Seat assembly with counter for isolating fracture zones in a well

Abstract

A specially designed rotary indexing system and associated operational methods are incorporated in a downhole control device, representatively a sliding sleeve valve, having an outer tubular member in which an annular plug seat is coaxially disposed. The plug seat is resiliently expandable between a first diameter and a larger second diameter and is illustratively of a circumferentially segmented construction. The rotary indexing system is operative to detect the number of plug members that pass through and diametrically expand the plug seat, and responsively preclude passage of further plug members therethrough when such number reaches a predetermined magnitude. Such predetermined magnitude is correlated to the total rotation of an indexing system counter ring portion rotationally driven by axial camming forces transmitted to the rotary indexing system by successive plug member passage-generated diametrical expansions of the plug seat.

1 . A control apparatus operably positionable in a wellbore, comprising:
 a tubular member extending along an axis;   an annular seat structure coaxially supported within the tubular member and being diametrically expandable by a plug member passing axially therethrough from a first diameter small enough to block passage of the plug member through the annular seat structure to a second diameter permitting the plug member to pass through the annular seat structure, and then being contractible to the first diameter; and   a counter apparatus operative to lock the annular seat structure at the first diameter in response to a predetermined number of plug members having passed through and diametrically expanding the annular seat structure to the second diameter, the counter apparatus including:
 a first portion rotationally indexable about the axis; 
 a second portion operative, in response to a diametric expansion of the annular seat structure to the second diameter, to engage and rotationally index the first portion through a predetermined angle about the axis; and 
 a third portion separated from the first portion by an axially extending separator that separates and prevents one of the first and third portions from displacing toward the other of the first and third portions, 
 one of the first and third portions having a separator receiver that receives the axially extending separator when the separator receiver aligns with the axially extending separator in a manner that one of the first and third portions displaces towards the other of the first and third portions and lock the annular seat structure at the first diameter. 
   
     
     
         2 . The control apparatus of  claim 1 , wherein the axially extending separator is an axially extending male protrusion, and wherein the separator receiver is an axially extending female recess in an edge of one of the first and third portions. 
     
     
         3 . The control apparatus of  claim 1 , wherein the axially extending separator is a first separator, the control apparatus comprising a second axially extending separator disposed between the first and third portions. 
     
     
         4 . The control apparatus of  claim 1 , wherein the separator receiver is an axially extending female recess, and the axially extending separator is an axially extending male protrusion, the first portion rotationally indexable about the axis until the male protrusion aligns with and enters the female recess so that one of the first and third portions displaces towards the other of the first and third portions. 
     
     
         5 . The control apparatus of  claim 1 , wherein the first portion comprises a first end region including a plurality of first cam surfaces and an opposing second end region including a plurality of second cam surfaces, the first portion being rotationally indexable as a result of a pin structure engaging either of the plurality of first cam surfaces or the plurality of second cam surfaces. 
     
     
         6 . The control apparatus of  claim 1 , further comprising a radially extending pin carried on the second portion that engages the first portion and rotationally indexes the first portion about the axis. 
     
     
         7 . The control apparatus of  claim 1 , wherein the control apparatus is a sliding sleeve valve. 
     
     
         8 . The control apparatus of  claim 1 , wherein the annular seat structure is resiliently expandable from the first diameter to the second diameter. 
     
     
         9 . The control apparatus of  claim 8 , wherein the annular seat structure is of a circumferentially segmented construction. 
     
     
         10 . The control apparatus of  claim 9 , wherein, the annular seat structure includes a series of rigid circumferential segments carrying an elastomeric material resiliently biasing the annular seat structure radially inwardly toward the first diameter thereof. 
     
     
         11 . The control apparatus of  claim 1 , further comprising a first biasing element biasing the second portion in a first axial direction and a second biasing element biasing the third portion in an opposing axial direction. 
     
     
         12 . The control apparatus of  claim 1 , wherein the second biasing member comprises a pocket arranged to receive the annular seat structure when it expands to the second diameter. 
     
     
         13 . A control apparatus operably positionable in a wellbore, comprising:
 a tubular member extending along an axis;   an annular plug seat coaxially disposed within the tubular member and being diametrically expandable from a first diameter to a larger second diameter by a plug member passing axially therethrough in a downstream direction; and   a rotationally indexable counter apparatus functioning, during an operational cycle of the control apparatus, to limit to a predetermined number the number of times the annular plug seat can be diametrically expanded from the first diameter to the second diameter by plug members sequentially passing through the annular plug seat in the downstream direction, the rotationally indexable counter apparatus comprising
 a counting ring rotationally indexable about the axis, the counting ring having at least one cam surface therein for incrementally rotating the counting ring about the axis; 
 a locking ring separated from the counting ring by an axially extending male protrusion that separates and prevents the counting and locking rings from displacing toward each other, and 
 one of the counting and locking rings having an axially extending female recess formed therein that receives the axially extending male protrusion when the female recess aligns with the male protrusion in a manner permitting the counting and locking rings to displace towards each other and lock the annular plug seat at the first diameter. 
   
     
     
         14 . The control apparatus of  claim 13 , comprising an upper piston arranged to be axially displaced when the annular plug seat expands to the second diameter and to simultaneously rotate the counting ring. 
     
     
         15 . The control apparatus of  claim 14 , wherein the upper piston comprises a radially extending pin that engages the cam surface to incrementally rotate the counting ring about the axis. 
     
     
         16 . The control apparatus of  claim 14 , further comprising a first biasing element biasing the counting ring in a first axial direction and a second biasing element biasing the upper piston in an opposing axial direction. 
     
     
         17 . The control apparatus of  claim 13 , wherein the counting ring comprises a first end region including a plurality of first cam surfaces and an opposing second end region including a plurality of second cam surfaces, the counting being rotationally indexable as a result of pin structures alternatingly engaging both of the plurality of first cam surfaces and the plurality of second cam surfaces. 
     
     
         18 . A control apparatus operably positionable in a wellbore, comprising:
 a tubular member extending along an axis;   an annular plug seat coaxially disposed within the tubular member and being diametrically expandable from a first diameter to a larger second diameter by a plug member passing axially therethrough in a downstream direction; and   a rotationally indexable counter apparatus functioning to limit the number of times the annular plug seat can be diametrically expanded from the first diameter to the second diameter by plug members sequentially passing through the annular plug seat, the rotationally indexable counter apparatus comprising:
 a counting ring rotationally indexable about the axis; 
 a piston ring operative, in response to a diametric expansion of the annular seat structure to the second diameter, to engage and rotationally index the counting ring through a predetermined angle about the axis; 
 a first spring biasing the piston ring away from the counting ring; 
 a locking ring separated from the counting ring by an axially extending male protrusion that separates and prevents the counting and locking rings from displacing toward each other, one of the counting and locking rings having an axially extending female recess formed therein that receives the axially extending male protrusion when the female recess aligns with the male protrusion in a manner permitting the counting and locking rings to displace towards each other and lock the annular plug seat at the first diameter; and 
 a second spring biasing the locking ring toward the counting ring. 
   
     
     
         19 . The control apparatus of  claim 18 , comprising an upper piston arranged to be axially displaced when the annular plug seat expands to the second diameter and to simultaneously rotate the counting ring. 
     
     
         20 . The control apparatus of  claim 18 , wherein the upper piston comprises a radially extending pin that engages the cam surface to incrementally rotate the counting ring about the axis.