Abstract:
A system for injecting fluids into a well having a fluid supply tine that is connected to a mandrel at the top of the production tree. The system is designed so that all components of the system are packaged together and run to the production tree in one run. The production tree is designed to provide a pathway for the fluid to travel from the mandrel to the production bore within the tree, and then into the production tubing of a well.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to the injection of fluid into oil and gas wells. In particular, this invention relates to the delivery of fluid to a well through a production tree mounted on the well, by injecting the fluid through a mandrel in the production tree. 
         [0003]    2. Brief Description of Related Art 
         [0004]    The production of oil and gas from some wells may lead to contact between compounds in hydrocarbon rock formations, and those present in oilfield process fluids, such as, for example, seawater. This contact may lead to the formation of “scale”, or salts that clog the formation and inhibit hydrocarbons in the formation from entering the well. Accordingly, scale inhibitors are sometimes introduced into a well to control or prevent scale deposition. In some cases, scale inhibitors may be combined with fracture treatments, whose purpose is to crack the formation and facilitate the release of hydrocarbons into the well. 
         [0005]    The fluids used to inhibit scaling and to cause fracturing (hereinafter referred to as scale squeeze fluid, or just fluid) are typically introduced to the well through the choke of a production tree attached to the well. From the choke, the fluid may enter the production bore of the tree, the production tubing of the well, and ultimately the formation in need of de-scaling/fracturing. However, there are problems associated with introducing the fluid through a choke on the production tree. 
         [0006]    For example, when the fluid is introduced through the choke, the capacity of the choke to carry out other functions, such as managing pressure within the well, may be reduced or eliminated. In addition, introduction of the fluid through the choke requires a special choke insert adapted for interface with a landing module that delivers the fluid. Retrofitting the choke to accept the special choke insert can be a complicated process that requires multiple steps. The steps include running guide posts, running a remote component replacement (RCR) tool to remove any old choke inserts, running an RCR tool to insert the special choke insert, running a scale squeeze module, injecting the scale squeeze fluid, recovering the module, and capping the scale squeeze adapter. 
         [0007]    Accordingly, there is a need for a fluid injection system and process that overcomes the disadvantages of the prior art. 
       SUMMARY OF THE INVENTION 
       [0008]    Disclosed herein is a fluid injection system in which the fluid is injected not into the choke of a production tree, but directly into a mandrel at the top of the tree. A pathway is provided within the production tree for the fluid to travel from the mandrel to the production bore within the tree, and then into the production tubing of a well. 
         [0009]    Also disclosed herein is a process for injecting fluid into a well by injecting the fluid. directly into the mandrel at a production tree mounted to the well. The process includes attaching a fluid supply line to the mandrel of the production tree with a connector. In one embodiment, all of the components necessary to connect the fluid supply line to the mandrel, and to control the flow of fluid through the fluid supply line, are included in one package, so that installation of the fluid injection system requires only one trip to deliver the package and install the components of the system at the production tree. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will be better understood on reading the following detailed description of nonlimiting embodiments thereof, and on examining the accompanying drawings, in which: 
           [0011]      FIG. 1  is a schematic side cross-sectional view of an example embodiment of a production tree having a flow path from a mandrel at the top of a production tree to a production bore in the tree; and 
           [0012]      FIG. 2  is a schematic side cross-sectional view of an example embodiment of a fluid injection system arranged and designed to deliver a fluid to a mandrel at the top of a production tree. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    The system and method of the present disclosure will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown, and wherein like reference numerals refer to like elements throughout. The subject matter of the present disclosure may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0014]    It is to be understood that the subject of the present disclosure is not limited to the exact details or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there are disclosed illustrative embodiments of the subject disclosure and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. 
         [0015]    Referring to  FIG. 1 , there is shown a schematic side cross-sectional view of a production tree  2  according to one possible embodiment of the present invention. The production tree  2  has a production bore  4  in fluid communication with, and configured for attachment at a lower end to, the production tubing of a well (not shown). The production tree  2  also includes a mandrel  6  at an upper end. A fluid port  8  provides a pathway through the mandrel  6  to an annulus wing block through annulus access valve  10 , and from the annulus access valve  10  to a crossover port  12 . An annulus master valve  14  separates the crossover port  12  from the portion of the annulus below the annulus master valve  14 . 
         [0016]    The crossover port  12  provides a pathway from the annulus wing block to a production wing block through a crossover valve  16 . The crossover port  12  intersects the production bore  4  at a location between a production wing valve  18  and a production master valve  20 . The production wing valve  18  separates the crossover port  12  from the portion of the production bore upstream of the production wing valve  18 . Each of the valves disclosed herein may be controlled by known methods. For example, the valves may be hydraulically controlled. Alternatively, the valves may be mechanically or electrically controlled. 
         [0017]    One advantage to the production tree configuration shown in  FIG. 1  is that fluid, such as, for example, scale squeeze fluid, may be introduced directly to the production bore  4  through the mandrel  6  of the production tree  2 . One reason this direct injection through the mandrel  6  is advantageous is that it eliminates the need to introduce the fluid through a choke. This frees the choke for use for other purposes, such as controlling pressure within the well. Another advantage to introducing fluid to the production tree directly through the mandrel, and not the choke, is that when connecting the fluid lines, it is easier to land the connector (discussed in more detail below) on the mandrel than the choke. 
         [0018]      FIG. 2  shows a schematic side cross-sectional view of a fluid injection system according to an embodiment of the present invention, where the fluid is introduced to the production tree  2  through a mandrel  6  at the top of the production tree  2 . As can be seen, fluid may be brought to the fluid injection system by a fluid supply line  22  that connects the fluid injection system with a fluid source at another location (not shown), such as, for example, at the surface of the sea. The fluid supply line  22  communicates with the production tree  2  via a connector  24 . In an example embodiment, the connector  24  is annular and includes clamps (not shown) on an inner circumference that can selectively attach on the outer circumference of the mandrel  6  of the production tree  2 . In one embodiment, the connector  24  may be a MDH4 connector. The connector  24  is optionally adaptable for use with different function packages. addition, different connectors may be used to connect the fluid supply line  22  to different types of production trees. For example, although the production tree shown in  FIG. 1  is a horizontal tree, the fluid injection system of the present invention may also be used with trees having a vertical configuration. 
         [0019]    As shown in  FIG. 2 , the fluid supply line  22  may include one or more valves to control the flow of fluid through the supply line  22 . For example, the fluid supply line  22  may include an isolator valve  26  and/or a check valve  28 , in addition, the fluid injection system may include additional components depending on the type and structure of the production tree  2 . For example, if the production tree has a plug  30  in the top of the mandrel  6 , the system may include a plug removal tool  32  such as that disclosed in, for example, U.S. Pat. Nos. 7,240,736 and 6,968,902. Similarly, a remotely operated vehicle (ROV) carrier  34  may be included in the system. Furthermore, the fluid injection system may include safety devices, such as, for example, an emergency quick disconnect  36  to ensure a secure disconnect. 
         [0020]    One advantage to the fluid injection system shown in  FIG. 2  is that all of the necessary structure (e.g., the supply line  22 , isolator valve  26 , check valve  28 , emergency quick disconnect  36 , ROV carrier  34 , plug removal tool  32 , and connector  24 ) can be placed in one trip, with just one land and lock of the connector. Thus, installation of the system of  FIG. 2  is faster and more cost effective than the installation of known systems, many of which require running multiple parts and tools separately in order to connect fluid supply lines to the production tree. 
         [0021]    With the structure of the production tree  2  and fluid injection system as shown in  FIGS. 1 and 2 , the flow path of fluid introduced through the system is as follows: First, the fluid travels from a fluid source to the connector  24  via fluid supply line  22 . Then the fluid travels through the connector  24  and the mandrel  6  via the fluid port  8 . The annular access valve  10  is open and the annulus master valve  14  is closed, so that the fluid travels through the annular access valve  10  and into the crossover port  12 . Thereafter, with the crossover valve  16  open, the production access valve  18  closed, and the production master valve  20  open, the fluid travels through the crossover valve  16  and the production master valve  20  into the production bore  4 . Thus, the fluid enters the production tree  2  through the mandrel  6  and ultimately into the production bore  4 . From the production bore  4  the fluid travels into the production tubing of the well. 
         [0022]    Another embodiment of the invention includes a method of injecting fluid into the production tubing of a well by introducing the fluid through a mandrel at the top of a production tree. First, the production tree is positioned at the top of the well, so that the production bore of the tree is in fluid communication with the production tubing in the well. In one embodiment, the production tree is designed as described above in reference to  FIG. 1 , with a flow path between a mandrel at the top of the tree and the production bore of the tree. A fluid supply line, such as that described above with respect to  FIG. 2 , is attached to the mandrel of the production tree. Thereafter, fluid is injected through the mandrel, into the production tubing of the tree, and then from the tree into the production tubing of the well. In one embodiment, the liquid may be scale squeeze liquid, although other types of fluid may he introduced by the same method. 
         [0023]    While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, in addition to the parts of the production tree specifically discussed above, other known tree components may be included in the tree. For example, the tree may include chokes, hydraulic or electric control tines for the valves, etc. Similarly, this system can be integrated with other deep water packages. Furthermore, it is to be understood that the above disclosed embodiments are merely illustrative of the principles and applications of the present invention. Accordingly, numerous modifications may be made to the illustrative embodiments and other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.