BAKER HUGHES, A GE COMPANY,
`LLC AND BAKER HUGHES
`OILFIELD OPERATIONS LLC
`Exhibit 1137
`BAKER HUGHES, A GE COMPANY,
`LLC AND BAKER HUGHES
`OILFIELD OPERATIONS LLC v.
`PACKERS PLUS ENERGY
`SERVICES, INC.
`IPR2016-01506
`Page 1 of 5
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`Patented Sept. 14, 1954
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`2,689,009
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`UNITED STATES PATENT OFFICE
`
`2,689,009
`ACIDIZING WELLS
`
`1
`1
`
`Harold W. Braincrd, Jr., Clarence R. Fast, and
`George 0. Howard, Tulsa, Okla” assignors to
`Stanolind Oil and Gas Company, Tulsa, Okla”
`a corporation of Delaware
`No Drawing. Application April 14,1951,
`Se1ial No. 221,136
`(01. 166—25)
`
`20 glaims.
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`01
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`10
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`1
`This invention pertains to a well-treating solu-
`tion and to an improved method of treating wells '
`to increase their productivity.
`In the art of completingwells or working over
`old wells to increase the output, acid is injected
`into the producing zones to increase the perme-
`ability of the formation around the well Since
`acid reacts very rapidly with calcareous forma-
`tions,1t appears that the action of the acid is
`very close to the well. Accordingly, the effect of
`acidizing a well is generally to increase output,
`but the increase appears to be much less than
`would be possible if the acid could be made to
`react into long channels deep into the formations.
`It has been proposed that strong mineral acids
`which are used to acidize formations penetrated
`by a well be incorporated as the discontinuous
`phase in an acid-011 emulsion. By thus shielding
`the acid, it is prevented from contacting the well
`tubing and the calcareous formations as the acid
`is injected into a well CorroSion of the tubing
`is avoided, and the reaction of the acid on the
`formation is retarded. Ceitain oils are knewn to
`emulsify with acids; and, in some cases, the emul-
`sion may be produced by incorporating in the oil
`or the acid certain emulsifying agents. This pro-
`posal has not been used, since, in practice, it has
`been found that the emulsifying agents proposed
`are either too stable or too unstable. That is,
`if the emulsion is too stable, the emulsion may
`not be easily broken down in the well or in the
`formation; and, if injected into a formation, as
`by the application of a high pressure, the emul-
`sion cannot be displaced from the pores of the
`formation by the 1elatively small available natu-
`ral driving force. The formation would thus be
`plugged if such stable emulsions were forced into
`the capillaiies surrounding a well.
`If the emul—
`sion is unstable, it is of no value for the intended
`purpose.
`Ineither case, lioWever, the action of
`the acid is close to the well, and long flow chan—
`nels into the formation are not produced.
`It is an object of this invention to provide an
`improved well-treating solution.
`It is another
`object of this invention to provide a well-treating
`solution comprising an emulsion of an acid and
`an oily vehicle which can be injected into a for-
`mation at high pressure to fracture the formatiOn
`and which subsequently can be removed from the
`formation without pluggingthe pores thereof. A '
`
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`still further object of this invention is to provide
`an iinproved process for increasing the permea-
`bility of calcareous formations which produce oil
`or gas or other valuable fluids.
`This invention, in brief, comprises a well-treat-
`ing solution in which acid is emulsified in an oil
`dispersion of Batu gum and an improved process
`in which the viscous emulsion is injected into a
`formation at a pressure great enough to fracture
`the formation.
`Batu gum is a natural resin related to the
`Damar natural resins and is a secretion or exuda—
`tion of the Sho1ea tree of the East Indies. It is
`soluble in aryl or coal tar hydrocarbons and in
`hydrogenated aliphatic petroleum solvents but is
`generally only very slightly solublein crude petro-
`leum or refined paraffinic petroleum hydrocar-
`bons.
`'It is, however, compatible with and can be
`dispersed in paraffinic hydrocarbons, both crude
`and refined It is available commercially as bold
`scraped unscraped, nubs and chips, and as dust.
`The acid phase of the emulsion may be any
`acid, such as hydrochloric, nitric, or hydrofluoric,
`which reacts with the formation and produces a
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`water-soluble salt. The most important well acid
`is hydrochloric acid in the concentration range
`from about 5 to about 20° Bé The higher con-
`centrations are preferred in view of the increased
`reaction rate and the decrease in breakdown time
`for the emulsion The vehicle in which the acid
`of our treating solution is emulsified may consist
`of non-aqueous liquids, such as liquid petroleum
`hydrocarbons, e. g., crude oil, kerosene, diesel fuel,
`or other light liquid hydrocaibons of this class,
`but we prefer kerosene, since it is practically uni-
`versally available, the composition is relatively
`uniform, and it is not considered hazardous to
`handle. While any of the commercial grades of
`, Batu gum will emulsify oil and acid in accord-
`40
`ance with this invention, bold scraped and nubs
`and chips a1e preferr_.ed This gum is, prefeiably,
`ground to pass through a 100-mesh U S. standard
`sieve or finer. Larger particles may be incorpo-
`rated We have found, for example, that, with
`Batu'nubs and chips, the viscosity of the emul—
`sion varies as a function of the particle size.
`As an example of this effect of particle size,
`emulsions having the same proportions of con—
`stituents—namely, 100 parts hydrochloric acid,
`12 parts kerosene and 2 parts Batu nubs and
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`2,689,009
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`chips by weightw—were prepared with different
`sizes of gum particles. The viscosity after 30
`minutes as measured on the Halliburton thicken-
`ing time tester which is described in A. P. I.
`RP 10 B, Recommended Practice for Testing 011
`Well Cements, third edition, increased as the par-
`ticle size of the gum decreased, as indicated in
`the following table:
`Table
`
`Viscosity
`'Particle Size (Mesh) (Pom)
`
`—40____________________________________________________
`25
`32,
`~100...
`
`34
`—-200.._
`
`37
`—325.._
`
`
`Since, as pointed out hereinafter, a high initial
`viscosity for the emulsion is desirable, it can be
`seen that particles of 100 mesh or smaller are
`substantially superior to largei particles.
`.
`,
`The emulsion is prepared by first mixing be—
`tween about 5 and about 30 parts of this finely
`divided gum per 100 parts by weight of liquid
`hydrocarbon “They are mixed—p1eferably, at
`high shear rates—until the gum is evenly dis-
`persed in the hydrocarbon The ratio may be
`varied substantially, particularly on the high end,
`since pumpability is the limiting factor, and very
`viscous emulsions can be pumped. The amount
`of hydrocarbon used depends upon the amount
`of acid used, the hydrocarbon-acid ratio being in
`the range of about 6 to about 24 parts hydrocar—
`bon by weight per 100 parts acid.
`It has been
`found that these proportions may be varied sub-
`stantially and still obtain a desirable emulsion;
`but, when the ratio of hydrocarbon to acid is
`reduced materially below the preferred range,
`there isioften excess acid which separates from
`the emulsion'on standing. Also, when the ratio
`of hydrocarbon to acid is above the preferred
`range, excess hydrocarbon separates from the
`emulsion on standing.
`In general, it can be said,
`however, other things, including agitation, being
`equal, that the viscosity of the emulsion increases
`as the concentration of the kerosene decreases,
`until ,a point
`is reached at which excess acid
`separates from the emulsion on standing. The
`preferred composition range. is, therefore, on a
`weight basis, between about 1 and 5 parts—typi-
`cally 2 parts—gum and between about 6 and
`about 24 parts—typically 10 parts—liquid hydro-
`carbon per 100 parts acid.
`'
`The oily vehicle containing the dispersed finely
`divided gum may be emulsified with the acid by
`any number of means.
`It has been found, how-
`ever, that, by mixing the two in any of a number
`of well—known homogenizers, the viscosity of the
`emulsion is higher than where they are mixed
`at lower shear rates. For example, the acid and
`the oily vehicle containing the Batu may be mixed
`by running them together thro‘ughan ordinary
`pump, and viscosities as high as 50 poises may
`be obtained; where the same concentration of
`constituents is used and the rate of shear is
`increased by using a jet-type homogenizer the
`viscosity of the emulsion may be increased by
`two or more times. Accordingly, it can be seen
`that a viscosity in the range of between about
`25 and about 50 poises, which is the preferred
`range, may be obtained by varying the ratio of
`the constituents and by the method of mixing.
`In general, less than about 2 per cent Batu based
`on the weight of the acid is to be preferred Where
`the rate of mixing and/or length of mixing time
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`can be arranged, so that a viscosity in the pre-
`ferred range is obtained. Higher concentrations
`of the emulsifying agent may be used at increased
`breakdown time where mixing facilities do not
`provide adequate emulsion viscosity. Where the
`emulsifier does not provide a shear rate high
`enough to form a sufficiently viscous emulsion, it
`has been found that increased viscosity can be
`obtained by increasing the mixing time at a mod—
`erately high shear rate. In one case, for example,
`where 2 per cent, by weight Batu nubs and chips
`through loo-mesh U. S. standard sieve and 9.6
`, per cent by weight kerosene were incorporated in
`13° Bé. hydrochloric acid, the viscosity using a
`propeller-type mixer running at 1750 R. P. M.
`was found to increase from about 33 poises after
`5 minutes to about 38 poises after mixing the
`emulsion 15 minutes.
`This emulsion is pumped or flowed into the‘
`well, preferably into a confined zone at the bot—
`tom of
`the well,
`through tubing or the like.
`Another fluid—such as water, oil or acid—is then
`injected into the tubing following the emulsion
`If pumping or injection of the emulsion or the
`fluid following the emulsion is continued after
`the confined zone in the well becomes filled with
`the viscous emulsion, the hydraulic pressure on
`the fluid rises until the strength of the formation
`is overcome and the formation is fractured. The
`hydraulic, pressure in the confined zone necessary
`to produce a fracture has been found to vary in
`wells 2,000 feet or more in depth between about
`0.7' and about 1 pound per square inch per foot
`of, well depth. This pressure—i. e., the pressure
`required to fracture a formation or the pressure
`beyond which an increase in rate of injection will
`not materially increase the pressure—is herein-
`after referred to as the formation—breakdown
`pressure. It is generally recognized by an obser-
`vation of the pressure in the tubing or the pres—
`sure on the pumps, or it may be measured with
`a bottom-hole pressure gage. After the confined
`zone in the well becomes filled with emulsion, the
`pressure riseS‘sharply—assuming a substantial
`- volume, e. g., two or more barrels per minute, is
`beinginjected—until the pressure rise ceases to
`be'proportional to the volume of fluid injected
`into the’well.
`In fact, in many cases, after the
`confined zone has been filled with the emulsion
`and the formation-breakdown pressure has been
`reached, the pressure may decrease sharply, indi-
`cating that the emulsion is flowing into a frac-
`ture in the formation.
`In some cases, namely,
`about 25per cent of the jobs done to date, there
`isno material breakdown in pressure when the
`formation fractures, since the tensile strength of
`the rock is so low that, when the pressure in the
`confined zone is sufficient to lift the effective over—
`burden at that point, the formation parts, and
`the emulsion enters the formation and extends
`the fracture to great, distances from the well.
`Obviously, after the emulsion commences to enter
`and extend the fracture, the friction in the frac-
`ture being small, an increase in the pump rate
`will not materially increase the pressure at the
`elevation of the fracture. A formation fracture
`and the formation-breakdown pressure are there—
`fore readily recognized. Another means of indie»
`cating a. formation fracture is to note the slope
`of thepressure vs. volume curve at the surface.
`If, after the confinedzone of, the well is filled,
`the emulsion is pumped slowly into the well, it
`will leak away into the permeable formation at a
`rate depending upon the differential pressure
`between the Well and" the formation; and the
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`2,339,009
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`differential pressure Will 'vary directly as the rate
`of injection. However, after the formation frac-
`tures or when the formation-breakdown pressure
`has been reached, the ratio of volume of ;fluid :to
`pressure increases. Accordingly, theslopezof the
`pressure Vs. :pump rate cur—ve changes Whenthe
`formation fractures or when the formation—
`breakdown pressure has been reached.
`After the formation fractures, the emulsion
`enters the fracture‘whichlmay be-extendeda sub-
`stantial distance into the formation by continued
`pumping of the emulsion or the fluid following
`the emulsion. Anygamount-of-emulsion maybe
`injected into the fracture, depending upon .the
`extent of fracturedesired.
`In a typical treat-
`ment, between about 5500 and 2,000 gallons of
`emulsion are injected into the fracture.
`'When
`all of the emulsion has been injected into the
`fracture, the fluid following—which, - as indicated
`above, is preferably unemulsifiecl-or.plamzstrong
`mineral acid—.may also be injected into the
`fracture.
`As is well known, when strong mineral acids
`are reacted with well formations, «water-soluble
`salts are produced. While-the emulsions-andzthe
`emulsifying gum are not broken or afi'ected by
`the acid per se, we have found that, When the
`emulsion contacts a calcareous formation-andthe
`water-soluble salt is produced, the emulsion is
`broken. Apparently this-salt, some-surface efiect,
`a catalytic‘effect'of the‘calcareous formation, or,
`perhaps, the partial reaction of the—acid with the
`formation breaks the‘emulsion, freeing the acid
`for reaction Withthe-formation.
`The-plain acidfollowing the=emu1sionalso con-
`tacts the formation surrounding the fracture,=and
`the excess of reaction lproductror the additional
`reaction itself appears to insure breakdown of
`any emulsion which might not-otherwise «break
`down. The amount of plain acid following the
`emulsified acid is not believed to be critical.
`In
`fact, none is . actuallyrequire'd; but, by emulsify-
`ing‘o-nly partof thevacid, thereis someeconomic
`advantage plus the assurance that .the emulsion
`breaks more rapidly. Equal volumes :of emu’lsie
`fied and plain acid produce lvery desirable results.
`After the plain acid is injected into the forma—
`tion, the well may be closed infer a short time
`to allow the emulsion to break and the acid to
`react with the formation.
`In general, the time
`delay is greater than the delay whereplain acid is
`injected into a formation, since the reaction rate
`of the emulsion appears to be retarded by the
`emulsion. However, in about 24 hours, the vis—
`cosity of a kerosene-hydrochloric ‘acid emulsion
`of the preferred composition in the presence of
`excess limestone and at a bottom—hole'tempera-
`ture of 120° 'F. and pressure of 150013. sqi. has
`been found to "be reduced from about 50 ‘poises
`to about 5 centipoises,'the'viscosity'of the reac—
`tion product. This reaction :product may then
`be removed from the well by flowing the well,
`by pumping, or the like.
`'
`As an example of the operationpf this inven-
`tion, an emulsion having the ~f0110wing~composi-
`tion wasmade up and used to ‘treata well in the
`Fullerton Field, Andrews County, Texas: 260
`pounds of Batu nubs and chips ground to pass
`through loo-mesh U. S. standard siev'e were dis—
`persed in 200 gallons of kerosene by circulating
`the kerosene in a tank. This kerosene was then
`emulsified with 1500 gallons of 20 per cent hy-
`droc'hloric acid (.13.25° Bé.) by circulating the
`two solutions through :a tank with «a duplex,
`reciprocating pump “for about '60 minutes. At
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`that time, the viscosity of theemulsion was :about
`30 poises. The emulsion was then injected at
`the rate of about 110 ‘G. P. M. into a :‘confined
`zone'betwee’n’S'l 06 feet, andf6820 feet in‘ the Clear—
`fork, a dolomitic formation. This amount ‘of
`emulsion was insufficient to fill the confined .zone
`or the well and the two-inCh tubing; and, there-
`fore, theremulsion was followed with :plain‘acid.
`The pressure built up to a maximum of about
`4,300 p. s. i. surface :pressure before the “forma-
`tion fibroke , down and took the emulsion through
`a fracture.
`‘Theemulsion was "then injected into
`the fracture at about 3,000 p. s. 1i. ”It was fol—
`lowed in sequence by 3,500gallons of 715 percent
`plain hydrochloricaci‘d (10.12" Bé.) and 40 bar-
`rels of crude oil.
`Before this treatmentrand after fbeing-acidized
`with the same amount-of acid solution, the well
`produced 14 barrels of oil per day withno wa-
`ter. Two months after treatment and long aft-
`er the “load” oil had been recovered, the well
`produced 46 barrels of oil per day with no wa—
`ter. The increase in production following this
`treatment indicated that, even though the well
`[3.Cal
`'- had previouslybeen acidized with plain asid, new
`flow channels were produced. This indicated
`then that .a permeable fracture was created in
`the formation which increasedthe drainage area
`of the well and the permeability adjacent the
`well. Many other suCh treatments in wells in
`different formations,»both limestone and dolomit—
`ic, have yielded'similar improvements.
`While this invention has been described with
`reference to a ‘preferredaccmpositionand a pre-
`ferred procedure, it will be apparent that various
`modifications can be made Without departing
`from the spirit-of the invention. For example,
`it is sometimes desirable to suspend in the emul-
`sion a propping agent, such as sand, having a
`particle size in the range between about 10- and
`about 40—mesh U. s..standard sieve, so that, aft-
`er the ‘fracture is created and the emulsion is re-
`moved therefrom, the fracture will be held-open
`by these props. Other modifications will bea —
`parent to those skilled in the art.
`'The inven—
`tion should therefore not :be construed to be lim»
`ited by the above examples but should be lim»
`ited only by the scope of the appended claims.
`We claim:
`1. A composition cf matter comprising an
`emulsion of a strong mineral acid and an oily
`vehicle containing Batu ‘gum.
`2. A well—treating emulsion rcomprising finely
`divided ‘Batu gum, an oily 'vehicle,.and an acid
`capable of forming a water-soluble salt With
`earth formations.
`'3. A well—treating fluid comprising finely di-
`vided Batu gum dispersed in an oily vehicle and
`an acid capable of forming a water—soluble salt
`with earth formations, said acid being emulsi-
`fiedas the discontinuous phase within said oily
`vehicle.
`4..A well treating fluid comprising an emulsion
`of .hydrochloricvacid and a dispersion of a finely
`divided Batu‘gum in a compatible oily vehicle,
`saidacid being the discontinuousphase, and said
`oily vehicle being the continuous phase in said
`emulsion.
`'5. A well-treating fluid comprising anemrilsion
`of hydrochloric acid and between about 6 and
`about 2.4: parts 'by‘wéi‘ght of aliqu‘id‘hydrocarbon
`per 2100 parts of said acid, said hydrocarbon con-
`taining sufilcient
`finely divided Batu gum to
`emuISify substantially completely said acid and
`said hydrocarbon.
`'
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`56. A well—treating fluid comprising an emul-
`sion of hydrochloric acid and between about 6
`and about 24 parts by weight of a liquid hydro-
`carbon and between about 1 and about 5 parts
`by weight of finely divided Batu gum per 100
`parts of said acid.
`7 . A well—treating fluid comprising an emulsion
`of hydrochloric acid and between about 6 and
`about 24 parts by weight of a liquid hydrocar-
`bon per 100 parts of said acid, said hydrocarbon
`containing between about 5 and about 30 parts
`of finely divided Batu gum per 100 parts of said
`liquid hydrocarbon.
`8. A method of increasing the productivity of a
`calcareous formation penetrated by a well com—
`prising disposing adjacent said formation an
`emulsion of an acid capable of forming a water-
`soluble salt with said formation and a dispersion
`of finely divided Batu gum in a compatible oily
`vehicle, applying a hydraulic pressure as great
`as the formation-breakdown pressure to said
`emulsion to fracture said formation, and inject—
`ing said emulsion into said fracture.
`9. A method of increasing the productivity of a
`calcareous formation penetrated by a well com—
`prising isolating a'section of said well opposite
`said formation from the remainder of said well,
`disposing in said section an emulsion of an acid
`capable of forming a water-soluble salt with said
`formation and a dispersion of finely divided Batu
`gum in a compatible, oily vehicle, applying a hy—
`draulic pressure as great as the formation—break—
`down pressure to said emulsion to fracture said
`formation, and injecting said emulsion into said
`fracture.
`10. A method of increasing the productivity of
`a calcareous formation penetrated by a well com-
`prising isolating a section of said well opposite
`said formation from the remainder of said well,
`disposing in said section an emulsion of hydro—
`chloric acid and a liquid hydrocarbon containing
`sufficient finely divided Batu gum to emulsify
`substantially completely said acid and said hy-
`drocarbon, applying a hydraulic pressure as great
`as the formation-breakdown pressure to said
`emulsion to fracture said formation, and injecting
`said emulsion into said fracture.
`11. A method of increasing the productivity of
`a calcareous formation penetrated by a well
`comprising isolating a section of said well op— ,
`posite said formation from the remainder of said
`well, disposing in said section an emulsion of hy-
`drochloric acid solution, between about 6 and
`about 24 parts by weight of a liquid hydrocarbon
`and between about 1 and about 5 parts by weight
`of finely divided Batu gum per 100 parts of said
`acid solution, applying a hydraulic pressure as
`great as the formation breakdown pressure to said
`emulsion to fracture said formation, and inject-
`ing said emulsion into the fracture.
`12. A method of increasing the productivity of
`a calcareous formation penetrated by a well com-
`prising isolating a section of said well opposite
`said formation from the remainder of said well,
`disposing in said section an emulsion of hydro-
`chloric acid solution, between about 6 and about
`24 parts by weight of a liquid hydrocarbon, and
`between about 1 and about 5 parts by weight of
`finely divided Batu gum per 100 parts of said acid
`solution, applying a hydraulic pressure as great
`as the formation—breakdown pressure to said
`emulsion to fracture said formation, injecting said
`emulsion into said fracture causing said acid to
`react with said calcareous formation and break
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`said emulsion whereby the permeability of said
`formation is increased a substantial distance from
`said well and producing said well to remove the
`spent hydrochloric aéid solution and liquid hy-
`drocarbon from said well.
`13. A method of increasing the productivity of
`a calcareous formation penetrated by a well com—
`prising isolating a section of said well opposite
`said formation from the remainder of said well,
`disposing in said section an emulsion of hydro-
`chloric acid solution, between about 6 and about
`24: parts by weight of a liquid hydrocarbon, and
`between about 1 and about 5 parts by weight of
`finely divided Batu gum per 100 parts of said acid
`solution, applying to said emulsion a hydraulic
`pressure in the range between about 0.7 and about
`1 pound per foot of well depth to fracture said
`formation, displacing said emulsion into the frac-
`ture by injecting a plain acid solution into said
`well following said emulsion, and displacing said
`plain acid solution from said well by following said
`plain acid solution with another fluid whereby
`said emulsion is injected into said formation a
`substantial distance from said well, and said
`emulsion is broken so that the permeability of the
`flow channels to said well is increased a substan-
`tial distance from said well.
`14. A method of increasing the productivity of
`a calcareous formation penetrated by a well com-
`prising isolating a section of said well opposite
`said formation from the remainder of said well,
`‘ disposing in said section an emulsion of about
`100 parts by weight of about 13° Be. hydrochloric
`acid, about 10 parts by weight of kerosene, and
`about 2 parts by weight of finely divided Batu
`gum, applying to said emulsion in said section
`a hydraulic pressure in the range between about
`0.7 and about 1 pound per foot of well depth to
`fracture said formation, and displacing said emul-
`sion into the fracture.
`15. The method of increasing the productivity
`of a calcareous formation penetrated by a well
`which method comprises emulsifying a strong
`a mineral acid in an 0in vehicle containing an ef-
`fective amount of Batu gum to form a viscous
`emulsion initially having a viscosity in the range
`of about 25 to about 50 poises and being capable
`of becoming broken by contact with said cal—
`careous formation, introducing said viscous emul—
`sion into a confined zone of said well adjacent
`said formation, applying a hydrostatic pressure
`to said emulsion sufficient to fracture said forma—
`tion and to displace at least a part of said emul-
`sion into passages formed in the formation, allow-
`ing said emulsion‘to contact said passages for a
`time sufficient for at least a portion of the acid
`to react with the calcareous formation and the
`emulsion to be broken, and producing said well
`to remove liquids therefrom.
`16. A process of treating a well to increase the
`productivity of a calcareous formation penetrated
`by the well, which process comprises dispersing
`finely divided Batu gum in an oily vehicle in an
`amount sufficient
`to effect emulsification of a
`strong acid in said vehicle, emulsifying in said
`Batu gum—containing vehicle a strong acid ca-,
`pable of reacting with calcareous formations to
`form a water—soluble salt, said Batu gum-con-
`taining vehicle and said acid being mixed in
`amounts and for the period of time required to
`obtain initially an emulsion having a viscosity in
`therange of about 25 to 50 poises, said emulsion
`being capable of becoming broken by contact with
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`2,689,009
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`said calcareous formation, disposing said viscous
`emulsion in a confined zone in said well adjacent
`said calcareous formation, applying a pressure
`to said emulsion sufficient to fracture said forma-
`tion and to displace at least a part of said emul-
`sion into passages formed by said fracture where-
`by the acid component of said emulsion reacts
`with calcareous material to form a water—soluble
`salt and said emulsion is broken, and producing
`said well
`to remove fluids therefrom including
`liquid containing said water-soluble salt.
`17. The process of claim 16 wherein the par-
`ticle size of the finely divided Batu gum is smaller
`than 40 mesh, the oily vehicle is a hydrocarbon
`liquid, the amount of said oily vehicle is within
`the range of about 6 to about 24 parts by weight
`per hundred parts by weight of acid, and the
`amount of Batu gum is in the range of about 5
`to about 30 parts by weight based on the amount
`of oily vehicle.
`18. The process of claim 17 wherein the acid is
`hydrochloric acid having a concentration in the
`range of about 5° to about 20° Bé.
`19. The process of claim 17 wherein said oily
`
`10
`vehicle and said acid are homogenized to obtain
`said emulsion having a viscosity in the range of
`about 25 to 50 poises.
`20. The process of claim 17 which includes the
`step of following said viscous emulsion in said
`confined zone with plain acid to displace unemul-
`sified acid in addition to said emulsion into pas-
`sages formed by said fracture.
`
`‘10
`
`15
`
`20
`
`References Cited in the file of this patent
`UNITED STATES PATENTS
`Date
`Name
`De Groote __________ Aug. 15, 1933
`De Groote __________ Apr. 28, 1936
`De Groote __________ Aug. 11, 1936
`De Groote __________ Aug. 11, 1936
`Loomis et a1_________' July 26, 1933
`Benckenstein ______ July 25, 1944
`Reistle, Jr ___________ Apr. 3, 1951
`OTHER REFERENCES
`
`Number
`1,922,154
`2,038,720
`2,050,932
`2,050,933
`2,124,530
`2,354,570
`2,547,778
`‘
`
`“Hydrafrac Process,” by J. B. Clark, The Oil
`and Gas Journal, October 14, 1948, pages 76—79.
`
`Page 5 of 5
`Page 5 of 5
`
`