METHOD FOR SAND PLUG EFFLUENT WASHING FROM WELL Russian patent published in 2020 - IPC E21B37/00 

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil and gas industry, namely, to methods of washing sand plugs during well repair. Method includes mounting on the wellhead from bottom to top: a chisel, a pipe string, equipped from below with helical self-braking mechanism - a screw pair, which is a hollow cylindrical shaft and hollow cylindrical housing, having the possibility of rotating about its axis, lower end of which is rigidly connected to the bit, lowering the pipe string to the head of the sand plug, unloading the pipe string onto the plug. Under action of axial force created by weight of pipe string on plug, there is locking cylindrical shaft and its translational movement down, cylindrical housing rotates, bringing into rotary motion bit. Pipe string is lifted, when shaft reaches extreme lower position limited by upper stroke limiter, repeated extension of pipe string for continuation of drilling cycles aimed at destruction of plug, after shaft returns into initial position until it stops in lower stroke limiter, at continued rotation of the bit during lifting of the pipe string, drilling the plug to the moment when friction forces do not stop its rotation. Flushing is carried out using tubing string or drill string, or flush-type long pipes of coil tubing unit. After lowering the pipe string, the upper end of the pipe string is fastened to the wellhead with the possibility of direct washing with liquid of the pump unit, discharge of the annular space and the chute reservoir. Pipe string is lowered with simultaneous circulation of liquid by direct flushing until plug head is reached by chisel head. A shutoff element is dropped into the pipe string, the upper end of the pipe string is re-tied to the wellhead with the possibility of backwashing. Cork is removed by cyclic hydraulic and mechanical action. Each cycle includes drilling of a plug with a chisel, limited lifting of a pipe string and drilled sand removal from the well. Drilling cycle is performed during drilling of part of sand plug by unloading pipe string on sand plug until the stop of cylindrical housing in lower stroke limiter of hollow cylindrical shaft, and limited rise of pipe string is performed at lifting of pipe string with screw pair and bit to the stop of cylindrical housing into upper limit stop of hollow cylindrical shaft. Removed drilled sand is carried out at holding pipe string in fixed position with simultaneous circulation of liquid by backwashing for 10-15 minutes. With each cycle, liquid consumption during drilled sand removal from the emergency well is increased by 15-20% of the liquid flow rate in the previous cycle. After reaching the face, drilled sand is removed without limited lift of the pipe string.

EFFECT: increased efficiency of drilled sand removal from well, exclusion of probability of pipe string clamping in process of lowering into well, reduced duration of repair works, expanded process capabilities of plug washout.

1 cl, 5 dwg