Journal of the Institute of Petroleum, Vol. 26, No. 204

P- i o i h ic ■

J O U R N A L O F

T H E I N S T I T U T E O F P E T R O L E U M

FOUNDED 1913 IN CO RPO RA TED 1914

V o l . 2 6 O C T O B E R 1940 N o . 2 0 4

C O N T E N T S

P A G E

Control of D rilling M u d in the Field. By H . C. H.

D arley . . . . . . . . 457

Synthesis and Properties of M ono-N orm al-A lkyl- benzenes. P art I. By G . Shen, T . Y. Ju , and

C. E. W ood . . . . . . .

O bituary . . . . . . . .

Abstracts . . . . . . . .

A

Book Review

A

Books Received . . . . . . .

A

Institute N otes . . . . . . . i-iii

Published by The Institute of Petroleum.

Address : c/o The University of Birmingham, Edgbaston, Birmingham, 15.

Printed in Great Britain by Richard Clay and Company, Ltd., Bungay, Suffolk.

A l l rig h ts o f P u b lic a tio n o r T ra n sla tio n a rc R e serv ed . P ric e 7s. 6 d .

T H E I N S T I T U T E O F P E T R O L E U M

C O U N C IL , 1 9 3 9 -4 0

PRESID EN T:

Prof. A . W . N ash, M .Sc.

PAST-PRESID EN TS : A lfred C . Adam s

Lt.-Col. S. J. M. Auld, O.B.E., M .C., D.Sc.

Prof. J. S. S. Brame, C.B.E., F.I.C.

The Rf. Hon. Lord Cadm an, C .C .M .C ., D.Sc., F.R.S.

T. Dew hurst, A.R .C.S.

A . E. Dunsfan, D.Sc., F.I.C.

Sir Thomas H. Holland, K .C .S.I., K.C.I.E., D.Sc., F.R.S.

J. K e w le y , M .A ., F.I.C.

V IC E -P R ES ID E N T S:

A s h le y C a rie r, A.M .I.M ech.E.

C. D ailey, M.I.E.E.

F. H. G arn e r, Ph.D., M .Sc., F.I.C.

M EMBERS O F C O U N C IL :

J. M cConnell San ders, F.I.C.

F. B. Thole, D.Sc., F.I.C.

G . H. Coxon

A . Frank Dabell, M.I.M ech.E.

E. A . Evans, M .I.A.E.

E. B. Evans, Ph.D., M .Sc., F.I.C.

W . E. G o o d a y, A .R .S.M ., D.I.C.

A . C. H artley, O.B.E., F.C.G .I.

Prof. V . C. Illing, M .A . J. S. Jackson, B.Sc., F.I.C.

J. A . O rie l, M .C., M .A.

E. R. R ed grove, Ph.D., B.Sc.

C. A . P. Southw ell, M .C ., B.Sc.

H. C . Tett, B.Sc., D.I.C.

A . Beeb y Thompson, O.B.E.

A . W a d e , D.Sc., A .R .C.S.

W . J. W ilson , F.I.C., A .C .C .I.

C. W . W o o d , F.I.C.

Arthur W . Eastlake, A .M .I.M ech.E., H onorary Secretary

H O N O R A R Y E D IT O R : Dr. A . E. Dunstan H O N O R A R Y A S S O C IA T E E D IT O R : Dr. F. H. G a rn e r H O N O R A R Y T R E A S U R E R : The Rt. Hon. Lord Plender, C.B.E.

S E C R E T A R Y : S. J. A stb u ry, M .A.

[ 3 Vol. 26. • N o . 204. October 1940:

CONTROL OF DRILLIN G MUD IN TH E FIELD.*

B y H . C. H .

B.Sc., A.M .Tnst.Pet. j

In t r o d u c t i o n.

!

Th e

laws governing th e chem ical a n d physical p roperties of m ud are n o t y e t fully know n, a n d m uch research work continues to be done on th e subject. M ost o f us on th e field have little tim e for research an d m u st a p p ly th e resu lts of others to th e p ra c tic a l problem s encountered in handling m ud. This p ap er therefore form ulates no new theory, b u t aim s a t p re se n t­

ing a m eans o f te stin g m uds which will give ra p id an d com parative resu lts, a n d a t establishing from those some system o f tre a tm e n t a n d control.

Fl o w Ch a r a c t e r i s t i c s o f Mu d.

The essential flow characteristics of m ud were clearly d em o n strated by P . H . Jo n es a n d E. C. B abson 1 using a MacMiehael ty p e viscom eter.

W ith this ty p e of viscom eter m u d is ro ta te d a t various speeds in a cup.

A n open-ended cylinder is suspended in th e m u d on a torsion wire. The deflection of th is cylinder gives a m easure o f th e resistance to shear o f th e m u d a t a n y in sta n t.

V ery briefly th e ir re su lts wore as follows :—

I f a th ix o tro p ic m u d is sheared a t a given speed, i t will g rad u ally assum e a deflection ty p ical o f t h a t speed, irrespective o f its previous s ta te of shear. This value is a tta in e d w hen equilibrium is established betw een th e gelling a n d disru p tin g forces. I f a m u d is sheared to equilibrium a t a given speed an d th e r a te o f shear th e n reduced, th e in itia l deflections a t each successive lower ra te o f shear will give a s tra ig h t line w hich will, if projected, c u t th e axis above zero. The slope o f th is line is called by th e se w orkers th e “ im m obility,” a n d th e value a t which i t c u ts th e axis th e “ yield p o in t ” (see Figs. 1 an d 2). Since th e y a re d eterm ined before th ix o tro p y can have a n y effect, im m obility a n d yield p o in t are ty p ical of th e ra te a t w hich th e m u d was originally sheared to equilibrium . To define th e flow characteristics of a m u d , yield p o in t expressed in dynes/cm .2 a n d im m obility in centipoises for several ra te s o f shear a re given.

T he a u th o r m ade some sim ilar b u t m ore app ro x im ate experim ents on drilling m uds ta k e n from A pex W ells. A synchronous m o to r w as used to s tir th e m ud a t a fixed ra te b y driving a paddle in a cup fitte d w ith baffles. Two speeds were ob tain ed through gears. The cup h ad a capil­

la ry tu b e fitte d to th e b o tto m . I n th e first series o f experim ents th e length of tim e required to shear a m ud to its equilibrium v alu e a t each speed was found b y stopping th e paddle every m in u te a n d tim ing th e discharge ra te th rough th e capillary tu b e. The discharge ra te was th e n p lo tte d against length of tim e sheared. Over a n u m b er o f m uds th e tim e required to reach a p p ro x im ate equilibrium w as found to v a ry from 10 m in u tes to m ore th a n h a lf a n hour. E xam ples o f each ty p e are given in Fig. 3.

* P aper read to a m eeting o f the Trinidad Branch on 1st M ay, 1940.

I I

4 5 8 BARLEY . CONTROL OF DRILLING MUD IN THE FIELD .

-P re v io u sly q u i e s c e n t

to

R . P . M

Fig. 2.

D ARLEY : CONTROL OF DRILLING MUD IN THE FIEL D . 4 5 9

I n th e second series of experim ents th e cup was first calibrated a n d a curve draw n to give th e m ean head of discharge ag a in st th e am o u n t d is­

charged. Mud was th e n sheared to its equilibrium value a n d discharged

Fi g. 3.

V A R I A T I O N O F V I S C O S I T Y O F M U D W I T H T I M E O F S H E A R I N G .

continuously in to a g ra d u a te d cylinder. The tim e a t w hich th e level passed

certain in terv als was noted, a n d th u s th e discharge ra te betw een each of

these in terv als could be obtained and p lo tte d ag ain st th e m ean head a t

which it w as discharged. The whole cup seldom to o k more th a n h a lf a

m in u te to discharge, an d th ix o tro p y w as consequently negligible. The

4 6 0 JDARLEY : CONTROL OF DRILLING M UD H i THE FIELD .

m ethod is rough, an d it is necessary to ta k e th e m ean o f a b o u t six se ts of readings to g et reasonably a ccu rate resu lts.

Some ty p ical resu lts are shown in Fig. 4. The slopo of a line is a repre-

F io . 4.

V A R I A T I O N O F R A T E O F D I S C H A R G E O F M U D W I T H H E A D .

DARLEY : CONTROL OF DRILLING MUD IN THE FIELD . 4 6 1

se n ta tio n of th e im m obility. T he p o in t a t which a line cu ts th e axis in d ic a te s th e yield p o in t for th e previous ra te o f shear. I t can be seen th a t a t low ra te s of shear th e curve leaves th e stra ig h t line. This is p ro b ab ly due to plug flow settin g in. T here is, of course, a c tu a lly no sh arp ly defined yield p o in t of a m ud, as has been shown b y o th er in stru m en ts, a n d th e yield p oint referred to th ro u g h o u t th is p ap er is a h y p o th e tic a l value.

I t is clear from th e above t h a t a n y absolute m easurem ent o f th e re sist­

ance to shear of m u d m u st be given in te rm s o f yield p o in t a n d im m obility.

The te rm “ viscosity o f a m u d ,” as u nderstood in com m on oil-field language an d in th e sense in which i t is used th ro u g h o u t th is paper, is u su ally found b y m easuring eith er th e discharge r a te a t co n sta n t head or th e shearing force a t co n stan t ra te . This gives th e to ta l resistance to shear com prising yield point, im m obility, a n d freq u e n tly th ix o tro p y . I t is therefore often highly m isleading, b u t can bo o f value if its lim itatio n s are realized. I f th e m uds are first reduced to .equilibrium a t a n y given ra te o f sh ea r a n d th e viscosity is m easured before th ix o tro p y can have a n y effect, th e re su lts will be com parative for th e r a te o f shear ob tain in g im m ediately before th e m easu rem en t a n d for th e p a rtic u la r in stru m e n t. The results Mill n o t be com parative w ith those obtained from a n o th er ty p e of in stru m en t, nor will th e y give a n y inform ation as to th e behaviour o f th e m uds under oth er ra te s o f shear.

R o u t i n e Ev a l u a t i o n o f Vi s c o s i t y a t t h e W e l l.

This is u su ally obtain ed from a sim ple rugged viscom eter o f th e capillary ty p e. The principal object is to enable th e d rille r to o b tain sonle idea o f th e resistance offered to th e p um ps a n d o f th e a b ility o f th e m u d to carry up cuttings. As th e m u d trav els thro u g h th e well its velocity changes over wide lim its, a n d therefore its viscosity is c o n sta n tly changing. I t is im possible by a n y m eans to arrive a t a figure representing th e to ta l resist­

ance offered b y th e m u d to th e pum ps. A v e ry fair figure is obtained, however, b y m easuring th e viscosity o f th e m ud as i t leaves th e annulus.

This p o in t is chosen for th e following reasons :—

1. The viscosity is highest.

2. The resistance to shear in a n annulus is very high. W ith 3-inch pipe in 6-inch hole R eid an d E vans 2 e stim a te th e resistance in tjie an n u la r space a t a b o u t six tim es th a t of a pipe o f eq u iv alen t d iam eter.

3. The m ud is in stream lin e flow.

4. The m u d has h ad tim e to reach th e equilibrium value for th e ra te of sh ear a t w hich i t is travelling.

I t has been shown t h a t th e single-reading viscom eter gives no inform ation ab o u t th e behaviour o f th e m u d at. a n y ra te o f shear b u t th a t o f m easure­

m ent. I t is therefore obvious, th a t th e viscom eter m u st be so designed

th a t th e velocities th ro u g h th e capillary correspond ap p ro x im ately to

those obtaining in th e annulus. (This m u st o f necessity be approxim ate,

since flow conditions in th e ca p illary tu b e an d th e an n u lu s have n o t y e t

been properly correlated.) F u rth e r, th e sam ple m u st be ta k e n and

m easured in a very sh o rt space o f tim e if th ix o tro p y is n o t to a lte r th e

results. The local I.P .T . viscom eter * does n o t sa tisfacto rily fulfil either of these requirem ents. I t is som ew hat slow in use an d th e velocity through th e orifice appears to be on th e high side. B ecause o f th e la tte r defect it is inclined to give com paratively low readings w ith high gel m uds. The m ost obvious exam ple o f th is is cem ent-cut m uds. A red u ctio n in h ead would rem edy bo th these defects.

I t is useful a t th e w ell to ta k e a viscosity o f th e m u d en terin g th e well a fte r degassing. The difference betw een th e tw o viscosities is a rough m easurem ent o f th e th ix o tro p y .

Ko u t i n e Vi s c o s i t y De t e r m i n a t i o n s i n t h e La b o r a t o r y.

The object of these is m ore to find o u t som ething o f th e properties of th e m ud w ith a view to controlling it, ra th e r th a n th e a c tu a l resistance to shear a t th e well. T here arc tw o opposing facto rs to be considered : tim e and accuracy o f resu lts. I f tim e is no object, a viscom eter like th e Mac- Michael, giving b o th yield p o in t an d im m obility, should unquestionably be used.

F o r quicker resu lts a single-shot in stru m e n t m ay be used, b u t, as pointed o u t previously, th e re su lts are of lim ited value. The m ud m u st first be reduced to equilibrium a t some sta n d a rd ra te o f shear. The m ost suitable ra te o f shear will be a n approxim ation to t h a t u sually prevailing in th e annulus, a n d viscosities th ro u g h th e capillary should be o f th e sam e order.

A suitable viscom eter of th is ty p e is th e capillary cup w ith th e m ud previously stirred b y a m otor-driven paddle. A gear-box w ill allow for tw o speeds, which can be selected b y experim ent to give ra te s o f shear sim ilar to “ ingoing ” a n d “ outgoing ” m ud.

The largest source o f error in th is m eth o d is th e correction for specific g rav ity of th e m ud. To o b ta in com parable re su lts a ll readings m u st be corrected to a sta n d a rd head. This c an n o t be done a cc u rately unless im m obility slopes are known. W ith sim ilar ty p es o f m u d such as m ay be ob tain ed on one field, im m obility slopes m a y differ little enough to allow a single slope to be assum ed, a n d th e correction th e n becomes :—

r = rx + (H — H J ta n . 0

when r is discharge r a te a t head H

r 1 is discharge ra te a t head H x and 0 is th e im m obility.

A n ap proxim ation necessary on account of tim e is th e equilibrium value, th e re being insufficient tim e to shear th e m ud u n til its viscosity is rea lly constant. The m u d m u st therefore be sheared u n til th e ra te of change o f viscosity falls below a certain stan d ard .

I t can be seen from th e above th a t w ith th e lim ited tim e available for routine te s ts viscosity readings m u st rem ain a n approxim ation w ith a lim ited application.

4 6 2 DARLE Y : CONTROL OF DRILLING MTJD IN THE FIELD .

* T h is is a viscom eter of th e Marsh ty p e designed to m eet Trinidad conditions as a result o f discussion betw een interested members o f th e local I.P . Branch.

D A RLEY : CONTROL OF DRILLING M UD IN THE F IE L D . 4 6 3

Cl a s s i f i c a t i o n o f Mu d s.

T he p articles com prising a m ud m ay be divided in to tw o groups : sus­

pensory, i.e., those w hich would suspend them selves i f isolated a n d m ade u p in to a scparato suspension— and suspensoids, which are those th a t w ould n o t. This classification is som ew hat indefinite, because th e ab ility o f p articles to suspend them selves is affected by th e ir concentration.

F u rth e r, th e division betw een suspension a n d deposition is by no m eans sharp, an d tim e m u st alw ays be ta k e n in to account. B u t while th ere is a group o f particles th e classification of which is uncertain, th e g re a t m a jo rity fall clearly into one or o th er o f th e groups.

I f a suspensoid m ud is d ilu ted by tw o or th ree tim es its volum e w ith w ater, th e n th e p articles which are im m ediately deposited are suspensoids.

This analysis is rough, b u t sim ple a n d quick. T he use o f th e te rm su s­

pensoid is perhaps u n fo rtu n ate in view o f th e fa c t th a t m an y w orkers use i t to denote a hydrophobic sol.

T he suspensory group is m ainly composed o f particles o f colloidal dim ensions. These can be classified as hydrophilic or gel-form ing colloids an d hydrophobic colloids. The distinction betw een th e tw o is v ery m arked.

H ydrophilic colloids give a very m uch m ore ra p id rise in viscosity w ith increasing concentration. T hey are also responsible for th e th ix o tro p y , including, of course, th e form ation o f gels. I t is therefore to be expected t h a t th e y w ill have a p redom inating effect on th e m ud, a n d th e proportion an d properties o f those p re se n t are th e m ain facto rs in determ ining its behaviour.

The suspensoid group consists broadly of in e rt p articles of clay, sand, and b ary tes o f dim ensions g re ate r th a n colloidal. T heir effect on th e vis­

cosity o f a suspension is relativ ely sm all, b u t increases w ith th e ir concen­

tra tio n u n til th e y ev en tu ally form a m echanical stru ctu re. The particle size of suspensoids largely determ ines th e ir effect on th e viscosity o f a suspension. (See R eid an d E v an s 2— “ D rilling M ud.” )

The behaviour of a m ud can be controlled b y its com position. The necessary viscosity for th e p rim a ry functions is b est supplied by gel-forming colloids, because of th eir thixotropic n atu re. On th e o th e r h and, too high a concentration is highly undesirable, because o f th e high viscosity involved.

Suspensoids are only desirable in a m ud to supply weight. H ence th e ir specific g rav ity should be as high as possible. The g reater th eir p article size th e less th e ir effect on th e viscosity, b u t p article size is lim ited b y tw o factors. I n th e first place, a balance m u st be stru ck betw een p article size a n d th e concentration o f gel-forming colloids necessary for suspension.

I n th e second place, too large a p article size will cause too m uch abrasion.

Now, i t has been seen th a t th e viscosity o f a m u d is a som ew hat difficult

th in g to determ ine, an d even w hen determ ined i t gives only lim ited in ­

form ation a b o u t th e m ud. I f a simile m ay be used, a high viscosity is

like th e te m p eratu re o f a sick m an : i t shows th a t he is ill, b u t does n o t say

w h at is w rong w ith him . Since th e properties o f a m u d m u st be determ ined

b y its com position, m uch fuller inform ation ab o u t all aspects o f its behaviour

can be obtained from a n analysis. The a u th o r has used a lim ited form of

classification which has given good resu lts w ith th e sim ilar ty p es o f m ud

such as are obtained from one field. In this system unloaded clay m uds are

4 6 4 BA R LEY : CONTROL OF DRILLING M UD IN THE F IE L D .

classified according to th e ratio o f th e viscosity to th e percentage o f solids b y volum e. This ratio is th e essence o f th e classification, because, since th e particle-size d istrib u tio n o f th e suspensoids of th e n o rm al drilling m uds is very m uch th e sam e, i t is a n indication of th e colloidal properties, th e higher th e viscosity for a given am o u n t of solids, th e g reate r th e stre n g th o f th e gel-forming colloids. I t is also held t h a t th e action of th e gel-forming colloids is th e basic facto r in determ ining th e behaviour o f th e m ud. A

Fi g. 5.

sim ple w ay to express resu lts is to select some clay as sta n d a rd an d m easure its viscosity a t various concentrations. The viscosity o f a te s t clay is th e n com pared w ith these, a n d th e co ncentration o f th e sta n d a rd clay required to give th e sam e viscosity as th e te s t clay w ill be a com parison o f th e ir colloidal p roperties. T hus a SO-77 lb./cu. ft. clay m eans a m ud weighing SO lb./cu. ft. th e viscosity o f which is th e sam e as a 77 lb./cu. ft.

m ud o f th e s ta n d a rd clay. Since these tw o figures give a n expression for th e concentration a n d n a tu re o f th e suspension, q u ite a good opinion m ay be form ed o f its behaviour.

I f th e m ud contains b a ry tes it, m u st be an alysed an d considered as tw o

DARLEY : CONTROL OF DRILLING MUD IN TH E F IE L D . 4 6 5

com ponents, th e clay m ud as th e base a n d th e b arytes. T he m ud is first evaporated to dryness a n d th e specific g ra v ity o f th e solids determ ined.

T he to ta l percentage o f solids b y volum e in th e original m u d is th e n c a l­

culated, and from i t an d th e w eight p e r cu. ft. th e clay base can be easily calculated or ob tain ed from a ch a rt. The concentration o f th e clay base being th u s determ ined, i t rem ains to o b ta in a m easure of its colloidal properties. I n a previous experim ent various concentrations o f th e sam e s ta n d a rd clay were loaded w ith various am ounts o f b a ry tes a n d th e viscosity ta k e n in each case. A curve o f viscosity against b ary tes c o n ten t was th e n draw n for each concentration o f th e clay base (Fig. 5). W hen testin g a m ud, its viscosity is found, an d th e am o u n t of b ary tes it contains is obtained from th e above analysis. T he equ iv alen t clay base of th e sta n d a rd clay is th e one w hich gives th e sam e viscosity as th e te s t m u d for th e sam e percentage of b arytes. T he ratio o f th e concentration o f clay base o f th e te s t m u d to th e equ iv alen t sta n d a rd clay base is a com parison o f th eir colloidal properties. The resu lts are expressed as before. T hus a 100- 80-77 lb./cu. ft. m u d m eans a m u d weighing 100 lb./cu. ft. I f a ll th e bary tes were rem oved it would weigh 80 lb./cu. ft. an d would have th e sam e v is­

cosity as a 77 lb./cu. ft. sta n d a rd clay m ud.

The a u th o r has used th is system on daily sam ples from drilling wells w ith satisfacto ry results. The m ain difficulty is th a t, to yield com parative results, th e m uds should all be in th e sam e electro-chem ical condition, w hereas, o f course, th e m uds cam e in from th e wells in varying stages of chem ical tre a tm e n t. T he only w ay to overcom e.this difficulty is to tr e a t th e m u d witli th e u su al reagents an d use th e low est viscosity th a t can be obtained. I n p reparing th e curves, th e sta n d a rd clay was, o f course, sim ilarly tre a te d . W hile th is p ro b a b ly does n o t alw ays give s tric tly com parative figures for th e a c tu a l com position of th e m ud, y e t as a p ractical m eans o f predicting th e behaviour of m uds i t w orks o u t v e ry well.

F o r th e sake o f convenience in draw ing graphs a n d com piling records th e au th o r uses th e ra tio of th e percentage solids in th e eq u iv alen t sta n d a rd clay base to th a t in th e te s t clay base as an indication of th e colloidal properties. This ratio has been called th e “ colloidal in d ex ,” an d th e higher i t is th e higher is th e proportion o f gel-form ing colloids. I t is n o t a very satisfacto ry term , because, if a m ud is d ilu te d a n d te s te d a t various stages o f dilution, its colloidal index changes. This is p rim arily due to th e shape o f th e viscosity-concentration curves.

Since th ix o tro p y also depends m ainly on th e a m o u n t o f th e gel-forming colloids present, it is reasonable to ex p ect some kind o f relationship betw een i t an d th e colloidal index. Fig. 6 shows th e th ix o tro p y a n d colloidal index ta k e n d irectly from th e re su lts o f a nu m b er o f consecutive daily te sts. A n ex act correlation cannot be expected in view o f th e o th er factors involved. The principal one o f these is th e fa c t th a t th e th ix o tro p y w as m easured in a ll stages o f chem ical tre a tm e n t, w hereas th e colloidal index was d eterm ined a fte r th e optim um dose h ad been added.

Fig. 7 shows how th e general level o f th e viscosities a t th e well are

d ep en d en t on th e clay base and th e colloidal index. The viscosity in each

case was ta k e n b y averaging th e viscosities recorded b y th e drillers during

th e 12 hours before a n d a fte r th e sam ple w as ta k e n . The sam ples included

a ll ty p e s of m ud up to ab o u t 105 lb./cu. ft. T he higher w eights can n o t be

4 6 6 DARLEY : CONTROL OF DRILLING MUD IN THE FIELD.

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Colloid '" d c y r - 0//° ,n e q u iv a le n t s t a n d a r d c /a y b a s e

% S o lid s in i e s f m u d d a y b a s e Fi g. 6.

G R A P H S H O W I N G E F F E C T O F T H E C O L L O I D A L P R O P E R T I E S O F T H E C L A Y B A S E O N T H E T H I X O T R O P Y O F A M U D .

Fi g. 7.

G R A P H S H O W I N G T H E E F F E C T O F C L A Y B A S E A N D I T S C O L L O I D A L P R O P E R T I E S O N T H E G E N E R A L L E V E L O F V I S C O S I T Y A T T H E W E L L .

F igures on th e chart are th e colloidal ind ex w hich is

% Solids in th e equivalen t standard clay base

% Solids in th e te st mud clay base L ines represent m ud s of equal colloidal index.

DA R LEY : CONTROL OF DRILLING MOD IN THE F IE L D . 4 0 7

expected to give good correlation, since th e d riller’s viscosities are n o t corrected for specific grav ity . I t can be seen how th e m uds of higher colloidal index give higher viscosities for th e sam e w eight p e r cu. ft. or, m ore clearly, how th e sam e viscosity is given b y m uch higher concentrations of clays of lower colloidal index. Considering th e n u m b er of variables n o t allow ed for, th e correlation is striking, a n d is th e b est p roof th e a u th o r can offer o f th e v alid ity of th is system o f classification.

T he “ in ” viscosity a n d gel stre n g th m u st also depend on th e clay base a n d colloidal index, and i t has been proved by field experience th a t th e ten d en cy to “ gas-cut ” depends on them . I t is also hoped to establish a relationship w ith th e w all-building p roperties.

I t is therefore suggested th a t a fairly com plete p ictu re o f a m u d m ay be gained even by th is ra th e r app ro x im ate system o f analysis, an d th a t a n y asp ect of th e behaviour o f th e m u d m ay be judged from th e re su lts.

E xperience w ith th is system suggests th e feasibility o f control b y a m ore com plete h ydraulic analysis, w ith o u t using d irect viscosity m easurem ents except those ta k e n by th e driller. A fairly ra p id analysis in to tw o or m ore suspensoid groups an d a m ore tru ly colloidal suspension should p resen t no serious p ra c tic a l difficulty. T he concentration a n d viscosity-concen- tra tio n ra tio o f th is suspension would be th e dom inating fa c to r in th e b ehaviour o f th e m ud. W ith m oderately d ilu te colloidal suspensions m ost o f th e difficulties o f viscosity m easurem ents would be rem oved. F ro m th e experience gained w ith th e p resen t system o f analysis i t seems likely th a t th e resu lts would be a tru s tw o rth y basis on w hich to judge th e perform ance o f th e m ud a t th e well, b u t of course m uch d a ta w ould have to be collected to confirm this.

Co n t r o l.

M any articles a n d papers ap p ear on various phases of th e su b ject o f m ud, b u t th e a u th o r has n o t y e t come upon one giving d e tails for a system o f m u d control. Therefore a b rief o utline o f th e m ethod used on tho A pex field is given for w h a t i t is w orth.

D aily sam ples are brought in to th e lab o rato ry from th e drilling wells.

T he viscosity a t speeds corresponding to th e “ in ” a n d “ o u t ” viscosities a t th e well are ta k e n on th e m otor-driven p addle viscom eter as previously described. The effect o f chem ical reagents is trie d a t th e fa s t r a te of ro ta tio n because tho re su lts are obtained m uch quicker. Q uebracho an d caustic soda solution, u sually in tho ra tio 1-6 to TO, is tho m o st com m on reagent. Silicate of soda is som etim es used, an d good re su lts are now being ob tain ed from com pounds containing com plex phosphates. The g ra v ity is d eterm in e d b y hydrom eter, and a rough figure is o b tain ed for san d co n ten t b y dilution a n d settlin g . A figure for gas en train ed in th e m ud is d eterm in ed by ta k in g a fixed volum e in a special d en sity cup, adding a m easured am o u n t o f w ater, shaking up an d allow ing th e gas to escape.

The d en sity cup is again filled w ith th e d ilu ted m u d a n d weighed. F rom

th e p roportion of w a ter added i t can easily be calcu lated w h a t th e original

w eight of th e m u d would have been h a d th e re been no gas in it, an d th e

difference betw een th is an d th e a c tu a l w eight is a n approxim ate m easure

o f tho am o u n t of gas in th e m ud. Tho d ilu te d m u d from th e d ensity cup

is th e n evap o rated rap id ly to dryness an d again weighed. The loss of weight gives th e volum e o f w a ter an d by difference th e volum e o f th e solids, an d hence th e ir specific grav ity . F rom th ese re su lts th e clay base a n d th e colloidal index are ascertain ed . A ll resu lts are recorded an d a daily graph is k e p t o f th e m ore im p o rta n t factors, including th e re su lts obtained a t th e well.

The d riller is provided w ith th e local I.P .T . viscom eter an d a m ud scale.

H e tak es readings a t fre q u en t in terv als. W henever th e viscosity rises above a given figure he adds a “ dose ” to th e m ud. T his is re p e a te d when th e viscosity rises again. T his “ dose ” is fixed on th e re su lts o f th e lab o rato ry te s ts described above an d is changed from tim e to tim e as con­

ditions change. I t u su ally consists o f a s ta te d am o u n t of chem ical reagent a n d w ater. The w ater is m easured in b y m oans o f a sim ple constant- head m eter discharging th rough interchangeable chokes. The “ dose ” is added over th o period of one circulation.

T he “ dose ” is determ ined as follows : I n norm al circum stances th e optim um am o u n t o f chem ical reag en t is p u t in w ith each dose. This am o u n t is judged from th e lab o rato ry te s t a n d p a s t experience. I f su b ­ sequent te s ts show th e a m ount too m uch or to o little , i t is ad ju ste d accord­

ingly. The am o u n t of w ate r depends en tirely on th e clay base a n d w hether i t is desirable to allow i t to rise or to fall.

The general aim is to allow' th e base to rise as m uch as possible, in order to save b arytes. Much m ore d a ta need to be collected before i t can bo decided to W'hat lim it it is econom ical to allow th e base to rise. I t m u st obviously depend largely on th e drilling conditions an d th e n a tu re of th e clay base. A t th e m om ent, lower bases are held for m uds o f high colloidal indices because of th e higher “ o u t ” viscosities (see Fig. 7) an d th e g reater tendency to gas-cut.

Careful control o f th e clay base has been found to yield considerable economies in th e use o f b ary tes. This is believed to be duo to th e fa c t t h a t high viscosities are avoided. As soon as th e viscosity rises above a given figure, th e driller tre a ts th e m ud. Clay-base control m erely rep re­

sen ts a system w hereby th e m inim um am o u n t o f w a te r is used to keep w ithin th e desired range o f viscosities. Low viscosities are economical because w ith th em less solids are picked up a n d dispersed th rough the m u d and, m ore im p o rtan t, th ere is less tendency to gas-cut. (This does n o t ta k e in to account th e m any ad v an tag es o f low viscosity to th e driller.

T h a t viscosity can very m aterially affect th e speed o f drilling, especially in deep holes, has been proved several tim es on th e A pex field.) T h a t low viscosities are econom ical in b ary tes consum ption is shown in Fig. 8, w'hich gives th e b ary tes used to m ain ta in w eight in wells before an d a fte r th e policy u'as intro d u ced in full on th e A pex field.

4 6 8 d a r l e y : c o n t r o l o f d r i l l i n g m u d i n t h e f i e l d .

Bl o w-o u t s a n d Ga s-c u t t i n g.

The connection betw een blow -outs an d g as-cutting is a p o in t which needs

em phasizing. W ith m ost blow -outs i t can be shown t h a t th e reservoir

pressure did n o t exceed th a t of th e h y d ro sta tic h ead o f m u d o f th e g ra v ity

th a t was being m aintained, o r even th a t of w ater. Therefore th e blow -out

D A RLEY : CONTROL OF DRILLIN G M UD IN THE F IE L D . 4 6 9

m u st have been preceded b y gas-cutting, w ith o u t which i t w ould n o t have occurred. Such g as-cu ttin g can ta k e place m erely from th e gas in th e san d c u t b y th e b it. Also i t m u st be rem em bered t h a t gas w ill te n d to

We//s in chronoiog/cai o rd e r

Fig. 8.

D I A G R A M M A T I C R E P R E S E N T A T I O N O F T H E A M O U N T O F B A R Y T E S U S E D T O M A I N T A I N W E I G H T I N I N D I V I D U A L W E L L S .

seep in to th e m u d from sands alread y p e n e tra te d , because o f th e difference

in specific g ra v ity betw een i t a n d th e m ud. This w ill n o t be controlled

b y th e difference in pressure betw een th e gas a n d m u d colum n, b u t by

th e form ation an d m aintenance o f a good m u d sh eath on th e face o f the sand. I t is significant th a t blow -outs often occur a long tim e a fter th e sand has been p en etrated , an d freq u en tly w hen o u t of th e hole w hen condi­

tions for g as-cu ttin g are optim um .

I t is by no m eans contended th a t g as-cutting is th e sole cause o f blow­

outs, b u t m erely th a t i t is a n im p o rta n t facto r in m any. D rilling technique should therefore ta k e i t in to account, a n d below are given some suggestions as to jjvhat steps should be ta k en . I n th e first place, some m eans m ig h t be devised w hereby th e driller would o b tain a rough figure for th e am o u n t o f gas in th e m ud. I f a sharp increase o f gas is observed, he is forew arned.

The addition o f b ary te s is n o t a v ery good rem edy. I t increases th e m argin o f safety, b u t i t also increases th e viscosity, a n d hence th e ten d en cy to gas-cut, a n d a vicious circle is a p t to be established. I t should be used only as a la s t resource. E v ery effort should be m ade to reduce th e am o u n t of th e gas in th e m ud b y lowering th e viscosity an d degassing. I t is u n ­ fo rtu n a te th a t th ere appears to be no really efficient ty p e o f m ud degasser available, a n d some research on th is subject should be am ply repaid. The m ost dangerous period is w hen th e pipe is o u t of th e hole. Before pulling o u t, th e m u d should be conditioned an d th e gas rem oved. Care should be ta k e n to see t h a t no fresh gas is entering th e m ud. A th in m u d will g re a tly reduce th e sw abbing effect w hen pulling out. The above sugges­

tions m ay be ra th e r vague, b u t w ork along these lines should lead to th e developm ent of a sounder technique, an d consequent decrease in th e nu m b er of blow-outs.

Co n c l u s i o n s.

T he system o f control o utlined in th is p ap er is based on various assum p­

tio n s a n d approxim ations th e v a lid ity of w hich is open to question. This is inevitable in a n y p ractical system u n til our knowledge of m u d increases.

The m ain thing is to establish te sts w hich are as com parative as possible and to keep fu 11 records of th em an d th e resu lts obtained. F rom these records inform ation is gained a n d th e system g rad u ally im proved. This, th e a u th o r can say from experience, is n o t m erely o f th eo retical in terest, b u t yields definite p ra c tic a l results.

The value o f good m u d control is only now being fu lly realized. I t is n o t m erely a question o f saving b ary tes, b u t o f preventing blow-outs, and o f preventing dam age to producing sands b y w ater in filtra tio n ; w ith deep holes i t often m eans th e difference betw een m aking hole or n o t m aking hole, or, w ith heaving shale, of m aking hole or losing it. There are m an y problem s connected w ith th ese p o in ts to be solved, and tim e a n d m oney sp e n t on th e m should be am p ly repaid.

The a u th o r’s th a n k s are due to Messrs. Apex (Trinidad) Oilfields, L td ., for perm ission to publish th is paper, a n d to Mr. G. H . S cott for freq u en t help an d advice.

Bibliography.

1 “ E valu ation of R o ta ry Drilling M ud,” by P. H . Jon es and E . C. B abson, Oil W eekly, 2 . 1 2 . 3 5 .

2 “ D rilling M ud,” Trans. M in . and Geol. In st, o f In d ia , Vol. x x x i i . 4 7 0 PA R LEY : CONTROL OF DRILLING MUD IN THE F IE L D .

DISCUSSION ON CONTROL OF DRILLING MUD IN THE FIELD. 4 7 1

D IS C U S S IO N .

T h e C h a i r m a n (Mr. L. A . B u s h e (Apex)), congratulating Mr. Darloy on a very

interesting and valuablo paper, said th a t apart from tHo scientific asp ect of m ud treatm ent there were several qu estions of a practical nature he would like to ask members to d eal w ith during th e discussion : H ow m any fields were usin g th e local I.P .T . viscom eter as their standard fieldm easuro o f v isco sity ? W hat lim its o f v isc o sity were allow ed on th e field ? W hat percentage of sand w as allow ed in th e m ud s, and were do-sanders used to an y ex te n t ? W hat ty p es of m ud dogassors woro used ?

Mr. Busho also asked speakers to give som e indication as to w h eth er th ey th ou gh t it w as worth w hile continuing w ith th ese m eetings while th e war w as on, as th e y w ould n ote th a t v ery few members of th e In stitu te woro present th a t evening, and th e C om m ittee w as n o t sure th a t it m ight n o t perhaps be botter to lot th e local Branch lie dorm ant u n til such tim o as there w as n o t such a prossuro of w ork th a t it m ade the obtaining of papers a lm ost a n im possibility.

T he Chairman th en declared Mr. B a rley ’s paper open for discussion.

M r . G. H . S c o t t (Apex) w ished to add h is congratulation s to th ose of Mr. Busho.

T he paper w as, to his m ind, one of th e first th a t had actu ally tried to strike a balance betw een th e pu rely scientific asp ect of m ud and the practical side. I n th is work Mr. D arley m u st be given all credit for havin g arrived a t a basis for m ud treatm ent w hich, although ad m itted ly purely applicable to local conditions, did corrolato the v isco sity of th e m ud a s m easured b y th e driller in th e field w ith th e laboratory performance.

W ith reference to th e caso o f ccm ent-cut m uds, tho I.P .T . viscom eter, o w in g to it s rather considerable head, gave a very high rate of shear through tho orifieo; only a few days ago ho had a case where th o I.P .T . viscom eter w as only 22 seconds, b u t th e th ixotrop y w as so high th a t th e m ud w ou ld n o t even flow through th e laboratory viscom eter after shearing.

H e w ou ld ask tho auth or to enlarge on tho im portance of th e colloidal in d ex w hen w ish in g to got Schlumberger p lu m m ets to b ottom or w h en running casing.

Mr. S c o tt referred to th e question of variation in th e size of hole. I f one had changes in th e size of th e hole th ere w as alw ays tho danger, especially in a deep hole, th a t tho largo hole above th e p ilot hole w ould u ltim a tely build up to tho diam oter o f tho p ilot hole. H e believed Mr. D arley could give som e actual cases of th is.

A s th e auth or had poin ted ou t, his use of th e term “ suspensoid ” w as perhaps a little un fortu nate; “ su sp e n so id ” a s used in puro colloidal ch em istry w as rather lim ited to tho hydrophobic typo of sol. H o could th in k of no other term for particles w hich, a lth ough larger than colloidal dim ensions, were held in su sp en sion by th e nature o f tho dispersive base and by their concentration.

W ith regard to th e qu estion of gas-cu tting and blow -ou ts, Mr. S co tt poin ted ou t th a t th e m od em tendency to “ slim ” holes tended to aggravato tho danger un less rigid m ud control w as observed. In m an y cases tho in terstitial gas in th e sand a ctu a lly excavated b y the b it w as sufficient to cause ex ten siv e gas-cutting. F urther­

more, tho tendency to sw ab a hole w h en pu llin g o u t w as increased as hole diam eters decreased, and it w as o f prim e im portance to condition th e m ud and secure a low v isc o sity prior to a “ round trip .”

M r . D a r l e y , replying, said th a t w ith regard to tho colloidal ind ex w h en running

Schlumberger plu m m ets, it w as a poin t th a t had to bo taken very m uch into account.

I f y o u had a m ud yieldin g qu ite a good v isc o sity a t th e w ell bu t havin g a high colloidal ind ex, it w as going to gol fast, and b y th e tim e th e Schlumberger p lu m m et g o t dow n it m ight be thick enough to preven t it reaching b ottom . H e had n o t done m any experim ents in th is direction, b u t generally foun d th a t agen ts su ch as quebracho w ould roduce v isco sity b u t did n o t groatly affect th o rate a t w hich th e m ud gelled.

T he o n ly solu tion , h e th ou gh t, w as to dilu te th e m ud down.

On th e poin t of difforent sizes of hole, he th o u g h t perhaps tho w orst case w as w hen cavities duo to cavin g woro obtained, resultin g in changes of v elo city w hich caused tho deposition of cuttings.

4 7 2 DISCUSSION ON CONTROL OF DRILLING MUD IN THE FIELD .

Mr. G. S. Taitt (U nited B ritish Oilfields of Trinidad) said he w as interested in the Chairman’s remarks w ith regard to tho hold in g of m eetin gs of th e Branch. T his w as th e first tim e ho had had tho op p ortu nity o f a tten d in g one him self, b u t ho felt it w ou ld be a great p ity if tho m eetin gs had to be given up, th ou gh ho quito realized th e difficulties under present conditions. H o su ggested it w ou ld bo bettor to have an occasional paper— sa y onco in one or tw o m onths— rather th an close dow n tho Branch altogether, becauso there w as alw ays a certain am oun t of in itiative available.

H e th o u g h t Mr. D arley w as to bo congratulated on th o sy stem a tic w a y in w hich he had d ealt w ith h is particular m ud problem s.

I n th o first part of tho paper, dealing w ith flow characteristics of m u d , several references were mado to tho p ossib ility of discounting tho effect of th ixotrop y e.g., in m easuring v iscosities after a n interval of n o t m ore th a n half a m inute. H ow ever, th e speaker had had som e experience of m u d s gelling alm ost instan taneously, which had preven ted th e obtaining of accurato v iscosities and com parative figures, so th a t ho fe lt it could n o t bo com pletely neglected . H e did n o t know if Mr. D arloy had com o across such conditions.

' H e th ou gh t th e im portance of th ixotrop y had n o t perhaps been stressed enough in th e papor, because oven w ith m ud which sh ow ed a very good condition w hilo circulating, its th ixotrop y w as o f great im p ortan ce; for exam ple, if th e pu m p s woro sh u t dow n, oven for a sh ort tim e, w h en starting up again high initial pressuro duo to gelling m igh t causo com plete loss of circulation.

On th e question of th e colloidal indox, te s ts m igh t bo m ado b y preparing standard m u d s; b u t had Mr. Darloy noticed th e change w h ich took place after a period of circulation w ith a given m ud ? T hey had observed th a t w ith som e m u d s th o clay contont appeared quito satisfactory a t tho beginning, b u t after a whilo, p ossib ly duo to crushing or grinding of clay particles, tho colloidal content appeared to have gone up.

I n connection w ith th o degassing of m ud s, had Mr. D arley had exporionco of v acuum degassifying ?

W ith regard to plastoring, Mr. D arley hod sta ted in h is paper : “ A lso it m u st be romembered th a t gas w ill ten d to seep in to th e m u d from sands already penetrated because of tho difference in specific gravity betw een it and th o m ud. T h is w ill n o t be controlled b y th o difference in pressure betw een tho gas and m ud colum n b u t by th e form ation and m aintenance o f a good m ud sh eath o n th e face o f th e san d .”

Som e experim en ts had been m ado w hich tended to su ggest th a t tho pressuro required to deplastor w as vory low indeed w ith a good m ud, and thereforo ho wondered w h y Mr. Darloy attach ed su ch im portance to th e nature of tho m ud sh eath for holding b ack gas.

M r . D a r l e v , replying on tho qu estion o f m uds settin g in sta n tly due to th ixotrop y,

said th a t ho had, of course, had experience of such a condition. H is actu al remark had been mado in connection w ith his te s ts o f th e rate of discharge a gain st head.

H e w as m erely tryin g to establish th e relationship and got som e valu es for th e A p ex field. T he m u d s used woro all fairly th in m ud s, gelling effect w as slig h t, and th e actual m otion through tho viscom eter w as quito sufficient to preven t tho th ix o tro p y from havin g a n y effect. H e quito agreed th a t w ith v ery th ick m u d s of high th ix o tro p y , viscom eter readings w ere a p t to bo vory seriously up set.

Tho change in v isc o sity duo to circulation w as v e ry readily understandable. Tho p oin t w as w ell illustrated b y th e difficulty in obtaining a c o n sta n t v isc o sity w h en m ak ­ ing up a m ud from th e raw clay. H is ow n stan dard m u d s were m ixed b y placing in a concrete m ixer and rotatin g for a d ay, and evon th en, o n p u ttin g th em in th e v isco ­ m eter and rotatin g he could still g et a rise in v isc o sity over a period o f tim e. T his w as un dou btedly duo to tho particles of th e cla y becom ing more and m ore dispersed and becom ing finer; their surface area w as increased and colloidal properties camo m ore and m ore into p lay.

W ith regal'd to vacuum degassing, h e had no field experience, b u t h ad tried it in a sm all w ay in th e laboratory, ju st hold in g a sm all v acu u m of a few inches. Tho difference he h ad obtained w as p ractically negligible.

W ith regard to plastering, h is answ er to th e qu estion w hether gas could seep into th e m ud a gainst a higher head if there w as n o t a m ud sh eath , w as em phatically yes.

Gas w ou ld tend to rise pu rely because it w as ligh ter th an th e m ud. I f one had a

DISCUSSION ON CONTROL OF DRILLING MUD IN THE FIE L D . 4 7 3 closed g lass tube w ith m ud in i t and an air space a t th e to p , and th e tu b e w as reversed end for ond, tho air bubble w ou ld go back to tho top. T he fu n ction o f th e m ud sh eath w as th a t of a m embrane to preven t th a t action. H o had done no experim en ts on tho force necessary to romovo th e m ud sh eath , b u t th is m u st ob viou sly bo dependent o n tho difference betw een tho reservoir pressure and th e pressuro of tho m ud colum n.

T h a t w as whero loading of tho m u d w as of value.

Mr. Taitt explained th a t he realized tho n ecessity for som e m ud sh eath (which, ho assum ed, w ould bo present in any case), b u t ho wondered if Mr. D arley h a d n oticed an y difference w ith m uds of different plastering qualitios.

Mr. Darley replied th a t ho had no com parisons from w hich conclusions could be reached.

Mr. N . Hea ley (U nited B ritish Oilfields o f Trinidad), spoaking on tho qu estion of gas entering m ud, said th a t w hen a sand had been drilled, if th e h yd rostatic head of tho m ud w as higher th a n tho reservoir pressure, laboratory experience show ed th a t th e absorptive effoct w ou ld givo rise to gas-cutting, oven th ou gh there w as a far greater pressuro duo to tho m ud th an to tho reservoir.

H o also raised tho p oin t ab ou t th e abrasivonoss of particles in m ud and particle sizo. H e believed particlo sizes had v ery little to do w ith abrasive action and it w as m uch moro due to particlo shape. I f y o u had sand particles w hich w ere perfectly rounded, thoro w ou ld be very littlo abrasive action indeod, b u t if th e y had sharp corners, e v en if o f vory sm all size, thoy w ould h a v e considerable abrasivo action.

L aboratory experim en ts could be done w ith particles of different kinds.

Mr. Darley agreed th a t sh ape m u st have a very great deal to do w ith it, b u t, g iv en tho sam e shaped particles, tho larger particlos w ould give deeper scratches, smallor ones havin g moro of a polish in g effect.

Mr. Hea l e y su ggested , w ith regard to th e colloidal ind ex, th a t if a stan dard m ud cou ld bo prepared— w hich w as ad m itted ly difficult— and som e am oun t o f standard cla y and w ater p u t in and ground for som e definite tim e, taking som e standard clay such as Aquagol in stead of local Trinidad clay, th e n perhaps ono could got an alm ost universal standard m ud, w h ich w ou ld help in com paring m ud s in different countries.

Mr. Da r ley th o u g h t th a t th is w ou ld bo a v ery usefu l th in g for com paring results betw een ono field and another.

Mr. Scott remarked th a t b enton ites were so liable to variation th a t ho did n o t th in k A quagel could bo tru sted any m ore th a n clay a s a standard.

Mr. Da rl e y sta ted th a t he had had sam p les o f ben ton ites which had com pletely lo st their gelling qualities m erely w ith age. Thoreforo ho did n ot th in k su ch a sensitive clay w ou ld bo suitablo for preparing a standard m ud.

Mr. He a l e y m entioned tho difficulty in correlating results on th e rig w ith th ose obtained in th e laboratory. W ith regard to v iscosity, an even b etter criterion w ould bo to tak e th e pum p pressure and rate of circulation. I f there w as stream line flow in th e ann ulus, th e law s of v iscosity should app ly, and from th a t it should bo possible to g e t som e idea of tho visco sity . I t w ould th en rem ain to correlate th is w ith tho laboratory v iscosity.

M r. D a r l e y pointed ou t th a t tho troublo w ou ld be to standardize conditions.

Thoro were so m any other im portant factors— e.g., if a change w as m ade from 4-inch to 2-inch drilling pipe, th e pu m p pressures w ou ld alm ost double them selves.

D r . A. J . G oodm an (Cory B ros.) m entioned a m ud degasscr w h ich he had seen in th e Oil Weelcly ab ou t tw o m o n th s previou sly.

K K

DISCUSSION ON CONTROL OF DRILLING MUD IN THE F IE L D .

M r. D a r l e y said ho h ad recently com e across ono w hich had a vacuum a t th e top and baffles to increase th o area exposed to th e vacuum . H e had n ot used anyth in g

sim ilar to th a t. J h

Mr. Bustie said th a t th e Com m ittee hoped to have another paper late in June.

I f a n y m ember had a particular urge to read a paper before th e Branch and would w rite to th e Secretary, th e y w ould see w h at could be done abou t it

I n conclusion he proposed a v o te of than ks to Mr. D arley for his paper, and also to tho A p ex Club for tho uso o f their Clubroom.

S Y N T H E S I S A N D P R O P E R T I E S O F M ONO- N O R M A L - A L K Y L B E N Z E N E S .*

P A R T I .— M ETH O D S F O R T H E A L K Y L A T IO N OF B E N Z E N E .

B y G. S h e n , M.Sc., A .M .In st.P et., T. Y. J u , B .Sc., S tu d .In s t.P e t., a n d C. E .

M.Sc., A .I.C ., F .In s t.P e t.

Sy n o p s is.

Tho principal available m othoda for preparing alk yl (long-straight chain) benzenes aro review ed critically. Seven m eth od s aro considered in detail—

nam ely, (1) F ittig ’s sy n th esis; (2) condensation of alk y l halides w ith benzene; (3) condensation o f d efin es w ith benzene; (4) condensation of alcohols w ith b en zen e; (5) interaction of inorganic and organic esters w ith bonzono; (6) Grignard s y n th e s is ; and (7) hydrogenation o f alk yl aryl ketones.

E ach reaction is considorod and explained in eloctronie term s. Certain com plicated reactions difficult o f explan ation on a logical basis and w hich lead to contradictory conclusions can bo explained by, and are in agreem ent w ith , th e fundam ental ideas o f activ a tio n and add ition o f an addend after cleavago in accordanco w ith M arkownikoff’s rule. Tho first six m eth od s are considorod un su ited w ith regard to good yield and p u rity o f tho product.

T h e hydrogenation of alk y l aryl k etones propared b y th e Friedel and Crafts’ reaction (acylation of bonzono) appears to bo tho host m eth od for obtaining tho largo qu antities of hydrocarbons w h ich aro necessary for tho determ ination o f cctano num bers. T h is process is on th e w hole of a sim ple character, n o t ^involving rearrangem ent o f alk yl groups, and is unaccom panied b y sido reaction s; further, tho process does n o t in volve a too-elaborate organic tochniquo. Palladium is tho b est ca ta ly st for carrying o u t tho hydrogenation. Considering different chem ical m eth od s of reduction, th e Clem mensen’s m eth od is to be preferred.

Nu m e r o u s

m ethods are available for th e p rep aratio n o f th e m ono-n-alkyl- benzenes, an d in a survey o f tho lite ra tu re certain m ethods are difficult, o thers easy in technique. The yield o f th e p ro d u c t is, as a rule, low, a n d th e p u re hydrocarbon can be iso lated only w ith difficulty. T hus, a com ­ p ara tiv e a n d critical stu d y o f a ll available m ethods m entioned in th e lite ra tu re has been m ade. E ig h t principal m ethods for th e alk y latio n o f th e aro m atic nucleus are in use :—

(1) F ittig ’s synthesis.

(2) C ondensation o f alk y l halides w ith benzene using alum inium chloride (Friedel a n d C rafts’ reaction) or hydrogen fluoride.

(3) C ondensation o f d efin es w ith benzene in th e presence of hydrogen fluoride, sulphuric acid, alum inium chloride, ferric chloride, or phosphoric acid.

(4) C ondensation o f alcohols w ith benzene in th e presence o f boron trifluoride, alum inium chloride, phosphorus pentoxide, or boric acid (through th e in term e d iate form ation o f R 3B 0 3 from th e corresponding alcohol, R O H , an d boric acid) a n d alum inium chloride.

(5) In te ra c tio n o f inorganic a n d organic esters w ith benzene in tho presence o f boron trifluoride, alum inium chloride, or hydrogen fluoride.

(6) G rignard synthesis.

(I) H ydrogenation o f alk y l a ry l k etones which m ay be p repared by th e following principal m ethods :—

4 7 5

* Paper received 8th M ay, 1940.

4 7 6 SH EN, JTJ, AN D WOOD : SYNTHESIS A ND

(a) A cylation o f benzene b y F riedel an d C rafts’ reaction.

(b) G rignard synthesis.

(c) P assing th e vapours o f benzoic a n d th e f a tty acids through h ea te d m anganous oxide or th o riu m oxide according to th e elegant m ethod o f S abatier.

(8) R eaction betw een cyclopropane a n d benzene using as c a ta ly st lydrogen fluoride. The ex p lan a tio n o f th e reactio n possibly involves tno1o 11i n rt?mehaniSm (Sim ons> A rdrnr, a n d A dam s, J . A m er. cliem. Soc., 19o8j 60j fc/955— 2956Ji

** is in terestin g to review briefly th e m ethods w hich hav e a t tim es been u tilized for th is p a rtic u la r ty p e o f alk y latio n .

(1) F ittig ’s Synthesis.

The first stage in th e accepted ex p lan atio n o f th e F ittig reactio n (Tollens an d F ittig , A nnalcn, 1864, 131, 303) is th e form ation o f sodium phenyl b HZ t (AcrC?’ A m e r' Ckem - J -’ 1903> 29> 5 8 8 1 Sohlubach, Ber., 1922,’

55, -889), on th e im m ed iate liberation o f th e phen y l rad ical. The second stage involves th e reactio n o f sodium phen y l w ith th e alk y l or ary l halide in accordance w ith th e following e x p lan atio n , in w hich i t is in terestin g to n o te th e am p h o teric c h a ra c ter o f carbon :—

~ : C l: N a : 6 i :

V

The p olar com pound re acts m ore read ily w ith th e a lk y l halide th a n w ith th e ary l halide, an d on th is acco u n t th e yield o f a lk y la te d benzene is m uch b e tte r th a n would be a n tic ip a te d in view o f th e th ree possible pro d u cts.

.Butylene, b u tan e (both form ed from th e free radicals), a n d diphenyl are by-products. Sodium is th e m e ta l m ost useful for coupling alk y l a n d aryl radicals. B achm ann a n d C larke (J. A m er. chem. Soc., 1927, 49, 2089) ound t h a t th e a ctio n o f sodium on chlorobenzene a t th e boiling p o in t gave benzene, diphenyl, o-diphenylbenzene, triphenylene, 2 : 2-diphenyl-

M

M

PROPERTIES OP MONO-NOKMAL-ALKYLBENZENES. PART I . 4 7 7

diphenyl a n d resinous t a r s ; fu rth er, th e actio n o f sodium on m-heptyl brom ide gave « -h ep tan e, heptylene, tetra d ecan e , heneicosane, a n d high- m olecular-w eight hydrocarbons. Copper, however, is m o st su ited for this ty p e of coupling.

«-Am ylbenzene was p rep ared by Schram m (A nn a len , 1883, 218, 388) b y action of sodium on a m ix tu re o f benzyl brom ide a n d b u ty l brom ide.

T he yield was a b o u t 25 p er cent, th eo retical, dibenzyl a n d «-octane an d some unidentified hydrocarbons being form ed a t th e sam e tim e. Radcliffe a n d Sim pkin (J . Soc. chem. In d ., 1921, 40, 119-122t) use benzyl chloride in ste ad o f benzyl brom ide, a n d th e yield is sim ilar to t h a t o b tain ed b y using benzyl brom ide, b u t requires a longer tim e for com pletion o f th e reaction. «-A m ylbenzene w as also p repared b y Radcliffe a n d Sim pkin

m etallic sodium , th e yield being tw o to th ree tim es g reater.

Possible com binations o f organo-sodium com pounds an d organic chlorides in th e F ittig ’s synthesis o f «-am ylbenzene hav e been stu d ied re c e n tly b y M orton an d F allw ell (J. Am er. chem. Soc., 1938, 60, 1429-1431). The yield was low (5-11 p er cent.). H ow ever, a b e tte r yield (54-70 per cent.) was o b tain ed b y using sodium benzyl in ste a d of sodium phenyl.

I n view o f these side reactions, which, in c e rtain circum stances, m ight well overwhelm th e required synthesis, th e F ittig reactio n is n o t satisfacto ry for preparing long-chain benzene hom ologues, th e isolation o f which in th e pure condition from com plex by-products en ta ils elaborate technique w ith consequent dim inution in yield.

(2) Condensation o f A lk y l Halides with Benzene in the Presence o f A lu m in iu m

F riedel a n d C rafts (Compt. rend., 1877, 84, 1392, 1450; cf. Ashdown,

am yl c h lo rid e ; th e hydrocarbon, how ever, h a d b.p. 185-190°. According to re cen t lite ra tu re , «-am ylbenzene has b.p. 205-3° (Simon, B ull. Soc.

chim. Belg., 1929, 38, 47) a n d th e te rtia ry com pound boils a t 190° (Verley, B ull. Soc. chim., 1898, (3), 19, 6 7 ; T zukervanik, J . Gen. chem. U .S .S .R .,

1935, 5, 117). This in d icates eith er th a t th e a m y l chloride used b y F riedel a n d C rafts w as n o t th e pu re n o rm al com pound, or, if such w as em ployed, th e n rearran g em en t o f th e «-am yl group h a d ta k e n place in th e reaction.

Simon a n d A rcher (J. Am er. chem. Soc., 1938, 60, 2953) o b tain ed o n ly fair yields o f th e alk y la te d benzenes b y using hydrogen fluoride. F rom «-propyl brom ide a 48 p er cent, yield o f propylbenzenes (containing 88 p e r cent, isopropyl a n d 12 p er cent, m-propyl) an d from feri.-am yl chloride a 41-5 p e r cent, yield o f m ono-terf.-am ylbenzene were obtained. T he following shows th e ease of rearran g em en t o f th e halides :—

Tomporaturo. H alide. P rod uct.

0°

H igher tem perature th a n 0°

A s low a s —18°

«-P ropyl halide n -B u ty l halide n -B u ty l halide iso B u ty l halido

¿soAmyl halide

t-soPropylbonzcno predom inates.

n -B u ty l- and sec.-bu tyl benzene.

sec.-B utylbenzene.

terP-Butylbenzene exelusi%’ely.

tsoA m ylbenzene and ier/.-am yl­

benzene.