Wells – Expansible anchor or casing – Expansible casing
Reexamination Certificate
2002-10-25
2004-08-03
Tsay, Frank (Department: 3672)
Wells
Expansible anchor or casing
Expansible casing
C166S227000, C166S051000
Reexamination Certificate
active
06769484
ABSTRACT:
FIELD OF THE INVENTION
The present invention is in the field of apparatuses and processes particularly adapted for use in an earth fluid well. More specifically, the present invention relates to an apparatus at the end of a well conduit for separating solids from the earth fluids flowing into the conduit, the apparatus comprises a porous mass of adhered filter material.
BACKGROUND OF THE INVENTION
Hydrocarbon producing wells typically are drilled many thousands of feet into the earth in order to reach an oil or natural gas bearing strata. These strata are often structurally weak or fragile geological formations comprising particulate matter, such as sand, gravel and similar materials. Consequently, the downhole formation of the well bore can be subject to degradation and the accumulation of particulates and the migration of these particulates along with the earth fluids into the well.
It is known in the field to use well screens as filters in the downhole bore of a hydrocarbon producing well to prevent the migration of particulates, such as sand, gravel and the like, into the well conduit along with the production flow. Additionally, because the downhole bore can have irregular surfaces, the field has been motivated to develop deformable well screens that are expandable downhole to at least partially set against the surrounding formation and line the borehole. For examples, see U.S. Pat. Nos. 5,901,789 and 6,012,522 to Donnelly et al. and U.S. Pat. No. 6,457,518 to Constano-Mears et al.
Further, at the points of irregularity in the borehole where the rigid, external surface of Donnelly-type well screens does not sufficiently contact the surrounding formation, undesirable gaps and channels can be formed. To reduce or eliminate the effect such formation irregularities, the field has been motivated to develop means to fill and/or support gap forming irregularities. For example, Donnelly et al. disclose the use of resin-coated gravel as a porous fill material which is separately installed in situ as a means for filling gaps between the well bore formation and the well screen.
Because of the benefit of having a downhole well screen installed in close contact with wall of the well bore formation, it would be useful in the field to have alternative downhole expandible well screens that serve not only as a production flow filters, but also as a well bore liners that require less intervention for filling gaps between the well bore formation and the well screen.
SUMMARY OF THE INVENTION
The present invention is a downhole expandable bore liner and well screen filter assembly, particularly for use in a hydrocarbon producing well bore. The liner/filter assembly comprises a perforated tubular base-pipe overlain with a filter-cover. A set of runners (bumpers) extends the length of the outer surface of the assembly. A constriction means holds the liner/filter assembly in a compressed configuration during insertion of the assembly down the well bore. The outside diameter of the liner/filter assembly in its compressed configuration is sufficiently less than the inside diameter of the well bore to facilitate insertion of the liner/filter assembly into its downhole position. Once positioned downhole in the well bore, the constriction means is released, and the liner/filter assembly takes its expanded or uncompressed configuration to interface with the walls of the well bore. In its uncompressed configuration, the liner/filter assembly can contact and press against the walls of the well bore, which contact serves to stabilize the assembly and to center it in the downhole well bore. Additionally, the resilient and malleable nature of the filter material of the filter-cover can engage and at least partially fill and stabilize the irregularities in the formation wall.
The tubular base-pipe is perforated to allow passage of earth liquids (“production flow”) from the well bore environment external to the base-pipe into its interior, and further passage into a conduit to which the liner/filter assembly (or string of liner filter assemblies) is attached. The tubular base-pipe has a central axis, a pipe-length, and a tube wall enclosing an interior space. The interior space is disposed to be communicable with the with the fluid space of a well conduit. The tube wall has a plurality of through perforations for passing fluids. Optionally, the tubular base-pipe may be expandable as is known in the field, to provide a tube wall having a plurality of through perforations for passing fluids. For example, see the U.S. Pat. No. 5,901,789 to Donnelly et al. for how to accomplish an expandable base-pipe in the present invention. Typically, the base-pipe will include a connecting means allowing the base-pipe to be joined in series with a well conduit or to another well screen liner/filter assembly. The bottom most liner/filter assembly in a series is plugged at its bottom end.
The filter-cover covers the outer tube-surface of the base-pipe and servers to filter the earth liquids before they pass through the perforations in the tube-wall of the base-pipe. The liner/filter assembly is inserted into the well bore with the filter-cover in a compressed configuration to reduce the overall outside diameter of the assembly to facilitate the insertion process. Once the liner/filter assembly is positioned downhole in the well bore, the filter-cover is allowed to take its normal uncompressed configuration. The filter-cover may be disposed on the outer surface of the base-pipe in any of a numbers of manners practicable in the present invention by one of ordinary skill in the art. For example, the filter cover may be drawn into position over the base-pipe in the manner of a sleeve, or may be wrapped in a helictical fashion over the length of the base-pipe.
The filter-cover is made of a compressible/self-expanding filter material and has a fully compressed-thickness, an expanded-thickness, a fully compressed outer-diameter and an expanded outer-diameter. The filter-cover is made of a filter material impervious to the fluids which it is to filter. In the present invention, the filter-cover comprises a filter material which is substantially impervious to fluids containing hydrocarbons. The filter-cover may comprise one or more layers of filter material, and the different filter material layers may have different physical and/or structural characteristics. For example, the filter-cover may comprises one or more filter materials selected from the group consisting of: a fiber matrix, an open cell foam. Additionally, the different layers of filter materials may have different physical-chemical characteristics and different porosity or filtering characteristics.
Typically, the filter material will have sufficient porosity to pass earth fluids and gas, while filtering out most particulates from the production flow. An appropriate filter material for practice in the present invention in a hydrocarbon producing well is resistant to exposure to crude oil, brine and to other fluids used in producing hydrocarbon wells. Additionally, the filter materials should be resistant to the temperatures, pressure and conditions of pH that may be experienced in hydrocarbon producing wells. The filter material is also mechanically resilient and has sufficient memory to expand to substantially its initial uncompressed condition (thickness) after being bound for a time in a compressed condition. Several polyurethane open-cell foam materials have been found to meet these requirements. It is likely that other materials, such as silicone resin based open-cell foams will also meet these filter material requirements.
A set of runners extend the length of the filter-cover and protrude radially beyond the outer surface of the filter-cover when the liner/filter assembly is in its compressed configuration. The runners are disposed at the outer cover-surface of the filter-cover in a spaced relationship to each other. The space relationship of the runners extends the pipe-length of the base-pipe, and define the overall outer diameter of the liner/filter assembly in
Pernia Sherman D.
Tsay Frank
LandOfFree
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