Selective Washing Device for Wells is applied for performing injections of plugs with fillers during drilling with bottomhole engine. The device is mounted above BHA.

When the device is not actuated, drilling mud goes through it smoothly. To activate the device it is necessary to drop an activation ball into drilling pipes and pump until it is set into a seat. When the activation ball reaches the seat, circulating ports open. Due to this BHA is hermetically disconnected as it is mounted lower. The circulation goes through the side ports and the bridging material is pumped into loss zones. When a drilling pump is stopped, a spring returns the stem to the top position and circulation ports are closed.

After all the planned technical operations two steel deactivation balls are dropped into drilling pipes and pumped with calculated volume of drilling mud in order to deactivate the device. Deactivation balls reach the device and close the ports due to liquid flow and the deactivation ball is pumped through a seat. The circulating ports are closed. Drilling mud continues to flow below the device. Used balls both activation and deactivation one come to a trap and don’t interfere with the following operations.