Core barrel

A core barrel device for use in obtaining a core sample from a formation, comprising:

• an axially extending tubular string having a front end, wherein the term “front” is determined relative to an axial direction of advance of said core barrel device into a formation from which a core sample is to be taken,
• an axially extending external tube coaxially fixed to said front end of said string,
• an axially extending front section of said external tube that extends coaxially through said external tube and projects from said front end of said external tube for selective movement axially relative to said external tube,
• an axially extending annular core bit coaxially mounted on said front section of said external tube,
• an axially extending internal tube assembly retrievably mounted coaxially in said external tube for retrieval through said string,
• an axially extending internal core tube mounted coaxially with said internal tube assembly, said internal core tube being mounted to be held fixed in rotation with respect to said formation and said front external tube section being driveable in rotation about a central axis independently of said internal core tube, and
• fluid flow passages in said core barrel device to convert a sampling fluid pressure flowing through said string into a thrust force for thrusting said internal tube assembly toward said front section of said external tube in response to said thrust force.