Indexing Sleeve for Single-Trip, Multi-Stage Fracing

CROSS-REFERENCE TO RELATED APPLICATION

0001This is a continuation-in-part of U.S. patent application Ser. No. 12/753,331, filed 2 Apr. 2010, to which priority is claimed and which is incorporated herein by reference in its entirety.

BACKGROUND

0002During frac operations, operators want to minimize the number of trips they need to run in a well while still being able to optimize the placement of stimulation treatments and the use of rig/frac equipment. Therefore, operators prefer to use a single-trip, multistage fracing system to selectively stimulate multiple stages, intervals, or zones of a well. Typically, this type of fracing systems has a series of open hole packers along a tubing string to isolate zones in the well. Interspersed between these packers, the system has frac sleeves along the tubing string. These sleeves are initially closed, but they can be opened to stimulate the various intervals in the well.

0003For example, the system is run in the well, and a setting ball is deployed to shift a wellbore isolation valve to positively seal off the tubing string. Operators then sequentially set the packers. Once all the packers are set, the wellbore isolation valve acts as a positive barrier to formation pressure.

0004Operators rig up fracing surface equipment and apply pressure to open a pressure sleeve on the end of the tubing string so the first zone is treated. At this point, operators then treat successive zones by dropping successively increasing sized balls sizes down the tubing string. Each ball opens a corresponding sleeve so fracture treatment can be accurately applied in each zone.

0005As is typical, the dropped balls engage respective seat sizes in the frac sleeves and create barriers to the zones below. Applied differential tubing pressure then shifts the sleeve open so that the treatment fluid can stimulate the adjacent zone. Some ball-actuated frac sleeves can be mechanically shifted back into the closed position. This gives the ability to isolate problematic sections where water influx or other unwanted egress can take place.

0006Because the zones are treated in stages, the smallest ball and ball seat are used for the lowermost sleeve, and successively higher sleeves have larger seats for larger balls. However, practical limitations restrict the number of balls that can be run in a single well. Because the balls must be sized to pass through the upper seats and only locate in the desired location, the balls must have enough difference in their sizes to pass through the upper seats.

0007To overcome difficulties with using different sized balls, some operators have used selective darts that use onboard intelligence to determine when the desired seat has been reached as the dart deploys downhole. An example of this is disclosed in U.S. Pat. No. 7,387,165. In other implementations, operators have used smart sleeves to control opening of the sleeves. An example of this is disclosed in U.S. Pat. No. 6,041,857. Even though such systems may be effective, operators are continually striving for new and useful ways to selectively open sliding sleeves downhole for frac operations or the like.

0008The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.

SUMMARY

0009Downhole flow tools or sliding sleeves deploy on a tubing string down a wellbore for a frac operation or the like. The tools have an insert and a sleeve that can move in the tool's bore. Various plugs, such as balls, frac darts, or the like, deploy down the tubing string to selectively isolate various zones of a formation for treatment.

0010In one arrangement, the insert moves by fluid pressure from a first port in the tool's housing. The insert defines a chamber with the tool's housing, and the first port communicates with this chamber. When the first port in the tool's housing is opened by an actuator, fluid pressure from the annulus enters this open first port and fills the chamber. In turn, the insert moves from a first position to a second position away from the sleeve by the piston action of the fluid pressure.

0011In another arrangement, the insert is biased by a spring from a first position to a second position. One or more pins or arms retain the biased insert in the first position. When the pins or arms are moved from the insert by an actuator, the spring moves the insert from the first position to the second position away from the sleeve.

0012For its part, the sleeve has a catch that can be used to move the sleeve. Initially, this catch is inactive when the insert is positioned toward the sleeve in the first position. Once the insert moves away due to filling of the chamber or bias of the spring by the actuator, however, the catch becomes active and can engage a plug deployed down the tubing string to the catch.

0013In one example, the catch is a profile defined around the inner passage of the sleeve. The insert initially conceals this profile until moved away by the actuator. Once the profile is exposed, biased dogs or keys on a dropped plug can engage the profile. Then, as the plug seals in the inner passage of the sleeve, fluid pressure pumped down the tubing string to the seated plug forces the sleeve to an open condition. At this point, outlet ports in the tool's housing permit fluid communication between the tool's bore and the surrounding annulus. In this way, frac fluid pumped down to the tool can stimulate an isolated interval of the wellbore formation.

0014A reverse arrangement for the catch can also be used. In this case, the sleeve in the tool has dogs or keys that are held in a retracted condition when the insert is positioned toward the sleeve. Once the insert moves away from the sleeve by the actuator, the dogs or keys extend outward into the interior passage of the sleeve. When a plug is then deployed down the tubing string, it will engage these extended keys or dogs, allowing the sleeve to be forced open by applied fluid pressure.

0015Regardless of the form of catch used, the indexing sleeve or tool has an actuator for activating when the insert moves away from the sleeve so the next dropped plug can be caught. In one arrangement, the actuator has a sensor, such as a hall effect sensor, and one or more flexure members or springs. When a plug passes through the tool, the flexure members trigger the sensor to count the passage of the plug. Control circuitry of the actuator uses a counter to count how many plugs have passed through the tool. Once the count reaches a preset number, the control circuitry activates a valve, which can be a solenoid valve or other mechanism. The valve can have a plunger or other form of closure for controlling fluid communication to move the insert. Alternatively, the valve can move a pin or arm to release the insert, which then moves by the bias of a spring.

0016The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> illustrates a tubing string having indexing sleeves according to the present disclosure.

<figref idref="DRAWINGS">FIG. 2</figref> illustrates an indexing sleeve according to the present disclosure in a closed condition.

<figref idref="DRAWINGS">FIG. 3</figref> diagrams portion of an actuator or controller for the indexing sleeve of <figref idref="DRAWINGS">FIG. 2</figref>.

<figref idref="DRAWINGS">FIG. 4</figref> shows a frac dart for use with the indexing sleeve of <figref idref="DRAWINGS">FIG. 2</figref>.

<figref idref="DRAWINGS">FIGS. 5A-5B</figref> illustrate another indexing sleeve according to the present disclosure in a closed condition.

<figref idref="DRAWINGS">FIG. 6</figref> shows a frac dart for use with the indexing sleeve of <figref idref="DRAWINGS">FIGS. 5A-5B</figref>.

<figref idref="DRAWINGS">FIGS. 7A-7C</figref> illustrate yet another indexing sleeve according to the present disclosure in a closed condition.

<figref idref="DRAWINGS">FIGS. 8A-8F</figref> show the indexing sleeve of <figref idref="DRAWINGS">FIGS. 7A-7C</figref> in various stages of operation.

<figref idref="DRAWINGS">FIGS. 9A-9B</figref> illustrate another catch arrangement for an indexing sleeve of the present disclosure.

<figref idref="DRAWINGS">FIG. 10</figref> illustrates a frac dart for the catch arrangement of <figref idref="DRAWINGS">FIG. 9A-9B</figref>.

<figref idref="DRAWINGS">FIGS. 11A-11D</figref> illustrate yet another catch arrangement for an indexing sleeve of the present disclosure.

<figref idref="DRAWINGS">FIGS. 12A-12B</figref> illustrates an indexing sleeve having an insert movable relative to ports and a catch in the bore.

DETAILED DESCRIPTION

0029A tubing string <b>12</b> shown in <figref idref="DRAWINGS">FIG. 1</figref> deploys in a wellbore <b>10</b>. The string <b>12</b> has flow tools or indexing sleeves <b>100</b>A-C disposed along its length. Various packers <b>40</b> isolate portions of the wellbore <b>10</b> into isolated zones. In general, the wellbore <b>10</b> can be an opened or cased hole, and the packers <b>40</b> can be any suitable type of packer intended to isolate portions of the wellbore into isolated zones.

0030The indexing sleeves <b>100</b>A-C deploy on the tubing string <b>12</b> between the packers <b>40</b> and can be used to divert treatment fluid selectively to the isolated zones of the surrounding formation. The tubing string <b>12</b> can be part of a frac assembly, for example, having a top liner packer (not shown), a wellbore isolation valve (not shown), and other packers and sleeves (not shown) in addition to those shown. If the wellbore <b>10</b> has casing, then the wellbore <b>10</b> can have casing perforations <b>14</b> at various points.

0031As conventionally done, operators deploy a setting ball to close the wellbore isolation valve (not shown). Then, operators rig up fracing surface equipment and pump fluid down the wellbore to open a pressure actuated sleeve (not shown) toward the end of the tubing string <b>12</b>. This treats a first zone of the formation. Then, in a later stage of the operation, operators selectively actuate the indexing sleeves <b>100</b>A-C between the packers <b>40</b> to treat the isolated zones depicted in <figref idref="DRAWINGS">FIG. 1</figref>.

0032The indexing sleeves <b>100</b>A-C have activatable catches (not shown) according to the present disclosure. Based on a specific number of plugs (i.e., darts, balls or the like) dropped down the tubing string <b>12</b>, internal components of a given indexing sleeve <b>100</b>A-C activate and engage the dropped plug. In this way, one sized plug can be dropped down the tubing string <b>12</b> to open the indexing sleeve <b>100</b>A-C selectively.

0033With a general understanding of how the indexing sleeves <b>100</b> are used, attention now turns to details of indexing sleeves <b>100</b> according to the present disclosure. Various indexing sleeves <b>100</b> are disclosed in co-pending application Ser. No. 12/753,331, which has been incorporated herein by reference.

0034One of these indexing sleeves <b>100</b> is illustrated in <figref idref="DRAWINGS">FIG. 2</figref>. The indexing sleeve <b>100</b> has a housing <b>110</b> defining a bore <b>102</b> therethrough and having ends <b>104</b>/<b>106</b> for coupling to a tubing string (not shown). Inside, the housing <b>110</b> has two inserts (i.e., insert <b>120</b> and sleeve <b>140</b>) disposed in its bore <b>102</b>. The insert <b>120</b> can move from a closed position (<figref idref="DRAWINGS">FIG. 2</figref>) to an open position (not shown) when an appropriate plug (e.g., dart <b>150</b> of <figref idref="DRAWINGS">FIG. 4</figref> or other form of plug) is passed through the indexing sleeve <b>100</b> as discussed in more detail below. Likewise, the sleeve <b>140</b> can move from a closed position (<figref idref="DRAWINGS">FIG. 2</figref>) to an opened position (not shown) when another appropriate plug (e.g. dart <b>150</b> or other form of plug) is passed later through the indexing sleeve <b>100</b> as also discussed in more detail below.

0035As shown in <figref idref="DRAWINGS">FIG. 2</figref>, the insert <b>120</b> in the closed condition covers a portion of the sleeve <b>140</b>. In turn, the sleeve <b>140</b> in the closed condition covers external ports <b>112</b> in the housing <b>110</b>, and peripheral seals <b>142</b> on the sleeve <b>140</b> prevent fluid communication between the bore <b>102</b> and these ports <b>112</b>. When the insert <b>120</b> has the open condition, the insert <b>120</b> is moved away from the sleeve <b>140</b> so that a profile <b>146</b> on the sleeve <b>140</b> is exposed in the housing's bore <b>102</b>. Finally, the sleeve <b>140</b> in the open position is moved away from the ports <b>112</b> so that fluid in the bore <b>102</b> can pass out through the ports <b>112</b> to the surrounding annulus and treat the adjacent formation.

0036Initially, an actuator or controller <b>130</b> having control circuitry <b>131</b> in the indexing sleeve <b>100</b> is programmed to allow a set number of plugs to pass through the indexing sleeve <b>100</b> before activation. Then, the indexing sleeve <b>100</b> runs downhole in the closed condition as shown in <figref idref="DRAWINGS">FIG. 2</figref>. To then begin a frac operation, operators drop a plug down the tubing string from the surface. This plug can be intended to close a wellbore isolation valve or open another indexing sleeve.

0037As shown in <figref idref="DRAWINGS">FIG. 4</figref>, one type of plug for use with the indexing sleeve is a frac dart <b>160</b> having an external seal <b>162</b> disposed thereabout for engaging in the sleeve (<b>140</b>). The dart <b>160</b> also has retractable X-type keys <b>166</b> (or other type of dog or key) that can retract and extend from the dart <b>160</b>. Finally, the dart <b>160</b> has a sensing element <b>164</b>. In one arrangement, this sensing element <b>164</b> is a magnetic strip or element disposed internally or externally on the dart <b>160</b>.

0038Once the dart <b>160</b> is dropped down the tubing string, the dart <b>160</b> eventually reaches the indexing sleeve <b>100</b> of <figref idref="DRAWINGS">FIG. 2</figref>. Because the insert <b>120</b> covers the profile <b>146</b> in the sleeve <b>140</b>, the dropped dart <b>160</b> cannot land in the sleeve's profile <b>146</b> and instead continues through most of the indexing sleeve <b>100</b>. Eventually, the sensing element <b>164</b> of the dart <b>160</b> meets up with a sensor <b>134</b> disposed in the housing's bore <b>102</b>.

0039Connected to a power source (e.g., battery) <b>132</b>, this sensor <b>134</b> communicates an electronic signal to the control circuitry <b>131</b> in response to the passing sensing element <b>164</b>. The control circuitry <b>131</b> can be on a circuit board housed in the indexing sleeve <b>100</b> or elsewhere. The signal indicates when the dart's sensing element <b>164</b> has met the sensor <b>134</b>. For its part, the sensor <b>134</b> can be a Hall Effect sensor or any other sensor triggered by magnetic interaction. Alternatively, the sensor <b>134</b> can be some other type of electronic device. In addition, the sensor <b>134</b> could be some form of mechanical or electro-mechanical switch, although an electronic sensor is preferred.

0040Using the sensor's signal, the control circuitry <b>131</b> counts, detects, or reads the passage of the sensing element <b>164</b> on the dart <b>160</b>, which continues down the tubing string (not shown). The process of dropping a dart <b>160</b> and counting its passage with the sensor <b>134</b> is then repeated for as many darts <b>160</b> the sleeve <b>100</b> is set to pass. Once the number of passing darts <b>160</b> is one less than the number set to open this indexing sleeve <b>100</b>, the control circuitry <b>131</b> activates a valve, motor, or the like <b>136</b> on the tool <b>100</b> when this second to last dart <b>160</b> has passed and generated a sensor signal. Once activated, the valve <b>136</b> moves a plunger <b>138</b> that opens a port <b>118</b> in the housing <b>110</b>. This communicates a first sealed chamber <b>116</b><i>a </i>between the insert <b>120</b> and the housing <b>110</b> with the surrounding annulus, which is at higher pressure.

0041Operation of the actuator or controller <b>130</b> in one implementation can be as follows. (For reference, <figref idref="DRAWINGS">FIG. 3</figref> shows the actuator or controller <b>130</b> for the disclosed indexing sleeve <b>100</b> in additional detail.) The sensor <b>134</b>, such as a Hall Effect sensor, responds to the sensing element or magnetic strip <b>162</b> of the dart <b>160</b> when it comes into proximity to the sensor <b>134</b>. In response, a counter <b>133</b> that is part of the control circuitry <b>131</b> counts the passage of the dart's element <b>162</b>. When a preset count has been reached, the counter <b>133</b> activates a switch <b>135</b>, and a power source <b>132</b> activates a solenoid valve <b>136</b>, which moves a plunger <b>138</b> to open the port <b>118</b>. Although a solenoid valve <b>136</b> can be used, any other mechanism or device capable of maintaining a port closed with a closure until activated can be used. Such a device can be activated electronically or mechanically. For example, a spring-biased plunger could be used to close off the port. A filament or other breakable component can hold this biased plunger in a closed state to close off the port. When activated, an electric current, heat, force or the like can break the filament or other component, allowing the plunger to open communication through the port. These and other types of valve mechanisms could be used.

0042Once the port <b>118</b> is opened on the indexing sleeve <b>100</b> of <figref idref="DRAWINGS">FIG. 2</figref>, surrounding fluid pressure from the annulus passes through the port <b>118</b> and fills the chamber <b>116</b><i>a</i>. An adjoining chamber <b>116</b><i>b </i>provided between the insert <b>120</b> and the housing <b>110</b> can be filled to atmospheric pressure. This chamber <b>116</b><i>b </i>can be readily compressed when the much higher fluid pressure from the annulus (at 5000 psi or the like) enters the first chamber <b>116</b><i>a. </i>

0043In response to the filling chamber <b>116</b><i>a</i>, the insert <b>120</b> shears free of shear pins <b>121</b> to the housing <b>120</b>. Now freed, the insert <b>120</b> moves (downward) in the housing's bore <b>102</b> by the piston effect of the filling chamber <b>116</b><i>a</i>. Once the insert <b>120</b> has completed its travel, its distal end exposes the profile <b>146</b> inside the sleeve <b>140</b>.

0044To now open this particular indexing sleeve <b>100</b>, operators drop the next frac dart <b>160</b>. This next dart <b>160</b> reaches the exposed profile <b>146</b> on the sleeve <b>140</b> in <figref idref="DRAWINGS">FIG. 2</figref>. The biased keys <b>166</b> on the dart <b>160</b> extend outward and engage or catch the profile <b>146</b>. The key <b>166</b> has a notch locking in the profile <b>146</b> in only a first direction tending to open the sleeve <b>120</b>. The rest of the key <b>166</b>, however, allows the dart <b>160</b> move in a second direction opposite to the first direction so it can be produced to the surface as discussed later.

0045The dart's seal <b>162</b> seals inside an interior passage or seat in the sleeve <b>140</b>. Because the dart <b>160</b> is passing through the sleeve <b>140</b>, interaction of the seal <b>164</b> with the surrounding sleeve <b>140</b> can tend to slow the dart's passage. This helps the keys <b>166</b> to catch in the exposed profile <b>146</b>.

0046Operators apply frac pressure down the tubing string, and the applied pressure shears the shear pins <b>141</b> holding the sleeve <b>140</b> in the housing <b>110</b>. Now freed, the applied pressure moves the sleeve <b>140</b> (downward) in the housing to expose the ports <b>112</b>. At this point, the frac operation can stimulate the adjacent zone of the formation.

0047Another indexing sleeve <b>100</b> shown in <figref idref="DRAWINGS">FIGS. 5A-5B</figref> has many of the same components as other sleeves disclosed herein so that like reference numbers are used for similar components. The indexing sleeve <b>100</b> has a housing <b>110</b> defining a bore <b>102</b> therethrough and having ends <b>104</b>/<b>106</b> for coupling to a tubing string (not shown). Inside, the housing <b>110</b> has two inserts (i.e., insert <b>120</b> and sleeve <b>140</b>) disposed in its bore <b>102</b>. The insert <b>120</b> can move from a closed position (<figref idref="DRAWINGS">FIG. 5A</figref>) to an open position (not shown) when an appropriate plug (e.g., ball, dart, or other form of plug) is passed through the indexing sleeve <b>100</b> as discussed in more detail below. Likewise, the sleeve <b>140</b> can move from a closed position (<figref idref="DRAWINGS">FIG. 5A</figref>) to an opened position (not shown) when another appropriate plug (e.g. ball, dart, or other form of plug) is passed later through the indexing sleeve <b>100</b> as also discussed in more detail below.

0048The indexing sleeve <b>100</b> is run in the hole in a closed condition. As shown in <figref idref="DRAWINGS">FIG. 5A</figref>, the insert <b>120</b> in the closed condition covers a portion of the sleeve <b>140</b>. In turn, the sleeve <b>140</b> in the closed condition covers external ports <b>112</b> in the housing <b>110</b>, and peripheral seals <b>142</b> on the sleeve <b>140</b> prevent fluid communication between the bore <b>102</b> and these ports <b>112</b>. When the insert <b>120</b> has the open condition, the insert <b>120</b> is moved away from the sleeve <b>140</b> so that a profile <b>146</b> on the sleeve <b>140</b> is exposed in the housing's bore <b>102</b>. Finally, the sleeve <b>140</b> in the open position is moved away from the ports <b>112</b> so that fluid in the bore <b>102</b> can pass out through the ports <b>112</b> to the surrounding annulus and treat the adjacent formation.

0049Initially, the actuator or controller <b>130</b> having the control circuitry <b>131</b> in the indexing sleeve <b>100</b> is programmed to allow a set number of plugs to pass through the indexing sleeve <b>100</b> before activation. Then, the indexing sleeve <b>100</b> runs downhole in the closed condition as shown in <figref idref="DRAWINGS">FIGS. 5A-5B</figref>. To then begin a frac operation, operators drop plugs down the tubing string from the surface.

0050As shown in <figref idref="DRAWINGS">FIG. 5A</figref>, a plug <b>170</b> is dropped down the tubing string, and the plug <b>170</b> eventually reaches the indexing sleeve <b>100</b>. (This plug <b>170</b> is shown as a ball, but can be another type of plug.) Because the insert <b>120</b> covers the profile <b>146</b> in the sleeve <b>140</b>, the dropped plug <b>170</b> cannot land in the sleeve's profile <b>146</b> and instead continues through most of the indexing sleeve <b>100</b>. Eventually, the plug <b>170</b> meets up with one or more flexure members <b>135</b> disposed in the housing's bore <b>102</b> as shown in <figref idref="DRAWINGS">FIG. 5B</figref>.

0051The one or more flexure members <b>135</b> can be bow springs or leaf springs disposed around the perimeter of the inside bore <b>112</b>. In one arrangement, as many as six springs <b>135</b> may be used. Each spring <b>135</b> is designed to support a portion of the kinetic energy of the plug <b>170</b> as it is pumped through the indexing sleeve <b>100</b>. The force required to pump the plug <b>170</b> past the springs <b>135</b> can be about 1500-psi, which is observable from the surface during the pumping operations.

0052Any number of springs <b>135</b> can be used and can be uniformly arranged around the bore <b>112</b>. The bias of the springs <b>135</b> can be configured for a particular implementation, expected pressures, expected number of plugs to pass, and other pertinent variables. The springs <b>135</b> are robust enough to provide a surface indication, but they are preferably not prone to stick due to the presence of frac proppant materials.

0053The sensor <b>134</b> is connected to a power source (e.g., battery) <b>132</b>. When the plug <b>150</b> engages the springs <b>135</b>, forced pumping of the plug <b>170</b> down the sleeve <b>100</b> causes the plug <b>150</b> to flex or extend the springs <b>135</b>. As the springs are flexed or extended due to the plug's passage, the springs <b>135</b> elongate. At full extension, ends of the springs <b>135</b> engage the sensor <b>134</b> in the bore <b>112</b>, and the presence of the tip of the spring <b>135</b> near the sensor <b>134</b> indicates passage of a plug.

0054The sensor <b>134</b> communicates an electronic signal to the control circuitry <b>131</b> of the actuator or controller <b>130</b> in response to the spring contact. (The indexing sleeve of <figref idref="DRAWINGS">FIGS. 5A-5B</figref> can use an actuator <b>130</b> similar to that disclosed previously in <figref idref="DRAWINGS">FIG. 3</figref>.) The control circuitry <b>131</b> can be on a circuit board housed in the indexing sleeve <b>100</b> or elsewhere. The signal indicates when the plug <b>170</b> has moved into or past the springs <b>135</b>. For its part, the sensor <b>134</b> can be a Hall Effect sensor or any other sensor triggered by interaction with the spring <b>135</b>. Alternatively, the sensor <b>134</b> can be some other type of electronic device. In addition, the sensor <b>134</b> could be some form of mechanical or electro-mechanical switch, although an electronic sensor is preferred.

0055Using the sensor's signal, the control circuitry <b>131</b> counts, detects, or reads the passage of the plug <b>170</b>, which continues down the tubing string (not shown). The process of dropping a plug <b>170</b> and counting its passage with the sensor <b>134</b> is then repeated for as many plugs <b>170</b> the sleeve <b>100</b> is set to pass. Once the number of passing plugs <b>170</b> is one less than the number set to open this indexing sleeve <b>100</b>, the control circuitry <b>131</b> activates a valve <b>136</b> on the sleeve <b>100</b> when this second to last plug <b>170</b> has passed and generated a sensor signal.

0056Once activated, the valve <b>136</b> moves a plunger <b>168</b> that opens a port <b>118</b>, and the filling chamber <b>116</b><i>a </i>shears the insert <b>120</b> free of shear pins <b>121</b> to the housing <b>120</b>. Now freed, the insert <b>120</b> moves (downward) in the housing's bore <b>102</b> by the piston effect. Once the insert <b>120</b> has completed its travel, its distal end exposes the profile <b>146</b> inside the sleeve <b>140</b>. To now open this particular indexing sleeve <b>100</b>, operators drop the next plug, which can be a frac dart <b>180</b> as in <figref idref="DRAWINGS">FIG. 6</figref>.

0057As shown in <figref idref="DRAWINGS">FIG. 6</figref>, the plug that can be used to index and open the sleeve can be a frac dart <b>180</b>. This frac dart <b>180</b> is similar to that described previously. The dart <b>180</b> has an external seal <b>182</b> disposed thereabout for engaging in the sleeve (<b>140</b>). The dart <b>180</b> also has retractable X-type keys <b>186</b> (or other type of dog or key) that can retract and extend from the dart <b>180</b>. Unlike the previous frac dart, this frac dart <b>180</b> can lack a sensing element because interaction of the frac dart <b>180</b> with the springs (<b>135</b>) on the indexing sleeve (<b>100</b>) indicates passage of the dart <b>180</b>.

0058<figref idref="DRAWINGS">FIGS. 7A-7C</figref> illustrate another indexing sleeve <b>100</b> according to the present disclosure in a closed condition. The indexing sleeve <b>100</b> is similar to that described previously so that the same reference numbers are used for like components. As before, the indexing sleeve <b>100</b> runs in the hole in a closed condition, and the insert <b>120</b> covers a portion of the sleeve <b>140</b>. In turn, the sleeve <b>140</b> covers external ports <b>112</b> in the housing <b>110</b>.

0059A dropped plug <b>170</b> down the tubing string from the surface eventually engages the springs <b>135</b> as shown in <figref idref="DRAWINGS">FIG. 7B</figref>. The sensor <b>134</b> detects the interaction of the end of the flexure members or springs <b>135</b>, and the control circuitry <b>131</b> of the actuator <b>130</b> counts the passage of the plug <b>170</b>. The process of dropping a plug <b>170</b> and counting its passage with the sensor <b>134</b> is then repeated for as many plugs <b>170</b> the sleeve <b>100</b> is set to pass.

0060Once the number of passing plugs <b>170</b> is one less than the number set to open this indexing sleeve <b>100</b>, the control circuitry <b>131</b> activates a valve, motor, or the like <b>136</b> on the sleeve <b>100</b> when this second to last plug <b>170</b> has passed and generated a sensor signal. Once activated, the valve <b>136</b> moves an arm or pin <b>139</b> restraining the insert <b>120</b>. Once the insert <b>120</b> is unrestrained, a spring <b>125</b> biases the insert <b>120</b> in the bore <b>112</b> away from the sleeve <b>140</b> to expose the profile <b>146</b> in the sleeve <b>140</b>. Further details of this operation are discussed below. Subsequently, when a frac dart is pumped downhole, the frac dart locates on the profile <b>146</b> of the sleeve <b>140</b> so that frac operations can proceed.

0061<figref idref="DRAWINGS">FIGS. 8A-8F</figref> show the indexing sleeve <b>100</b> of <figref idref="DRAWINGS">FIGS. 7A-7C</figref> in various stages of operation. Many of the same operational steps would apply to the other indexing sleeves disclosed herein. As shown in <figref idref="DRAWINGS">FIG. 8A</figref>, the indexing sleeve <b>100</b> deploys downhole in a closed condition with the sleeve <b>140</b> covering the port <b>112</b> and with the insert <b>120</b> covering the profile <b>146</b> on the sleeve <b>140</b>. A dropped plug <b>170</b> can pass through the indexing sleeve <b>100</b>.

0062As shown in <figref idref="DRAWINGS">FIG. 8B</figref>, the dropped plug <b>170</b> engages the springs <b>135</b>, and the sensor <b>134</b> and control circuitry <b>131</b> detects and counts the passage of the plug <b>170</b>. This process of dropped plugs <b>170</b> and counting is repeated until the preset number of plugs <b>170</b> has passed through the indexing sleeve <b>100</b>. At this point shown in <figref idref="DRAWINGS">FIG. 8C</figref>, the control circuitry <b>131</b> activates the valve <b>136</b>, which removes the restraining arm or pin <b>139</b> from the insert <b>120</b>. Now free, the insert <b>120</b> moves by the bias of the spring <b>125</b> way from the sleeve <b>140</b>, thereby exposing the sleeve's profile <b>146</b>.

0063As shown in <figref idref="DRAWINGS">FIG. 8D</figref>, another plug is next dropped down the tubing. In this instance, the plug is a frac dart <b>180</b> similar to that described previously with reference to <figref idref="DRAWINGS">FIG. 6</figref>. The dart <b>180</b> reaches the exposed profile <b>146</b> on the sleeve <b>140</b>. The biased keys <b>186</b> on the dart <b>180</b> extend outward and engage or catch the profile <b>146</b>. The keys <b>156</b> have a notch locking in the profile <b>146</b> in only a first direction tending to open the sleeve <b>140</b>. The rest of the key <b>186</b>, however, allows the dart <b>180</b> move in a second direction opposite to the first direction so it can be produced to the surface as discussed later.

0064The dart's seal <b>182</b> seals inside an interior passage or seat in the sleeve <b>140</b>. Because the dart <b>180</b> is passing through the sleeve <b>140</b>, interaction of the seal <b>182</b> with the surrounding sleeve <b>140</b> can tend to slow the dart's passage. This helps the keys <b>186</b> to catch in the exposed profile <b>146</b>.

0065Operators apply frac pressure down the tubing string, and the applied pressure shears the shear pins <b>141</b> holding the sleeve <b>140</b> in the housing <b>110</b>. Now freed, the applied pressure moves the sleeve <b>140</b> (downward) in the housing to expose the ports <b>112</b>, as shown in <figref idref="DRAWINGS">FIG. 8D</figref>. At this point, the frac operation can stimulate the adjacent zone of the formation.

0066After the zones having been stimulated, operators open the well to production by opening any downhole control valve or the like. Because the dart <b>180</b> has a particular specific gravity (e.g., about 1.4 or so), production fluid coming up the tubing and housing bore <b>102</b> as shown in <figref idref="DRAWINGS">FIG. 8E</figref> brings the dart <b>180</b> back to the surface. If for any reason, the dart <b>180</b> does not come to the surface, then the dart <b>180</b> can be milled. Finally, as shown in <figref idref="DRAWINGS">FIG. 8F</figref>, the well can be produced through the open sleeve <b>100</b> without restriction or intervention. At any point, the indexing sleeve <b>100</b> can be manually reset closed by using an appropriate tool.

0067As disclosed above, energizing the insert <b>120</b> in the indexing sleeve <b>100</b> can use a number of arrangements. In <figref idref="DRAWINGS">FIGS. 5A-5B</figref>, the actuator <b>130</b> uses a piston effect as a chamber fills with pressure and moves the insert <b>120</b>. In <figref idref="DRAWINGS">FIGS. 7A-7C</figref>, the actuator <b>130</b> uses a solenoid and pin arrangement to release the sleeve <b>120</b> biased by the spring <b>122</b>. Other ways to energize the insert <b>120</b> can be used, including, hydrostatic chambers, motors, and the like. In addition, a solder plug could be melted to allow movement between two axial members. These and other arrangements can be used.

0068The previous indexing sleeves <b>100</b> of <figref idref="DRAWINGS">FIGS. 2</figref>, <b>5</b>A-<b>5</b>C, and <b>7</b>A-<b>7</b>C used profiles <b>146</b> on the sleeves <b>140</b>, while the frac darts <b>160</b>/<b>180</b> of <figref idref="DRAWINGS">FIGS. 3 and 6</figref> used biased keys <b>186</b> to catch on the profiles <b>146</b> when exposed. A reverse arrangement can be used. As shown in <figref idref="DRAWINGS">FIG. 9A</figref>, an indexing sleeve <b>100</b> has many of the same components as the previous embodiments so that like reference numerals are used. The sleeve <b>140</b>, however, has a plurality of keys or dogs <b>148</b> disposed in surrounding slots in the sleeve <b>140</b>. Springs or other biasing members <b>149</b> bias these dogs <b>148</b> through these slots toward the interior of the sleeve <b>140</b> where a frac plug passes.

0069Initially, these keys <b>148</b> remain retracted in the sleeve <b>140</b> so that plugs or frac darts can pass as desired. However, once the insert <b>120</b> has been activated by one of the darts or other plugs and has moved (downward) in the indexing sleeve <b>100</b>, the insert's distal end <b>122</b> disengages from the keys <b>148</b>. This allows the springs <b>149</b> to bias the keys <b>148</b> outward into the bore <b>102</b> of the sleeve <b>100</b>. At this point, the next frac dart <b>190</b> of <figref idref="DRAWINGS">FIG. 10</figref> will engage the keys <b>148</b>.

0070For example, <figref idref="DRAWINGS">FIG. 10</figref> shows a frac dart <b>190</b> having a seal <b>192</b> and a profile <b>196</b>. As shown in <figref idref="DRAWINGS">FIG. 9B</figref>, the dart <b>190</b> meets up to the sleeve <b>140</b>, and the extended keys <b>148</b> catch in the dart's exposed profile <b>196</b>. At this stage, fluid pressure applied against the caught dart <b>190</b> can move the sleeve <b>140</b> (downward) in the indexing sleeve <b>100</b> to open the housing's ports <b>112</b>.

0071The previous indexing sleeves <b>100</b> and darts <b>160</b>/<b>180</b>/<b>190</b> have keys and profiles for engagement inside the indexing sleeves <b>100</b>. As an alternative, an indexing sleeve <b>100</b> shown in <figref idref="DRAWINGS">FIG. 11A-11D</figref> uses a plug in the form of a ball <b>170</b> for engagement inside the indexing sleeve <b>100</b>. Again, this indexing sleeve <b>100</b> has many of the same components as the previous embodiment so that like reference numerals are used. Additionally, the sleeve <b>140</b> has a plurality of keys or dogs <b>148</b> disposed in surrounding slots in the sleeve <b>140</b>. Springs or other biasing members <b>149</b> bias these dogs <b>148</b> through these slots toward the interior of the sleeve <b>140</b>.

0072Initially, the keys <b>148</b> remain retracted as shown in <figref idref="DRAWINGS">FIG. 11A-11B</figref>. Once the insert <b>120</b> has been activated as shown in <figref idref="DRAWINGS">FIG. 11C-11D</figref>, the insert's distal end <b>124</b> disengages from the keys <b>148</b>. Rather than catching internal ledges on the keys <b>148</b> as in the previous embodiment, the distal end <b>124</b> shown in <figref idref="DRAWINGS">FIGS. 11A-11B</figref> initially covers the keys <b>148</b> and exposes them once the insert <b>120</b> moves as shown in <figref idref="DRAWINGS">FIGS. 11C-11D</figref>.

0073Either way, the springs <b>149</b> bias the keys <b>148</b> outward into the bore <b>102</b>. At this point, the next ball <b>170</b> will engage the extended keys <b>148</b>. For example, the end-section in <figref idref="DRAWINGS">FIG. 11B</figref> shows how the distal end <b>124</b> of the insert <b>120</b> can hold the keys <b>148</b> retracted in the sleeve <b>140</b>, allowing for passage of balls <b>170</b> through the larger diameter D. By contrast, the end-section in <figref idref="DRAWINGS">FIG. 11D</figref> shows how the extend keys <b>148</b> create a seat with a restricted diameter d to catch a ball <b>170</b>.

0074As shown, four such keys <b>148</b> can be used, although any suitable number could be used. As also shown, the proximate ends of the keys <b>148</b> can have shoulders to catch inside the sleeve's slots to prevent the keys <b>148</b> from passing out of these slots. In general, the keys <b>148</b> when extended can be configured to have ⅛-inch interference fit to engage a corresponding plug (e.g., ball <b>170</b>). However, the tolerance can depend on a number of factors.

0075When the dropped ball <b>170</b> reaches the extended keys <b>148</b> as in <figref idref="DRAWINGS">FIGS. 11C-11D</figref>, fluid pressure pumped down through the sleeve's bore <b>102</b> forces against the obstructing ball <b>170</b>. Eventually, the force releases the sleeve <b>140</b> from the pins <b>141</b> that initially hold it in its closed condition.

0076As disclosed herein, the indexing sleeve <b>100</b> can have two inserts (e.g., insert <b>120</b> and sleeve <b>140</b>). The sleeve <b>140</b> has a catch <b>146</b> and can move relative to ports <b>112</b> to allow fluid communication between the sleeve's bore <b>102</b> and the annulus. Because the insert <b>120</b> moves in the housing <b>110</b> by the actuator <b>130</b>, the insert <b>120</b> may instead cover a port in the housing <b>110</b> for fluid communication. Thus, once the insert <b>120</b> is moved, the indexing sleeve <b>100</b> can be opened.

0077As shown in <figref idref="DRAWINGS">FIGS. 12A-12B</figref>, another indexing sleeve <b>100</b> has a housing <b>110</b>, ports <b>112</b>, an insert <b>120</b>, and other components similar to those disclosed previously. This indexing sleeve <b>100</b> lacks a second insert or sleeve (e.g., <b>140</b>) as in previous embodiments. Instead, the catch (i.e., profile <b>126</b> or other locking shoulder) is defined in the bore <b>102</b> of the housing <b>110</b>.

0078A passing dart <b>180</b> or other plug interacts with the spring <b>135</b> and sensor arrangement <b>134</b> or other components of the actuator <b>130</b>, which moves the insert <b>120</b> as discussed previous. When the insert <b>120</b> is moved by the actuator <b>130</b>, it reveals the ports <b>112</b> in the housing <b>110</b> as shown in <figref idref="DRAWINGS">FIG. 12B</figref> so that the bore <b>102</b> communicates with the annulus. At the same time, movement of the insert <b>120</b> exposes this fixed catch <b>126</b>. In this way, the next dropped dart <b>180</b> or plug can engage the catch <b>126</b> in the bore <b>102</b> to close off the lower portion of the tubing string. Depending on the implementation and how various zones of a formation are to be treated, using this form of indexing sleeve <b>100</b> may be advantageous for operators.

0079The indexing sleeves and plugs disclosed herein can be used in conjunction with or substituted for the other indexing sleeves, plugs, and arrangements disclosed in co-pending application Ser. No. 12/753,331, which has been incorporated herein by reference.

0080The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. As described above, a plug can be a dart, a ball, or any other comparable item for dropping down a tubing string and landing in a sliding sleeve. Accordingly, plug, dart, ball, or other such term can be used interchangeably herein when referring to such items. As disclosed herein, the various indexing sleeves disclosed herein can be arranged with one another and with other sliding sleeves. It is possible, therefore, for one type of indexing sleeve and plug to be incorporated into a tubing string having another type of indexing sleeve and plug disclosed herein. These and other combinations and arrangements can be used in accordance with the present disclosure.

0081In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.