Abstract:
Methods and apparatus for use within a production pipeline or other flowbore to reduce fluid pressure and regulate fluid flow while minimizing erosion effects caused by particulate matter in the fluid, wherein varying geometries with respect to multiple components within a choke valve are utilized to effectuate multiple changes in fluid flow direction, causing a fluid pressure drop at each directional change.

Description:
RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/466,135, filed Apr. 28, 2003. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to methods and apparatus for reducing fluid pressure and regulating fluid flow within a production pipeline or other flowbore while minimizing erosion effects caused by particulate matter within the fluid. 
   2. Description of the Related Art 
   Production pipelines are used to transmit hydrocarbons, in the form of crude oil or natural gas, from a producing well to a storage facility or distribution point. These pipelines typically include one or more flow control devices, commonly referred to as “chokes.” The purpose of these devices is to reduce fluid pressure and regulate flow in the hydrocarbon stream. If fluid pressure is not reduced and flow goes unregulated, the high-pressure stream could cause damage to the more vulnerable downstream portions of the pipeline system. 
   Hydrocarbon streams, particularly natural gas, can often carry solid particulates such as sand. These solid particulates can clog flow in the flow control device and abrade or erode the device&#39;s internal components. Accordingly, the flow control device should be resistant to clogging and internal damage caused by such particulate-containing streams. 
   Various types of flow control devices for pipelines have been proposed to reduce fluid pressure, control fluid flow, and provide resistance to abrasion and/or erosion. These flow control devices primarily utilize some form of stem and seat mechanism, wherein the stem and seat are located within a valve body, and the stem is concentrically located within the seat. During operation, the seat remains static, and the stem moves relative to the seat, exposing a varying area. The exposed area at this single location within these devices controls the amount of pressure drop occurring and the resulting dissipation of energy in the flow stream. 
   These previously proposed flow control devices suffer from a number of disadvantages. One disadvantage is that the only component within these devices that is utilized to effectuate a significant pressure drop is the geometry of the single varying area. As a result, the pressure drop occurring within the device is primarily limited to that which occurs at this single location within the device. Another disadvantage is that the internal components of the flow control devices are subject to abrasion and erosion as a result of a geometry that brings the components into direct contact with the high pressure, solid particulate-containing hydrocarbon fluid stream. 
   Prior to the development of the present invention, there has been no choke valve apparatus or fluid flow enhancer apparatus for use as a part of a choke valve which: utilizes controlled geometric principles to effectuate multiple pressure drops at different locations within a flow control device; and encourages erosive solid particulates in a fluid stream to impact surfaces within the flow control device with a degree of angular control that minimizes erosive damage. Additionally, there has been no method of dissipating the energy of, or effectuating multiple pressure drops for, a fluid within a choke valve which: utilizes controlled geometric principles to effectuate such multiple pressure drops at different locations within a flow control device; and encourages erosive solid particulates in a fluid stream to impact surfaces within the flow control device with a degree of angular control that minimizes erosive damage. Therefore, the art has sought methods and apparatus for reducing fluid pressure and regulating fluid flow within a pipeline or other flowbore while minimizing erosion effects caused by particulate matter within the fluid which: utilize controlled geometric principles to effectuate multiple pressure drops at different locations within a flow control device; and encourage erosive solid particulates in a fluid stream to impact surfaces within the flow control device with a degree of angular control that minimizes erosive damage. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, the foregoing advantages have been achieved through the present fluid flow enhancer for use as a part of a choke valve. The present invention includes: a flow enhancement sleeve having an inner wall surface, an outer wall surface, and first and second ends; a focus rim disposed at the first end of the flow enhancement sleeve; a flow focus element disposed in a spaced relationship from the focus rim, the flow focus element and the focus rim defining a flow passage therebetween; and a flow regulator disposed within a portion of the flow enhancement sleeve for receiving fluid from the flow passage. 
   Another feature of the present invention is that the fluid flow enhancer may have a helical groove disposed within the outer wall surface of the flow enhancement sleeve. Another feature of the present invention is that the fluid flow enhancer may have a helical groove disposed upon the outer wall surface of the flow enhancement sleeve. Another feature of the present invention is that the fluid flow enhancer may have a flow focus element with a wall surface having an annular shaped recess disposed in the wall surface for deflecting flow across the focus rim. A further feature of the present invention is that the flow enhancer may have a flow focus element with a recess that is inwardly rounded. Another feature of the present invention is that the flow enhancer may have a flow regulator that is a cage-type valve. An additional feature of the present invention is that the flow enhancer may have a flow regulator that is a needle-type valve. Another feature of the present invention is that the fluid flow may be additionally enhanced by varying the shape of the focus rim. A further feature of the present invention is that the fluid flow may be additionally enhanced by varying the distance between the flow focus element and the focus rim. 
   In accordance with another aspect of the present invention, the foregoing advantages have also been achieved through the present choke valve. The present invention may include: a fluid flow inlet; a fluid flow outlet; and a choke body for facilitating flow between the fluid flow inlet and the fluid flow outlet, the choke body including a housing having an inner wall surface, a flow enhancement sleeve having an inner wall surface, an outer wall surface, and first and second ends, the flow enhancement sleeve disposed within a portion of the housing, a focus rim disposed at the first end of the flow enhancement sleeve, a flow focus element disposed in a spaced relationship from the focus rim, the flow focus element and the focus rim defining a flow passage therebetween, and a flow regulator disposed within a portion of the flow enhancement sleeve for receiving fluid from the flow passage. 
   Another feature of the present invention is that the choke valve may have a helical groove disposed within the outer wall surface of the flow enhancement sleeve. A further feature of the present invention is that the choke valve may have a helical groove disposed within the inner wall surface of the housing. Another feature of the present invention is that the choke valve may have a helical groove disposed upon the outer wall surface of the flow enhancement sleeve. A further feature of the present invention is that the choke valve may have a helical groove disposed upon the inner wall surface of the housing. Another feature of the present invention is that the choke valve may have a flow focus element with a wall surface having an annular shaped recess disposed in the wall surface for deflecting flow across the focus rim. A further feature of the present invention is that choke valve may have a flow focus element with a recess that is inwardly rounded. Another feature of the present invention is that the choke valve may have a flow regulator that is a cage-type valve. An additional feature of the present invention is that the choke valve may have a flow regulator that is a needle-type valve. An additional feature of the present invention is that the choke valve may have an inner lining disposed adjacent to the inner wall surface of the housing. 
   In accordance with another aspect of the present invention, the foregoing advantages have also been achieved through the present method of dissipating the energy of a fluid within a choke valve. This aspect of the present invention may include the steps of: utilizing varying geometry with respect to multiple components within the choke valve to effectuate a plurality of changes in the direction of fluid flow; and causing a pressure drop for the fluid at each of the plurality of changes in flow direction. 
   In accordance with another aspect of the present invention, the foregoing advantages have also been achieved through the present method of dissipating the energy of a fluid within a choke valve. This aspect of the present invention may include the steps of: passing the fluid in a helical direction through a first portion of the choke valve; deflecting the fluid off a second portion of the choke valve; passing the fluid through a flow passage between the first and second portion of the choke valve; and passing the fluid through a flow regulator disposed within the sleeve. 
   Another feature of the present invention may include the step of: utilizing, as a first portion of the choke valve, a flow enhancement sleeve disposed within the choke valve. A further feature of the present invention may include the step of: utilizing, as a second portion of the choke valve, a flow focus element of the choke valve. 
   In accordance with another aspect of the present invention, the foregoing advantages have also been achieved through the present method of effectuating multiple pressure drops for a fluid within a choke valve. This aspect of the present invention may include the steps of: causing a first pressure drop by passing the fluid in a helical direction through a first portion of the choke valve; causing a second pressure drop by passing the fluid through a second portion of the choke valve; and causing a third pressure drop by passing the fluid through a third portion of the choke valve. 
   Another feature of the present invention may include the step of: utilizing, as a first portion of the choke valve, a flow enhancement sleeve disposed within the choke valve. A further feature of the present invention may include the step of: utilizing, as a second portion of the choke valve, the area between a focus rim and a flow focus element of the choke valve. A further feature of the present invention may include the step of: utilizing, as a third portion of the choke valve, a flow regulator disposed within the choke valve. 
   The methods and apparatus of the present invention for reducing fluid pressure and regulating fluid flow within a pipeline or other flowbore while minimizing erosion effects caused by particulate matter within the fluid, when compared with previously proposed methods and apparatus, have the advantages of: utilizing controlled geometric principles to effectuate multiple pressure drops at different locations within a flow control device; and encouraging erosive solid particulates in a fluid stream to impact surfaces within the flow control device with a degree of angular control that minimizes erosive damage. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial cross-sectional side view of the preferred embodiment of the present invention. 
       FIG. 2  is a partial cross-sectional side view of the preferred embodiment of the present invention. 
       FIG. 3  is a partial cross-sectional side view of another embodiment of the present invention. 
       FIG. 4  is a partial cross-sectional side view of another embodiment of the present invention. 
   

   While the invention will be described in connection with the preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention as defined by the appended claims. 
   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to  FIG. 1 , a choke valve assembly  20  in accordance with the present invention is shown to generally comprise: a flow inlet  30 , a flow outlet  40 , and a choke body  50 . Choke body  50  includes a housing  60  and a fluid flow enhancer  65 . 
   Still with reference to  FIG. 1 , choke body  50  receives fluid flow from inlet  30  and dispenses fluid flow from outlet  40 . Inlet  30  and outlet  40  are preferably set at a right angle to one another, thereby providing an elbow configuration for choke body  50 , although other angular dispositions of inlet and outlet  30 ,  40 , could be utilized. Choke body  50  includes a housing  60  having an inner wall surface  61 . Housing  60  is typically constructed of a strong and chemically resistant material, such as a steel alloy or any other material having the requisite strength and durability properties to function as housing  60 , as known by those skilled in the art. Fluid flow enhancer  65  is disposed within housing  60  and is generally surrounded by inner wall surface  61  of housing  60 . 
   Fluid flow enhancer  65  generally comprises a flow enhancement sleeve  70 , a flow focus element  90 , and a flow regulator  110 . Sleeve  70  is generally tubular shaped, and has an inner wall surface  71 , an outer wall surface  72 , a first end  73 , and a second end  74 . A focus rim  80  is disposed at the first end  73  of sleeve  70 . Preferably, focus rim  80  is integrally formed with first end  73  of sleeve  70 . Focus element  90  is disposed in a spaced relationship from focus rim  80 . Preferably, focus element  90  is disposed above, and opposite from, focus rim  80 . The area between focus rim  80  and focus element  90  defines a flow passage  100 . Flow regulator  110  is disposed within a portion of sleeve  70 . Flow regulator  110  may be of a conventional type used to regulate flow in a pipeline or flow control device used therein. A conventional cage-type valve is illustrated in  FIG. 1 . However, other valves types may be utilized without deviating from the spirit of the present invention. 
   In operation, as illustrated in  FIG. 1 , high-pressure fluid enters choke valve assembly  20  through flow inlet  30  and encounters fluid flow enhancer  65 . Fluid flow enhancer  65  effectuates a series of pressure drops in the fluid by utilizing varying geometry at different locations of enhancer  65  to cause changes in fluid flow direction, with a resulting pressure drop and corresponding enhanced fluid flow at each change in flow direction. 
   The first fluid pressure drop occurs when fluid encounters flow enhancement sleeve  70 . The geometry of sleeve  70  forces fluid flow to change direction and generally flow circumferentially around outer wall surface  72  of sleeve  70  and move toward focus rim  80  at first end  73 . In the preferred embodiment, as illustrated in  FIG. 2 , the flow is directed along a helical groove  120  disposed within outer wall surface  72  of sleeve  70 . In another embodiment (not shown), helical groove  120  may be disposed upon outer wall surface  72  of sleeve  70 . In still another embodiment (not shown), helical groove  120  may be disposed within inner wall surface  61  of housing  60 . In still another embodiment (not shown), helical groove  120  maybe disposed upon inner wall surface  61  of housing  60 . As illustrated in  FIG. 3 , an inner lining  66  may be disposed adjacent to inner wall surface  61  to alter the geometry within housing  60  to further regulate pressure and flow within choke valve assembly  20  or to protect surface  61 . 
   Referring back to  FIG. 1 , the second fluid pressure drop occurs when fluid reaches, and then passes across, focus rim  80 . At this location within enhancer  65 , the fluid is subject to an approximately 180-degree directional change as it travels along outer wall surface  72  of sleeve  70 , deflects off of wall surface  91  of flow focus element  90 , passes across focus rim  80 , and continues within the interior of sleeve  80  along inner wall surface  71  towards flow regulator  110 . Focus rim  80  at first end  73  of sleeve  70  is generally outwardly rounded, and preferably has a smooth rim surface. Disposed within wall surface  91  of flow focus element  90  is an annularly shaped recess  92  to aid in deflecting flow across focus rim  80 . Recess  92  is generally inwardly rounded, and preferably has a smooth wall surface without sharp angular contours. However, the shape of recess  92 , and of wall surface  91  in general, can be varied in order to regulate the pressure drop occurring at this location. Likewise, the shape of focus rim  80 , and the distance between focus rim  80  and flow focus element  90 , can also be varied depending on flow conditions to regulate pressure drop at this location and promote a smooth flow transition towards flow regulator  110 . 
   The third fluid pressure drop occurs at flow regulator  110 . The flow regulator will typically utilize a conventional valve design or some improvement thereupon.  FIG. 1  illustrates flow regulator  110  utilizing a simplified cage-type valve  140 , wherein pressure drop occurs as the fluid passes through multiple annular passages  141  in valve  140 . Alternatively,  FIG. 4  illustrates flow regulator  110  utilizing a simplified needle-type valve  130 , wherein pressure drop occurs as fluid passes between needle stem  131  and valve seat  132 . In each of the above-described embodiments, pressure drop occurs as a result of fluid flow through a decreased flow area. Other alternative embodiments of flow regulators may be used without deviating from the spirit of the present invention. 
   Referring to  FIG. 2 , a profile of the general fluid path through choke valve assembly  20  for a preferred embodiment of the invention is shown. Fluid enters choke valve assembly  20  at flow inlet  30 , encounters flow enhancement sleeve  70 , is directed with a degree of angular control within helical groove  120 , flows circumferentially around sleeve  70 , moves towards focus rim  80 , deflects off of flow focus element  90 , passes across focus rim  80 , continues towards flow regulator  110 , passes through flow regulator  110 , and exits choke valve assembly  20  at fluid outlet  40 . 
   In a preferred embodiment of the present invention, the fluid flow within fluid flow enhancer  65  undergoes three distinct pressure drops before exiting enhancer  65  via flow outlet  40 . However, it is also possible that any number of multiple pressure drops can occur within enhancer  65  without such variation deviating from the spirit of the invention, which generally pertains to causing multiple pressure drops within a choke valve assembly by effectuating changes in flow direction within the device. 
   It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials or embodiments shown and described, as obvious modifications and equivalents will be apparent to one skilled in the art. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.