The Pipelnne Transportation~CPT6 5 - CJ Lf - / /

of Heavy OilsBy B. L. MOREAU"

(Heavy Oil Seminar, The Petroleum Society of C.I.iU_, Calgary. llIay .5, 196.51

THE PROBLEM

been necessar}r to collect the oil by truck frum in­dividual wells because of the difficulty in even con­solidating the production of a few wells into a centralbattery, as is normally done for lighter oils.

The difficulties can be summarized in one word­viscosi ty.

Figll're 1 shows the viscosity (in Saybolt universalseconds) of some typical Alberta heav}r cL'udes at va~

rious temperatures_ This Figure illustrates somepoints of interest.

I.-Viscosity generally increases as API gravity de­creases.

2,-The viscosit}r of these crudes i!5 very muchgreater than the viscosity of the typical Albel'tnlight crudes we are used to handling.

3.-In the range of flowing temperatures which ' ..... ecan expect in a pipeline, ::;mall differences in tem­perature have a major effed on viscosity,

Fortunately, most of these heavy oils do not hnvea very high pour point. They are not genenllly thixo­tropic; that is, there is not an initial "gel" to over­come in pumping them and the .shearing force re­quired to move them is proportional to the rate ofshear. Thus, pressure gradients can be calculated withthe conventional flow equations. Lloydmin~tel' crude,for instance, has a paul' point of about _8°F.

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Heavy oils tend to be highly viscous. The excessi\"cI)ressure gradients caused b}' high l'iscosity haye discour­aged the del'elopment of heal"y oil pipelines in WesternCanada. This paper reviews briefly and comments on someof the methods used to oyercome this difficult}'.

The crude may be heated to reduce viscosity. Thismethod is well known, and temperature profiles along ahot oil pipeline may be calculated by an equation givenin the paper. There is some difficulty. howHer. in ac­curatel}' predicting heat transfer rates because of un­knowns in soil temperature and conductivity.

Blendinl{ the ,"iscous crude with a diluent to reduce itsyiscosity is probably the simplest method of obtainingpipeline access to interprovincial markets_ If a light dilu­ent such as natural gasoline is used, even small percent­ages grl!atly reduce the viscosit:r. Although there aremethods of estimating the "iscosity of a blend from aknowledge of the vi~cosity of the comlJOnents, laboratorytests on the actual blends to be transported ma.r gin moredependable information.

The addition of water to viscous oil lines is known toreduce pressure gradients. and research on this matter hasbeen conducted by several people. including the AlbertaResearch CounciL This method. however, may have cer­tain operating difficulties and more work on the matte,would he helpful.

The designer of hea".y oil pipelines is advised to givecareful consideration to all the alternati,·es and makedetailed studies lJefore deciding on the method to he used.

The paper outlines briefly some of the design featuresof Husky Pipeline L1d.'s L10ydminster to Hardist)" system.which went into operation late in 1963. This 6%-in. pipe­line, 72 miles long, utilizes three pumping stations tohandle a blend of Lloydminster crude and natural gaso­line_ The pumpage is heated to 130°F at each statloo_A fourth pumpini=!: station at the outlet end (Hardisty)allows pumping in either direction; the renrsal is usedto batch the diluent north to the crude source. where it ishlended with the Lloydminster crude. The blend pumpinglate is 15,000 bbls/day_

ABSTRACT

INTRODUCTION

A LTHOUGH heav)' oil production has existed in\Vestel·n Canada for a number of years, pipeline

movement of this oil is fail"ly recent- Substantial re­serves of proven oil have lacked aggressive develop­ment because their markets have been restricted tolocal requirements. Most of the low-gravity oils havean asphaltic base and consequently are suited to theproduction of paving material. Low-gra,,·ity crude forthe production of paving asphalt has been importedinto Eastern Canada for some time, The restrictionof our local heavy oil production has not been becauseit is unsuitable but because of the difficulty in eco­nomically moving it to market in Eastern Canada,The Lloydminster area along the Alberta-Saskat­chewan border, where oil ,vas discovered in 1938, mayh.n~e at least 50 million barrels of primary recoverablestock tank oil, and considerably more if secondary re­covery methods are effective. This reserve did nothave pipeline access to market until late in 1963.

Most of the production classified as heav.y oil hasbeen trucked to local markets. In Some fields, it has

TENlPERt.TURE DEGREES FAHRENHEIT

-:<-pmject llIanagcr, Jrilliums B1"others Canada Lim­ited, Calgary. Alberta.

Figw'c l.-Fi-scosities oj somc tYJJicarAfbel·ta hcavy cl"Ildcs.

252 The Journal of Canadion Petroleum

DISTANCE (MILESI

Figm'c 2_-TempenJ..tllrc and pressure 'P'l"ojiles tor a typical heated oillinc_

Technology, Oetober~De,enlber, 1965. Montreal

fourth power of the diameter. Thus, the pressuregradient is reduced by raising the average flowingtemperature.

The capacity of a pipeline can be seen to be quitesensitive to pipe diameter.

The main loss of heat from flowing fluids in aburied pipeline takes place by thermal conductionthrough the pipe wall into the surrounding soil andto the atmosphere. If we make certain assumptions, itcan be shown that the temperature at any point alongthe pipeline can be calculated from the equation:

"

rI,

~_.. :.

II.,.

,..- :

.',

(1)

The cooling of the oil along thedirection of flow, and its conse­quent increase in viscosity, resultsin a hydraulic profile which is nota straight line. This is shown inFigure 2 for a typical 6-in. pipelinehandling 15,000 BID of a dilutedLloydminster crude. The curvatureof the line is more. pronounced formore viscous material.

253

The mathematics of evaluatingtemperature and pressure profilesalong a pipeline are tedious, butare well adapted to solution bycomputer (3). It is generally nec­essary to divide the line into shortincrements of 1 to 3 miles and cal­culate these increments separatelyusing average conditions_

temperature of flowing oil, OFground temperature, OFinlet temperature of oil into the pipeline, ofbase of natural logs - dimensionlessover-all heat transfer coefficient, Btu/hr. It2 OFoutside diameter of pipe, inchesdistance from inlet, milesspecific gravity of oilspecific heat of oil, Btu/lb. "Fflow rate, bbls/day

laoo

1600

2000

.0400

1200 ~

~

1000

Bo'

'00

400

20'

0

It should be noted that the distance that the oilwill travel for a given temperature drop is dependentupon the flow rate- It should also be noted that thisequation is for a stabilized flowing condition whichmay take some time to reach.

The terms appearing in Equation 1 can be evalu­ated with accuracy with the exception of "Tb" and"U", which have to do with heat flow from the pipesurface to the surrounding soiL It is known that "Tg "

varies with the seasons. Little reliable data on localground temperatures has been published, but one caninfer certain information from the measured flowingtemperatures of unheated pipelines. One source ofinformation on local conditions is a paper by Bouchel·and Carlisle of Imperial Pipe Line Co. Ltd_ (1). Theover-all heat transfer co-efficient, ··U/' is affectedby the type of soil and its moisture content, and bothof these characteristics may vary over the length ofa pipeline. The best that can be done is to assignaverage values which, from experience, are known to

give representative results. Someguidance may be had from a paperby Fritz Karge (2) which relatesover-all heat transfer to the ther~

mal conductiVity of different soiltypes.

- 3_94 Udo LT ~ T, + (T,-T,)e s<Q

where TT,T,eUdoLScQ

IB 20 22 24 26""",4,

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GROUND TEMPERATURE 3D"F.c,

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This high viscosity has several effects on pipelinedesign:

I.-In the nlost economic size of pipe, the flow will. generally be laminar rather than turbulent_ In the

laminar flow region, pressure drop for a givenpumping rate is directly proportional to viscosity_

2.-High pressure drops pel- mile will be encountered,resulting in fairly close pump station ,spacing.

3.-The viscosity of the oil is too high to get any rea­sonable efficiency from centrifugal pumps-posi­tive displacement pumps are required.

4_-The seasonal variation in ground temperature willhave a marked effect on pipeline flow capacity_ Ifpositive displacement pumps are used we needsome method of adjusting the pumping rates.

These same problems exist in other parts of theworld and the difficulties can be overcome. Heavy oilhas been pipelined in California since early in thecenbu·}r. Some e>...-tremely viscous oil is moved in pipe­line systems in Venezuela and Indonesia_ The diffi­culties in Canada are compounded by our climate andby the fact that our heavy oil production often comesfrom low-productivity wells in small, widely scatteredpools.

The difficulties are therefore more economic thantechnical. In many instances, heavy oils can be movedbJr pipeline more economically than by truck or rail,but one should not expect that normal "rules ofthumb'l for }Jipeline transportation costs will apply.

Various schemes have been used or proposed to re­duce the excessive power consumption required topump highly viscous oiL One of the earliest Was theapplication of heat.

HEATING

An examination of Figu,re 1 shows that viscosityincreases very rapidly with decreasing temperature.For pure Lloydminster crude, a change in averageflowing temperature from 40°F to GO°F reduces theviscosity by a factor of almost 3 to 1. The equationfor laminar flow states that the pressure gradient va­ries directly as the viscosity and inversely as the

... _.. _.. , -- - - ... -_ .. __ _-- -- -

WATEA

It is far better, however, to actually make severaltest blends in the laboratory and to determine theirvi::;cosities experimentally.

Figure 3 shows the viscosity at lOOClF of varyingpercentage blends of Rimbey condensate (a de-butan­ized natural ga.-::olille) wit.h L10ydminster and \Vnin­wright crudes. Both of these crlldes have been blend­ed with the same diluent-note that the curves do notmeet at the same point on the 100-per-cent-condensateaxis.

One should note that even small percentages of thediluent have a marked effect on the viscosity,

The current large pl"oduction of by-products fromnatural gas in Alberta suggetits that this material maybe used to dilute our heavy oils.

As a practical matter, if "'estern Canadian henvycrudes are to attain other than local mal"lmtg, their"i~cosities at flowing pipeline temperatures must beSUL:h that they can be handled by the major eXistingcros:i-(:ountry pipelines.

As the quantities involved are relatively smull,blending ''''ith a lighter diluent is the only practical~cheme for long-distam:e pipeline transportation,

THE ADDITION OF \VATER

The reduction in pressure gradient cau,sed by thl!addition of a less viscous, immiscible liquid to oil hasbeen noted for some time. United State::; patents onlhis method date back to the early 1800's. The AlbertaResearch Council has done considerable work in thisregard, and patents have been issued to Clarl( andShapiro (5) and others.

The resistance to flow in a pipeline is reduced byhaving the viscous liquid at the pipe wall replncedb~' a liquid of much lower vi~cosity, such a.s water.

ThE" maximum pl'e:isure gradient reduction b re­ported to be obtained with a concentrie oil-in-watcl'flow IJattern (6). (see Figlt1·e 4', and methods havebeen proposed to induce thi~ flow paUern-Fiuch OlH

rifling the inlet of the pipe, A reduction in preFiHurcgradient i~ also obtained even if the flow is stratifiedwith the water moving as a la~'er under the oil. Con­siderable information on theoretical studies ancl Ill­boratory tests is available in the literature.

The only pipeline system uf which the author isaware that was designed to operate in this fa~hion

was built in Indonesia for Shell OiL Il move,g an ex­tremeb- viscous nude approximately 100 miles.

The idea of using water to reduce pressure gradientappears attractive because of its simplicity and theexcellent results which theory predicts_ A detailednumerical analysis of the flow patterns ha~ been pub.Iished (7),

There are, howevet', ::;ome points to be consid­ered:I.-Practically all of the published information is

based on small·diameter laboratory test pipelinesor on theory. Unfortunately, bench-scale tests cianot alway:,; check out on commercial installations.

2.-It may be important to ensure that the fluids stayimmiscible. It is sometimes more difficult to pumpemulsions than the pure ViSCOllS e.l'ude.

3.-Ground temperatures in this area drop belowfreezing at the normal pipeline depth of cover,The economics of deeper burial 01' heating thewater would have to be carefully considered_

4_-There is the possibility of patent infringement.5.-There are mechanical problems of separation and

re-injection of the "./ater. if re-pumping is requiredalong the pipeline.

Despite these problems, the scheme is worthy ofserious considenltion.

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PERCENT HEAVY PRODUCT

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1500

55

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FERcENT LIGHT PRODUCT

Figuj'(' ,J.-Yiscosit!l of blends Of Lloydmillstel· alld TVa in­ICrigM cj"1tdt, with Rimbey condensate_

PIPE WALL

...... -.----_ - -.--_ .............. -----_ ----_ .............. ----_ ---_ .

BLENDING

Another wieful method of reducing the pressuregradient in a heavy oil line is to reduce the viscosityb)r blending the heavy oil with a less viscolls material.A number of method:; for predicting the viscosity ofblends of two different materials have been propo~ed_

One can get an approximation by using the standardAST.iVI viscosity temperature charts D-341. The QOF

line may be assumed to represent 100 per cent of thelight component and the lOQoF line to represent 100per cent of the heavy component. A plot of the known'viscosities of the two components at the same tem­perature may be joined by a straight line to show theviscosit.y, at that temperature, of varying proportionsof blend (4).

.- _--_ --- _.. _ __ _. __ .-- ::::::::~::::::::::f"0IL:-:~::::::::~::::::::: --PIPE AXIS......... ---_ _--_ - __ .

...... __ .. - _-.. . -.. -_ ....... _-_ _-_ -_ .

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PIPE WALLf'igrrrc ~.-Coilccnb·ic flow of oil in wate1' to 'redu.ce

press-un: gradients_

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254 The Journal of Canadian Patrolcum

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lNTERPROVINCI:.LPIPELINEHARDISTY

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Figure 5.-Route oj Husky Pipeline Ltd,culations indicated that a 6-ill. pipeline system wouldbe capable of handling the desired traffic, providedthat the pumpage was heated to raise the averageflowing temperatures.

'Vith three pump stations approximatel]r 24 milesapart, discharging the Lloydminster blend at 130'Fand 1.400 psi, the system is capable of a pumping rateof approximately 15.000 B/D. Oil discharged at 130'Ffrom one station reaches the next station at approxi­mately 40°F in the winter. Under summer operatingconditions, heating is not required to maintain 'chepumping rate. Based on the performance of the line.it is estimated that the over-all heat transfer coeffi­cient from oil to ground averages 0.75 Btu/hr. ft' 'F_

The pipeline itself consists of approximately 72miles of 6%-in. by O,ISS-in. API 5LX42 pipe. Thepumping equipment to handle the blend consists ofh\'o axial-flow, screw-type pumps. One pump at ~ach

station is directbr connected to a 300-hp electric mo­tor. The second pump at each station is driven by anelectric motor through a constant-torque, variable­speed Eddy current coupling_ This system allows thepumping rate to be adjusted as required, The pump­ing station at Hardisty, which is used to send con­densate batches north, has two high-pressure plungerpumps with similar drives, The blend is heated ateach station to 130°F in fin-tube heat exchangers, ·~he

heating medium being circulated through exchangersand direct-fired heaters. Each heater is capable of ap­proximately S million Btu/hr_ The crude at Llol'd­minster is delivered partly by tank truck and partlyfrom a field gathering system. All blends are made ina line blending type of operation as required. Theblend received at Hardisty is stored in tankage to betendered to the InterprovinciaJ Pipe Line Company in75,000-barrel tenders at rates of up to 200,000 B/D.The entire pipeline system is equipped with remotesupervisor~r control and telemetering, and can be con­trolled from Lloydminster by one operator.

CHOICE OF METHOD

No hard and fast'rule can be given as to the mosteconomical method for the pipeline tran~portation ofviscous oils. The choice depends upon many ,'al'iables,such as viscosity of the oil, cost and availabilit.y ofdiluent.s amI fuel, soil temperatul"eS and conl1it.iu!l~.

the distance the oil is to be moved, etc.In the case of Husky Pipelines Ltd.'s 72-mile-Iong,

6-inch line from Lloydminster to Hardisty, it was de­cided to blend the crude with a natural gasoline dilu­ent and to heat the stream to 130°F at pumping sta­tions approximately 24 miles apart to reduce the pres­sure gradients.

For a field gathering s:~rstem in the Lone Rock­Lloydminster area of Saskatche'\van, the addition of adiluent and the use of blending facilities at each bat­tery proved to be economic. Additional capacity willbe obtained at a later date by the addition of reheat­ing stations.

The designer of any system to pipeline viscous oilwould be well advised to consider several alternativesand make detailed calculations and economic compari­sons before selecting his final design.

THE HUSKY PIPELINE LTD. SYSTEM

It may be of interest to outline briefl~r some of thedesign features of Alberta's first pipeline project de­!:igned to handle heavy crude oil. V\Then the increasingnatural gas production in Alberta resulted in a con­siderable' quantity of natural gas by-products comingon the market, consideration 'vas given to dilutingLloydminster crude with this material to reduce itsviscosity to a level which could be handled by the ma­jor cross-country pipelines. B~r the spring of 19G3,Husky Oil Canada Ltd., the major producer in theLloydminster area, had conducted sufficient marketingstudies to determine that a blend of Lloydminstercrude and natural gasoline-condensate would be sale­able in Eastern Canada and the United States.

The experience of Interprovincial Pipe Line Com­panJr in moving medium-gravity Fosterton crude tomarket indicated that they could handle a blend ofdiluted Lloydminster crude provided that the viscos­ity characteristics were no 'worse than those of the

'Fosterton crude. Laboratory tests confirmed by theactual operation of a small pilot pipeline system indi­cated that a blend of 22 per cent Rimbey condensateand 78 per cent Lloydminster crude 'would have thedesired characteristics. This blend, slightly less vis­cous than Fosterton crude, has a viscosity of 2,050SSU at 20°F and 720 SSU at 50'F.

Figu.Te 5 shows the route of the pipeline. The sys­tem concept involved receiving batches of condensatefrom the facilities of Interprovincial Pipe Line Com­pany at their Hardisty terminal, transporting the con­densate to Lloydminster, mixing this condensate withLloydminster crude and sending the resultant blendto Hardisty for tender to Interprovincial Pipe LineCompany. The 'Vain,\'right oil field lies on the routebehveen Lloydminster and Hardisty, and it was de­sirable to move the ""Vainwright oil production toLloydminster for use in the local refinery as ""Vain­wright crude is a more suitable feed stock for thelocal operation and is somewhat less desirable forasphalt production in Eastern Canada.

About this time, Husky Oil purchased small refin­eries in the ""Vainwright and LloJrdminster areas.These were shut down and converted to storage ter­minals. The available tankage made it appear rea£on­able to investigate the possibility of batching ship­ments in either direction through one pipeline_ Cal-

.,

Technology, October-December, 1965 r Montreal 255

B. L. Moreau graduated in 1951 with a B.Sc. in petroleumengine.ering from the University of Alberta, Edmonton. Hisexperience includes oil and gas production and reservoir engi­neering with Westcoost Transmission Company Limiled. In1959, he joined Williams Brothers. Canada limited, a Calgary­based consulting firm, os senior design engineer. He is nowproject manager.

(I)

(2)

(3)

(4)

(5)

(6)

REFERENCES

BOllCher, W. IF .. and Carlisle, C., "Soil TemperatureStudies Can Aid in Pipeline Design and Operation,"The Oil & Gas Journal, September 22, 1962, pp. 140,I(urge, Fritz, "Design of Oil Pipelines," The Petr()­[mon Enginee.1·, March, April and 1\.iay, 1945.HOTner, Dennis R., and F-rcid, Paltl, "Computer Pro­gram for a Heated CrudC" Line," Pipeli.ne Industry,November, 1960,Fisher Scientific, "Fisher/Tag Manual for Inspec­tors of Petroleum," 28th Edition, pp. 111.Glm'I.', .4. F., and Shapiro, A., U. S. Patent No. 2,533,­878, }lay 31, 1949.Russell, T. lY. F., and Charles .lI. E., liThe Effect ofthe Less Vi.!)cous Liquid in the Laminar Flow of T ...voImmiscible Liquids," The Canadian JOl~nJ(l1 of C/tclII-

(7)ical E'llgincel'11Ig, 37:18-24, February, 1959.Chu7'les, J1_ E. and Redburgcr, P. J., "The Reductionof Pressure Gradients in Oil Pipelines by the Addi­tion of Water: Numerical Analv.sis of StratifiedFlow," The Canad~'all JOUT1utl of Chemical E"uillcrr­ing, 40:70-75, April, 1962.

Discussion • . •••• • • • • • •

M R. MOREAU's papel", dealingas it does in general terms

with the problems agsociated withthe pipeline movement of heavyoit... touches upon the whole pipe­line transportation picture in thatmany of the problems which heha~ bl"iefl~l dealt with are perti­nent not only to the single or mul­ti-phase flow of gases and liquidsbut to the transportation of all ma­terials-gaseous, liquid or solid.

The crux of any pipeline trans­portation problem is the minimiza­tion of the cost per ton-mile ofproduct moved-assuming that thetechnolog:y is :mfficiently advancedto be able to move the product inthe first place. In the case of veryviscous oils, the choice of technol­ogy is multiple; so that the choice,as 1\o1r. :Moreau has poillted out, isan economic one governed, in turn,b~r geography and the availabilityof materials.

The Research Council of Albertahas had an ac.tive theoretical andexperimental interest in the pipe­line movement of liquids and solidsand mixtures of these in variousforms for sevetal years. Particularemphasis has been placed, boththeoretically Hnd experimentally,on movement by holo-phase liquidflow and solid-liquid flow, and anumber of experiments have beenmade involving two-phase liquidannular flow. The annular liquidus.ed was water in all eases (1). Inone sense, very viscous oils fall in­to the solid-liquid category in thatlarge solid movement in a liquidstream rnajr be regarded, from ananalytical point of vie'....•. as move­ment of a very viscous liquid, i.e.,one ha\ling infinite viscosity. Bent­wich (2) has, in fact. treated the::;tratified flow and conc.entric flowof two immiscible liquids in thisway and has made predictions

256

which agree dosely "'lith the nu­merical analysis of Newton, Red­berger and Ronnd (a). Unfortnn­ately, from the practical point ofview for concentric flow. not onlyshould the specific gravities of thetwo liquids match as closely as pos­sible but the liquids should be in­troduced into the pipeline at theoptimum input ratio in such a wayas to offer minimum 'reorienta­tion' to stable flow. In the labora­torj'. this is easily controlled; inthe field. where mahy other di~­

turbances obtain, it may be diffi­cult. 'Ve have noticed in labora­tory experiments. for example, thatan immiscible core of liquid tendsto become sinuous and that dis­turbances of topography. change inpipe diameter and vibration mayadversel)r affect the flow to thepoint where an emulsion may beformed.

The stratified flov,.', on the otherhand, has only one practical restric­tion-that of keeping the liquidsstratified. In addition, for a givenoil flow rate, the pressure gradientdue to a Vel"y viscous oil flowingby itself in a pipe may be severaltimes that of the same viscous oilflo\'r'ing with water as a stratifiedstream. Charles (4), for example,through laboratory and field ex­periments, noted that a pressurereduction factor exceeding 10 couldbe obtained for ",.'ater contentsranging from 40 to 60 per cent.

Analytical and numerical solu­tions of heat transfel' from buriedpipelines are extremely complex.N at only ma:~,r the physical char­acteristics of the ~urrounding soilchange in space longitudinally andradially around the pipeline butthey may also change in time.Oyer-all heat transfer changes maytherefore be very marked not onlyfor seasonal changes in ground

temperature but also by the effectof the pipe itself on the ground;Le., because the pipe is a heatsource it will change the physicalcharacteristics of the surroundingmedium and, fOl' example, intersti­tial ",rater will migrate outward.Equufiml 1 must therefore be usedwith caution, bearing in mind:(a 1 It is a steadjr-state equation

and unsteady-state conditionsprevail.

(b) 'U' is a complex function oftime and distance and of theother parameterg of Eqllafioll1 .. e.g., if T. is increased, thethermal charHcteristics of thesurrounding medium changeand U, which is dependentupon these, also changes.

In Alberta, whel'e diluents exiBtin the same locale as heav~r crudeoils, this would seem by far thebetter wa,Y of handling the long­distance transportation of thesecrudes-not only from a practicaloperating point of view but alsofrom an economic one. Short di:-l­tances ma}r warrant the use ofheating, and short to intermediatediRtances may warrant the use ofan immisdble liquid (water).

Mr. Moreau has presented auseful general summary of themethods available for the pipelinetl"ansportation of heavy crude oils,and this in turn may perhaps ini­tiate further inveRtigations in thisfield.

REFERI-;NCE:s0) M. E. Charles, G. ll'. Govier llnd

G. IV_ Hodgso-II, Call. J. ChelH.Ellg., :J[}, 27, (1961).

(2) M. Bcntwicli, "Two-phase Flowin a Circular Pipe," InternalRcpt., Aeron. Dept. Imperilll Col­lege, London, (1962).

(3) R. NcwlOJl, P. J. Rcdbcrgcl' llndG. F. ROl/1ul, Ge1.1l . ./. Clum. Ellg.,1,2,168-73 (1963).

(4) .lI. E. Cha1'les, C.I.l\L TrtUl8., titJ,305, (1960).

G. F. ROlmd and G. W. HodgsonResearch Council of Alberta,

Edmonton, Alta.

The Jaurnal af Canadian Petraleum