Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B47/00—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase
  • C06B47/14—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase comprising a solid component and an aqueous phase
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S102/00—Ammunition and explosives
  • Y10S102/705—Separated explosive constituents
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S149/00—Explosive and thermic compositions or charges
  • Y10S149/11—Particle size of a component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S149/00—Explosive and thermic compositions or charges
  • Y10S149/11—Particle size of a component
  • Y10S149/112—Inorganic nitrogen-oxygen salt
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S149/00—Explosive and thermic compositions or charges
  • Y10S149/11—Particle size of a component
  • Y10S149/114—Inorganic fuel

Definitions

• a low' density explosive can usually be detonated with smaller boosters and in a smaller diameter charge than a higher density explosive having the same composition.
• Slurry explosives having higher densities are particularly difficult to detonate also because of the high heat capacity of the water which is used in most instances as the base of the liquid phase.
• density control has been achieved heretofore by the incorporation of voids in the form of air, foamed ammonium nitrate, inert gaseous containing particles such as expanded perlite and other like gaseous containing materials.
• particles of organic explosives such as, for example, pelletized TNT, gun powder, carbon or light metals such as particulate aluminum have been used as sensitizers.
• slurry explosive sentially squeezed out of the explosive compositions, thus increasing the density to such a degree that the explosive cannot be readily detonated.
• the gaseous containing materials which haveheretofore been employed usually collapse under high pressures.
• explosive compositions which employ light metals as sensitizers have failed to detonate under increased pressures such as those-encountered in deep sea siesmic testing and the explosive fracturing of oil wells.
• Patent No. 2,671,400 teaches the use of air filled globules in specially shaped explosive charges to gain enhanced directional effects of 3,456,589 Patented July 22, 1969 the explosive when detonated. Duesing prefers to employ self-detonating explosives in his shaped charges such as, for example, dynamite and liquid nitroglycerin.
• the patent does not teach the use of hollow glass particles having particular characteristics which can withstand elevated pressures.
• the patent also does not teach that unique high pressure characteristics can be achieved when hollow glass particles having the unique characteristics as defined herein are used in slurry explosives to provide and maintain a predetermined density.
• the novel invention herein is not directed to using entrapped gaseous voids as a sensitizer but is directed to maintaining some reqiured critical densities of a given slurry explosive composition under elevated pressures.
• the fact that the entrapped gaseous voids also have a sensitizing effect is but one further advantage presented by the present improvement.
• the instant invention comprises an improved method of fracturing underground formations which are under elevated pressures and to improved slurry explosive compositions which retain density requirements under elevated pressures.
• the invention consists of incorporating into slurry explosive compositions, which usually depend to a certain degree upon gaseous voids, usually air, as a sensitizer, hollow glass particles in suflicient amounts so as to provide a density which allows the most effective propagation of the explosive composition under elevated pressures.
• the hollow glass particles are characterized by ranging in size from about 10 microns to 250 microns and having a sufficient wall thickness that the particles will not be crushed by the ambient pressure on said explosive prior to detonation.
• the improved slurry explosives are placed in boreholes adjacent to an underground formation or preferably are pumped into fissures in aformation, and detonated.
• the improvement of the present invention can be employed with any of the known slurry explosive compositions which depend to a certain degree on gaseous voids as a sensitizer and the components of which will not detrimentally affect the characteristics of the hollow glass particles.
• the compositions of the invention usually contain at least one inorganic oxidizing salt; a non self-detonating fuel; water and'usually also a gelling or thickening agent.
• the explosive composition of the present novel composition contains from about 10 percent to about 90 percent by weight of the total composition of the inorganic oxidizer salt; preferably ammonium nitrate and sodium nitrate are employed wherein the ammonium nitrate ranges from about 30 percent to 90 percent by weight of the total composition and the sodium nitrate ranges from about percent to 30 percent by weight of the total composition.
• Fuels which can be employed in the improved explosive composition usually consist of non-explosive carbonaceous and particulate metallic fuels.
• Non-self-detonating fuels are preferred in the instant improved composition, however, self-detonating fuels such as, for example, organic nitrate and nitro compounds, nitramines and explosive grade nitrocellulose may be employed under certain conditions to provide needed velocity, enhanced sensitivity at low temperature, and the like characteristics.
• carbonaceous non-explosive fuels include finely divided carbon, carbonaceous vegetable products such as corn starch, sugar, wood pulp; organic liquids such as hydrocarbon oils, fatty oils, vegetable oils; urea, crude oils and other liquid hydrocarbons and preferably water-soluble petrolic liquids of low volatility. Generally, up to about 20 percent of the non-explosive carbonaceous fuels are employed in the compositions and preferably from about 5 to 15 percent are employed.
• particulate metallic fuels also may be employed either alone or in admixture with other fuels.
• Metallic fuels which can be employed in the novel composition can consist of aluminum, magnesium silicon; alloys of aluminum silicon and magnesium; iron, alloys of iron, ferro-silicon, ferro phosphorous and mixtures and alloys thereof.
• Particulate metal size generally ranges from about 8 mesh to about 200 mesh and preferably from about 20 to 200 mesh. About 50 percent by weight of metallic fuels can be employed in the present novel invention, however, preferably only from 10 to 30 percent are employed.
• water-bearing compositions can be employed in the present invention. Usually up to about 25 percent of water may be used, preferably, however, only from about 5 percent to about percent of water is employed and usually at least 8 percent is employed.
• thickening agents may be employed in the present novel invention and the resultant compositions may vary from pourable solutions, slurries, and dispersions to thick moldable plastic masses. It is preferred that the explosive be maintained in such a condition so as to insure a stable mix having the various components in suspension for substantial periods of time and which are pumpable without the use of excessive pump pressures.
• Various thickening and gelling agents may be employed. Those commonly used include natural gums such as gum arabic, guar, karaya, synthetic polymers including polyacrylamides and polyvinyl alcohols and the like. Generally from about 0.1 to 10 percent and preferably from about 0.5 to 5 percent by weight of a thickening agent based on the total weight of composition are employed depending on the particular agent chosen and the desired consistency of the explosive.
• slurry explosives as defined herein must be maintained at a density of from about 1.0 to about 1.5 g./cc. in order to insure substantially complete propagation upon detonation.
• the density is usually controlled by the amount of entrapped gaseous voids, usually air, in the explosive mix; heretofore, air has generally been provided in small bubbles in the mixes by agitation of the explosive during the preparation thereof.
• the novel improvement of the present invention consists in admixing into any of a variety of slurry explosive compositions hollow glass particles within well defined proportions and having well defined physical characteristics.
• the density of slurry explosive compositions is important in that when the density is increased above a critical amount, improper propagation of the explosive composition will result. Therefore, the hollow glass particles are added to the particular slurry composition in amounts which will provide a composition having a density which for that particular composition will insure the most efficient detonation under elevated pressures. Generally from about 1 percent to 20 percent by weight of hollow glass particles are used and one, preferably, should not use more hollow glass particles than necessary to provide the explosive composition with a desired density. The most favorable amount of hollow glass particles to be employed is dependent upon the particular slurry employed since the desired operating density varies somewhat accordingly with the composition of the explosive.
• the 'wall thickness of the hollow glass particles varies with the pressures under which the explosive compositions are to be employed. A greater wall thickness will be required for high pressures. Hollow glass particles having a particle density of from about 0.2 to 0.9 are usually adequate for use at pressures up to 1000 p.s.i. It is necessary to provide glass particles having sufficient wall thickness so as to not be crushed under the force of the elevated pressures, otherwise the explosive composition will become more dense and consequently less sensitive as the air is squeezed from the explosive.
• the hollow glass particles also provide a sensitizing effect upon detonation of the explosive because of the presence of the encapsulated gas in the explosive. It has been found that the size of the gaseous voids within the range disclosed herein does not affect the sensitivity of the explosive composition to any appreciable degree.
• the present novel invention is especially adapted for treating underground earth formations to provide a fracturing thereof and particularly at depths where elevated pressures are encountered.
• it finds special utility in the treatment of oil and gas wells to fracture and open up passageways away from the borehole in order to increase the production of oil or gas from the well.
• Slurry explosives are compressed under the elevated pressures which are encountered at the depths of most oil wells, especially those having a high hydrostatic head. For example, at 1000 feet the pressure under a hydrostatic head is equal to about 500 p.s.i.
• slurry type explosives which require a certain minimum density for complete propagation could not be fired at this pressure, even when extremely powerful boosters are employed, and even slurry explosives containing self-deton'ating fuels may be ineffective at such pressures.
• the present novel method consists in placing a slurry explosive composition containing hollow glass particles in an amount and having characteristics as defined hereinbefore, into the underground earth formation either in preformed charges or preferably pumping the slurry explosive into the bore and into the fissures of the geological formation surrounding theborehole.
• a small amount of explosive usually is left in the borehole to aid ininitiating the explosive mass.
• the borehole is usually filled with a liquid, such as, for example, water or cement and the explosive is detonated with a suitable detonation charge. Because of the presence of the hollow'glass particles in the explosive composition, the explosive can be detonated with substantially complete propagation with standard detonation devices.
• the pressures which are encountered in underground earth formations as, for example, oil wells may range anywhere from psi. to 20,000 p.s.i. or more dependmg on the depth of the formation.
• the present novel invention is suitable for fracturing underground'earth formations in a variety of areas, including, for example, oil and gas *wells, brine wells, taconite and other like formations.
• An especially adaptable explosive composition for the present'novel improvement and which can be employed as the improved method of fracturing underground earth formations is that disclosed in US. Patent No. 3,307,986 and comprises a mixture of alkali metal nitrate to about 60 percent," ammonium nitrate from about to about 85 percent particulate aluminum from about 5 to about 40 percent, water from about 5 to percent, gelling agent from about 0.2 to about 1.5 percent.
• Thisimprovement comprises adding to the explosive composition hollow glass particles having a particle density ranging from'0.1 g./cc. to 0.9 g./cc. and ranging in size from about 10 microns to about 250 microns and comprising from about 1.0 percent to about.
• the composition comprises sodium nitrate from about 5 to about 40 percent; ammonium nitrate from about 15 to about 80 percent; particulate aluminum from about 10 to about 30 percent; water from about 6 to about 16 percent, liquid organic water-miscible liquid extender, from about 2 to about 16 percent; a water swellable gum'and crosslinking agent from about 0.5 to about 1.5 percent, and hollow glass particles having a particle density of from about 0.2 g./cc. to 0.9 g./cc. and ranging in size from about 10 microns to 250 microns and provided in sufiicient quantity so as to maintainthe density of the composition within the range of from about 1.1 g./cc. to about 1.4 g./cc. which usually requires from 2.0 to 10 percent by Weight of hollow'glass particles.
• the aluminum metal employed has a particle size and guage distribution as set forth in Table I.
• the metal ranges from about 0.025 to about 5 mils in guage. 1
• aluminum is meant to include aluminum and aluminum alloys containing at least about 60 percent by weight of aluminum.
• Liquid organicfiuid extenders which can be employed consist of monohydroxy alkanols of low molecular weight
• ethylene glycol, propylene glycol, glycerol, formamide, and other like fluid extenders which preferably have a carbon-oxygen ratio such that there is no detrimental competition of the carbon with the metal for available oxygen in the system.
• methanol, ethylene glycol, glyc- particularly suitable agents include guar gums, karaya gums, and mixtures thereof and any of a variety of conventional crosslinking agents can be employed.
• the desired density can now be achieved and maintained while the explosive is under elevated pressures by the addition of hollow glass particles having the characteristics and in amounts as defined herein'before.
• Example 1 A slurry explosive composition was prepared, the composition of which was as follows:
• the explosive composition was prepared by first dispersing the gelling agent into propylene glycol. Water and formamide were mixed and added to the propylene glycol and gelling agent mix. Next the sodium nitrate and ammonium nitrate were added'and mixed. The hollow glass particles were then added to the composition and the entire mixture was warmed to room temperature and the particulate aluminum was added and mixed. Finally, the crosslinking agent was added and the explosive composition was allowed to gell. The hollow glass particles ranged in size from about 10 to 250 microns and had a particle density of about 0.26 g./cc. The final explosive mix had a density of approximately 1.1 g./ cc. The explosive composition was then tested for detonation characteristics under elevated pressures.
• the explosive was placed in a 2 inch standard steel pipe having a cover, a welded cap and a pressure tubing connection.
• the cover was sealed with a standard neoprene O ring.
• a 37 gram high explosive primer was also placed in the bottom of the pipe.
• the explosive composition was separated from the cover by a plastic disc to prevent oil from mixing with the explosive prior to detonation.
• the pipe was buried in the ground with a small shaped charge next to the booster.
• the pressure in the pipe was raised to 560 p.s.i., the shaped charge was detonated.
• Example 2 7 An explosive having the following compositions was prepared in a manner similar to that described for preparing the explosive in Example 1.
• a part of the explosive composition described herein without beads was whipped to provide air voids.
• the mix failed to propagate when pressurized to 100 p.s.i.
• a method for treating underground earth formations to provide fracturing thereof which comprises:
• said slurry explosive consists of a water resistant metalized, flowable explosive composition which comprises, on a weight basis to about 60 percent alkali metal nitrate, from about 10 to about 85 percent ammonium nitrate, from about to about 25 percent water, from about 0.2 to about 1.5 percent of a member selected from the group consisting of water swellable gelling and thickening agents, and from about 5 to about 40 percent particulate aluminum, said aluminum ranging in size from about 4 to about 150 mesh U.S.
• hollow glass particles ranging in size from about 10 microns to about 250 microns and having a particle density which ranges from about 0.1 g./cc. to 0.9 g./cc., said particles being present in an amount sufiicient to provide a density of the explosive composition which will insure a substantially complete propagation under elevated pressures.
• said slurry composition comprises on a weight basis to about 60 percent alkali metal nitrate; from about 10 to about percent ammonium nitrate; from about 5 to about 25 percent water; from about 0.2 to about 1.5 percent of a member selected from the group consisting of water swellable gelling and thickening agents, and from about 5 to about 40 percent particulate aluminum, said aluminum ranging in size from about 4 to about 150 mesh US.
• the improved slurry explosive composition as defined in claim 12 wherein said explosive comprises on a weight basis from about to about 40 percent sodium nitrate; from about 15 to about 80 percent ammonium nitrate; from about 6 to about 16 percent water; from about 2 to about 16 percent of a liquid, organic watermiscible liquid extender; from about 0.5 to about 1.5 percent of a water-swellable, hydrophobic, cross-linkable gum and crosslinking agent therefor; and from about 10 to about percent particulate aluminum, said aluminum having (1) a particle size of from about 30 to about 100 mesh wherein the particle size distribution ranges from about to about percent of about 30 to 50 mesh, from about 25 to about 35 percent of from about 50 to about mesh, balance from about 100 to about mesh and (2) a gauge of from about 1 to about 15 mils and distribution such that about 6 to about 9 percent of the particles have a maximum thickness of about 1 mil, from about 14 to about 17 percent range from about 1 to about 5 mils, from about 73 to about 77 percent range from about 5 to about 10

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Cited By (27)

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Citations (8)

• 1967
  • 1967-03-20 US US624185A patent/US3456589A/en not_active Expired - Lifetime
• 1968
  • 1968-03-14 NL NL6803624A patent/NL6803624A/xx unknown
  • 1968-03-15 GB GB02713/68A patent/GB1206243A/en not_active Expired
  • 1968-03-19 FR FR1562346D patent/FR1562346A/fr not_active Expired
  • 1968-03-19 NO NO1051/68A patent/NO119829B/no unknown
  • 1968-03-20 DE DE19681771007 patent/DE1771007A1/de active Pending

Patent Citations (8)

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