It is when a hole is worn in the pipe, and becomes increasingly larger due to circulating drilling fluid. This can eventually sever or twist off the pipe entirely. Washouts usually occur at rotary connections, due to improper make-up, cracks or defective materials. From the surface, a washout may be indicated by a gradual decrease in pump pressure at constant pump rate.

Washout is Suspected:

If a washout while drilling is suspected, then the following action should be taken:

🔹Check that the pressure drop is not associated with a drop in the pump strokes.

🔹Pull the string off the bottom and stop circulating immediately.

🔹Have the surface system, e.g., rotary hose, drag chains, HP pipework, etc., checked for leaks and potential spills to sea.

🔹Stop rotating, but continue working the pipe.

🔹Check the drill string weight has not changed.

🔹If no leak is found, restart the mud pumps, but keep people clear of the floor while pulling the stand back up through the rotary.

🔹Derrickman to sound the pumps and check the pop-offs, etc.

🔹The driller is to change to a second pump or pump combination and double-check the pressures.

🔹Checking against previous SCR figures is unlikely to be of help as the circulating pressures involved are often too low to be of value.

🔹Well Site Leader to check the pressure chart and look for signs of characteristic pressure drops or indications that the pressure loss may be attributed to a bit nozzle clearing or a heavy slug being circulated the system.

🔹If an MWD tool is in the drill string, check to see if it is still pulsing OK (lack of a pulse could indicate a pipe washout has occurred above the tool).

🔹Is the system pressure fluctuating more than normal as the string is worked up and down? (Longitudinal crack washouts can open and close as the string, especially drill pipe, goes from tension into compression.)

🔹If unable to establish any problems with the surface equipment, then consider carrying out a pump test as detailed in section 3.2.2 below.

🔹If no pump test data is available, then close in the IBOP (or Standpipe valve if the IBOP is not designed to hold pressure from above). Then using the mud pump, pressure test the surface system to the previous circulating pressure.