Abstract:
A method for analyzing material wear in a hydrocarbon production environment is disclosed. The method includes the steps of preparing a sample of material to be disposed proximate the hydrocarbon production environment; selecting a placement location for the sample of material, wherein the placement location is in fluid communication with a fluid flow for which the impact of the fluid flow on the sample of material is to be tested; disposing the sample of material in the placement location for a pre-determined amount of time; allowing the sample of material to be exposed to the fluid flow; retrieving the sample of material from the placement location after the pre-determined amount of time has passed; and analyzing the sample of material for wear caused by the hydrocarbon production environment.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a non-provisional application claiming priority to U.S. Provisional Application No. 62/110,346, filed Jan. 30, 2015, which is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    This disclosure relates in general to oil and gas equipment, and to testing materials used in oil and gas equipment for wear. In particular, the disclosure provides systems and methods that accurately assess wear on materials used in oil and gas equipment under varying environmental conditions. 
         [0004]    2. Related Technology 
         [0005]    The American Petroleum Institute requires fatigue analysis on materials exposed to certain environmental conditions when the materials are to be used in oil and gas operations. These operations can include high pressure high temperature (HPHT) operations and subsea operations. However, environmental conditions vary from well to well, and no single analysis can be used to determine the expected lifespan of a given piece of oil and gas equipment. Laboratory scale tests cannot accurately mimic the environment found in harsh hydrocarbon production environments, such as a subsea wellbore, and cannot accurately gauge the expected lifespan of a given piece of oil and gas equipment when exposed to such harsh environments. 
       SUMMARY 
       [0006]    Systems and methods for accurately assessing wear on materials in wellbore environments, including subsea applications, are disclosed. Materials can be installed and exposed to wellbore fluids in racks within one or more unused blowout preventer (BOP) outlets. The sample size of material can vary to assess equipment design life. Material degradation can be measured over time for the particular environmental conditions affecting a sample. For metallic samples, such materials can be connected to wellbore materials that are connected to a system&#39;s cathode protection system. For elastomeric material samples, such samples can be tested against manufacturing material properties and can be analyzed in the wellbore environment to test equipment performance and to establish better life and service recommendations, as well as compound improvements. 
         [0007]    Subsea systems can be protected cathodically by using anodes rated for the environment. Anodes are sized in accordance with industry specifications based on the material grades, surface preparation, surface areas, as well as other factors. The sacrificial anodes are mounted in various locations on a BOP and connected so that they limit degradation in the subsea equipment for the expected design life. 
         [0008]    Therefore, disclosed herein is a method for analyzing material wear in a hydrocarbon production environment. The method includes the steps of: preparing a sample of material to be disposed proximate the hydrocarbon production environment; selecting a placement location for the sample of material, wherein the placement location is in fluid communication with a fluid flow for which the impact of the fluid flow on the sample of material is to be tested; and disposing the sample of material in the placement location for a pre-determined amount of time. The method further includes the steps of allowing the sample of material to be exposed to the fluid flow; retrieving the sample of material from the placement location after the pre-determined amount of time has passed; and analyzing the sample of material for wear caused by the hydrocarbon production environment. 
         [0009]    Additionally disclosed is a monitoring vessel for analyzing material wear in a hydrocarbon production environment. The vessel includes a retainer operable to hold a sample of material to be disposed proximate the hydrocarbon production environment; a fluid flow channel operable to allow a fluid flow through the retainer, for which the impact of the fluid flow on the sample of material is to be tested; and an end cap, wherein the end cap is operable to allow insertion of the sample of material into the retainer, and removal of the sample of material from the retainer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following descriptions, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the disclosure and are therefore not to be considered limiting of the disclosure&#39;s scope as it can admit to other equally effective embodiments. 
           [0011]      FIG. 1  is a representative system overview of a BOP stack. 
           [0012]      FIG. 2A  is a schematic showing a remotely operated vehicle (ROV) accessing a lower marine riser package (LMRP) subsea. 
           [0013]      FIG. 2B  is a schematic showing an enlarged view of the lower stack (LS) from  FIG. 1 . 
           [0014]      FIG. 3  is a cross-sectional schematic representation of a BOP outlet for sample monitoring. 
           [0015]      FIG. 4  is a front-view schematic of stackable retainers with sample materials for monitoring. 
           [0016]      FIG. 5  provides a schematic for insertion of a sample material into a monitoring vessel. 
           [0017]      FIG. 6  provides a schematic of a sample material installed in a stackable retainer, such as that shown in  FIG. 4 , that is preloaded under tension. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    So that the manner in which the features and advantages of the embodiments of systems and methods of condition-based monitoring for materials in wellbore applications, as well as others, which will become apparent, may be understood in more detail, a more particular description of the embodiments of the present disclosure briefly summarized previously may be had by reference to the embodiments thereof, which are illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only various embodiments of the disclosure and are therefore not to be considered limiting of the present disclosure&#39;s scope, as it may include other effective embodiments as well. 
         [0019]    The present technology relates to fatigue analysis and testing of materials used in oil drilling or production equipment. High pressure high temperature (HPHT) well control equipment is required by regulation to undergo fatigue analysis on materials exposed to the environmental conditions at and in the well. Currently, there are no destructive testing procedures available to monitor the material properties while exposed to the environment. The ability to carry out such destructive testing would allow a user to predict the life of the material, and the equipment made of the material, to better predict the life of the equipment, and to ensure that the equipment meets the design requirements in the actual operating service conditions instead of lab conditions. 
         [0020]    Typically, testing of equipment and materials requires that a few conditions are submitted for a baseline analysis, but there is no condition-based monitoring during the service life of the equipment except for non-destructive testing (for pitting and cracks) and hardness testing. This can be problematic because, while equipment may see similar conditions throughout the life of the equipment at a particular well, drilling equipment typically moves from well to well during its life, and conditions at different wells may vary. 
         [0021]    The present technology includes a procedure wherein material sampling vessels are installed in blowout preventers (BOPs), or other oilfield equipment, on site at different wells, and exposed to the well fluids, and also other fluids such as sea water and air, in and around the BOPs. Material can be introduced and removed on a time-based cycle program (e.g., yearly), and the material properties tested to confirm the material is within the design limits prescribed for the equipment. Records during the service conditions can record pressure and temperature cycles as well as fluid properties (mud type, seawater exposure, production fluid exposure with durations) and external loading (riser tension and bending moments) to be evaluated when comparing material compatibility (both metallic and elastomeric). Such a system is advantageous because it better predicts service life of the components under the actual field conditions instead of a lab analysis which cannot accurately simulate environmental conditions for drilling equipment when it is moved from well to well. 
         [0022]    Referring first to  FIG. 1 , a representative system overview of a BOP stack is shown. In  FIG. 1 , a BOP stack  100  is pictured, which includes a lower marine riser package (LMRP)  102  and a lower stack (LS)  104 . LMRP  102  includes an annular  106 , a blue control pod  108 , and a yellow control pod  110 . A hotline  112 , a blue conduit  114 , and a yellow conduit  120  proceed downwardly from a riser  122  into LMRP  102  and through a conduit manifold  124  to control pods  108 ,  110 . A blue power and communications line  116  and a yellow power and communications line  118  proceed to control pods  108 ,  110 , respectively. An LMRP connector  126  connects LMRP  102  to LS  104 . Hydraulically activated wedges  128  and  130  are disposed to suspend connectable hoses or pipes  132 , which can be connected to shuttle panels, such as shuttle panel  134 . 
         [0023]    LS  104  can include shuttle panel  134 , as well as a blind shear ram BOP  136 , a casing shear ram BOP  138 , a first pipe ram  140 , and a second pipe ram  142 . BOP stack  100  is disposed above a wellhead connection  144 . LS  104  can further include optional stack-mounted accumulators  146  containing a necessary amount of hydraulic fluid to operate certain functions within BOP stack  100 . 
         [0024]    Referring now to  FIG. 2A , LMRP  102  from  FIG. 1  is shown as being enlarged, and remotely operated vehicle (ROV)  150  is shown accessing LMRP  102 . ROV  150  is controlled from the surface, and has access arms  152 ,  154 . In  FIG. 2A , LMRP  102  shows monitoring vessels  156 ,  158 , and  160 . Monitoring vessels  156 ,  160  are fluidly coupled to and in fluid communication with production line  162 . Therefore, when drilling fluids and production fluids, such as for example drilling mud, brine, hydrocarbons, oil, natural gas, and condensates, are flowing through production line  162 , such fluids also flow through monitoring vessels  156 ,  160 . Monitoring vessel  158  is coupled to LMRP rack  164 , and is in fluid communication with seawater surrounding BOP stack  100 . 
         [0025]    While monitoring vessels  156 ,  158 , and  160  are shown mounted in certain positions on BOP stack  100 , monitoring vessels could be mounted or located at any point on a BOP stack to assess environmental impacts on a material. Additionally, while monitoring vessels  156 ,  158 , and  160  are shown being used in a subsea application, such monitoring vessels could be used in a land-based wellbore monitoring application in-situ, or in the ground. Monitoring vessels  156 ,  158 , and  160  can represent existing unused outlets on a BOP stack, or can represent monitoring vessels specifically added to a BOP stack to assess environmental impact on materials. Such monitoring vessels can be integrally formed with BOP elements, such as for example production line  162 , or monitoring vessels can be added after the installation of a BOP stack by an ROV, such as ROV  150 . 
         [0026]    ROV  150  with access arms  152 ,  154  can access monitoring vessels  156 ,  158 , and  160  to insert material samples for the properties of the material samples to be assessed over time when exposed to the environmental conditions at the BOP stack  100 . For example, a material sample  155  can be placed within monitoring vessel  160  by ROV  150  for monitoring in the presence of production fluid in production line  162 . Additionally, ROV  150  can add and remove monitoring vessels, such as monitoring vessels  156 ,  158 , and  160 , to and from BOP stack  100 . Monitoring vessels can be attached and removed from BOP stack  100  by any suitable means in the art including welding, bolting, and magnetic coupling. However, as noted, monitoring vessels can also be pre-existing unused outlets on a BOP stack integrally formed with existing elements on the BOP stack. After a material sample has been exposed to an environment for a suitable pre-determined amount of time, the material sample can be retrieved for analysis and testing in a laboratory. 
         [0027]    In some embodiments, monitoring vessels are not ROV retrievable and would be mounted on or in BOP equipment, and when an LMRP and/or lower stack is retrieved to surface, then the samples could be removed and sent in for testing. 
         [0028]    Referring now to  FIG. 2B , a schematic is provided showing an enlarged view of the lower stack (LS) from  FIG. 1 . Monitoring vessels  166 ,  168 ,  170 , and  172  are disposed at particular locations on LS  104 ; however, in other embodiments monitoring vessels could be placed at other locations on LS  104 . Monitoring vessel  166  is fluidly coupled to production line  162  through casing shear ram BOP  138 ; monitoring vessel  168  is fluidly coupled to production line  162  above wellhead connection  144 ; monitoring vessel  170  is fluidly coupled to stack-mounted accumulators  146 ; and monitoring vessel  172  is coupled to LS frame  174 . When drilling fluids and production fluids, such as for example drilling mud, brine, hydrocarbons, oil, natural gas, and condensates, are flowing through production line  162 , such fluids also flow through monitoring vessels  166 ,  168 . A material sample in monitoring vessel  170  can be exposed to hydraulic fluid flow in stack-mounted accumulators  146 . A material sample in monitoring vessel  172  can be exposed to seawater from the environment surrounding BOP stack  100 . 
         [0029]    Referring now to  FIG. 3 , a cross-sectional schematic representation of a BOP outlet for sample testing is provided. BOP outlet  300  serves as a monitoring vessel to assess wear on materials, similar to monitoring vessels  156 ,  158 ,  160 ,  166 ,  168 ,  170 , and  172  shown in  FIGS. 2A and 2B . In some embodiments, a BOP outlet has a diameter of about 3.06 inches. In BOP outlet  300 , a retainer  302  with sample compartments  304  holds sample materials  306 . Sample materials  306  can include any material relevant to hydrocarbon recovery procedures, such as metals and elastomers, which require wear testing and exposure to a hydrocarbon recovery environment. In some embodiments, the material samples tested comprise materials that make up nearby oil and gas equipment, such as for example a BOP. BOP outlet  300  and/or sample materials  306  can be placed by an ROV. Sample materials  306  are exposed to fluids, such as hydrocarbon production fluids or seawater, when sample compartments  304  are fluidly coupled to a flow line or open to the surrounding fluid environment. 
         [0030]    Sample materials, such as sample materials  306 , can be recovered and tested for wear on an agreed upon timeline, such as annually or semi-annually. Lab testing, such as testing for material degradation, can be performed on relevant sample materials, including metals and elastomers, to provide an accurate estimate for the useful life of a material in a specific environment. In some embodiments, testing can be performed proximate a BOP outlet or sample retainer and proximate a hydrocarbon recovery environment. BOP outlet  300  includes a cathodic connection  308  for use with metal samples. In certain embodiments, a cathodic connection such as cathodic connection  308  would be required for use only with metallic samples, and not for use with elastomeric samples. 
         [0031]    Subsea systems are typically protected cathodically by using anodes rated for the environment. Anodes are sized in accordance with industry specifications based on the material grades, surface preparation, surface areas as well as some other factors. The sacrificial anodes are mounted in various locations and connected so that they limit degradation in the subsea equipment for the expected design life. 
         [0032]    Referring now to  FIG. 4 , a front-view schematic of stackable retainers with sample materials for monitoring is provided. In monitoring vessel  400 , stackable retainers  402 ,  404 ,  406 , and  408  hold sample materials  410  in layers between the stackable retainers. Monitoring vessel  400  includes a temperature sensor  412  and a pressure sensor  414  for monitoring, transmitting, and recording pressure and temperature during the time period during which sample materials  410  are exposed to a fluid flowing in between stackable retainers  402 ,  404 ,  406 , and  408 . More or fewer pressure and temperature sensors can be used in other embodiments, and can be placed anywhere suitable for measuring the pressure and temperature, and/or other parameters such as flow rate, in the environment relevant to the sample materials. 
         [0033]    Referring now to  FIG. 5 , a schematic for insertion of a sample material into a monitoring vessel is provided. Monitoring vessel  500  is disposed within a production line wall  502  with end caps  504  and  506 . Material sample  155  can be placed in monitoring vessel  500  by ROV  150  while end cap  506  is open and end cap  504  is closed. Once the material sample  155  is placed in monitoring vessel  500 , end cap  506  can be closed, and end cap  504  can be opened. In this way, the material sample  155  is exposed to production fluid. End caps  504 ,  506  can be opened and closed, in some embodiments, by an ROV, or can be controlled remotely by a user at the surface with either wireless or wired connections. 
         [0034]    In some embodiments, monitoring vessels are not ROV retrievable and would be mounted on or in BOP equipment, and when an LMRP and/or lower stack is retrieved to surface, then the samples could be removed and sent in for testing. 
         [0035]    Referring now to  FIG. 6 , a schematic of a sample material installed in a stackable retainer, such as that shown in  FIG. 4 , that is preloaded under tension is provided. A tension bar  600  provides tension outwardly in the X1 and X2 directions on a material sample  602 . Such tension can also be referred to as a “preload” of tension. Tension bar  600  holds material sample  602  by grips  601 . Some environmental conditions can reduce the ability of a material to handle stress levels, which results in environmental stress corrosion and cracking in tension loads. Such degradation is difficult to replicate in a lab environment. Samples can be preloaded to a varying number of tension loads, and if failure occurs, the strength levels can be correlated to the reduction in material strength while in the environment, and compared to the design limitations and fatigue life of the equipment. Such degradation testing over time while a material sample is under tension can be performed on both metallic and elastomeric materials. 
         [0036]    The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise. 
         [0037]    In the drawings and specification, there have been disclosed embodiments of methods and systems for condition-based monitoring for materials in wellbore applications, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The embodiments of methods and systems have been described in considerable detail with specific reference to these illustrated embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the embodiments of the present disclosure as described in the foregoing specification, and such modifications and changes are to be considered equivalents and part of this disclosure.