U

. S

. D e pa r t m e n t o f I n t e r i o r

U

. S

. G e o l o gi c a l S ur v e y

C o m po s i t i o n o f c r ude o i l a n d na t ur a l ga s pr o duc e d f r o m 14 w e l l s i n t h e

L o w e r S i l ur i a n “ C l i n t o n ” s a n d s t o n e a n d M e d i na G r o up

,

n o r t h e a s t e r n O hi o a n d n o r t h

w e s t e r n P e nns yl va ni a

R

. C

. B ur r us s 1

a n d

R

. T

. R y

de r 1

O pe n

- F i l e R e po r t 03

- 409

T hi s r e po r t i s pr e l i m i na r y a n d ha s n ot b e e n r e vi e w e d f o r c o n f o r m i t y w i t h

U

. S

. G e o l o gi c a l S ur v e y e d i t o r i a l s t a n da r ds a n d s t r a t i gr a p hi c n o m e nc l a t ur e

. A ny us e o f t r a de n a m e s i s f o r de s c r i pt i v e pur po s e s o nl y a n d d o e s n ot i m p l y

e n do r s e m e n t by t h e U S G S

.

1 U

. S

. G e o l o g i c a l S ur v e y

, R e s t o n

, V i r g i ni a 20192C O N T E N T S

P a ge

I n

t r o duc t i o n

............................................. .............................. 1

S a m p l e L o c a t i o ns

.................................................................. 3

S a m p l i ng a n d A n a l y t i c a l M e t h o ds

................................................ 4

R e s u l t s

................................................... ............................... 5

N a t ur a l ga s e s

............................................. ..................... 5

C r ude o i l s

................................................ ..................... 7

P r e l i m i na r y C o n c l us i o ns

.............................. ............................... . 8

N a t ur a l ga s e s

............................................. ..................... 8

C r ude o i l s

................................................ ........................ 10

A c k n o w l e dg e m e n t s

................................................................... 13

R e f e r e n c e s C i t e d.......................................

............................... . 13

I L L U S T R A T I O N S

P a ge

F i gur e 1. M a p o f t h e L o w e r S i l ur i a n r e g i o na l o i l a n d ga s a c c u m u l a t i o n

s h o w i n g t h e l o c a t i o n o f t h e s t udy a r e a a n d r e g i o n a l c r o s s

s e c t i o n s A

- A ’ a n d D

- D ’

.............................. ............. . 18

F i gur e 2. C o r r e l a t i o n c ha r t o f L o w e r S i l ur i a n a n d a d j o i ni ng s t r a t a

,

n o r t h e a s t e r n O hi o

, n o r t h

w e s t e r n P e nn s yl va ni a

, a n d c e n t r a l

P e nn s yl va ni a s h o w i n g t h e i n t e r v a l o f t h e L o w e r S i l ur i a n

r e g i o n a l o i l a n d ga s a c c u m u l a t i o n

...... ............ ............. . 19

F i gur e 3. M a p s h o w i n g t h e w e l l l o c a t i o ns i n G e a uga a n d T r u m b u l l

C o un t i e s

, O hi o

, a n d M e r c e r a n d B ut l e r C o un t i e s

, P e nns yl va ni a

,

w h e r e o i l a n d ( o r ) ga s w a s s a m p l e d f o r t h e i nv e s t i g a t i o n

...... 20

iF i gur e 4. S c h o e l l ( 1983) d i a gr a m s h o w i n g t h e i s o t o pi c c o m p o s i t i o n

o f s e l e c t e d n a t ur a l ga s e s i n t h e l o w e r S i l ur i a n r e g i o n a l o i l a n d

ga s a c c u m u l a t i o n

....................................... ............. 21

F i gur e 5A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98O H 01B

, #2 P a t t e r s o n

............................................. ............ 22

F i gur e 5B

. S a t ur a t e d hy d r o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 01B

, #2 P a t t e r s o n

........................................... 23

F i gur e 5C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 01B

, #2 P a t t e r s o n

........................................... 24

F i gur e 6A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98O H 02 A

, #1 B r un o

................................................ ............ 25

F i gur e 6B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 02A

, #1 B r un o

.............................................. 26

F i gur e 6C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 02A

, #1 B r un o

.............................................. 27

F i gur e 7A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98O H 03 A

, #2 G r a n dvi e w

- J o hn s o n

................................. ............ 28

F i gur e 7B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 03A

, #2 G r a n d vi e w

- J o hn s o n

.................. ............. 29

F i gur e 7C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 03A

, #2 G r a n d vi e w

- J o hn s o n

.................. ............ 30

F i gur e 8A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98O H 04 A

, #1 D e t w e i l e r

....................................................... . 31

F i gur e 8B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 04A

, #1 D e t w e i l e r

.............................. ............ 32

F i gur e 8C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 04A

, #1 D e t w e i l e r

.............................. ............ 33

F i gur e 9A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98O H 05 A

, #2 H i s s a

............................................................. 34

i iF i gur e 9B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 05A

, #2 H i s s a

.................................... .......... . 35

F i gur e 9C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 05A

, #2 H i s s a

.................................... .......... . 36

F i gur e 10A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98O H 06 A

, #2 F r e n c h

.......................................... ...... .......... . 37

F i gur e 10B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 06A

, #2 F r e nc h

................................. ............ 38

F i gur e 10C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 06A

, #2 F r e nc h

................................. ............ 39

F i gur e 11A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98O H 07 A

, #3 G r i f f i n................................................

.......... . 40

F i gur e 11B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 07A

, #3 G r i f f i n.................................

............ 41

F i gur e 11C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 07A

, #3 G r i f f i n.................................

............ 42

F i gur e 12A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98O H 08, #1 B a t e s

. . . 43

F i gur e 12B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 08, #1 B a t e s

................................................. 44

F i gur e 12C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98O H 08, #1 B a t e s

................................................. 45

F i gur e 13A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98P A 02, #6 W e b e r

. . 46

F i gur e 13B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98P A 02, #6 W e b e r

................................................. 47

F i gur e 1 3C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98P A 02, #6 W e b e r

................................................. 48

F i gur e 14A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98P A 05 A

, # 8 O r i s

. . . 49

i i iF i gur e 14B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98P A 05 A

, #8 O r i s

................................................. 50

F i gur e 14C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98P A 05 A

, #8 O r i s

................................................. 51

F i gur e 15A

. W h o l e o i l ga s c h r o m a t o gr a m

, s a m p l e 98P A 06 A

, #2 G i bs o n

................................................ .......... . 52

F i gur e 15B

. S a t ur a t e d hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98P A 06 A

, #2 G i bs o n

................................. ............ 53

F i gur e 15C

. A r o m a t i c hy dr o c a r b o n f r a c t i o n ga s c h r o m a t o gr a m

, s a m p l e

98P A 06 A

, #2 G i bs o n

................................. ............ 54

F i gur e 16. P l o t o f pr / n C 17 v s

. ph / n C 18 f o r “ C l i n t o n ” / M e d i na o i l s

a n d U t i c a S h a l e bi t u m e n e x t r a c t s

.............................. 55

F i gur e 17. P l o t o f 1 3 C di s t r i b ut i o ns i n t h e s a t ur a t e d a n d a r o m a t i c hy dr o c a r b o n f r a c t i o n s f o r “ C l i n t o n ” / M e d i na o i l s a n d

U t i c a S h a l e bi t u m e n e x t r a c t s

........................ ............ 56

F i gur e 18A

. T e r pa n e m a s s f r a g m e n t o gr a m

, m / z 191. 180, s a m p l e

98P A 02, #6 W e b e r

................................................ 57

F i gur e 1 8B

. S t e r a n e m a s s f r a g m e n t o gr a m

, m / z 217. 1956 s a m p l e

98P A 02, #6 W e b e r

................................................ 58

i vT A B L E S

P a ge

T a bl e 1. W e l l s s a m p l e d f o r ga s a n d o i l i n n o r t h e a s t e r n O hi o a n d

n o r t h w e s t e r n P e n ns yl va ni a

........................... ............. 59

T a bl e 2A

. M o l e c u l a r a n d i s o t o pi c c o m po s i t i o n o f ga s s a m p l e s

.......... . 60

T a bl e 2B

. M o l e c u l a r a n d i s o t o pi c c o m po s i t i o n o f ga s s a m p l e s

.......... . 61

T a bl e 3. P r o pe r t i e s o f t h e w h o l e c r ude o i l a n d c r ude o i l f r a c t i o n s

...... 62

T a bl e 4. P r o pe r t i e s o f t h e s a t ur a t e d hy dr o c a r b o n f r a c t i o n o f t h e

c r ude o i l s

................................................ ............. 63

T a bl e 5. T e r pa n e a n d s t e r a n e c o m po un ds i de n t i f i e d i n t h e s a t ur a t e

f r a c t i o n o f t h e o i l i n t h e #6 W e b e r w e l l

............ ............. 64

v

.Introduction

The Lower Silurian regional oil and gas accum u lation was nam e d by Ryder and

Zagorski (2003) for a 400-m i -long by 200-m i -wide hydrocarbon accum u lation in the

central Appalachian basin of the eastern United States and Ontario, Canada (Figure 1).

The dom inant reservoirs in this regional accum u lation are the “Clinton” sandstone,

Medina Group sandstones, and Tuscarora Sandst one of Early Silurian age (Figure 2).

The basin-center gas (continuous) part of this regional Silurian accum u lation contains an

estim ated 30 trillion cubic f eet (TCF) of recoverable gas and covers an area that extends

across western Pennsylvania, eastern Ohio, and western W e st Virginia (Gautier and

others, 1995; Ryder, 1998). This part of the accum u lation occurs in rocks of low

perm eability, usually 0.1 m illidarcies (m d) or less, downdip of m o re perm eable, watersaturated rocks. A conventional part of the accum u lation with hybrid features of a basincenter accum u lation lies updip from the basin-center gas (Ryder, 1998; Ryder and

Zagorski, 2003). This hybrid-conventional part of the regional accum u lation follows a

pre-1980s production trend that extends fr om Ontario, Canada, through western New

York, northwestern Pennsylvania, and central Ohio (Figure 1).

In the basin-center part of the regional accum u lation, individual wells ultim ately

produce on the order of 50 to 450 m illion cubic feet (MMCF) of natural gas. In addition

to gas, m a ny wells produce variable am ounts of brine and crude oil. The gas-to-fluid

ratio is variable but generally high, on the order of 50,000 to 500,000 standard cubic feet

(SCF) of gas per barrel of oil or brine. Th e am ount of oil and brine produced affects the

econom ics of individual wells because of the cost incurred to dispose of the brine or the

1value added through the sale of oil. In general, the best gas producers are those wells that

produce the least oil and brine.

W e are investigating the geochem i stry of the gas and co-produced oil to better

understand the origin of the hydrocarbons within the Lower Silurian regional

accum u lation. This report docum ents 12 gas sam p les and 11 oil sam p les from 14 wells

producing from the “Clinton” sandstone and Grim sby/W h irlpool Sandstones in

northeastern Ohio and northwestern Pennsylvania. The sam p les from Ohio were

collected in Geauga and Trum bull Counties and those from Pennsylvania were collected

in Butler and Mercer Counties. This investigation supplem ents a previous data set of 10

oil sam p les and 3 gas sam p les collected from the “Clinton” sandstone in Trum bull

County (Barton, Burruss, and Ryder, 1998; Burruss and Ryder, 1998).

Other published analyses of crude oils and natural gases from Silurian-age

reservoirs in the Appalachian basin include those by Barker and Pollock (1984), Cole,

Drozd, and others (1987), Drozd and Cole (1994), Jenden, Drazan, and Kaplan (1993),

Laughrey and Baldassare (1998), Oberm a jer, Fowler, and Snowdon (1998), and Powell,

Macqueen, and others (1984). Cole, Drozd, and others (1987) recognized two groups of

oils in Silurian reservoirs in Ohio. One group of oil, they suggested, was generated from

m a rine black shale of Devonian age and the other group was generated from m a rine

black shale of Ordovician age. Most likely, oil in the Lower Silurian “Clinton” sandstone

was generated from the Ordovician black shale (Drozd and Cole, 1994; Ryder, Burruss,

and Hatch, 1998). Devonian black shale is a less likely source for the “Clinton” oils

because the 700-to-1,000-ft-thick Upper Silurian Salina Group, with evaporite beds, is

located between them (Figure 1). Molecular and isotopic data on natural gas from

2Silurian reservoirs in western and central Pennsylvania (Laughrey and Baldassare, 1998)

and western New York (Jenden, Drazan, a nd Kaplan, 1993) are less diagnostic for

identifying source rock than geochem i cal param e ters m easured in oil sam p les. However,

the general conclusion of work to date on “Clinton”/Medina/ Tuscarora gases is that they

were derived from therm a lly m a ture, m a rine organic m a tter, probably in strata older than

the Silurian.

Sample Locations

The wells sam p led f o r this investigation f o llow a northwest-southeast trend that is

subparallel to the dip of the basin and crosses the approxim a te boundary between basincenter and hybrid-conventional parts of the Lower Silurian regional accum u lation

(Figures 1, 3). In general, those wells east of Mosquito Creek Lake in central Trum bull

County are located in the basin-center part of the Lower Silurian regional accum u lation

whereas those wells west of Mosquito Creek Lake are located in the hybrid-conventional

part (Figure 3). All wells sam p led are within 5 m iles of cross section D-D’ that shows

the stratigraphic and depositional character of the “Clinton” sandstone and Medina Group

(Keighin, 1998) (Figure 3). Cross section A-A’ (Ryder, 2000), which connects with

cross section D-D’ in Mercer County, is located 5 to 10 m iles from the wells sam p led in

southeastern Mercer and northwestern Butler Counties (Figure 3). Also located in Figure

3 are 10 wells in Trum bull County for which oil and gas analyses have been reported by

Burruss and Ryder (1998). Selected inform ation on the wells sam p led for this

investigation is listed in Table 1.

3Sampling and Analytical Methods

Most oil and gas sam p les were obtained, with the assistance of operating

com p any field personnel, from the wellhead or the oil and gas separator of individual

wells. One oil sam p le was taken from the stock tank at the well site. Gas was sam p led at

the pressure gauge port on the production tubing using evacuated stainless steel cylinders

supplied by Isotech Laboratories, Inc. Oil was sam p led, where possible, at the drain for

the f l uid-level sightglass on the oil and gas separator. The oil is initially saturated with

gas at the separator pressure and foam s from exsolution of the gas as it exits the

sightglass drain. One oil sam p le was bailed from the stock tank.

All sam p les were analyzed by standard m e thods. Natural gas sam p les were

analyzed at Isotech Laboratories, Inc., Cham paign, Illinois, for m o lecular com position by

gas chrom a tography and for stable isotopic com position by isotope ratio m a ss

spectrom e try. Carbon isotopic com position was determ ined for m e thane (C 1 ), ethane

(C 2 ), propane (C 3 ), and iso-butane (C 4 ). Also, hydrogen isotopic com position was

determ ined for m e thane and nitrogen isotopic com position was determ ined for m o lecular

nitrogen. Carbon isotope ratios are reported in standard per m il deviation relative to the

Peedee belem n ite standard (PBS), and hydrogen isotope ratios are reported relative to

standard m ean ocean water (SMOW ) for both gases and oils. Nitrogen isotope ratios are

reported relative to atm o spheric nitrogen.

Crude oils were analyzed by the U.S. Geological Survey (Denver, Colorado).

API gravity of the oils was determ ined gravim etrically. Oils were fractionated by

dilution in n- heptane to rem ove asphaltenes. A concentrate of the solution was further

fractionated by colum n chrom a tography on silica gel by selective elution with heptane,

4benzene, and benzene-m e thanol (1:1 v/v) to collect the saturated hydrocarbon, arom atic

hydrocarbon, and resin (nitrogen-, sulfur-, and oxygen- [NSO] com pounds) fractions,

respectively. The carbon stable isotope com position of an aliquot of the saturated and

arom atic hydrocarbon fractions was determ ined on a Microm ass Optim a isotope ratio

m a ss spectrom e try system

.

Gas chrom a tography of the whole oil, and the saturated and arom atic hydrocarbon

fractions, was perform e d with a Hewlett/Packard Model 6890 (HP6890) gas

chrom a tograph with a 60 m x 0.32 m m x 0.25 μm DB-1 fused silica capillary colum n and

a FID detector. The oven was program m e d from 50 to 330°C at 4.5°C/m i n and held

isotherm al at 330°C for 15 m i n with helium carrier gas flow at 35 cm /sec. Gas

chrom a tography-m a ss spectrom e try (GCMS) of the saturated hydrocarbon fraction of one

oil was perform e d with a HP6890-JEOL GCMate system in selective ion m onitoring

m ode to identify steranes and terpanes in the fraction.

5Results

Natural gases: The m o lecular and isotopic com position of natural gas from twelve wells

is presented in Tables 2A and 2B. All twelve gases are rich in m e thane, between 76 and

90 m o le %, with low concentrations of hydrocarbons that have m o re than four carbon

atom s. All sam p les contain a trace of helium and 2.01 to 4.55 m o le % nitrogen. Eight of

the twelve wells contain a trace of hydrogen. These gas com positions are consistent with

gas com positions reported for the “Clinton” sandstone in Ohio by the U.S. Bureau of

Mines (Moore, 1982).

The carbon isotopic com position of m e thane, ethane, propane, and n- butane in the

sam p les ranges from about 7 to 12 per m il for each com ponent. In eight of twelve wells,

the carbon isotopic com position of m e thane, ethane, propane, and n- butane (where

analyzed) becom e respectively heavier as norm a lly expected (Chung, Gorm ly, and

Squires, 1988) whereas, in four wells, the carbon isotopic com position of m e thane,

ethane, propane, and n- butane (where analyzed) show several com b inations of reversal in

the norm a l trend (see #5 Brown; table 2B). The variation in the hydrogen isotopic

com position of m e thane is about 50 per m il and the variation in the nitrogen isotopic

com position ranges is about 4 per m il. The carbon dioxide content in the sam p les was so

low, 0.04 m o le % or less, that the carbon isotopic com position of this constituent could

not be determ ined.

Judging from their isotopic location on a Schoell (1983) diagram (Figure 4),

“Clinton”/Medina natural gases from this study and from Burruss and Ryder (1998) are

therm ogenic in origin. The δ 13 C m e thane and δ D m e thane values define a straight line

that indicates that the gases becom e isotopically heavier with depth of production (Figure

64). For exam ple, δ 13 C m e thane values range from -41.98 in the #2 Patterson well (~3,600

ft to the gas production) near the northwest end of section D-D’ to –33.97 in the #2

Mathews well (~6,570 ft) near the southeast end. Isotopic com positions of additional

Lower Silurian gases from northwestern Pe nnsylvania (Laughrey and Baldassare, 1998)

and Lower Silurian gases from New York (Jenden, Drazan, and Kaplan, 1993) also fit the

trend defined in Figure 4. Natural gases in the basin-center part of the regional

accum u lation are differentiated from natural gases in the hybrid-conventional part based

on their position relative to the δ 13 C m e thane = -37.0 value (Figure 4).

Crude oils: Bulk param e ters and selected m o lecular param e ters of the crude oils are

listed in Table 3. The API gravity of 8 of the 11 sam p les is 40° or greater. One of the 3

exceptions, the No. 6 W e ber well with an API gravity of 39.9°, was bailed from the top

of the stock tank instead of being collected at the separator. The oils are uniform ly high

(84 to 92 wt. %) in saturated hydrocarbons with 12% or less of arom atic hydrocarbons.

Carbon isotopic com positions of the saturated and arom atic hydrocarbon fractions show

sm all ranges of 0.8 per m il and 1.0 per m il, respectively.

Gas chrom a togram s of the whole oil, saturated hydrocarbon, and arom atic

hydrocarbon fractions for sam p les from the 11 wells are shown in Figures 5A, 5B, 5C,

respectively, through Figures 15A, 15B, 15C. The saturated hydrocarbon gas

chrom a togram s have sim ilar characteristics to “Clinton” oils reported by Cole, Drozd,

and others (1987). Molecular param e ters derived from the gas chrom a togram s of the

saturated hydrocarbon fractions are listed in Table 4. All whole-oil gas chrom a togram s

of the saturated hydrocarbon fraction, except the one from the #6 W e ber well, show a full

7spectrum of n- alkanes from n- C 10 to n- C 30+ . The whole oil chrom a togram for the sam p le

from the #6 W e ber well shows depletion in the low carbon num ber range (< n- C 10 )

suggesting evaporative loss of the light ends. Two types of n- alkane distributions and

one interm ediate type are recorded by the saturated fraction gas chrom a togram s.

Including the depleted #6 W e ber sam p le, six of the eleven chrom a togram s show a broad

spectrum of n- alkanes whose peak heights progressively dim i nish toward the higher

carbon num bers (Figure 8B); two chrom a togram s have a bim odal distribution of nalkanes that peak at about n- C 14 and n- C 24 (Figure 6B); and three chrom a togram s show a

broad spectrum of n- alkanes whose peak heights progressively dim i nish toward the

higher carbon num bers but show a secondary peak at n- C 24 (Figure 11B). Both types of

n- alkane distribution show a m odest odd-carbon preference and the presence of

isoprenoids. The pristane/phytane (pr/ph) ratios listed in Table 4 range from 1.31 to 2.01.

Crude oils from “Clinton”/Medina reservoirs in this study and in Burruss and

Ryder (1998) are characterized by pr/ n- C 17 and ph/ n- C 18 values that vary broadly with

their depth of production (Figure 16). Major exceptions are sam p le 14 (#6 W e ber) that is

grouped with oils produced from m u ch shallower depths and sam p le 6 (#3 Griffin) that is

grouped with oils produced from m u ch greater depths (Figure 16). Moreover, carbon

isotopic com positions of the saturated and arom atic fractions of the oils, in general,

becom e heavier with depth (Figure 17). Basin-center and hybrid-conventional parts of

the regional accum u lation can be largely differentiated on the basis of trends shown in

Figures 16 and 17.

Mass fragm e ntogram s from gas chrom a tography-m a ss spectrom e try (GCMS) of

the crude oil sam p les indicate the presence of biom arkers although m a ny are barely

8visible because of their low signal-to-noise ratio. Surprisingly, the best fragm e ntogram s

are from the depleted oil in the #6 W e ber well. Terpane (m /z 191) and sterane (m /z 217)

fragm e ntogram s of this oil are shown in Figures 18A and 18B, respectively.

Preliminary Conclusions

Natural gases: The striking distribution of δ 13 C m e thane vs. δ D m e thane com positions is

clearly a function of the therm a l m a turity of the gases (Figure 4). In addition, given the

orderly increase toward heavier isotopes with depth, there appears to have been very little

m i xing of the gases in the “Clinton”/Medina reservoirs after entrapm e nt. Also, these data

im ply a com m on source rock for the gases. Several explanations are possible for the

isotopic distributions shown in Figure 4. First, gases m a y have been introduced to

Lower Silurian reservoirs from a distant source, becam e trapped, and then therm a lly

m odified, in situ , as the reservoirs gradually achieved m a xim u m burial. Secondly, gases

m a y have been introduced from a local source rock and then trapped before it was

allowed to m i grate laterally. In these two m odels, the gases had m i nim a l m obility during

late-stage basin uplift. A third m odel suggests that the isotopic character of the gases is a

late-stage, leakage/fractionation phenom enon whereby the volum e of the escaped gas is

directly related to the thickness of overburden. Therefore, isotopic com positions would

be heaviest in gases having the greatest overburden thickness.

Furtherm ore, conodont alteration index (CAI) isograds for Middle Ordovician

carbonate rocks (Repetski and others, 2002; J.E. Repetski and R.T. Ryder, unpubl. data)

show a consistently lower therm a l m a turity value, f o r a given locality, than that of the gas

(Jenden, Drazan, and Kaplan, 1993) (Figure 4) . Figure 4 suggests that gases in the

9“Clinton”/Medina were derived from source rocks having therm a l m a turity values about

1 to 1.5 vitrinite reflectance equivalence (VRE) (Nöth, 1991) greater than the therm a l

m a turity of the underlying Middle Ordovician strata based on CAI isograds. A sim ilar

discrepancy occurs when the therm a l m a turity of the gases are com p ared with the therm a l

m a turity of the overlying Lower/Middle Devonian strata based on CAI isograds and

vitrinite reflectance (Ro%) isoreflectance lines.

The fact that these gases have a significantly higher therm a l m a turity than the

underlying Ordovician and overlying Devonian stra ta suggests that they m i grated from

deeper in the basin. Moreover, a Utica Shale source rock is favored over a Devonian

shale source rock because of the shorter m i gration distance (25 to 50 m i vs. >100 m i ) that

the Utica requires to account for the observed therm a l m a turity of the gases. Although

these data are m o st consistent with m odel 1 for the origin of the gases (m edium -range

m i gration with isotopic signatures being set during m a xim u m burial), m odel 3 (m edium

range m i gration with isotopic signatures being set during late-stage uplift and erosion of

the basin) cannot be rejected. Methane δ 13 C > ethane δ 13 C values observed in several

natural gases in this study (Table 2B) m a y have resulted from the m i xing of m a ture and

post-m a ture gases (Jenden, Drazan, and Kaplan, 1993; Laughrey and Baldassare, 1998);

however, diffusive leakage of gas through overburden rock (as perm itted in m odel 3)

m a y be an alternate explanation (Laughrey and Baldassare, 1998).

Crude oils: The m a jority of n- alkane distributions for whole-oil gas chrom a togram s in

this investigation (Figures 6A-13A and 15A) show: 1) a broad spectrum of n- alkanes

ranging from n- C 10 through n- C 35 , 2) m odest odd-carbon preference in the n- C 15 through

10n- C 19 range, and 3) the presence of isoprenoids pristane and phytane. The m a jor

exception to the rule is the oil from the #6 W e ber well (Figure 13A) which has an

incom p lete spectrum of n- alkanes ( n- C 10 and n- C 11 are nearly depleted) and lacks oddcarbon predom inance in the n- C 15 through n- C 19 range. As noted earlier, the

characteristics of the #6 W e ber oil were probably caused by evaporative loss during

sam p ling and storage.

The oils analyzed in this investigation have the sam e basic com position as other

oils from the “Clinton” reservoir in Ohio (Cole, Drozd, and others, 1987; Burruss and

Ryder, 1998) and oils from Cam b rian/Ordovici an reservoirs in Ohio (Cole, Drozd, and

others, 1987; Ryder, Burruss, and Hatch, 1998). These basic sim ilarities suggest a

com m on source rock, probably the Middle Ordovician Utica Shale, for the “Clinton” and

Cam b rian/Ordovician reservoirs (Cole, Dr ozd, and others, 1987; Ryder, Burruss, and

Hatch, 1998). Geochem i cal and geological evidence are m u ch less convincing for other

source rocks such as the Lower/Middle Devonian black shale and Silurian

shale/carbonate units (Ryder and Zagorski, 2003).

CAI isograds for Middle Ordovician carbonates gradually increase eastward

across the study area from 1.5 to 2.0 (VRE 0.5 to 1) (Repetski and others, 2002; J.E.

Repetski and R.T. Ryder, unpubl. data). These isograds are indicative of the “window”

of oil and wet gas generation and preservation and, thus, are perm issive of local

derivation of the oils from the Utica Shale. Also, local oil derivation from the Utica is

suggested by the sim ilarity of carbon isotopic distributions in Utica Shale extracts from

Coshocton County, Ohio (Figure 3) (depth = 5,600-5,700 ft) and “higher” m a turity oils

from “Clinton” reservoirs (Figure 17). Moreover, the general eastward (basinward)

11increase in therm a l m a turity of the oils, based on pr/ n- C 17 vs. pr/ n- C 18 (Figure 16) and

carbon isotopic distributions (Figure 17), suggests that m i nim a l lateral m i gration of oil

had occurred before entrapm e nt.

Oil from the #6 W e ber well is anom alous because it is geochem i cally associated

with “lower” m a turity oils (Figure 16) and is geologically associated with the CAI 3

isograd (VRE 2.25) (Repetski and others, 2002) that signifies the “window” of dry gas

generation and preservation. Either this oil was introduced from a lower m a turity source

rock such as the overlying Devonian black shale or was locally preserved in a relatively

high therm a l regim e that favored the generation and preservation of dry gas. In contrast,

oil from the #3 Griffin well at a depth of a bout 3,900 ft is geochem i cally associated with

“higher” m a turity oils whose depth of production is approxim a tely 1,000 ft greater

(Figures 16 and 17). Possibly this oil m i grated into the vicinity of the #3 Griffin well

from deeper in the basin, or from a m o re m a ture secondary phase of generation that

occurred beneath the well, and was trapped next to the lower m a turity oil. Additional

evidence for the m i xing of different several oil types — either caused by a different

source rock or therm a l m a turity regim e — is suggested by the bim odal n- alkane

distributions noted in several oils (see Figure 6B).

The following sequence of events represents one scenario for the origin of the

oils: 1) oil generation from the Utica Shale, 2) vertical m i gration of the oil into the

overlying “Clinton”/Medina reservoir, 3) probable entrapm e nt of the oil before

significant lateral m i gration had occurred, and 4) local m i xing of oils from disparate

therm a l regim e s during late-stage basin uplift and erosion. This scenario suggests that

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. , 199 8, B l a c k s h a l e s o ur c e r o c ks a n d o i l

ge n e r a t i o n i n t h e C a m b r i a n a n d O r do vi c i a n o f t h e c e n t r a l A ppa l a c hi a n b a s i n, U S A :

A m e r i c a n A s s o c i a t i o n o f P e t r o l e u m G e o l o g i s t s B ul l e t i n

, v

. 82, p

. 412

- 441.

17Figure 1. Map of the lower Silurian regional oil and gas accumulation showing the

location of the study area and cross sections A-A' and D-D'.

18Figure 2. Correlation chart of Lower Silurian and adjoining strata, northeastern Ohio. northwestern Pennsylvania,

and central Pennsylvania, showing the interval of the Lower Siurian regional and gas accumulation.

19Figure 3. Map of the study area in northeastern Ohio and northwestern Pennsylvania showing well locations in Geauga and Trumbull Counties, Ohio,and Mercer and Butler Counties, Pennsylvania, where oil and (or) gas was sampled for this ivnestigation and the Burruss and Ryder (1998) investigation.

20Figure 4. Schoell (1983) diagram showing the isotopic composition of selected natural gases in the Lower

Silurian regional oil and gas accumulation. A scale devised by Jenden and others (1993) for estimating the

approximate vitrinite reflectance (%Ro) of the source rock that generated the gas is attached to the right side

of the diagram. Also shown are the CAI thermal maturity values for Middle Ordovician carbonate rocks located

near the proposed Middle Ordovician Utical Shale source rock.

CAI - Conodont alteration index; VRE - Vitrinite reflectance equivalence based on N **ο** th (1991); BC - Basin-center

part of the regional accumulation; HC - Hybrid-conventional part of the regional accumulation.

2122



### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

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, s a m p l e 9 8 O H 0 1 B

, # 2 P a t t e r s o n

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

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, p r i s t a n e ; p h

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. 8

p r

p h n

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n

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p h

1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 5 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 1 B

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. 

### S a t u r a t e d h y d r o c a r b o n s



### # 2 P a t t e r s o n

A P I g r a v i t y : 4 2

. 823

### 1 0 2 0 3 0 4 0 5 0 6 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 5 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 1 B

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. 

### A r o m a t i c h y d r o c a r b o n s



### # 2 P a t t e r s o n

A P I g r a v i t y : 4 2

. 824

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 6 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 2 A

, # 1 B r u n o

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l a l k a n e s

w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

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# 1 B r u n o

A P I g r a v i t y : 4 1

. 4

p r

p h n

- C 1 7 m e t h y l c y c l o h e x a n e

n

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n

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- C 725

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 6 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 2 A

, # 1 B r u n o

. 

### S a t u r a t e d h y d r o c a r b o n s



### # 1 B r u n o

A P I g r a v i t y : 4 1

. 4



### p r

p h26

### 1 0 2 0 3 0 4 0 5 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 6 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 2 A

, # 1 B r u n o

. 

### A r o m a t i c h y d r o c a r b o n s



### # 1 B r u n o

A P I g r a v i t y : 4 1

. 427

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 7 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 3 A

, # 2 G r a n d v i e w

- J o h n s o n

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l

a l k a n e s w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

. 

### W h o l e o i l

# 2 G r a n d v i e w

- J o h n s o n

A P I g r a v i t y : 4 0

. 7

p r

p h n

- C 1 7

m e t h y l c y c l o h e x a n e

n

- C 1 0

n

- C 3 0 n

- C 728

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 7 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 3 A

, # 2 G r a n d v i e w

- J o h n s o n

. 

### S a t u r a t e d h y d r o c a r b o n s



### # 2 G r a n d v i e w

- J o h n s o n

A P I g r a v i t y : 4 0

. 7



### p r

p h29

### 1 0 2 0 3 0 4 0 5 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 7 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 3 A

, # 2 G r a n d v i e w

- J o h n s o n

. 

### A r o m a t i c h y d r o c a r b o n s



### # 2 G r a n d v i e w

- J o h n s o n

A P I g r a v i t y : 4 0

. 730

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 8 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 4 A

, # 1 D e t w e i l e r

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l a l k a n e s

w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

. 

### W h o l e o i l

# 1 D e t w e i l e r

A P I g r a v i t y : 4 3

. 8

p r

p h n

- C 1 7

m e t h y l c y c l o h e x a n e

n

- C 1 0

n

- C 3 0 n

- C 731

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 8 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 4 A

, # 1 D e t w e i l e r

. 

### S a t u r a t e d h y d r o c a r b o n s



### # 1 D e t w e i l e r

A P I g r a v i t y : 4 3

. 8



### p r

p h32

### 1 0 2 0 3 0 4 0 5 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 8 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 4 A

, # 1 D e t w e i l e r

. 

### A r o m a t i c h y d r o c a r b o n s



### # 1 D e t w e i l e r

A P I g r a v i t y : 4 3

. 833

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 9 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 5 A

, # 2 H i s s a

, c o l l e c t e d f r o m a s e p a r a t o r t h a t a l s o s e r v e s t h e # 1 H i s s a

w e l l

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l a l k a n e s w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

. 

### W h o l e o i l

# 2 H i s s a

A P I g r a v i t y : 4 2

. 8

p r

p h n

- C 1 7 m e t h y l c y c l o h e x a n e

n

- C 1 0

n

- C 3 0 n

- C 734

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 9 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 5 A

, # 2 H i s s a

, c o l l e c t e d f r o m a s e p a r a t o r

t h a t a l s o s e r v e s t h e # 1 H i s s a w e l l

. . 

### S a t u r a t e d h y d r o c a r b o n s



### # 2 H i s s a

A P I g r a v i t y : 4 2

. 8



### p r

p h35

### 1 0 2 0 3 0 4 0 5 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 9 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 5 A

, # 2 H i s s a

, c o l l e c t e d f r o m a s e p a r a t o r

t h a t a l s o s e r v e s t h e # 1 H i s s a w e l l

. 

### A r o m a t i c h y d r o c a r b o n s



### # 2 H i s s a

A P I g r a v i t y : 4 2

. 836

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 0 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 6 A

, # 2 F r e n c h

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l a l k a n e s

w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

. 

### W h o l e o i l

# 2 F r e n c h

A P I g r a v i t y : 4 3

. 0

p r

p h n

- C 1 7 m e t h y l c y c l o h e x a n e

n

- C 1 0

n

- C 3 0 n

- C 737

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 0 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 6 A

, # 2 F r e n c h

. 

### S a t u r a t e d h y d r o c a r b o n s



### # 2 F r e n c h

A P I g r a v i t y : 4 3

. 0



### p r

p h38

### 1 0 2 0 3 0 4 0 5 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 0 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 6 A

, # 2 F r e n c h

. 

### A r o m a t i c h y d r o c a r b o n s



### # 2 F r e n c h

A P I g r a v i t y : 4 3

. 039

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 1 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 7 A

, # 3 G r i f f i n

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l a l k a n e s

w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

. 

### W h o l e o i l

# 3 G r i f f i n

A P I g r a v i t y : 3 3

. 8

p r

p h n

- C 1 7 m e t h y l c y c l o h e x a n e

n

- C 1 0

n

- C 3 0 n

- C 740

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 1 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 7 A

, # 3 G r i f f i n

. 

### S a t u r a t e d h y d r o c a r b o n s



### # 3 G r i f f i n

A P I g r a v i t y : 3 3

. 8



### p r

p h41

### 1 0 2 0 3 0 4 0 5 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 1 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 7 A

, # 3 G r i f f i n

. 

### A r o m a t i c h y d r o c a r b o n s



### # 3 G r i f f i n

A P I g r a v i t y : 3 3

. 842

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 2 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 8

, # 1 B a t e s

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l a l k a n e s

w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

. 

### W h o l e o i l

# 1 B a t e s

A P I g r a v i t y : 4 2

. 9

p r

p h n

- C 1 7 m e t h y l c y c l o h e x a n e

n

- C 1 0

n

- C 3 0 n

- C 743

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 2 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 8

, # 1 B a t e s

. 

### S a t u r a t e d h y d r o c a r b o n s



### # 1 B a t e s

A P I g r a v i t y : 4 2

. 9



### p r

p h44

### 1 0 2 0 3 0 4 0 5 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 2 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 O H 0 8

, # 1 B a t e s

. 

### A r o m a t i c h y d r o c a r b o n s



### # 1 B a t e s

A P I g r a v i t y : 4 2

. 945

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 3 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 P A 0 2

, # 6 W e b e r

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l a l k a n e s

w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

. 

### W h o l e o i l

# 6 W e b e r

A P I g r a v i t y : 3 9

. 9

p r

p h n

- C 1 7

n

- C 1 0 n

- C 3 046

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 3 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 P A 0 2

, # 6 W e b e r

. 

### S a t u r a t e d h y d r o c a r b o n s



### # 6 W e b e r

A P I g r a v i t y : 3 9

. 9



### p r

p h47

### 1 0 2 0 3 0 4 0 5 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 3 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 P A 0 2

, # 6 W e b e r

. 

### A r o m a t i c h y d r o c a r b o n s



### # 6 W e b e r

A P I g r a v i t y : 3 9

. 948

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 4 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 P A 0 5 A

, # 8 O r i s

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l a l k a n e s

w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

. 

### W h o l e o i l

# 8 O r i s

A P I g r a v i t y : 4 5

. 5

p r

p h n

- C 1 7 m e t h y l c y c l o h e x a n e

n

- C 1 0

n

- C 3 0 n

- C 749

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 4 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 P A 0 5 A

, # 8 O r i s

. 

### S a t u r a t e d h y d r o c a r b o n s



### # 8 O r i s

A P I g r a v i t y : 4 5

. 5



### p r

p h50

### 1 0 2 0 3 0 4 0

R e t e n t i o n T i m e

, m i n u t e s 5 0 6 0

F i g u r e 1 4 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 P A 0 5 A

, # 8 O r i s

. 

### A r o m a t i c h y d r o c a r b o n s



### # 8 O r i s

A P I g r a v i t y : 4 5

. 551

### 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 5 A : W h o l e o i l g a s c h r o m a t o g r a m

, s a m p l e 9 8 P A 0 6 A

, # 2 G i b s o n

. S e l e c t e d p e a k i d e n t i f i c a t i o n s : 

### n

- C X

, n o r m a l a l k a n e s

w h e r e X i s t h e c a r b o n n u m b e r ; p r

, p r i s t a n e ; p h

, p h y t a n e

. 

### W h o l e o i l

# 2 G i b s o n

A P I g r a v i t y : 3 8

. 8

p r

p h n

- C 1 7

m e t h y l c y c l o h e x a n e

n

- C 1 0

n

- C 3 0 n

- C 752

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 5 B : S a t u r a t e d h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 P A 0 6 A

, # 2 G i b s o n

. 

### S a t u r a t e d h y d r o c a r b o n s



### # 2 G i b s o n

A P I g r a v i t y : 3 8

. 8



### p r

p h53

### 1 0 2 0 3 0 4 0 5 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 5 C : A r o m a t i c h y d r o c a r b o n f r a c t i o n g a s c h r o m a t o g r a m

, s a m p l e 9 8 P A 0 6 A

, # 2 G i b s o n

. 

### A r o m a t i c h y d r o c a r b o n s



### # 2 G i b s o n

A P I g r a v i t y : 3 8

. 854Figure 16. Plot of pr/n-C17 vs. ph/n-C18 for "Clinton"/Medina oils and Utica Shale bitumen extracts. BC - Basin-center part ofthe regional accumulation; HC - Hybrid-conventional part of the regional accumulation.

55Figure 17. Plot of **δ** 13 C distributions in the saturated and aromatic hydrocarbon fractions for "Clinton"/Medina

oils and Utica Shale bitumen extracts. BC - Basin-center part of the regional accumulation; HC - Hybrid-conventional

part of the regional accumulation.

56

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 8 A : T e r p a n e m a s s f r a g m e n t o g r a m

, m / z 1 9 1

. 1 8 0

, s a m p l e 9 8 P A 0 2

, # 6 W e b e r

. 

### T e r p a n e s

# 6 W e b e r

C 2 1 C 2 3 C 2 4 C 2 5 C 2 8 a

, b C 2 9 a

, b A B D

E F

G H

I

K

L M

N O P T r i c y c l i c t e r p a n e s P e n t a c y c l i c t r i t e r p a n e s57

### 1 0 2 0 3 0 4 0 5 0 6 0 7 0

R e t e n t i o n T i m e

, m i n u t e s

F i g u r e 1 8 B : S t e r a n e m a s s f r a g m e n t o g r a m

, m / z 2 1 7

. 1 9 5 6

, s a m p l e 9 8 P A 0 2

, # 6 W e b e r

. 

### S t e r a n e s

# 6 W e b e r

1

2

3 5 a

, b

7 a

, b 8

1 0

1 2 1 3

, 1 4

, 1 5

1 6

, 1 7

, 1 858Perforation DepthSample IDWell NameOperatorAPInumberOhioorPa.County/Townshipor71⁄2 quad.ProducingFormationTop,ftBottom,ftTotalDepth,ft.SampleOil SamplePoint98OH01#2PattersonRangeRes.3405521619Geagua/Chester“Clinton”sandstone358836113720gas,oilsightglass98OH02#1BrunoRangeRes.3405520490Geauga/Claridon“Clinton”sandstone379538443993gas,oilsightglass98OH03#2GrandviewJohnsonRangeRes.3405520285Geauga/Claridon“Clinton”sandstone390639624098gas, oilsightglass98OH04#1DetweilerRangeRes.3405520818Geauga/Middlefield“Clinton”sandstone394339794150gas,oilsightglass98OH05#2HissaRangeRes.3405521083Geauga/Huntsburg“Clinton”sandstone379738974015gas,oilsightglass98OH06#2FrenchRangeRes.3415522716Trumbull/Mesopotamia“Clinton”sandstone372338783950gas,oilsightglass98OH07#3GriffinRangeRes.3415522594Trumbull/Bloomfield“Clinton”sandstone375438624047gas,oilsightglass98OH08#1BatesRangeRes.3415522553Trumbull/Bloomfield“Clinton”sandstone381538954085oilsightglass98PA01#5BrownAtlasRes.3708521979Mercer/Grove CityGrimsby/Whirlpool62886416632864266582gasoilnotavailable98PA02# 6 WeberAtlasRes.3708521992Mercer/Grove CityGrimsby/Whirlpool63556477637364876637oilstocktank98PA03#1VelisarisAtlasRes.3701921358Butler/Grove CityGrimsby/Whirlpool65206584656865946714gasoil notavailable98PA04#2MathewsAtlasRes.3701921352Butler/BarkeyvilleGrimsbySandstone656465746775gasoilnotavailable98PA05#8OrisRangeRes.3708522239Mercer/SharpsvilleGrimsby/Whirlpool478349445086gas,oilsightglass98PA06#2GibsonRangeRes.3708521263Mercer/SharpsvilleGrimsbySandstone495850215180gas,oilsightglass

59Table 1.Wellssampledfor gasandoilinnortheasternOhioand northwesternPennsylvania.SampleID98OH01A98OH02B98OH03B98OH04B98OH05B98OH06BWell Name#2Patterson#1Bruno#2GrandviewJohnson#1Detweiler#2Hissa#2FrenchMolecular Analysis,mole%Methane78.0385.6288.1088.1776.3887.48Ethane9.706.185.305.5810.985.59EthylenendndndndndndPropane4.822.562.161.936.072.12iso-Butane0.600.360.360.281.060.33n-Butane1.330.730.720.512.010.63iso-Pentane0.300.190.210.140.600.17n-Pentane0.300.170.180.120.520.15Hexanes+0.220.160.230.110.280.14Helium0.140.120.110.100.0690.12Hydrogen0.013nd0.00470.00280.00440.0067ArgonndndndndndndOxygenndndndndndndNitrogen4.553.912.633.042.013.24CarbonDioxidendndnd0.020.020.02Isotopic Analysis, permilMethane,δ13C-41.98-39.17-38.06-38.76-39.83-38.78δD-201.9-174.1-167.3-174.3-181.9-174.6Ethane,δ13C-35.26-33.76-34.62-35.12-35.16-35.26Propane,δ13C-32.34-31.10-30.81-30.90-31.18-31.05n-Butane,δ13C-30.68nd-29.52ndndndNitrogen,δ15N-4.92nd-2.98ndndnd

60Table2A. Molecular and isotopic composition ofgas samples.nd:notdetectedSampleID98OH07B98PA0198PA0398PA0498PA05B98PA06BWell Name#3Griffin#5Brown#1Velisaris#2Mathews#8Oris#2GibsonMolecular Analysis,mole%Methane88.1994.3694.2594.0289.9491.74Ethane5.172.372.262.234.583.67EthylenendndndndndndPropane1.870.150.140.131.350.87iso-Butane0.260.0170.0150.0140.220.13n-Butane0.510.0220.0170.0170.360.25iso-Pentane0.130.0090.00730.00700.110.0780n-Pentane0.12ndndnd0.0890.061Hexanes+0.0980.0150.0090.00870.160.087Helium0.110.0870.090.0870.100.097Hydrogennd0.01ndnd0.00240.012ArgonndndndndndndOxygenndndndndndndNitrogen3.542.923.173.453.082.99CarbonDioxidend0.040.040.030.010.02Isotopic Analysis, permilMethane,δ13C-38.75-34.69-34.19-33.97-36.90-35.58δD-175.3-152.3-153.3-150.8-167.3-159.8Ethane,δ13C-35.58-39.75-41.14-41.15-35.32-35.98Propane,δ13C-31.34-40.17-42.85-42.81-30.61-30.74n-Butane,δ13C-29.84nd-38.89ndnd-29.24Nitrogen,δ15N-1.31nd-5.14ndnd-5.00

61Table2B. Molecular andisotopic composition ofgas samples.nd:notdetectedSample ID Well name API

gravity Petroleum Fractions,

wt. % Isotopic Composition,

per mil

Sat

HC Aro

HC NSOs Asph Sat HC, δ 13 C Aro HC, δ 13 C

98OH01B #2 Patterson 42.8 84.46 10.72 2.91 1.90 -30.22 -29.74

98OH02A #1 Bruno 41.4 85.21 12.10 2.58 0.11 -30.08 -29.40

98OH03A #2 Grandview

- Johnson 40.7 85.20 11.08 3.24 0.48 -30.16 -29.37

98OH04A #1 Detweiler 43.8 86.85 9.04 3.55 0.56 -29.95 -29.01

98OH05A #2 Hissa 42.8 86.71 8.72 4.08 0.49 -30.17 -29.37

98OH06A #2 French 43.0 84.40 11.36 3.55 0.70 -30.09 -29.16

98OH07A #3 Griffin 33.8 88.03 9.26 2.43 0.29 -30.08 -29.23

98OH08 #1 Bates 42.9 87.36 8.67 3.24 0.73 -30.01 -29.17

98PA02 #6 Weber 39.9 89.39 2.21 1.20 7.21 -29.60 -28.72

98PA05A #8 Oris 45.5 91.81 2.84 4.97 0.39 -29.60 -29.00

98PA06A #2 Gibson 38.8 92.96 4.27 2.37 0.39 -29.47 -28.80

Table 3. Properties of the whole crude oil and crude oil fractions. Sat HC: saturated hydrocarbons;

Aro HC: aromatic hydrocarbons; NSOs: Nitrogen, sulfur, oxygen-bearing organics; asph: asphaltenes.

62Saturated HC characteristics

Sample ID Well name pr/ph pr/n-C 17 ph/n-C 18 CPI % n-alk Cond.

index

98OH01B #2 Patterson 1.33 0.38 0.33 1.07 7.73 9.72

98OH02A #1 Bruno 1.35 0.41 0.34 0.96 17.93 5.49

98OH03A #2 GrandviewJohnson 1.36 0.40 0.33 0.99 24.58 7.21

98OH04A #1 Detweiler 1.36 0.41 0.34 1.00 10.21 9.82

98OH05A #2 Hissa 1.32 0.36 0.31 0.96 14.92 8.60

98OH06A #2 French 1.38 0.38 0.32 1.04 17.95 10.81

98OH07A #3 Griffin 1.31 0.27 0.23

98OH08 #1 Bates 1.31 0.43 0.38 1.06 6.35 9.51

98PA02 #6 Weber 1.44 0.40 0.38 1.05 14.93 3.04

98PA05A #8 Oris 1.94 0.29 0.19 1.03 18.74 8.23

98PA06A #2 Gibson 2.01 0.28 0.17 1.02 20.40 5.99

Table 4. Properties of the saturated hydrocarbon fraction of the crude oils. These properties were

calculated on the basis of peak area from analyses performed on April 1999. pr/ph: pristane/phytane;

CPI: carbon preference index; % n-alk: % of n-alkanes in total saturate fraction; Cond. Index: condensate

index defined by Lewan and Buchardt (1989), % n-C 11 of n-C 10 to n-C 30 . CPI, % n-alk, and cond. Index

were not calculated for the #3 Griffin oil sample.

63Table 5. Terpane and sterane compounds identif ied in the saturate fraction of the oil

from the #6 Weber well.

Molecular

Label Formula Compound

Tricyclic Terpanes

C 21 C 21 H 38 C 21 tricyclic terpane

C 23 C 23 H 42 C 23 tricyclic terpane

C 24 C 24 H 44 C 24 tricyclic terpane

C 25 C 25 H 46 C 25 tricyclic terpane

C 28a C 28 H 50 C 28 [22S] tricyclic terpane

C 28b C 28 H 50 C 28 [22R] tricyclic terpane

C 29a C 29 H 52 C 29 [22S] tricyclic terpane

C 29b C 29 H 52 C 29 [22R] tricyclic terpane

Pentacyclic Triterpanes

A C 27 H 46 18 α trisneonorhopane [Ts]

B C 27 H 46 17 α trisneonorhopane [Tm]

D C 29 H 50 Norhopane [C 29 ]

E C 29 H 50 18 α neonorhopane [C 29 ]

F C 30 H 52 Hopane [C 30 ]

G C 30 H 52 17 β 21 α moretane [C 30 ]

H C 31 H 54 22S homohopane [C 31 ]

I C 31 H 54 22R homohopane [C 31 ]

K C 32 H 56 22S bishomohopane [C 32 ]

L C 32 H 56 22R bishomohopane [C 32 ]

M C 33 H 58 22S trishomohopane [C 33 ]

N C 33 H 58 22R trishomohopane [C 33 ]

O C 34 H 60 22S tetrakishomohopane [C 34 ]

P C 34 H 60 22R tetrakihomohopane [C 34 ]

Steranes

1 C 27 H 48 13 β 17 α 20S diacholestane [C 27 ]

2 C 27 H 48 13 β 17 α 20R diacholestane [C 27 ]

3 C 27 H 48 13 α 17 β 20S diacholestane [C 27 ]

5a C 28 H 50 13 β 17 α 20S 24-methyldiacholestane [C 28 ] (I)

5b C 28 H 50 13 β 17 α 20S 24-methyldiacholestane [C 28 ] (II)

7a C 28 H 50 13 β 17 α 20R 24-methyldiacholestane [C 28 ] (I)

7b C 28 H 50 13 β 17 α 20R 24-methyldiacholestane [C 28 ] (II)

8 C 28 H 50 13 β 17 β 20S 24-methyldiacholestane [C 28 ] or 5 α 14 α 17 α 20S

cholestane [C 27 ]

10 C 28 H 50 5 α 14 α 17 α 20R cholestane [C 27 ] or 13 α 17 β 20R 24-

methyldiacholestane [C 28 ]

12 C 28 H 50 5 α 14 α 17 α 20S 24- methyldiacholestane [C 28 ] + Dia – C 29

13 C 28 H 50 5 α 14 β 17 β 20R 24- methyldiacholestane [C 28 ]

14 C 28 H 50 5 α 14 α 17 α 20R 24- methylcholestane [C 28 ]

15 C 29 H 52 5 α 14 α 17 α 20S 24- ethylcholestane [C 29 ]

16 C 29 H 52 5 α 14 β 17 β 20R 24- ethylcholestane [C 29 ]

17 C 29 H 52 5 α 14 β 17 β 20S 24- ethylcholestane [C 29 ]

18 C 29 H 52 5 α 14 α 17 α 20R 24- ethylcholestane [C 29 ]

64