Mitigating swab and surge piston effects in wellbores

Abstract

A method of mitigating undesired pressure variations in a wellbore due to movement of a well tool string in a well can include selectively decreasing and increasing fluid communication between sections of a wellbore on opposite sides of at least one well tool in the well tool string, the fluid communication being increased in response to detecting a threshold movement of the well tool string relative to the wellbore. A well tool string can include a well tool connected in the well tool string, and having an enlarged outer dimension relative to adjacent sections of the well tool string, a flow passage extending between the well tool's opposite ends, a sensor, and at least one flow control device which selectively permits and prevents fluid communication between the opposite ends via the flow passage, in response to an output of the sensor indicative of movement of the well tool string.

Dependencies are inferred from the claim text.