Expandable screen utilizing near neutrally-buoyant particles outside of the screen

Abstract

In one embodiment, a wellbore completion method includes disposing an expandable screen into a well bore and disposing a fluid into an annular space between a wall of the wellbore and the expandable screen. The fluid contains a plurality of near neutrally-buoyant particles. The method further includes radially expanding the screen, whereby the near neutrally-buoyant particles exert a force against the wall of the wellbore.

Description

RELATED APPLICATIONS

This application claims the benefit of Ser. No. 60/532,933, entitled “Expandable Sand Screen Utilizing Near Neutrally Buoyant Particles Outside of Screen,” filed provisionally on Dec. 29, 2003.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to the field of well bore completion and, more particularly, to an expandable screen utilizing near neutrally-buoyant particles outside of the screen.

BACKGROUND OF THE INVENTION

Sand control is important during completion and subsequent production of a wellbore that is in hydraulic communication with Earth formations susceptible to production of solid materials from the formation. Such formations are known in the art as “unconsolidated” and, if not protected with suitable wellbore equipment, may produce solid materials of a character and quantity so as to damage the wellbore, or at least reduce its capacity to produce oil and gas from the formation. Devices known in the art as “sand screens” are typically used to protect such unconsolidated formations. Sand screens include a structural member, called a “base pipe”, having apertures therein to maintain the mechanical integrity of the sand screen (meaning to provide mechanical support for the screen. A “filter layer” is typically disposed outside the base pipe. Many different types of filter layer are used, including, for example, wound wire and mesh screen.

More recently, radially plastically deformable sand screens, called “expandable sand screens” have been used in some wellbores to increase productivity of wellbores completed in unconsolidated Earth formations. A principal reason for the use of expandable sand screens is to mechanically support the unconsolidated formation prior to initiating fluid production. By supporting the formation prior to initiating production, it is possible to reduce loss of formation permeability due to movement of solid materials against the screen during fluid production. A conventional (non-expandable) sand screen must necessarily have an external diameter smaller than the drilled out diameter of the wellbore (“open hole”) prior to insertion of the sand screen, in order for the screen to fit in the wellbore. The smaller screen diameter results in an annular space between the outer surface of the screen and the wall of the wellbore, which may become filled with formation solids moved from the formation during fluid production. Expandable sand screens are intended to provide a way to close the annular space prior to beginning fluid production, and thus prevent movement of formation solids. Expandable sand screens are run into the wellbore in an unexpanded state, wherein the external diameter of the screen is less than the drilled out diameter of the wellbore. After insertion, the screen is expanded using one or more types of expansion tools, preferably to cause the screen to be placed into firm contact with the wellbore wall.

During the expansion of expandable sand screens, it is advantageous to push the sand screen outward to an extent so that it “conforms” to, and applies pressure to, the wellbore wall in order to hold the sand in place and increase oil and/or gas flow into the wellbore. Many wellbores may include sections where the actual diameter of the wellbore exceeds the drilled out diameter (drill bit diameter) due to washout or other cause. In such sections, it maybe necessary to expand a screen to 35 or 40 percent greater than its unexpended diameter in order to place the screen in form contact with the wall of the wellbore.

One problem with expandable screens known in the art is that they are difficult to expand more than about 30 to 35 percent because the base pipes made out of carbon steel or stainless steel begin to fail. As a result, these screens may often not be expanded enough to apply the high contact pressures needed to hold the sand in place in enlarged wellbores, thus resulting in failure of the sand screen or inadequate production. Conversely, if expanded to the degree necessary to provide a suitable amount of contact pressure, the base pipe may be weakened to an extent so as to have very little resistance to crushing under external pressure, thus leaving the wellbore susceptible to failure.

SUMMARY OF THE INVENTION

It is desirable to have an expandable sand screen that can be made to conform to the wall of a wellbore, even if it is necessary to expand the screen to 35 percent or more beyond the unexpanded diameter of the screen, while maintaining sufficient mechanical integrity to resist failure of the screen and consequent loss of the wellbore.

In one embodiment, a wellbore completion method includes disposing an expandable screen into a wellbore and disposing a fluid into an annular space between a wall of the wellbore and the expandable screen. The fluid contains a plurality of near neutrally-buoyant particles. The method further includes radially expanding the screen, whereby the near neutrally-buoyant particles exert a force against the wall of the wellbore.

Embodiments of the invention may provide a number of technical advantages. In one embodiment, placement of neutrally-buoyant or near-neutrally-buoyant particles in the annular space outside of the screens makes the screens compliant and allows them to exert a force against the wall of a wellbore and hold the sand particles in place. This facilitates the use of strong base pipe with high torsional, axial, and collapse strength.

Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are cross-sectional elevation views illustrating a wellbore completion method in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

FIGS. 1 and 2 are cross-sectional elevation views illustrating a wellbore completion method in accordance with one embodiment of the present invention. Referring first to FIG. 1, a wellbore completion system 100 is utilized in completing a wellbore 101 drilled within a formation 102. Wellbore 101 may be drilled using any suitable drilling techniques and may have any suitable diameter, length, and direction. Formation 102 may be any suitable geological formation; however, the present invention is particularly suitable for unconsolidated formations, such as sandstone.

Holding the sand or other particles from formation 102 in place during the completion process is important for effective oil and/or gas flow into wellbore 101. Thus, expandable sand screens are sometimes utilized to hold the sand in place. A major problem with prior expandable sand screens is that they are difficult to expand more than about 30-35% before the base pipes from which they are made begin to fail. Thus, these prior screens may often not be expanded enough to apply high contact pressures to hold the sand in place.

Therefore, according to the teachings of one embodiment of the invention, a plurality of near neutrally-buoyant particles 106 are disposed within an annular space 108 between a wall 109 of wellbore 101 and an expandable screen 104 prior to expanding expandable screen 104. Near neutrally-buoyant particles 106 reduce the amount of expansion required by expandable screen 104 and increases the contact force between expandable screen 104 and wall 109. In the illustrated embodiment, near neutrally-buoyant particles 106 are disposed within a fluid 115.

Expandable screen 104 may be any suitable screen of any suitable size and configuration, and may be formed from any suitable material. For example, expandable screen 104 may be formed from a suitable carbon steel and include a fine screen or coarse screen (or both) inside of a suitable sleeve (sometimes referred to as a “shroud”) having suitable apertures formed therein. Expandable screen 104 may also have any suitable length and may be formed from one or more sections. If expandable screen 104 is formed from more than one section, then expandable threads 112 may be utilized to couple the sections together. Expandable screen 104 may be disposed in wellbore 101 by any suitable method, such as the utilization of a suitable work string 110. Any suitable method may be utilized to expand expandable screen 104, such as a cone expander 114 or other suitable expander element.

Near neutrally-buoyant particles 106 may be any suitable particles formed from any suitable material. As used herein, the term “near neutrally-buoyant” means that particles 106 each have a density that is equal to or very near the density of fluid 115 in which they are suspended. As examples, near neutrally-buoyant particles 106 may be hollow or low density particles. Although near neutrally-buoyant particles 106 may have any suitable size and shape, in one embodiment, near neutrally-buoyant particles 106 are generally spherical in shape having any suitable diameters. In a particular embodiment of the invention, the near neutrally-buoyant particles 106 are generally spherical in shape and have diameters larger than the diameters of the pores existing within formation 102 adjacent wall 109 in order to prevent them from flowing into and plugging the pores in formation 102. With respect to expandable screen 104, in one embodiment, near neutrally-buoyant particles 106 may be generally spherical in shape and have diameters larger than the diameters of the holes formed within the outermost member of expandable screen 104, such as a shroud. In one embodiment, this prevents the near neutrally-buoyant particles from damaging the fine screen inside of the shroud.

Fluid 115 may be any suitable fluid. For example, in one embodiment, fluid 115 is a suitable completion fluid. In addition, fluid 115 may be disposed within annular space 108 between wall 109 and expandable screen 104 in any suitable manner using any suitable equipment, such as a pump.

In some embodiments, fluid 115 develops “gel” strength when it is not being circulated. This gel strength allows near neutrally-buoyant particles 106 to be suspended in fluid 115 even though their densities are slightly different than fluid 115. Therefore, in some embodiments, the densities of near neutrally-buoyant particles 106 do not have to equal the density of fluid 115 to be suspended therein.

In one embodiment, some of the near neutrally-buoyant particles 106 each have a density slightly greater than fluid 115 such that they tend to fall within fluid 115 prior to expansion of expandable screen 104, and some of the near neutrally-buoyant particles 106 each have a density slightly less than fluid 115 such that they will tend to rise within fluid 115 prior to expansion of expandable screen 104. This may improve the placement of particles 106 in annular space 108 around screen 104. In another embodiment, near neutrally-buoyant particles 106 each have a density equal to fluid 115 such that particles 106 substantially remain in place around expandable screen 104 prior to expansion thereof with no tendency to rise or fall within fluid 115. Other methods for moving and/or locating particles 106 within fluid 115 are contemplated by the present invention. It should be noted that larger near neutrally-buoyant particles 106 may tend to sink or float faster than smaller particles. Thus, as near neutrally-buoyant particles 106 get larger, the difference in density between near neutrally-buoyant particles 106 and fluid 115 may be smaller in order to suspend them in fluid 115.

System 100 may also include a first barrier 118 coupled near a top of expandable screen 104 and a second barrier 120 coupled near a bottom of expandable screen 104. Barriers 118, 120 may be utilized to confine the near neutrally-buoyant particles 106 to a particular vertical space within annular space 108 of wellbore 101. Barrier 118 and barrier 120 may be any suitable barriers formed from any suitable material, such as an elastomer. Barriers 118, 120 are typically coupled to the outside of expandable screen 104 before expandable screen 104 is disposed within wellbore 101.

A bottom sub 122 may also be coupled to a bottom of expandable screen 104 to prevent any fluid 115 from exiting expandable screen 104. Bottom sub 122 may be any suitable plug formed from any suitable material and may coupled to expandable screen 104 in any suitable manner.

Also illustrated in FIG. 1 is a casing 124, which may case any suitable portion of wellbore 101, and an expandable liner hanger 126 that functions to hang any suitable lining within casing 124. The present invention contemplates more, fewer, or different components than those illustrated in FIG. 1.

In operation of one embodiment of the invention, and with reference to FIGS. 1 and 2, wellbore 101 is first drilled by any suitable method within formation 102 and the upper portion thereof cased with casing 124. Expandable liner hanger 126 is utilized to position expandable screen 104 within wellbore 101. Work string 110 with cone expander 114 coupled thereto is then run-in-hole and fluid 115 is circulated down into wellbore 101. Fluid 115, with near neutrally-buoyant particles 106 suspended therein, fills annular space 108.

Work string 110 then is utilized to apply weight to cone expander 114, which translates downward and starts radially expanding expandable screen 104, as illustrated best in FIG. 1. Cone expander 114 plastically deforms expandable screen 104. As expandable screen 104 is radially expanded out towards wall 109, near neutrally-buoyant particles 106 exert a force against wall 109 in order to hold the sand associated with formation 102 in place. In the illustrated embodiment, the near neutrally-buoyant particles 106 have diameters larger than the pores existing in formation 102 in order to prevent them from flowing into and plugging the pores. Once cone expander 114 reaches the end of its desired travel, then work string 110 and cone expander 114 are pulled out of wellbore 101, thereby leaving the arrangement illustrated in FIG. 2.

As shown in FIG. 2, expandable screen 104 is radially expanded outward towards wall 109 and applies a force to near neutrally-buoyant particles 106 so that they may exert a force on wall 109 of wellbore 101. Expandable screen 104 is thus plastically deformed from a smaller diameter to a larger diameter. Any suitable expansion is contemplated by the present invention.

Thus, near neutrally-buoyant particles 106 within annular space 108 facilitate expandable screen 104 being compliant and holds sand particles associated with formation 102 in place by exerting a force against wall 109. This may allow the use of a strong base pipe with expandable screen 104 with high torsional, axial and collapse strength. Efficient production from wellbore 101 may then be realized.

Although embodiments of the invention and their advantages are described in detail, a person of ordinary skill in the art could make various alterations, additions, and omissions without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A wellbore completion method, comprising:

disposing an expandable screen into a wellbore;

disposing a fluid into an annular space between a wall of the wellbore and the expandable screen, the fluid containing a plurality of near neutrally-buoyant particles; and

radially expanding the screen, whereby the near neutrally-buoyant particles exert a force against the wall of the wellbore.

2. The method of claim 1, wherein the near neutrally-buoyant particles have a density equal to the fluid such that the near neutrally-buoyant particles substantially remain in place around the screen prior to radial expansion with no tendency to rise or fall.

3. The method of claim 1, wherein some of the near neutrally-buoyant particles have a density slightly greater than the fluid density such that they will tend to fall within the fluid prior to expansion and some of the near neutrally-buoyant particles have a density slightly less than the fluid density such that they will tend to rise within the fluid prior to expansion.

4. The method of claim 1, wherein the near neutrally-buoyant particles comprise generally spherical particles having diameters larger than the diameters of the pores existing within a formation associated with the wall of the wellbore.

5. The method of claim 1, wherein the fluid comprises a completion fluid.

6. The method of claim 1, further comprising placing a barrier in the annular space near a top of the screen.

7. The method of claim 1, further comprising placing a barrier in the annular space near a bottom of the screen.

8. A wellbore completion system, comprising:

an expandable screen configured to be disposed into a wellbore;

a fluid containing a plurality of near neutrally-buoyant particles;

a pump operable to dispose the fluid into an annular space between a wall of the wellbore and the expandable screen; and

an expander operable to radially expand the screen when disposed within the wellbore, whereby the near neutrally-buoyant particles exert a force against the wall of the wellbore.

9. The system of claim 8, wherein the near neutrally-buoyant particles have a density equal to the fluid such that the near neutrally-buoyant particles substantially remain in place around the screen prior to radial expansion with no tendency to rise or fall.

10. The system of claim 8, wherein some of the near neutrally-buoyant particles have a density slightly greater than the fluid density such that they will tend to fall within the fluid prior to expansion and some of the near neutrally-buoyant particles have a density slightly less than the fluid density such that they will tend to rise within the fluid prior to expansion.

11. The system of claim 8, wherein the near neutrally-buoyant particles comprise generally spherical particles having diameters larger than the diameters of the pores existing within a formation associated with the wall of the wellbore.

12. The system of claim 8, wherein the fluid comprises a completion fluid.

13. The system of claim 8, further comprising a barrier coupled near a top of the screen.

14. The system of claim 8, further comprising a barrier coupled near a bottom of the screen.

15. The system of claim 8, wherein the expander comprises a cone expander.

16. A method for expanding an expandable screen within a wellbore, comprising:

disposing a fluid containing a plurality of near neutrally-buoyant particles into an annular space between the expandable screen and a wall of the wellbore; and

expanding the screen in such a manner that the near neutrally-buoyant particles exert a force against the wall of the wellbore.

17. The method of claim 16, wherein the near neutrally-buoyant particles have a density equal to the fluid such that the near neutrally-buoyant particles substantially remain in place around the screen prior to expansion with no tendency to rise or fall.

18. The method of claim 16, wherein some of the near neutrally-buoyant particles have a density slightly greater than the fluid density such that they will tend to fall within the fluid prior to expansion and some of the near neutrally-buoyant particles have a density slightly less than the fluid density such that they will tend to rise within the fluid prior to expansion.

19. The method of claim 16, wherein the near neutrally-buoyant particles comprise generally spherical particles having diameters larger than the diameters of the pores existing within a formation associated with the wall of the wellbore.

20. The method of claim 16, further comprising defining a cylindrical volume for the near neutrally-buoyant particles by placing a first barrier in the annular space near a top of the screen and a second barrier in the annular space near a bottom of the screen.