CA1145902A - Gelled pigs for cleaning and sanitizing pipelines - Google Patents
Gelled pigs for cleaning and sanitizing pipelinesInfo
- Publication number
- CA1145902A CA1145902A CA000362839A CA362839A CA1145902A CA 1145902 A CA1145902 A CA 1145902A CA 000362839 A CA000362839 A CA 000362839A CA 362839 A CA362839 A CA 362839A CA 1145902 A CA1145902 A CA 1145902A
- Authority
- CA
- Canada
- Prior art keywords
- pig
- gelled
- aqueous
- pipeline
- crosslinked
- 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
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto
- B08B9/02—Cleaning pipes or tubes or systems of pipes or tubes
- B08B9/027—Cleaning the internal surfaces; Removal of blockages
- B08B9/04—Cleaning the internal surfaces; Removal of blockages using cleaning devices introduced into and moved along the pipes
- B08B9/053—Cleaning the internal surfaces; Removal of blockages using cleaning devices introduced into and moved along the pipes moved along the pipes by a fluid, e.g. by fluid pressure or by suction
- B08B9/055—Cleaning the internal surfaces; Removal of blockages using cleaning devices introduced into and moved along the pipes moved along the pipes by a fluid, e.g. by fluid pressure or by suction the cleaning devices conforming to, or being conformable to, substantially the same cross-section of the pipes, e.g. pigs or moles
- B08B9/0555—Gelled or degradable pigs
Abstract
Abstract Pipeline interiors are treated by passing through said pipeline an aqueous gelled pig containing an aqueous, cross-linked gelled galactomannan gum, or derivative thereof. A bactericide may optionally be included in the gelled pig to sanitize the interior of the pipe. The interior surface of a pipeline may optionally be dried by sequentially passing through the pipeline an aqueous cross-linked gelled pig, a fluid mobility buffer comprising a non-crosslinked gelled alkanol of from one to three carbon atoms, and a des-sicating amount of a liquid alkanol from one to three carbon atoms.
27,974A-F
27,974A-F
Description
METHOD FOR CLEANING AND
SANITIZING THE INTERIOR OF PIPELINES
This invention pertains to a novel method for treating the interior surfaces of pipelines uslng -aqueous, cross-linked gelled pigs.
.
Pipeline efficiency and volume of product being conveyed through the pipeline can be lost by a build-up of scale on the interior surface of the pipe.
~ Mechanical pigs and/or gelled chemical pigs have pre-; viously been used to remove scale from the interior ; surface of a pipe. Mechanical piys are, normally solid bullet-shaped devices which have wire brushes or abrasive surfaces to physically abrade the scale adhered to the interior surface of the pipe. Gelled chemical pigs, on ` the other hand, remove suxface deposits on the interior surface of a pipe by dissolution and/or by picking up loose debris as they pass through the pipeline.
In many instances, scale also contains bac~
teria which attack the product to be conv~yed by the pipeline. ~For example, sulfate-reducing bacteria can generate copiou~ quantities of gaseous hydrogen sulfide from certain crude oils, which causes severe corrosion of pipeline walls and also contaminate the product ::
SANITIZING THE INTERIOR OF PIPELINES
This invention pertains to a novel method for treating the interior surfaces of pipelines uslng -aqueous, cross-linked gelled pigs.
.
Pipeline efficiency and volume of product being conveyed through the pipeline can be lost by a build-up of scale on the interior surface of the pipe.
~ Mechanical pigs and/or gelled chemical pigs have pre-; viously been used to remove scale from the interior ; surface of a pipe. Mechanical piys are, normally solid bullet-shaped devices which have wire brushes or abrasive surfaces to physically abrade the scale adhered to the interior surface of the pipe. Gelled chemical pigs, on ` the other hand, remove suxface deposits on the interior surface of a pipe by dissolution and/or by picking up loose debris as they pass through the pipeline.
In many instances, scale also contains bac~
teria which attack the product to be conv~yed by the pipeline. ~For example, sulfate-reducing bacteria can generate copiou~ quantities of gaseous hydrogen sulfide from certain crude oils, which causes severe corrosion of pipeline walls and also contaminate the product ::
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f~
~2--flowing in the line. Hydrogen sulfide is also a noxious, toxic gas which makes it difficult and dangerous to handle from a personnel standpoint and also from a pump-ing standpoint. Gases in a liquid can cause pumps to cavitate, lose prime, or to function less efficiently.
Bacteria are also known to consume h~drocarbons, result-ing in a 105s of the product.
Because water is an undesirable foreign matter in any oil or gas pipeline, the treatment of pipelines with gelled pigs also includes their drying. One method of drying a pipeline is described by G.D.H. Crawford, Gas Journal, Volume 341, No. 5549, 282 (March 18, 1970).
In Crawford, the bulk of the water is removed from a pipeline by a conventional mechanical pig and then swab-bing the interior of the pipeline by passing a quantity of methanol through the pipeline sandwiched between a pair of pigs. Crawford found it necessary to use this technique to remove residual water from pipelines carry-ing natural gas having a high proportion of methane.
Residual water was said to form hydrates with the methane mder certain conditions of temperature and pressure and lead to serious transmission difficulties.
The invention resides in a method of cleaning the interior of a pipeline comprising passing through said pipeline an aqueous gelled pig containing an aqueous cross-linked gelled galactomannan gum, or derivative thereof, wherein said gum, or derivative thereof, is present in said gelled pig in an amount of at least about 40 pounds per 1000 gallons of water.
The invention further resides in a method of sequentially passing through said pipeline (a) an aqueous 27~974A-F -2-., . ' .
.
-
' : ' , . . ~ ::
.
f~
~2--flowing in the line. Hydrogen sulfide is also a noxious, toxic gas which makes it difficult and dangerous to handle from a personnel standpoint and also from a pump-ing standpoint. Gases in a liquid can cause pumps to cavitate, lose prime, or to function less efficiently.
Bacteria are also known to consume h~drocarbons, result-ing in a 105s of the product.
Because water is an undesirable foreign matter in any oil or gas pipeline, the treatment of pipelines with gelled pigs also includes their drying. One method of drying a pipeline is described by G.D.H. Crawford, Gas Journal, Volume 341, No. 5549, 282 (March 18, 1970).
In Crawford, the bulk of the water is removed from a pipeline by a conventional mechanical pig and then swab-bing the interior of the pipeline by passing a quantity of methanol through the pipeline sandwiched between a pair of pigs. Crawford found it necessary to use this technique to remove residual water from pipelines carry-ing natural gas having a high proportion of methane.
Residual water was said to form hydrates with the methane mder certain conditions of temperature and pressure and lead to serious transmission difficulties.
The invention resides in a method of cleaning the interior of a pipeline comprising passing through said pipeline an aqueous gelled pig containing an aqueous cross-linked gelled galactomannan gum, or derivative thereof, wherein said gum, or derivative thereof, is present in said gelled pig in an amount of at least about 40 pounds per 1000 gallons of water.
The invention further resides in a method of sequentially passing through said pipeline (a) an aqueous 27~974A-F -2-., . ' .
.
-
3-crosslinked gelled pig containing an aqueous crosslinkea gelled galactomannan gum, or derivative thereof, wherein said gum, or derivative thereof, is present in said gelled pig in an amount of at least about 40 pounds per 1000 gallons of water; (b) a fluid mobility buffer com-prising a non-crosslinked gelled alkanol of from one to three carbon atoms, and (c) a dessicating amount of a liquid alkanol of from one to three carbon atoms. The mobility buffer permits the user to derive the benefits of both the gelled aqueous pigs and a liquid dessicat-ing alkanol.
The aqueous gelled crosslinked pigs used in this invention are superior to other pigs which utilize, for example, polyacrylamides and the like for the gel matrix. This superiority is shown in their shear sta-bility, ease of hydration in water, and the convenience with which the gelled pigs are broken when the job is complete. This facilitates waste disposal and enhances the commercial viability.
It has also been discovered that pipelines can be cleaned and simultaneously sanitized by pas~ing an aqueous gelled pig containing at leas-t one bacteri-cide through the interior of a pipeline. By the term, "sanitize" is meant that the bacteria level of the pipe-line surface in contact with the aqueous gelled pig is reduced. Normally, the bacteria level is reduced to essentially zero or some other very low value~
The aqueous gelled pigs of the present inven-tion are easily formulated, are easy to use, and elimi-nate the need for completely filling a pipeline with an ;
27,97~A-F -3- ~
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.
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3a-antibacterial solution and thus represent an advance-ment in the art of pipeline cleaning.
The aqueous-based pig compositions comprise water, a galactomannan gum or derivative thereof as a thickening agent, and a crosslinker. The pig composi-tions may optionally contain a bactericide as an addi-tive.
27,974A-F -3a-:, , , , .
s~z Other additives may include an abrasive in solid particu-lat~ form (e.g. sand) to promote the cleaning ability of the pig as it passes through the pipeline, or other conventional additives which stabilize the piy.
Galactomannan gums and derivatives thereof are well known thickeners for water and water-based fluids. Examples of ~uch gums include natural gums (e.g. guar gum, locust bean gum, endosperm seed gums, and the like) and derivatives thereof (e.g. hydroxy-alkyl galactomannans, carboxyalkyl galactomannans, hydroxyalkyl carboxyalkyl galactomannans, and the like). These are known classes of compounds and essentially any member can be used in the present invention. The most common commerically employed galactomannan gums are guar, hydroxypropyl guar, hydroxyethyl guar, hydroxyethyl carboxymethyl guar, and carboxymethyl guar gums. Because -the aforementioned gums are readily commercially available, these gums are preferred thickeners, and of these, guar gum and hydroxy-propyl guar gum are the most preferred. It should be ; noted that;in some references the galactomannan gums are referred to as polysaccharide and polysaccharide derivatives. Any member of this known class of thickening agents can be used in the invention. Such thickeners are normally used in amounks of from 40 to 150 pounds ~ per 1000 gallons of water (i.e. from 0.5 to 1.8 percent ; by wt). They are preferably used in amounts of from 40 ; to 80 pounds per 1000 gallons of water (i.e. from 0.5 to 1.0 percent by wt). The actual amount used, however, can b~ adjusted to convenience by the practitioner.
~ queous compositions containing the abovethickeners are normally cross-lin~ed using a polyvalent 27,974A-F -4-:: .
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,:
,~ : ~ . " : ~:
~s~z metal ion. The cross-linker is normally added as a soluble salt or as a soluble organometallic compound in an amount sufficient to achieve the desired amount of cross-linking. Borates, organotitanates, and organo-zirconium salts are commonly used. The cross-linking ability of such compounds is pH dependent in many instances (e.g. the borate systems). This factor presents a convenient mechanism for dealing with the thickened fluids in a non-crosslinked form unkil the properties of a cross-linked fluid are desired. In the non-crosslinked state, the thickened aqueous fluids are normally pumpable at conventional pressures. Sub-stantially elevated pressures are required to pump the fluids in the cross-linked state.
The galactomannan gums and cross-linkers are, as noted, known classes of compounds and are disclosed in U.S. Patent Nos. 3,058,909; 3,974,077; 3,818,991;
3,779,914 and 3,696,035. Reference is also made -to the disclosure in the text by Davidson and Sittig, "Water-soluble Resins" Second Edition (1968) and the text by Smith and Montgomery, "The Chemistry of Plant Gums and Mucilages", Biograph Series No. 141 (1959).
Normally, the pig is formulated outside of the pipeline as a pumpable mass and the cross-linker or cross-linker/activator is added to the pumpable mass as it is being pumped into the pipeline. This "on-the-fly"
approach has several procedural adv~ntages, not the least of which is ease of placement at con~enient low pressures~. In this manner, the pig forms a cross-linked gel network after it enters the pipeline and conforms to the general shape and size of the pipeline. To illustrate, an aqueous pig comprised of a borate cross-linked polysaccharide (or polysaccharide derivative) 27,974A-F -5-:
' ~5913Z
gel is a preferred pig composition where the pig may be subjected to considerable shear. Such pig formations are conveniently prepared and used by first blending boric acid (from 2 to 4 pounds) with an aqueous slurry or solution of the polysaccharide or polysaccharide derivativé ~from 60 to 80 pounds) to form a pumpable homogeneous mass. Sufficient base (e.g. aqueous NaOH) is then metered in to change the pH to a basic pH
(pH 8.5-10 normally) as the homogeneous aqueous mass is being pumped into the pipeline. The desired quan-tities of boric acid and polysaccharide or derivative are present per 1000 gallons of water in each instance in the pipeline. The gel-time of these borate-cross-linked systems is easily adjusted by the quantity of base added (cross-linking occurs faster at higher pE values).
After the gelled pig has been formed in the pipeline, it is normally driven through the pipeline by the driving force of a fluid under pressure. This fluid may be a gas or a liquid and will vary depending upon the needs of the user. For example, if the user wishes to leave the pipeline in a dry, empty state, one would normally use a dry inert gas such as, for example, nitrogen, carbon dioxide, ethane, propane, or liquified petroleum gas. If the user desires to refill the pipeline with a liquid product such as, for example, crude oil or gasoline the pig could be driven with the liquid product, so long as the product does not adversely affect the properties of the pig before its purpose was complete or substantially complete in the pipeline.
~0 Normally the pigs are formulated and used at ambient temperatures or below and are pumped through the pipelines at pressures sufficient to move the pig : : .
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at a reasonable rate. Temperatures are therefore normally below about 140F. Pressures are normally below about 2000 psig. The predominant number of pipelines will normally be cleaned at pressures less than 500 psig. ~inear flow rates of up to about 5 feet/second are normally satisfactory, from a commercial cleaning standpoint. Rates of from 0.75 to 1.25 ft/sec.
are preferred.
The size and shape of the pipeline is basic-ally irrelevant because the gelled pigs are able to bepumped through the pipe over long distances and their shapes will adjust to fit the size of the pipeline during use. This makes the gelled pig extremely effec-tive because stalactites and stalagmites in the pipeline do not cause its destruction by ripping and tearing it apart as they do solid mechanical pigs.
The aqueous gelled pigs can be used alone or as an element of a pig train in the pipeline cleaning process. In the latter instance, the aqueous gelled pig is preceded and/or followed by other chemical pig segments or mechanical pigs. Such chemical pig segments could be of the same or diferent compositions. For example, the pig train could be formed having an aqueous gelled pig according to the instant invention as the leading segment to remove loose scale and other deris from the pipe followed by a bactericide-containing gelled pig for sanitizing the pipe. Accordingly, this combination would be very effective in cleaning as well as sanitizing pipelines. Segments of the pig train could likewise include fluids (liquids or gases) or non-crosslinked gels containing various additives such as corrosion inhibitors, and the like.
27,974A-F -7-.
"~
~5~2 After the aqueous cross-linked gelled pig has passed through the pipeline, it can be recovered and disposed of as such or "breakers" can be added to the pipeline causing the cross-linked gelled pig to break-up and lose its structure and viscosity. As noted above, this is a very desirable property because it facilitates ; waste disposal. Additionally, in many instances the aqueous gelled pig is of essentially inconsequential volume xelative to the volume of the "product" following it and therefore does not adversely affect the material which follows. For example, a few hundred gallons of a pig used according to the instant invention and dis-charged into the hold of a ship transporting crude oil would not adversely affect the properties of the thou-sands of gallons of crude oil also present in thetanker.
Bactericides which are compatible with water-based formulations are likewise a known class of compounds.
Typically such compounds are aldehydes, organic ~uaternary ammonium compounds or water-soluble salts of halogenated ~particularly chlorinated) phenols. Examples of such bactericides include formaldehyde, gluteraldehyde, dodecyl trlmethyl ammonium chloride, and octadecyl tris (2-hydroxyethyl) ammonium chloride. Bactericides that are effective against sulfate-reducing bacteria are particularly useful in the instant invention because of the serious problems such bacteria can create, particu-larly in oil pipelines. If the particular thickener used is subject to bacterial attack, it may be desirable to also include a bactericide as a preservative for the formulated pig.
The fluid mobility buffer of the invention used for drying the interior surface of a pipe comprises 27,974A-F -3-~"' ~'. ' ~' ' ' ' :.
z - 9 - ~
a non-crosslinked gelled alkanol of from one to three carbon atoms. Preferred alkanols are methanol, ekhanol, and isopropanol. Mixtures of alkanol can be used, if desired. The thickening agent for such alkanols can be 5 galactomannan gums or derivatives thereof but are preferably hydroxy (lower alkyl) celluloses and are more preferably hydroxethyl or hydroxypropyl cellulose.
Such thickeners may be included in the alkanol in substantially any concentration that has the effect of 10 gelling the alkanol and thereby lowering its volatility and enabling the gelled material to be pumped as a viscous slug through the pipeline. Concentrations of from 50 to 20Q pounds of thickener per thousand gallons of alkanol are normally used in making the 15 buffer. Sodium hydroxide or other strong base can also be added to the buffer as a viscosity enhancer.
.
The buffer of the present invention separates the aqueous gelled pig from the liquid alkanol and prevents interfacial mixing of these two components 20 which would destroy or substantially reduce the effec~
t tiveness of each. The gelled alkanol does not appear to cause degradation of the gelled aqueous pig, such as by dehydration, even though the gelled alkanol has the capacity to take up substantial quantities of water as 25 it passes through the pipeline.
The dessicant used for drying the interior surface of a pipe comprises a liquid alkanol of from one to three carbon atoms. Preferred alkanols are methanol, ethanol and ispropanol. The alkanol(s) is 30 used in an amount sufficient to dry the pipeline to the desired degree of dryness, i.e. a dessicating amount.
27,974A-F -9-. , :
It is preferred that the alkanol dessicant and the buffer be the same, but they may be different at the convenience of the user. For example, one would ordinarily prefer to follow gelled methanol with liquid methanol, but it would likewise be satisfactory to follow gelled methanol with ethanol or isopropanol.
It is normally convenient to follow the liquid dessicant with a mechanical swab or with a crosslinked hydrocarbon gel, such as the gelled hydro-carbon pig described in U.S. Patent No. 4,003,393 or anungelled hydrocarbon pig described in U.S. Patent No.
The aqueous gelled crosslinked pigs used in this invention are superior to other pigs which utilize, for example, polyacrylamides and the like for the gel matrix. This superiority is shown in their shear sta-bility, ease of hydration in water, and the convenience with which the gelled pigs are broken when the job is complete. This facilitates waste disposal and enhances the commercial viability.
It has also been discovered that pipelines can be cleaned and simultaneously sanitized by pas~ing an aqueous gelled pig containing at leas-t one bacteri-cide through the interior of a pipeline. By the term, "sanitize" is meant that the bacteria level of the pipe-line surface in contact with the aqueous gelled pig is reduced. Normally, the bacteria level is reduced to essentially zero or some other very low value~
The aqueous gelled pigs of the present inven-tion are easily formulated, are easy to use, and elimi-nate the need for completely filling a pipeline with an ;
27,97~A-F -3- ~
. . .
.
: ~
~ ' , ' , ' ' ' . ' ~ : . ~ ' ' ' ' ~s~
3a-antibacterial solution and thus represent an advance-ment in the art of pipeline cleaning.
The aqueous-based pig compositions comprise water, a galactomannan gum or derivative thereof as a thickening agent, and a crosslinker. The pig composi-tions may optionally contain a bactericide as an addi-tive.
27,974A-F -3a-:, , , , .
s~z Other additives may include an abrasive in solid particu-lat~ form (e.g. sand) to promote the cleaning ability of the pig as it passes through the pipeline, or other conventional additives which stabilize the piy.
Galactomannan gums and derivatives thereof are well known thickeners for water and water-based fluids. Examples of ~uch gums include natural gums (e.g. guar gum, locust bean gum, endosperm seed gums, and the like) and derivatives thereof (e.g. hydroxy-alkyl galactomannans, carboxyalkyl galactomannans, hydroxyalkyl carboxyalkyl galactomannans, and the like). These are known classes of compounds and essentially any member can be used in the present invention. The most common commerically employed galactomannan gums are guar, hydroxypropyl guar, hydroxyethyl guar, hydroxyethyl carboxymethyl guar, and carboxymethyl guar gums. Because -the aforementioned gums are readily commercially available, these gums are preferred thickeners, and of these, guar gum and hydroxy-propyl guar gum are the most preferred. It should be ; noted that;in some references the galactomannan gums are referred to as polysaccharide and polysaccharide derivatives. Any member of this known class of thickening agents can be used in the invention. Such thickeners are normally used in amounks of from 40 to 150 pounds ~ per 1000 gallons of water (i.e. from 0.5 to 1.8 percent ; by wt). They are preferably used in amounts of from 40 ; to 80 pounds per 1000 gallons of water (i.e. from 0.5 to 1.0 percent by wt). The actual amount used, however, can b~ adjusted to convenience by the practitioner.
~ queous compositions containing the abovethickeners are normally cross-lin~ed using a polyvalent 27,974A-F -4-:: .
. .:
:, .
,:
,~ : ~ . " : ~:
~s~z metal ion. The cross-linker is normally added as a soluble salt or as a soluble organometallic compound in an amount sufficient to achieve the desired amount of cross-linking. Borates, organotitanates, and organo-zirconium salts are commonly used. The cross-linking ability of such compounds is pH dependent in many instances (e.g. the borate systems). This factor presents a convenient mechanism for dealing with the thickened fluids in a non-crosslinked form unkil the properties of a cross-linked fluid are desired. In the non-crosslinked state, the thickened aqueous fluids are normally pumpable at conventional pressures. Sub-stantially elevated pressures are required to pump the fluids in the cross-linked state.
The galactomannan gums and cross-linkers are, as noted, known classes of compounds and are disclosed in U.S. Patent Nos. 3,058,909; 3,974,077; 3,818,991;
3,779,914 and 3,696,035. Reference is also made -to the disclosure in the text by Davidson and Sittig, "Water-soluble Resins" Second Edition (1968) and the text by Smith and Montgomery, "The Chemistry of Plant Gums and Mucilages", Biograph Series No. 141 (1959).
Normally, the pig is formulated outside of the pipeline as a pumpable mass and the cross-linker or cross-linker/activator is added to the pumpable mass as it is being pumped into the pipeline. This "on-the-fly"
approach has several procedural adv~ntages, not the least of which is ease of placement at con~enient low pressures~. In this manner, the pig forms a cross-linked gel network after it enters the pipeline and conforms to the general shape and size of the pipeline. To illustrate, an aqueous pig comprised of a borate cross-linked polysaccharide (or polysaccharide derivative) 27,974A-F -5-:
' ~5913Z
gel is a preferred pig composition where the pig may be subjected to considerable shear. Such pig formations are conveniently prepared and used by first blending boric acid (from 2 to 4 pounds) with an aqueous slurry or solution of the polysaccharide or polysaccharide derivativé ~from 60 to 80 pounds) to form a pumpable homogeneous mass. Sufficient base (e.g. aqueous NaOH) is then metered in to change the pH to a basic pH
(pH 8.5-10 normally) as the homogeneous aqueous mass is being pumped into the pipeline. The desired quan-tities of boric acid and polysaccharide or derivative are present per 1000 gallons of water in each instance in the pipeline. The gel-time of these borate-cross-linked systems is easily adjusted by the quantity of base added (cross-linking occurs faster at higher pE values).
After the gelled pig has been formed in the pipeline, it is normally driven through the pipeline by the driving force of a fluid under pressure. This fluid may be a gas or a liquid and will vary depending upon the needs of the user. For example, if the user wishes to leave the pipeline in a dry, empty state, one would normally use a dry inert gas such as, for example, nitrogen, carbon dioxide, ethane, propane, or liquified petroleum gas. If the user desires to refill the pipeline with a liquid product such as, for example, crude oil or gasoline the pig could be driven with the liquid product, so long as the product does not adversely affect the properties of the pig before its purpose was complete or substantially complete in the pipeline.
~0 Normally the pigs are formulated and used at ambient temperatures or below and are pumped through the pipelines at pressures sufficient to move the pig : : .
. , 27,974A-F -6-. ~
:
.
, . , , . '~
-, ~ ...... ",, .
~S~
at a reasonable rate. Temperatures are therefore normally below about 140F. Pressures are normally below about 2000 psig. The predominant number of pipelines will normally be cleaned at pressures less than 500 psig. ~inear flow rates of up to about 5 feet/second are normally satisfactory, from a commercial cleaning standpoint. Rates of from 0.75 to 1.25 ft/sec.
are preferred.
The size and shape of the pipeline is basic-ally irrelevant because the gelled pigs are able to bepumped through the pipe over long distances and their shapes will adjust to fit the size of the pipeline during use. This makes the gelled pig extremely effec-tive because stalactites and stalagmites in the pipeline do not cause its destruction by ripping and tearing it apart as they do solid mechanical pigs.
The aqueous gelled pigs can be used alone or as an element of a pig train in the pipeline cleaning process. In the latter instance, the aqueous gelled pig is preceded and/or followed by other chemical pig segments or mechanical pigs. Such chemical pig segments could be of the same or diferent compositions. For example, the pig train could be formed having an aqueous gelled pig according to the instant invention as the leading segment to remove loose scale and other deris from the pipe followed by a bactericide-containing gelled pig for sanitizing the pipe. Accordingly, this combination would be very effective in cleaning as well as sanitizing pipelines. Segments of the pig train could likewise include fluids (liquids or gases) or non-crosslinked gels containing various additives such as corrosion inhibitors, and the like.
27,974A-F -7-.
"~
~5~2 After the aqueous cross-linked gelled pig has passed through the pipeline, it can be recovered and disposed of as such or "breakers" can be added to the pipeline causing the cross-linked gelled pig to break-up and lose its structure and viscosity. As noted above, this is a very desirable property because it facilitates ; waste disposal. Additionally, in many instances the aqueous gelled pig is of essentially inconsequential volume xelative to the volume of the "product" following it and therefore does not adversely affect the material which follows. For example, a few hundred gallons of a pig used according to the instant invention and dis-charged into the hold of a ship transporting crude oil would not adversely affect the properties of the thou-sands of gallons of crude oil also present in thetanker.
Bactericides which are compatible with water-based formulations are likewise a known class of compounds.
Typically such compounds are aldehydes, organic ~uaternary ammonium compounds or water-soluble salts of halogenated ~particularly chlorinated) phenols. Examples of such bactericides include formaldehyde, gluteraldehyde, dodecyl trlmethyl ammonium chloride, and octadecyl tris (2-hydroxyethyl) ammonium chloride. Bactericides that are effective against sulfate-reducing bacteria are particularly useful in the instant invention because of the serious problems such bacteria can create, particu-larly in oil pipelines. If the particular thickener used is subject to bacterial attack, it may be desirable to also include a bactericide as a preservative for the formulated pig.
The fluid mobility buffer of the invention used for drying the interior surface of a pipe comprises 27,974A-F -3-~"' ~'. ' ~' ' ' ' :.
z - 9 - ~
a non-crosslinked gelled alkanol of from one to three carbon atoms. Preferred alkanols are methanol, ekhanol, and isopropanol. Mixtures of alkanol can be used, if desired. The thickening agent for such alkanols can be 5 galactomannan gums or derivatives thereof but are preferably hydroxy (lower alkyl) celluloses and are more preferably hydroxethyl or hydroxypropyl cellulose.
Such thickeners may be included in the alkanol in substantially any concentration that has the effect of 10 gelling the alkanol and thereby lowering its volatility and enabling the gelled material to be pumped as a viscous slug through the pipeline. Concentrations of from 50 to 20Q pounds of thickener per thousand gallons of alkanol are normally used in making the 15 buffer. Sodium hydroxide or other strong base can also be added to the buffer as a viscosity enhancer.
.
The buffer of the present invention separates the aqueous gelled pig from the liquid alkanol and prevents interfacial mixing of these two components 20 which would destroy or substantially reduce the effec~
t tiveness of each. The gelled alkanol does not appear to cause degradation of the gelled aqueous pig, such as by dehydration, even though the gelled alkanol has the capacity to take up substantial quantities of water as 25 it passes through the pipeline.
The dessicant used for drying the interior surface of a pipe comprises a liquid alkanol of from one to three carbon atoms. Preferred alkanols are methanol, ethanol and ispropanol. The alkanol(s) is 30 used in an amount sufficient to dry the pipeline to the desired degree of dryness, i.e. a dessicating amount.
27,974A-F -9-. , :
It is preferred that the alkanol dessicant and the buffer be the same, but they may be different at the convenience of the user. For example, one would ordinarily prefer to follow gelled methanol with liquid methanol, but it would likewise be satisfactory to follow gelled methanol with ethanol or isopropanol.
It is normally convenient to follow the liquid dessicant with a mechanical swab or with a crosslinked hydrocarbon gel, such as the gelled hydro-carbon pig described in U.S. Patent No. 4,003,393 or anungelled hydrocarbon pig described in U.S. Patent No.
4,152,289, but the use of an inert gas is also operable.
The aqueous cross-linked gelled pig; the buffer, and the dessicant are normally driven through the pipeline by the driving force of a fluid under pressure such as hereinbefore described. If the user desires to refill the pipeline with a liquid product, the "pig train" could be driven with the product so long as thexe was a satisfactoxy interface between the product and the alkanol such that the product did not adversely afect the dessicatiny ability of the alkanol before the job was complete or substantially complete in the pipeline.
The following examples will further illustrate 25 the invention. ~-Example l A 40 mile pipeline was cleaned by passing through it sequentially (a) 2000 gallons of a borate cross-linked aqueous gelled pig (pH 8.5-lO) having lO0 pounds of hydroxypropyl guar per 2000 gallons water, :`
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:. .
~5~
(b) 1000 gallons fresh water, (c) 16,000 gallons of 15 percent hydrochloric acid, (d) 8000 gallons of a com-mercial passivator and neutralizer, and (e) several polyurethane pigs for gas migration control. This train was driven through the pipeline with fresh water pumped at 90 gallons per minute. Samples of the pig were taken as it passed through the pipeline. Data obtained from such samples showed that the gelled aqueous pig retained its integrity throughout the 40 mile journey. An excellent cleaning job resulted from this treatment.
In Example 1 the pig train was driven through ` the pipeline at a rate of approximately 1 foot per second. This is a very satisfactory rate from a com-merical standpoint, but rates up to about 5 feet per second have been used with success. The higher linear velocity trains normally require somewhat longer pigs or pig segments to achieve the same degree bf cleaning (thought to be primarily a function of contact time) and to minimize -the tendency of pig segments to mix if turbulent flow is encountered.
Example 2 The effectiveness of a bactericide~gelled pig was e~aluated by passing ten gallons of an aqueous gelled pig containing 250 ppm of a commercial quaternary ammonium bactercide (Dowell M 76) through a 65 foot test loop of one inch steel and a section of one inch polyvinyl chloride pipeline contaminated with river water laden with bacteria. The gelled pig was~driven through the pipeline with fresh water at approximately six inches~per second. The gel discharged from the pipeline and the pipeline was flushed with approximately 40 gallons of resh water. Samples were taken from the :
27,974A-F -11 :
``` ~.. 4~s~
river water, from the gelled pig, and from the flush water. Culture tests revealed an extremely high level of bacteria of greater than one million bacteria/cubic centimeter in the river water; no bacteria were detected in the gelled pig, and less than 10 bacteria per cubic centimeter were detected in the flush water. The gelled pig was prepared by blending 60 pounds of hydroxy-propyl guar and 3 pounds of boric acid and 250 ppm of the bactericide per thousand gallon~ of water and adjusting the pH of the solution to a pH of from 9-10 with agueous sodium hydroxide. The system cross-linked as the ph became basic.
Example 3 Approximately 60 feet of a l-inch steel pipeline, containing 25 feet of clear polyvinyl chloride sections was filled with water, evacuated with compressed air, and then dried by passing through it the following pig train:
(l) A crosslinked gelled water pig was added first. It was prepared by mixing 12 gallons water, 354 grams of hydroxypropyl-guar, 16.5 g.
boric acid and 350 milliliters of a 5 percent solution of sodium hydroxide in water. The sodium hydroxide was added on-the-fly as the pig was being pumped into the line. The pig crosslinked ; quickly (2-5 seconds) after entering the line to a firm gel.
(2) A gelled methanol pig - prepared by blending 3.5 gal. methanol, l91 g. of hydroxypropyl cellulose (average molecular weight of approximately l million) and 24 g. solid ~odium hydroxide - was then charged.
'.
27,974A-F -12-~, ' " ' ~'. ~
(3) Methanol - 15 gal.
The pig train was then driven through the line at 1-2 feet per second with compressed nitrogen (approximately 231 standard cubic feet used~.
Visual inspection of the line prior to drying showed the walls wet with water and small puddles in low points of the line. After drying with the pig train, the surface walls had a dew po.int of -19F as measured by the Bureau of Mines Dew Point Tester ~manufactured by Chandler Engineering Company~.
; .
:`
~ 27,974A F -13-.
~ -
The aqueous cross-linked gelled pig; the buffer, and the dessicant are normally driven through the pipeline by the driving force of a fluid under pressure such as hereinbefore described. If the user desires to refill the pipeline with a liquid product, the "pig train" could be driven with the product so long as thexe was a satisfactoxy interface between the product and the alkanol such that the product did not adversely afect the dessicatiny ability of the alkanol before the job was complete or substantially complete in the pipeline.
The following examples will further illustrate 25 the invention. ~-Example l A 40 mile pipeline was cleaned by passing through it sequentially (a) 2000 gallons of a borate cross-linked aqueous gelled pig (pH 8.5-lO) having lO0 pounds of hydroxypropyl guar per 2000 gallons water, :`
27,974A-F -lG-.
.,--:
:. .
~5~
(b) 1000 gallons fresh water, (c) 16,000 gallons of 15 percent hydrochloric acid, (d) 8000 gallons of a com-mercial passivator and neutralizer, and (e) several polyurethane pigs for gas migration control. This train was driven through the pipeline with fresh water pumped at 90 gallons per minute. Samples of the pig were taken as it passed through the pipeline. Data obtained from such samples showed that the gelled aqueous pig retained its integrity throughout the 40 mile journey. An excellent cleaning job resulted from this treatment.
In Example 1 the pig train was driven through ` the pipeline at a rate of approximately 1 foot per second. This is a very satisfactory rate from a com-merical standpoint, but rates up to about 5 feet per second have been used with success. The higher linear velocity trains normally require somewhat longer pigs or pig segments to achieve the same degree bf cleaning (thought to be primarily a function of contact time) and to minimize -the tendency of pig segments to mix if turbulent flow is encountered.
Example 2 The effectiveness of a bactericide~gelled pig was e~aluated by passing ten gallons of an aqueous gelled pig containing 250 ppm of a commercial quaternary ammonium bactercide (Dowell M 76) through a 65 foot test loop of one inch steel and a section of one inch polyvinyl chloride pipeline contaminated with river water laden with bacteria. The gelled pig was~driven through the pipeline with fresh water at approximately six inches~per second. The gel discharged from the pipeline and the pipeline was flushed with approximately 40 gallons of resh water. Samples were taken from the :
27,974A-F -11 :
``` ~.. 4~s~
river water, from the gelled pig, and from the flush water. Culture tests revealed an extremely high level of bacteria of greater than one million bacteria/cubic centimeter in the river water; no bacteria were detected in the gelled pig, and less than 10 bacteria per cubic centimeter were detected in the flush water. The gelled pig was prepared by blending 60 pounds of hydroxy-propyl guar and 3 pounds of boric acid and 250 ppm of the bactericide per thousand gallon~ of water and adjusting the pH of the solution to a pH of from 9-10 with agueous sodium hydroxide. The system cross-linked as the ph became basic.
Example 3 Approximately 60 feet of a l-inch steel pipeline, containing 25 feet of clear polyvinyl chloride sections was filled with water, evacuated with compressed air, and then dried by passing through it the following pig train:
(l) A crosslinked gelled water pig was added first. It was prepared by mixing 12 gallons water, 354 grams of hydroxypropyl-guar, 16.5 g.
boric acid and 350 milliliters of a 5 percent solution of sodium hydroxide in water. The sodium hydroxide was added on-the-fly as the pig was being pumped into the line. The pig crosslinked ; quickly (2-5 seconds) after entering the line to a firm gel.
(2) A gelled methanol pig - prepared by blending 3.5 gal. methanol, l91 g. of hydroxypropyl cellulose (average molecular weight of approximately l million) and 24 g. solid ~odium hydroxide - was then charged.
'.
27,974A-F -12-~, ' " ' ~'. ~
(3) Methanol - 15 gal.
The pig train was then driven through the line at 1-2 feet per second with compressed nitrogen (approximately 231 standard cubic feet used~.
Visual inspection of the line prior to drying showed the walls wet with water and small puddles in low points of the line. After drying with the pig train, the surface walls had a dew po.int of -19F as measured by the Bureau of Mines Dew Point Tester ~manufactured by Chandler Engineering Company~.
; .
:`
~ 27,974A F -13-.
~ -
Claims (23)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of cleaning the interior of a pipeline comprising passing through said pipeline an aqueous gelled pig containing an aqueous crosslinked gelled galactomannan gum, or derivative thereof, wherein said gum, or derivative thereof, is present in said gelled pig in an amount of at least about 40 pounds per 1000 gallons of water.
2. The method of Claim 1 wherein said galact-omannan gum, or derivative thereof, is a guar gum or a hydroxypropyl guar gum.
3. The method of Claim 1 wherein said galactomannan gum, or derivative thereof, is crosslinked with borate, organotitanate, or organozirconium ions.
4. The method of Claim 3 wherein said galact-omannan gum, or derivative thereof, is crosslinked with borate ions.
5. The method of Claim 1 wherein said gelled pig comprises hydroxypropyl guar gum in an amount of from 45 to 80 pounds per 1000 gallons of water cross-linked with borate ions and buffered at a pH of from 8.5 to 10.5.
6. The method of Claim 1, including at least one bactericide in said aqueous gelled pig in an amount 27,974A-F -14-sufficient to substantially reduce or eliminate bacteria within said pipeline.
7. The method of claim 6 wherein said bactericide is effective against sulfate reducing bacteria and is selected from aldehydes, organic quaternary ammonium compounds or water soluble salts of halogenated phenols.
8. The method of claim 6 wherein said bactericide is selected from formaldehyde, gluteralaldehyde, dodecyl trimethyl ammonium or octadecyl tris(2-hydroxyethyl)amnonium chloride.
9. A method of cleaning the interior of a pipeline comprising sequentially passing through said pipeline (a) an aqueous crosslinked gelled pig containing an aqueous crosslinked gelled galactomannan gum, or derivative thereof, wherein said gum, or derivative thereof, is present in said gelled pig in an amount of at least about 40 pounds per 1000 gallons of water; (b) a fluid mobility buffer comprising a non-crosslinked gelled alkanol of from one to three carbon atoms, and (c) a dessicating amount of a liquid alkanol of from one to three carbon atoms.
10. The method of claim 9 wherein said gelled pig comprises hydroxypropyl guar gum in an amount of from 45 to 80 pounds per 1000 gallons of water crosslinked with borate ions and buffered at a pH of from 8.5 to 10.5.
11. The method of claim 9, including at least one bactericide in said aqueous gelled pig in an amount sufficient to substantially reduce or eliminate bacteria within said pipeline.
12. The method of claim 9 wherein (b) is an alkanol thickened with hydroxyethyl or hydroxypropyl cellulose.
13. The method of claim 9 or 12 wherein (c) is methanol, ethanol, or isopropanol.
14. The method of claim 9 wherein said alkanol in (b) and (c) is the same in each instance and is methanol, ethanol, or iso-propanol.
15. The method of claim 9 wherein (a) is an aqueous cross-linked gelled pig comprising an aqueous gelled guar gum or hydroxy-propyl guar gum crosslinked with borate, titanate zirconium ions;
(b) is a fluid mobility buffer comprising methanol, ethanol or iso-propanol thickened with hydroxypropyl cellulose, and (c) is methanol, ethanol or isopropanol.
(b) is a fluid mobility buffer comprising methanol, ethanol or iso-propanol thickened with hydroxypropyl cellulose, and (c) is methanol, ethanol or isopropanol.
16. The method of claim 15 wherein (a) is a hydroxypropyl guar gum crosslinked with borate ions, (b) is methanol thickened with hydroxypropyl cellulose and (c) is methanol.
17. The method of claim l wherein said aqueous gelled pig is at least one element of a pig train having a plurality of chemical pig elements.
18. The method of claim 9 wherein said aqueous gelled pig is at least one element of a pig train having a plurality of chemical pig elements.
19. The method of claim 17 or 18 wherein at least the leading element of the said pig train is said aqueous gelled pig.
20. The method of claim 17 or 18 wherein said pig train additionally comprises at least one mechanical pig.
21. The method of claim 17 or 18 wherein at least one of said aqueous gelled pig elements is preceded and/or followed by an aqueous gel or aqueous liquid.
22. The method of claim 17 or 18 wherein at least one of said aqueous gelled pig elements is preceded and/or followed by an uncrosslinked aqueous gel.
23. The method of claim 17 or 18 wherein at least one of said aqueous gelled pig elements is preceded and/or followed by a liquid.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US9610679A | 1979-11-20 | 1979-11-20 | |
| US96,106 | 1979-11-20 | ||
| US10678479A | 1979-12-26 | 1979-12-26 | |
| US106,784 | 1979-12-26 | ||
| US122,536 | 1980-02-19 | ||
| US06/122,536 US4254559A (en) | 1980-02-19 | 1980-02-19 | Method for drying pipelines |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1145902A true CA1145902A (en) | 1983-05-10 |
Family
ID=27378095
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000362839A Expired CA1145902A (en) | 1979-11-20 | 1980-10-21 | Gelled pigs for cleaning and sanitizing pipelines |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0029243B1 (en) |
| CA (1) | CA1145902A (en) |
| DE (1) | DE3070680D1 (en) |
| NO (1) | NO157744C (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4416703A (en) * | 1981-11-20 | 1983-11-22 | Shell Oil Company | System for removing debris from pipelines |
| GB2167078B (en) * | 1984-11-14 | 1988-04-13 | Schlumberger Cie Dowell | Method and composition for the treatment of pipelines |
| DE69013059D1 (en) * | 1989-06-06 | 1994-11-10 | Pumptech Nv | Method and device for temporarily sealing pipelines. |
| GB0113006D0 (en) * | 2001-05-30 | 2001-07-18 | Psl Technology Ltd | Intelligent pig |
| DE10206989A1 (en) | 2002-02-19 | 2003-08-21 | Basf Ag | Production of phthalic anhydride involves gas-phase oxidation of o-xylene or naphthalene in a tubular reactor containing three or more different catalyst beds with controlled hot-spot temperatures |
| CO6170073A1 (en) * | 2008-12-12 | 2010-06-18 | Ecopetrol Sa | ONLINE PROCESS FOR THE PRODUCTION OF AN INTERFACE SEPARATOR GEL AND PIPE CLEANER |
| GB2580986A (en) * | 2019-02-04 | 2020-08-05 | Aubin Ltd | Method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4003393A (en) * | 1973-02-14 | 1977-01-18 | The Dow Chemical Company | Gel-like composition for use as a pig in a pipeline |
| US4216026A (en) * | 1979-02-05 | 1980-08-05 | Shell Oil Company | System for removing fluid and debris from pipelines |
-
1980
- 1980-10-21 CA CA000362839A patent/CA1145902A/en not_active Expired
- 1980-11-17 EP EP80107123A patent/EP0029243B1/en not_active Expired
- 1980-11-17 DE DE8080107123T patent/DE3070680D1/en not_active Expired
- 1980-11-19 NO NO803492A patent/NO157744C/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP0029243A1 (en) | 1981-05-27 |
| NO803492L (en) | 1981-05-21 |
| NO157744B (en) | 1988-02-01 |
| EP0029243B1 (en) | 1985-05-22 |
| NO157744C (en) | 1988-05-11 |
| DE3070680D1 (en) | 1985-06-27 |
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