Lyons W.C. (ed.). Standard handbook of petroleum and natural gas engineering.2001- Volume 1

Thermodynamics

235

550

1.2154

1272.0

1.5437

1.0798

1266.7

1.5279

0.9686

1261.2

1.5131

0.8753

1255.5

1.4990

0.7277

1243.2

1.47?2

0.6154

1229.8

1.4467

0.5264

1215.0

1.4216

0.4533

1198.3

1.3961

.....

......

Table

2-21

(continued)

600

1.3005

1302.8

1.5735

1.1591

1298.6

1.5588

1.0431

1294.3

1.5451

0.9463

1289.9

1.5323

0.7934

1280.6

1.5084

0.6779

1270.7

1.4863

0.5873

1260.1

1.4653

0.5140

1248.8

1.4450

0.4632

1236.7

1.4251

Pressure

.

psia

(Saturation

temp

.

deg

F)

700

1.4584

1359.9

1

.

6250

1.3044

1357.0

1.6115

1.1783

1354.0

1.5991

I

. 0732

1351.1

1.5875

0.9077

1345.0

1.566.5

0.7833

1338.6

1.5476

0.6863

1332.1

1.5303

0.6084

1325.3

1.5141

0.5445

1318.3

1.4989

0.4909

1311.0

1.4843

0.4062

1.4567

0.3417

1278.7

1.4303

0.2907

1260.3

1.4044

0.2489

1.3783

0.2135

1217.4

1.3515

1295.5

1240.0

150

(45(i.")

iOIl

(467.0

I

)

55(l

(476.514)

tj00

(486.2

I

)

700

(.503.

IO)

XOII

(.?lX.23)

900

(.531.98)

1.

000

(744.61)

I,

100

(55IiiO)

I

.

200

(.-)ti7

22)

I,

41111

(5x7

IO)

I

.

IiOO

(604

!IO)

1

.

800

(621

0:i)

'L.

000

(635.X2)

2.

200

(649

16)

750

1.5337

1387.3

1.6481

1.3732

1384.8

1.6350

1.2419

1382.3

1.6228

1.

1324

1379.7

1.6117

0.9601

1374.5

1.5914

0.8308

1369.2

1.5734

0.7300

1363.7

1.5570

0.6492

1358.1

1.5418

0.5830

1352.4

1.5276

0.5277

1364.4

1.5142

0.4405

1.4893

0.3743

13'20.9

1

4660

0.3'2'5

1307.0

1.4438

0.2806

1.4223

0.2457

1276.0

1.4010

1334.0

1292.0

.

U

h

%

71

IL

5

I,

h

s

71

h

5

I

I1

5

U

h

P

7'

I1

5

il

h

5

71

h

5

7'

h

5

7J

h

,

u

h

.

11

h

\

U

h

7

7'

h

.

-

500

.

1.1231

1238.4

I

.

5095

O.'IY?7

1231.3

14919

0.8832

1223.7

1.17.51

0.7947

1215.7

1.4586

.....

......

.....

....

......

.....

......

.....

....

.....

....

......

.....

......

.....

......

.....

....

.....

....

......

.....

0.4016

1223.5

1.4052

0.3174

1193.0

1.3639

......

....

......

Temperature

of

steam.

deg

F

.

650

1.3810

1331.9

1.6003

1.2333

1328.4

1.5663

1.1124

1.724.9

1.3734

1.0115

1321.3

1.5613

0.8525

1313.9

1.5391

0.7328

1306.2

1.5190

0.6393

1.5004

0.5640

1289.5

1.4825

0.5020

1280.5

1.4656

0.4498

1271.0

1.4491

.

1298.0

0.3668

1250.6

1.4171

0.3027

1227.3

1.3800

0.2506

1200.3

1.3.5 15

0.2058

1167.0

1.3139

0.1633

1121.0

1.2665

800

1.6071

1414.3

1.6699

1.4405

1412.1

1.6571

1.3038

1409.9

1.6452

1.1899

1407.7

1.6343

1.0108

1403.2

1.6147

0.8763

1398.6

1.

5972

0.7716

1393.9

1.5814

0.6878

1389.2

1.5670

0.6191

1384.3

1.553.5

0.5617

1379.3

1.5409

0.4714

1369.1

1.5177

0.4034

13.58.4

1.4964

0.3502

1347.2

1.4765

0.3074

139.5.5

1.4576

0.27'21

1323.9

1.4393

.

__

900

1.7516

1467.7

1.7

1

OR

1.5715

1466.0

1.6982

1.4241

1464.3

1.6868

1.3013

1462.5

1.6762

1.1082

1.6573

!).9633

1455.4

1.6407

0.8.506

1451.8

1.6257

11.7604

1.6121

0.6866

1444.5

1.5995

0.6250

1440.7

1.5879

.

1459.0

1448.2

n.5281

1433.1

1.5666

0.4553

1425.3

1.5476

0.3986

1417.4

1.5501

0.35.72

1409.2

0.5

I39

O.YI.SS

1400.8

1.4986

__

1.

000

1.8!42X

1521.0

1.7486

1.6996

1519.6

1

736.4

1.5414

1518.2

1.7250

I

.

4096

1516

i

17147

1.2024

1.513.9

1.6963

1.0470

151

1

0

16801

O.Y26:2

1508.1

1.66.56

O.8294

150.5

1

1.6525

0.7.503

1502.2

1.6405

0.6843

1499.2

1.6293

0.,580i

1493.2

1.6093

0.5027

1487.0

1

..?

91

I

0.4421

1480.8

1.57.72

0.503,5

1474.5

1

380

n5538

1468.2

1.5465

236

General Engineering and Science

50

52

54

56

58

60

62

64

66

68

70

72

74

76

78

80

82

84

86

88

90

92

94

96

98

100

102

104

106

108

110

112

114

1

I6

I18

120

122

124

126

128

130

132

134

136

I38

I40

142

144

146

148

150

Table

2-22

Steam Table

for

Use

in Condenser Calculations

Abs

pressure

Psi

In.

Hg

P

0.

I781

1

0.19182

0.20642

0.2220

0.2386

0.2563

0.2751

0.2951

0.3164

0.3390

0.3631

0.3886

0.4156

0.4443

0

4747

0.5069

0.5410

0.5771

0.6154

0.65.56

0.6982

0.7432

0.7906

0.8407

0.8935

0.9492

1.0078

1.0695

1.1345

1.2029

1.2748

1.3504

1.4298

1.5130

1.6006

1.6924

1.7888

1.8897

1.9955

2.1064

2.2225

2.3440

2.4712

2.6042

2.7432

2.8886

3.0440

3.1990

3.365

3.537

3.718

0.3626

0.3906

0.1203

0.4520

0.4858

0.5218

0.5601

0.6009

0.6442

0.6903

0.7992

0.7912

0.8462

0.9046

0.9666

1.0321

1.1016

I

1750

1.2.527

1.3547

14215

15131

1.6097

1.7117

1.819'2

1.9325

2.0519

2. I775

2.3099

2.4491

2.5955

2.7494

2.91

11

3.0806

9.2589

9.4458

3.64'20

3.8475

4.0629

4.2887

4.5251

4.7725

5.0314

5.3022

5.5852

5.8812

6.1903

6.5132

6.850

7.202

7.569

Specific

"OllUlle

Sat

vapor,

vg

1703.2

1587.6

1481.0

13132.4

1291.1

1206.7

1128.4

1055.7

988.4

925.9

867.9

813.9

763.8

717.1

673.1;

633.1

595.3

560.2

527.3

496.7

468.0

441.3

416.2

392.8

370.9

350 4

331.1

313.1

296.2

280.3

265.4

251.4

238.2

225.8

214.2

203.27

192.95

183.25

174.10

165.47

157 14

149.66

14'2.42

135.58

129.12

123.01

11

7.23

111.77

106.60

101.71

97.07

Sat

liquid,

f??

18.07

20.07

22.07

24.06

26.06

28.06

30.05

3'2.05

34.05

36.04

38.04

40.04

42.03

44.03

46.02

48.02

52.01

.54.00

50.01

.m.on

57.99

59.99

61.98

63

98

65.97

67

97

69.96

71.96

73.95

75.95

77.94

79.94

81.93

83.93

85.92

87.92

89.92

91.91

93.91

95.91

97

YO

99.90

101.90

103.90

105.89

107.89

109.89

113.89

115.89

11

7.89

I I

I

.n9

-

1065.6

1064.4

1063.3

1062.2

1061.0

10.59.9

1058.8

1057.6

1056.5

1055.5

1054.3

1053.2

1058.1

1050.9

1049.8

1048.6

1047.5

1046.4

1045.2

1044.1

104i.x

1042.9

1040.7

1039.5

1038.4

1037.2

1036.1

1034.9

1033.8

1032.7

1031.6

1030.4

1OpY.2

1028.1

1026.9

1025.8

1024.6

1023.4

1022.5

1021.1

1020.0

1018

8

1017.6

1016.4

1015.3

1014.1

1012.9

1011.7

10106

1009.4

1008.2

-

1083.7

1084.5

1085.4

1086.3

1087.1

1088.0

1088.9

I

089.

7

1090.6

1091.5

1092.5

1093.2

1094.1

1094.9

1095.8

1096.6

1097.5

1098.4

1099.2

1100.1

1100.9

1101.8

1102.6

110s.i

1104.4

1105.2

1106.1

1106.9

1108.6

llO9.5

I1

10.3

1111.1

11

12.0

1112.8

1113.7

1114.5

1115.3

11

16.2

1117.0

1117.9

1 118.7

11

19.5

1120.3

1121.2

1122.0

1122.8

1123.6

1

124.5

1125.3

1126.1

I

107.8

Entl

sat

liquid,

!f

0.0361

0.0400

0.0439

0.0478

0.0517

0.0555

0.0993

0.0632

0.0670

0.0708

0.0748

0.0783

0.0820

0.0858

0.0895

0.0932

0.0969

0.1005

0.1042

0.1079

0.1115

O.ll.51

0.1187

0.1223

0.1259

0.1295

0.1330

0.1366

0.1401

0.1436

0.1471

0.1506

0.1541

0.1576

n.1610

0.1645

0.1679

0.1714

0.174R

0.

I782

0.1816

0.1S49

0.1883

0.1917

0.

I950

0.1984

0.2016

0.2049

0.2083

0.2116

0.2149

V

2.1264

2.1199

2.1136

2.1072

2.1010

2.0948

2.0886

2.0826

2.0766

2.0706

9.0647

2.0588

9.0473

2.0416

2.0360

2.0304

2.0249

2.0195

2.0141

2.0087

2.0034

I

9981

1.9929

1.9877

1.9826

1.9775

1.9725

1.9675

1.9626

1.9577

1.9529

1.9481

1.9433

1.9386

1.9339

1.9293

1.9247

1.9202

1.9156

1.9112

1.9067

1.9023

1.8980

1

,8937

1.8894

1.8851

1.8809

1.8768

1.8726

1.8685

2.0530

SOURCE:

Baurneister

T.,

and

Marks,

L.

S.,

e&..

Standard

HmdDookJor

M~rhanml

EngiiiePrs,

Seventh

edition,

MrGldw-

Hill

Book

Co.,

New

York,

1967.

Thermodynamics

237

-40

-3.3

-30

-25

-20

-I,i

-10

0

,

IO

15

90

2.3

30

3

5

40

$5

.io

i.5

60

6.5

70

75

80

85

88

Pres

sure,

psia,

P

145.87

161.33

177.97

195.85

21.5.02

239.55

257.46

305.56

332.2

360.4

390.2

421.8

435.3

4110.6

528.0

567.3

608.9

652.7

698.8

747

4

798.6

852.4

909.3

969.3

10:42.7

1072.1

280.85

Table

2-23

Properties of Carbon Dioxide

(hf

and

sf

are measured from

32°F)

Density,

Ib

per

cu

ft

Sat

liquid

69.8

69.

I

68.3

67.6

66.9

66.1

65.5

64.5

63.6

W2.8

(<I.!)

61

.0

60.0

.59.0

58.0

.i7.0

55.9

54.7

53

4

52.1

.50.7

49.1

47.3

4.5.

I

42.4

38.2

32.9

Sat

vapor

1.64

1

83

2.02

2

23

2.44

2.66

"91

3.17

:4

46

3.77

1

I2

4.49

2.89

5.33

.5.81

6

35

6.91

7

60

8.37

9.27

10.2

I

1.3

12.6

14.2

16.2

19.1

25.4

Sat

liquid,

hf

-3R.5

-35.8

-33.1

-30.4

-27.7

-24.9

-22.1

-19.4

-16.7

-14.0

-11.2

-

8.4

-

2.j

+

0.4

3.5

6.6

9.8

12.9

16.1

19.4

22.9

26.6

30.9

35.fi

41.7

_-

-

3.:)

Enthalpy,

Btu

vapor-

ization,

hrp

136.5

134

3

132.1

129.8

127.5

125.0

122.4

120.0

I1

7.5

115.0

112 2

109.4

103.1

99.7

95.8

91.8

87.5

83.2

78.7

74.0

68.9

62.7

54.8

44.0

27.5

106.3

98.0

98..5

99.0

99.4

99.8

100.1

100.6

100.8

101.0

100.8

100.3

1ni.o

100.6

100.1

99.3

98.4

97.3

96.1

94.8

93.4

91.8

89.3

85.7

79.6

69.2

Xtical

point

at

88.43-F

Sat

liquid,

Sf

-0.0850

9.0793

-0.0676

-0.0619

-0.0560

-0.0440

-0.0381

-0.0735

-o.n5oo

-o.nm

-0.0264

-0.0204

-0.01 44

-0.0083

-0.0021

+0.0039

0.0090

0

0160

0.0'220

0.0282

0.0345

0.0412

0.0482

0.0562

0.0649

0.0761

0.2400

0.2367

0.2336

0.2506

0.2277

0.2220

0.2198

0.21

73

0.2151

0.2124

0.2

100

0.2071

0.2043

0.2012

n.z.io

n.197.i

n.1w2

0.1809

0.1934

0,1852

0.1767

0.1724

0.1665

0.1587

0.1464

0.1265

238

Entropy

*

.g

-0.086

-0.074

-0.061

4.049

4.036

-0.024

0.000

0.024

0.035

0.047

0.059

0.070

0.082

0.093

0.105

0.116

0.128

0.140

-0.012

0.012

.....

General Engineering and Science

ru-

0.400

0.393

0.389

0.384

0.380

0.377

0.371

0.368

0.366

0.365

0.364

0.363

0.374

0.370

...,.

.....

rr.

M

d

I

d

+

-70

-60

-50

-40

-30

-20

-1

0

+IO

20

30

40

50

60

70

KO

90

100

1

10

120

130

140

-

Table 2-24

Properties

of

Propane and Butane

rn

'L

g

e

a

7.37

9.72

-

12.6

16.2

20.3

25.4

31.4

38.2

46.0

55.5

66.3

78.0

91.8

107.1

124.0

142.8

164.0

187.0

?12.0

!40.0

.....

Prop-

(CSW

(Heat measurement are from

0°F)

$5

-0

u

an

$6

2

5;:

&%

t

cn

12.9

9.93

7.74

6.13

4.93

4.00

3.26

2.71

2.27

1.90

1.60

1.37

1.18

1.01

0.883

0.770

0.673

0.591

0.521

0.45Y

......

9

Sr

-

-37.0

-32.0

-26.5

-21.5

-16.0

-11.0

-5.5

0

5.5

11.0

17.0

23.0

29.C

35.0

41.0

47.5

54.c

60.5

67.0

73.5

....

B

s

a-

-

152.5

155.0

158.0

160.0

163.0

165.0

168.0

170.5

173.5

176.0

179.0

182.0

185.0

1R8.0

190.5

193.5

196.5

199.0

201.0

202.5

.....

Butane

(CIHLO)

(Heat measurements are from

O'F)

m

a

.-

a

_.

7.3

9.2

11.6

14.4

17.7

21.6

26.3

31.6

37.6

44.5

52.2

60.8

70.X

81.4

92.6

-

$$

3"

a

u

an

%?;

11.10

8.95

7.23

5.90

4.88

4.07

3.40

2.88

2.46

2.10

1.81

1.58

1.38

1.21

1

.07

Q

ff

'3

3-2-

-

0

5.5

10.5

16.0

21.5

27.0

38.5

44.5

57.0

63.5

70.0

76.5

83.5

33.0

51.0

8

n

5

e-

-

170.5

174.0

177.5

181.5

185.0

188.5

192.5

196.0

199.5

203.0

206.5

210.5

213.5

217.0

221.0

Entropy

3

-5

-

0.000

0.01

1

0.022

0.033

0.044

0.056

0.067

0.078

0.089

0.100

0.122

0.134

0.145

0.157

0.111

8

P

r

a

__

0.371

0.370

0.371

0.373

0.374

0.375

0.376

0.377

0.378

0.380

0.3RP

0.384

0.386

SOURCE:

Bdumeister

T.,

and

Marks,

L.

S.,

eds.,

Standard

Handbook

/m

Merhaniral

I?'nginwm,

Seventh cdition,

McGra~

Hill

Book

Co.,

New

York,

1967.

Thermodynamics

239

73.50

74.70

if.05

78.21

79.36

75.87

79.94

80.49

81.06

81.61

8'2.16

82.71

83.26

83.78

84

91

X4.82

85.82

86.80

88.@2

87 74

89.43

90.1.3

90.76

-

k.

M

8

;

-40

-10

B

-30

-20

0

10

15

20

25

30

35

40

45

.50

5

60

70

80

!IO

100

110

120

I30

___

n.oooo

O.lii2

0.00471

0.1539

0.01403

n.1717

0.01869

0.170!1

O.IYZWJ n.iini

0.02556

0.1698

0

02783 0.lti9.5

0.03008

0

169'2

0.03253

ll.l68>1

0.03438 0.1686

0.00941)

o.im

o.omn

o.I~H:~

o.osgo3

n.16xi

0.04126

O.lli7R

0.04348

0.1676

0.04568

O.llii4

0.05009

O.l67(l

0.05446

0.166ti

0 06316

0

16.58

0.05~~2

n.iw

0.06749

0

16.74

0.07180

(1.1649

0.07607

01644

Table

2-25

Properties

of

Freon

11

and

Freon

12

__

01

a

.-

t

a

0.739

1.03

I

.42

1.512

2.55

3

:45

3.82

4.54

4.92

.-,.5li

626

7.03

7.8H

x.xo

c3.x

I

10.9

1.7.4

l&:4

19

7

!:3.ll

!X.

I

$3

2

w.0

I

Freon

11

(CChF)

Heat measurements are from 40°F)

-

?g

%

E;

g%

&

0

an

v)

44.2

32.3

24.1

18.2

13.9

10.8

9.59

8

52

7..ix

6.i.i

6.07

3.45

4.90

4.42

4.00

3.63

2

99

2.49

2.0!3

1.76

1.50

1.28

1.10

Enthalpy,

Btu

per

Ib

a&

-

0.00

1.97

3.94

3.91

7.89

9.X8

10.88

11

87

12.88

13.88

14.88

15.89

16.91

17.9'2

18.95

19.96

22.02

24.09

26.18

28.27

30.40

52.53

34.67

8

P

>

-eM

87.4X

88.67

89.87

91.07

92.27

93.48

94.69

95.30

9.5.91

9651

97.11

97.72

98.Y2

98.93

99.3.7

00.73

09.1

2

04.30

05.47

06.63

07.58

94.09

0i.m

Entropy

U

'g

a*

0.0046

-

0.0000

0.0091

0

0136

0.0179

0.0222

0.0244

0.0264

o.rm

o.om

0.0326

0.0346

0.0966

0.0386

0.0406

0.0426

0.0.504

11.0542

I1

0580

0.0465

0.0617

0.0654

0.0tXII

s

%

>

-3

n.zo8.;

0.2ox1

-

0.2064

0.2046

0.2015

0.2003

0.1997

0.1991

0.1986

0.1981

0.1976

0.1972

0.1968

0.1960

0.19.58

0.1933

0.1'147

O.I9&2

0.19:7x

0.1935

0.1933

0.1931

0.1964

Freon

12

(CChF2)

(Heat measurements are from 4O'F)

01

.-

k

c

I

k

-

9.3

12.0

1.5.3

19.2

23.9

29.3

32.4

35.7

39.3

49.2

47.3

31.5

i6.4

61

4

66.7

72.4

84.8

98.8

114.1

131.6

150.7

171.x

194.9

-

g2

3

3s

g$

v)

3.91

3.00

2.37

2.00

1

64

1.3.5

123

1.12

1.02

0.939

0.862

0.79'2

0

750

0.673

0.575

0

493

0.4'2.5

0.368

0.319

0.277

0.240

0.20H

0.w

Enthalpy,

1

Btu

per

Ib

Entropy

5

-e%

0.00

-

2.03

4.07

6.14

H.25

10.39

1

I

.48

12.55

13.66

14.76

15.87

17.00

IH.14

19.27

20.41

21.57

23.90

26.28

28.70

31.16

33.6.5

36.

I6

38.69

-

240

General Engineering and Science

(text

continued

from

page

226)

GEOLOGICAL ENGINEERING

Geology is the study of the earth, its internal and surface composition, structure, and

the earth processes that cause changes in composition

and

structure. The earth is constantly

changing. The processes within the earth and the history of these processes are important

factors in determining how minerals deposits were formed, where they accumulated, and

how they have been preserved. The geology of the present composition and structure of

the earth and, secondarily, the history

of

the processes that resulted in the present geology

have become very important in the prediction of where accumulations of economically

valuable hydrocarbons (oil and gas) may be found. Studies of surface geological fractures

and the past processes coupled with such surface geophysical investigation techniques

as

seismic, gravity, magnetic, radioactive, electrical, and geochemical are used to locate

probable subsurface target regions that might contain economically valuable accumulations

of hydrocarbons. However, only by drilling

a

borehole from the surface to these subsurface

regrons is it possible to definitely assess whether hydrocarbons exist there. The borehole

provides a direct fluid communication from these subsurface regions to the surface,

where the fluid (if present) can be assessed for its economic value.

Not only is geology important in exploring for hydrocarbons, but also engineers

must study the present composition and structure of the earth

to

successfully drill

the borehole itself. Further, once hydrocarbons have been found and have proven to

be economically recoverable, studies of the physical and chemical aspects of earth in

such regions are important to the follow-on production and reservoir engineering.

These studies help ensure that the accumulated hydrocarbons are recovered in an

economic manner

[24].

General

Rock

Types

The earth is composed of three general rock types: igneous, sedimentary, and

metamorphic

[24].

Igneous

rocks are the original rocks of the earth and were solidified from the

molten mixture of materials that made up the earth prior to its cooling. Igneous

rocks are very

complex

assemblages of minerals. Usually such rocks are very

dense and have very few pores (or voids) which can accumulate or pass any type

of fluid.

Sedimentary

rocks are aggregates of particles broken away from other rock masses

which are exposed at or near the earth’s surface to weathering processes. These

particles are then transported by water, wind, or ice (glaciers) motion

to

new

locations where they assemble eventually into a new rock mass. The origin of

the rock mass prior to action by the weathering process can be igneous rock,

another sedimentary rock, or metamorphic rock (see next rock type). During

the process of weathering and transportation (particularly by water) compounds

are precipitated chemically from the original rock mass or from materials within

the water itself. In lake or seawater environments organisms provide such com-

pounds.

.4s

the particles are deposited in slower moving waters, the chemical

compounds provide a type of cement that ultimately binds the particles into a

sedimentary rock mass. Sedimentary rock masses that are formed from water

erosion and deposition by water in lake or ocean environments were originally

laid down (Le., deposited) in horizontal or near horizontal (deltas) layers.

Metamorphic

rocks are formed from either igneous, sedimentary, or possibly other

metamorphic rock masses. These original rock masses are subjected

to

heat,

Geological Engineering

241

pressure, or chemically active gases or liquids which significantly alter the original

rock to a new crystalline form.

In general, it

is

found from surface observations that about 75% of the land surface

area is composed of sedimentary rocks. Most of the remaining land area is composed

of igneous rock, with metamorphic rocks being a rather small percentage of the

earth’s surface-exposed rock. If the outer 10 mi of thickness of the earth is considered,

it is estimated that 95% of this volume of rocks (including those exposed at the surface)

are igneous rocks. Igneous rocks are the original rocks of the earth and are, therefore,

the ancestors of all other rock types [24,25].

Historical

Geology

It is estimated that the earth’s age is in the neighborhood of 4

to

7

billion years.

These estimates are basically derived from carbon-14, potassium-40, uranium-235,

and uranium-238 dating of earth rocks and meteorites. The meteorites give impor-

tant data as

to

the age of our solar system. Geologic time is felt to be represented

by the presence of rock intervals in the geologic column (layers of rock formations

in vertical depth) or by the absence of equivalent rocks in correlative columns in

adjacent locations [25,26]. The two basic factors that are used to determine geo-

logic time are:

1.

The principle

of

uniformity, which states that internal and external processes

affecting the earth today have been operating unchanged and at the same rates

throughout the developmental history of earth. This means that a historical

geologic event preserved in the rock record can be identified, in terms of its

elapsed time of development, with similar events occurring at the present time.

Therefore, rates of deposition, erosion, igneous emplacement, and structural

development will be preserved in the geologic column and can be compared

with current similar processes [25,26].

2. Relative time, which is based upon the occurrence of geologic events relative to

each other. Dating in this manner requires the development of a sequence of

events that could be established on the basis of obvious consecutive criteria.

The identification

of

a geologic continuum such that the events within the

sequence are sufficiently identifiable (e.g., uplifting, erosion, deposition) and

widespread to have practical significance. Such dating in relative time allows

events to be identified throughout the world [25,26]:

Superposition is fundamental to the study of layered rocks. This means that

in a normal layered (sedimentary) rock sequence, the oldest rocks were

deposited first and are at the bottom of the sequence. The younger rocks

were deposited last and are at the top of the sequence.

Succession of flora and fauna refers

to

the deposition of sedimentary material,

which will include the remains of plant and animal life that existed at the

time of the deposition

of

these rock particles. The fossils of these plants and

animals will be found in the rock formations that result from the deposition.

The presence, absence, or change of the plant and animal life within a

sequence of the geologic column provide important information that allows

for the correlation of rock formations (and, thereby, relative time) from

location

to

location. Also, the fossil records within sequences give important

information regarding the evolution of life through geologic time.

Inclusion

of

one rock type (usually igneous) into surrounding rocks is

invariably younger than the rocks it intrudes. Inclusions are useful in deter-

mining relative geologic ages.

242

General Engineering and Science

The term

cross-cutting relations

refers to pre-existing rocks that can be affected

by later faulting or folding of the rock mass. Layered rock sequences must be

in existence before the cross-cutting events occur. Cross-cutting is useful in

determining relative geologic ages.

Physiographic development

of

the surface

of

the earth refers to the landforms

and shapes of the landscape. These surface features are subject to continuous

change from constructive (e.g., uplift, volcanic activity, and deposition of

sediments) and destructive (e.g., erosion) processes. Landform modifications

are continuous and sequential. These modifications establish a predictable

continuity that can be helpful in determining certain aspects of relative

geologic ages.

The relationship between time units, time-rock units, and rock units is as follows:

Time Units Time-Rock Units Rock Units

Eon

Era Erathem Group

Period System Formation

Epoch Series Member

Age Stage

This system for keeping track of these important units is used as the basis for

the standard geologic time and the evolution of the animal life on earth. (See also

Tables

2-26

and

2-27.)

Table

2-28

gives the relationship between geologic time and

important physical and evolutionary events that are used to aid in the identification

of rock units in relative geologic time

[26].

Petroleum Geology

Basically, circumstantial evidence has lead geologists and other scientists to believe

that nearly all hydrocarbon (liquid and gas) deposits within the earth are strongly

associated with sedimentary rocks. This evidence suggests that hydrocarbons in the

earth are altered organic material derived from microscopic plant and animal life.

This microscopic plant and animal life that has thrived on land and in lake and ocean

regions of the earth through geologic time has been deposited with finely divided

clastic sediments. In general it is felt that most of the important deposition (relative

to hydrocarbon accumulations) has occurred in the marine environment in ocean

margins. The organic material is buried and protected by the clay and silt sediments

that accompany this material during deposition. The amount of organic material

available during deposition dictates the amount of hydrocarbons that might be

produced. The amount

of

sediments available for burial of the organic material

depends upon the amount of erosion that occurs on the landmasses. The more rapid

the burial of the organic material by the sediments, the more efficient the alterations

through geologic time of the organic material to basic hydrocarbons.

Conversion of the organic material appears to be assisted by the pressure

of

burial

depth, the temperature resulting from burial depth, and the type of bacterial action

in a closed nonoxidizing chemical system. If burial action is not sufficient to eliminate

oxygen, aerobic bacteria will act upon the organic material and destroy it. If burial is

sufficient to nearly eliminate oxygen from reaching the organic material, anaerobic

bacterial action involving oxygen from dissolved sulfates begins and a reducing

Geological Engineering

243

Table

2-26

The Standard

Geologic

Column

[24]

Refalwo

Gedog~~

Ti

Cemzwc

13-

Mesozoic

190-1

9h

34-

Devonian

Paleozoic

39-

430-440---

5-

Cambrian

stimated

ages

of time boundaries (millions

01

years)

environment develops. It is felt that this reducing environment is necessary for altering

the buried organic material and for beginning the process that ultimately leads to

the accumulation

of

the hydrocarbon deposits found in the great sedimentary basins

of

the world

[26-291.

Source Rocks

Abundant deposits of fine silt, clay, and organic material in ocean margins are the

most likely sedimentary deposits that will have the required reducing environment

for the alteration of the organic material. Such deposits eventually result in shale

rock formations after the cementing of the particles takes place over geologic time. It

is felt, therefore, that shale rock is the most likely source rock for hydrocarbons. The

best source rocks are considered to be black shales originally deposited in a

nonoxidizing, quiet marine environment. The deposition

of

organic material in nearly

pure carbonate deposits may represent a possible second type of sedimentary deposit.

244

General Engineering and Science

Approox. Age

in

Milhons

ot

Years

(Radioacbvity)

Era

Table

2-27

Geologic Time and Evolution of Ancient Life

[26]

Period or System

slum

rem

10

IM

~CN

*~S,IM

awnp

pnca

Pnd

nhrr

m

tom

me#-

R

\I

Jurassic

Triassic

Permian

Mesozoic

280

310

345

Paleozo,c 395

430440

500

570

700

I

3.400 First onecelled organisms

4.000

4.500 Approximate age

of

meteorites

'recambrim

Approximate age

of

oldest

rocks

discovered

These deposits would result in carbonate rock (e.g., limestone).

A

third source rock

possibility would be evaporite rocks (eg., salt, gypsum, anhydrite), which often contain

large organic concentrations when originally deposited

[26-291.

Migration

The hydrocarbons in some altered form migrate from the source beds through

other more porous and permeable beds to eventually accumulate in a rock called the

reservoir

rock.

The initially altered (i.e., within the source beds) organic material may

continue to alter as the material migrates. The hydrocarbon movement is probably

the result of hydrodynamic pressure and gravity forces.

As

the source beds are

compacted by increased burial pressures, the water and altered organic material are

expelled. Water movement carries the hydrocarbons from the source beds into the

reservoir, where the hydrocarbon establishes a position of equilibrium for the

hydrodynamic and structural conditions

[26-291.

Lyons W.C. (ed.). Standard handbook of petroleum and natural gas engineering.2001- Volume 1

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