Well tool actuator and isolation valve for use in drilling operations

A well tool actuator, comprising:

• a series of closed chambers which are openable only once and which, when opened in succession, cause the well tool to alternate between multiple predetermined configurations, the multiple predetermined configurations comprising a piston which alternately displaces in opposite directions;
• and
• a sensor, wherein the chambers are opened in succession in response to detection of a stimulus by the sensor.

A drilling isolation valve, comprising:

• an actuator including a series of closed chambers which are openable only once and which, when opened in succession, cause the drilling isolation valve to be alternately opened and closed.

A well system, comprising:

• a drill string positioned in a wellbore;
• and
• a drilling isolation valve which selectively permits and prevents fluid flow through a passage extending through a tubular string, the isolation valve including a sensor which senses manipulation of the drill string in the tubular string, whereby the isolation valve actuates in response to the sensor detecting a predetermined pattern of the drill string manipulation, wherein the isolation valve includes a series of chambers which, when opened in succession, cause the isolation valve to be alternately opened and closed, and wherein the succession comprises opening a first chamber in the series of chambers, then opening a second chamber in the series of chambers, and then opening a third chamber in the series of chambers.