Multi-stage liner with cluster valves and method of use

A method of using a cluster valve assembly for successively opening a plurality of radial ports axially spaced along a liner situated within a wellbore, comprising:

• circulating cement downhole through the bore and returning uphole via the annulus between the liner and the wellbore;
• dropping a wiper ball down the liner and pumping it through the liner to clean residual cement by pushing it downhole ahead of the wiper ball;
• landing the wiper ball in a landing collar at the distal end of the liner;
• said cluster valve assembly comprising:
• a tubular liner defining a bore;
• a ball member;
• a ball seat, having an axial passage therein of lesser size than said ball member;
• a plurality of slidably moveable valve sleeves, located within said liner, each valve sleeve disposed within the bore and axially moveable relative to the liner along said bore from a first uphole position obstructing one or more ports in said tubular liner to a second downhole position in which said one or more ports are open;
• a corresponding plurality of collets each coupled to or integral with a corresponding valve sleeve and slidably moveable within said bore, each collet having one or more protuberances radially moveable from a first inward position where said protuberances engageably couple said collet to said ball seat when said valve sleeve and collet are in said first uphole position, to a radially outward second position disengaged from said ball seat when said valve sleeve and collet is slidably moved by said ball seat to said second downhole position wherein said ball seat becomes disengaged from said collet and protuberances thereof and said ball seat is thereby allowed to thereafter move further downhole;
• said ball seat initially engaging a most uphole first collet and corresponding first valve sleeve;
• and
• wherein said ball and ball seat when exposed to uphole fluid pressure, together move downhole in said liner and engage said first collet and move said corresponding first valve sleeve downhole to said second downhole position to thereby open said one or more ports in said liner previously obstructed by said first valve sleeve and said ball seat thereafter becomes released from engagement with said first collet and thereafter with said ball member moves further downhole to engage a second collet and corresponding second valve sleeve and thereafter again move together as a unit to cause said second valve sleeve to move downhole to said second downhole position to open additional ports in said liner previously obstructed by said second valve sleeve.