Abstract:
A method of pressure testing a lower marine riser package includes forming an inflatable packer having exposed slats and an inflatable packer element. The packer is positioned within the lower marine riser package above the cap seal with the exposed slats above the packer element. The packer is inflated and fluid pressure is then applied to test the integrity of the cap seal. The packer may be inverted, then positioned below the BOP/riser connection, the packer inflated, and pressure increased above the inflated packer element to test the fluid integrity of the BOP/riser connection.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method of pressure testing a lower marine riser package including a BOP/riser connection and a cap seal. More particularly, the present invention relates to the method of testing the lower marine riser package prior to installation of the subsea package. 
       BACKGROUND OF THE INVENTION 
       [0002]    It has been widely accepted amongst those in the oil and gas industry that the era of easily available, “cheap” energy is over. In order to meet rapidly growing demand, it is becoming more and more necessary to move offshore in the search for conventional oil and gas plays. Since the feasibility of a well&#39;s production is driven largely by economic, rather than technical factors, it is very important to control costs as much as possible. 
         [0003]    With the oil and gas industry increasingly looking for energy offshore, there will be increased costs associated with the complexity of drilling below the ocean floor in deeper water. A leak detected after latching the lower marine riser package (LMRP) in deep water can cost the rig and the energy producer up to a $12 million in lost time. There is a need to be able to test the BOP/riser connection and cap seal for pressure integrity at surface before the operator runs to depth with the LMRP. 
       SUMMARY OF THE INVENTION 
       [0004]    A procedure is disclosed to test at surface for leaks inside the lower marine riser package, and primarily the cap seal (annular seal) at the lower marine riser package and the BOP/riser connection. All connections may be tested offline and do not interfere with drilling operations. The method is safe and economical since it uses field proven equipment and can be performed in a short time interval. A closed system is created in a BOP of the lower marine riser package using an external inflate (El) tool. 
         [0005]    The tool may be inflated insider the BOP above the cap seal. Pressure is then applied from below the tool to test this seal&#39;s integrity. The tool may then be inverted and placed higher up in the BOP in order to test any of the BOP/riser connections. In either position, by observing the applied pressure, it is possible to confirm the presence or absence of a leak, as well as its location. If testing detects the presence of a leak, the cause for the leak may be economically corrected. 
         [0006]    In one embodiment, a method of pressure testing a lower marine riser package prior to installation in a subsea well includes forming an inflatable packer having an inflate port external to a packer mandrel, and having exposed slats and an inflatable packer element axially spaced from the exposed slats. 
         [0007]    The packer may be lowered within the lower marine riser package to a position above the cap seal, with the exposed slats above the inflatable packer element. The packer may then be inflated against the internal well of the lower marine riser package above the cap seal, and fluid pressure increased below the inflated packer to test fluid integrity of the cap seal. The packer may also be lowered to a position below the BOP/riser connection, with the exposed slats below the inflatable packer element. The packer may be inflated against the internal wall of the lower marine riser package below the BOP/riser connection to set the packer. Pressure may be increased above the inflatable packer element to test fluid integrity of the BOP/riser connection. 
         [0008]    These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a side view of a tool configured for testing the fluid integrity of the cap seal. 
           [0010]      FIG. 2  is a side view of the tool configured for testing the BOP/riser connection. 
           [0011]      FIG. 3  is a cross-sectional view of the pup joint generally shown in  FIG. 1 . 
           [0012]      FIG. 4  is a pictorial view of the tool positioned for testing the annular cap seal of the lower marine riser installation. 
           [0013]      FIG. 5  is a pictorial view of the tool positioned for testing a BOP/riser connection. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0014]    The cap seal and the BOP/riser connection of a lower marine riser package may be tested according to this invention “offline”, e.g., at the moon pool. If a cost of $1 million/day is assumed for not only the rig but also the production company (standby time for personnel and equipment, for instance), it can cost a rig up to $12 million to correct a leak detected at the seabed (4 days to get to bottom, 4 days to pull riser, and another 4 days to go back down). 
         [0015]    The simplicity of the lower marine riser package test at surface lies in the short list of equipment used before the package is lowered subsea, as shown in  FIG. 4 :
       7″×14½″ external inflate (El tool)  10     Stainless steel inflate lines  20  with pressure gauges  22     Rig Pump  30     Lower marine riser package  60 , typically including BOP  62 , annular cap seal  64 , flex joint  66 , and riser adapter  68         
 
         [0020]    A similar external inflate tool has been used extensively in applications presenting IDs of from 16″ to 30″, as a bridge plug, casing hole finder, and on cement squeeze jobs. 
         [0021]    These are two distinct parts of the external inflate (El) tool. As shown in  FIG. 1 , the metal anchoring slats  12  are provided at one end. Due to the metal-to-metal slat/BOP ID contact, these slats act like “slips” or grippers when the element is inflated. Below the slats is the rubber seal element  14 . This rubber element does provide some measure of holding force, although its main purpose is to create a seal within the BOP. 
         [0022]    Providing a tool which uses an inflatable sealing element has significant advantages compared to other types of sealing techniques. The inflatable element is particularly well-suited for reliable sealing with different sized internal bores and different internal ID profiles. Lower mariner riser packages commonly have a central bore which may vary in diameter from about 16 inches to about 22 inches. The same inflatable element is able to reliably seal with the bore of marine riser packages which are manufactured by different companies and typically have different diameters. Also, the inflatable tool may be reliably anchored within the lower marine riser package in order to conduct a pressure test using the exposed slats discussed above. The tool may be positioned, inserted and inflated, and a pressure test conducted in a relatively short time period. Additional inflate ports may be provided compared to a conventional packer, with ports provided the upper end of the tool regardless of whether the tool is inverted. Also, additional ports may be provided at each end to decrease the time required to inflate the packer element. 
         [0023]    Since this test deals with high pressure applied to a large piston area, it is necessary to take measures to conduct the test safely. The external inflate packer has a long service history, and its behavior is highly predictable. Although pressure tests may present safety concerns, the proven nature of the tool combined with the observed safety precautions mitigated many of these concerns. 
         [0024]    In addition to not requiring much equipment, each test case (slats up or slats down) is extremely simple to carry out, as illustrated by the following test programs. 
       Test 1: Slats Up, Testing Cap Seal 
       [0025]    1. Install packer  11  with slats  12  upward and crossover to work string, for instance: 
         [0026]    a) Drillpipe with lifting pup 
         [0027]    b) Crane with lifting strap 
         [0028]    2. Install inflation tubing in connection on top of packer. 
         [0029]    3. Run packer  11  into BOP above cap seal  64 ; route inflation line  20  from fitting  18  at the top of the packer to the packer inflation pump  30 . 
         [0030]    4. With packer at proper set depth, install pressure gauge  22  and shut off valve  24  to inflate line. See  FIGS. 2 and 4 . 
         [0031]    5. Connect inflate line  20  to pump  30 . Slowly inflate packer to a predetermined pressure, based on: 
         [0032]    a) BOP ID 
         [0033]    b) Desired test pressure 
         [0000]    The combination of inflate/test pressures for a given BOP ID may be listed in a set of charts. 
         [0034]    6. Hold pressure for an amount of time determined by the rig operator, and ensure no pressure fall off is seen during test. 
         [0035]    7. To release packer, bleed off applied pressure, open shut off valve to allow packer to fully deflate. 
         [0036]    A lifting eye  70  is provided at the upper end of the mandrel for manipulating the tool in place. 
       Test 2: Slats Down, Testing Bop/Riser Connection 
       [0037]    1. Install packer  11  with slats downward  12  and crossover to work string, for instance: 
         [0038]    a) Drillpipe with lifting pup 
         [0039]    b) Crane with lifting strap 
         [0040]    2. Install inflation tubing in connection on top of packer. For this, a feed through control line pup joint  40  is used. 
         [0041]    3. Run packer into BOP below annular seal  64 . The packer  11  may conveniently be positioned below the lower annular BOP  74  and below the riser connector  76 . Route inflation line from the top of the feed through sub  40  to fitting  42  and flowline  44 . The lower end of this line may be connected to fitting  18  at the top of the packer, as shown in  FIG. 3 . The correct space out of feed through control line pup joint  40  may be ensured in this manner. The tool rests on the partially closed rams  72 , and flow port  46  in sub  40  for pressurizing the annulus above the set packer. 
         [0042]    4. With packer at proper set depth, install pressure gauge  22  and shut off valve  24  to inflate line. 
         [0043]    5. Connect inflate line to pump  30 . Slowly inflate packer to predetermined pressure, based on: 
         [0044]    c) BOP ID 
         [0045]    d) Desired test pressure 
         [0000]    The combination of inflate/test pressures for a given BOP ID is listed in the charts. 
         [0046]    6. Hold pressure for an amount of time determined by the rig operator, and ensure no pressure fall off is seen during test. 
         [0047]    7. To release packer, bleed off applied pressure, open shut off valve to allow packer to fully deflate. 
         [0000]    This test was performed several times, and each time the inflate pressure, and that applied below the tool were varied, as summarized in the following table. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE I 
               
               
                   
                   
               
               
                   
                 Inflate Pressure (psi) 
                 Pressure Applied Below Tool (psi) 
               
               
                   
                   
               
             
             
               
                   
                 1500 
                 1000 
               
               
                   
                 1800 
                 1500 
               
               
                   
                 2000 
                 1800 
               
               
                   
                   
               
             
          
         
       
     
         [0048]    The readings for pressure applied below the tool were taken when the packer movement was observed. At this point, the inflate pressure was increased, and pressure was reapplied below until the packer again started to slide. 
         [0049]    This posed the only significant safety issue: the possibility of the packer being ejected from the BOP due to the very large piston area on which the applied force acted. However, when slight packer movement upwards was observed, the pressure at this point was escaping between the packer and the BOP ID, allowing the system to bleed itself back to equilibrium (and keep the packer in the BOP). In addition, the volume underneath the packer was not large enough to provide for a catastrophic failure. Finally, since pressure was being increased gradually, the risk of a sudden, catastrophic failure was mitigated. 
       Test Findings 
       [0050]    Four test runs were conducted, and the results were highly conclusive. 
         [0051]    Test 1: Inflated tool to 1500 psi and applied 1000 psi pressure below. 
         [0052]    Result: Leak detected at lower flange. Since the very purpose of the test was to detect leaks at the BOP/riser connection, the first run proved very successful. After the flange bolts were tightened, test run  2  was initiated. 
         [0053]    Test 2: Again inflated tool to 1500 psi and applied 1000 psi of pressure under the tool. The goal here was to see if the packer would hold pressure, thus confirming that the leak had indeed been fixed. 
         [0054]    Result: Pressure was held for 20 minutes then bled off. 
         [0055]    Test 3: Tool inflated to 1800 psi, pressure of 1500 psi applied below the tool. 
         [0056]    Result: Pressure held for 10 minutes then bled off. 
         [0057]    Test 4: Deflated and removed tool from BOP, inspected the tool, and restabbed into the BOP. Tool was inflated to 2000 psi, and a pressure of 1800 psi was held below the tool. 
         [0058]    Result: One purpose of this test run was to demonstrate how fast the test could be performed. Not only did the pressure hold just as well as in previous runs, but also the test took only 28 minutes to perform from start to finish. 
       Modifications to the Tool 
       [0059]    Modifications to the original El tool were made to increase its versatility when being used for this application.
       The height of the cap at the end of the tool may be adjusted so that it may be used as a locator on top of the shear rams inside the BOP.   The number of inflate/deflate lines at both ends of the tool was increased.       
 
         [0062]      FIG. 1  shows the tool as configured during the BOP/riser connection test. The most important aspect of the schematic is the depiction of the slats on the top side of the tool (the slats are positioned up or down if the pressure is applied from below or above, respectively). 
         [0063]    In  FIG. 2 , the packer is turned over and pressure is applied from above through the perforated pup joint  16  (slats should always be positioned “opposite” the direction of the pressure). This configuration allows testing of the BOP/riser connections. The bottom of the tool is flat to use as a locator against the shear rams. 
         [0064]    If the circumferential spacing of the slats were decreased and the length of the slats were increased, the tool should be capable of reliably withstanding a test pressure of up to 20,000 psi within the lower marine riser package. The tool conveniently may be fabricated such that a box thread is provided at each end of the mandrel, so that each end may be connected with a threaded tubular. As shown in the figures, a lifting eye may also be added to the box end of the tool to assist in tool handling. Various types of valves may conventionally be provided for closing off flow through the tool, including a bull plug. 
         [0065]    With costs for offshore oil and gas development rising as sources of hydrocarbons become harder to produce, it is possible to use proven equipment in innovative ways in order to reduce the costs of offshore operations. Safety offshore is of primary importance. Rig crews can be trained in the redressing and operation of the tool, negating the need for additional personnel on the rig. The fewer people on the rig, the safer operations can be performed. The use of equipment in new applications also presents benefits, since the behavior of the tool should be known and predictable. 
         [0066]    An inflatable packer element as disclosed herein has a wide range of sealing diameters. The metal slats also may be radially expanded to grip with the interior of the package over a wide range of diameters. The tool of the present invention is particularly universal in its ability to test various size riser packages manufactured by various companies. When the package is made up at the well site for the first time, the tool may be used to effectively test ten to fourteen potential seals. This one tool thus effectively eliminates numerous specialty tools and caps previously used to test particular seals for a particular sized package by a particular manufacturer. The tool may be inverted so that test pressure may be applied from below as shown in  FIG. 4 , so that the slats are above and thus downstream from the sealing element, while the slats are beneath and thus downstream of the sealing element as shown in  FIG. 5  when pressure is applied from above. 
         [0067]    Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.