Indexing Sleeve for Single-Trip, Multi-Stage Fracing

BACKGROUND

p-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.

p-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.

p-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.

p-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.

p-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 size to pass through the upper seats.

p-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.

p-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

p-0009Downhole flow tools or sliding sleeves deploy on a tubing string down a wellbore for a frac operation or the like. In one arrangement, the sliding sleeves have first and second inserts that can move in the sleeve's bore. The first insert moves by fluid pressure from a first port in the sleeve's housing. In one arrangement, the first insert defines a chamber with the sleeve's housing, and the first port communicates with this chamber. When the first port in the sleeve's housing is opened, fluid pressure from the annulus enters this open first port and fills the chamber. In turn, the first insert moves away from the second insert by the piston action of the fluid pressure.

p-0010The second insert has a catch that can be used to move the second insert. Initially, this catch is inactive when the first insert is positioned toward the second insert. Once the first insert moves away due to filing of the chamber, however, the catch becomes active and can engage a plug deployed down the tubing string to the catch.

p-0011In one example, the catch is a profile defined around the inner passage of the second insert. The first insert initially conceals this profile until moved away by pressure in the chamber. 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 second insert, fluid pressure pumped down the tubing string to the seated plug forces the second insert to an open condition. At this point, additional ports in the sleeve's housing permit fluid communication between the sleeve's bore and the surrounding annulus. In this way, frac fluid pumped down to the sleeve can stimulate an isolated interval of the wellbore formation.

p-0012A reverse arrangement for the catch can also be used. In this case, the second insert has dogs or keys that are held in a retracted condition when the first insert is positioned toward the second insert. Once the first insert moves away, the dogs or keys extend outward into the interior passage of the second insert. When a plug is then deployed down the tubing string, it will engage these extended keys or dogs, allowing the second insert to be forced open by applied fluid pressure.

p-0013Regardless of the form of catch used, the sliding sleeves have a controller for activating when the first insert moves away from the second insert so the next dropped plug can be caught. The controller has a sensor, such as a hall effect sensor, that detects passage of a magnetic element on the plugs passing through the sliding sleeve.

p-0014In one arrangement, control circuitry of the controller uses a counter to count how many plugs have passed through the closed sleeve. Once the count reaches a preset number, the control circuitry activates a valve disposed on the sleeve. This valve can be a solenoid valve or other mechanism and can have a plunger or other form of closure for controlling communication through the housing's chamber port.

p-0015When the valve opens the port, fluid pressure from the surrounding annulus fills the chamber between the first insert and the sleeve's housing. This causes the first insert to move in the sleeve and away from the second insert so the catch can be activated. The sliding sleeve is now set to catch the next dropped ball so the sleeve can be opened and fluid can be diverted to the adjacent interval.

p-0016In another arrangement, control circuitry of the controller uses a timer in addition to or instead of the counter. The timer is set for a particular time interval. The timer can be activated when one or some preset number of plugs have passed through the sleeve. In any event, once the timer reaches its present time interval, the control circuitry activates the valve disposed on the sleeve as before so fluid in the surrounding annulus can fill the chamber and move the first insert away from the catch of the second insert.

p-0017When a timer is used, the sliding sleeve can be beneficially used in conjunction with sleeves having conventional seats. When a first plug is passed through one or more sliding sleeves and lands on the conventional seat of a sleeve, the first plug can activate the timers of the one or more other sliding sleeves up hole on the tubing string. These timers can be set to go off in successive sequence up the tubing string. In this way, once the timer on one of these sleeves activates the sleeve's catch. A second plug having the same size as the first can be deployed to this activated sleeve so a new interval can be treated. Therefore, multiple intervals of a formation can be treated sequentially up the tubing string uses plugs having the same size.

p-0018The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

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

<figref idrefs="DRAWINGS">FIGS. 2A-2B</figref> illustrate an indexing sleeve according to the present disclosure in a closed condition.

<figref idrefs="DRAWINGS">FIG. 2C</figref> diagrams a controller for the indexing sleeve of <figref idrefs="DRAWINGS">FIG. 2A</figref>.

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

<figref idrefs="DRAWINGS">FIGS. 3A-3F</figref> show the indexing sleeve in various stages of operation.

<figref idrefs="DRAWINGS">FIGS. 4A-4C</figref> schematically illustrate an arrangement of indexing sleeves in various stages of operation.

<figref idrefs="DRAWINGS">FIG. 5A</figref> illustrates another indexing sleeve according to the present disclosure in a closed condition.

<figref idrefs="DRAWINGS">FIG. 5B</figref> shows the indexing sleeve of <figref idrefs="DRAWINGS">FIG. 5A</figref> during opening.

<figref idrefs="DRAWINGS">FIG. 5C</figref> shows a frac dart for use with the sleeve of <figref idrefs="DRAWINGS">FIG. 5A</figref>.

<figref idrefs="DRAWINGS">FIG. 6A</figref> illustrates yet another indexing sleeve according to the present disclosure in a closed condition.

<figref idrefs="DRAWINGS">FIGS. 6B-6C</figref> shows lateral cross-sections of the indexing sleeve of <figref idrefs="DRAWINGS">FIG. 6A</figref>.

<figref idrefs="DRAWINGS">FIG. 6D</figref> shows the indexing sleeve of <figref idrefs="DRAWINGS">FIG. 6A</figref> during a stage of closing.

<figref idrefs="DRAWINGS">FIG. 7</figref> illustrates yet another indexing sleeve according to the present disclosure in a closed condition.

<figref idrefs="DRAWINGS">FIG. 8</figref> shows an isolation sleeve according in an opened condition.

<figref idrefs="DRAWINGS">FIGS. 9A-9B</figref> schematically illustrate an arrangement of sleeves in various stages of operation.

DETAILED DESCRIPTION

p-0034A tubing string <b>12</b> shown in <figref idrefs="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.

p-0035The 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.

p-0036As 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 idrefs="DRAWINGS">FIG. 1</figref>.

p-0037The 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 other 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.

p-0038With a general understanding of how the indexing sleeves <b>100</b>A-C are used, attention now turns to details of an indexing sleeve <b>100</b> shown in <figref idrefs="DRAWINGS">FIGS. 2A-2C</figref> and <figref idrefs="DRAWINGS">FIGS. 3A-3F</figref>.

p-0039As best shown in <figref idrefs="DRAWINGS">FIG. 2A</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 idrefs="DRAWINGS">FIG. 2A</figref>) to an open position (<figref idrefs="DRAWINGS">FIG. 3C</figref>) when an appropriate plug (e.g., dart <b>150</b> of <figref idrefs="DRAWINGS">FIG. 2D</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 idrefs="DRAWINGS">FIG. 2A</figref>) to an opened position (<figref idrefs="DRAWINGS">FIG. 3D</figref>) 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.

p-0040The indexing sleeve <b>100</b> is run in the hole in a closed condition. As shown in <figref idrefs="DRAWINGS">FIG. 2A</figref>, 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>, and peripheral seals <b>142</b>/<b>144</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 (<figref idrefs="DRAWINGS">FIG. 3C</figref>), 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 (<figref idrefs="DRAWINGS">FIG. 3D</figref>) 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.

p-0041Initially, control circuitry <b>130</b> in the indexing sleeve <b>100</b> is programmed to allow a set number of frac darts <b>150</b> 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 idrefs="DRAWINGS">FIGS. 2A and 3A</figref>. To then begin a frac operation, operators drop a frac dart <b>150</b> down the tubing string from the surface.

p-0042As shown in <figref idrefs="DRAWINGS">FIG. 2D</figref>, the dart <b>150</b> has an external seal <b>152</b> disposed thereabout for engaging in the sleeve (<b>140</b>). The dart <b>150</b> also has retractable X-type keys <b>156</b> (or other type of dog or key) that can retract and extend from the dart <b>150</b>. Finally, the dart <b>150</b> has a sensing element <b>154</b>. In one arrangement, this sensing element <b>154</b> is a magnetic strip or element disposed internally or externally on the dart <b>150</b>.

p-0043Once the dart <b>150</b> is dropped down the tubing string, the dart <b>150</b> eventually reaches the indexing sleeve <b>100</b> as shown in <figref idrefs="DRAWINGS">FIG. 3B</figref>. Because the insert <b>120</b> covers the profile <b>146</b> in the sleeve <b>140</b>, the dropped dart <b>150</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>154</b> of the dart <b>150</b> meets up with a sensor <b>134</b> disposed in the housing's bore <b>102</b>.

p-0044Connected to a power source (e.g., battery) <b>132</b>, this sensor <b>134</b> communicates an electronic signal to control circuitry <b>130</b> in response to the passing sensing element <b>154</b>. The control circuitry <b>130</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>154</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. Also, the sensor <b>134</b> could be some form of mechanical or electro-mechanical switch, although an electronic sensor is preferred.

p-0045Using the sensor's signal, the control circuitry <b>130</b> counts, detects, or reads the passage of the sensing element <b>154</b> on the dart <b>150</b>, which continues down the tubing string (not shown). The process of dropping a dart <b>150</b> and counting its passage with the sensor <b>134</b> is then repeated for as many darts <b>150</b> the sleeve <b>100</b> is set to pass. Once the number of passing darts <b>150</b> is one less than the number set to open this indexing sleeve <b>100</b>, the control circuitry <b>130</b> activates a valve <b>136</b> on the sleeve <b>150</b> when this second to last dart <b>150</b> has passed and generated a sensor signal. Once activated, the valve <b>136</b> moves a plunger <b>168</b> that opens a port <b>118</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.

p-0046<figref idrefs="DRAWINGS">FIG. 2C</figref> shows an example of a controller <b>160</b> for the disclosed indexing sleeve <b>100</b>. A hall effect sensor <b>162</b> responds to the magnetic strip (<b>152</b>) of the dart (<b>150</b>), and a counter <b>164</b> counts the passage of the dart's strip (<b>152</b>). When a present count has been reached, the counter <b>164</b> activates a switch <b>165</b>, and a power source <b>166</b> activates a solenoid valve <b>168</b>, which moves a plunger (<b>138</b>) to open the port (<b>118</b>). Although a solenoid valve <b>168</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 electronically or mechanically activated. 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.

p-0047Once the port <b>118</b> is opened as shown in <figref idrefs="DRAWINGS">FIG. 3C</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>

p-0048In 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> as also shown in <figref idrefs="DRAWINGS">FIG. 3C</figref>.

p-0049To now open this particular indexing sleeve <b>100</b>, operators drop the next frac dart <b>150</b>. As shown in <figref idrefs="DRAWINGS">FIG. 3D</figref>, this dart <b>150</b> reaches the exposed profile <b>146</b> on the sleeve <b>140</b>. The biased keys <b>156</b> on the dart <b>150</b> extend outward and engage or catch the profile <b>146</b>. The key <b>156</b> has a notch locking in the profile <b>146</b> in only a first direction tending to open the second insert. The rest of the key <b>156</b>, however, allows the dart <b>150</b> move in a second direction opposite to the first direction so it can be produced to the surface as discussed later.

p-0050The dart's seal <b>152</b> seals inside an interior passage or seat in the sleeve <b>140</b>. Because the dart <b>150</b> is passing through the sleeve <b>140</b>, interaction of the seal <b>154</b> with the surrounding sleeve <b>140</b> can tend to slow the dart's passage. This helps the keys <b>156</b> to catch in the exposed profile <b>146</b>.

p-0051Operators apply frac pressure down the tubing string <b>120</b>, 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 idrefs="DRAWINGS">FIG. 3D</figref>. At this point, the frac operation can stimulated the adjacent zone of the formation.

p-0052After all of the zones having been stimulated, operators open the well to production by opening any downhole control valve or the like. Because the darts <b>150</b> have a particular specific gravity (e.g., about 1.4 or so), production fluid communing up the tubing and housing bore <b>102</b> as shown in <figref idrefs="DRAWINGS">FIG. 3E</figref> brings the dart <b>150</b> back to the surface. If for any reason, one or more of the darts <b>150</b> do not come to the surface, then these remaining darts <b>150</b> can be milled. Finally, as shown in <figref idrefs="DRAWINGS">FIG. 3F</figref>, the well can be produced through the open sleeve <b>100</b> without restriction or intervention. At any point, the indexing sleeve can be manually reset closed by using an appropriate tool.

p-0053To help show how particular indexing sleeves <b>100</b> can be selectively opened, <figref idrefs="DRAWINGS">FIGS. 4A-4C</figref> show an arrangement of indexing sleeves <b>100</b>B-F in various stages of operation. As shown in <figref idrefs="DRAWINGS">FIG. 4A</figref>, a first dart <b>150</b>A has been dropped down the tubing string <b>12</b>, and it has passed through each of the indexing sleeves <b>100</b>B-F, increasing their counts. The lowermost indexing sleeve <b>100</b>B being set to one count activates so that its insert <b>120</b> moves by fluid pressure entering from side port <b>118</b>.

p-0054When the next dart <b>150</b>B is dropped as shown in <figref idrefs="DRAWINGS">FIG. 4B</figref>, it passes through each sleeve <b>100</b>C-F and engages in the exposed profile <b>146</b> of the lowermost sleeve <b>100</b>B. After the dart <b>150</b> passes the second-to-last indexing sleeve <b>100</b>C, its insert <b>120</b> activates and moves to expose its sleeve <b>140</b>'s profile. Eventually, the dart <b>150</b>B seats in the lowermost sleeve <b>150</b>B. Frac fluid pumped down the tubing string <b>12</b> can then exit the sleeve <b>100</b>B and stimulate the surrounding interval.

p-0055After facing, the next dart <b>150</b>C drops down the tubing sting and adds to the count of each sleeve <b>100</b>D-F. Eventually, this dart <b>150</b>C activates the third sleeve <b>100</b>D when passing as shown in <figref idrefs="DRAWINGS">FIG. 4B</figref>. Finally, this dart <b>150</b>C lands in the second sleeve <b>100</b>C as shown in <figref idrefs="DRAWINGS">FIG. 4C</figref> so that fracing can be performed and the next dart <b>150</b>D dropped. This operation continues up the tubing string <b>12</b>. Each deployed dart <b>150</b> can have the same diameter, and each indexing sleeve <b>100</b> can be set to ever-increasing counts of passing darts <b>150</b>.

p-0056The previous indexing sleeve <b>100</b> of <figref idrefs="DRAWINGS">FIG. 2A</figref> uses a profile <b>146</b> on its sleeve <b>140</b>, while the dart <b>150</b> of <figref idrefs="DRAWINGS">FIG. 2D</figref> uses biased keys <b>156</b> to catch on the profile <b>146</b> when exposed. A reverse arrangement can be used. As shown in <figref idrefs="DRAWINGS">FIG. 5A</figref>, an indexing sleeve <b>100</b> has many of the same components as the previous embodiment 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.

p-0057Initially, these keys <b>148</b> remain retracted in the sleeve <b>140</b> so that frac darts <b>150</b> can pass as desired. However, once the insert <b>120</b> has been activated by one of the darts <b>150</b> and has moved (downward) in the sleeve <b>100</b>, the insert's distal end <b>125</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 dart <b>150</b> will engage the keys <b>148</b>.

p-0058For example, <figref idrefs="DRAWINGS">FIG. 5C</figref> shows a dart <b>150</b> having a magnetic strip <b>152</b>, seal <b>154</b>, and profile <b>158</b>. As shown in <figref idrefs="DRAWINGS">FIG. 5B</figref>, the dart <b>150</b> meets up to the sleeve <b>140</b>, and the extended keys <b>148</b> catch in the dart's exposed profile <b>158</b>. At this stage, fluid pressure applied against the caught dart <b>150</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>.

p-0059The previous indexing sleeves <b>100</b> and darts <b>150</b> have keys and profiles. As an alternative, an indexing sleeve <b>100</b> shown in <figref idrefs="DRAWINGS">FIG. 6A</figref> uses a ball <b>170</b> having a sensing element <b>172</b>, such as a magnet. 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>.

p-0060Initially, the keys <b>148</b> remain retracted as shown in <figref idrefs="DRAWINGS">FIG. 6A</figref>. Once the insert <b>120</b> has been activated as shown in <figref idrefs="DRAWINGS">FIG. 6D</figref>, the insert's distal end <b>127</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>127</b> shown in <figref idrefs="DRAWINGS">FIG. 6D</figref> initially covers the keys <b>148</b> and exposes them once the insert <b>120</b> moves.

p-0061Either 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 idrefs="DRAWINGS">FIG. 6B</figref> shows how the distal end <b>127</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 idrefs="DRAWINGS">FIG. 6C</figref> shows how the extend keys <b>148</b> create a seat with a restricted diameter d to catch a ball <b>170</b>.

p-0062As 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.

p-0063When the dropped ball <b>170</b>′ reaches the keys <b>148</b> as in <figref idrefs="DRAWINGS">FIG. 6D</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 pin <b>141</b> that initially holds it in its closed condition.

p-0064Previous indexing sleeves <b>100</b> included an insert moved by fluid pressure once a set number of dart or balls have passed through the sleeve <b>100</b>. The moved insert <b>120</b> then reveals a profile or keys on a sleeve <b>140</b> that can catch the next plug (e.g., dart <b>150</b> or ball <b>170</b>) dropped through the indexing sleeve <b>100</b>. As an alternative, an indexing sleeve <b>100</b> shown in <figref idrefs="DRAWINGS">FIG. 7</figref> lacks the separate insert and sliding sleeve from before. Instead, this sleeve has an integral insert <b>180</b>. Many of the sleeve's components are the same as before, including the control circuitry <b>130</b>, battery <b>132</b>, sensor <b>134</b>, valve <b>136</b>, etc. The insert <b>180</b> defines the chambers <b>116</b><i>a</i>-<i>b </i>with the housing <b>110</b> and covers the housing's ports <b>112</b>.

p-0065When a set number of plugs (e.g., balls <b>170</b>) have passed the sensor <b>134</b> and been counted, the control circuitry <b>130</b> activates the valve <b>136</b> so that the plunger <b>138</b> opens chamber port <b>118</b>. Surrounding fluid pressure passes through the chamber port <b>118</b> and fills the chamber <b>116</b><i>a </i>to move the insert <b>180</b>. As it moves, the insert <b>180</b> reveals the housing's ports <b>112</b>. Thus, this sleeve <b>100</b> opens when a set number of plugs has passed, but the sleeve <b>100</b> lacks a seat or the like to catch a dart or ball dropped therein. Accordingly, this sleeve <b>100</b> may be useful when two or more sleeves along the tubing string are to be opened by the same passing dart or ball. This may be useful when a long expanse of a formation along a wellbore is to be treated.

p-0066As mentioned previously, several indexing sleeves <b>100</b> can be used on a tubing string. These indexing sleeves <b>100</b> can be used in conjunction with one or more sliding sleeves <b>50</b>. In <figref idrefs="DRAWINGS">FIG. 8</figref>, a sliding sleeve <b>50</b> is shown in an opened condition. The sliding sleeve <b>50</b> defines a bore <b>52</b> therethrough, and an insert <b>54</b> can be moved from a closed condition to an open condition (as shown). A dropped plug <b>190</b> (e.g., dart, ball, or the like) with its specific diameter is intended to land on an appropriately sized ball seat <b>56</b> within the insert <b>54</b>.

p-0067Once seated, the plug <b>190</b> typically seals in the seat <b>56</b> and does not allow fluid pressure to pass further downhole from the sleeve <b>50</b>. The fluid pressure communicated down the isolation sleeve <b>50</b> therefore forces against the seated plug <b>190</b> and moves the insert <b>54</b> open. As shown, openings in the insert <b>54</b> in the open condition communicate with external ports <b>56</b> in the isolation sleeve <b>50</b> to allow fluid in the sleeve's bore <b>52</b> to pass out to the surrounding annulus. Seals <b>57</b>, such as chevron seals, on the inside of the bore <b>52</b> can be used to seal the external ports <b>56</b> and the insert <b>54</b>. One suitable example for the isolation sleeve <b>50</b> is the Single-Shot ZoneSelect Sleeve available from Weatherford.

p-0068The arrangement of sleeves <b>100</b> discussed in <figref idrefs="DRAWINGS">FIGS. 4A-4C</figref> relied on consecutive activation of the indexing sleeves <b>100</b> by dropping an ever-increasing number of darts <b>150</b> to actuate ever-higher sleeves <b>100</b>. Given the various embodiments of indexing sleeves <b>100</b> disclosed herein and how they can be used in conjunction with sliding sleeves <b>50</b>, <figref idrefs="DRAWINGS">FIGS. 9A-9B</figref> show an exemplary arrangement of multiple indexing sleeves <b>200</b> and sliding sleeves <b>50</b>.

p-0069As shown in <figref idrefs="DRAWINGS">FIG. 9A</figref>, the arrangement of sleeves include a sliding sleeve <b>50</b> (S_A), a succession of three indexing sleeves <b>200</b> (I₁-I₃), and another sliding sleeve <b>50</b> (S_B). These sleeves <b>50</b>/<b>200</b> can be divided into any number of zones using packers (not shown), and their arrangement as depicted in <figref idrefs="DRAWINGS">FIG. 9A</figref> is illustrative. Depending on the particular implementation and the treatment desired, any number of sleeves <b>50</b>/<b>200</b> can be arranged in any number of zones, and packers or other devices (not shown) can be used to isolate various intervals between any of the sleeves <b>50</b>/<b>200</b> from one another.

p-0070Dropping of two different sized plugs (A &amp; B) (i.e., dart, balls, or the like) with different sizes are illustrated in different stages for this example. Any number of differently sized plugs, balls, darts, or the like can be used. In addition, the relevant size of the plugs (A &amp; B) pertains to their diameters, which can range from 1-inch to 3¼-inch in some instances.

p-0071In the first stage, operators drop the smaller plug (A). As it travels, plug (A) passes through sliding sleeve <b>50</b>(SB) without engaging its larger seat. The plug (A) also passes through indexing sleeves <b>100</b>(I₁-I₃) without opening them. Finally, the plug (A) engages the seat in sliding sleeve <b>50</b>(S_A). Fluid treatment down the tubing string <b>12</b> opens the sliding sleeve <b>50</b>(S_A) and stimulates the formation adjacent to it.

p-0072After passing through each of the indexing sleeves <b>200</b>, however, the plug (A) triggers their activation. Rather than counting the number of passing plugs, however, these sleeves <b>200</b> use their sensors (e.g., <b>132</b>) or other mechanism to trigger a timed activation of the sleeves <b>200</b>. In this case, the controller of the sleeve <b>200</b> uses a timer instead of (or in addition to) the counter described previously in <figref idrefs="DRAWINGS">FIG. 2D</figref>. Each of the indexing sleeves <b>200</b> can then be set to activate at successive times.

p-0073In second stages, for example, indexing sleeves <b>200</b>(I₁-I₃) activate at different or same times based on the preset time interval they are set to after passage of the initial sized plug (A). Additionally, depending on the type of disclosed sleeve used, additional plugs (A) of the same size may or may not be dropped to open these sleeves <b>200</b>.

p-0074In one example, any of the sleeves <b>200</b>(I₁-I₃) can be similar to the sleeve <b>100</b> of <figref idrefs="DRAWINGS">FIG. 7</figref> so that they open once activated but do not have a seat for engaging a dropped plug (A). In this way, such sleeves could expose more of a formation in the same or different interval for treatment at the same or successive times as the lowermost sliding sleeve <b>50</b>(S_A). Then, in a third stage, operators can drop a larger sized plug (B) to land in the other sliding sleeve <b>50</b>(S_B) to seal off all of the sleeves <b>50</b>(S_A) and <b>200</b>(I₁-I₃).

p-0075In another example, one or more of the sleeves <b>200</b>(I₁-I₃) can be similar to the sleeves <b>100</b> of <figref idrefs="DRAWINGS">FIG. 2A</figref>, <b>5</b>A, or <b>6</b>A. Once triggered, the timer of the control circuitry (<b>130</b>) can activate the valve (<b>136</b>) to fill the piston chamber (<b>116</b><i>a</i>) and move the sleeve's insert (<b>120</b>). This can reveal the profile (<b>146</b>) of the sliding sleeve (<b>140</b>) or can free keys (<b>148</b>) of the sliding sleeve <b>140</b> to engage another plug (A) dropped down the tubing string <b>12</b>.

p-0076For example, the indexing sleeve <b>200</b>(I₁) can be such a sleeve and can activate at a set time T₁(e.g., a couple of hours or so) after the first dropped plug (A) has passed and landed in the lowermost sliding sleeve <b>50</b>(S_A). The set time T₁gives operators time to treat the interval near the sliding sleeve <b>50</b>(S_A). Once the sleeve <b>200</b>(I₁) activates after time T₁, however, operators drop a same sized plug (A) to catch in this indexing sleeve <b>200</b>(I₁) so its adjacent formation can be treated.

p-0077This process can be repeated up the tubing string <b>12</b>. Indexing sleeve <b>200</b>(I₂) can activate at a later time T₂after the second plug (A) has passed and can catch a third plug (A), and the other sleeve <b>200</b>(I₃) can then do the same with another time T₃. In this way, operators can treat any number of intervals using the same sized plug (A) before using another sized plug (B) to land in the other sliding sleeve <b>50</b>(S_B) in a third stage.

p-0078As disclosed herein, the plug (A) can be a ball or dart with a magnetic element or strip to be detected by the sleeves <b>200</b>. Due to the narrowness of the tubing strings bore and the size limitations for plugs, conventional approaches allow operators to treat only a limited number of intervals using an array of ever-increasing sized plugs and sleeve seats. The number of sizes may be limited to about 20. Being able to insert one or more of the indexing sleeves <b>200</b> between conventionally seating sliding sleeves <b>50</b>, however, operators can greatly expand the number of intervals that they can treat with the limited number of sized plugs and sleeve seats.

p-0079The 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 described above, the various indexing sleeves disclosed herein can be arranged with one another and with other sliding sleeves. It is possible, therefore, 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.

p-0080In 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.