Abstract:
A valve for downhole use has the ability to throttle between fully open and closed and is fully variable in positions in between. The valve is preferably responsive to flowing fluid viscosity and uses a three dimensional flow through restrictor in combination with a relatively movable cover. At a given flow, a higher viscosity fluid will create a greater relative movement and make it possible for flowing fluid to bypass more of the flow through member. In a particular application involving production from a zone, an array of such valves can allow more production where the viscosity is higher and less production where the viscosity drops due to, for example, water production.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of the invention is separation devices for downhole use and more particularly valves responsive to flowing fluid properties. 
       BACKGROUND OF THE INVENTION 
       [0002]    Valves called chokes are commonly used in oil and gas service to throttle between pressure levels between a fully open and fully closed position. One way they operate is by having a movable sleeve in a stationary housing. The sleeve has a series of longitudinally spaced holes on a common circumference and is manipulated axially for alignment of different sized holes with the fixed port in the outer housing. While this arrangement allows for some setting variability it still leaves gaps in the control because of the step change in sizes between adjacent holes that are longitudinally spaced. Beyond that there are considerations of erosion from high velocity flows, particularly in gas service where solids can be entrained. 
         [0003]    One way the present invention addresses this design issue it to move away from the prior design of overlapping openings by using a porous media with a quantifiable resistance per unit length to act as a resistance to flow. Access through the medium is increased or decreased between end positions where one defines the substantially no flow condition and another provides substantially full access over the length of the medium to define the fully open position. 
         [0004]    In another aspect, the valve features an ability to respond to a property of the flowing liquid to vary its position responsive, for example, to flowing liquid viscosity. In a screen application, for example, multiple such valves can be in position. When the desired hydrocarbon that has a much higher viscosity than water is flowing, the movable member can leave more of the flow through valve member exposed to reduce resistance to flow. This encourages portions of a zone that are making pure hydrocarbons to continue to do so over other locations where the onset of water production has reduced viscosity. The reduced viscosity allows a closure device to cover more of the flow through the member so as to reduce or cut off flow from areas where water is being produced. This can be accomplished without even having to measure viscosity by making the mechanical components responsive in predetermined ways to an expected range of viscosities. Totally manual as well as totally automatic operations are also contemplated. 
         [0005]    These and other aspects of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and associated drawings while recognizing that the full scope of the invention is given by the claims. 
       SUMMARY OF THE INVENTION 
       [0006]    A valve for downhole use has the ability to throttle between fully open and closed and is fully variable in positions in between. The valve is preferably responsive to flowing fluid viscosity and uses a three dimensional flow through restrictor in combination with a relatively movable cover. At a given flow, a higher viscosity fluid will create a greater relative movement and make it possible for flowing fluid to bypass more of the flow through member. In a particular application involving production from a zone, an array of such valves can allow more production where the viscosity is higher and less production where the viscosity drops due to, for example, water production. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a section view of a valve featuring a flow through media partially uncovered due to fluid flow of a low viscosity displacing a sleeve; 
           [0008]      FIG. 2  is the view of  FIG. 1  with a low viscosity fluid present that allows the flow through media sleeve to be spring biased to cover more of the flow through media; 
           [0009]      FIG. 3  is an alternative embodiment to  FIG. 1  showing the inverse of the  FIG. 1  design where the blank sleeve is movable rather than the flow through media; 
           [0010]      FIG. 4  is the view of  FIG. 3  where a low viscosity fluid is flowing that allows the sleeve to advance over the flow through media to retard flow; 
           [0011]      FIG. 5  is a manual design that allows moving the flow though media with respect to a surrounding stationary sleeve; 
           [0012]      FIG. 6  is the reverse of  FIG. 5  where the sleeve is movable with respect to a stationary flow through media. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    In the preferred embodiments the valve assemblies are arrayed in conjunction with an assembly of screens  10  that can span for thousands of feet depending on the configuration of the producing interval. The structural support for the screen assembly  10  is commonly known as a base pipe  12  which runs the length of the screen assembly  10 . The base pipe over its length has openings  14 . The openings  14  are generally disposed in arrays of multiple openings on a given spacing pattern. While some inflow balancing can be done by varying the cross-sectional area of the arrays along a length of screen  10 , another technique is to associate a valve  16  with a given array  14 . In the present invention the valve  16  associated with an array  14  is responsive to a fluid property for the fluid flowing through it. In one embodiment the fluid property is viscosity. When a high viscosity desirable hydrocarbon is being produced, the flow in combination with that higher viscosity produced a high enough force on the element  18  to displace it against spring  20  and to offset the element  18  from stationary sleeve  22 . Thus in the position of  FIG. 1  the element  18  which preferably is made of a pack of beads of a known diameter yielding a network of passages though it of a known size configuration, winds up being short circuited as more flow can exit laterally through side  24  without having to flow to the end  26 . Thus the flow paths to end  26  have an axis that intersects with flow paths through side  24 , which, in the preferred embodiment, happens to be a cylindrical surface. To complete the structure, an outer tube  28  is used to create an annular space  30  between the screen  10  and the openings  14 . In order for flow represented by arrow  32  to reach the openings  14  it has to flow through the porous material element  18  which is movably mounted over sleeve  22  which is fixed. The flow passing through element  18  creates a pressure drop and a net force that compressed the spring  20 . As the spring  20  is compressed and the element  18  shifts to the left, more of the side  24  of element  18  comes out of alignment with sleeve  22 . The more viscous the material is that represents flow  32  the greater the force exerted on spring  20 , the more element  18  shifts left and as a result the less resistance to flow is offered to the viscous fluid as more of the flow entering the element  18  can make a fast lateral exit out the side surface  24  that is no longer in alignment with sleeve  22 . 
         [0014]    On the other hand, if the viscosity drops, indicating the appearance of water, for example, or some other unwanted fluid, the net pressure exerted for a given flow rate against the element  18  will drop as that given flow rate can move through the porous element with less resistance. When that happens, the spring  20  can shift the element  18  to the right to an extreme position where the element  18  comes into alignment with sleeve  22 , as shown in  FIG. 2 . The end  34  can be made impervious and depending on the strength of spring  20  the valve  16  in the  FIG. 2  position can be fully closed to fluids. A seat  36  that also acts as a travel stop for the element  18  can be provided in the form of an inner and outer seal rings such that if combined with an impervious end  34  and a strong enough spring  20  can actually close the valve  16  if the viscosity drops low enough due to production of an unwanted fluid such as water. 
         [0015]      FIGS. 3 and 4  are simply a reverse of the design of  FIGS. 1 and 2 . The element  18  is now fixed to a retainer  38 . The sleeve  22  is movably mounted with a peripheral seal ring  40 . When the viscosity of the flowing fluid  32  is high the force against sleeve  22  will overcome the spring  20  and expose more of the side surface  24  of the element  18  which will mean a reduction of resistance to flow and enhanced flow of the desirable hydrocarbon through screen  10 . On the other hand, if the viscosity drops, for a given flow rate the force on sleeve  22  will decrease to allow spring  20  to shift element  18  to the  FIG. 4  position such that the side surface  24  is substantially within the sleeve  22  and resistance to flow goes higher because all the flow has to go clean through the length of the element  18  to the only exit at end  26 . Optionally, end  34  can be impervious and come up against a seal ring  36 . Then, if the spring  20  is strong enough, the valve in the  FIG. 4  position can exclude fluid. 
         [0016]      FIGS. 5 and 6  illustrate totally manual operation. In  FIG. 5 , the element  18  is secured to an operator  46  with sleeve  22  held fixed. The sleeve  18  is movable relative to fixed sleeve  22 . In  FIG. 6  the element  18  is held fixed by retainer  38  while the sleeve  22  is moved by the adjustment mechanism  46 . Optionally an impervious end cap  34  can be used to shut off flow while the resistance to flow is infinitely variable by simply positioning the element  18  either more in alignment with sleeve  22  or less so. 
         [0017]    Element  18  is preferably a cylindrical shape of a bead pack or a sintered material or some other porous material. The passages or openings through it need not be uniform. Rather the structure needs to be responsive to a change in fluid property and respond to such a change for a given flow rate with a change in force applied to a closure device. In the preferred embodiment the fluid property that changes that affects the movement of the element  18  or its associated sleeve  22  is viscosity. The actual viscosity need not be locally measured but it can be and in association with a processor connected to an operator that replaces spring  20  can achieve the same result. The illustrated preferred embodiments are just simpler and cheaper and more reliable in that they need not literally measure the fluid property change that affects their performance. Instead, what needs to be known for a given configuration of porous element is its pressure versus flow characteristics for a given viscosity. 
         [0018]    On the other hand using a system, schematically illustrated as S, that senses an actual fluid property and can convert that signal using a processor into a proportional movement, the same effect of keeping out undesirable ingredients can be accomplished if there is a fluid property that identifies the undesirable ingredient. For example pH may be used as a measured quantity to affect changes in relative position between the element  18  and the sleeve  22 . 
         [0019]    While the element  18  has been depicted as a cylinder surrounded by a sleeve  22  the arrangement can be inverted using an impervious cylindrical plug surrounded by a porous annularly shaped member as shown in  FIGS. 1 and 2 . While a coil spring  20  is illustrated, equivalents such as pressurized chambers, Belleville washer stacks or other devices that store potential energy could be used. Alternatively a control system can use motors of various types such as a stepper motor or a ball screw assembly to create the relative movement responsive to fluid property change. 
         [0020]    In another variation, the actual flowing fluid can be analyzed as it passes a sensor to specifically identify ingredients and operate the valve  16  to exclude the unwanted fluids. 
         [0021]    The design of a pair of members where there is relative movement and flow though one of the members allows infinite variability in a throttling application such as a choke with a possibility of dramatically reducing or cutting off unwanted flows. Another advantage is better resistance to the erosive effects of high velocities and a cheaper way to rebuild the valve if necessary by simply replacing a porous element. 
         [0022]    The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.