EP0562879B1 - 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
- EP0562879B1 EP0562879B1 EP93302377A EP93302377A EP0562879B1 EP 0562879 B1 EP0562879 B1 EP 0562879B1 EP 93302377 A EP93302377 A EP 93302377A EP 93302377 A EP93302377 A EP 93302377A EP 0562879 B1 EP0562879 B1 EP 0562879B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- gell
- grains
- coating
- breaker
- intermediate layer
- 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.)
- Expired - Lifetime
Links
- 239000000203 mixture Substances 0.000 title claims description 15
- 238000000034 method Methods 0.000 title claims description 8
- 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
- 239000011253 protective coating Substances 0.000 claims description 10
- 230000001427 coherent effect Effects 0.000 claims description 8
- 239000011342 resin composition Substances 0.000 claims description 8
- JRKICGRDRMAZLK-UHFFFAOYSA-L persulfate group Chemical group S(=O)(=O)([O-])OOS(=O)(=O)[O-] JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 claims description 7
- -1 polyethylene Polymers 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 3
- 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
- 229920000573 polyethylene Polymers 0.000 claims description 2
- 229920001155 polypropylene Polymers 0.000 claims description 2
- 239000005033 polyvinylidene chloride Substances 0.000 claims description 2
- 239000001993 wax Substances 0.000 claims description 2
- 238000004090 dissolution Methods 0.000 claims 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 14
- 230000015556 catabolic process Effects 0.000 description 14
- 239000004576 sand Substances 0.000 description 10
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 6
- 229910052500 inorganic mineral Inorganic materials 0.000 description 4
- 239000011707 mineral Substances 0.000 description 4
- 239000003921 oil Substances 0.000 description 4
- 239000008199 coating composition Substances 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 239000004312 hexamethylene tetramine Substances 0.000 description 3
- 235000010299 hexamethylene tetramine Nutrition 0.000 description 3
- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 description 3
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229920001568 phenolic resin Polymers 0.000 description 2
- 239000005011 phenolic resin Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 1
- 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
- DHKHKXVYLBGOIT-UHFFFAOYSA-N acetaldehyde Diethyl Acetal Natural products CCOC(C)OCC DHKHKXVYLBGOIT-UHFFFAOYSA-N 0.000 description 1
- 125000002777 acetyl group Chemical class [H]C([H])([H])C(*)=O 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910000323 aluminium silicate Inorganic materials 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
- 239000008187 granular material Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000002480 mineral oil Substances 0.000 description 1
- 235000010446 mineral oil Nutrition 0.000 description 1
- 229920003986 novolac Polymers 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 235000010603 pastilles Nutrition 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
- 229920002689 polyvinyl acetate Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 150000004760 silicates Chemical class 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
- 230000002459 sustained effect Effects 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 229920002554 vinyl polymer Polymers 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
Definitions
- the present invention relates to a method of and means for sustaining fractures radiating from a well bore in geological strata.
- 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.
- a persulphate is a suitable breaker for the gell.
- a persulphate breaker produces free radicals.
- 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 breakdown of the gell is impaired.
- it is known 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 in the fractures. Premature breakdown of the gell can, for example, lead to the formation of a coherent body of resin-bonded grains in the well bore.
- a proppant for hydraulic fracturing comprising a core on which there is a cured resin coating.
- An outer coating is present outside the cured coating, the outer coating being a heat-curable phenolic resin with which there is incorporated a small amount of a polyvinyl acetal and a small amount of a mineral oil.
- the curable resin of the outer coating would be reactive towards a free-radical breaker and would thus impair the efficiency of the breaker for the purpose of causing the breakdown of a gell in which the proppant is suspended.
- 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.
- a composition comprising proppant grains suspended in a gell wherein the gell includes a breaker 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.
- grains suitable for use as the proppant grains to be suspended in a gell which includes a breaker for the gell to form 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 comprises a material selected to be 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 coherent mass.
- 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.
- coatings which rupture under pressure, to permit bonding of the proppant grains by curing of the resin are polyethylene, polypropylene, and polyvinylidene chloride.
- 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 well 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 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.
- the gell In the fractures, the gell is subjected to pressure and to an elevated temperature.
- the temperature may be within the range 49-93°C (120 to 200°F).
- the breaker promotes breakdown of the gell to a relatively low viscosity aqueous mixture.
- 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.
- 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.
- 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.
- compositions can be prepared as follows:
- High quality silica sand, or synthetic proppant with particle sizes in the range 420-840 microns is heated to 160°C. 3.0% by weight based on the weight of sand or other proppant of a phenol/formaldehyde solid novolac resin in granule, pastille, flake or needle form, having a molar phenol to formaldehyde ratio of I to 0.8 in its initial kettle charge, is then charged onto the sand in a known sand mixer. The sand and resin are mixed until the resin has melted and coated the sand evenly.
- a hexamine solution (44% w/w) in water is added to the sand mixture.
- the amount of hexamine solution is such that the weight of solid hexamine added is 13% of the weight of the resin mixed with the sand.
- a second protective overcoating is then put onto the sand, which is still at an elevated temperature in the mixer.
- the overcoating compositions as appropriate may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.
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- 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)
- Soil Conditioners And Soil-Stabilizing Materials (AREA)
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
- Glanulating (AREA)
Description
- 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 49-93°C (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 breakdown of the gell is impaired. To mitigate this problem, it is known 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 in the fractures. Premature breakdown of the gell can, for example, lead to the formation of a coherent body of resin-bonded grains in the well bore.
- In US 4 888 240, Graham et al, there is disclosed a proppant for hydraulic fracturing, the proppant comprising a core on which there is a cured resin coating. An outer coating is present outside the cured coating, the outer coating being a heat-curable phenolic resin with which there is incorporated a small amount of a polyvinyl acetal and a small amount of a mineral oil. The curable resin of the outer coating would be reactive towards a free-radical breaker and would thus impair the efficiency of the breaker for the purpose of causing the breakdown of a gell in which the proppant is suspended.
- 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 breaker 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 to be suspended in a gell which includes a breaker for the gell to form 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 comprises a material selected to be 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 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 well 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 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 49-93°C (120 to 200°F). 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 1.5lbs, 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 5lbs per 1 thousand US gallons (greater than approximately 1000 grams, e.g. from 1500 to 2500 grams, per 3785 litres).
- Suitably coated proppant grains can be prepared as follows:
- High quality silica sand, or synthetic proppant with particle sizes in the range 420-840 microns (ASTM sieve no's: 20-40) is heated to 160°C. 3.0% by weight based on the weight of sand or other proppant of a phenol/formaldehyde solid novolac resin in granule, pastille, flake or needle form, having a molar phenol to formaldehyde ratio of I to 0.8 in its initial kettle charge, is then charged onto the sand in a known sand mixer. The sand and resin are mixed until the resin has melted and coated the sand evenly.
- A hexamine solution (44% w/w) in water is added to the sand mixture. The amount of hexamine solution is such that the weight of solid hexamine added is 13% of the weight of the resin mixed with the sand. When all the water has evaporated, a second protective overcoating is then put onto the sand, which is still at an elevated temperature in the mixer. There is used for the overcoating compositions, as appropriate may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.
Claims (10)
- 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.
- A method according to Claim 1 wherein said protective coating breaks down under the action of heat and pressure.
- A method according to Claim 1 wherein the protective coating breaks down by dissolution of water-soluble components in an aqueous gell.
- A method according to anyone of Claims 1-3 wherein the proppant grains are transported and stored seperately from the gell and dispersed into the gell prior to introduction of the gell down the bore.
- 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 intermediate layer comprising a resin and the coating being less reactive with respect to the breaker than is said layer.
- A composition according to Claim 5 comprising 0.5 to 2lbs persulphate per thousand US gallons of gell (approximately 250 grams - 1kg per 3785 litres).
- Grains used as the proppant grains to be suspended in a gell which includes a breaker for the gell to form a composition according to Claim 5 or Claim 6, 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 comprises a material seclected to be less reactive with respect to the breaker than is said intermediate layer.
- Grains according to Claim 7 wherein said coating comprises natural and/or synthetic waxes.
- Grains according to Claim 7 wherein said coating comprises polyethylene, polypropylene or polyvinylidene chloride.
- Grains according to any one of Claim 7 wherein the gell is aqueous and the coating incorporates water-soluble components.
Applications Claiming Priority (2)
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 |
GB9206780 | 1992-03-27 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0562879A2 EP0562879A2 (en) | 1993-09-29 |
EP0562879A3 EP0562879A3 (en) | 1994-03-02 |
EP0562879B1 true EP0562879B1 (en) | 1997-05-14 |
Family
ID=10713009
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP93302377A Expired - Lifetime EP0562879B1 (en) | 1992-03-27 | 1993-03-26 | 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 |
---|---|---|---|---|
MX2007008850A (en) * | 2005-01-21 | 2008-01-16 | Fairmount Minerals Ltd | Soluble diverting agents. |
US7490667B2 (en) | 2006-10-02 | 2009-02-17 | Fairmount Minerals, Inc. | Proppants with soluble composite coatings |
Family Cites Families (5)
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 |
US4888240A (en) * | 1984-07-02 | 1989-12-19 | Graham John W | High strength particulates |
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 EP EP93302377A patent/EP0562879B1/en not_active Expired - Lifetime
- 1993-03-26 DK DK93302377.2T patent/DK0562879T3/en active
- 1993-03-26 MX MX9301713A patent/MX9301713A/en unknown
- 1993-03-26 NO NO931126A patent/NO301293B1/en unknown
Also Published As
Publication number | Publication date |
---|---|
EP0562879A2 (en) | 1993-09-29 |
DE69310596D1 (en) | 1997-06-19 |
DE69310596T2 (en) | 1997-09-18 |
NO931126L (en) | 1993-09-28 |
MX9301713A (en) | 1993-12-01 |
GB2265398B (en) | 1995-10-25 |
DK0562879T3 (en) | 1997-07-14 |
NO301293B1 (en) | 1997-10-06 |
GB9206780D0 (en) | 1992-05-13 |
EP0562879A3 (en) | 1994-03-02 |
GB2265398A (en) | 1993-09-29 |
NO931126D0 (en) | 1993-03-26 |
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