Wells – Screens
Reexamination Certificate
1999-11-23
2001-10-09
Neuder, William (Department: 3672)
Wells
Screens
C166S232000
Reexamination Certificate
active
06298914
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains generally to well screens for oil, gas, mineral, and groundwater production, and groundwater monitoring, and more particularly to an improved one piece wire-wrapped well screen.
2. Description of the Background Art
When water, oil and gas producing wells are drilled through unconsolidated formations, the produced fluids generally contain particulate matter, usually sand. The production of sand, along with the fluids, is an undesired consequence because the sand causes extra wear and abrasion of production tubing, valves, pumps, and other equipment used to produce and remove fluids from the wells. It is therefore beneficial to avoid or minimize the production of sand or other particulate matter during the production of fluids from wells.
One method of accomplishing the reduction of sand or particulate production is by “gravel packing” the well during completion operations. Such gravel packing includes providing on the production conduit or tubular work string a slotted or ported cylindrically shaped member, generally known as well screens, which restricts the passage of particles into the interior of the conduit. For many years, well screens have been used in wells to permit fluid to flow through the screen and into the well while retaining sand and other particulate matter outside the well screen.
A common well screen design uses longitudinal supports tangentially welded to a helical band to produce a frame upon which strainer elements or inserts are attached. The strainer elements or inserts fill the gaps between the longitudinal and helical bars and serve to retain sand and other particulate matter. In such designs, the filtration screen is not self-supporting and is dependent on the frame for rigidity.
Other designs of well screens incorporate “projections” that are formed in a stack of rings and which protrude parallel to the longitudinal axis of the structure and perpendicular to the rings. This enables installers to adjust the gap between the rings during installation of the well screen. However, the projections do not provide structural rigidity to the screen and merely rest on the inner surface of the rings, thereby resulting in an undulated inner well screen surface.
Current screen design practice assumes a 1% ellipticity, which significantly reduces collapse strength and requires use of excess materials in order to achieve the desired resistance. The general tensile calculation for conventional wire wrap screens includes an approximate 30% welding de-rating effect due to welding of the wire or ring apex to the rod tangent, which is also a corrosion enhancer. Wire/rod screens have no torsional qualities. Corrosion, well construction defects, or manufacturing errors occasionally lead to holes or cracks in well casings or screens. One approach toward repair is to spot a serrated piece of slightly under-sized casing and hydraulically pressing this piece over the problem area, essentially forming a patch. This is impractical due to the presence of vertical rod protrusions in conventional wire wrap screens.
Conventional wire wrap screens normally show mostly steel, not open area available for fluid to flow through. The usual range of open area percentage exposed to abutting geological formations is 20%-50% with a fluid entrance efficiency of approximately 90% at best.
BRIEF SUMMARY OF THE INVENTION
By way of example and not of limitation, the present invention is a well screen which generally comprises a wire which is spirally wound to form a cylinder with spaces between each layer of wire. Spacers between the wire at intervals around the circumference of the well screen serve to attach the layers of wire together. The spacers do not extend radially beyond the inner or outer edge of the wire. The spacers can be flush with either the inner and/or outer edge of the wire or recessed from either the inner and/or outer edge of the wire. The spacers are permanently and securely attached to the wire by means such as welding, resulting in a single unitized well screen that is also very structurally rigid.
In an alternate embodiment of the invention, the well screen comprises a plurality of rings stacked atop one another and connected together by spacers located at intervals around the circumference of the rings, generally forming a cylinder. The spacers do not extend radially beyond either the inner or outer edge of the rings. The spacers can be flush with either the inner and/or outer edge of the ring or recessed from either the inner and/or outer edge of the ring. The spacers are attached to the rings in the same manner as with the spiral wire well screen design.
The rings or wire may also have the spacers integrated into the top, bottom or top and bottom surfaces in alternative embodiments. This integrated spacer embodiment allows the wire or steel rings to be joined by fillet welds on a single surface thereby reducing the total number of welds required to manufacture the screens. It should also be understood that the rings can be manufactured from a variety of materials by a variety of processes such as forging, stamping, extruding, molding and casting.
This spacer/wire and spacer/ring design allows for fabrication and use of any thickness or width of wire or ring. By increasing wire or ring thickness and essentially melting the vertically oriented rod components of wire wrap screen into the thickness of the rings, and then welding these in place, superior strength is created even with less width profile. Since it is advantageous to provide more open area through which the fluid can enter the screen, aperture dimensions can be varied by adjusting ring thickness, width, spacer dimensions, spacer shapes, placement and orientation, in order to improve fluid flow therethrough, while simultaneously increasing strength and rigidity and reducing material requirements.
The spacer shape is variable, which allows the manipulation of fluid dynamics. Improved fluid flow characteristics can be achieved, thus increasing flow efficiency while reducing corrosion and plugging tendencies of conventional well screen designs.
Since the spacers do not extend beyond the inner surface of the well screen, the flush inner surface of the well screen also allows ready installation of “swaged” patches for damage repair and eases repair when fissures develop during use. The flush inner surface allows the use of zone isolation devices with greater effectiveness. The flush inner surface also allows rotation activities within the screen without interference or catching of rods on the rotating device which would otherwise damage or destroy the screen.
This design eliminates or minimizes problems associated with tangential welding and normal stress points as such welds are more robust and less susceptible to corrosion. In addition, any length of well screen can be easily manufactured because no rods are used.
In another embodiment, the outside diameter of the wire or rings forming the exterior surface of the screen, is formed into a distinct shape, such as a generally square shaped edge. It should be understood to one skilled in the art that any number of shapes could be utilized.
In yet another embodiment of the invention, the screen is formed by the machining of processed tubes to include all of the spacing, angles and other design features disclosed herein. Such machining may include precision milling, Electrical Discharge Machining (EDM), Electron Beaming (EB), Plasma cutting, laser cutting and the like.
An object of the invention is to provide a one-piece rigid well screen which is self-supporting, has increased structural strength and which can be manufactured efficiently and reliably.
Another object of this invention is to provide a greater area through which fluid can flow, thus enhancing the fluid entrance capability and efficiency.
Yet another object of the invention is to provide for a flush inn
Schwimmer Donald D.
Spray Jeffery A.
Neuder William
O'Banion John P.
Spray Jeffery A.
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