CA1245997A - Use of flow improvers - Google Patents

Abstract

IMPROVED USE OF FLOW IMPROVERS
Abstract of the Disclosure Friction loss in hydrocarbon fluids flowing through conduits is reduced by adding to said hydrocarbon fluids an effective amount of an ultrahigh-molecular-weight polyolefin having an inherent viscosity of at least 11.0 deciliters per gram, said polymer added to said hydrocarbons in the form of a solution containing less than 10.0 weight percent active material. When added in this form, reduction in friction loss is surprisingly much higher than for similar concentrations of polymer added to the hydrocarbons in a more highly concentrated form.

Description

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IMRE~OVEO USE OF FLOW IMPROVERS
This invention relates to the reduction of frictional pressure loss encountered in the transfer of liqulds by fluid flow through the use of a flow lmprovin~
or drag reducing substance. More specifically~ this invention relates to an improved method of injecting such substances into conduits transferring liquid~ in order to reduce turbulent flow and to increase the effectiveness of ~he flow improver.
It is well known that whe~ a fluid is pumped or otherwise caused to flow throuyh a conduit under pressure, energy is expended as a result o friction, and a rictional pressure los~ xesults Such frictional pressure losse~ are particularly large under turbulent flow conditions/ for example when the ve10c1ty of a liquid passing through a conduit is such that turbulent flow results~ a large frictional pressure loss is encountered. This problem of high rictional pressure 109s or pressure drop in the Elow of liquids through a conduit is commonly e~countered in industrial operati~ns wherein hydrocarbon liquids are conveyed through pipelines at high fluid velocities.
In order *o comperlsate for the frictional pressure loss encountexed from the t~arbulent flow o such hydrocarbon liquidsg considerable energy, generally in the orm of pumping horsepower, must be expended. Thus, reduction of the frictional pressure loss asad the 10w o such hydrocarbon 2S liquids brings about an ~dvantageous reduction of horsepower requirements or alternatively an increased flow rate of a hydrocarbon liquids under the same pumping conditions.
The art ls aware of ~hese problerns as is represented by U.S0 Patent 3~692,676, which discloses a method of reducing friction loss when fluids a pumped through pipelines by adding a high molecular weight poly-alpha-olefin. This patent taught th2t such polymers reduce friction in the flowing liquid by reducing turbulence. A me~hod of measuring performance of these polymers was defined as ~. .
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Drag reduction = ~pressure drop preSsure drop) diesel polymer x 100 .
pressure drop diesel oil U.S Patents 3,~48~266 and 3,75~,406 relate to methods and compo~itions for reducing frictional pressure loss in hydrocarbon flows. Reduction in pressure loss was accomplished by adding a homopolymer SUC}I as a polyisobutyl~ne having an intrinsic viscosity between 2 and 10 deciliters per gram to allow a low total concentration of polymer to hydrocarbon of about 2.5 pounds ~er 1~000 gallons, respectively.
U.S~ Patent 3,351~079 uses drag reducers comprising ethylene~ propylene and butylene terpolymers having a molecular weight up to about 1 million ana useful at concentrations of from 0.01 to about 0.3 weight percent.
U.S. Patent 3,493,000 discloses high molecular weight cis-polyisoprene, cls-polybutadiene and ethylene-propylene copolymers used at concentrations of about 40 paxt~per million. U.S. 3,559,664 relates to the addition of ethylen~ propylene ropolymers to hydrocarbon liquids at level~
of about 300 parts per million by weight.
These references, while not exhaustive of the art in the area, genel^ally represent such art. ~hese references all deal with total concentration of drag reducing ma~erial in polymer and attri~u~e various levels of drag reduction to such to~al concentration of polymersO
Drag reducing polymers currently in use are reputed to be useful at low levels, yet often in practice require hlyher levels in order to sufficiently reduce turbulent flow to a desirable extent. In view of the cost of these polym~rs, as well as the possible contamination effect if used in a finished product pipeline, .it would be greatly advantageous to provide a method whereby such polymers are effective at lower concentrations, or in the alternative, provide much higher levels of drag reduction at equivalent concentrations in the flowing hydrocarhon fluid.
I hava now discovered a method for reducing riction loss in hydrocarbon fluids flowing ~hrough conduits comprising adding to said hydrocarhon fluid an ultrahigh-molecular-weight _3~ ~5~9~

polymer having an inherent viscosity o at lPast 11.0 deciliters per ~ram, said high molecular weight polymer dissolved or suspend d in a hydrocarbon diluen-t, wherein the polymer is present in the diluent at a concentration of less than 10 pexcent by weight, based on the total weight of the diluen~. and the ultrahigh-moleculctr-weight polymer, and is placed into t~te flowing hydrocarbon 1uid such ~hat the total polymer concentration in the flowing hydrocarbon fl-lid ranges from about 0.01 to about 500 parts per million by volume.
It is necessary in the present invention that the ultrahigh-molecular-weight polymer have a inherent viscosity of at least 11.0 deciliters per gram as measured in a low polynuclear aromatic solvent ~LPA) at a temperature of from about 77 ~o about 78F, at a shear rate o 300 reciprocal seconds, and a~ a concentration of 0.10 g/100 ml.
Thus, in the process of the present invention the drag re~ucing mixture wiil contain less than 10 weight percent o an ultrahigh molecular-weight poly- ~ -olefin.
~0 These poly- ~ ~oleins can be homopolymers, copolymers, or terpolymers prepared by con~acting ~ olsins contai.ning from 2 to 30 carbon atoms with a polymerization catalyst.
The catalyst and method of preparing these polymers is not critical other than the .inherent vicosities of the resulting polymers must be greater than 11.0 deciliters per gram at a shear rate o 300 sec 1, and that these materials be substantial.l~
soluble in the hydrocarbon liquid in o.rder to reduce turbulent flow. It is preerred in the practice of the present invention to have a polyltter content of ~rom about 2 to about 6 weight percent at an inherent viscosity o~ from abou-t 12.0 to about 15.0 deciliters per grarn for maximum efectiveness.
The drag reducing polymer, once prepared, is placed in a suitable caxrier substance. These materials are usually inactive hydrocarbon solventsu ~epresenta~ive but non-exhaustive examples of such materials are straight chainaliphatic compounds or branched hydrocarbons such as ethane, :~%~4~997 propane, isobutane, bu~ane, pentane, hexalle, heptane, or isooctane, octane. Also useful are alicyclic hydrocarbons such as cyclohexane, methylcyclopentane, and tetralene.
Aroma~ic hydrocarbons can also be used as represented by benz~ne, toluene, and xylene. Mixtures and analogues of these compounds are also useful as represented by MOLEX
(~rademar~ of Universal Oil Products) raffinate, which is a complex mixture of branched aliphatic, cyclic aliphatic, aromatic and trace amounts of unbranched aliphatic hydrocar~ons.
Likewise useful are low polynuclear aromatic sol~ents~
Further, the hydrocarbon diluent can be an ~ olefin.
I-t should be noted in ~he context of the present invention that when the ~ -olefin drag reducing pol~mer contains significant amounts of lower olefins such as ethylene and butene, a small ~ut significant amount of hydrocarbon~
insoluble material may be producedO This hydrocarbon-insoluble material ~ill be apparent in the diluted ~ixture prepared for injection into the 10wing hydrocarbon liquid, but such materials will dis~olve in the much larger volumes of the flowing hydrocarbon fluid. Therefore? in the context of the present invention, these materia~s may be dissolved or suspendad or a combination of these physical states when injected in~o ~he pipeline. In either case, the term "suspended"
as used in this specifiration and claims will indicate that the polymer can be totally or par~ially dissolved, with any undissolved polymer suspended in ~he hydrocarbon medium.
In any e~ent, once in ~his s~ate, the material is injected into a conduit containing flowing hydrocarbons.
In contxas~ to ma~erials which are produced a~ lower inherent viscosities, or those having hi~h inherent viscosities which are injected at concen~rations of 10% by weight or more, the instant inven~ion shows a surprising increase in drag raduction effectiveness.
The hydrocarbon liquids in which the additive o~ this invention is eEfective include oleayinous or petroliferous liquids as well as emulsions, suspensions, and dispersions thereof. For example crude oil, refined petroleum product~

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such as kerosene, pale oil, diesel oll, fuel oil, asphalt, etc., water-in-oil emulslons, surfactan~s and the like.
Where ~he hydrocar~on liquid is a hydraulic fracturlng fluid, it may also contain solid particulate matter such as sand as a propping agent~ a fluid loss control additive and other materials commonly added to fracturing fluidso In the preferred embodimen~ of ~he present invention the drag reducing polymer is formed rom olefins containing from 5 to 20 carbon atoms which optionally can contain from about 0.01 to about 20% by weight of ethylene or propylene~
and up to 50% butene-l comonomer. Poly~ers so produced will have an inherent viscosity of from about 11.5 to about 15.0 and will be placed in the flowing hydrocarbon fluid at a concentration o~ from about 0.1 to about 3.5% by weight of the diluent or suspending agent.
The invention is more concretely described with reference to the ~xamples below wherein all parts and percentages are hy weight unless otherwise specified. The examples are provided to illustrate the present invention and not t~ limit it.
Example 1 A catalyst slurry was prepared by mixing under an inert atmosphere of dry argon, 0.104 grams of TiC13.A~ (Type lo 1 catalyst frorn Stauffer Chemical Company), 0.36 milliliters (ml) of dried and deoxygenated Molex raffinate ~obtained from Conoco Chemicals; Molex is a trademark of Universal Oil Products)O Thls mixture was stirred for approximately 2 minutes in a dry box. ~i-n-~utylether (60 microliters, dried and degassed) was added. The mixture was then stirred vlgorously for 15 minutes in a small vial equipped with a microstir-bar. This mixture was then transferred to a gas-tight syringe. The vial was washed with 10 milliliters of iow polynuclear aromatic solvent (~A) and the wash material added to the same syringe.
Example 2 The catalyst of example 1 was used in the preparation of a drag reducin~ polymer.

~6~ 5~7 A mixture of 189 ml of dried and deoxygenated low polynuclear aromatic solvent, 3.6 ml of diethylaluminum chloride ~EAC, purchased from Texas Al~yls as a 10% solution in heptane~ and 41 ml of dried and degassed decene-1 was placed into a clean, dry l-~uar~ bottle under an atmosphere of dry argon. Tha mixture was cooled ~o -7~C and agitated in a sha];er bath at 500 revolutions per minute (rpm).
Tha catalyst mixture described in example 1 was added to initiate the polymerization. The mixture became thick. After 3 hours the bottle was removed from the temperature bath. A thermometer was placed into the center of the viscous material, recording a temperature of 6C. The pol~nerization was, therefore, semi-adiabatic due to the insulation effect o the poly(decene-l~ mixture.
Approximately 1.7 ml of methanol was added to deactivate the catalyst. The polymer mixture was stabilized with aboutO.01 weight percent butylated hydroxy toluene (BHT) as an antioxidantO The weight of polymer produced was determined by pouring 84.9 grams o the deactivated polymsr mix~ure in~o 400 ml of isopropyl alcohol with sufficient mixing to precipitate a viscous material containing poly~decene-l). The substance was washed with an additional 400 ml of isopropyl alcohol, filt~red and washed with 400 m~
of metha~ol -to remove catalyst residuP. The poly(decene-l) was collec~ed by vacuum filtration and dried in a vacuum oven overnigh~ t~ produce 4.2075 grams of polymerO The polymer solution thus co~tained 4.95% poly(decene~
This polymer solution was used to determine the inherent viscosity of dissolved polymer. The inherent viscosity 30 ~Fth~was determined in LPA solvent at 77.5 + 0.5F using a Cannon-Ubbelohde four bulb shear dilution ~iscometer at a shear rate of 300 reciprocal seconds.
Example 3 A calibrated Cannon-Ubbelohde Four-~ulb Shear Dilu~ion Viscom~er is used ~o measure the flow time for both solvent and polymer samples. Inherent viscosity values are calcula~ed for each of the four bulbs. These calculated _7~ S~7 values are plotted as a function oE shear rate, and the resulting plot is used to obtain the irlherent viscosity at ~a shear ratP of 300 sec 1 Approximately 0.5 gm of the drag reducer material (for example~ a solution contai~incJ 4.95 weight percent poly~decene-l) in LPA solvent as obtained in Example 2) is p7aced into a clean, dry Exlenmeyer flask equipped with a ground glass stopper. LPA solvent is added to generate a concentration of 0.10 gm polymer/100 ml. The stoppered flask is placed on a ma~netic stirrer and stirred until dissolution is completedO q~he stirrincJ speed is set to minimize shear degradation of the pol~mer. Shear degradation will produce an anomalously low inherent viscosity value.
LPA solvent ~lOml~ is placed into the viscometer, and the viscometer is immersed into a water bath. The system is allowed to equilibrate for at least 20 minutes.
The e~flux time for each ~ulb is determined according to the proceduxa supplied with the viscometer.
The viscometer is cleaned and dried by 1ushin~ with hexane, then with acetone. The efflux ~ime or the ~ample solution i5 measured following the same procedure as used for the LPA solvent~
The inherent visco~ity fQr reach bulb is calculated using the following equationsO
RelatiVe Viscosity (~ rel) = tSoln./tsolven~
t here, soln. = efflux time o the solution tsolvent = eff 1UY~ time of the solvent.
Inherent Vis~ositY ~ nh~ a ln~rel/C r 30 C = concentration in gjdl The shear rate for each bulb is calculated using the relationship. shear Rate (~) ~ K/tSoln where, K - shear rate constant.
~ p~ot of shear rate versus inherent visco~ity is made. The inherent viscosity at a shear rat~ of 300 sec 1 is then determined~

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Examples 4 through 8 The instant inv2ntion was demonstrated in a pipeline.
A polymer solu~ion containing 10.8% poly(decene~1) with an inherent viscosity of 11.8 dlfgm at a ~hear rate of 300 sec 1 was made using a procedure ~imilar ~o Examples 1 and 2.
5 Conditions and quantities were adjusted to yield 10~8%
polymer. Approximately 12 weight percent de~ene-l was charged into th~ pol~meriza~ion vesselO The polymerization was terminé~ with alcohol. The weight percent polym~r content was de~ermined b~ the proc~dure set forth in Example 2.
The inherent viscosity of the dissolved polymer was determined by the four bulb viscometer procedure as dascribed in Example 3.
The 10.8% polymer solution was diluted with LPA to yield a 5.95~ and a 0.94~ polymer solution. A Pfaudler mixer was used to conduct the dilution. The agitator was set at a low mixing speed to prevent shear deterioration of the polymer.
The effectiveness of the drag-reducing materials so produced was te~ted in the Kingfisher pipeline in Oklahoma.
~0 This crude oil pipeline runs from the Kingfisher pump station near Hennessey, Olclahoma, to a ~ank storage area in Orlando, Oklahoma. The inner diameter of the pipeline is 8.24 inches and the total length of 28.3 miles. Drag reducer per~rmance was evaluated in the first 7.4 mile section of the pipeline from the Kingisher pump station. Dual-piston positive clisplacemen~ pumps were used to maintain pipeline flow. The drag reducers wexe injected direc~ly into the 8.~ inch line downstream of the pump at Kingisher. The crude oil fl~w rate during the tests was approximately 1,272 barrels per hour (BPH), which corxesponds to a pipeline flow velocity of 5.3 ft/sec. As a control, a poly~decene-l) solution was prepared containing 6.10% polymer having an inherent viscosity o~ 9.5 dl~ at a shear rate of 300 sec 1 Test results are set forth in Table 1, where examples 4 and 8 are control experiments, and ~xamples 5l 6 and 7 demonstrate the prasent invention.

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Table 1 Weight Inherent Polymer Percent Percen~ Viscosity 1 In~ected into Dra~
Example Polymer (dl/4 ~ n ~ ~eductic~
4 10.8 ~1.9 4.0 33 5.95 11.9 3.1 36 6 0.9~ ~1.9 3~2 39 7 0.9~ 11.9 0.8~ 1~
8 ~.10 9~5 3.1 20 Control example 4 shows that injection of a 10.8 wt~
11.9 inherent viscosity material into the pipeline at approximately 4.0 ppm level o polymer content resulted in 33~ drag reduction in the 7.4-mile section of pipeline.
An 11.9 inherent viscosity material containing 5.95 wt~ polymer and 0. ~4 wt% polymer resulted in much hetter drag reduction perormance. Lesæ polymer was required ~o yield grea~er drag reduction. Surprisingly, the 0.94 wt% material ~exsample 6 j was more effecti~e than the 5.95 wt~ material (example 5).
Examples 9 through 11 A tes~ was carried out in the ~rent pipeline system in the North Sea connecting Conoco's Murchison Platform and Shéll ' s Dunlin-~ platform. This connecting lS pipeling ~egment is 14.7$~inches in diameter ~ID) and 11~74 miles in length and carries crude oil production from ~he Murchison plat~orm. The Murchison crude pxoperties are-API Gravity 3a . 5 Vlsco~ity, Cs 11.3 - 12.4 at 32F
5.4 - 5.8 at /0F
3.5 - 3.7 at 100F
In the5e test~l three materials were employed.
Comparative example 9 used a 10.8 wt~ poly(decene-l) solution with an inherent viscosity of 11.9 dl/~n at a shear rate of 300 sec . ~xample 10 used a 10.~ wt~ material diluted to approxima~ely 3.0 wt3 polymer content in LPA solven~.
~gain, thc dilution was conduc~ed in a Pfaudler mixer under conditions which prevented shear degradation of the polymer.

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The inherent ~iscosity o:E the polymer was 11.9 dl/ym at a ~hear rate o 300 sec 1 Example 11 used a drag reducer which contained approximately 10.5 w~% poly(decene-l~ wi~h an inherent vi~cosity of 9. 5 dl/gm at ~ shear rate of 300 5 sec 1, Compaxative example 11 was al50 conducted using A
dra~ reducer with an inherent viscosity o 90S at a polymer content of 10 5% prior to in~ecting i~to the pipeline. Test results are presented in Table 2 Table 2 Weigh~ Inherent Polymer Pexcent Calculated Percent VisoDsity Injected into Drag Flow 9 10.8 1109 10 19 12 10 3.0 llo~ :~0 50 ~
111~.5 9.5 22 17 11 1~' The test results clearly show th~t performa~ce of the 11 o ~ inhieXE3ilt Vi5C05i ty materizl is greatly enhanced by dilution prior to injection into the pipeline. When comparing Example 9 wi~h Example 10, a flow increase of abou~
~6% was ob~ained usinc3 the diluted material (10~, compared to only a 12~ incxea3e in flow using the concentr~ed dra~
reducer (9). Comparative examples 9 and 11 showed only 12%
and 11% flow in~rease~ respectively. There was a great deal o~ difference in inherent viscosities.
While theoretical in nature/ and I do not wish to

2~ be bound thereby, it is believed ~hat the higher weight con-cen~ration polymer sol~ltions require lvnyer tim2s to go into solution Wi th the ~rude oil. The higher inherent vi~cosity ma~erial, however, provides for bet~er dray reduction if the material is dissslved in the crude oil. This hypothesis is supported by t'he data as eviclenced by comparing example 5 ~ith example 8.

Wl:ile certain embodiments and deta.tls have ~een shown for the purpl~se c~f illus~ratiny this inverltivn, it t`7ill 3:e appar~nt to those ~killed in this ~rt ~hat various ch~nges ancl modification~ may ~e masle herein without d~par~ing 5 from the Spi:rlt or ~cope of the lnv~ntion, , ,

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for reducing friction loss in hydrocarbon fluids flowing through conduits comprising adding to said hydrocarbon fluid a high molecular weight polymer having an inherent viscosity of at least 11.0 deciliters/gram suspended in a hydrocarbon diluent or suspending agent where the polymer is present in the diluent or suspending agent at a concentration of less than 10.0 weight percent when placed into the flowing hydrocarbon fluid and the total polymer concentration in the flowing hydrocarbon fluid ranges from about 0.01 to about 500 parts per million.

2. A method as described in claim 1 wherein the polymer molecular weight as measured by inherent viscosity in low polynuclear aromatic solvents at 77 to 78°F is at least 11.0 at a shear rate of 300 reciprocal seconds and the concentration of polymer prior to insertion is 5.0 weight percent or less of the hydrocarbon diluent or suspending agent.

3. A method as described in claim 2 wherein the polymer is a poly(alpha-olefin).

4. A method as described in claim 3 wherein at least half of the poly(alpha-olefin) polymer is formed from olefins containing from 5 to 20 carbon atoms.

5. A method as described in claim 4 wherein from about 0.01 to about 20% by weight of the poly(alpha-olefin) polymer is formed from ethylene or propylene.

6. A method as described in claim 5 wherein from 1 to about 50% by weight of the poly(alpha-olefin) is formed from butene-1 comonomer.

7. A method as described in claim 5 wherein the polymer placed in the flowing hydrocarbon fluid has an inherent viscosity of from about 11.5 to about 15Ø

8. A method as described in claim 6 wherein the polymer solution or mixture placed in the flowing hydrocarbon fluid has a polymer concentration of from about 0.1 to about 3.5% by weight of the diluent or suspending agent.