[go: up one dir, main page]

EP0858549A1 - Deep well filters - Google Patents

Deep well filters

Info

Publication number
EP0858549A1
EP0858549A1 EP96935136A EP96935136A EP0858549A1 EP 0858549 A1 EP0858549 A1 EP 0858549A1 EP 96935136 A EP96935136 A EP 96935136A EP 96935136 A EP96935136 A EP 96935136A EP 0858549 A1 EP0858549 A1 EP 0858549A1
Authority
EP
European Patent Office
Prior art keywords
layers
mesh
filter
wire
same
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP96935136A
Other languages
German (de)
French (fr)
Inventor
Nigel John Brooks
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mixalloy Ltd
Original Assignee
Mixalloy Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mixalloy Ltd filed Critical Mixalloy Ltd
Publication of EP0858549A1 publication Critical patent/EP0858549A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/02—Subsoil filtering
    • E21B43/08—Screens or liners
    • E21B43/084—Screens comprising woven materials, e.g. mesh or cloth
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/11—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
    • B01D29/111—Making filtering elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/50—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition
    • B01D29/56—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition in series connection
    • B01D29/58—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition in series connection arranged concentrically or coaxially
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/10—Filter screens essentially made of metal
    • B01D39/12—Filter screens essentially made of metal of wire gauze; of knitted wire; of expanded metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2027—Metallic material
    • B01D39/2041—Metallic material the material being filamentary or fibrous
    • B01D39/2044—Metallic material the material being filamentary or fibrous sintered or bonded by inorganic agents

Definitions

  • This invention relates to deep well filters.
  • Deep well filters are used to remove sand and other granular contaminants during downhole recovery of oil and gas from onshore and offshore reserves.
  • Such filters generally form part of the overall length of the tube through which oil and gas pass from the respective reserve to the well head. They are conventionally positioned at either the tube base or at another position within the bottom third of the tube.
  • Typical filter lengths are between 1 0m and 1 00m with an average length of 30m Recent investigations have been carried out into the use of horizontal tubes which would require longer filter lengths.
  • Conventional filters such as disclosed by US-PS-5004049 include gravelpac filters in which a specially graded gravel typically of 30 to 40 mesh is used in conjunction with a wire wrapped ribbed screen to prevent formation sand from entering the well bore; wire wrapped pipe based welded screens in which a stainless steel wrapping wire is welded to each rib wire of the screen which is in turn welded to a perforated pipe; and wire wrapped rod based welded screens which are similar to pipe-based screens but without a perforated pipe.
  • the wall thickness of these known filters is typically of the order of 0.5 inches. For a given outside diameter there is a smaller inside diameter which limits the gas and oil flow rates obtainable and restricts the diameter of the tooling which can be accommodated in the tube.
  • the limited wall thickness often requires the use of some form of supporting structure whose presence also reduces the available internal space of the tube.
  • conventional filters have an open area which equates approximately to 1 0% only of the total filter area. This has the effect of increasing within the filter build-up of scale and from mud residue of the original drilling process. Both of these factors have an effect on service life.
  • the present invention sets out to provide a deep well filter which overcomes or at least alleviates these and other problems present in conventional deep well filters.
  • a deep well filter which comprises a tubular assembly of at least five superimposed roll bonded and sintered wire mesh layers, the aperture size and wire diameter of any one mesh layer being different from the aperture sizes and wire diameter(s) of its neighbouring mesh layer or layers.
  • the layers may each be produced from steel or nickel alloy.
  • the steel is preferably a stainless steel and may be, for example, a 304 or 31 6 stainless steel.
  • the aperture size and wire diameter of the inner and outer mesh layers are the same.
  • the aperture sizes and wire diameters of the mesh layers which lie next to the inner and outer mesh layers may also be the same, although different from those of the inner and outer mesh layers.
  • Seven steel mesh layers may be provided the aperture size and wire diameter of the first and seventh such layers being the same, those of the second fourth and sixth layers being the same but different from the first and seventh, and those of the third and fifth layers being different from those of the other five layers.
  • the third and fifth layers may be of the same or different aperture size and wire diameters.
  • the invention provides a method for producing a deep well filter which comprises passing at least five superimposed layers of wire mesh through the nip of a rolling mill at a rolling load sufficient to produce a relatively flat bonded panel substantially free of delaminations, passing the roll bonded panel through a furnace to promote sintering of the superimposed mesh layers, forming the panel into a tube, and welding the adjoining edges of the panel together.
  • the superimposed layers may be passed through a furnace with a reducing atmosphere before entering the nip of the rolling mill to remove any oil residue and to soften the mesh layers.
  • the steel of mesh layers is preferably a stainless steel, especially a stainless steel of 304L specification.
  • the edges of the super imposed mesh sheets are preferably spot welded together. Sintering is preferably effected within a reducing atmosphere.
  • the tubular assembly may be produced by spiral welding of continuous lengths of the steel or nickel alloy layers. After welding, the tubular assembly may be coiled.
  • the exemplified deep well filter comprises seven superimposed sheets of stainless steel or nickel alloy wire mesh.
  • the individual sheet layers are bonded together to form a panel which is free of all delaminations.
  • the abutting panel edges are spot-welded together.
  • the layers may be produced in continuous lengths which are spirally welded into tube form. The continuously formed tube may then be coiled.
  • filters in accordance with the invention are both stronger and stiffer than conventional screen filters in terms of resistance to axial compression This is important when additional force is being applied to the
  • tubular filter to overcome obstacles during downhole installation.
  • the roll panel is then passed through a furnace with a reducing
  • the panel is then formed into its required tubular shape by a bending operation and the adjoining side edges of the panel are welded to form a

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Textile Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Inorganic Chemistry (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Filtering Materials (AREA)

Abstract

A deep well filter comprises a tubular assembly of at least five superimposed roll bonded and sintered wire mesh layers, the aperture size and wire diameter of any one mesh layer being different from the aperture sizes and wire diameter(s) of its neighbouring mesh layer or layers. In a preferred arrangement, seven steel mesh layers are provided, the aperture size and wire diameter of the first and seventh such layers being the same, those of the second, fourth and sixth layers being the same but different from the first and seventh, and those of the third and fifth layers being different from those of the other five layers. The third and fifth layers may be of the same or different aperture size and wire diameters.

Description

DEEP WELL FILTERS
This invention relates to deep well filters.
Deep well filters are used to remove sand and other granular contaminants during downhole recovery of oil and gas from onshore and offshore reserves. Such filters generally form part of the overall length of the tube through which oil and gas pass from the respective reserve to the well head. They are conventionally positioned at either the tube base or at another position within the bottom third of the tube. Typical filter lengths are between 1 0m and 1 00m with an average length of 30m Recent investigations have been carried out into the use of horizontal tubes which would require longer filter lengths.
Conventional filters such as disclosed by US-PS-5004049 include gravelpac filters in which a specially graded gravel typically of 30 to 40 mesh is used in conjunction with a wire wrapped ribbed screen to prevent formation sand from entering the well bore; wire wrapped pipe based welded screens in which a stainless steel wrapping wire is welded to each rib wire of the screen which is in turn welded to a perforated pipe; and wire wrapped rod based welded screens which are similar to pipe-based screens but without a perforated pipe.
The wall thickness of these known filters is typically of the order of 0.5 inches. For a given outside diameter there is a smaller inside diameter which limits the gas and oil flow rates obtainable and restricts the diameter of the tooling which can be accommodated in the tube. The limited wall thickness often requires the use of some form of supporting structure whose presence also reduces the available internal space of the tube. Also conventional filters have an open area which equates approximately to 1 0% only of the total filter area. This has the effect of increasing within the filter build-up of scale and from mud residue of the original drilling process. Both of these factors have an effect on service life.
The present invention sets out to provide a deep well filter which overcomes or at least alleviates these and other problems present in conventional deep well filters.
According to the present invention in one aspect there is provided a deep well filter which comprises a tubular assembly of at least five superimposed roll bonded and sintered wire mesh layers, the aperture size and wire diameter of any one mesh layer being different from the aperture sizes and wire diameter(s) of its neighbouring mesh layer or layers.
The layers may each be produced from steel or nickel alloy. The steel is preferably a stainless steel and may be, for example, a 304 or 31 6 stainless steel.
In one arrangement the aperture size and wire diameter of the inner and outer mesh layers are the same. The aperture sizes and wire diameters of the mesh layers which lie next to the inner and outer mesh layers may also be the same, although different from those of the inner and outer mesh layers.
Seven steel mesh layers may be provided the aperture size and wire diameter of the first and seventh such layers being the same, those of the second fourth and sixth layers being the same but different from the first and seventh, and those of the third and fifth layers being different from those of the other five layers. The third and fifth layers may be of the same or different aperture size and wire diameters.
In another aspect the invention provides a method for producing a deep well filter which comprises passing at least five superimposed layers of wire mesh through the nip of a rolling mill at a rolling load sufficient to produce a relatively flat bonded panel substantially free of delaminations, passing the roll bonded panel through a furnace to promote sintering of the superimposed mesh layers, forming the panel into a tube, and welding the adjoining edges of the panel together.
The superimposed layers may be passed through a furnace with a reducing atmosphere before entering the nip of the rolling mill to remove any oil residue and to soften the mesh layers. The steel of mesh layers is preferably a stainless steel, especially a stainless steel of 304L specification.
Before rolling, the edges of the super imposed mesh sheets are preferably spot welded together. Sintering is preferably effected within a reducing atmosphere.
The tubular assembly may be produced by spiral welding of continuous lengths of the steel or nickel alloy layers. After welding, the tubular assembly may be coiled.
The invention will now be described with reference to the following example of a deep well filter in accordance with the invention.
The exemplified deep well filter comprises seven superimposed sheets of stainless steel or nickel alloy wire mesh. The individual sheet layers are bonded together to form a panel which is free of all delaminations. The abutting panel edges are spot-welded together. Alternatively, the layers may be produced in continuous lengths which are spirally welded into tube form. The continuously formed tube may then be coiled.
Individual tubes are typically of 5 feet in length, these tubes being circumferentially welded together as required to produce longer filter lengths. The aperture size and wire diameter of each of the bonded sheets are different from its neighbouring sheet or sheets. A typical arrangement of steel mesh sheets is:-
Layer No. Layer Code Aperture (mm) Wire Diameter (mm)
1 A 5.00 2.00
2 B 1 .49 0.63
3 C 0.1 6 0.10
4 B 1 .49 0.63
5 D 0.26 0.1 6
6 B 1 .49 0.63
7 A 5.00 2.00
The outside diameters of filter tubes in accordance with the invention
are typically 1 77.8mm and 82.5mm.
The arrangement of steel mesh sheets is effected to increase
significantly the open area of the filter. Typically the open area of a tubular
filter in accordance with the invention is of the order of 45%. This
compares with an open area of 1 0% for conventional screen filters. The increased open area has the effect of reducing scale build-up and build-up
from mud residue from the original drilling process leading to longer service
life. Also, filters in accordance with the invention are both stronger and stiffer than conventional screen filters in terms of resistance to axial compression This is important when additional force is being applied to the
tubular filter to overcome obstacles during downhole installation.
To produce a deep well filter in accordance with the invention,
appropriate sheets of steel mesh conveniently to a 304L stainless steel
specification are initially passed through a furnace with a reducing
atmosphere to remove any oil residue and to soften the mesh sheets. The
sheets are then assembled in the appropriate configuration and the edges of
the assembled sheets are spot-welded together The assembled sheets are
then passed through a rolling mill at a rolling load sufficient to produce a flat
bonded panel free of delaminations.
The roll panel is then passed through a furnace with a reducing
atmosphere to promote sintering of the vaπous mesh sheets.
The panel is then formed into its required tubular shape by a bending operation and the adjoining side edges of the panel are welded to form a
welded seam. Individual tubular filters may then be circumferentially welded
together to produce a deep well filter of the required length.
It will be appreciated that the foregoing is merely exemplary of deep
well filters in accordance with the invention and that various modifications
may readily be made thereto without departing from the true scope of the invention as set out in the appended claims.

Claims

1 . A deep well filter which comprises a tubular assembly of at least five
superimposed roll bonded and sintered wire mesh layers, the aperture
size and wire diameter of any one mesh layer being different from the aperture sizes and wire dιameter(s) of its neighbouring mesh layer or
layers.
2. A filter as claimed in Claim 1 wherein each layer is produced from
steel
3. A filter as claimed in Claim 2 wherein the steel is a stainless steel.
4. A filter as claimed in Claim 1 wherein each layer is produced from a
nickel alloy.
5. A filter as claimed in any one of Claims 1 to 4 wherein the aperture size and wire diameter of the inner and outer mesh layers are the
same.
6. A filter as claimed in any one of Claims 1 to 5 wherein the aperture
sizes and wire diameters of the mesh layers which lie next to the
inner and outer mesh layers are the same, although different from
those of the inner and outer mesh layers. 7. A filter as claimed in any one of Claims 1 to 6 wherein seven wire
mesh layers are provided the aperture size and wire diameter of the
first and seventh such layers being the same, those of the second
fourth and sixth layers being the same but different from the first and
seventh, and those of the third and fifth layers being different from those of the other five layers.
8. A filter as claimed in Claim 7 wherein the third and fifth layers are of
the same aperture size and wire diameters.
9. A method for producing a deep well filter which comprises passing at
least five superimposed layers of wire mesh through the nip of a
rolling mill at a rolling load sufficient to produce a relatively flat
bonded panel substantially free of delaminations, passing the roll
bonded panel through a furnace to promote sintering of the
superimposed mesh layers, forming the panel into a tube, and welding
the adjoining edges of the panel together.
1 0. A method as claimed in Claim 9 wherein the superimposed layers are passed through a furnace with a reducing atmosphere before entering
the nip of the rolling mill to remove any oil residue and to soften the
mesh layers.
1 1 A method as claimed in Claim 1 0 wherein before rolling, the edges of the superimposed wire mesh sheets are spot welded together.
2. A method as claimed in any one of Claims 9 to 1 1 wherein sintering
is effected within a reducing atmosphere.
3. A method as claimed in any one of Claims 9 to 1 2 wherein the tubular
assembly is produced by spiral welding of continuous lengths of the
steel or nickel alloy layers.
4. A method as claimed in Claim 1 3 wherein after welding, the tubular
assembly is coiled.
EP96935136A 1995-11-04 1996-10-31 Deep well filters Withdrawn EP0858549A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9522662 1995-11-04
GB9522662A GB2306894B (en) 1995-11-04 1995-11-04 Deep well filters
PCT/GB1996/002665 WO1997017525A1 (en) 1995-11-04 1996-10-31 Deep well filters

Publications (1)

Publication Number Publication Date
EP0858549A1 true EP0858549A1 (en) 1998-08-19

Family

ID=10783425

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96935136A Withdrawn EP0858549A1 (en) 1995-11-04 1996-10-31 Deep well filters

Country Status (4)

Country Link
EP (1) EP0858549A1 (en)
AU (1) AU7321496A (en)
GB (1) GB2306894B (en)
WO (1) WO1997017525A1 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6415509B1 (en) * 2000-05-18 2002-07-09 Halliburton Energy Services, Inc. Methods of fabricating a thin-wall expandable well screen assembly
US6612481B2 (en) * 2001-07-30 2003-09-02 Weatherford/Lamb, Inc. Wellscreen
JP7181624B2 (en) * 2020-04-07 2022-12-01 富士フィルター工業株式会社 Filter element and method for manufacturing filter element
CN114460115A (en) * 2021-07-26 2022-05-10 中海油能源发展股份有限公司 Indoor scale sample treatment device and treatment method thereof

Family Cites Families (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB324924A (en) * 1928-08-01 1930-02-03 Joseph Allen Pickard Improvements in or relating to filters
GB416097A (en) * 1933-03-15 1934-09-13 Auto Klean Strainers Ltd Improvements in or relating to filtering or straining apparatus
GB423088A (en) * 1934-08-24 1935-01-24 Western States Machine Co Improvements relating to filter sieves for use in filtration of liquid bodies carrying suspended solid material
US2388640A (en) * 1943-12-17 1945-11-06 Edward J Moore Well point
GB926911A (en) * 1958-07-08 1963-05-22 Sintered Products Ltd Improvements in or relating to porous metallic material
CH462783A (en) * 1968-05-16 1968-09-30 Bopp & Co G Filter bodies made of metal fibers
US3780872A (en) * 1968-05-27 1973-12-25 Pall Corp Filters comprising anisometric compressed and bonded multilayer knitted wire mesh composites
GB1271867A (en) * 1968-10-04 1972-04-26 Amf Inc Filter element
GB1285574A (en) * 1969-04-17 1972-08-16 Atomic Energy Authority Uk Improvements in or relating to filters
BE792211A (en) * 1971-12-03 1973-06-01 Rech Des Etats De Surface Cent FILTER ELEMENT
NL156324B (en) * 1974-04-24 1978-04-17 Neratoom COLD CATCHER AND FILTER DEVICE FOR USE IN SUCH DEVICE.
DE2541383C3 (en) * 1975-09-17 1978-05-24 Haver & Boecker, 4740 Oelde Process for the production of multi-layer filter hollow bodies for gaseous or liquid media and then produced filter hollow bodies
JPS62156493A (en) * 1985-12-27 1987-07-11 永岡金網株式会社 Double cylinder screen
US4696751A (en) * 1986-08-04 1987-09-29 Dresser Industries, Inc. Vibratory screening apparatus and method for removing suspended solids from liquid
US4858691A (en) * 1988-06-13 1989-08-22 Baker Hughes Incorporated Gravel packing apparatus and method
GB8827484D0 (en) * 1988-11-24 1988-12-29 Gray M Game
DE3925596A1 (en) * 1989-08-02 1991-02-07 Schwaebische Huettenwerke Gmbh METHOD FOR PRODUCING A FILTER AND FILTER THEREFORE PRODUCED
US5004049A (en) * 1990-01-25 1991-04-02 Otis Engineering Corporation Low profile dual screen prepack
DE4201741A1 (en) * 1992-01-23 1993-07-29 Dynamit Nobel Ag FILTER DEVICE FOR FILTERING A GAS FLOW
JP3396246B2 (en) * 1993-01-18 2003-04-14 株式会社ナガオカ Multilayer composite screen
US5411084A (en) * 1994-06-13 1995-05-02 Purolator Products N.A., Inc. Sand filter system for use in a well

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9717525A1 *

Also Published As

Publication number Publication date
WO1997017525A1 (en) 1997-05-15
AU7321496A (en) 1997-05-29
GB2306894B (en) 1999-06-02
GB2306894A (en) 1997-05-14
GB9522662D0 (en) 1996-01-03

Similar Documents

Publication Publication Date Title
US5899271A (en) Particle control screen assembly for a perforated pipe used in a well, a sand filter system, and methods of making the same
AU2004200262B2 (en) Well completion method and apparatus
CA2550160C (en) Multi-layer screen and downhole completion method
CN101619653B (en) Expanded non-bonded mesh well screen system and manufacture method
US5979551A (en) Well screen with floating mounting
US6612481B2 (en) Wellscreen
US6457518B1 (en) Expandable well screen
JP3426334B2 (en) Coiled well screen
EP1644610B1 (en) A well screen
US20100163481A1 (en) Drainage or Filter Layer for Well Screen Assembly with Integrated Stand-off Structure
US7077196B2 (en) Expandable downhole tubular and method of use
CA2853161C (en) Sand filter and method of manufacture
CA2459559A1 (en) An expandable metal liner for downhole components
US20150375144A1 (en) Method of assembly for sand screen
CN101532378A (en) Expandable sand control screen pipe
US20070114171A1 (en) Composite filtering mesh, a sand control sleeve and a sand control screen pipe with the composite filtering mesh
AU679081B2 (en) Sand screen structure
CN206071549U (en) Wriggling self-cleaning screen pipe
WO1997017525A1 (en) Deep well filters
CN201162528Y (en) Expansible sand-prevention screening tube
CN218953287U (en) Punching joint direct welding screen pipe

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19980527

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE

17Q First examination report despatched

Effective date: 20000224

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20000706