MXPA99007434A - Prepacked flush joint well screen - Google Patents

Abstract

A prepacked well screen has concentric inner (10) and outer (11) fiber reinforced composite tubes with a granular filter medium (13) in the annulus between the inner (10) and outer (11) tubes. The walls of the tubes are slotted (12) for passing fluid through the slots (12) and the filter medium (13). Each end of the inner tube (10) extends beyond the adjacent end of the outer tube (11) and has a male thread (16). A connection is made to an adjacent well screen or other tube by a female coupling member (18) threaded onto the male thread (16). An advantage of the design is that the coupling member (18) connected to the inner tube (10) has an outside diameter approximately the same as the outside diameter of the outer tube (11).

Description

MESH FOR JOINT WELL AT LEVEL, PREEMPAQUE ADA Background of the Invention This invention relates to a mesh or screen used in oil or water wells or the like, to prevent sand or other debris from entering the pipe used for the production of oil or oil or water. Well screens have been used for many years to limit the production of sand and other debris in water, oil and gas wells. Well meshes are simply filters that hold sand in the well, eliminating the need to separate the sand from the fluid produced at some later stage in the process. In a typical installation, a housing or case extends downwardly from the borehole of a well and the fluid produced is pumped from within that housing. In many wells a perforated housing can be used to recover the fluid. In some places, there are loose particles of formation (commonly referred to as 'sand', even though it is not sand technically) REF: 31094 which can be dragged in the fluid.It is very desirable to prevent such sand from entering the pipeline. In this way, a sand filter or well screen is attached to the bottom of the pipe, such a well screen can be extended many feet through a production formation, some of the well screens are more of a design. simple: a piece of steel tube with small openings slotted or punched through the wall of the tube.The openings machined in the wall of the tube are either smaller than the sand particles of the well, or the sand of a size of Larger grain than the openings is packaged around the pit mesh in the borehole, to serve as a filter.This "gravel pack" around the pit mesh filters the smallest sand particles Other meshes are more complex, using a filter medium such as a porous metal, sand with controlled grain size, or a fine mesh to filter the sand. There have been recently developed fiberglass well screens that are pre-packed with sand. A pre-packaged, exemplary fiberglass well screen comprises epoxy tubes reinforced with internal and external fiber. The annular space between the tubes is filled with a sand of controlled grain size to act as a filter medium. The inner and outer tubes are grooved with a narrower groove width than the grain size of the packed sand within the ring. Conventional well screens or screens are assembled end to end with couplings to obtain a desired total mesh length in the well. These tube couplings have a larger diameter than the well mesh. It is desirable to have a wellbore mesh with a large diameter as this increases the mesh area, which not only improves the flow velocity through the mesh, but can also prolong the life time of the mesh before it the filter becomes plugged. A problem with the previous couplings has been that the meshes fitted in a well bore must be appreciably smaller than the hole or borehole, so that the couplings can be adjusted into the borehole. Thus, for example, in a 100 mm (4 inch) orifice, the well screen has couplings close to the borehole diameter and the screen itself has an external diameter of only about 73 mm. The larger meshes can be used since the couplings may not fit within the 100 m perforation. It is therefore desirable to provide a well screen having an outer diameter approximately equal to the external diameter of the couplings.

Brief Description of the Invention It is therefore provided in the practice of this invention, according to a currently preferred modeA prepackaged screen or screen for well having internal and external concentric tubes with the inner tube extending longitudinally out of at least one end of the outer tube. The ring or crown between the tubes is closed at each end and filled with a filter medium. The walls of the inner and outer tubes are perforated to allow fluid flow, through the perforations and the filter medium. A male thread is formed on the protruding end of the inner tube to receive a female coupling member having an outer diameter approximately equal to the outer diameter of the outer tube.

Drawing These and other features and advantages of the present invention will be better understood by reference to the accompanying drawing, which illustrates a pre-packaged pit mesh assembly, partially in longitudinal cross-section.

Detailed description The pre-packaged well mesh comprises an inner tube 10 concentric with an outer tube 11. The inner and outer tubes are each made of epoxy, polyester, phenolic or phenolic-siloxane resin, reinforced with glass fiber. In a typical embodiment for use in a 100 mm (4 inch) diameter well, the outer diameter of the outer tube is approximately 95 mm and its internal diameter is approximately 85 mm. Thus, the wall thickness of the outer tube is about 5 mm. The inner tube in such an embodiment has an outer diameter of about 74 mm and an internal diameter of about 63 mm. The wall thickness of the inner tube is approximately 5.7 mm. The ring or crown between the inner and outer tubes is approximately 5.3 mm wide. Each of the inner and outer tubes have a plurality of grooves 12 extending longitudinally through the wall of the tube. In an exemplary embodiment, the slots are approximately 0.25 mm in width and 75 mm in length. Such grooves are formed by sawing with a circular, thin diamond saw. The slots are sawn before the tubes are assembled with each other. In the illustrated mode, the groups of three slots are closer together, with a somewhat wider space between the groups. Six to eight such groups are provided around the circumference of the tubes. About half a dozen bands of grooves are provided along the length of a section of the well screen. Other slot fixes can be used.

The ring or crown between the two tubes is filled with silica sand 13. The sand is preferably of a uniform grain size which passes through a 20 mesh screen and is retained on a 40 mesh screen. The grain size of the sand is in the range of approximately 0.37 to 0.76 mm. The sand can be placed in the ring or crown by erecting the tubes vertically, making them vibrate and emptying the sand inside the ring or crown. The tubes are kept coaxial during filling, to obtain a uniform thickness of the granular filter medium. Other filter media can also be used in the ring between the inner and outer tubes. For example, a fiberglass mesh layer may be wrapped around the inner tube prior to insertion through the outer tube. Similarly, a porous metal sheet can be placed in the ring or crown. A granular filter medium is desirable since it can be easily placed in the ring after the tubes are assembled, and the sand is very cheap. The outer tube is shorter than the inner tube, so that each end of the inner tube projects beyond the end of the outer tube. A ring-shaped spacer or "sealing piece" 14 is connected in place between the inner and outer tubes adjacent to each end. One of the sealing pieces is bonded by cement in place before the granular filter medium is added. After filling the ring or crown with sand, the second sealing piece is cemented in place. A male thread 16 is formed on the protruding end or "spigot" of the inner tube at each end of the tube assembly. An exemplary thread has an 8-step thread shape having a spacing of about 3 to 6 mm, and a thread depth of about 2 mm. Preferably, the thread is tapered at about 1 ° to form an assurance thread. The threaded pin extends 60 to 70 mm beyond the outer tube at one end of the assembly. A similar spike length is used at the other end, and there is a short cylindrical extension 17 of the inner tube, beyond the end of the outer tube before the thread begins. Although a shallow thread of 8 rungs is employed in the illustrated embodiment, other thread shapes and dimensions may also be used. A coupling member 18 having a female thread is threaded onto a male tang end of the inner tube. Such coupling member is illustrated at one end of the well mesh assembly in the drawing. A mesh assembly for the well and the coupling typically has a length of about 3.7 meters, or about half the length of the typical production pipe. The couplings are used for mounting a plurality of end-to-end well meshes for a desired length in the well bore. At the bottom of the row of well meshes, an unthreaded coupling member can be used as a cover for closing the end of the well screen. At the upper end of a row of well meshes, a coupling member may have a thread on one end to be attached to the threaded end of the inner tube, and on its other end a standard API thread for mounting on the production line which extends from the filter to the floor surface.

When the coupling is threaded onto a male shank at the end of the well screen having a cylindrical extension 17 between the thread and the end of the outer tube, the coupling is secured against the tapered thread, before reaching the end of the outer tube , whereby an empty space is left which has a smaller diameter than the coupling and the outer tube. This empty space can be used to receive a C-shaped plate used in the head of the well to support the meshes for well during the assembly and installation of the various lengths of the mesh for well. The coupling member has an outer diameter approximately equal to the outer diameter of the outer tube, and certainly not significantly larger than the outer diameter of the outer tube. For example, in the exemplary embodiment described and illustrated, the coupling has an outer diameter of about 95 mm to fit within a 100 mm well bore. Since the outer diameter of the outer tube is approximately equal to the diameter of the coupling, the mesh area of the well screen is significantly increased, compared to composite, fiber reinforced well meshes of the prior art, with couplings on the outer tube. For example, in a well screen for a 100 mm well hole, a pre-well screen could have an outer diameter of about 73 mm. Such a well screen has a mesh surface area of approximately 0.73 irr per meter of mesh length. A mesh for a well where the outer diameter of the outer tube is approximately the same as the diameter of the coupling (for a 100 mm well) has a mesh surface area of approximately 0.98 pr per meter of mesh length. This is approximately an increase of 35% in the surface area of the mesh, which translates directly into increased production and a longer mesh life before the mesh is plugged. In addition, there is less pressure drop inside the inner tube, since its diameter is more than 25% greater than the previous mesh. Another advantage of the mesh for composite well, reinforced with fiber, is that it is easily drilled from the well. There may be occasions when a well mesh is separated from the production pipeline and lost at the bottom of a well. For example, a fiber reinforced epoxy bottom element having a reduced cross-sectional area that will fail at a predetermined tensile load can be installed at the top of a row of well meshes. The well meshes below this deliberately weakened section can become attached to the well bore as sand particles formed in the well around the meshes. In some wells it may be desirable to add a "gravel pack" around a mesh screen as described above, to pre-filter the fluid before it reaches the slits in the screen. The use of a gravel pack almost ensures that the well screen is adhered to the well. In that case, the production pipe can be pulled and the row broken in the weakened joint, leaving the meshes for well in the hole. Epoxy well screens, reinforced with fiberglass, are easily knurled from light drilling equipment or reconditioning equipment to eliminate the lost meshes from the hole in the well. A steel mesh is much harder to fish or knurl.

The pre-packaged well screen has been described in an exemplary manner for a 100 mm well hole. This is desirable since such small diameter wells are quickly and economically drilled. Therefore, a narrower well spacing can be used for improved production from low permeability formations. Larger well meshes can be used, such as, for example, approximately 120 mm in diameter for a standard size well hole with a diameter slightly greater than 125 mm. As mentioned above, such pre-packaged well meshes can be used for the production of water, oil or petroleum, gas or other fluids. Composite well meshes, reinforced with fiber are desirable in such service, due to the corrosion resistance. Some well meshes are made of expensive stainless steel for service in corrosive environments. Reinforced fiber-reinforced composite well screens are considerably less expensive than steel meshes and even more economical compared to stainless steel meshes.

Another distinct advantage of a fiber reinforced composite well screen is the ability to make relatively sharp turns in a well hole. In recent years, a reactivation of more or less horizontal perforation has been observed. Such a well is drilled vertically at a desired level of formation and then the hole in the well gradually rotates to be drilled at an angle. Well meshes placed in such a well bore must be flexed to pass through the underground loops of the well. It has been shown that fiber reinforced composite well meshes can rotate through many turns of radius tighter than the steel well meshes can turn, without bulging or collapsing. Although the pre-packaged well screen has been described with a male thread at each end and a separate coupling, it will be apparent that a well screen could also be fabricated with a male thread on the inner tube at one end, and a female thread at a extended sealing piece in the outer tube at the opposite end. In such an embodiment, the end of an adjacent well mesh could be considered as the female coupling member. An arrangement as illustrated is preferred, since the inner tube with the male thread at each end forms a tension member that supports the well meshes in the well bore, without any need for shear load transfer, appreciable between the inner tube and a spacer or "extreme sealing piece." In the preferred arrangement, the ends of the inner tube extending beyond the end of the outer tube are threaded for the reception of a female thread coupling member. adhesively an outer surface of the inner tube to the inside of an outer tube or sealing piece on an adjacent well screen or connecting underground member.The time to constitute such joints or joints in the head of the well can be excessive.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following:

Claims (16)

RE IVINDICAC IONS

1. A screen or mesh for well, pre-packaged, characterized in that it comprises: a composite outer tube, reinforced with fiber; a composite inner tube, reinforced with fiber, concentric with the outer tube, and having at least one end extending beyond one end of the outer tube; a filter medium in a ring or crown between the tubes; a plurality of perforations through the walls of the inner and outer tubes, to pass the fluid through the tubes and the filter medium; a male thread formed on at least the extending end of the inner tube; and a female coupling member connected to the male thread, having an outer diameter not significantly greater than the outer diameter of the outer tube.

2. A well screen according to claim 1, characterized in that each tube comprises fiberglass reinforced resin, selected from the group consisting of epoxy, polyester, phenolic and phenolic-siloxane resin.

3. A mesh for a well according to claim 1, characterized in that each tube comprises an epoxy resin reinforced with glass fiber.

4. A well screen according to claim 1, characterized in that the filter means comprises a granular material that fills the ring or crown.

5. A mesh for a well according to claim 1, characterized in that the filter means comprises grains of sand in the ring.

6. A well screen according to claim 5, characterized in that each of the inner and outer tubes comprises a plurality of longitudinal grooves having a width narrower than the size of the sand grains.

7. A well screen according to claim 1, characterized in that it has both ends of the inner tube that extend beyond the respective ends of the outer tube, and that they have a male thread on each of the extending ends.

8. A well screen according to claim 7, characterized in that it further comprises an extension of the inner tube between the beginning of the thread on an extending end and the adjacent end of the outer tube, whereby a free space is formed between the coupling member and the end of the outer tube.

9. A mesh or sieve for well, prepackaged, characterized in that it comprises: glass fiber reinforced, concentric tubes, internal and external extending the inner tube longitudinally out of at least one end of the outer tube; means for closing a ring or crown between the inner and outer tubes adjacent to each end; a filter medium in the ring or crown between the inner and outer tubes; a plurality of grooves through the walls of the inner and outer tubes, to pass the fluid through the grooves and the filtering means - a male thread on the end of the inner tube, which extends outside the outer tube; and a female coupling member threaded onto the male thread, the coupling member having an outer diameter approximately equal to the outer diameter of the outer tube.

10. A well screen according to claim 9, characterized in that both ends of the inner tube extend beyond the respective ends of the outer tube and that they have a male thread on each of the extending ends.

11. A well screen according to claim 10, characterized in that it further comprises an extension of the inner tube between the beginning of the thread on an extending end and the adjacent end of the outer tube, to form a free space between the coupling member and the end of the outer tube.

12. A well screen according to claim 10, characterized in that each tube comprises fiberglass reinforced resin, selected from the group consisting of epoxy, polyester, phenolic and phenolic-siloxane resin.

13. A mesh for a well according to claim 12, characterized in that each tube comprises epoxy resin reinforced with glass fiber.

14. A mesh for a well according to claim 9, characterized in that the filter means comprises a granular material that fills the ring or crown.

15. A mesh for a well according to claim 14, characterized in that the size of the grains of the filter material are larger than the grooves in the tubes.

16. A mesh for a well according to claim 9, characterized in that the filter means comprises grains of sand in the ring or crown.