reservoir. The beginning of the tail piece in form of a transfer from the casing string to the tail piece is located in a lower zone of a producing oil saturated reservoir. The length of the tail piece is chosen sufficient for passing a lower zone of the producing oil saturated reservoir and a dense impermeable interlayer located under the producing oil saturated reservoir. The length of a cement ring in the lower zone of the producing oil saturated reservoir and zone of the dense impermeable interlayer located below the producing oil saturated reservoir is determined on base of isolating water at pressure drops in a well between a current reservoir pressure and a current bottom hole pressure on the assumption, that 1 running metre of the cement ring around the tail piece withstands drops of pressure 2 MPa without loosing insulating properties. Also well operating is performed when bottom hole pressure is achieved, whereat the cement ring around the tail piece facilitates insulation of water from the lower water saturated reservoir.

EFFECT: facilitates increased reliability of well insulation from water inrush from lower water flooded reservoir.

2 cl, 1 ex, 1 dwg