Patent Publication Number: US-11649692-B2

Title: System and method for cementing a wellbore

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present disclosure relates to actively monitoring downhole conditions during wellbore cementing operations, and selectively adjusting cementing operations based on data obtained during monitoring. 
     2. Description of Prior Art 
     Hydrocarbons that are produced from subterranean formations typically flow from the formation to surface via wellbores that are drilled from surface and intersect the formation. The wellbores are often lined with a casing string which is usually bonded to the inner surface of the wellbore with a wellbore cement. In addition to anchoring the casing within the wellbore, the cement also isolates adjacent zones within the formation from one another. Without the cement isolating these adjacent zones a potential exists for communication of gaseous formation fluids through cracks and microannuli. This gas communication can cause pressure buildup behind the casing to possibly reduce the hydrocarbon producing potential of the wellbore. 
     Cementing operations typically involve depositing a designated amount of cement slurry into the casing string, forcing the cement slurry through the casing string causing the slurry to exit from a lower end of the casing string and to then flow back up into the annulus between the casing string and walls of the wellbore. A technique used to estimate what amount of cement slurry to deposit into the casing is based on the annulus volume in which the cement is being injected. To force the cement slurry downward through and from the casing string, and then upward in the annulus; a plug is landed on top of the cement slurry column, and pressurized fluid is added into the casing string above the plug to push the plug, and the cement slurry, downward through the casing string. A cement shoe is often provided at the lowermost end of the casing string, and which the plug latches to when it reaches a lower end of the casing string. Temperature downhole where the cement slurry exits the casing string is typically derived from historical data from the field, and values of pressure are generally based on static head calculations. 
     SUMMARY OF THE INVENTION 
     An example method of cementing a wellbore is disclosed and that includes flowing a cement slurry into a casing string that is disposed in the wellbore, urging the cement slurry from an end of the casing string and into an annulus between the casing string and walls of the wellbore, obtaining real time downhole conditions of the cement slurry by monitoring conditions of the cement slurry proximate the end, and adjusting a characteristic of the cement slurry based on the downhole conditions. Examples of conditions include pressure and temperature, and examples of monitoring are inside and outside of a shoe track that is disposed on a lower end of the casing string. In this example and where wherein the conditions are pressure and the method further optionally includes identifying a pressure differential of cement slurry flowing through the shoe track. In an example, the method further includes transmitting acoustic signals uphole that represent the monitored conditions and in an alternative includes evaluating a characteristic of the acoustic signals. A property of the cement slurry based on a characteristic of the acoustic signal and the monitored conditions is optionally performed. The method further includes the option of comparing the monitored conditions to expected conditions, and adjusting a design temperature of the cement slurry when the monitored conditions differ from the expected conditions by an amount that exceeds a designated amount. In an example, determining that the cement slurry has cured into a set cement is based on an evaluation of the real time downhole conditions. An evaluation of the holdup of a column of the cement slurry by the shoe track is optionally based on an evaluation of the real time downhole conditions. Downhole intervention is optionally performed to repair the shoe track when no holdup of the column of the cement slurry by the shoe track is determined. 
     Also disclosed is a system for cementing a wellbore that includes a casing string, a shoe track mounted on an end of the casing string, and that includes a monitoring system that is sensitive to downhole conditions proximate the shoe track, and a means for evaluating that a variance between the downhole conditions and expected conditions exceeds a designated amount, and for identifying an operational adjustment in response to when the variance exceeds the designated amount. An example means is a controller that is in communication with the sensor. The monitoring system optionally has sensors that are inside and outside of the shoe track. The monitoring system alternatively has a sensor that senses the downhole conditions and a transmitter in communication with the sensor. Transmitters are optionally include that are both inside and outside the shoe track. Examples exist where the controller is in communication with the first and second transmitters, and based on a comparison of signals received from the first and second transmitters selectively evaluates characteristics of substances inside the casing string and in an annulus between the casing string and wellbore. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
         FIGS.  1 - 3    are partial side sectional views of example steps of cementing a casing string in a wellbore. 
         FIG.  4    is a side sectional detail view of a portion of the casing string of  FIG.  2   . 
         FIG.  5    is a side sectional view of the portion of  FIG.  4    with set cement formed around the portion. 
     
    
    
     While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF INVENTION 
     The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term “about” includes +/−5% of a cited magnitude. In an embodiment, the term “substantially” includes +/−5% of a cited magnitude, comparison, or description. In an embodiment, usage of the term “generally” includes +/−10% of a cited magnitude. 
     It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. 
     An example of a wellbore cementing operation is shown in a partial side sectional view in  FIG.  1   . In this example, a casing string  10  is shown inserted within a wellbore  12  that is formed within a formation  14 . An example of a cementing system  16  is shown injecting cement slurry  18  inside casing string  10 , and which flows along an axis Ax of casing string  10 . A service truck  20  is included with the cementing system  16  that is shown on surface S and equipped with a pump  22  having a suction side in fluid communication with a reservoir  24 , and a discharge side connected to a line  26 . An end of line  26  opposite pump  22  connects to a cement head  28  shown coupled to a wellhead assembly  30 , which in an example provides pressure control of and access into wellbore  12 . Further in this example, casing string  10  has an upper end in fluid communication with cement head  28  through wellhead assembly  30 , and is supported on its upper end to wellhead assembly  30  by hangers (not shown). A derrick  32  is illustrated mounted on surface S over wellhead assembly  30 , and which alternatively provides a framework for mounting the hardware used in the cementing operation. 
     Cementing system  16  of  FIG.  1    includes a controller  34  and a communication means  36  for communicating with controller  34 . As will be described in more detail below, in an embodiment controller  34  includes logics for performing calculations, for evaluating operations, and actions to be taken based upon the evaluated and monitored conditions. Optional vessels  38 ,  40  are schematically represented in communication with slurry reservoir  24  on service truck  20  via lines  42 ,  43 . In one example vessel  38  contains liquid constituents of the cement slurry  18 , such as water, and vessel  40  contains solid constituents of the cement slurry  18  (or vice versa), such as but not limited to Portland cement, silica, silicates and the like. Optionally, vessel  38  contains a typical cement slurry  18  and vessel  40  contains additives (or vice versa), such as but not limited to additives for changing design temperature of the cement slurry  18 , additives for changing design pressure of the cement slurry  18 , agents for accelerating or slowing the rate of curing, additives for mitigating fluid loss, and the like. In a non-limiting example, valves  44 ,  45  within lines  42 ,  43  are selectively operated to adjust the compositional makeup of the cement slurry  18 , such as when vessels  38 ,  40  contain constituents of the cement slurry  18 . In another example, valves  44 ,  45  within lines  42 ,  43  are selectively operated to adjust characteristics or properties of the cement slurry  18 , such as when one of the vessels  38 ,  40  contains an additive. In further embodiments additional vessels are included for storing and the selective dispersal of additives and/or constituents of cement slurry  18 . 
     Still referring to  FIG.  1   , in the example step of cementing illustrated a plug  46  is shown on a lower end of a column of cement slurry  18  inside casing string  10 . Plug  46  operates as a barrier between the cement slurry  18  and an amount of spacer fluid  48  below plug  46  and between drilling fluid  50  that is within casing string  10 . Urging the cement slurry  18  downward within casing string  10  pushes the drilling fluid  50  from within casing string  10  and out into an annulus  52  between casing string  10  and walls of wellbore  12 . A subsequent step of the example cementing operation is shown in  FIG.  2    and where the designated amount of the cement slurry  18  has been directed into casing string  10 , and inserted into casing string  10  is an upper plug  54  shown disposed on an upper end of the column of the cement slurry  18 . A displacement fluid  56  is illustrated on top of the upper plug  54 , which similarly to previous steps of the operation is pressurized to urge the upper plug  54  and cement slurry  18  downward within casing string  10 . As shown in  FIG.  2    lower plug  46  is depicted having been pushed into engagement with a shoe track  58 . In the example of  FIG.  2    shoe track  58  makes up a lowermost portion of casing string  10 . 
     Referring now to  FIG.  3   , an orifice  59  is shown extending axially through lower plug  46 ; which is formed by applying pressure to lower plug  46  above a set pressure at which a frangible section in plug  46  ruptures. Forming the orifice  59  through the lower plug  46  allows cement slurry  18  between plugs  54 ,  46  to flow past the lower plug  46 , out from the bottom end of casing string  10 , and out into the annulus  52 . 
     A detailed example portion of casing string  10  is shown in side sectional view in  FIG.  4    where cement slurry  18  is illustrated being forced outward from the bottom end of the shoe track  58 . In this example, shoe track  58  is shown having a float collar  60  on which the lower plug  46  is landed and float shoe  62  proximate a lower end of the shoe track  58 . Examples of centralizers  64 ,  66  are shown optionally provided along out surfaces of the shoe track  58 , centralizers  64 ,  66  are respectively disposed adjacent the float collar  60  and float shoe  62 ; in an alternative an axis A Y  of shoe track  58  is aligned with an axis of wellbore  12  by centralizers  64 ,  66 . In the illustrated embodiment, an example of a check valve assembly  68  is depicted within the float collar  60  and which includes a body  70  within the housing of float collar  60 . As illustrated by arrows A, cement slurry  18  flows from casing string  10  into shoe track  58  and into orifice  59  of lower plug  46 . An axial passage  72  inside body  70  provides a way for the cement slurry  18  to flow through the body  70  and downward to the float shoe  62 . A plug member  74  is axially moveable within passage  72 , and that allows flow in a downward direction from float collar  60  to float shoe  62 , and as described in more detail below becomes a barrier to upward flow inside the shoe track  58  in a direction from float shoe  62  to float collar  60 . In the example shown float shoe  62  includes an inner body  76  having a chamber  78  formed within that is in communication with the inside of shoe track  58  upstream of float shoe  62 . A lower port  80  and side port  82  extend through the inner body  76  that provide communication between chamber  78  and annulus  52 , so that the inside of the shoe track  58  is in communication with the annulus  52 . In this example, the flow of the cement slurry  18  as represented by arrows A illustrates the slurry flowing through the passage  72 , and exiting from within the shoe track  58  via ports  80 ,  82 . 
     A sensor sub  84  is included with the example shoe track  58  and shown disposed axially between the float collar  60  and float shoe  62 . An annular space  85  inside of sensor sub  84  is in communication with float collar  60  and float shoe  62 , and cement slurry  18  flowing downward from float collar  60  flows through annular space  85  on its way to float shoe  62 . Sensor sub  84  of  FIG.  4    is equipped with inner sensors  86   1,2  and outer sensors  88   1,2 ; where inner sensors  86   1,2  are shown mounted to an inner sidewall of the sensor sub  84  and within annular space  85 , and outer sensors  88   1,2  are illustrated mounted to an outer surface of the sensor sub  84  and within annulus  52 . In a non-limiting example, inner sensors  86   1,2  sense conditions within annular space  85  and outer sensors  88   1,2  sense conditions within annulus  52 . Embodiments exist where conditions within the annular space  85  are the same or substantially the same as conditions within the remaining portions of the shoe track  58 . Example downhole conditions monitored by the sensors  86   1,2 ,  88   1,2  include temperature and pressure, alternatives exist where the conditions monitored by sensors  86   1,2 ,  88   1,2  represent conditions of the cement slurry  18  inside shoe track  58  and also inside annulus  52 . 
     Further shown in the example of  FIG.  4    are inner and outer transmitters  90 ,  92 . Inner transmitter  90  is illustrated disposed inside of the sensor sub  84 , and outer transmitter  92  is depicted in the annulus  52  and outside of sensor sub  84 . Schematically shown are communication means  94  between inner sensors  86   1,2  and outer sensors  88   1,2  and with each of the transmitters  90 ,  92 . In the example shown, the communication means  94  is a communication line that optionally is made up of media that conducts electromagnetic energy; such as metal wire, or media transmissive by electromagnetic energy, such as fiber optics. In additional embodiments communication means is via wireless telemetry, such as electromagnetic and/or acoustic. Communication lines  96 ,  98  are provided that connect respectively with transmitters  90 ,  92  and that in one example provide a communication means between the transmitters  90 ,  92  and surface S ( FIG.  1   ). Alternatively, as depicted by the acoustic signals  100 ,  102  communication between the transmitters  90 ,  92  and surface S takes place acoustically in the form of these signals. Optionally, the signals both in the lines  96 ,  98  and the acoustic signals  100 ,  102  are representative of the conditions monitored downhole by the sensors  86   1,2 ,  88   1,2  so that conditions within shoe track  58  and annulus  52  are available at surface S via communication between sensors  86   1,2 ,  88   1,2 , transmitters  90 ,  92 , and surface S. 
     In a non-limiting example of operation, signals are transmitted uphole and to controller  34  ( FIG.  1   ) via transmitters  90 ,  92  and one or more of communication means  94 ,  96   98 ,  100 ,  102 , and where the signals directly represent downhole conditions monitored by the sensors  86   1,2 ,  88   1,2 , or include data representing the conditions. An evaluation of the downhole conditions is performed and the downhole conditions are compared to expected conditions downhole. Expected conditions in one example are from historical data which is that available from a temperature gradient and optionally also pressure data which is estimated based upon static head of the fluids within the wellbore  12 , in one example fluids whose static head values are estimated include drilling mud  50 , spacer fluid  48 , cement slurry  18 , displacement fluid  56  and combinations thereof. In a further example, if variances between the measured downhole conditions and the expected conditions exceed a designated value, subsequent remedial action is taken to address the situations. In one example of a remedial action the constituents of the cement slurry  18  are adjusted so that a design condition of the cement slurry  18  exceeds that of the monitored downhole conditions. In an alternative, pressure drop through the shoe track  58  is optionally obtained by comparison of the downhole conditions monitored by the sensors  86   1,2 , versus that of sensors  88   1,2 . 
     Referring now to  FIG.  5    shown is an example step of the cementing operations described herein, and where the cement slurry  18  of  FIG.  4    has cured into a set cement  104  within annulus  52  and inside of a portion of shoe track  58  below float collar  60 . In this example, the presence of the set cement  104  is detectable with an evaluation of the pressure downhole and which is sensed by the sensors  86   1,2 ,  88   1,2  and transmitted uphole by transmitters  90 ,  92 . In a further example, acoustic signals  100 ,  102  generated by transmitters  90 ,  92  are received on surface S and where values of conditions monitored downhole by sensors  86   1,2 ,  88   1,2  are extracted. Optionally, signals  100 ,  102  are analyzed, and characteristic(s) of the signals obtained from the analysis provides information about the cement slurry  18  or set cement  104 . Example characteristic(s) include speed, attenuation, and travel time, which in certain embodiments vary dependent upon the medium in which the signals  100 ,  102  are being transmitted. In an embodiment, the values of downhole conditions obtained from the data embedded in the signals is further conditioned or adjusted based on the characteristic(s) of the signals analyzed. In yet another example, information about a quality of the set cement  104  is obtained by an analysis of the signals  100 ,  102  and their characteristic(s). In a non-limiting example, an analysis of changes in the characteristic(s) of the signals  100 ,  102  over time is performed that indicates when the cement slurry  18  has cured into set cement  104 . 
     Still referring to  FIG.  5    shown is that the plug member  74  is moved into a smaller cross-sectional area of passage  72  and which blocks fluid flow uphole through the float collar  60 . In an alternative, a transmitter receiver device  106  is shown mounted within wellhead assembly  30  of  FIG.  1   , and which is in communication with transmitters  90 ,  92  or optionally directly within sensors  86   1,2 ,  88   1,2  and via repeater (not shown) disposed within or along outside of casing string  10  and that deliver signals to the receiver transmitter  106 . In one alternative, the combination of the sensors  86   1,2 ,  88   1,2  transmitters  90 ,  92  communication means  94 , communication lines  96 ,  98  and receiver transmitter  106  define an example of a monitoring system  108 . 
     Advantages provided by this disclosure include addressing concerns surrounding the shoe track  58  before, during, and after cementing operations. Having accurate temperature values proximate the shoe track  58  enables adjustment of design temperatures of the cement slurry  18  and set cement  104  by introducing additives; and which provides an alternative in examples when the measured temperature around the shoe track  58  differs from a temperature based on a common temperature gradient for the field that was historically gathered through some common temperature logs run in the field. In an example, values of pressure sensed around the shoe track  58  are compared with theoretical planned pressures; which provides an option of adjusting operations should these values differ. The ability to adjust composition of the cement slurry  18  based on actual sensing of downhole conditions increases the likelihood that the set cement  104  meets or exceeds design values and functionality. A further advantage provided includes the availability of wait on cement (“WOC”) times between stages in case of multi stage cementing operations and wet shoe track issues by sensing the internal pressure across the shoe track  58 , as pressure exerted by the set cement  104  is expected to be less than that exerted by the cement slurry  18  in the annulus  52 . Also the height of the column of cement slurry  18  in the annulus  52  is readily obtained by the real time pressure measurements. Advantages also include confirming that the equipment in the shoe track  58  is holding (i.e. preventing a back flow of cement slurry  18  from annulus  52  back into shoe track  58 ) after bleeding off pressures at the end of the cementing operations. 
     The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.