Positive displacement apparatus for selectively translating expander tool downhole

An apparatus for translating an expander tool axially within a wellbore in order to facilitate the expansion of an upper portion of a liner string into a surrounding string of casing, the apparatus comprising:

• a fluid transfer chamber having an upper end and a lower end;
• a displacement piston having an upper end and a lower end, the upper end of the displacement piston acting upon the expander tool, and the lower end being in communication with the fluid chamber;
• an inner mandrel, the inner mandrel defining a tubular body nested essentially concentrically within the displacement piston;
• an outer sleeve, the outer sleeve defining a tubular body surrounding the displacement piston such that the displacement piston is nested essentially concentrically within the outer sleeve;
• a rotor piston having an upper end and a lower end, the upper end of the rotor piston sealingly residing within the fluid transfer chamber;
• oil, the oil loaded in an annular region defined between the expandable liner string and the outer sleeve;
• an annular feed channel placing the annular region and the fluid chamber in fluid communication;
• an inflow valve permitting the oil to flow from the annular region into the fluid chamber;
• an outflow valve permitting the oil to flow from the fluid chamber against the lower end of the displacement piston in response to rotational movement of the rotor piston;
• and
• the fluid chamber sized and configured such that reciprocal movement of the rotor piston causes axial movement of the displacement piston within the wellbore.

An apparatus for translating an expander tool axially within a wellbore in order to facilitate the expansion of an upper portion of a liner string into a surrounding string of casing, the apparatus comprising:

• a fluid transfer chamber having an upper end and a lower end;
• a displacement piston having an upper end and a lower end, the upper end of the displacement piston acting upon the expander tool, and the lower end being in communication with the fluid chamber;
• a rotor piston having an upper end and a lower end, the upper end of the rotor piston sealingly residing within the fluid transfer chamber, and the lower end having a bottom face, the bottom face having a wave form configuration;
• a spring disposed in the fluid transfer chamber, the spring biasing the rotor piston to ensure essentially continuous contact between the bottom face of the rotor piston and the top face of the stator member;
• a stator having an upper face having a wave form configuration which mates with the bottom face of the rotor piston;
• and
• wherein the bottom face of the rotor piston rides on the top face of the stator member such that rotation of the rotor piston imparts an upstroke and a downstroke to the rotor piston, causing the rotor piston to reciprocate axially within the fluid transfer chamber such that oil is drawn into the fluid transfer chamber on the downstroke of the rotor piston, and oil is extruded under pressure against the displacement piston on the upstroke, thereby imparting axial movement to the displacement piston and to the expander tool within the wellbore.