Patent Publication Number: US-2022235631-A1

Title: Opening a casing with a hydraulic-powered setting tool

Description:
BACKGROUND 
     Technical Field 
     Embodiments of the subject matter disclosed herein generally relate to downhole tools for perforating operations, and more specifically, to a casing string having one or more casing valves that are opened and closed with a hydraulic-powered setting tool for fracturing a desired formation. 
     Discussion of the Background 
     After a well  100  is drilled to a desired depth H relative to the surface  110 , as illustrated in  FIG. 1 , and the casing string  110  protecting the wellbore  104  has been installed and cemented in place, it is time to connect the wellbore  104  to the subterranean formation  106  to extract the oil and/or gas. 
     The typical process of connecting the casing to the subterranean formation may include the following steps: (1) placing a plug  112  with a through port  114  (known as a frac plug) above a just stimulated stage  116 , and (2) perforating a new stage  118  above the plug  112 . The step of perforating is achieved with a gun string  120  that is lowered into the well with a wireline  122 . A controller  124  located at the surface controls the wireline  122  and also sends various commands along the wireline to actuate one or more gun assemblies of the gun string. 
     A traditional gun string  120  includes plural carriers  126  connected to each other by corresponding subs  128 , as illustrated in  FIG. 1 . Each sub  128  includes a detonator  130  and a corresponding switch  132 . The corresponding switch  132  is actuated by the detonation of a downstream gun. When this happens, the detonator  130  becomes connected to the through line, and when a command from the surface actuates the detonator  130 , the upstream gun is actuated. This process is expensive, time consuming and dangerous as the gun includes shaped charges, which include explosive materials. 
     U.S. Pat. No. 6,763,892 discloses a different approach for fracturing a well, in which the individual casing tubes forming the casing string are provided with a corresponding sliding sleeve, i.e., a casing valve. The sliding sleeve can be opened or closed as desired with the help of a plurality of seals and ports. The fracturing of the formation around the casing can then be performed through the openings formed in the casing string. 
     However, this specific implementation is burdensome because the casing valve includes a number of individual components that are threaded to each other and use plural seals, which may fail and leak. In addition, this specific implementation cannot withstand the torque specifications of a typical wellbore casing because of the threaded components. 
     Thus, there is a need to provide a casing valve that can withstand the torque specifications in the wellbore casing, is not prone to leaks and is easy to open and close when a fracturing operation is desired. 
     SUMMARY 
     According to an embodiment, there is a setting tool for opening and closing a sleeve inside a casing. The setting tool includes a body extending along a central longitudinal axis (X), a set of holding dogs located around the body, and a set of sleeve dogs located around the body. The set of sleeve dogs are configured to move along the central longitudinal axis (X) relative to the set of holding dogs. 
     According to another embodiment, there is system for fracturing a well. The system includes a casing having plural openings that are covered by a sleeve when the sleeve is in a close position, and a setting tool configured to open the sleeve for fracturing operations. The setting tool includes a body extending along a central longitudinal axis (X), a set of holding dogs located around the body, and a set of sleeve dogs located around the body. The set of sleeve dogs are configured to move along the central longitudinal axis (X) relative to the set of holding dogs. 
     According to still another embodiment, there is a method for fracturing a well. The method includes lowering a setting tool inside a casing having plural openings covered by a sleeve, engaging a set of holding dogs of the setting tool with a corresponding holding groove formed inside the casing, engaging a set of sleeve dogs of the setting tool with a corresponding sleeve groove formed in the sleeve, and opening the sleeve by translating the sleeve dogs along a central longitudinal axis X, relative to the holding dogs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings: 
         FIG. 1  illustrates a well and associated equipment for well completion operations; 
         FIG. 2  illustrates a casing having a sleeve; 
         FIG. 3  illustrates a casing string that ends with a toe valve; 
         FIG. 4  illustrates a setting tool for opening the sleeve in the casing; 
         FIG. 5A  illustrates the setting tool without holding dogs, sleeve dogs and a seal while  FIG. 5B  illustrates the addition of these elements to the setting tool; 
         FIG. 6  illustrates the setting tool provided inside the casing; 
         FIG. 7  illustrates the setting tool engaging the casing with the holding dogs; 
         FIG. 8  is a flowchart of a method for opening the sleeve of the casing and fracturing a stage associated with the casing; 
         FIG. 9  illustrates the setting tool engaging the casing with the holding dogs and the sleeve dogs; 
         FIG. 10  illustrates the setting tool opening the sleeve; 
         FIG. 11  illustrates the setting tool closing the sleeve; 
         FIG. 12  illustrates the setting tool disengaging the casing; 
         FIG. 13  illustrates the setting tool moving to the next casing; 
         FIG. 14  illustrates an accumulator and fail safe mechanism of the setting tool; 
         FIG. 15  is a flowchart of a method for opening the sleeve of the casing; and 
         FIGS. 16A to 16C  illustrate a flowchart of a method for opening the sleeve, fracturing the stage associated with a casing, closing the sleeve and then repeating this operation for all the casings in the casing string. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to a casing having a valve and a hydraulic-powered setting tool that opens and closes the casing valve. However, the embodiments discussed herein are also applicable to a device that has a valve that needs to be closed and opened under tight conditions. 
     Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. 
     According to an embodiment illustrated in  FIG. 2 , a casing  200  (sometimes called a casing valve) has an interior sleeve  210 . Interior sleeve  210  has plural sleeve openings  212  that corresponds to plural casing openings  214  formed in the body  216  of the casing  200 . The sleeve  210  is shown closed in  FIG. 2 , i.e., a fluid  220  inside the casing  200  cannot move outside the body  216  through casing openings  214 . However, if the sleeve  210  is moved to the left and the sleeve openings  212  are aligned with the casing openings  214 , then the fluid  220  communicates with the outside  222  of the casing. Note that an interior diameter of the sleeve  210  is larger than a diameter of a seal region  227  so that the sleeve cannot enter the seal region for reasons to be discussed later. Further note that an interior of body  216  has a latching groove  224  and an interior of sleeve  210  has a latching groove  226 , also to be discussed later. A set of latching grooves  224  are formed inside the seal region  227  and the other set of latching grooves  226  are formed onto the sleeve  210 . 
     Plural casings  200 A and  200 B (only two are shown for simplicity, but a casing string may include tens or hundreds of casings) are shown in  FIG. 3  distributed in the well  100 . The last casing  200 A is connected to a tow valve  201 . Just before the fracturing operation, all the valves (sleeves) are closed. The toe valve  201  (an example of which is described in U.S. Pat. Nos. 9,121,247, 9,121,252, and 9,650,866) has a disk that breaks when the pressure inside the casing becomes larger than a certain threshold pressure. When this happens, a piston inside a wall of the toe valve is actuated and moves to open the openings  201 A formed through the toe valve. In this way, the toe valve stage may be fractured by the fluid  230  pumped from the surface. A wiper plug  232  has been previously pumped to the bottom of the well, past the toe valve  201  for preventing the fracturing fluid  230  to move past the toe valve. After the fracturing operation of the toe valve stage is finalized, the toe valve may be used to expel the pumped fluid into the formation. 
     To reveal the openings of the top casing of the casing string, a hydraulic-powered setting tool is placed into the well and controlled to attach to the sleeve of the casing. According to an embodiment illustrated in  FIG. 4 , the hydraulic-powered setting tool (setting tool herein)  400  has a body  402  connected to a hydraulic valve block  404  that includes plural valves  406 . Valves  406  are configured to allow in and out a fluid under pressure to activate various pistons as discussed later. In one embodiment, there are three different pistons that need to be actuated and each piston is actuated by a pair of valves. For this reason, the figure shows 6 valves. However, one skilled in the art would understand that more or less valves may be used for the setting tool. 
     Setting tool  400  also includes a first set of connecting elements  420 , called herein holding dogs because these elements would engage corresponding grooves in the casing valve and fix the setting tool relative to the casing. The setting tool also includes a second set of connecting elements  430 , called herein sleeve dogs because these elements would engage the sleeve of the casing valve and move it from the closed position to the open position and vice versa. The dogs are mechanical elements that mate with corresponding grooves formed in the body of the casing and/or the sleeve. 
     The setting tool  400  further includes a seal  440 , located downstream from the first and second set of dogs. The setting tool  400  further includes an electronics module  450  and a fishing neck  452 . The electronics module  450  includes various sensors, e.g., pressure transducer  454 , velocity sensor  456 , accelerometers, etc., that may be connected to a wireline for communicating and/or receiving various information to the surface. The hydraulic valve block  404  may include similar or additional sensors. In one application, the hydraulic valve block  404  includes a pressure transducer  408  and a power source  410 . The power source  410  may include one or more batteries. In one application, the power source  410  includes about 100 AA lithium batteries. The hydraulic valve block  404  may also include a controller  412 , that is connected to the various sensors noted above and which is configured to open and close one or more or the valves  406  so that a corresponding piston moves up and down the well. 
     In one application, the setting tool shown in  FIG. 4  may be used for different sized casing. For example, the casing may have an internal diameter of 4½″ or 5½″. Irrespective of the internal diameter of the casing, the setting tool shown in  FIG. 4  may be provided with corresponding dogs and seals to account for the change in diameter of the casing. In this respect,  FIG. 5A  shows the location A of the setting tool  400  having no sets of dogs  420  or  430  and no seal  440 . After determining the internal diameter of the casing in which the setting tool is to be deployed, the corresponding sets of dogs  420  and  430  and the seal  440  are added (slid from one end of the tool) to the body  402  of the setting tool, as illustrated in  FIG. 5B . 
     Once the sets of dogs are in position, they are attached to corresponding pistons (to be discussed later) and can be moved relative to the body of the casing, both toward or away (i.e., radially) from a central longitudinal axix X of the body and also along the central longitudinal axis X. To move the dogs radially along axis X, ramps are sliding under the dogs and the ramps are powered by the pistons noted above. The pistons in turn are actuated with hydraulics, provided through the valves  406 . In one application, instead of using hydraulics and solenoids for actuating the pistons, it is possible to use electrical motors with power screws. The hydraulics energy is supplied by the pressure established inside the casing. For this reason, the setting tool includes one or more accumulators (e.g., spring-loaded accumulators) that can store enough hydraulic energy to open and close several casing valve sleeves. The setting tool may use solenoid valves  406  for reducing the electrical energy required to open and close the valves. These pistons are shown and discussed in the next figures. 
       FIG. 6  shows a casing  200  (considered to be the top casing in the casing string) having inside the setting tool  400 . The holding dogs  420 , the sleeve dogs  430  and seal  440  of the setting tool  400  are shown in cross-section. Also visible are the holding grooves  224  of the casing  200  and the sleeve grooves  226  of the sleeve  210 . The aim of this embodiment is to connect the set of holding dogs  420  to the corresponding holding groove  224  to fix/hold the setting tool inside the casing  200 , and then to connect the set of sleeve dogs  430  to the sleeve groove  226  to take control of the sleeve  210 . In this way, the sleeve dogs  430  may be moved relative to the holding dogs  420  to open and close the sleeve  210  for fracturing the stage associated with the top most casing. After the fracturing operation is finalized, the sleeve  210  is closed and the sleeve dogs and holding dogs are disengaged from their respective grooves so that the setting tool  400  can move to the next casing to repeat the above operations and fracture the stage associated with the next casing. Because the sleeves of all the casings are closed except for the sleeve of the current casing in which the setting tool is deployed, the fracturing is controlled to take place only in the current stage. 
       FIG. 6  also shows holding dogs ramps  422  and sleeve dogs ramps  432 . These ramps can move along the longitudinal direction X of the casing  200 , to make the corresponding dogs to move along the radial direction R. Ramps  422  are actuated by piston  424  while ramps  432  are actuated by piston  434  (see  FIG. 7 ).  FIG. 6  also shows the sleeve  210  having plural sleeve openings  212  and the casing  200  having plural casing openings  214 . Note that the two sets of openings are not aligned in  FIG. 6 , which means that the sleeve is closed and no fluid from inside the casing can fracture the formation  106  around the casing. 
     A method for moving the setting tool inside the casing, engaging the holding dogs followed by the sleeve dogs, and opening the sleeve of the casing for fracturing operations is now discussed with regard to  FIG. 8 . In step  800 , the setting tool  400  is provided inside the casing  200 , as illustrated in  FIG. 6 . The process starts with the top casing and then moves to the next casing, toward the bottom of the well, until all the casings are fractured. Those skilled in the art would understand that because of the autonomy of the setting tool, the operator can fracture selected stages, i.e., only selected casing valves can be opened for fracturing. 
     In step  802 , a top portion  420 A (see  FIG. 7 ) of the holding dogs  420  is engaged with the holding groove  224 . This engagement takes place as the holding dogs  420  are biased by springs  426  (toward the central part of the setting tool along the radial direction) and because the holding ramp  422  was moved by the corresponding piston  424  to push the holding dogs along the radial direction R, toward the outside of the casing  200 . In this regard, note that a bottom region  420 B of the holding dogs  420  are located on top of ramp  422  in  FIG. 7  while  FIG. 6  shows the same bottom region of the holding dogs at the bottom of the ramp. Thus, the movement of the ramp  422  because of the piston  424  has pushed the holding dogs toward the interior wall of the casing  200  and when the top region  420 A of the holding dogs  420  has met the corresponding holding groove  224 , the two elements have locked in place as shown in  FIG. 7 . To prevent the top region  420 A of the holding dogs  420  to engage with the sleeve groove  226  as the setting tool is travelling through the casing, a size of the sleeve groove  226  is larger than a size of the top region  420 A so that the holding dogs  420  cannot engage with the sleeve groove  226 . Note that at this time the sleeve  210  is still closing the casing openings  214 . Also note that at this time the seal  440  is abutting tightly against the internal wall  200 A of the casing  200 , thus in effect isolating the stage corresponding to the current casing  200  from the rest of the stages associated with other casings. 
     The movement of the pistons is controlled by the processor  412 , valves  406 , and at least an accumulator that stores hydraulic energy as now discussed. When the setting tool is approaching the top most casing, the operator of the setting tool may send a signal along the wireline to the processor  412  for moving the holding dogs along the radial direction. Upon receiving this command, processor  412  opens one of the valves  406 , which corresponds to piston  424 , and allows the pressurized fluid inside the accumulator to move the piston along the longitudinal axis X, as illustrated by the corresponding arrow in  FIG. 6 , to move the ramp  422  under the holding dogs. As the setting tool is moving through the casing  200 , the holding dogs  420  eventually engage the holding groove  226 . At this time, the setting tool stops and the velocity sensors  456  determine that the setting tool has stopped. Processor  412  then choses valve  406  and may inform the operator of the well that the setting tool is set. When the setting tool is set, the pressure above it increases, which signals to the operator to stop pumping the setting tool. 
     In step  804 , the sleeve dogs  430  are engaged with the corresponding sleeve grooves  226 . Because controller  412  has determined that the setting tool has stopped and knowing that the holding dogs are engaged, it can instruct the sleeve dogs  430  to engage the sleeve groove  226 . In this regard, note that in  FIG. 7  the ramp  432  is not biasing the sleeve dogs  430  along the radial direction. However,  FIG. 9  shows the ramp  432  has moved along the longitudinal direction X due to piston  434  (which is controlled by processor  412  and corresponding valve  406 ), so that a top region  430 A of the sleeve dogs  430  is engaged with the sleeve groove  226  and a bottom region  430 B of sleeve dogs  430  has moved up the ramp  432 . At this time, the holding dogs are holding the setting tool fixed relative to the casing and the sleeve dogs have engaged the sleeve and are ready to move the sleeve along the longitudinal axis X. 
     In step  806 , the sleeve  210  is opened as illustrated in  FIG. 10 . To move the sleeve dogs  430 , another piston  438  (a second piston) is used. This second piston  438  is associated with the sleeve dogs  430  and moves not only the sleeve dogs as illustrated in  FIG. 10 , but also the ramp  432 . Due to the movement of the sleeve dogs  430  relative to the holding dogs  430  and implicitly relative to the casing  200 , the sleeve  210  moves along the longitudinal axis X, toward the left in the figure, so that the sleeve openings  212  become aligned with the casing openings  214 . The movement of the second piston  438  is coordinated by controller  412  and achieved by corresponding hydraulic valve  406 . 
     In step  808 , the fracturing fluid is pumped from the casing and exits through aligned openings  212  and  214  into the formation  106 , as indicated by arrow B in  FIG. 10 . Note that due to the seal  440 , which abuts against the internal wall of the casing  200 , no sand or other formation debris from the formation passes the seal toward the other casing valves. Thus, the setting tool can freely move toward the other casing valves after finalizing the fracturing of the current stage. 
     When the fracturing operation is concluded for the current stage, the sleeve  210  needs to be moved back to the closed position, to close the sleeve openings  212 . Thus, in step  810 , the sleeve is closed. To instruct the controller  412  to close the sleeve, the following mechanism may be used. Suppose that the operator of the well has finalized the fracturing operation. The operator may send a signal to the controller  412  for closing the sleeve. The signal may be transmitted in various ways, i.e., as an electrical signal along a wire, as an acoustic signal with a modem, etc. The embodiment presented in  FIG. 10  uses the following mechanism. The well is allowed to flow-back (i.e., the fluids inside the well flow toward the surface) after the fracturing operation. The flow-back is stopped (usually by using pumps at the surface) and then the fluid is flown into the well. This pattern of flowing the fluid in one direction, stopping the flow, and the flowing the fluid in the opposite direction can be identified by the controller  412  by using the velocity sensor  456 . In one application, the pattern includes flowing 5 barrels back (i.e., out of the well), waiting for 2 minutes, and then pumping 5 barrels back into the well. Other quantities and times may be used. When this “finished pattern” is identified, the controller  412  knows that the fracturing process is finished and needs to close the sleeve. 
     The controller  412  connects another valve  406  to the hydraulic pressure in the accumulator so that the second piston  438  moves in the opposite direction relative to the configuration shown in  FIG. 10 .  FIG. 11  shows the second piston  438  taking the sleeve dogs  430  and the sleeve  210  back to the closed position as in  FIG. 9 . Note that during the opening and the closing of the sleeve, the holding dogs  420  and the seal  440  do not move along the longitudinal axis X or along the radial axis R. 
     After the sleeve  210  has been closed, it is time to move the setting tool to the next casing. To achieve this objective, the holding dogs  420  and the sleeve dogs  430  are disengaged in step  812  (or closed, i.e., retracted along the radial axis R toward the center axis of the setting tool), as illustrated in  FIG. 12 . The dogs are disengaged from their connections with the corresponding grooves in the casing by moving the sleeve ramps  432  with the piston  434  and the holding ramps  422  with the piston  424 . In this regard, note that  FIG. 12  shows the bottom regions  420 B and  430 B of the holding dogs  420  and the sleeve dogs  430 , respectively, to be at the bottom of their respective ramps.  FIG. 12  also shows the top regions  420 A and  430 A of the holding dogs  420  and the sleeve dogs  430 , respectively, disengaged from the corresponding grooves  224  and  226 . The controller  412  can be programmed to perform these operations sequentially, with a given wait time between two subsequent operations. 
     In step  814 , the operator pumps the setting tool  400  downward toward the next casing. The setting tool monitors its movement with its velocity sensor  456  (e.g., the velocity sensor may include one or more accelerometers). After a given distance D, which is calculated to be less than a distance from the openings  212  of one casing to the openings of an adjacent casing, the controller  412  is configured to open the holding dogs (i.e., to move the corresponding rams) so that the holding dogs catch and engage the holding groove of the next casing. This means that the process disclosed in  FIG. 8  returns to step  802  and performs all the steps discussed above for the next casing. This process continues until each casing has been opened, fractured and then closed. At the end of this process, all the stages have been fractured and all the valves are closed. As previously discussed, the operator may select to not open each casing. 
     The setting tool needs now to be retrieved to the surface. For this action, a retrieval tool is sent in the well. The retrieval tool is configured to latch onto the fishing neck  452  of the setting tool  400 . The retrieval tool may be attached to the wireline (or another line, e.g., slickline) to be lowered into the well. Once the retrieval tool latches on the fishing neck  452 , the wireline is pulled up to bring to the surface the setting tool. The controller  412  of the setting tool, based on measurements received from the velocity sensor, determines that the setting tool is moving toward the surface and can instruct the valves  406  to actuate the corresponding pistons to make sure that the dogs sit at the bottom of the corresponding ramps, so that neither the holding dogs nor the sleeve dogs engage a corresponding groove in the interior wall of the casings. 
     In one embodiment, as shown in  FIG. 13 , is it noted that sleeve dogs  430  have the top portion  430 A moving up and down along the radial direction R as previously discussed. The top portion  430 A is biased by a spring  436 . However, when the corresponding ramp  432  is moved under the base portion  430 B, top portion  430 A moves in tandem with the base portion  430 B upwards. A protection region  1300  is formed around the top portion  430 A. The protection region  1300  is designed to not engage any groove in the interior wall of the casing when the setting tool moves through the setting tool.  FIG. 13  shows that the top region  430 A fits inside the protection region  1300  when the ramp  432  is not pushing radially the base portion  430 B. The same structure may be employed for the holding dogs  420 . Holding dogs  420  may have plural springs  426 . In one application, the holding dogs and/or the sleeve dogs have multiple elements that “bite” into the corresponding groove formed in the interior wall of the casing. The figures discussed until now show a holding or sleeve dog at the top the figure and one at the bottom. Those skilled in the art would understand that other elements similar to those shown in the figures may be added all around the longitudinal axis X of the setting tool to better engage the casing and/or the sleeve. 
     In one embodiment, the setting tool may be used to open the sleeve of each casing valve while the setting tool moves from the bottom of the well toward the top so that well production can commence. For this situation, the holding dogs are open, i.e., the corresponding ramp is moved under the dogs to push them outward along the radial direction. The setting tool is moved upward with the wireline until the holding dogs engage a corresponding groove in a casing. The velocity sensors of the setting tool determine that the setting tool has stopped. The controller of the setting tool then instructs the sleeve dogs to engage the sleeve groove of the casing and open the sleeve. The casing sleeve is opened. Then all the dogs are disengaged and the setting tool can move upwards towards the next casing. 
     In one embodiment, it is possible that the setting tool gets stuck in a casing. In this situation, as shown in  FIG. 14 , the wireline or slickline is pulled with an increased force to shear pins  470 , which make the ramps  422  and  432  to move away from the base portions of the dogs, so that the dogs move toward the central part of the setting tool under their bias generated by the springs  426  and  436 , and thus, the setting tool is free to move inside the casing. The wireline is then used to pull the setting tool out of the casing string.  FIG. 14  also shows possible accumulators  480 ,  482  and  484  for storing the hydraulic energy. In one application, chambers  482  and  484  are used for moving the pistons discussed above along a desired direction. 
     A method for opening a sleeve of a casing and then fracturing a stage associated with the casing is now discussed with regard to  FIG. 15 . The method includes a step  1500  of lowering a setting tool  400  inside a casing  200  having plural openings  212  covered by a sleeve  210 , a step  1502  of engaging a set of holding dogs  420  of the setting tool  400  with a corresponding holding groove  224  formed inside the casing  200 , a step  1504  of engaging a set of sleeve dogs  430  of the setting tool  400  with a corresponding sleeve groove  226  formed in the sleeve  210 , and a step  1506  of opening the sleeve  210  by translating the sleeve dogs  430  along a central longitudinal axis X, relative to the holding dogs  420 . The method may further include one or more of the step of fracturing a formation around the casing by pumping a fluid into the casing, the step of closing the sleeve by translating back the sleeve dogs along the central longitudinal axis X, relative to the holding dogs, the step of disengaging the holding dogs and the sleeve dogs from their respective grooves, and the step of pumping the setting tool further down the well to the next casing. In one application, the step of opening includes a step of activating a sleeve piston for translating the sleeve dogs along the central longitudinal axis, a step of releasing from an accumulator a fluid under pressure for activating the sleeve piston and/or a step of recharging the accumulator by pumping the fluid into the well with a pump at a surface of the well. 
     Another method for fracturing a well, with the setting tool discussed in the previous embodiments, is now discussed with regard to  FIGS. 16A to 16C . The method includes a step  1600  of providing multiple casing valves in a casing string, the casing string having a toe valve at the bottom. The casing valves do not need to have burst discs or any type of time delay, but each casing has latching profiles and a sliding sleeve as illustrated in the previous figures. 
     In step  1602 , the wiper plug is pumped down. When the wiper plug bottoms-out, the operator of the well will note a pressure spike at the surface. Then, in step  1604 , the well is pressured up to test the casing string. If the pressure holds, then the operator applies more pressure to rupture the burst disk in the toe valve. At this time, the openings in the toe valve are opened and in step  1606 , the stage associated with the toe valve is fractured. After the fracturing of this stage is completed, the well may be cleaned. 
     In step  1608 , the setting tool  400  is inserted into the well and pumped down. Because the setting tool is moving only in water, there is less chance of getting stuck in the casing. The setting tool has a pressure transducer and a fluid velocity sensor at least at the top of the body. The setting tool has holding dogs that are spring-loaded open. However, they default to closed if there is a loss of power. The setting tool has a spring-loaded accumulator  480  with enough hydraulic energy to open and close several casing valve sleeves. The setting tool may use solenoid valves  406  to reduce the electrical energy required to activate the dogs. The accumulator  480  stores fluid under pressure and is configured to actuate a holding piston, a first sleeve piston and a second sleeve piston for moving the set of holding dogs and the set of sleeve dogs. In one application, the holding piston, the first sleeve piston and the second sleeve piston are concentric to each other. 
     The spring-loaded holding dogs latch in step  1610  into a profile (e.g., holding groove) in the first casing valve near its heel and holds the setting tool in position with its seal  440  under the casing valve. The well is now plugged and the operator of the well notices a pressure spike at this point. 
     In step  1612 , the setting tool knows it stopped (because of the measurement received from the velocity sensor and/or pressure transducer) and is in position. In step  1614 , the operator increases the casing&#39;s pressure to re-charge the hydraulics (e.g., accumulator  480 ) in the setting tool  400 . In step  1616 , the setting tool uses its stored energy to open the sleeve dogs and to open the casing valve&#39;s sleeve. Once the sleeve is open, the upper-most stage is fractured in step  1618 . In step  1620 , if the well sands out, the operator can cycle the flow to clear it up, because the setting tool is held below the flow, and not in the sand. 
     After finishing the fracturing operation, the operator sends in step  1622  a stop and start fluid flow pattern so that the setting tool recognizes as the “Finished Frac-ing Pattern” signal indicating that the fracturing operation has been concluded (if no signal is received, it times out based on a timer started by the controller  412 ). The setting tool closes in step  1624  the casing valve&#39;s sleeve, the setting tool&#39;s sleeve dogs, and then closes the setting tool&#39;s holding dogs. In step  1626 , the operator pumps the setting tool to the next casing valve, still moving in water only. Next, the setting tool spring-opens the holding dogs and latch onto the next casing valve (i.e., repeats step  1610 ), and seals. The process repeats now the steps  1612  to  1626  of holding in position with the seal, pressurizing the casing to charge the setting tool, opening the sleeve, fracturing the current stage, closing the sleeve, closing the holding dogs, moving the setting tool to the next casing valve, spring-opening the holding dogs, latching to the next casing valve and so on. 
     When this process is completed, all of the stages are fractured and their sleeves are re-closed. The retrieval tool is pumped down in step  1628 , on a Slickline, or a Wireline and latched onto the setting tool. The setting tool would be chased down to the toe valve. However, the fluid flow is allowed to go around the setting tool. The setting tool&#39;s holding dogs are still sprung open. The setting tool is pulled up the casing spring in step  1628  until the holding dogs latch to the lowermost casing valve. The well is again plugged. In step  1630 , the operator pressures the well to charge the accumulator of the setting tool. In step  1632 , the setting tool opens the casing valve&#39;s sleeve so that oil and/or gas from the formation can enter the casing. In step  1634  the setting tool closes its holding dogs and the setting tool is pulled up in step  1636  toward the next casing valve and the previous steps are repeated to open the next sleeve. In this way all the sleeves are open and the exploration of the well can commence as the oil and/or gas is now flowing through the openings into the well. 
     The method discussed above may be modified as now discussed. In one embodiment, instead of pumping the retrieval tool to the bottom of the well to hook it to the setting tool, the setting tool can be moved up-hole by using the flow-back of each of the stages. When the setting tool finishes opening the last casing valve, it closes its holding dogs and then can flow-back the well. The setting tool moves up toward the next casing valve. As the setting tool arrives at the next casing valve, the setting tool spring-opens the dogs and latches onto the next casing valve. Then, the setting tool opens the sleeve, and the operator pressures up the formation and the setting tool. Next, the setting tool closes the holding dogs and flows-back the well so that the setting tool moves upward. This process continues until the setting tool arrives at the last casing valve near the heel. After opening the last sleeve, the setting tool is kept latched to the casing valve and the retrieval tool is pumped in the vertical section of the well. After the retrieval tool is connected to the setting tool, the holding dogs of the setting tool are released from the groove of the casing, and both tools are retrieved from the well. Those skilled in the art would be able, having the benefit of this disclosure, to practice different variations of the methods discussed herein. Note that while the above embodiments have discussed using a wireline to convey the setting tool inside the well (or at least to retrieve the setting tool), it is possible to have the setting tool move autonomously inside the well, or to be attached at the end of a slickline or wire rope, or wireline, or coiled tubing or coiled tubing with wireline inside. 
     The setting tool discussed above may have the hydraulics implemented with solenoids for powering the holding dogs open and closed, and open and close the casing valve&#39;s sleeve. The holding dogs are configured to “Fail safe” in the closed position. The controller and sensors may be selected to work with “AA” lithium batteries. Thus, no high power electrical devices are used except for the solenoids. In one application, the setting tool would carry enough batteries for a  100  casing valve stages per run. In another application, the setting tool could carry enough batteries to complete the entire job, so that recharging is not required. 
     During pressurizing the casing, the upper pressure may move a piston in the setting tool that has check valves. This “pump” mechanism re-charges the hydraulic accumulator during every pressurization cycle. 
     “Time Based,” “Velocity Pattern Recognition,” or “Pressure Pattern Recognition” signals based communication is possible between the operator of the well and the controller of the setting tool. These types of communication are enhanced by the presence of the pressure transducers, fluid velocity sensor, and accelerometer. In one application, the setting tool may have an information storing device (e.g., a memory) for post-job analysis (as an example, it will know if all the sleeves were opened). 
     The setting tool may act as a moving, resettable plug, rated at 10,000 psi differential pressure, with dogs that open and close the casing valve&#39;s sleeves. In one application, the setting tool may be designed to have the upper section made of materials that are acid resistant. The setting tool may be designed for multiple jobs, with minimal maintenance. 
     One or more advantages of the setting tool discussed above are as follows:
         pin point frac-ing performed at each stage;   no debris in the well due to the seal  440 ;   no dissolving balls are needed;   no drilling out of various plugs between the stages is required;   no waiting for activation;   need not Frac all of the casing valve stages;   for an autonomous tool, pre-program the setting tool to skip some casing valves, or use simple down-link communication (pressure and fluid velocity);   any of the stages can be fractured with another future run with the setting tool;   no coiled tubing frac-ing;   the setting tool could be conveyed on slickline, wireline, coiled tubing, or drill pipe;   the sleeves can be individually re-opened or re-closed with future runs;   the sleeves can be partially opened;   selected sleeve can be open or closed;   with a setting tool memory, a record is keep of when each sleeve was moved;   if a wireline is conveyed, the setting tool can contain a pump to charge its hydraulic system, and have real time data acquisition of pressure and velocity downhole while frac-ing;   less water usage than a conventional fracturing operation;   no explosives are used during the fracturing;   the casing valves are 11″ shorter and have a smaller outer diameter (e.g., 6.50″) than current FracBack design;   the casing valves have no deforming seat, no locking ring, no collet, no balls, no darts, nor any outer burst disk cover;   enough batteries can be carried for over a hundred stages;   the setting tool is reusable while the conventional guns are not;   the setting tool may include communication capability while the conventional guns do not;   the same setting tool may be used for different size casings;   the setting tool may have the wear items (seals and dogs) easily replaced for multiple usage;   the parts exposed to corrosion can be made of acid resistant materials;   the structure of the casing valve being simple, its price is low;   the setting tool requires less surface equipment for its usage;   no conveyance equipment in the casing during Frac-ing;   faster setup that conventional fracturing operations;   the memory record the pressures;   depth knowledge; and   can monitor down-hole pressure in real-time.       

     The disclosed embodiments provide methods and systems for selectively actuating one or more casing valves in a casing string. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details. 
     Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein. 
     This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.