Patent Publication Number: US-2023142393-A1

Title: Staged cementing device and staged cementing method

Description:
CROSS REFERENCE OF RELATED APPLICATION 
     The present application claims the priority of Chinese patent application No. 202010596606.1, entitled “Staged cementing device” and filed on Jun. 28, 2020, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to the technology of petroleum well cementation, in particular, to a staged cementing device, and more specifically, to a staged cementing device with a multiple-expansible packer. The present invention further relates to a staged cementing method using the staged cementing device. 
     TECHNICAL BACKGROUND 
     Well cementation technology is an important technical link in the well drilling and completing process. The quality of well cementation directly affects subsequent operations in oil and gas  20  production. 
     Staged cementing process is a common process in the well cementation technology. As explorations and exploitations continue to deepen, more and more ultra-deep wells have been developed. When the well cementation with an intermediate casing is performed on some wells, due to the poor  25  cementing ability and low loading capacity of the formation, the staged cementing process is often used to reduce the liquid column pressure, and thus reduce leakage. However, for ultra-deep absorption wells, even if the staged cementing process is adopted, leakage will still occur during a primary cementing procedure. Moreover, since the lost layer has not been sealed after the primary cementing procedure, leakage, even loss of return loss, will still exist during a secondary cementing  30  procedure. Accordingly, the quality of well cementation cannot be ensured even with a subsequent cementing extrusion, so that the cost-effectiveness is low and thus it is difficult to satisfy the demand on improving speed and efficiency for oil-field developments. In addition, after the production in some areas, the annulus of the intermediate casing will suffer pressure problem of different degrees. In order to ensure safe production, it is required to inject protective liquid into the annulus. However, the cost is high and the management is difficult. 
     A staged cementing device with a packer can seal the leakage layer or the reservoir, partially reducing leakage in the well cementation or protecting the reservoir. However, the expandable fluid of the packer is a drilling fluid without strength. After the process is completed, the packer will be always under hydraulic pressure, resulting in the risk of packer aging and liquid leakage. In addition, there are irregularities in the wellbore, which will generate tiny gaps during the expansion of the packer. When there is gas in the well, the gas will pass through the packer to cause the pressure problem in the annulus. 
     Therefore, it is difficult for the current staged cementing process to meet the requirements of well cementation nowadays. 
     SUMMARY OF THE PRESENT INVENTION 
     Directed to the above problems, the present invention proposes a staged cementing device, and a staged cementing method using the staged cementing device. 
     According to a first aspect of the present invention, a staged cementing device is proposed, comprising: a hollow cylindrical body, which includes an inner chamber, a circulating opening extending through a wall of the body, and a liquid inlet recess open to the inner chamber and formed on the wall of the body; an opening assembly arranged in the body, the opening assembly comprising an opening sleeve and an opening seat located in the opening sleeve, wherein in an initial state, the opening sleeve is connected with the body through a first shear pin and covers the circulating opening, and the opening seat is connected with the opening sleeve through a second shear pin and covers the liquid inlet recess; and a packer, which includes a packing valve body connected with a downstream end of the body, and a packer rubber arranged downstream of the packing valve body, the packing valve body including a flow channel in communication with the liquid inlet recess, and the packer rubber including a liquid reservoir in communication with the flow channel. The second shear pin is configured to be sheared off in response to a primary pressure build-up in the body after completion of a primary cementing procedure, causing the opening seat to move downward to open the liquid inlet recess, whereby swelling fluid entering the inner chamber of the body in the primary cementing procedure enters the liquid reservoir through the liquid inlet recess and the flow channel, thereby causing the packer rubber to expand. 
     In an embodiment, the liquid reservoir is filled with an accelerant, which is capable of reacting with the swelling fluid so that the packer rubber generates a secondary expansion. 
     In an embodiment, the swelling liquid is a part of displacing fluid. Preferably, the swelling liquid is liquid epoxy resin, and the accelerant is liquid adjuvant. 
     In an embodiment, the primary pressure build-up is achieved by putting down an opening tool engageable with the opening seat. 
     In an embodiment, a receiving seat is further provided at a downstream end of the opening sleeve, for restricting a distance of downstream movement of the opening seat. 
     In an embodiment, the liquid inlet recess is configured as a groove formed in an inner wall of the body, wherein the flow channel is formed in a wall of the packing valve body, and extends axially throughout the packing valve body. 
     In an embodiment, the packer further comprises a base pipe fixedly connected with the packing  25  valve body, wherein the base pipe is located radially inside the packer rubber, and the liquid reservoir is formed by a gap between the base pipe and the packer rubber. 
     In an embodiment, two supporting sleeves separated from each other are provided on an outer surface of the packer rubber, for defining an axial area where the packer rubber expands. 
     In an embodiment, the first shear pin is capable of being sheared off in response to a secondary pressure build-up in the body, so that the opening sleeve is caused to move downstream, thereby opening the circulating opening and closing the liquid inlet recess. 
     In an embodiment, a closing sleeve is provided upstream of the opening sleeve, and connected with the body through a third shear pin. The third shear pin is configured to be sheared off in response to a tertiary pressure build-up in the body during a secondary cementing procedure, causing the closing sleeve to move downstream to close the circulating opening. 
     In an embodiment, a closing seat is provided in the closing sleeve, wherein the tertiary pressure build-up is achieved through putting down a closing tool engageable with the closing seat. 
     In an embodiment, an elastic member is provided on an outer wall of the closing sleeve, and an elastic-member receiving groove is provided in the inner wall of the body, for accommodating the elastic member and maintaining a position of the closing sleeve after the closing sleeve closes the circulating opening. 
     In an embodiment, the packer rubber is made of hydrocarbon-expansible rubber. 
     According to a second aspect of the present invention, a staged cementing method with the staged cementing device as mentioned above is proposed, comprising steps of: putting down an opening tool in the staged cementing device to engage with the opening seat, and shearing off the second shear pin through the primary pressure build-up, so that the opening seat moves downstream to open the said liquid inlet; flowing the swelling liquid to enter the liquid reservoir through the inner chamber of the body, the liquid inlet recess and the flow channel, thereby causing the packer rubber to expand; shearing off the first shear pin through the secondary pressure build-up so that the opening sleeve moves downstream to open the circulating opening, and at the same time communication between the liquid inlet recess and the flow channel is cut off; and putting down the closing tool to be in engagement with the closing seat, and shearing off the third shear pin through the tertiary pressure build-up, so that the closing sleeve moves downstream to close the circulating opening again. 
     In an embodiment, the swelling fluid is reacted with the accelerant in the liquid reservoir, for the secondary expansion of the packer rubber. 
     According to the staged cementing device of the present invention, the packer is not affected by the pressure in the pipe. The liquid injection channel cannot be opened without the opening tool, thus avoiding accidental opening operation caused by the pressure in the tube. In addition, after the liquid injection channel is opened, the displacing fluid enters the liquid reservoir of the packer rubber, realizing the primary expansion of the packer to block up the annulus. In this way, after the circulating opening is opened, the liquid column pressure will be reduced due to the primary expansion of the packer which blocks up the annulus, thereby reducing the leakage of the primary cement mud, preventing the leakage of the cement in the secondary cementing procedure, and thus improving the quality of the well cementation. Moreover, the accelerant in the packer will be chemically reacted with the displacing fluid to be cured in a predetermined time, thus forming into one piece with the packer rubber. In this way, after curing, the packer rubber will not shrink but expand slightly in terms of volume, thereby realizing the secondary expansion of the packer. 
     Therefore, it is possible to avoid the aging and damage of the packer rubber, which may cause the liquid to flow out and eventually lead to the failure of the packer. Further, the packer rubber of the packer is made of hydrocarbon-expansible rubber, which can, on the basis of previous expansions, generate a further expansion (i.e., tertiary expansion) with hydrocarbon medium, such as gas or oil, in the reservoir. This tertiary expansion can fill tiny gaps, thus further improving the long-term sealing ability of the packer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the present invention will be explained in more detail by way of illustrative exemplary embodiments with reference to the accompanying drawings. In the drawings: 
         FIG.  1    shows the overall structure of a staged cementing device according to a specific embodiment of the present invention, wherein the device is in an initial state; 
         FIG.  2    is a partial enlarged view of the device as shown in  FIG.  1   , showing the positions of an opening seat and an opening sleeve; 
         FIG.  3    shows the staged cementing device according to the present invention, wherein a packer rubber is in an expanded state but a circulating opening is still closed; 
         FIG.  4    shows the staged cementing device according to the present invention, wherein the packer rubber is in the expanded state and the circulating opening is opened; 
         FIG.  5    is a partial schematic view of the staged cementing device according to the present invention, showing a state in which the circulating opening is closed again; 
         FIG.  6    shows an opening tool according to one embodiment of the present invention; and 
         FIG.  7    shows a closing tool according to one embodiment of the present invention. 
     
    
    
     In the drawings, the same reference numerals are used to indicate the same components. The drawings are not drawn to actual scale. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present invention will be further described below with reference to the accompanying drawings. In the context of the present invention, directional terms “down”, “downstream”, “downward” or the like refer to a direction away from the well head, while directional terms “upper”, “upstream”, “upward” or the like refer to a direction toward the well head. 
       FIG.  1    schematically shows the structure of a staged cementing device according to the present invention. In this specific embodiment, the staged cementing device is a staged cementing device  10  with a multiple-expansible packer. 
     As shown in  FIG.  1   , the staged cementing device  10  includes a hollow cylindrical body  100 . The body  100  includes an inner chamber  110  formed therein, a circulating opening  120  extending through a wall of the body, and a liquid inlet recess  130  (see  FIG.  2   ), which is formed on an inner surface of the wall of the body and in communication with the inner chamber  110 . An upper joint  140  is connected to an upstream end of the body  100 , in order to connect with other components of a casing. The liquid inlet recess  130  is disposed downstream of the circulating opening  120 , which is used for a secondary cementing procedure. The function of the circulating opening is well known in the art, and thus will not be described in detail here. The function of the liquid inlet recess  130  will be described in detail below. 
     According to the present invention, an opening assembly  300  is provided in the cylindrical body  100  of the staged cementing device  10 , and includes an opening sleeve  310  arranged in the body  100  and an opening seat  320  arranged in the opening sleeve  310 . In an initial state as shown in  FIG.  1   , the opening sleeve  310  is connected to the body  100  through a first shear pin  180 , and covers the circulating opening  120 . As shown in  FIG.  2   , the opening seat  320  is connected to the opening sleeve  310  through a second shear pin  182 , and covers the liquid inlet recess  130 . In the embodiment as shown in  FIGS.  1  and  2   , the first shear pin  180  is disposed downstream of the circulating opening  120 , but upstream of the second shear pin  182 . The shear stress of the first shear pin  180  is set to be greater than that of the second shear pin  182 , that is, the second shear pin  182  will be sheared off prior to the first shear pin  180 . 
     As used herein, the term “initial state” refers to a state prior to a primary cementing procedure.  FIGS.  1  and  2    both show the staged cementing device  10  in the initial state.  FIG.  3    shows a state after the primary cementing procedure but before the secondary cementing procedure. 
     In addition, according to an embodiment of the present invention, the opening assembly  300  further includes a receiving seat  330 . As shown more clearly in  FIG.  2   , the receiving seat  330  is secured within the opening sleeve  310  through, for example, threads, and preferably located at a downstream end of the opening sleeve  310 . The receiving seat  330  is used to receive the opening seat  320  moving downward, thus defining the distance of the downward movement of the opening seat  320 . This downward movement of the opening seat  320  will be described in detail below. 
     As shown in  FIG.  1   , according to the present invention, the staged cementing device  100  further includes a packer  200  disposed downstream of the cylindrical body  100 . The packer  200  includes a packing valve body  210 , which is fixedly connected to the downstream end of the body  100  by, e.g., threaded engagement. The packing valve body  210  is of, for example, a cylindrical structure, with a step  215  formed on an inner wall thereof. The packer  200  further includes a base pipe  250 , which is, for example, fixedly connected to a downstream end of the packing valve body  210 , and a packer rubber  220  arranged around the base pipe  250 . In the illustrated embodiment, an upstream end of the base pipe  250  extends into an inner chamber of the packing valve body  210 , and is connected with the downstream end of the packing valve body  210  through threads. A lower joint  270  is provided at a downstream end of the packer rubber  220 . The lower joint  270 , together with a short casing  272  fixed thereto, is used to connect subsequent tools. 
     As shown in  FIG.  2   , the packing valve body  210  includes an axially extending flow channel  230  formed therein, which is in communication with the liquid inlet recess  130  in the body  100 . The flow channel  230  extends axially throughout the packing valve body  210 . In addition, as shown in  FIG.  1   , the packer rubber  220  includes a liquid reservoir  240  in communication with the flow channel  230 . 
     The liquid reservoir  240  can similarly extend axially within the packer rubber  230 . In an alternative embodiment, the liquid reservoir  240  may be formed by a gap between the base pipe  250  and the packer rubber  230 . Moreover, two supporting sleeves  260  which are separated from each other are provided around the packer rubber  230 . A first supporting sleeve  260  located upstream is connected with the packing valve body  210 , while a second supporting sleeve  260  located downstream is connected with the lower joint  270 . The two supporting sleeves  260  can be used to limit an axial area where the packer rubber  220  expands. That is, a portion of the packer rubber  220  between said two supporting sleeves  260  can expand outward. 
     An accelerant is filled in the liquid reservoir  240  of the packer rubber  230 . The accelerant is a kind of liquid that can be uniformly mixed with a swelling fluid (for example, a part of a displacing fluid, preferably liquid epoxy resin) and then cured, so as to realize a secondary expansion of the packer rubber  220 , which will be described in detail below. One skilled in the art can readily select the type of the accelerant according to the specific swelling fluid used. In addition, by adding necessary components in the accelerant, the reaction time for the accelerant and the swelling fluid can be controlled. That is, the accelerant can be reacted with the swelling fluid at a predetermined time, so as to realize the secondary expansion of the packer rubber at the predetermined time. 
     According to an embodiment of the present invention, the packer rubber  220  is made from hydrocarbon-expansible rubber, which can be expanded continuously in the presence of hydrocarbons, so that the packer rubber  220  can meet the performance requirements on the primary and secondary expansions at the same time. 
     In addition, as shown in  FIG.  1   , in the body  100 , a closing sleeve  450  is further provided upstream of the opening sleeve  310 . In the initial state, the closing sleeve  450  directly abuts with the opening sleeve  310 , and is connected with the body  100  through a third shear pin  184 . A closing seat  460  is provided at an upper end of the closing sleeve  450 . In a preferred embodiment, as shown in  FIG.  5   , a snap ring  462  is provided on an outer wall of the closing sleeve  450 , and a snap-ring groove  118  that can be in engagement with the snap ring  462  is provided in the inner wall of the body  100 . The specific functions of the closing sleeve  450  and the closing seat  460  as well as the snap ring  462  and the snap-ring groove  118  will be described below. 
     As shown in  FIGS.  1  and  2   , in the initial state, the opening sleeve  310  of the opening assembly  300  is connected with the body  100  through the first shear pin  180 , and thus covers the circulating opening  120 . At the same time, the opening seat  320  of the opening assembly  300  is connected with the opening sleeve  310  through the second shear pin  182 , and thus covers the liquid inlet recess  130 . At this time, the inner chamber  110  of the body  100  is not in communication with the flow channel  230  in the packing valve body  210  of the packer  200 . In this way, the displacing fluid entering the inner chamber  110  of the body  100  during the primary cementing and mud replacing procedure cannot enter the flow channel  230  in the packing valve body  210  of the packer  200 , so that the displacing fluid is physically isolated from the accelerant in the liquid reservoir  240 . 
     As shown in  FIG.  3   , when an opening tool  400  as shown in  FIG.  6    is put into the staged cementing device  100  according to the present invention, the opening tool  400  will be in engagement with the opening seat  320  as moves downward, thereby blocking up the inner chamber  110  of the body  100 . 
     The second shear pin  182  will be sheared off by a pressure build-up in the body  100 , which is referred to herein as “primary pressure build-up”. In this case, the opening tool  400  will move downward together with the opening seat  320 , until the opening seat  320  is received on the receiving seat  330 . At this time, due to the downward movement of the opening seat  320 , the liquid inlet recess  130  will be no longer blocked up by the opening seat  320 , and thus in communication with the inner chamber  110 . In this way, the displacing fluid in the inner chamber  110  can enter the liquid reservoir  240  in the packer rubber  220  through the liquid inlet recess  130  and the flow channel  230  in the packing valve body  210 . Under the action of the hydraulic pressure of the swelling fluid, the packer rubber  220  generates expansion (i.e., the primary expansion) to fit with the borehole wall, thus isolating the annulus into an upper part and a lower part. 
     After that, a further pressure build-up, which is referred to herein as “secondary pressure build-up”, is performed in the body  100 , so that the first shear pin  180  is sheared off. In this case, the opening sleeve  310  is able to move downward relative to the body  100 , until it abuts on the step  215  of the packing valve body  210 , as shown in  FIG.  4   . At this time, the circulating opening  120  is exposed, while the liquid inlet recess  130  is blocked up again by the opening sleeve  310  moving downward, thereby cutting off the communication between the liquid inlet recess  130  and the inner chamber  110  again. In this case, the secondary cementing procedure can be performed. 
     During the secondary cementing procedure, the swelling fluid will be uniformly mixed with the accelerant, and solidified with the packer rubber  220  as a whole. In this case, the secondary expansion of the packer rubber  220  can be achieved. At this time, the closing tool  410  as shown in  FIG.  7    can be put down and a mud replacement can be performed. As shown in  FIG.  5   , when the closing tool  410  falls down onto the closing seat  460  and seals thereon, an upper part of the closing seat  460  forms a closed cavity. At this point, a further pressure build-up, which is referred to herein as “tertiary pressure build-up”, is performed in the body  100  to shear off the third shear pin  184 . In this way, the closing sleeve  450  descends relative to the body  110  and closes the circulating opening  120  again. In this position, the snap ring  462  located on the outer wall of the closing sleeve  450  will enter the snap-ring groove  118  formed in the inner wall of the body  100 . Through the engagement of the snap spring  462  and the snap-spring groove  118 , the backward movement of the closing sleeve  450  can be prevented, thereby realizing permanent closure of the circulating opening  120 . 
     After the completion of the secondary cementing procedure, if hydrocarbon medium, such as oil and gas, enters the annulus during the production, the packer rubber  220  made of hydrocarbon-expandable rubber will absorb the hydrocarbon medium from the well, and thus generate a further expansion (i.e., tertiary expansion). The tertiary expansion can fill tiny gaps, prevent oil, gas and water from flowing upward, and avoid the pressure problem in the annulus. 
     As described above, according to the staged cementing device  100  of the present invention, the packer  200  will not be affected by the pressure in the pipe. The liquid injection channel cannot be opened without the opening tool  400 , thus avoiding accidental opening operation caused by the pressure in the pipe. In addition, after the liquid injection channel is opened, the displacing fluid enters the liquid reservoir  240  of the packer rubber  220 , so that the primary expansion of the packer can be realized through the hydraulic pressure of the swelling liquid, so as to block up the annulus. In this way, after the circulating opening  120  is opened, the liquid column pressure will be reduced, thereby reducing the leakage of the primary cement mud, preventing the leakage of the secondary cement, and thus improving the quality of the well cementation. Moreover, the accelerant in the packer  200  will be chemically reacted with the displacing fluid to be cured in a short time, thus forming into one piece with the packer rubber  220 . In this way, after curing, the packer rubber  220  will not shrink but expand slightly in terms of volume, thereby realizing the secondary expansion of the packer  200 . Therefore, it is possible to avoid the aging and damage of the packer rubber  220 , which may cause the liquid to flow out and eventually lead to the failure of the packer  200 . Further, the packer rubber  220  of the packer  200  is made of hydrocarbon-expansible rubber, which can, on the basis of previous expansions, generate a further expansion (i.e., tertiary expansion) under hydrocarbon medium, such as gas or oil, in the reservoir. This tertiary expansion can fill tiny gaps, thus further improving the long-term sealing ability of the packer. 
     Although the present invention has been described with reference to the preferred embodiments, various modifications may be made and equivalents may be substituted for components thereof without departing from the scope of the present invention. In particular, under the condition that there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any manner. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.