Abstract:
A regulation mechanism configured to automatically close off fluid flow through a line based on flow rate exceeding a predetermined level. This mechanism may be particularly beneficial when employed in conjunction with downhole chemical injection systems that are directed at well locations prone to becoming low pressure in nature. That is, in a conventional system, once the inherent pressure at the downhole end of an injection line exceeds that of the adjacent downhole environment, the flow rate of the column of fluid in the line may naturally increase as chemical is unintentionally emptied into the well. However, use of embodiments of the flow-based regulation mechanism detailed herein may near-automatically prevent such undesirable emptying of chemical into a low pressure well.

Description:
[0001]    PRIORITY CLAIM/CROSS REFERENCE TO RELATED APPLICATION(S) 
         [0002]    This Patent Document claims priority under 35 U.S.C. §119 to U.S. Provisional App. Ser. No. 61/438,995, filed on Feb. 3, 2011, and entitled, “Chemical Injection U-Tube Prevention System” incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0003]    Exploring, drilling and completing hydrocarbon wells are generally complicated, time consuming and ultimately very expensive endeavors. As a result, over the years increased attention has been paid to monitoring and maintaining the health of such wells. Significant premiums are placed on maximizing the total hydrocarbon recovery, recovery rate, and extending the overall life of the well as much as possible. Thus, logging applications for monitoring of well conditions play a significant role in the life of the well. Similarly, significant importance is placed on well intervention applications, such as clean-out techniques which may be utilized to remove debris from the well so as to ensure unobstructed hydrocarbon recovery. 
         [0004]    In addition to interventional applications, the well is often outfitted with chemical injection equipment to enhance ongoing recovery efforts without the requirement of intervention. For example, most of the well may be defined by a smooth steel casing that is configured for the rapid uphole transfer of hydrocarbons and other fluids from a formation. However, a buildup of irregular occlusive scale, wax and other debris may occur at the inner surface of the casing or tubing and other architecture restricting flow there-through. Such debris may even form over perforations in the casing, screen, or slotted pipe thereby also hampering hydrocarbon flow into the main borehole of the well from the surrounding formation. 
         [0005]    In order to address scale buildup as noted above, a variety of conventional interventional techniques are available. However, in order to avoid running time consuming interventional applications that may involve the delivery of footspace eating clean-out equipment, a circulating chemical injection system is often employed. This is particularly the case where the likelihood of buildup is accounted for up front, as is often the case in deep water wells. Regardless, with such systems in place, a metered amount of chemical mixture, such as a hydrochloric acid mix, may be near continuously circulated downhole to help prevent such buildup. 
         [0006]    The noted chemical injection equipment includes an injection line that may be run from surface and directed at different downhole points of interest such as within production tubing, at a production screen or into formation fluid prior to entering the noted tubing. Regardless, the need to halt production or run expensive interventions in order to address undesirable buildup may be largely eliminated. 
         [0007]    Unfortunately, regulating the delivery of the chemical injection mixture to the points of interest may come with pressure related challenges over the life of the well. For example, a given downhole point of interest within the well may display a fairly high pressure at the outset of operations. In some cases, well pressures may exceed 10,000 PSI. Therefore, the chemical injection line may be pressurized from surface so as to ensure that a proper chemical injection delivery rate is maintained. Indeed, a series of check valves may also be incorporated into the line to help avoid potentially caustic production uphole through the line. 
         [0008]    While utilizing check valves and pressurizing the line may initially ensure chemical injection delivery and avoid production through the line, pressures within the well may change over time. For example, pressurizing the line may overcome a well pressure of 10,000 PSI. However, when the pressure within the well drops over time as is often the case, the line may begin to leak chemical mixture into the well even without the application of positive pressure from surface. That is to say, depending on the depth of the line, the inherent fluid pressure therein may begin to exceed well pressure. 
         [0009]    Aside from the expense of lost chemical mixture into the well, leakage as a result of low well pressure may have a variety of negative consequences. For example, an exceeded rate or ratio of active chemical directed at the target location may act as a corrosive and damage the downhole tubing, screen or other equipment at the location. Once more, simply halting production by sealing off the line at surface may also be undesirable. For example, such action may result in forming a vacuum within the line that can lead to boiling of the chemical mixture. Thus, irreparable damage to the line, the production tubing and/or the casing may result. 
         [0010]    Such low pressure wells often lead to catastrophic circumstances that require a full chemical injection system change-out, major workover or even a complete loss of the well at a cost of between several hundred thousand to perhaps millions of dollars, not to mention lost production time. Indeed, rather than take such measures, these low pressure wells may be kept on-line only so long as artificial lift and other such production aids remain viable, after which time the well may be abandoned due to failure to effectively address buildup issues. 
       SUMMARY 
       [0011]    A chemical injection regulation mechanism is provided which includes inlet and outlet lines. A regulation device is coupled to the lines for regulating chemical flow therebetween based on a fluid flow directed thereat. For example, a method of regulating fluid flow between the lines is provided. The method includes directing a fluid downhole through the inlet line at a given rate and guiding the fluid to a regulator of the device having a pressure based on the given rate. The fluid may then be released through the outlet line and into a well where the pressure is below a predetermined level. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a side view of a downhole assembly employing an embodiment of a chemical injection regulation mechanism. 
           [0013]      FIG. 2  is an overview of an oilfield with a well accommodating the assembly of  FIG. 1  with the regulation mechanism incorporated therein. 
           [0014]      FIG. 3A  is an enlarged sectional view of the regulation mechanism of  FIGS. 1 and 2  in an open position to allow chemical flow therethrough. 
           [0015]      FIG. 3B  is an enlarged sectional view of the mechanism of  FIG. 3A  in a closed position to seal off chemical flow to the well. 
           [0016]      FIG. 4  is an alternate embodiment of a chemical injection regulation mechanism employing multiple regulators in tandem for flexibility in flow control. 
           [0017]      FIG. 5  is another alternate embodiment of a regulation mechanism incorporated into a downhole assembly and utilizing electric line control. 
           [0018]      FIG. 6  is a flow-chart summarizing an embodiment of employing a chemical injection regulation mechanism is disclosed. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Embodiments are described with reference to certain configurations of completions hardware that make use of chemical injection assemblies. In particular, completions are depicted and described which utilize a chemical injection assembly to help prevent scale and other buildup in an adjacent production tubular. However, whether on shore or offshore, a variety of different completion architectures may benefit from utilization of regulated chemical injection as detailed herein. For example, chemical injection directed at a well annulus, casing, production screen or a variety of other locations may benefit from a regulation mechanism as detailed herein. 
         [0020]    Referring now to  FIG. 1 , a side view of a downhole assembly  101  is shown. The assembly  101  utilizes an embodiment of a chemical injection regulation mechanism  100  to help manage the flow of chemical injection fluid into adjacent production tubing  180 . However, in other embodiments, such a chemical injection application may be directed at a variety of different completion hardware target locations. Regardless, as detailed further below, the regulation mechanism  100  may be particularly adept at preventing the undesirable drainage of a column of the injection fluid from a chemical injection line  120 . 
         [0021]    More specifically, a chemical injection mixture and application protocol at the depicted location of  FIG. 1  may be directed by an operator positioned a significant distance away at an oilfield  200  of  FIG. 2 . As detailed below, this results in a pressure exerted by the column of fluid in the line  120  which, depending on downhole conditions, may exceed pressure within the tubing  180 . Thus, the regulation mechanism  100  may be of significant benefit in deterring chemical fluid leakage into the depicted tubing  180 . 
         [0022]    In the embodiment shown, the assembly  101  is configured to support production in an uphole direction (see arrow  110 ). At the same time, the assembly  101  is outfitted with the chemical injection features such as the referenced line  120 . Thus, an ongoing metered amount of chemical injection fluid may be delivered to the tubing  180  so as to help minimize scale  190  or other production inhibiting buildup. 
         [0023]    With added reference to  FIG. 2 , and by way of example only, early in the life of the well  285 , downhole pressures may be quite dramatic, perhaps exceeding 10,000 PSI. Therefore, the assembly  101  may be outfitted with one way check valves  175  to ensure that production does not enter the tubing port  177  of the chemical injection system. These valves  175  may be located near the port  177  to protect as much of the line  120 , regulation mechanism  100 , and other chemical injection hardware from exposure to downhole fluids as possible. Additionally, in order to achieve chemical injection into the tubing  180  through the port  177 , a pump unit  227  may be utilized to drive up pressure and deliver a metered rate of injection. 
         [0024]    However, in other situations, for example, later in the life of the well, downhole pressures may drop dramatically, perhaps well under 500 PSI. Nevertheless, artificial lift and other measures may be taken to help ensure continued production viability of the well  285 . 
         [0025]    Continuing with reference to  FIGS. 1 and 2  and with such possible low pressure conditions of the well  285  in mind, the role of the regulation mechanism  100  is again considered. The mechanism  100  is shown with a coupling  140  for securing to the chemical injection line  120  which originates at the surface of the oilfield  200  as alluded to above. As a practical matter, this means that the noted column of fluid in the line  120  may span a distance of several thousand feet in vertical height. Thus, with a conventional line diameter of between 0.25 inches and 1.25, the fluid pressure at the coupling  140  and mechanism  100  may be far in excess of about 500 PSI (depending on the fluid type). 
         [0026]    By the same token, however, the tubing pressure at the location  179  adjacent the depicted tubing port  177  may be well under 500 PSI as in the example above. Indeed, this is often the case for wells that are offshore, substantially depleted, of extended life, or some combination thereof Whatever the case, as noted above, the disposal of the regulation mechanism  100  between the noted location  179  and the line  120  may be utilized to help avoid the undesirable chemical injection leakage into the tubing  180 . 
         [0027]    Referring directly now to  FIG. 2 , an overview of an oilfield  200  is shown which accommodates the assembly  101  of  FIG. 1  within a well  285 . More specifically, the assembly  101  is isolated with a packer  275  adjacent a perforated production region  297 . So, for example, the interior of the production tubing  180  is exposed to the region  297  for production but isolated from the remaining annulus  250  of the well  285 . Once more, as detailed above, debris such as scale and other buildup in the tubing  180  are kept at a minimum by the use of a chemical injection system that incorporates a regulation mechanism  100 , among other features. 
         [0028]    In the embodiment shown, the noted injection system is directed at delivery through a port  177  and into the tubing  180  as described above. The location of the delivery is such that uphole fluid flow via production may be utilized to distribute chemical injection mix through the tubing  180  keeping buildup therein at a minimum. However, depending on the nature of operations, such chemical injection may be directed at hardware directly adjacent the production region  297 , within the annulus  250 , or anywhere downhole that may be of operational benefit. Once more, there may be circumstances where downhole pressure (e.g. in the tubing  180 ) is of a level that&#39;s below the line-based injection fluid pressure at the downhole end of the line  120  (near the injection point). Nevertheless, the regulation mechanism  100  may help prevent uncontrolled injection fluid drainage, thereby avoiding any potential catastrophic results from such leakage. 
         [0029]    Continuing with reference to  FIG. 2 , the well  285  is outfitted with a casing  280  and traverses various formation layers  290 ,  295  in reaching the noted production region  297 . Thus, the chemical injection line  120  of the assembly  101  may traverse several thousand feet from surface before reaching the regulation mechanism  100 . As such, the significance of the mechanism  100  in holding back a column of injection fluid mixture may be appreciated, for example, where the corresponding downhole pressure is of a negligible level. 
         [0030]    Additionally, a host of equipment  220  is positioned at the oilfield  200  for running production, chemical injection, and other operations. In the embodiment shown, this includes a conventional well head  225  with production line  223  emerging therefrom along with a rig  221  for supporting a host of potential interventional tools. Further, pump  227  and control  229  units are also positioned adjacent the well head  225  for directing operations. For example, at the outset of operations, the pump unit  227  may be supplied by chemical tanks and utilized to circulate a tailored chemical fluid mixture down through the injection line  120 . 
         [0031]    The pump unit  227  may be configured to effect a pressure and rate sufficient for overcoming any high pressure downhole conditions. By the same token, changes to this rate, the ratio of constituents of the fluid mixture, or responsiveness to changing downhole pressures may be accounted for and directed by the control unit  229 . As described above, this may even include directing the pump unit  227  to halt positive pressure applied to the line  120  when downhole pressure becomes sufficiently low. In fact, at this time, the effectiveness of the regulation mechanism  100  in preventing chemical loss from the line  120  may be appreciated as noted above and detailed further below. 
         [0032]    Continuing with reference to  FIG. 2 , another advantage of utilizing the regulation mechanism  100  relates to testing of the injection system as a whole. That is, upon outfitting hardware within the well  285  as shown, a series of functional tests may be performed. For example, this may include testing seals and other features of the chemical line  120 . With the regulation mechanism  100  incorporated into the line  120 , such tests may now be performed at reasonably low pressures and without significant loss of chemical fluid. That is, flow rate and pressure may be introduced into the line  120  in order to close off the mechanism  100  as described and test fluid sealing thereof 
         [0033]    Referring now to  FIGS. 3A and 3B , enlarged sectional views depicting internal features of the regulation mechanism  100  of  FIGS. 1 and 2  are shown. More specifically,  FIG. 3A  is a view of the mechanism  100  in an open position to allow chemical flow therethrough, whereas  3 B depicts the mechanism  100  closed to seal off the chemical flow. 
         [0034]    With particular reference to  FIG. 3A , the mechanism  100  is depicted with the coupling  140  at one end for securing to the chemical line  120  and an outlet  360  leading to check valves  175  and other injection features (see  FIGS. 1 and 2 ). However, between this coupling  140  and outlet  360 , the flow rate of the noted chemical fluid mix  300  may determine whether or not the regulation mechanism  100  is left open or is closed. 
         [0035]    By way of a specific example, and continuing with reference to  FIG. 3A , the fluid mix  300  may be directed to the regulation mechanism  100  at a rate of about 0.1 gallons per minute. With added reference to  FIG. 2 , this may be achieved by operation of the pump  227  and control  229  units which may direct and monitor flow on an ongoing basis as well as account for factors such as the length and dimensions of the line  120 . Regardless, in the embodiment shown, and by way of example only, a flow rate of 0.1 gal./min. may translate into about a 150 lbs. of force applied to a valve  325  of within the mechanism  100 . Thus, where a biasing device  330 , in this case, a spring, is rated at about 200 lbs., such a flow of the fluid  300  would fail to overcome the spring. As such, the valve  325  would remain open and allow the fluid  300  to continue to flow through the regulation mechanism  100 . 
         [0036]    However, with added reference to  FIG. 3B  (and  FIG. 2 ), circumstances may dictate that the valve  325  be closed so as to stop the flow of chemical mix  300 . For example, as well noted above, low pressure conditions in the well  280  may constitute such circumstances. Indeed, where this is the case, the column of chemical mix  300  in the line  120  may naturally begin to flow at a greater rate due to a reduced pressure differential. For example, the flow rate may be increased, whether naturally or as directed by surface equipment  220 . For exemplary purposes only, consider that a rate increase to 0.2 gallons per minute might raise the forces exerted on the valve  325  to a predetermined 300 lbs., thereby overcoming the biasing device  330  and closing off flow through the mechanism  100 . More specifically, the valve  325  is equipped with a piston  350  and sealing head  355  which extends toward an exit channel  365  of the outlet  360 . Thus, when the force of the spring is overcome by the forces imparted on the valve  325 , the mechanism  100  is closed and flow from the line  120  is halted. 
         [0037]    Continuing with reference to  FIGS. 3A and 3B , with some added reference to  FIG. 2 , the manner by which forces imparted on the valve  325  and device  330  as a result of changing flow rate is described in greater detail. Namely, in the embodiment depicted, the valve  325  is a shuttle valve disposed in a chamber  320  defined by a body  301  of the mechanism  100  and outfitted with a seal ring  329  and flow restrictor  327 . Thus, the flow of fluid  300  into this chamber  320  from the line  120  translates into a force on the valve  325  that is enhanced primarily based on the dimensions of the restrictor  327 . That is, the smaller the restrictor  327 , the greater the magnification of the force. Regardless, with the restrictor  327  inherently of smaller dimension than the chamber  320  and the line  120 , some degree of force amplification results. 
         [0038]    The particular degree of force amplification may be tailored to the particular operational parameters in which the regulation mechanism  100  is to be utilized. So, for example, in certain embodiments a wide range and high rate of chemical injection delivery protocols may be utilized. Therefore, the amount of flow rate increase necessary to close off the regulation mechanism and injection may be greater than in applications where tighter tolerances or more precision is to be displayed in chemical injection delivery. Such design choices may be implemented through the use of flow restrictors  327  of varying sizes as noted above or through dimensional variations in the body of the valve  325  itself. Indeed, for added variability a manifold  400  of differently tailored regulator mechanisms may be utilized simultaneously (see  FIG. 4 ). 
         [0039]    In the embodiment shown, the diameter of the body of the piston head  355  is notably less than that of the spring and interfacing support structure. Thus, the effective diameter of the seal is limited in a manner that may allow for an equilibrium to develop between the pressure in the chamber  320  and pressure surrounding the spring. Therefore, to ensure that the valve  325  remains closed, continuous flow of fluid  300  may be maintained. Of course, in other embodiments, the effective diameter of the seal may be increased by enlarging the piston head  355  to a degree that continuous flow of fluid  300  may not be necessary. 
         [0040]    Referring now to  FIG. 4 , an alternate embodiment of a manifold  400  of chemical injection regulation mechanisms  410 ,  420 ,  430  operating in tandem to provide for flexibility in flow control. That is, each regulator  410 ,  420 ,  430  may be set to close off at a different flow rate threshold as determined by spring, restrictor and other internal component factors as noted above. For example, in one embodiment, a first regulator  430  may be configured for sealing upon exposure to a flow rate of 0.3 gallons per minute, a second regulator  420  for sealing upon exposure to 0.2 gallons per minute and a third regulator  410  to close off at 0.1 gallons per minute. Thus, as flow is introduced into the line  120  and driven up, the regulators  430 ,  420 ,  410  would be sequentially closed off 
         [0041]    As a practical matter, the sequential closing off of the regulators  430 ,  420 ,  410  as described above provides a system in which an overall wider range of flow rates and pressures may be utilized to achieve injection before completely shutting down an injection application. For example, such a manifold  400  may be configured to govern a metered rate of injection where flow rate from the line  120  ranges up to about 0.3 gallons per minute and imparts up to several thousand PSI on any of the individual regulators  430 ,  420 ,  410 . 
         [0042]    Referring now to  FIG. 5 , another alternate embodiment of a regulation mechanism  500  is shown. In this embodiment, the mechanism  500  operates to regulate a flow of chemical injection fluid  300  with the aid of a control line  510 , most likely of an electric variety, although other signaling platforms may be utilized. Regardless, in the embodiment shown, the mechanism  500  regulates or meters the delivery of the injection fluid  300  by way of a valve  525 , in this case shifted open or closed via signaling over the noted line  510 . That is, in this embodiment, electric signaling may be utilized in place of flow control for regulating the chemical injection application. Regardless, this technique helps avoid undesired release of injection fluid  300  in circumstances where downhole pressures are substantially low. 
         [0043]    In the embodiment of  FIG. 5 , the valve  525  may be directed to release the chemical injection fluid  300  through a port  579  as shown. However, this ported release may again be directed at a variety of locations. This may include directing the fluid  300  to flow upstream with production fluid  110  before release into the tubing  180  so as to help prevent buildup at a port  577  thereat. Indeed, in the embodiment shown, the fluid  300  is actually routed toward a flow control valve  527  that more directly meters the release of fluid  300  into the production tubing  180 . For example, in one embodiment, this valve  527  may be further guided by input from a viscosity  560 , flow  540  or other sensor for tighter precision over the chemical injection release into the tubing  180  via a release port  577 . 
         [0044]    Continuing with reference to  FIG. 5 , a regulation mechanism  500  may be utilized at a variety of site specific locations. For example, in the embodiment of  FIG. 5 , the mechanism  500  is utilized to guide and regulate chemical injection at a specific isolated zone of a downhole assembly. That is, the mechanism  500  is disposed in a region of the well  285  that is cased  280  and isolated by packers,  275 ,  575  in a manner targeting production from the specific production region  297 . Indeed, a variety of different such production zones may be a part of the overall well architecture, each with its own discrete hardware and independently operating regulation mechanism  500  tailored to the production and conditions thereat. Thus, a more site specific and overall tailored injection profile for the entire well  285  may be developed. 
         [0045]    Referring now to  FIG. 6 , a flow-chart summarizing an embodiment of employing a chemical injection regulation mechanism is disclosed. Namely, an injection line leading through a well may be supplied with a chemical fluid mixture as indicated at  610 . Thus, a column of fluid with its own column-based pressure at its downhole end is provided. Thus, the mix may be flowed through the line to a downhole target location as indicated at  630 . Where downhole pressure is less than the column-based pressure, the potential exists for this to be achieved without the use of surface pumps or the like. Alternatively, as noted at  650 , positive pressure may also be utilized as needed. 
         [0046]    Regardless, once the flow is begun, the system is equipped with a regulation mechanism that provides for the sealing off of the flow when desired by exceeding the rate to above a predetermined level (see  670 ). Thus, undesirable leakage of chemical flow may be avoided. As referenced above, this sealing may take place sole based on the flow resulting from a column-based pressure differential (see  610  proceeding directly to  670 ) or by intentionally pumping at a higher rate from surface. Additionally, as indicated at  690 , the presence of the mechanism allows for early stage seal testing of the injection line and/or periodic testing during the life of the well without significant risk of such chemical fluid losses. 
         [0047]    Embodiments described hereinabove include a chemical injection regulation mechanism that may be utilized to avoid expenses associated with the loss of chemical injection fluid into a well as a result of low downhole pressures. Once more, more dramatic consequences related to chemical fluid leakage and/or corresponding vacuum induced line closure may also be avoided. Such regulation is achieved in a manner which avoids any undesired downtime in injection capacity and even allows for early stage testing of chemical injection line sealing capacity. 
         [0048]    The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. Regardless, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.