V o l . 31. N o. 258. Ju n e 1945.
THE ANALYSIS OF TRINIDAD CRUDE OILS.*
II. THE PARAFFINIC OILS.
B y F . M o r t o n f a n d A . R . R i c h a r d s . !
In t r o d u c t i o n.
I n a previous com m unication 1 from these laboratories th e analysis of a num ber of crude oils from th e F orest R eserve F ield was described. I t was suggested th a t th e crude oils of T rinidad consist essentially of tw o m ain ty p es—nam ely, a paraffinic oil yielding, on distillation, a n a p h th a of th e paraffin—arom atic type, an d a naphthenic oil yielding a n a p h th a of m ixed naph th en ic ty p e. Subsequent studies of th e crude oils of th e F o rest Sands of th e B ernstein A r e a 2 indicated th a t th e interm ediate character of th e oils m ight be explained by th e m igration of th e p araffin- arom atic ty p e oil into an area originally containing oils of th e naphthenic ty p e. In view of th e fact th a t paraffinic ty p e oils occur th ro u g h o u t th e pro
ducing areas of T rinidad (i.e., G uayaguayare, Morne Diablo, F orest Reserve, etc., etc.), it was desirable to exam ine these oils in order to ascertain w hether or n o t a common history could be supported on chemical grounds.
T he present com m unication deals w ith th e analysis of fourteen individual crude oils draw n from four different areas. The examples given have been chosen from am ong several h undred as best illustrating th e variations in crude-oil com position encountered w ithin a single ty p e oil. F re a k oils, such as oils of unusual arom atic content, have been excluded, b u t exam ples of th e “ distillate oils ” hav e been given to illu stra te th e fact t h a t th e com position of th e n a p h th a from these oils is identical w ith th a t associated w ith th e heavier oils in th e sam e area.
The m ethods of analysis used th ro u g h o u t th e survey have n a tu rally been subject to m odification from tim e to tim e. Originally crude oils were classified by reference to th e physical constants of th e fractions of a precisely fractio n ated n a p h th a p lo tted as th e characteristic g ra p h .1 W here it was necessary to estim ate th e com position of a given fraction in term s of its constituent hydrocarbons, th is was done by reference to frac
tions isolated in a more detailed stu d y of bulk crude oils of T rinidad, th e chemical composition of which h ad been established by com bined physical an d chemical m ethods. I t was early realized th a t simple com parative d a ta would be insufficient in view of th e com plicated n atu re of th e geo
chem ical problem s involved, and th a t to extend th e value of th e survey beyond th e needs of simple exploitation problems a detailed chemical analysis of th e n a p h th a s would be necessary. I n order to m a in ta in th e con tin u ity of th e work, this was first a tte m p te d by extraction of th e arom atic hydrocarbons from th e individual fractions obtained by th e precise fractionation of th e n a p h th a after d eterm ination of th e physical constants required to construct th e characteristic graph. D eterm ination of th e physical constants afte r acid extraction enabled an approxim ate
* M an u scrip t received 1st F e b ru a ry , 1945.
f M essrs. T rin id a d L easeholds, L td ., P o in te-a -F ie rre , T rin id ad , O
160 MORTON AND RICH A RD S :
d e term in atio n of th e paraffin -n ap h th en e ra tio to be m ade, a n d from this th e relative am ounts of groups of hydrocarbons could be com puted, I t was realized th a t th is procedure was open to serious objections. F irstly , th e existence of constant-boiling m ixtures in th e original fractio n atio n would preclude reliable com parison o f th e non-arom atic p o rtio n w ith published d a ta , a n d secondly th e use of sulphuric acid m ight lead to d isproportionation an d to destruction, or ex tractio n , of non-arom atic m ate rial (more p artic u larly hydrocarbons containing a te rtia ry carbon atom ). A num b er of analyses proved t h a t u n d er carefully controlled conditions of e x tractio n th e results could be d uplicated w ith ease.
F u rth e r w ork has resulted in our discarding th e ch aracteristic g rap h in favour of a fractio n atio n of th e n a p h th a afte r rem oval of th e arom atic h ydrocarbons,3 th u s enabling a m ore precise sta te m e n t to be m ade con
cerning th e chem ical com position of th e non-arom atic portion.
T he analyses rep o rted h erein belong to th e tra n sitio n period, an d are based on th e early technique coupled w ith acid ex tra c tio n of th e individual n a p h th a fractions. Subsequent w ork has show n t h a t th e analyses given are sufficiently accurate to be used in geo-chem ical studies, an d th e general findings have n o t been in v alid ated by la te r an d m ore precise analysis.
Me t h o d s o f An a l y s i s.
T he m ethods of analysis em ployed th ro u g h o u t th e presen t w ork are essentially those described in P a r t I of th is series.1 T he P rim a ry Dis
tilla tio n an d S upplem entary A nalysis * rem ain su b sta n tia lly unaltered.
I n th e n a p h th a characterization, however, th e ind iv id u al fractions are e x tra c te d w ith 98-5 per cent, sulphuric acid below 20° C. to constant aniline p o in t an d th e physical con stan ts of th e fractions before and after ex tractio n are recorded. As in previous w ork, th e physical constants of th e fractions prior to acid ex tractio n have been used to co n stru ct charac
teristic graphs of th e n a p h th a s (Figs. 1-14) to w hich has been added the aniline p o in t of th e fractions afte r acid ex tractio n . T he physical constants of th e arom atic-free fractions have been used to estim a te th e paraffin- n a p h th en e ratio, an d th is ratio , to g eth er w ith physical properties, has been used in assessing th e probable am o u n ts of various hydrocarbon groups.
Ge n e r a l Re s u l t s.
T he analyses of fourteen crude oils are reported, five from F o re st Reserve, four from G uayaguayare, th re e from Morne D iablo, a n d tw o from th e P alo Seco field of Messrs. S iparia T rin id ad Oilfields, L td . T he routine analysis of these oils is given in T able I, to g eth er w ith th e asphaltene co n ten t of th e crude oils. T he oils are arranged in order of ascending paraffinicity (see T able I I I ) , an d n o t in an y relatio n to th e ir geological occurrence. I t will be no ted th a t th e characteristics of th e oils are similar, a n d t h a t th e y exhibit th e ty p ical properties of paraffinic crude oils : viz., high fight fractions, low octane num ber, low crude oil g rav ity , low a sp h a lt
ene content, low sulphur, etc. To these general sim ilarities th ere are
* I n th e su p p le m e n ta ry a n a ly sis d e sc rib e d in th e J . I n s t. P etrol., 1943, 29 (230), 59, a ty p o g ra p h ic a l e rro r occurs. T h e fa c to r fo r x y len e g iv en a s a = 0-39A sh o u ld re a d a = T39A.
T H E A NALYSIS OF TR IN ID A D CRTJDE OILS. 161
0
10
20
30
40
50
60
70
80
A .P .,
° C.
- 1 0
0
10
20
30
40
50
60
70 A .P .,
° C.
- 1 0
80 0-72
X or CRUOC Fig. 1.
Fi g. 2.
162 MORTON AND R ICH A RD S :
A .P .,
° C.
- 1 0
0
10
20
30
40
50
60
70
80
A .P .,
° C.
- 1 0
0
10
20
30
40
50
60
70
80
^ o f c ru d e
Fi g. 3.
Fi g. 4.
TH E ANALYSIS OF TR IN ID A D CR U D E OILS. 163
0
10
20
30
40
50
60
70
80
A .P .,
•c.
- 1 0
0
10
20
30
40
50
60
70 A .P .,
° C.
- 1 0
80
0-96 1-53
0-92 1-51
0-88
0-84
0-80
0-76
0-72
0-68
0-64
0-60 1-
0-96
0-92
0-88
0-84
0-80
0-76
0-72
0-68
0-64
0-60 1-39
1-37
1-35
X o * CRUOC
Fig. 5.
Fi g. 6.
A .P .,
° C.
- 1 0
o 10 20
30
40
50
60
70
80
A .P .,
° C.
- 1 0
o
10
20
30
40
50
60
70 164
80
MORTON AND RICH A RD S :
d^°. ri™.
0-96 1-53
Fig. 7.
0-96 1-53
0-92 1-51
0-68 1-39
0-64 1-37
0-60 1-35
Fig. 8.
TH E ANALYSIS OF TR IN ID A D C R U D E OILS. 165
0
10
20
30
40
50
60
70
80
A .P .,
° C.
- 1 0
0
10
20
30
40
50
60
70 A .P.,
° C.
- 1 0
80
d™.4
0-96
0-92
0-88
0-84
0-80
0-76
0-72
0-68
0-64
0-60
0-72 1-41
0-68 1-39
0-64 1-37
0-60 1-35
Fi g. 10.
166 MOUTON AND RICH A RD S :
A .P .,
F ia . 11.
A .P .,
- 1 0 0-96 1-53
0 0-92 1-51
40 0-76 1-43
70 0-64 1-37
80 0-60 1-35
F ia . 12.
T H E A N ALYSIS OF TR IN ID A D CRUDE OILS. 167
0
10
20
30
40
50
60
70
80
A .P .,
° C.
- 1 0
0
10
20
30
40
50
60
70 A.P.,
° C.
-1 0
80 á®°.
0-96 1-53
0-92 1-51
0-88 1-49
0-84 1-47
0-80 1-45
0-76 1-43
0-72 1-41
0-68 1-39
0-64 1-37
0-60 1-35
d ? °.
0-96 1-53
0-92 1-51
0-88 1-49
0-84 1-47
0-80 1-45
0-76 1-43
0-72 1-41
0-68 1-39
0'64 1-37
0-60 1-35
O F CRUDE
Pig. 13.
y . o r CRUDE
Fi g. 14.
Crude EvaluationData.
168 MORTON AND RICH A RD S
.FQ C5”
û3 T-H. to
ç^co• CO
Roígeo
p3 CO
Jijeo
« S
n d o
fi.w
g'S
1 “
t> tO
O '*
i>
¿ Ñ
00 05 Ô
CO 03 ó ¿
or-03
O M
05 Ó
Oco
cb Ô
O '*
r ^ ô
GO 05 Ô CO
OtH
¿6
O Necó
00 O ON
GO 03 Ô Ô
GO 00
¿>03
05 3>
¿ Ñ
S '3 °o
r’H >*
^ ¡ v a
o ex..
tf S = d O
co . bp>>
c3 3
.^CQ m
“ g dS3
ó S . a » o
coOÍ> H
03100510 03
03 tO tH lO tO c¿
tO O tO 03 to
¿^NOîÇÇ
coPhôôÔ'*
W I > 03 O
O l O H O CO
N tO O tO
cb^cb 03
03 O tO 03
tH tO 05 tO CO
COCO 05 10
tó^ CO l>
03 O tO H
H N H O 03 05 05 !>• O CO Ô ¿5 CO
OCO H O
0 0 3 ÔrH
O CO CO Ô
CO 1^ to tO Tf 05 CO O
O N O IO CO 0 0 5 0 5 0
I>l>CO to TH ¿ 0 3 03
03 CO 00 05 O
00 05 0 3 0 rH ô Ô5CÔ
■H* t :
c3 £
Pr£ O^P •§
•n w eo ,c3
Pi
CÛ * * • O bD *
• • M O a Ç« ° o<3 «$ -O- P OCO .rri
•2 r0 -*n bO 05 2 •
« ° E . - s s ®
O CC0 3
S S05 •
CO 05
■**
H o
“ T*1 o c o
’“íó
ô
QO o
ü ^rH
§ . -î* • N *m’S ¡>
ö * . M.S >, ■ S S « f t l .
S “ ¿ í ¿ .
" ¿8.3.3 g
vp
rP fâ,FHpH w
h O o
I - S t «
ns ?
* M.D. = Mome Diablo, TrinidadLeaseholds,Ltd. F.R. = ForestReserve, TrinidadLeaseholds,Ltd. G. = Guayaguayare, TrinidadLeaseholds, Ltd. S.T.O.L. = SipariaTrinidadOilfields, Ltd., Palo Seco.
TableII. Analysisof SecondaryDistillates. Volume Percent.Composition.
TH E A NALYSIS OP TR IN ID A D CR U D E O ILS. 169
G. 152. t o c o rH H rHC© ¿ 5 03
CO
¿5 C0 C0 '*H0 0 © © O © 0 3 © 0 5 r H £ > ©
© r H c b © r H ^ © © < Ñ c b r H r H0 3 rH
23-9 H H W ^ O O N H C O t O H C O t n O C O C O CO Ó rH ^ C O t ^ ^ t Ó ^ ^ r H c b r H l Ó l > c b
rH rH 570
G. 153.
t o c o O l CO r H c b t > r H
Sil CO CO C OtOC O r-IG O O O i—U0 0 0 O 0 3 G0 Ó 0 3 CO rH Ó © Ó Ó CO CO Ó rH rH Ó
25-8
t o t o o
t o 03 CO 00 05 CO rH CO 03 03 l > © tO CO 05 O h hh © c b t ^ c b c b ^ ^ i Ñ ^ c Ñ c b ó c b
56-7
G. 133B.
cr 9 N 0
r H l > C5<>3
©
Ó03
O O t O0 5 O 03 0 3 C0 C0 r H 0 0 0 5 t0 CO 0 < ^ ^ © r H t b r H r H < > 3 c b r H © r H r H
27-3
CO
tO GO r—1 O O C0 9 C0 ^ r H « 0 9 9 © 9 r H0 3 rH CO 05 t ó <¿ t o rH 03 rH t ó CO 03
rH rH 52-7
P.R. 651. C5 GO tO rH
©0 3 c b <>3
12-3 tO t^ (N < N C O C D ( N C O i0 0 3 0 0 0 0 0 3
¿ W c b ( Ñ Ó ^ r H r H c b c o Ó3 Ó3 c b Ó 3 03 CO CO
©
CO CO GO C O N O N t O N H C O X O O C O C O 'C tÓ I > Ó c b r H t ^ l ß c b r b r H0 C3 r H © l b c b
54-5
0 0 «
rioo
Cn 00
^ TH •
L - CO D- CO CO rH
G0 tO O 5 T tfO C 0 C0 C0 C0 0 3 O 0 0 '^ t O Ó rH CO rH rH rH rH 03 0 3 0 3 CO rH 03 03
CO rH CO
t o tO 03
0 0 3 0 0 © © © C O C O O3 O3 © O 3 © © C 0 iC -H I > © CO 03 Ó © tÓ 03 CO rH rH rH *Ó © 03
H H rH
CO rH tO
O M O M
© rH t > 03
to rHC0 I > r t i t 0 0 5 i O C 5 r H 0 3 t H 0 3 © © Ó rH CO rH Ó C¿ rH Ó 03 CO 03 rH 03 rH
32-4
05
05 t o o r * t^ - c o CO 03 CO rH rH rH I > 05 CO VO rH 05 tÓ tÓ rH rH tO rH rH tH CO rH 03 rH rH
OSS
G. 151. COCO I > t o rH tÓ l> 0 3
17-3 © C0 H <D-C0 0 3 t H 0 0 O t H O 0 3 © ©
© rH CO rH rH l b rH Ó rH 03 03 rH 03 rH
300 tO t o t o
C O C O © t O O ^ C O O C O G O ^ H < C O C O t O H <
t b r H r H © c b CO © 03 rH 03 03 rH ó t o t o CO
52-7
p ä . Lt, CO
^ C O
H N H N
15-6
C*-" (N-
O0 3 C0 O G 0 C0 G0 r H t0 G0 0 3 0 3 t0 0 3
© C O ^ ( Ñ Ó t b © C3 c b c b Ó 3 © © Ó 3
31-7
t o t o CO
CO O 0 5 0 0 0 3 COG0 0 3 C0 0 3 0 3 0 tH I> C O l ó c b Ó t o c b Ó c b t o c b rH tH rH rH t o tH rH
rH rH 52-6
M.D. 32. I>CO lO H
13-9 0 3 ' ^ t O © © 0 5 0 1 rH l> G O C 0 0 3 © r H rH 03 i b Ó rH CO rH tH CO CO 03 03 rH rH
37-9
00
tO rH rH lO tO Q O C O rH C O C S lC O tO rH O G O rH
©1> t H c b 0 3 rH t > CO CO rH rH rH rH t b rH rH 03 rH
03 00rH
S.T.O.L. 35. t ^ O C O TH r H t b l> 0 3
16-7 tO i0 0 5 C0 C0 I > O 0 3 " ^ c 0 C0 O 0 3 G0 Ó c b CO rH rH rH rH 03 rH CO 03 CO CO 03
37-2
L - tO 05 03 C O ^ t ^ r H O c O r H r H r H C O r H O r H
i > Ó5<© t b (Ñ t > t b c b c b c b rH t h © rH t b 03 rH rH
rH c b rH
C¿CÓ
•TH i > © r H o3 rH > r* £ ^ Ó3
16-2 0 0 © G O I > © C 3 © 0 3 © 0 0 © © © 0 3 rH 03 CO rH rH l b rH 03 l b r}( CO 03 l b 03
42-8
CO
© GO 05 CO G0 © © C O G p r H O 3 COC0 O3 I>- T H r H © c b t b t b c b c b 03 03 rH © rH c b 03
03 03 40-9
F.R. 651B.
© tO 03 03 rH 03 0 03
11-9 © ^ C3 C ^ rH O 3 C0 C 5 © O 3 © r H O 3 © 0 3 O3 C ¿ t H t —IC O rH C SlC O iÓ cO C O iÓ cO
t o CO rtf
CO 03 © © r H O C0 G0 G0 © r H r H C 0 t0 I > 0 3 C0 rH rH rH rH Ó3 t b c b r H r H c b © © © t b Ó 3 cb
03 03 39-9
S.T.O.L. 20. 05 I > Th lO Ó © <35 03
t o 05 rH
0 0 GO rH CO 03 CO rH CD © rH 03 GO 03 rH Ó 03 CO rH rH CD rH 03 rH CO rH 03 CO CO
41-5
t o t o CO
t^ t^ -G O C^G Oi0 0 3 0 0 © C O © C O C O C p 0 3 TH
0 0 0 3 © (ÑrH^tb(Ñcb<Ñcb©©rHibÓ3
rH 03 391
M.D. 29B.
tO I> 0 3 05 T H iÓ Ó G S l
CO
Ó03
r H © r ^ r H C O C5 © © r H © O0 < 0 GO L~
Ö H t H H H CD rH CO t b rH CO 05 CO 03 t o r * -H
tO tO rH
CO rH © © © C p ^ G O C O r H C O r H © C p t O 03 03 rH cb c b t b r H c b r H © < © © t b Ó3 c b
03 03 35-1
Well No. Aromatics: B........................................... T........................................... X........................................... C... Total Naphthenes : 5 + M5 * . M5 *........................................... (6 + 11M5)t 11M5 * (13M5 + M6)f • M6... E5 *........................................... Tri-M5’s * . (Di-M6's + ME5) t E6........................................... Di-ME5’S... Alk5 * Pr6........................................... Ciot... Total Total cyciohexane derivatives Total cj/eiopentane derivatives Ratioc6/e5 naphthenes Paraffins i i5 + n5 22M4 (?) . 6+ Di-M5 .... M6........................................... 7... Di-M6.... i8 (M7's).... M7 + 8. 8+ Di-M7’s Di-M7’s .... Di-M7's.... CVs... M9’s... Total Fordetailsofabbreviations usedsee A. R. Richards,Nature, 1944,153,715. * c5’s. t Split 50/50 c6/c5 for purposeofcalculatingc6/c5 ratio.
170 M ORTON AND KICH A B D S :
G. 162. 50-36 9-72 12-04 28-60 19-3 23-9 56-8 1-29 2-38
G. 153. r-1 C5 t > lO O O
C 3 C O C O H 1 H CO CO CO<>3 r H C S J O O O N l O O rH CSJ
H N iQ
G. 133B. 41-65 8-33 11-37 21-95 200 27-3 52-7 1-13 1-93
& § >
O rH T—I T * 0 3 CO
l O i O O H CO T il CO CO £ >
H ^ O N H l r H H l ¿ H
CO i - l rH CO lO
Cd rA
• VO
CO CO lO t o C S C o
O C 1 C O I > CO CO ^ coo
O rH O CO 03 CO H O H
rH H C O i O
M.D. 11. 2303 3-36 7-46 12-21 14-6 32-4 53-0 1-09 1-64
G. 151. 17-21 2-98 5-16 9-07 17-2 30-1 52-7 1-05 1-76
• CO P R ' S
i H uO O t > C O O
O O C O O O D - D - OS O
* > © 3 0 0 0 i O r—I 03 O tH
tH H C O i O
M.D. 32. O T f i C O O CO D -
tO H CO H< C S C S 0 3 rH 03 D - 03 CO 0 0 CO D - CO H H
i - l rH CO H I
S.X.O.L. 35. H U O O C S 03 H i
© 3 l Q O I > D - 03 rH OS 03 T H C O t > C S C O I > c b O H
0 3 tH CO H i
r A co
f c o
CO O H 1 H i O O
CO CO JH CO © 3 0 0 OS CS o c b c b o o o 03 o o o
03 rH H H i
p4 2
O C O N H 0 0 3
CO 03 03 CO 0p 1? 1^ ‘? c?
O r H l O H I rH CO CS H O
rH i H H i CO
S.T.O.L. 20. CS O O H i CO H i
CS H H O H i iO rH C O O l > CO I > I > C S rH o O O
rH r H H I CO
M.D. 29B. 12-19 2-49 5-42 4-28 20-4 44-5 35-1 1-01 0-79
Well No. % oncrude: Secondarydistillate Aromatics.... Naphthenes Paraffins .... % onsecondarydistillate: Aromatics.... Naphthenes Paraffins .... Ratioc6/c5 naphthenes * Ratioparaffins/naphthenes
T H E ANALYSIS OP TR IN ID A D CR U D E OILS. 171 exceptions. T he octane num bers of light fractions of th e oils from Wells 651, 651B, an d M.D.29D are higher th a n are usual, w hilst th e asphaltene contents of th e oils from Wells M.D.29B and S.T.O.L. 35 are high.
D espite these exceptions th e oils would be classified on th e basis of th e routine inspection d ata , as low-octane paraffinic crude oils.
B y com parison of th e properties of th e arom atic-free fractions w ith th e physical constants of pure hydrocarbons and th e synthetic m ixtures, an a tte m p t has been m ade to calculate th e am ounts of individual h y d ro carbons or groups of hydrocarbons which constitute th e paraffin or n ap h th en e com ponent of th e various fractions. T he results of these calculations are given in Table I I , which lists for each crude oil th e am ounts of various hydrocarbons as a percentage of secondary distillate.
T he to ta l p araffin -n ap h th en e-aro m atic content of th e secondary distillate is given in T able I I I , b o th as th e percentage in th e secondary distillate an d as a percentage of th e p a re n t crude oil. In Table I I I th ere is also recorded th e ratio of cyciohexane to cycfopentane derivatives and th e ratio of paraffins to naphthenes.
I t is n o t claimed th a t th e analysis given in Table I I is an ything more th a n an approxim ation based entirely on physical characteristics, an d no proof is offered a t th e m om ent for th e presence of an y one of th e individual hydrocarbons. The modified technique can, however, be carried out alm ost as quickly as th e original and by its use it is possible to differentiate betw een oils w hich would otherwise be regarded as th e same. A com
parison of Figs. 1 and 10 w ith th e d a ta of Table I I I illustrates th is point.
Di s c u s s i o n o e Re s u l t s.
The G uayaguayare oils are th e m ost paraffinic oils so far encountered.
T he wells 152, 153, and 133B are producing from th e same horizon in th e G oudron field, and although th e n ap h th as are identical, th e variations in light fraction content are som ew hat surprising. Correlation in th is area is difficult, and fu rth e r investigations are being carried out. The absence of heavy ends and th e low asphaltene content suggest th a t th e oils have been subjected to some separation effect. W ell 151 is situ ated in th e Logeon spur, a n d th e oil m ay be regarded as ty p ical of th e G uayaguayare area.4 I t will be no ted th a t th e n a p h th a is very similar to th e n ap h th as of th e Goudron oils, an d for th is reason a sim ilar source m ay be postulated.
I t is highly probable th a t th e oils of Wells 152, 153, etc., have been form ed from an oil of th e 151 type.
T he F orest R eserve oils are all from th e Lower Cruse Horizon. Similar oils have been described previously, an d th e occurrence of naphthenic oils an d oils of m ixed character in th e sands of th e Lower Cruse series has been discussed.1 The oils herein described are th e m ost paraffinic so far en
countered in th is area, b u t th e oils of Wells 651B and 643 show clearly th e effect of mixing w ith a naphthenic ty p e oil. The m ost paraffinic oils—those of Wells 488B and 651—are similar in character an d contain less arom atic hydrocarbons th a n th e G uayaguayare oils. Comparison of th e oils of W ell 151G. and 651F/R . indicates th e lower arom atic content of th e paraffinic oils of F orest Reserve.
Of th e Morne D iablo oils, th a t of Well M .D .ll is from th e Middle Cruse Horizon, w hilst th e oil of M.29B. is from th e U pper Cruse. I n this area
172 T H E AN A LY SIS OF T R IN ID A D C R Ü D E O ILS.
a good deal of m ixing has occurred, an d th e oil of M.D.29B is obviously a m ixed oil. T he paraffinic oil of M .D .ll is, however, ty p ical of th e M iddle Cruse sands, an d its sim ilarity to th e F o re st R eserve oils of W ells 651 an d 488B should be noted. Again, th e oil is less aro m atic th a n th e com parable G uayaguayare oil.
Two oils from S.O.T.L. have been included for reference purposes.
B o th are from th e Cruse series. H ere, as a t Morne D iablo, th e occurrence of m ixed oils is a featu re of th e area, a n d b o th oils show th e ad m ix tu re of a naph th en ic oil. T he high arom atic co n ten t is a characteristic feature of th e oils from th is area.
Reference to Table I I I shows t h a t th e increase in paraffinicity th ro u g h o u t th e series is n o t accom panied by a general increase in arom atic content, an d th a t although th e n ap h th en e co n ten t decreases w ith increasing paraffin content, th is decrease is n o t uniform . If, however, th e oils from sim ilar areas are considered, it will be seen th a t th e n a p h th en e co n ten t decreases w ith increasing paraffin content, although th e arom atic co n ten t does n o t show a uniform increase. I t has been shown t h a t arom atic hydrocarbons are norm ally associated w ith paraffin hydrocarbons in th e n a p h th a of crude oils, an d th a t in th e p redom inantly n ap h th en ic oils arom atic h y d ro carbons are present in th e n a p h th a in v ery sm all am o u n ts.1- 5 I t therefore follows t h a t th e crude oils u n d er ex am ination cannot be form ed by th e sim ple m ixing of tw o p a re n t crude oils, unless one of th e oils has undergone considerable changes in arom atic content. E v en w ithin th e lim ited area o f th e Lower Cruse sands of F o re st R eserve, th e v ariatio n s in arom atic co n ten t are such as to preclude th e form ation of th e oils by simple m ixing of tw o oils unless it can be show n t h a t th e p araffin -aro m atic com ponent has undergone changes in arom atic content, as, for exam ple, by adsorption during m igration.
T here is, however, insufficient evidence to su p p o rt such a th eo ry , and all t h a t can be sta te d w ith c e rta in ty is th a t th e p araffin -aro m atic oils of T rinidad, although o f th e one ty p e, ex h ib it fu n d am en tal differences th ro u g h o u t th e producing areas exam ined.
Ac k n o w l e d g m e n t.
T he au th o rs wish to express th e ir g ra titu d e to D r. C. J . M ay a n d D r.
H . G. K ugler of th e P ro d u ctio n an d Geological Divisions for assistance in p lanning th e su rv e y ; to Mr. A. E . G erty of th e R efinery L a b o ra to ry for d a ta given in T able I, an d to Mr. A. J . R u th v en -M u rray an d th e B oard of Messrs. T rinidad Leaseholds, L td ., for perm ission to publish work carried o u t in th e C om pany’s R esearch L aboratories.
T h an k s are also due to Messrs. Siparia T rin id ad Oilfields, L td ., for perm ission to publish th e analysis of certain crude oils.
B ib lio g ra p h y .
1 F . M o rto n a n d A. R . R ic h a rd s, J . I n s t. Petrol., 1943, 29 (230), 55.
3 K . W . B a rr, F . M orto n a n d A. R . R ich a rd s, B u ll. A m er. A ssoc. Petrol. Oeol., 1943, 27, 1595.
3 A. F . F o rz ia ti, C. B . W illin g h am , B. J . M air a n d F . D . R o ssin i, J . Res. N a t. B u r.
S td ., R P . 1571, 1944, 32, 11.
4 I . M eC ullan, “ Science o f P e tro le u m ,” V ol. I I , p . 879.
6 M. R . F e n sk e , C. O. T o n g b erg a n d W . J . Sw eeney, I n d . E ng. Chem ., 1938, 30, 166.
173
DIAGNOSTIC CHARACTERISTICS OF CRUDE O IL:
FLUORESCENCE ANALYSIS IN ULTRA-VIOLET LIGHT.*
B y J . N. M u k h e r j e e , C.B.E., D.Sc., F .N .I .,f an d M. K . I n d r a , M .Sc.f
In t r o d u c t i o n.
I t h a s l o n g b e e n f e l t , e s p e c i a l l y b y g e o lo g is ts , t h a t a r e l a t i v e l y s im p le m e t h o d of d i s t i n g u i s h i n g b e t w e e n o ils o f d i f f e r e n t o r i g in w o u l d h a v e i m p o r t a n t a p p li c a t io n s .
The more obvious of these applications are th e detection of “ salted ” or faked oil seepages and th e distinction betw een tru e oil-shows in the m ud retu rn s of an exploratory well and accidental contam ination of th e m ud-fluid by lubricating oil from some p a rt of th e drilling rig. I t is also necessary to have some m eans of detecting th e presence of traces of crude oil in cores and in surface samples.
A larger sphere of inquiry is presented by th e desirability of being able to distinguish betw een crude oils of different origins. The geologist, in his search for source-rocks, wishes to know w hether th e oil occurrences of a petroliferous region have th e same origin or are derived from different sources. H e m ay also wish to know w hether oil occurrences of tw o neigh
bouring b u t possibly related regions have th e same or different origins.
T his aspect of th e subject has been sum m arized in a paper published posthum ously from notes prepared b y D. C. B arto n .1
I t is well know n th a t in one oilfield there m ay be a large range through which th e physical properties of th e oil v ary . In th e B ad arp u r oilfield in Assam th e oil in tw o of th e sands was m uch lighter in th e southern p a rt of th e field th a n in th e northern, th e flash-point varying from below 80° F . to over 230° F . w ithin three-q u arters of a mile. Still more rem ark able was th e occurrence of a zone w ith light oil flashing a t 70° F . sand
wiched between tw o zones of heavy oil flashing a t over 200° F . In th e Dighoi oilfield of Assam there are several types of oil showing a complex distribution depending p a rtly on horizon and p a rtly on geographical position. A still more striking exam ple is provided by th e oilfields of th e P unjab. The oil recently found on th e south side of th e Soan syncline is a heavy asphaltic oil which contrasts sharply w ith th e more norm al crude of th e D hulian field on th e n o rth of th e syncline, although both oils come from th e same geological series and presum ably from th e same geological province.
I f in an y one of such instances th e physically different oils have indeed a common origin we should expect to find some characteristic common to th e oils b u t differentiating th em from others which h ad another origin.
* M an u scrip t receiv ed 8 th F e b ru a ry , 1945.
f P rofessor o f C h em istry , U n iv e rsity College o f Science a n d T echnology, C a lc u tta . j A ssam Oil C o m p an y R esearch Scholar, U n iv e rsity College o f Science a n d
T echnology, C a lc u tta . ■»
Again, th e oil from seepages is, n atu rally , often som ew hat different from th e oil still w ithin th e oilsands of th e sam e oilfield, an d th e u su al physical te sts m ay show little or no connection betw een th e tw o, b u t as th e origin is th e sam e, we should expect to have some distinctive characters present in each.
M any investigations have been m ade in to th is problem . One m ethod o f approach has been described by B arto n . H e sep arated each sam ple in to fractions boiling w ithin successive ranges of 25° C. a n d determ ined the specific gravities. T he graph connecting specific g ra v ity a n d boiling-point was term ed th e g rav ity -in terv al p a tte rn , a n d B a rto n ’s figures suggest t h a t w eathering h a d little effect on th e p a tte rn , w hich seem ed to be much th e sam e for oils believed to be of th e sam e origin, b u t differed w ith oils of different origin. I t is do u b tfu l w hether enough w ork has been done to dem o n strate th e reliability of m ethods of th is type.
Among oth er possibilities of finding a diagnostic characteristic are the detection of some elem ents presen t in v ery sm all qu an tities a n d th e recog
nition of unusual co m p o u n d s; th e use of infra-red rays is also proving to be a prom ising line o f research. I n each case it is only by prolonged investigation t h a t we can hope to distinguish ch aracters which depend on w h at m ay be term ed accidental v ariatio n s a ttrib u ta b le to th e later stages in th e h isto ry of th e crude from th e fu n d a m e n ta l differences diagnostic o f th e origin of th e crude.
I n a search for suitable m ethods, p articu larly ones w hich are rapid in application an d capable of em ploym ent w ith sm all q u an tities of m aterial, we have begun in C alcu tta a num b er of experim ents w ith ultra-violet fluorescence an d chrom atography. These hav e yielded interesting and prom ising results in th e differentiation of tru e oil-shows from spurious ones (w hether accidental or faked), although i t has n o t y e t been possible to ap p ly th e m ethods to oils from different geological provinces. The object of th is paper is to describe th e m ethods used an d give exam ples of th e results obtained, in th e hope t h a t criticism s an d suggestions will be forthcom ing.
There appear to be few published papers bearing on th e differentiation of crudes by fluorescence analysis, an d these were n o t available in C alcutta u n til our investigations h a d m ade considerable progress. O ur provisional program m e included a stu d y of th e effects of solvents, concentration, light filters, a n d fluorescence quenchers on th e fluorescence of various oils. We soon found th a t direct visual observation was insufficiently sensitive, and accordingly developed a technique based on c hrom atography a n d capillary analysis.
Pr e v i o u s Wo r k.
A. B entz an d R . S tro b e l2 exam ined th e fluorescence of a d rop of oil placed on filter pap er b en ea th a q u artz m ercury lam p. T h ey noticed th a t refined oils gave a blue fluorescence, w hilst th e crudes exam ined gave yellows an d browns. M elh ase3 applied fluorescence analysis to m any Californian crudes a n d noticed th a t oils from different sands show some difference in th e ir fluorescence. Since our presen t w ork was com pleted we have found th a t R . G rader 4 has described th e use of chrom atography for separating fractions of crude oil.
174 M U K H E R JE E A N D IN D R A : DIAG N O STIC CH A RA CTERISTICS OF
