GB2265398A - Method of sustaining fractures radiating from a well bore and compositions for use in the method - Google Patents
Method of sustaining fractures radiating from a well bore and compositions for use in the method Download PDFInfo
- Publication number
- GB2265398A GB2265398A GB9206780A GB9206780A GB2265398A GB 2265398 A GB2265398 A GB 2265398A GB 9206780 A GB9206780 A GB 9206780A GB 9206780 A GB9206780 A GB 9206780A GB 2265398 A GB2265398 A GB 2265398A
- Authority
- GB
- United Kingdom
- Prior art keywords
- grains
- gell
- coating
- resin
- proppant
- 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.)
- Granted
Links
- 239000000203 mixture Substances 0.000 title claims description 23
- 238000000034 method Methods 0.000 title claims description 14
- 229920005989 resin Polymers 0.000 claims description 26
- 239000011347 resin Substances 0.000 claims description 26
- 238000000576 coating method Methods 0.000 claims description 25
- 239000011248 coating agent Substances 0.000 claims description 24
- 230000015556 catabolic process Effects 0.000 claims description 13
- 239000011253 protective coating Substances 0.000 claims description 11
- 230000001427 coherent effect Effects 0.000 claims description 10
- 239000011342 resin composition Substances 0.000 claims description 9
- JRKICGRDRMAZLK-UHFFFAOYSA-L persulfate group Chemical group S(=O)(=O)([O-])OOS(=O)(=O)[O-] JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 5
- 239000011707 mineral Substances 0.000 claims description 5
- -1 polyethylene Polymers 0.000 claims description 4
- 239000004698 Polyethylene Substances 0.000 claims description 2
- 239000004743 Polypropylene Substances 0.000 claims description 2
- 229920001328 Polyvinylidene chloride Polymers 0.000 claims description 2
- 229910052783 alkali metal Inorganic materials 0.000 claims description 2
- 150000001340 alkali metals Chemical class 0.000 claims description 2
- 229910000323 aluminium silicate Inorganic materials 0.000 claims description 2
- 239000005011 phenolic resin Substances 0.000 claims description 2
- 229920001568 phenolic resin Polymers 0.000 claims description 2
- 229920000058 polyacrylate Polymers 0.000 claims description 2
- 229920000573 polyethylene Polymers 0.000 claims description 2
- 229920001155 polypropylene Polymers 0.000 claims description 2
- 229920002689 polyvinyl acetate Polymers 0.000 claims description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 2
- 235000019422 polyvinyl alcohol Nutrition 0.000 claims description 2
- 239000005033 polyvinylidene chloride Substances 0.000 claims description 2
- 239000004576 sand Substances 0.000 claims description 2
- 150000004760 silicates Chemical class 0.000 claims description 2
- 239000000377 silicon dioxide Substances 0.000 claims description 2
- 229920003002 synthetic resin Polymers 0.000 claims description 2
- 239000000057 synthetic resin Substances 0.000 claims description 2
- 239000001993 wax Substances 0.000 claims description 2
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims 1
- 238000004090 dissolution Methods 0.000 claims 1
- 239000008199 coating composition Substances 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000004160 Ammonium persulphate Substances 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 1
- 235000019395 ammonium persulphate Nutrition 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L sodium sulphate Substances [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002459 sustained effect Effects 0.000 description 1
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
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
-
- 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
- E21B43/025—Consolidation of loose sand or the like round the wells without excessively decreasing the permeability thereof
Landscapes
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- Physics & Mathematics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
- Soil Conditioners And Soil-Stabilizing Materials (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
- Glanulating (AREA)
Description
2265398 1 Title: Method of sustaining fractures radiating from a well bore
and compositions for use in the method
Description of Invention
The present invention relates to a method of and means for sustaining fractures radiating from a well bore in geological strata. In order to stimulate production of oil and gas from subterranean wells, it has become standard practice to fracture the oil or gas bearing strata hydraulically so that fractures radiate from the well bore. The fractures provide channels for the flow of oil and/or gas to the well bore and enhance the rate of production from the well. The pressures prevailing in the fractured strata will tend to close the fractures, unless they are sustained by introducing material into the fractures.
It is known to sustain fractures radiating from a well bore by introducing resin-coated proppant grains into the fractures. The grains are suspended in a gell for transfer down the well bore and into the fractures. Breakdown of the gell occurs in the fractures, producing a liquid which can flow away from the grains and leaving the grains deposited in the fractures. The conditions of temperature and pressure to which the grains are subjected in the fractures results in bonding of the grains into a coherent mass by means of the resin.
In order to promote breakdown of the gell within the fractures, there is incorporated in the gell a source of free-radicals or other suitable agent. A persulphate is a suitable breaker for the gell. At a temperature in the range 120 to 200'F, a persulphate breaker produces free radicals. However, these free radicals are reactive towards the resin coating of the proppant grains so that the efficiency of the breaker for the purpose of causing the breakdowa-of the gell is impaired. To mitigate this problem, it is knovn to incorporate a relatively high proportion of the breaker in the gell but this leads to'risk of the gell breakdown occurring before the gell has reached the required position Jn the fractures.
_.11 2 Premature breakdown of the gell can, for example, lead to the formation of a coherent body of resin-bonded grains in the well bore.
According to a first aspect of the present invention, there is provided a method of sustaining fractures radiating from a well bore in geological strata wherein a resin composition is applied to relatively inert grains and a protective coating is applied to the grains over the resin composition, the coated grains are suspended in a gell containing a breaker for the gell, the suspended grains are introduced down the bore into said fractures, when in the fractures, the gell breaks down under the action of the breaker, the protective coating breaks down and the resin composition binds the grains into a coherent, porous mass.
According to a second aspect of the invention, there is provided a composition comprising proppant grains suspended in a gell wherein the gell includes a break-er for the gell, wherein the grains comprise cores, an intermediate layer on the cores and a coating on the intermediate layer, wherein the intermediate layer comprises a resin and wherein the coating is less reactive with respect to the breaker than is said layer.
According to a third aspect of the invention, there are provided grains suitable for use as the proppant grains of a composition according to the second aspect of the invention, which grains comprise cores, an intermediate layer on the cores and a coating on the intermediate layer, wherein the intermediate layer comprises a resin and wherein the coating is less reactive with respect to the breaker than is said layer.
Naturally-occurring and synthetic mineral grains are suitable for use as the cores of the proppant. The proppant cores may be silica sand or synthetic alumino silicates.
The resin composition applied to the cores of the proppant is selected for its ability to cure, when subjected to elevated temperature and to pressure in the fractures radiating from a well bore. Suitable phenolic resins are available commercially. The resin may be applied as an aqueous dispersion and then dried under turbulent conditions, so that the grains do not become bound into a 9 1 1 3 coherent mass. Alternatively the resin may be applied by a solvent, or by direct coating of the cores with the resin in a melted condition.
The coating applied to the proppant grains over the resin is required to protect the resin against reaction with the breaker or with free radicals or other products derived from the breaker and is therefor required to be less reactive towards the breaker or towards free-radicals derived from the breaker than is the resin layer. The composition of the coating may be such that the coating will break down under the action of heat and pressure and permit bonding of the proppant grains into a coherent mass by curing of the resin. Composition comprising natural and/or synthetic waxes may be used to form the coating. Naturally-occurring and/or synthetic resins may comprise or be incorporated in the coating composition.
Examples of coatings which rupture under pressure, to permit bonding of the proppant grains by curing of the resin, are polyethylene, polypropylene, and polyvinylidene chloride.
In a case where the gell is aqueous, the coating composition may incorporate water-soluble components, for example polyacrylates, polyvinyl alcohols and polyvinyl acetates. Silicates of alkali metals may also be used in the coating composition.
The gell may be an aqueous gell and may comprise naturally-occurring gums and modified gums. The gell further comprises a breaker suitable for promoting break-down of the gell under the conditions to which the gell is subjected in the fractures radiating from the well bore. A source of free-radicals, for example a persulphate, e.g. sodium or ammonium persulphate, is a suitable breaker for use with a gell comprising an aqueous dispersion of gums.
The coated proppant grains may be prepared, transported and stored separately from the gell. Prior to use, the proppant grains are dispersed in the gell and the resulting dispersion is then pumped down a wen bore and into fractures radiating from the bore. The gell. containing coated proppant grains as herein described may be preceded by gell containing uncoated proppant grains 4 which will be carried into parts of the fractures remote from the well bore. The gell containing coated proppant grains will occupy at least those parts of the fractures adjacent to the well bore.
In the fractures, the gell is subjected to pressure and to an elevated temperature. The temperature may be within the range 120 to 2000F. At the elevated temperature, the breaker promotes breakdown of the gell to a relatively low viscosity aqueous mixture. For example, free radicals released by a persulphate at the elevated temperature will attack the carbon chain of a gum and thereby cause the breakdown of the gell. The aqueous mixture resulting from breakdown of the gell flows to the well bore and is drawn up the bore to the surface, leaving the coated grains in the fractures.
The protective coating on the proppant grains also will break down in the fractures. In a case where the coating is water-soluble, the coating may, at least in part, be carried away from the proppant grains by the aqueous mixture which results from break-down of the gell. The effect of the temperature and pressure to which the coated grains are subjected in the fractures also contributes to break-down of the protective coating over a period of time which is generally longer than that required for the breaker to act on the gell and cause break-down of the gell to a relatively low-viscosity mixture. Break-down of the protective coating is sufficient to enable the resin layer on the cores of the proppant grains to bind the grains into a coherent mass as the resin cures under the temperature and pressure to which the proppant is subjected in the fractures.
The proportion of the resin in the coated proppant grains is sufficiently high to facilitate bonding of the cores into a coherent mass but is sufficiently low to ensure that the resulting mass is permeable to gas and/or to oil. The proportions of resin and mineral will, in part, be determined in accordance with the size of the mineral grains. Typically, the mineral grains will constitute at least 95% by weight of the coated proppant grains and the resin composition will be present in the range 1. 5 to 5%, by weight, of the coated proppant grains. The weight of the protective coating will be substantially less than that of the resin layer.
We have found that, when using coated proppant grains as herein described, satisfactory breaking of the gell can be achieved by incorporating a persulphate at the rate of 0.5 to 21bs, e.g. 1 or 1.51bs, per thousand US gallons of gell (approximately 250 grams to 1000 grams, e.g. 500 or 750 grams, per 3785 litres of gell). In a comparable composition using proppant grains coated only with a resin, it has been found necessary to incorporate the persulphate at a rate of greater than 2, e.g. between 3 and 51bs per 1 thousand US gallons (greater than approximately 1000 grams, e.g. from 1500 to 2500 grams, per 3785 litres).
The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.
6
Claims (30)
1. A method of sustaining fractures radiating from a well bore in geological strata, wherein a resin composition is applied to relatively inert grains and a protective coating is applied to the grains over the resin composition, the coated grains are suspended in a gell. containing a breaker for the gell, the suspended grains are introduced down the bore into said fractures and when in the fractures the gell breaks down under the action of the breaker, the protective coating breaks down, and the resin composition binds the grains into a coherent, porous mass.
2. A method according to Claim 1 wherein said protective coating breaks down under the action of heat and pressure.
3. A method according to Claim 1 wherein the protective coating breaks down by dissolution of water-soluble components in an aqueous gell.
4.
A method according to Claim 3 wherein the breakdown of the gell provides an aqueous mixture in which the coating is, at least in part, carried away from the grains.
5. A method according to any one of the preceding claims comprising introducing a gell containing uncoated proppant grains down the bore into said fractures prior to introducing a gell containing said coated grains down the bore into said fractures.
6. A composition comprising proppant grains suspended in a gell. which includes a breaker for the gell; wherein the grains comprise cores, an intermediate layer on the cores, and a coating on the intermediate layer; the 7 intermediate layer comprising a resin and the coating being less reactive with respect to the breaker than is said layer.
7. A composition according to Claim 6 wherein said gell is an aqueous gell.
8. A composition according to Claim 7 wherein said gell comprises naturally-occurring gums and modified gums.
9. A composition according to Claim 8 wherein said breaker comprises a source of free radicals.
10. A persulphate.
composition according to Claim 9 wherein said breaker is a
11. A composition according to any one of Claims 6 to 10 wherein the proppant grains are transported and stored separately from the gell, and dispersed into the gell prior to use thereof.
12. A composition according to Claim 10 comprising 0.5 to 21bs persulphate per thousand US gallons of gell (approximately 250 grams - lkg per 3785 litres).
13. Grains suitable for use as the proppant grains of a composition according to any one of Claims 6 to 12, said grains comprising cores, an intermediate layer on the cores, and a coating on the intermediate layer, wherein the intermediate layer comprises a resin and the coating is less reactive with respect to the breaker than is said intermediate layer.
8
14. Grains according to Claim 13 wherein said cores comprise naturally occurring or synthetic mineral grains.
15. Grains according to Claim 14 wherein said cores comprise silica sand or synthetic alumino silicates.
16. Grains according to any one of Claims 13 to 15 wherein said resin comprising the intermediate layer is curable when subject to elevated temperature and pressure.
17. Grains according to Claim 16 wherein said resin is a phenolic resin.
18. Grains according to any one of Claims 13 to 17 wherein said coating is able to break down under the action of heat and pressure, to permit bonding of the proppant grains into a coherent mass by curing of the resin.
19. Grains according to Claim 18 wherein said coating comprises natural and/or synthetic waxes.
20. Grains according to Claim 18 wherein said coating comprises naturally occurring and/or synthetic resins.
21. Grains according to Claim 18 wherein said coating is rupturable under pressure, to permit bonding of the proppant grains into a coherent mass by curing of the resin.
22. Grains according to Claim 21 wherein said coating comprises polyethylene, polypropylene or polyvinylidene chloride.
9
23. Grains according to any one of Claims 13 to 17 wherein the gell is aqueous and the coating incorporates water-soluble components.
24. Grains according to Claim 23 wherein said coating incorporates polyacrylates, polyvinyl alcohols, polyvinyl acetates, or silicates of alkali metals.
25. Grains according to any one of Claims 13 to 24 wherein the cores of the proppant grains comprise at least 95% by weight of the coated proppant grains, and the resin composition is present in the range 1.5 to 5%, by weight, thereof, the weight of the protective coating being substantially less than that of the resin intermediate layer.
26. A composition according to any one of Claims 6 to 12, wherein said coated proppant grains are as claimed in any one of Claims 13 to 25.
27. A method of sustaining fractures radiating from a well bore in geological strata, substantially as hereinbefore described.
28. A composition substantially as hereinbefore described.
29. Grains substantially as hereinbefore described.
30. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9206780A GB2265398B (en) | 1992-03-27 | 1992-03-27 | Method of sustaining fractures radiating from a well bore and compositions for use in the method |
| DK93302377.2T DK0562879T3 (en) | 1992-03-27 | 1993-03-26 | Process for maintaining fractures radiating from a borehole and compositions for use in the method. |
| EP93302377A EP0562879B1 (en) | 1992-03-27 | 1993-03-26 | Method of sustaining fractures radiating from a well bore and compositions for use in the method |
| DE69310596T DE69310596T2 (en) | 1992-03-27 | 1993-03-26 | Method of obtaining radial fractures in a borehole and corresponding compositions |
| NO931126A NO301293B1 (en) | 1992-03-27 | 1993-03-26 | Method for keeping open cracks radiating from a well in a geological formation and preparation for use in the method |
| MX9301713A MX9301713A (en) | 1992-03-27 | 1993-03-26 | METHOD FOR SUSTAINING FRACTURES THAT RADIATE FROM A WELL HOLE AND COMPOSITIONS TO BE USED IN THE METHOD. |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9206780A GB2265398B (en) | 1992-03-27 | 1992-03-27 | Method of sustaining fractures radiating from a well bore and compositions for use in the method |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9206780D0 GB9206780D0 (en) | 1992-05-13 |
| GB2265398A true GB2265398A (en) | 1993-09-29 |
| GB2265398B GB2265398B (en) | 1995-10-25 |
Family
ID=10713009
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9206780A Expired - Fee Related GB2265398B (en) | 1992-03-27 | 1992-03-27 | Method of sustaining fractures radiating from a well bore and compositions for use in the method |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0562879B1 (en) |
| DE (1) | DE69310596T2 (en) |
| DK (1) | DK0562879T3 (en) |
| GB (1) | GB2265398B (en) |
| MX (1) | MX9301713A (en) |
| NO (1) | NO301293B1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060175059A1 (en) * | 2005-01-21 | 2006-08-10 | Sinclair A R | Soluble deverting agents |
| US7490667B2 (en) | 2006-10-02 | 2009-02-17 | Fairmount Minerals, Inc. | Proppants with soluble composite coatings |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4888240A (en) * | 1984-07-02 | 1989-12-19 | Graham John W | High strength particulates |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3237693A (en) * | 1963-10-28 | 1966-03-01 | Gulf Research Development Co | Fracturing method and propping agent |
| US4169818A (en) * | 1978-04-17 | 1979-10-02 | Celanese Corporation | Mixture of hydroxypropylcellulose and poly(maleic anhydride/alkyl vinyl ether) as a hydrocolloid gelling agent |
| US4439489A (en) * | 1982-02-16 | 1984-03-27 | Acme Resin Corporation | Particles covered with a cured infusible thermoset film and process for their production |
| US4694905A (en) * | 1986-05-23 | 1987-09-22 | Acme Resin Corporation | Precured coated particulate material |
-
1992
- 1992-03-27 GB GB9206780A patent/GB2265398B/en not_active Expired - Fee Related
-
1993
- 1993-03-26 DE DE69310596T patent/DE69310596T2/en not_active Expired - Fee Related
- 1993-03-26 NO NO931126A patent/NO301293B1/en unknown
- 1993-03-26 MX MX9301713A patent/MX9301713A/en unknown
- 1993-03-26 DK DK93302377.2T patent/DK0562879T3/en active
- 1993-03-26 EP EP93302377A patent/EP0562879B1/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4888240A (en) * | 1984-07-02 | 1989-12-19 | Graham John W | High strength particulates |
Also Published As
| Publication number | Publication date |
|---|---|
| DE69310596T2 (en) | 1997-09-18 |
| EP0562879A3 (en) | 1994-03-02 |
| NO931126L (en) | 1993-09-28 |
| MX9301713A (en) | 1993-12-01 |
| GB9206780D0 (en) | 1992-05-13 |
| DK0562879T3 (en) | 1997-07-14 |
| EP0562879A2 (en) | 1993-09-29 |
| NO931126D0 (en) | 1993-03-26 |
| NO301293B1 (en) | 1997-10-06 |
| GB2265398B (en) | 1995-10-25 |
| EP0562879B1 (en) | 1997-05-14 |
| DE69310596D1 (en) | 1997-06-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20000327 |