Abstract:
Methods and apparatus for use in a welibore to meter and choke certain components from being produced, based upon their density relative to the density of oil are described herein. The device includes an inner tubular body portion having apertures in the wall thereof for passing oil, an outer tubular body and at least one metering orifice therebetween to meter production. Disposed around the inner body is an axially movable member to selectively cover and expose the apertures of the inner body, thereby permitting fluid to flow therethrough.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to the control of fluid flow into a wellbore. More particularly, the invention relates to a flow control apparatus that is self adjusting to meter production and choke the flow of gas into the wellbore. 
   2. Description of the Related Art 
   In hydrocarbon wells, horizontal wellbores are formed at a predetermined depth to more completely and effectively reach formations bearing oil or other hydrocarbons in the earth. Typically, a vertical wellbore is formed from the surface of a well and thereafter, using some means of directional drilling like a diverter, the wellbore is extended along a horizontal path. Because the hydrocarbon bearing formations can be hundreds of feet across, these horizontal wellbores are sometimes equipped with long sections of screened tubing which consists of tubing having apertures therethough and covered with screened walls, leaving the interior of the tubing open to the inflow of filtered oil. 
   Horizontal wellbores are often formed to intersect narrow oil bearing formations that might have water and gas bearing formations nearby.  FIG. 1  illustrates two such nearby formations, one of water and one of gas. Even with exact drilling techniques, the migration of gas and water towards the oil formation and the wellbore is inevitable due to pressure drops caused by the collection and travel of fluid in the wellbore. Typically, operators do not want to collect gas or water along with oil from the same horizontal wellbore. The gas and water must be separated at the surface and once the flow of gas begins it typically increases to a point where further production of oil is not cost effective. Devices have been developed that self adjust to control the flow of fluid into a horizontal wellbore. One such device is shown in U.S. Pat. No. 6,371,210 owned by the same assignee as the present invention and that patent is incorporated by reference in its entirety herein. The &#39;210 patent teaches a self-adjusting device that chokes the flow of fluid into a horizontal wellbore as the flow of fluid increases relative to a preset value determined by a spring member. Multiple devices can be placed along the length of a wellbore to help balance the inflow of production throughout the length of the wellbore. The device includes a piston that is depressed by a force generated by fluid flow. The device is especially useful when several are used in series along the length of a horizontal wellbore. However, the devices are not designed to meter production while choking unwanted production components due to its lack of a constantly sized orifice though which to meter the flow of production and determine the relative amounts of gas or water. 
   There is a need therefore, for a self-adjusting flow control apparatus for downhole use in a wellbore that operates to limit the inflow of gas or water into the wellbore when that component in a production stream reaches a predetermined percentage relative to the oil. There is a further need, for a flow control apparatus for use in a wellbore that is self-regulating and self-adjusts for changes in the amount of fluid and gas in a production stream. There is yet a further need for a flow control apparatus that meters the flow of production into a horizontal wellbore. 
   SUMMARY OF THE INVENTION 
   The present invention provides an apparatus for use in a hydrocarbon producing wellbore to prevent the introduction into the wellbore of gas and/or water when the gas or water is of a given percentage relative to the overall fluid content of the production. In one aspect of the invention, a perforated inner tube is surrounded by at least one axially movable member that moves in relation to a pressure differential between sides of a piston having at least one sized orifice through which the production flows to enter the wellbore. The movable member selectively exposes and covers the perforations of the inner tube to pass or choke production. In another embodiment, a method is disclosed to choke the flow of production into a wellbore when a predetermined component of the production is made up of gas or water. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, For the invention may admit to other equally effective embodiments. 
       FIG. 1  depicts a partial cross-sectional view of a vertical and horizontal hydrocarbon wellbore having a sand screen in the horizontal wellbore. 
       FIG. 2  is a partial cross-sectional view of the apparatus of the subject invention in an open position. 
       FIG. 3  is another cross-sectional view of the apparatus shown in a closed, choked position. 
       FIG. 4  is a cross-sectional view of a portion of the apparatus along a line  4 - 4  of  FIG. 2 . 
   

   DETAILED DESCRIPTION 
   The present invention is intended to effectively monitor and self adjust the flow of production into a wellbore depending upon the components in the production. To facilitate the description of the invention, the device will typically be described as it would function in the presence of gas and oil in a production stream. However, it will be understood that the invention operates primarily due to differences in densities between oil and another component of production in a wellbore and could operate in the presence of oil and water or any other component having a density distinct from oil.  FIG. 1  depicts a cross-sectional view of a well  200  having a flow control apparatus  212  of the present invention located therein. Specifically, an apparatus  212  for controlling the flow of oil or some other hydrocarbon from an underground reservoir  203  through the well  200  is depicted. The well  200  includes a cased, vertical wellbore  202  and an uncased, horizontal wellbore  204 . Production tubing  209  for transporting oil to the surface of the well is disposed within the vertical wellbore  202  and extends from the surface of the well  200  through a packing member  205  that seals an annular area  211  around the tubing and isolates the wellbore therebelow. The horizontal wellbore  204  includes a section of screened tubing  206 . The screened tubing  206  continues along the horizontal wellbore  204  to a toe  208  thereof. The apparatus  212  is attached to the screened tubing  206  near the heel  210  of the horizontal wellbore  204 . 
     FIG. 2  is a more detailed view of the apparatus  212  of the present invention. In the embodiment of  FIG. 2 , the flow control apparatus  212  is a two-position apparatus with a first position preventing the flow of production and a second position permitting the inflow of production into the production tubing  209 . The apparatus  212  is shown in the second, open position. The apparatus  212  is additionally designed to assume any number of positions between the first and second positions, thereby providing an infinitely adjustable restriction to the inflow of production into the interior of the device. 
   The apparatus  212  includes an inner tubular body  307  and an outer tubular body  324  disposed therearound. Disposed in an annular area  305  between the inner  307  and outer  324  bodies is an axially slidable sleeve member  311  which is biased in a first position relative to the inner body  307  by a spring  320  or other biasing member. In the position shown in  FIG. 2 , apertures  317  formed in the sleeve  311  are substantially aligned with mating apertures  308  formed in the inner body  307  to permit the passage of production fluid from the wellbore into the inner tube  307 . The production fluid flow into the apparatus is illustrated by arrows  313 . A piston surface  318  is formed on the sleeve  311  and is constructed and arranged to cause the sleeve  311  to become deflected and to move axially in relation to the inner body when acted upon by production fluid with sufficient momentum, mass and density to overcome the resistive force of the spring  320  and a pressure differential across the sleeve  311 . Specifically, the spring  320  is selected whereby a mass flow rate created by a pressure differential will result in a fluid momentum adequate to deflect the sleeve  311 , thereby shifting the apparatus  212  from the first fully closed position to the second, open position as it is shown in  FIG. 2 . 
   Formed in the piston surface  318  are at least one orifice  321  that meters the flow of production into the apparatus  212  and defines the pressure differential across the sleeve  311  based on flow rate and density of the fluids passing through the orifice  321 . In the design shown in  FIG. 2 , the only fluid path to the inner tube  307  is through the orifice  321  which is sized to permit flow but also to meter the production fluid as it travels through the sleeve  311 . In a preferred embodiment, when a certain percentage of the production fluid is made up of oil, its density will be adequate to cause a sufficient pressure differential as it flows through the orifice  321  to depress the sleeve  311  while an adequate amount flows through the orifice  321  sized to permit the flow of oil. If however, a substantial amount of gas is a component of the production fluid (or any other substance with a lower density than oil), the gas will not have adequate density to cause a sufficient pressure differential as it flows through the orifice  321  to depress the sleeve  311 , and any gas traveling through the orifice will be prevented from flowing into the wellbore. For some embodiments, the orifice  321  may not be formed in the sleeve  311  as long as the orifice  321  meters flow across the sleeve  311 . For example, the orifice  321  can be an insert that is locked (threaded, brazed, etc.) in place. 
     FIG. 3  is another section view of the apparatus  212  in the first or closed position. Accordingly,  FIG. 3  illustrates the position of the sleeve  311  when there is not an adequate amount of force to depress the piston surface  318  due possibly to a lack of density in some component of the production. 
     FIG. 4  is a section view illustrating the radially spaced orifices  321  formed in the sleeve  311 . In the embodiment shown, there are six orifices that serve to meter the inflow of production. The piston surface  318  which must be acted upon and depressed by pressure developed by the production fluid is the surface area of the face of the sleeve  311  less the area of the orifices  321 . The orifices are sized to meter the flow of production permitting an adequate amount to flow through while the surface area of the piston and the spring member  320  against which it must act are designed to require that the production be made up of some predetermined, minimum amount of higher density oil than some other lower density material, like water or gas. 
   While the invention has been described as being fully self adjusting, it will be understood that in some instances the device might be remotely adjusted from the surface using a hydraulic control line to artificially influence movement of the sleeve or a solenoid that is battery powered and can be signaled from the surface of the well. At least one pressure sensor (not shown) can sense a pressure value and communicate the pressure value to the solenoid. 
   While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.