Patent Publication Number: US-2005126779-A1

Title: Seamless woven wire sintered well screen

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of U.S. provisional application No. 60/528,344 filed Dec. 10, 2003. 
    
    
     STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not applicable.  
     REFERENCE TO A MICROFICHE APPENDIX  
      Not applicable.  
     BACKGROUND OF THE INVENTION  
      Current embodiments pertaining solely to the utilization of nickel alloy diffusion bonded sintered metal filters in downhole installations are limited to two (2) embodiments. One embodiment uses sintered porous powdered metal which can either be manufactured seamless or press-rolled and welded (U.S. Pat. No. 5,293,935 to Arterbury et.al). In another patent, short sections are welded or mechanically attached (Lowery, Arterbury U.S. Pat. No. 5,318,119) over a perforated or slotted mandrel. Another embodiment in current use involves multi-layered sintered laminate plates calendared together and form-pressed to a tube shape. After forming in a press brake they are seam welded to retain tube shape and strength. In either diffusion bonded (sintered) design they can be employed as a component filter, or as a primary filter.  
      A problem, which arises with sintered powder well screens, is plugging of sand fines (debris) due to what is known as depth filtration. Uneven pore space openings can cause blockage in specific areas of the filter, which can result in high entrance velocities in others, resulting in erosion and failure.  
      Another problem that arises in this design is lack of malleability. Sintered porous powder well screens have a tendency to crack and split in bending applications such as those that are encountered in horizontal well bores.  
      A further problem that arises with sintered laminate tube well screen apparatus relates to the seam welding process. The flat “sheet” metal (which may be woven) is made up of differing layers of filter sheets that are manufactured into a sintered, diffusion bonded single element structure to insure a nominal or absolute filter capability, for example, micron rating, retention etc. In this configuration the sintered laminate well screen tube is seam-welded to maintain shape and integrity. As a result of the press-brake rolling and seam welding processes, many aspects of the procedure compromise the ability of the sintered welded tube to perform in its environment. Seam welded sintered laminate causes a heat affected zone particularly in the region of the weld that can and does create “burn through” by inconsistent heating during the welding process. Pin holes may develop as a result of the process which causes “hot spots” that may evolve into erosion failures. In addition, the heat-affected zone can also be subject to accelerated stress-crack corrosion due to harsh downhole well conditions (ie, temp/chlorides/acid, etc.).  
      It is also noted that wire-wrapped (conventional) (Smith U.S. Pat. Nos. 3,785,409; 3,908,256; 3,958,634 etc.) well screens are used in the same applications as noted previously. Resistance welding longitudinal ribs to the helically spaced wrap wires constructs these well screens. As previously noted each weld region is susceptible to stress crack corrosion at each juncture due to being heat affected. The control of filter opening (width/pore space) is also compromised at each juncture due to the heat of the welding process combined with the tensile (stretching) conditions placed on the wire during the process. Resistance welded (wire-wrapped) screens are also attached to a base pipe which is perforated or slotted. Connection can either be welded or mechanically attached.  
     BRIEF SUMMARY OF THE INVENTION  
      A sand screen assembly for separating particulate material from a subsurface fluid/gas formation uses a well screen having a seamless sintered woven wire element. In one embodiment the element has a seamless sintered woven wire body mounted over a mandrel containing apertures. The seamless sintered woven wire element is placed in a downhole environment in the subsurface gas/fluid formation. Then particulate matter is filtered from the subsurface gas/fluid formation through the seamless sintered woven wire element.  
      By application of seamless sintered (inter-atomic diffusion) well screen, as opposed to porous powdered sintered or sintered seam welded laminate screen, the principle object of the disclosed embodiments is to exclude the inflow of sand fines in both open hole and cased hole well completions in a more reliable manner.  
      A related object of the disclosed embodiments is to provide a well screen that offers maximum corrosion resistance for installation in subsurface locations. By way of example, the seamless sintered woven wire body may be electropolished by known electropolishing techniques prior to use. Another object is to provide integral structure through diffusion bonding that ensures accurate pore space openings to coincide with well design parameters. Another object is to circumvent welding at any juncture point. Ductility (malleability) of the metal seamless sintered woven wire body is another improvement over prior art with respect to delamination of the diffusion bonded surfaces which occurs in the prior art devices during expansion and bending of the well screen. Another object is to maintain proportionality between the pore space opening size and changes in the amount or quanta of flexing (bending and/or expansion) of the seamless sintered woven wire body by precision winding to accommodate intentional and/or unintentional changes in form and/or shape which occur downhole. By way of example a fifty percent (50%) expansion of the seamless sintered woven wire body would result in a likewise pore space expansion. All metal to metal crossing points are diffusion bonded without welding in order to attain maximum efficiency in hostile downhole conditions. Due to the absence of seam welding, greater inlet (flow) area is achieved by greater surface filtration exposure.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic elevational view of one embodiment of an assembly with a seamless sintered woven wire body well screen in a subsurface environment.  
       FIG. 2  is an elevational view of one embodiment of a seamless sintered woven wire element.  
       FIG. 3  is an elevational view of another embodiment of a seamless sintered woven wire element.  
       FIG. 4  is a close up view of a weave or windings employed in the seamless sintered woven wire element.  
       FIG. 5  is a view of the device shown in  FIG. 4  in an expanded mode.  
       FIG. 6  is a perspective view of one embodiment of a seamless sintered woven wire body.  
       FIG. 7  is a simplified schematic view of offset windings. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIG. 1  the embodiment disclosed represents a well  10  with surface assembly  11  mounted above ground (or ocean/sea/water body bottom) level  12 , an upper tubing string  14  extending subsurface  16 , casing  18 , a lower production tubing string  20  (either vertical, horizontal or directional) extending into a gas/fluid formation  22  which may contain hydrocarbons, and one or more well screens  30  included in the lower production tubing string  20 .  
      Referring to  FIGS. 2-3  the well screens  30  employ a seamless sintered woven wire element  32  which is preferably mounted on a mandrel  34  in contrast to prior art seam-welded sintered laminate/porous well screens for use in various configurations of downhole well completions to reduce produced (inflow) of unconsolidated sand. As a result there are no “seams” or welding lines of prior art devices as wire (various nickel/chrome) alloys are woven onto a usually ceramic or dissimilar metallic mandrel in order to produce a seamless sintered woven wire body  36 . The seamless sintered woven wire body  36  is fused by sintering. The sintering process creates a diffusion (inter-atomic) bonded structure.  
      Referring to  FIG. 2 , the seamless sintered woven wire body  36  is mounted on the mandrel  34  or pipe  35  with a mechanical type of attachment (such as pinned by set screws or a heat shrink form of attachment  38 ). Referring to  FIG. 3 , the seamless sintered woven wire body  36  is mounted on the mandrel  34  or pipe  35  with a non-mechanical type of attachment (e.g via a welded joint  40 ) Referring to  FIGS. 4-5 , the weave or windings  50  define pore space openings or inlet areas  52 . The pore space openings or inlet areas  52  may be controlled by using precise winding prior to the sintering process. Such control over the pore space/inlet areas  52  surpasses sintered laminate or conventional wire wrapped designs. The winding of the wire  54  performed prior to sintering may be done in an offset (tortuous path) design  50   a  ( FIG. 7 ) resulting in an offset flow path generally represented by arrow  51 , or a more direct non-offset configuration  50   b  ( FIGS. 2-6 ) that is consistent with wire-wrapped screen designs. Offset winding  50   a  would be more consistent with component screen products (pre-pack aggregate, etc.) that require fine filtration and “Dirt holding” capacity. Non-offset windings  50   b  would be more consistent with wire-wrapped primary screen functions. Filtering characteristics can be affected by wire  54  shape, size, pitch, winding pattern, and winding angle. For example, the helically wound wire  54  in cross section could be “flat”  54   a  ( FIG. 7 ) (somewhat trapezoid shaped) or round  54   b  depending on the purpose of the application.  
      A further explanation of the conditions under which well screens are used may help to illustrate the advantages of the seamless sintered wire well screen  30 . For largely commercial/economic reasons in the completion design of certain oil/gas/water wells  10  it is imperative to install specialized filtration equipment downhole in order to restrict the inflow of unconsolidated sand. This is usually confirmed by obtaining core (sand) samples of the formation  22  as well as well test data. It is then determined whether filtration will be required downhole in order to maximize productivity of the well  10 . The production of sand entrained in or in conjunction with well fluid/gas can cause significant erosion to any equipment (surface and subsurface) in the direct flow path of the well fluid/gas, such as, for example, surface assembly  11 . This is known to occur in either a cased hole (perforated) well bore design, or open (barefoot) hole environment. Sand control equipment/treatments are commonly installed in order to prevent the occurrence of produced formation sand. In some cases, chemically bonded porous material (i.e., gravels, proppants) is used to control the inflow of sand. In other cases, either gravel or actual formation sand (open-hole) surrounds a well screening device of sorts. In some cases, a combination (pre-pack screen) of gravel and screen are used in this manner (U.S. Pat. No. 5,339,895). In all of these arrangements or systems, as previously stated, the control or separation of particulate material from subsurface formation fluid/gas is improved by using the sintered seamless woven wire well element  32 .  
      A superior filter body  36  is provided in all applications in regard to life (corrosion resistance), reliability and ductility (bending results in deformation of pore space openings) by way of maintaining the accuracy and precision of winding a continuous shaped or round wire  54  (usually stainless or nickel/chrome alloy) without welding. Diffusion bonding of all crossing sections  56  of the sintered seamless woven wire body  36  insures total integration at the inter-atomic level. High strength levels are attained without compromising accurate filtration efficiencies. An added advantage is that improvements translate directly into economic savings for the operator.  
      One example of a seamless woven wire device which could be adapted through the disclosure of this application to a seamless sintered woven wire body  36  used in a well screen  30  application is a device commercially available from Fuji America, Inc. known as FUJILOY.  
      In a preferred embodiment the seamless sintered woven wire body  36  may have one or more of the following features separately or in combination: pore space openings  52  ranging from twenty micron to 1,000 micron; making the body  36  in a tubular shape having a wall thickness  38  ( FIG. 6 ) ranging from 0.020 inches thick to 0.365 inches thick; the seamless sintered woven wire body  36  has pore space openings  52  with tolerances ranging from plus forty microns to minus forty microns; the flat shaped ribbon wire  54   a  ( FIG. 7 ) has a thickness ranging from 0.002 inches to 0.150 inches; the round shaped wire  54   b  has a diameter ranging from 0.002 inches to 0.150 inches; expanding the seamless sintered woven wire body  36  downhole while proportionately expanding the pore space openings  52  (compare and contrast  FIG. 4  to  FIG. 5 ); electropolishing the well screen  30  for corrosion resistance prior to placing it downhole; adding a drainage layer to the well screen  30 , by, for example, adjusting the weave  50  during the seamless sintered woven wire body  36  manufacturing process to create variably sized pore space openings according to separate layers  60 ,  62 ,  64  ( FIG. 7 ) within the seamless sintered woven wire body  36  (for example the weave  50  could be course next to the mandrel  34 , next the weave  50  could be finer, and on the outer weave layer  60  the weave  50  could have large openings).