Patent Publication Number: US-2015088425-A1

Title: System, Method &amp; Computer Program Product to Simulate the Progressive Failure of Rupture Disks in Downhole Environments

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to downhole simulators and, more specifically, to a system to simulate and report progressive failures of rupture disks along a wellbore due to trapped annular pressure. 
     BACKGROUND 
     Traditionally, rupture disks have been utilized to combat annular pressure increases in downhole environments. Rupture disks mitigate the effects of increased annular pressure by failing at a specified pressure increment, thus allowing fluid flow between the annuli separated by the burst disc, which will then reduce the annulus pressure. This reduced pressure is intended to prevent damage to the well completion caused by the annulus pressure build up. If multiple rupture discs are used in the well completion design, there is the potential for progressive failures if the pressure redistribution caused by the failed rupture disk, in turn, causes additional failures of other rupture disks. 
     However, to date, the prior art has failed to produce a system to analyze, predict and report the progressive failures of rupture disks. Accordingly, there exists a need in the art for a systematic analysis that predicts and models progressive rupture disks failures, thereby providing the ability to reconfigure completion designs to avoid such failures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a block diagram of a progressive failure analysis system according to an exemplary embodiment of the present invention; 
         FIGS. 2A &amp; 2B  are flow charts illustrating data flow associated with an exemplary methodology of the present invention; and 
         FIG. 3  is a screen shot of an interface having various wellbore configuration windows according to an exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Illustrative embodiments and related methodologies of the present invention are described below as they might be employed in a system to simulate and report progressive failures of rupture disks along a wellbore due to trapped annular pressure. In the interest of clarity, not all features of an actual implementation or methodology are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. Further aspects and advantages of the various embodiments and related methodologies of the invention will become apparent from consideration of the following description and drawings. 
       FIG. 1  shows a block diagram of progressive failure analysis system  100  according to an exemplary embodiment of the present invention. In one embodiment, progressive failure analysis system  100  includes at least one processor  102 , a non-transitory, computer-readable storage  104 , transceiver/network communication module  105 , optional I/O devices  106 , and an optional display  108 , all interconnected via a system bus  109 . Software instructions executable by the processor  102  for implementing software instructions stored within progressive failure simulator  110  in accordance with the exemplary embodiments described herein, may be stored in storage  104  or some other computer-readable medium. 
     Although not explicitly shown in  FIG. 1 , it will be recognized that progressive failure analysis system  100  may be connected to one or more public and/or private networks via appropriate network connections. It will also be recognized that the software instructions comprising progressive failure simulator  110  may also be loaded into storage  104  from a CD-ROM or other appropriate storage media via wired or wireless means. 
       FIG. 1  further illustrates a block diagram of progressive failure simulator  110  according to an exemplary embodiment of the present invention. As will be described below, progressive failure simulator  110  comprises drilling prediction module  112 , production prediction module  114 , casing stress module  116 , tubing stress module  118 , multi-string module  120 , and a progressive failure module  122 . Based upon the input variables as described below, the algorithms of the various modules combine to formulate the progressive failure analysis of the present invention. 
     Drilling prediction module  112  simulates, or models, drilling events and the associated well characteristics such as the drilling temperature and pressure conditions present downhole during logging, trip pipe, casing, and cementing operations. Production prediction module  114  models production events and the associated well characteristics such as the production temperature and pressure conditions present downhole during circulation, production, and injection operations. Casing stress module  116  models the stresses caused by changes from the initial to final loads on the casing, as well as the temperature and pressure conditions affecting the casing. 
     Tubing stress module  118  simulates the stresses caused by changes from the initial to final loads on the tubing, as well as the temperature and pressure conditions affecting the tubing. The modeled data received from the foregoing modules is then fed into multi-string module  120  which analyzes and then models the annular fluid expansion and wellhead movement present in a system defined by the original input variables. Thereafter, the data modeled in multi-string module  120  is then fed into progressive failure module  122 , which analyzes and reports the progressive failure of rupture disks in response to trapped annular pressure. Persons ordinarily skilled in the art having the benefit of this disclosure realize there are a variety modeling algorithms that could be employed to achieve the results of the foregoing modules. 
       FIGS. 2A &amp; 2B  illustrate the data flow of progressive failure analysis system  100  according to an exemplary methodology of the present invention. At step  200 , the mechanical configuration of the well is defined using manual or automated means. For example, a user may input the well variables via I/O device  106  and display  108 . However, the variables may also be received via network communication module  105  or called from memory by processor  102 . In this exemplary embodiment, the input variables define the well configuration such as, for example, number of strings, casing and hole dimensions, fluids behind each string, cement types, and undisturbed static downhole temperatures. As will be described below, this configuration data also includes data related to rupture disks utilized in the well completion. Based upon these input variables, at step  202 , using drilling prediction module  112 , processor  102  models the temperature and pressure conditions present during drilling, logging, trip pipe, casing, and cementing operations. At step  204 , processor  102  then outputs the initial drilling temperature and pressure of the wellbore. 
     Further referring to  FIG. 2A , at step  206 , processor  102  outputs the “final” drilling temperature and pressure. Here, “final” can also refer to the current drilling temperature and pressure of the wellbore if the present invention is being utilized to analyze the wellbore in real time. If this is the case, the “final” temperature and pressure will be the current temperature and pressure of the wellbore during that particular stage of downhole operation sought to be simulated. Moreover, the present invention could be utilized to model a certain stage of the drilling or other operation. If so, the selected operational stage would dictate the “final” temperature and pressure. 
     The initial and final drilling temperature and pressure values are then fed into casing stress module  116 , where processor  102  simulates the stresses on the casing strings caused by changes from the initial to final loads, as well as the temperature and pressure conditions affecting those casing strings, at step  208 . At step  210 , processor  102  then outputs the initial casing mechanical landing loading conditions to multi-string module  120  (step  216 ). Referring back to step  200 , the inputted well configuration data may also be fed directly to multi-string module  120  (step  216 ). In addition, back at step  204 , the initial drilling temperature and pressure data can be fed directly into multi-string module  120  (step  216 ). 
     Still referring to the exemplary methodology of  FIG. 2A , back at step  202 , processor  102  has modeled the drilling temperature and pressure conditions present during drilling, logging, trip pipe, casing, and cementing operations. Thereafter, at step  212 , these variables are fed into production prediction module  114 , where processor  102  simulates production temperature and pressure conditions during operations such as circulation, production, and injection operations. At step  214 , processor determines the final production temperature and pressure based upon the analysis at step  212 , and this data is then fed into multi-string module  120  at step  216 . 
     Referring back to step  212 , after the production temperature and pressure conditions have been modeled, the data is fed into tubing stress module  118  at step  226 . Here, processor  102  simulates the tubing stresses caused by changes from the initial to final loads, as well as the temperature and pressure conditions affecting the stress state of the tubing. Thereafter, at step  220 , processor  102  outputs the initial tubing mechanical landing loading conditions, and this data is fed into multi-string module  120  (step  216 ). At step  216 , now that all necessary data has been fed into multi-string module  120 , the final (or most current) well system analysis and simulation is performed by processor  102  in order to determine the annular fluid expansion (i.e., trapped annular pressures) and wellhead movement. 
     Thereafter, at step  222 , processor  102  performs a progressive failure analysis of the wellbore (using progressive failure module  122 ) as defined by the data received from multi-string module  120 . Here, taking into account defined rupture disk data, progressive failure module  122  will analyze and simulate the annular fluid expansion (i.e., trapped annular pressure), and any associated rupture disk failures, over the life of the defined wellbore. Accordingly, the exemplary methodology illustrated in  FIGS. 2A &amp; 2B  are used to simulate and report progressive rupture disk failures, even in real-time through linkage of final thermal operating conditions to the desired downhole event. 
     The logic flow of progressive failure module  122  will now be briefly summarized, as would be readily understood by persons ordinarily skilled in the art having the benefit of this disclosure. In general, the present invention achieves this by determining a set of annuli pressures that equalize the fluid volume change in a given annuls to the annulus volume change due to well deformation. While the change in fluid volume depends only on the fluid pressure, the annulus volume is influenced by all the pressures changes in all of the annuli. As a result, change of pressure in a given annulus affects pressures in all other annuli. 
     As a result of this interaction, in a multiple rupture disc system, the failure of one disc will alter the annulus pressures, which may result in further disc failures. Thus, the proper analysis is progressive, i.e. the failure of one disc alters the annulus pressure, possibly resulting in the failure of a second rupture disc. Processor  102 , via progressive failure module  122 , continues this process until either all discs have failed or no further disc failure is predicted. Moreover, other types of failures, such a formation fracturing, are also analyzed as part of the overall analysis. 
     As would be understood by one ordinarily skilled in the art having the benefit of this disclosure, the failure of a rupture disc implies two effects. First, the pressures in the two annuli connected by the burst disc are equilibrated. Second, fluid may flow from one annulus to the other. The second effect does not need to be explicitly calculated because the new equilibrium pressure criterion is that the sum of the fluid volume changes for the two annuli must equal the change in volume of the two annuli. By summing the two effects, the flow between annuli is canceled out of the equations. 
     Now, referring to  FIGS. 2A &amp; 2B , an exemplary methodology of the logic flow of progressive failure module  122  will now be described. At step  221 , multi-string module  120  outputs the multi-string data that includes the final (or most current) well system data, including the annular fluid expansion and wellhead movement data. At step  222   a,  processor  102  determines the annular pressure buildup (“APB”) of all annuli of the well completion. 
     At step  222   b,  processor  102  then analyzes all defined rupture disks, simulates failure scenarios, and determines a list of possible rupture disk failures that may occur over the life of the well. To summarize the logic utilized by processor  102  to achieve this, for internal pressure Pi&gt;external pressure Po, rupture disc failure is defined when Pi&gt;Po+Pr, where Pr is the rupture disc pressure. Similarly, if Po&gt;Pi, rupture disc failure is defined when Po&gt;Pi+Pr. Applying this logic, processor  102  computes a list of rupture disk failures. 
     At step  222   c,  processor  102  then assigns failure criterion to each rupture disk based upon the analysis of step  222   b.  Assuming rupture disk failure is predicted, the failure criterion applied by processor  102  is |Po−Pi|//Pr. Thereafter, processor  102  identifies the rupture disk having the highest failure criterion (i.e., the highest probability of failure). 
     At step  222   d,  processor  102  recalculates the APB. However, in this calculation, processor  102  assumes the identified rupture disk (having the highest failure criterion) has actually ruptured and, thus, performs the calculation with the annuli connected by the failed rupture disk. At step  222   e,  processor  102  then performs another simulation of the well to determine whether any further rupture disk failures are predicted. If the determination is “yes”, the algorithm loops back to step  222   b,  and processor  102  performs the analysis again, with the assumption that the previously identified failed rupture disk has failed. If the answer is “no” at step  222   e,  processor outputs the report at step  224 . In this exemplary embodiment, the report, which may be provided in textual or graphical format, lists the rupture discs in the order of failure and the resulting final annulus pressures. 
       FIG. 3  illustrates a user interface  300  utilized to defined wellbore and rupture disk characteristics according to an exemplary embodiment of the present invention. At step  200 , user interface  300  is displayed on display  108 . In window  302 , a list of user-specified string characteristics are displayed. Windows  304  and  306  are used to define initial conditions and annulus options, respectively. In window  308 , the well configuration is defined to include any number of rupture disks per string and their respective depths, burst ratings, and collapse ratings. A vented or unvented annulus  311  may also be defined. Lastly, window  312  allows definition of the final conditions such as, for example, a production operation and a corresponding time period. After the well configuration has been defined via interface  300 , progressive failure analysis system  100  simulates the effects that one or more failed rupture disks would have on the APB over the specified life of the well. 
     As described above, the present invention allows definition of wellbore and rupture disk and analysis of progressive failures that may occur over the life of the well. Although not described herein, other mitigation techniques, such as the use of syntactic foam, may be modeled using the present invention, as would be understood by persons ordinarily skilled in the art having the benefit of this disclosure. In this instance, the present invention would perform the progressive failure analysis described herein while taking into account the other defined mitigation data. 
     Accordingly, exemplary embodiments of the present invention may be utilized to conduct a total well system analysis during the design phase or in real-time. It can also be used to analyze the influence that progressive failure of rupture disks would have on the thermal expansion of annulus fluids, and/or the influence of loads imparted on the wellhead during the life of the well, as well as the load effects on the integrity of a well&#39;s tubulars. Accordingly, the load pressures and associated wellhead displacement values are used to determine the integrity of a defined set of tubulars and rupture disks in the completed well or during drilling operations. 
     Although various embodiments and methodologies have been shown and described, the invention is not limited to such embodiments and methodologies and will be understood to include all modifications and variations as would be apparent to one skilled in the art. For example, the present invention may also determine alternative well completion designs in the event that rupture disk failures are determined. Therefore, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.