WO1995003140A1 - Method for removing alkaline earth scale from the interior surface of production tubing - Google Patents

Method for removing alkaline earth scale from the interior surface of production tubing Download PDF

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Publication number
WO1995003140A1
WO1995003140A1 PCT/US1994/007262 US9407262W WO9503140A1 WO 1995003140 A1 WO1995003140 A1 WO 1995003140A1 US 9407262 W US9407262 W US 9407262W WO 9503140 A1 WO9503140 A1 WO 9503140A1
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WO
WIPO (PCT)
Prior art keywords
scale
solvent
acid
production tubing
interior surface
Prior art date
Application number
PCT/US1994/007262
Other languages
French (fr)
Inventor
James Mark Paul
Original Assignee
Mobil Oil Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mobil Oil Corporation filed Critical Mobil Oil Corporation
Publication of WO1995003140A1 publication Critical patent/WO1995003140A1/en

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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
    • E21B37/00—Methods or apparatus for cleaning boreholes or wells
    • E21B37/06—Methods or apparatus for cleaning boreholes or wells using chemical means for preventing or limiting, e.g. eliminating, the deposition of paraffins or like substances
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/52—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning
    • C09K8/528—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning inorganic depositions, e.g. sulfates or carbonates
    • 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
    • E21B37/00—Methods or apparatus for cleaning boreholes or wells
    • 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
    • E21B37/00—Methods or apparatus for cleaning boreholes or wells
    • E21B37/02—Scrapers specially adapted therefor

Definitions

  • This invention relates to a method for removing alkaline earth scale, particularly strontium and barium sulfate scale, from the interior surface of poduction tubing.
  • alkaline earth metal cations such as barium, strontium, calcium and magnesium
  • anions such as sulfate, bicarbonate, carbonate, phosphate and fluoride.
  • concentrations which exceed the solubility product of the various species which may be formed precipitates form until the respective solubility products are no longer exceeded.
  • concentrations of the barium and sulfate ions exceed the solubility product of barium sulfate, a solid phase of barium sulfate will form as a precipitate.
  • Solubility products are exceeded for various reasons, such as evaporation of the water phase, change the pH, pressure or temperature and the introduction of additional ions which can form insoluble compounds with the ions already present in the solution.
  • Scale may prevent effective heat transfer, interfere with fluid flow, facilitate corrosive processes, or harbor bacteria. Scale is an expense problem in any industrial water system, in production systems for oil and gas, in pulp and paper mill systems, and in other systems, causing delays and shutdowns for cleaning and removal.
  • a method for removing barium sulfate and other sulfate scales by a solvent comprising a combination of a chelating agent together with catalyst or synergist.
  • the catalyst or synergist comprises anions of (1) a monocarboxylic acid such as acetic acid, hydroxyacetic acid, mercaptoacetic acid or salicylic acid; (2) oxalates; (3) thiosulfates or (4) nitriloacetic acid.
  • the chelating agent comprises polyamino- polycarboxylic acid such as EDTA or DTPA.
  • the scale is removed under alkaline conditions, preferably at pH values of about 8.0 to about 14.0, with best results being achieved at about pH 12.
  • the spent solvent is disposed of by re-injection into the subsurface formation or is regenerated.
  • a method for removing alkaline earth scale from the interior surface of production tubing comprising contacting the scale with a solvent while simultaneously milling the scale with a rotating mill head connected to a downhole motor.
  • solvent is an aqueous solution having a pH of about 8 to about 14 and comprises: a chelating agent comprising a polyaminopolycarboxylic acid present in a concentration of from 0.1 M to 1.0M or salt of such an acid, and a synergist in a concentration of from 0.1 to 1.0 M to dissolve the scale.
  • a chelating agent comprising a polyaminopolycarboxylic acid present in a concentration of from 0.1 M to 1.0M or salt of such an acid
  • a synergist in a concentration of from 0.1 to 1.0 M to dissolve the scale.
  • the chelating agent comprises DTPA or EDTA.
  • the scale may consists of barium, strontium or calcium sulfate and mixtures thereof and naturally occurring radioactive material (NORM), mainly radium 226 and radium 228.
  • NEM naturally occurring radioactive material
  • the synergist comprises a onocarboxylic acid anion; an oxalate anion; a thiosulfate anion; or a nitriloacetate anion.
  • the monocarboxylic acid is desirably salicylic acid or a substituted acetic acid. It is preferred that the pH of the solvent is substantially 12.
  • the solvent may be brought to the specified pH by the addition of a potassium base.
  • the scale is desirably contacted with the solvent at a temperature from 25°C to 100°C.
  • the downhole motor is preferably connected to coiled tubing extended downhole inside the production tubing and the solvent is injected into the interior surface of the production tubing containing scale via the coiled tubing and mill head.
  • alkaline earth sulfate scales are removed from the interior surface of downhole production tubing by contacting the scale with an aqueous scale- removing solvent while simultaneously milling the scale with a rotating working drill or mill head connected to a downhole motor.
  • the scale itself is usually in the form of an adherent deposit of a scale-forming mineral on the interior surface of the downhole production tubing which has been exposed to water containing the scale-forming components.
  • These components comprise alkaline earth metals including calcium, strontium and barium, together with variable amounts of radium, depending upon the origin of the waters.
  • Barium sulfate scale is particularly difficult to remove by existing chemical methods in view of its very low solubility.
  • the present invention removes the scale deposits on the interior surface of the downhole production tubing by contacting the scale with an aqueous solvent while simultaneously milling the scale with a rotating working drill or mill head connected to coiled tubing.
  • the aqueous solvent comprises a chelating agent and a synergist to dissolve the scale as disclosed in US- A-4980077.
  • the pH of the solvent is maintained at pH values of about 8.0 to about 14.0, preferably at about 11 to 13, and preferably about 12.
  • Suitable chelating agents comprise poly- aminopolycarboxylic acid such as EDTA or DTPA which is intended to form a stable complex with the cation of the alkaline earth scale forming material.
  • the chelant may be added to the solvent in the acid form or, alternatively, as a salt of the acid, preferably the potassium salt.
  • concentration of the chelant in the aqueous solvent should normally be in the range of 0.1 M to 1.0 M.
  • concentration of the synergist in aqueous solvent will also be in the range of 0.1 M to 1.0 M. In any event the alkaline conditions used in the scale removal process will convert the free acid to the salt.
  • the preferred synergist is the oxalate anion as described in US-A-4980077.
  • the oxalate is preferably used in an amount of about 0.1 to 1.0 M, more preferably about 0.5 M, with a pH of 8.0 to 14.0, preferably 11 to 13, and usually about 12.
  • the desired pH value is obtained by the addition of a base, preferably a potassium base such as caustic potash, potassium hydroxide.
  • An alternative synergist is a monocarboxylic acid anion, preferably salicylate, as described in our US-A-5084105.
  • the thiosulfate or nitriloacetic acid synergists described in our US-A-5049297 may also be used.
  • the amounts of the chelant used with the monocarboxylic acid and other synergists are comparable to the amounts used with the oxalate synergists, and comparable solution pH values are also used, i.e. chelant and synergist concentration from 0.1 to 1.0 M, usually about 0.5 M, solution pH from 8 to 14, usually 11 to 13 and, for best results, about 12.
  • the preferred solvents comprise about 0.1 to about 1.0 M of ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA) , or salts of these acids, as a chelant.
  • EDTA ethylenediaminetetraacetic acid
  • DTPA diethylenetriaminepentaacetic acid
  • the preferred oxalate synergist is added to the aqueous solution in about 0.1 to about 1.0, preferably about up to 0.5 M.
  • the pH of the solvent is then adjusted by the addition of a base to the desired value, preferably to about pH 12.
  • a base preferably to about pH 12.
  • Potassium is preferred for economy as well as availability.
  • the normal course of making up the solvent will be to dissolve the chelant and the oxalic acid (or potassium oxalate) in the water to the desired concentration, after which a potassium base, usually potassium hydroxide is added to bring the pH to the desired value of about 12.
  • the drawing schematically illustrates a use of the present method. It shows a permeable subterranean formation 10 penetrated by the borehole of a well 12.
  • the well contains a perforated casing 14.
  • a production tubing 16 extends inside casing 14 to a point near the bottom of the oil formation 10.
  • Coiled tubing 18 is pushed down inside the production tubing 16 onto which is attached a working drill or mill head 20 connected to a downhole motor (not shown) .
  • the drill or mill head 20 is rotated by the electric downhole motor attached to the coiled tubing 18.
  • barium sulphate scale 22 forms on the interior surface of the production tubing 16. Once the scale 22 forms sufficiently to reduce production of the well the well is shut in and coiled tubing 18 with the working drill or mill head 20 is lowered into the production tubing 16 to a point adjacent the scale. Suitable coil tubing is disclosed in an article by Martyn Beardsell, Mark Corrigan and Ken Newman, entitled “The Coiled Tubing Revolution", published by Reservoir Engineering. A scale-removing solvent is injected into the interior surface walls of the production tubing 16 containing the scale 22 from the bottom of mill head 20 via the coiled tubing while simultaneously milling the barium sulphate scale by the rotating mill head 20.
  • the scale 22 is dissolved into the solvent and the solvent containing dissolved scale flows upward via the tubing annulus 24 and is carried to the top of the well for recovery.
  • the solvent plays a dual role in the well: first, as a cooling fluid for the mechanical drill, and secondly as an efficient solvent for the milled scale cuttings released into the fluid.
  • Some other advantages of the combination treatment includes: softening very hard scale before drilling, increased bit life, prevention of scale sloughing into the well and possible tool sticking, increased scale dissolution and removal of solids by circulation.
  • the high specific gravity of the solvent also enhances the removal, by circulation, of heavy scale particles that are released by milling/drilling.
  • Softening the scale before milling is also advantageous in order to prevent damage to downhole equipment, such as plugs and equipment, by milling over shots.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Geology (AREA)
  • Chemical & Material Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Fluid Mechanics (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Abstract

A method of removing alkaline earth sulfate scale (22) from the interior surface of downhole production tubing (16) comprising contacting the scale with a solvent while simultaneously milling the scale with a rotating mill head (20) connected to a downhole motor.

Description

METHOD FOR REMOVING ALKALINE EARTH SCALE FROM THE INTERIOR SURFACE OF PRODUCTION TUBING
This invention relates to a method for removing alkaline earth scale, particularly strontium and barium sulfate scale, from the interior surface of poduction tubing.
Many waters contain alkaline earth metal cations, such as barium, strontium, calcium and magnesium, and anions, such as sulfate, bicarbonate, carbonate, phosphate and fluoride. When combinations of these anions and cations are present in concentrations which exceed the solubility product of the various species which may be formed, precipitates form until the respective solubility products are no longer exceeded. For example, when the concentrations of the barium and sulfate ions exceed the solubility product of barium sulfate, a solid phase of barium sulfate will form as a precipitate. Solubility products are exceeded for various reasons, such as evaporation of the water phase, change the pH, pressure or temperature and the introduction of additional ions which can form insoluble compounds with the ions already present in the solution.
As these reaction products precipitate on the surfaces of the water-carrying or water-containing system, they form adherent deposits or scale. Scale may prevent effective heat transfer, interfere with fluid flow, facilitate corrosive processes, or harbor bacteria. Scale is an expense problem in any industrial water system, in production systems for oil and gas, in pulp and paper mill systems, and in other systems, causing delays and shutdowns for cleaning and removal.
In US-A-4980077, US-A-4990718, US-A-5049297 and US-A- 5084105 there is disclosed a method for removing barium sulfate and other sulfate scales by a solvent comprising a combination of a chelating agent together with catalyst or synergist. The catalyst or synergist comprises anions of (1) a monocarboxylic acid such as acetic acid, hydroxyacetic acid, mercaptoacetic acid or salicylic acid; (2) oxalates; (3) thiosulfates or (4) nitriloacetic acid. The chelating agent comprises polyamino- polycarboxylic acid such as EDTA or DTPA. The scale is removed under alkaline conditions, preferably at pH values of about 8.0 to about 14.0, with best results being achieved at about pH 12. When the solvent becomes saturated with scale metal cations, the spent solvent is disposed of by re-injection into the subsurface formation or is regenerated.
It is common practice when using scale dissolvers to pump a slug or volume of solvent into the well and leave it to stand static for a long period of time. This is not effective from an economic stand point because the well must be shut in for long periods of time, resulting in loss of production. Soaking is also not an efficient method from a reaction rate standpoint. Also, circulating scale solvent into the well bore is too costly, due to the large volume of solvent needed to fill the tubing and allow circulation. The article by A.D.F. Brown, S.J. Merrett, and J.S. Putman, entitled "Coil-Tubing Milling/Underreaming of Barium Sulphate Scale and Scale Control in the Forties Field", published by the Society of Petroleum Engineers in 1991 discloses milling barium sulphate scale from the interior walls of downhole production tubing using coiled tubing with a downhole motor which rotates an underreamer and/or bit.
According to the present invention there is provided a method for removing alkaline earth scale from the interior surface of production tubing, comprising contacting the scale with a solvent while simultaneously milling the scale with a rotating mill head connected to a downhole motor.
Advantageously, solvent is an aqueous solution having a pH of about 8 to about 14 and comprises: a chelating agent comprising a polyaminopolycarboxylic acid present in a concentration of from 0.1 M to 1.0M or salt of such an acid, and a synergist in a concentration of from 0.1 to 1.0 M to dissolve the scale.
Preferably, the chelating agent comprises DTPA or EDTA.
The scale may consists of barium, strontium or calcium sulfate and mixtures thereof and naturally occurring radioactive material (NORM), mainly radium 226 and radium 228.
Preferably, the synergist comprises a onocarboxylic acid anion; an oxalate anion; a thiosulfate anion; or a nitriloacetate anion.
The monocarboxylic acid is desirably salicylic acid or a substituted acetic acid. It is preferred that the pH of the solvent is substantially 12. The solvent may be brought to the specified pH by the addition of a potassium base.
The scale is desirably contacted with the solvent at a temperature from 25°C to 100°C. The downhole motor is preferably connected to coiled tubing extended downhole inside the production tubing and the solvent is injected into the interior surface of the production tubing containing scale via the coiled tubing and mill head.
According to the present invention, alkaline earth sulfate scales, especially barium sulfate, calcium sulfate and strontium sulfate scale, are removed from the interior surface of downhole production tubing by contacting the scale with an aqueous scale- removing solvent while simultaneously milling the scale with a rotating working drill or mill head connected to a downhole motor. The scale itself is usually in the form of an adherent deposit of a scale-forming mineral on the interior surface of the downhole production tubing which has been exposed to water containing the scale-forming components. These components comprise alkaline earth metals including calcium, strontium and barium, together with variable amounts of radium, depending upon the origin of the waters. Barium sulfate scale is particularly difficult to remove by existing chemical methods in view of its very low solubility.
The present invention removes the scale deposits on the interior surface of the downhole production tubing by contacting the scale with an aqueous solvent while simultaneously milling the scale with a rotating working drill or mill head connected to coiled tubing. The aqueous solvent comprises a chelating agent and a synergist to dissolve the scale as disclosed in US- A-4980077. The pH of the solvent is maintained at pH values of about 8.0 to about 14.0, preferably at about 11 to 13, and preferably about 12. Suitable chelating agents comprise poly- aminopolycarboxylic acid such as EDTA or DTPA which is intended to form a stable complex with the cation of the alkaline earth scale forming material. The chelant may be added to the solvent in the acid form or, alternatively, as a salt of the acid, preferably the potassium salt. The concentration of the chelant in the aqueous solvent should normally be in the range of 0.1 M to 1.0 M. The concentration of the synergist in aqueous solvent will also be in the range of 0.1 M to 1.0 M. In any event the alkaline conditions used in the scale removal process will convert the free acid to the salt.
The preferred synergist is the oxalate anion as described in US-A-4980077. The oxalate is preferably used in an amount of about 0.1 to 1.0 M, more preferably about 0.5 M, with a pH of 8.0 to 14.0, preferably 11 to 13, and usually about 12. The desired pH value is obtained by the addition of a base, preferably a potassium base such as caustic potash, potassium hydroxide.
An alternative synergist is a monocarboxylic acid anion, preferably salicylate, as described in our US-A-5084105. The thiosulfate or nitriloacetic acid synergists described in our US-A-5049297 may also be used. The amounts of the chelant used with the monocarboxylic acid and other synergists are comparable to the amounts used with the oxalate synergists, and comparable solution pH values are also used, i.e. chelant and synergist concentration from 0.1 to 1.0 M, usually about 0.5 M, solution pH from 8 to 14, usually 11 to 13 and, for best results, about 12.
The preferred solvents comprise about 0.1 to about 1.0 M of ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA) , or salts of these acids, as a chelant. In addition, the preferred oxalate synergist is added to the aqueous solution in about 0.1 to about 1.0, preferably about up to 0.5 M. The pH of the solvent is then adjusted by the addition of a base to the desired value, preferably to about pH 12. We have found that it is advantageous to avoid the use of sodium cations when operating at high pH values, about pH 8, and instead, to use potassium or, alternatively, cesium as the cation of the scale-removing agent.
Potassium is preferred for economy as well as availability. Thus, the normal course of making up the solvent will be to dissolve the chelant and the oxalic acid (or potassium oxalate) in the water to the desired concentration, after which a potassium base, usually potassium hydroxide is added to bring the pH to the desired value of about 12.
The mode of operation of the synergist is not presently understood. While not desiring to be bound to a particular theory concerning the actual mechanism of its activity in converting or dissolving the scale, it is believed that adsorption of the synergist on the barium sulfate surface may modify the surface crystal structure in such a way that the barium in the modified crystal is easily removed by the chelating agent.
Reference is now made to the accompanying drawing, which schematically illustrates a method in accordance with this invention in which scale deposits are removed from the interior surface of downhole production tubing by contacting the scale with a solvent while simultaneously milling the scale walls with a rotating working drill or mill head connected to a downhole motor.
The drawing schematically illustrates a use of the present method. It shows a permeable subterranean formation 10 penetrated by the borehole of a well 12. The well contains a perforated casing 14. A production tubing 16 extends inside casing 14 to a point near the bottom of the oil formation 10.
Coiled tubing 18 is pushed down inside the production tubing 16 onto which is attached a working drill or mill head 20 connected to a downhole motor (not shown) . The drill or mill head 20 is rotated by the electric downhole motor attached to the coiled tubing 18.
During production operations, barium sulphate scale 22 forms on the interior surface of the production tubing 16. Once the scale 22 forms sufficiently to reduce production of the well the well is shut in and coiled tubing 18 with the working drill or mill head 20 is lowered into the production tubing 16 to a point adjacent the scale. Suitable coil tubing is disclosed in an article by Martyn Beardsell, Mark Corrigan and Ken Newman, entitled "The Coiled Tubing Revolution", published by Reservoir Engineering. A scale-removing solvent is injected into the interior surface walls of the production tubing 16 containing the scale 22 from the bottom of mill head 20 via the coiled tubing while simultaneously milling the barium sulphate scale by the rotating mill head 20. The scale 22 is dissolved into the solvent and the solvent containing dissolved scale flows upward via the tubing annulus 24 and is carried to the top of the well for recovery. The solvent plays a dual role in the well: first, as a cooling fluid for the mechanical drill, and secondly as an efficient solvent for the milled scale cuttings released into the fluid. Some other advantages of the combination treatment includes: softening very hard scale before drilling, increased bit life, prevention of scale sloughing into the well and possible tool sticking, increased scale dissolution and removal of solids by circulation. The high specific gravity of the solvent also enhances the removal, by circulation, of heavy scale particles that are released by milling/drilling. Softening the scale before milling is also advantageous in order to prevent damage to downhole equipment, such as plugs and equipment, by milling over shots.

Claims

Claims
1. A method for removing alkaline earth scale from the interior surface of production tubing, comprising contacting the scale with a solvent while simultaneously milling the scale with a rotating mill head connected to a downhole motor.
2. A method according to claim 1, wherein the solvent is an aqueous solution having a pH of about 8 to about 14 and comprises: a chelating agent comprising a polyaminopolycarboxylic acid present in a concentration of from 0.1 M to 1.0M or salt of such an acid, and a synergist in a concentration of from 0.1 to 1.0 M to dissolve the scale.
3. A method according to claim 2, wherein the chelating agent comprises DTPA or EDTA.
4. A method according to claim 1 wherein the scale consists of barium, strontium or calcium sulfate and mixtures thereof and naturally occurring radioactive material (NORM) , mainly radium 226 and radium 228.
5. A method according to claim 2, in which the synergist comprises a monocarboxylic acid anion; an oxalate anion; a thiosulfate anion; or a nitriloacetate anion.
6. A method according to claim 5, in which the monocarboxylic acid is salicylic acid or a substituted acetic acid.
7. A method according to claim 1 in which the pH of the solvent is substantially 12.
8. A method according to claim 1, in which the solvent is brought to the specified pH by the addition of a potassium base.
9. A method according to claim 1, in which the scale is contacted with the solvent at a temperature from 25°C to 100°C.
10. A method according to claim 1, wherein the downhole motor is connected to coiled tubing extended downhole inside the production tubing and the solvent is injected into the interior surface of the production tubing containing scale via the coiled tubing and mill head.
PCT/US1994/007262 1993-07-26 1994-06-28 Method for removing alkaline earth scale from the interior surface of production tubing WO1995003140A1 (en)

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US096,249 1993-07-26

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004003101A1 (en) * 2002-06-28 2004-01-08 Halliburton Energy Services, Inc. System and method for removing particles from a well bore
CN104602829A (en) * 2012-07-05 2015-05-06 Sld强化开采有限公司 Apparatus for removal of alkaline earth metal salt scale and method

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4980077A (en) * 1989-06-22 1990-12-25 Mobil Oil Corporation Method for removing alkaline sulfate scale
US5049297A (en) * 1989-04-03 1991-09-17 Mobil Oil Corporation Sulfate scale dissolution
US5084105A (en) * 1989-04-03 1992-01-28 Mobil Oil Corporation Sulfate scale dissolution

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5049297A (en) * 1989-04-03 1991-09-17 Mobil Oil Corporation Sulfate scale dissolution
US5084105A (en) * 1989-04-03 1992-01-28 Mobil Oil Corporation Sulfate scale dissolution
US4980077A (en) * 1989-06-22 1990-12-25 Mobil Oil Corporation Method for removing alkaline sulfate scale

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
SOCIETY OF PETROLEUM ENGINEERS, September 1991, A.D. BROWN, S.J. MERRET and J.S. PUTMAN, (BROWN et al.), "Coil-Tubing Milling/Underreaming of Barium Sulphate Scale and Scale Control in the Forties Field", pages 2-3. *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004003101A1 (en) * 2002-06-28 2004-01-08 Halliburton Energy Services, Inc. System and method for removing particles from a well bore
US6968898B2 (en) 2002-06-28 2005-11-29 Halliburton Energy Services, Inc. System and method for removing particles from a well bore penetrating a possible producing formation
CN104602829A (en) * 2012-07-05 2015-05-06 Sld强化开采有限公司 Apparatus for removal of alkaline earth metal salt scale and method

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