METHOD OF WASHOVER OF HORIZONTAL WELL Russian patent published in 2014 - IPC E21B21/00 

FIELD: oil and gas industry.

SUBSTANCE: method comprises the creation of drilling fluid circulation using the direct layout of washover by pumping through the drilling pipe string with bit, lowered into a well of main drilling fluid and drilling fluid with viscosity, ensuring the increased cutting-carrying capacity. An aerated flush fluid is used as a drilling fluid. During washover with aerated flush fluid the drilling pipes are lowered at the axial speed 20 m/h and at rotational speed 40 rpm. After passing of each 5 m the string lowering is paused and it is raised by 2 meters, the circulation with aerated flush fluid is performed at increased flow rate during 15 minutes, then the lowering is continued. Polymeric bars from acrylic copolymer, soluble paper and soluble cork soluble in aerated flush fluid are used as a drill fluid with the increased cutting-carrying capacity. Bars are thrown off into the pipe string from the wellhead at extension of each pipe of the drill column, starting from the interval of build angle of open borehole above higher 40 degrees at washover of horizontal well and until achievement of the open borehole foot.

EFFECT: washover performance, drilling fluid stability is increased, probability of differential sticking of the string is decreased.

2 dwg