In Situ Stress Analysis of Wellbore 

Breakouts from Oklahoma and the 

Texas Panhandle

U.S. GEOLOGICAL SURVEY BULLETIN 1866-F

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Chapter F

In Situ Stress Analysis of Wellbore 

Breakouts from Oklahoma and the 

Texas Panhandle

By RICHARD L DART

A multidisciplinary approach to research studies of 

sedimentary rocks and their constituents and the 

evolution of sedimentary basins, both ancient and modern

U.S. GEOLOGICAL SURVEY BULLETIN 1866 

EVOLUTION OF SEDIMENTARY BASINS ANADARKO BASIN
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government.

UNITED STATES GOVERNMENT PRINTING OFFICE: 1990

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

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Box 25425

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Library of Congress Cataloging-in-Publication Data

Dart, R.L (Richard L.)

In situ stress analysis of wellbore breakouts from Oklahoma and the Texas 

Panhandle / by Richard L Dart.

p. cm. (Evolution of sedimentary basins Anadarko Basin ; ch. F) 

(U.S. Geological Survey bulletin ; 1866-F)

Includes bibliographical references (p. )

Supt. of Docs, no.: I 19.3:1866-F

1. Rock deformation Oklahoma. 2. Rock deformation Texas. 

3. Earth Crust. I. Title . II. Series. III. Series: U.S. Geological Survey 

bulletin ; 1866-F. 

QE75.B9 no. 1866-F 

[QE604]

557.3 s-dc20 90-3686 

[557.8'09766] CIP
CONTENTS

Abstract Fl

Introduction Fl

Geologic setting F2

Wellbore enlargement data F5

Rock types of enlargement formation F8

Fracture enlargements and data scatter Fll

Inferred stress directions and relative stress magnitudes F17

Transpressional (oblique compressional) stresses and fault-bounded blocks F23

Conclusions F25

References cited F25

FIGURES

1-4. Maps showing:

1. Generalized structure of Oklahoma and the Texas Panhandle F3

2. Structure of the eastern Anadarko basin F4

3. Structure of the Marietta basin F6

4. Structure of the Bravo dome area F7 

5. Cross sectional schematics of wellbores showing original and enlarged

borehole shapes F8 

6-8. Three-dimensional histograms and frequency rose diagrams for the:

6. Eastern Anadarko basin F9

7. Marietta basin F10

8. Bravo dome area F12

9. Vertical bar graphs of wellbore enlargement type and rock type of 

enlargement occurrence F18

10. Histogram of wellbore enlargement data F24

TABLE

1. Quality criteria for breakout (wellbore enlargment) data F13 

2-4. Wellbore enlargement data for the:

2. Eastern Anadarko basin F14

3. Marietta basin F15

4. Bravo dome area F16

5. Stratigraphic units logged F20

6. Wellbore enlargement type, frequency of occurrence, and orientation F22

7. In situ stress data, south-central United States F23

8. Inferred stress directions from wellbore enlargment orientations F23

9. Comparison of wellbore enlargement data from different stress 

regimes F23

Contents III

EVOLUTION OF SEDIMENTARY BASINS-ANADARKO BASIN

In Situ Stress Analysis of Wellbore Breakouts from 

Oklahoma and the Texas Panhandle

By Richard L Dart

Abstract

Orientations of crustal stresses are inferred from stressinduced breakouts (well bore enlargements) in the eastern 

part of the Anadarko basin in central Oklahoma, the Marietta 

basin in south-central Oklahoma, and the Bravo dome area 

of the central Texas Panhandle. Inferred directions of maximum horizontal principal stress (SHmax) are east-northeast 

for the eastern Anadarko basin and northeast for the Marietta 

basin and the Bravo dome area.

The relative magnitudes of the three principal stresses 

(S,, S2, S3) are known for the Bravo dome area from existing 

hydraulic-fracturing measurements, and a normal-faulting 

stress regime (Sv>SHmax >SHmIn) is implied. For the eastern Anadarko basin and the Marietta basin, the magnitudes 

of the principal stresses are not known. Possible left-lateral 

oblique slip on the Meers fault during the Quaternary implies 

that strike-slip (SHmax >Sv>SHmln) and reverse (SHmax 

>SHmln >Sv) faulting has occurred in south-central Oklahoma. Thus, the study region may be a transition zone 

between extensional stress in the Texas Panhandle and 

compressional stress in Oklahoma.

Breakout data from the eastern Anadarko basin yield a 

single consistent SHmax orientation, whereas data from the 

Marietta basin and the Bravo dome area yield bimodalorthogonal distributions believed to consist of northwestoriented breakouts and northeast-oriented fracture-related 

wellbore enlargements. This northeast (orthogonal) trend in 

data from the Marietta basin and the Bravo Dome area is 

probably related to drilling-induced hydraulic fracturing of the 

wellbore or to preexisting natural fractures or joint sets 

intersecting the wellbore. On dipmeter log records, breakouts and fracture-related enlargements have similar elliptical 

cross sections. Orthogonally oriented breakout and fracturerelated wellbore enlargements are therefore differentiated by 

comparing their long-axis orientations with directions of 

known or inferred horizontal stress.

Manuscript approved for publication, January 10, 1990.

The mean orientations of either the breakout or fracturerelated orthogonal trends in the Marietta basin and the Bravo 

dome area data sets are not as well constrained as the mean 

orientation of breakout data for the eastern Anadarko basin. 

Poorly constrained mean orientations give the appearance of 

data scatter or dispersion among wellbore enlargement 

orientations within the northwest and northeast bimodalorthogonal trends. Drill holes in the Marietta basin and Bravo 

dome area are located primarily between northwest-striking 

subparallel faults. Mean data orientations calculated for 

either orthogonal trend for individual well data sets appear to 

rotate counterclockwise across these two fault-bounded 

study areas. Stress trajectory rotation between suparallel 

faults within the Marietta basin and the Bravo dome study 

areas may account for the data scatter.

Although breakouts and fracture-related enlargements 

formed in all parts of the thick sequences of sedimentary 

rocks logged, they are primarily in limestone, shale, and 

dolomitic rock, probably because of the abundance of these 

rock types.

INTRODUCTION

Numerous borehole stress studies (Cox, 1970; 

Brown, 1978; Bell and Gough, 1979, 1982; Gough and 

Bell, 1981, 1982; Hickman and others, 1985; Plumb and 

Hickman, 1985; Teufel, 1985; Zoback and others, 1985) 

and theoretical and laboratory studies simulating borehole stress conditions (Mastin, 1984; Haimson and Herrick, 1985; Zoback and others, 1985) show that wellbore 

breakouts are stress-induced spall zones that typically 

elongate vertically within the wellbore and are the result 

of compressional shear failure of the wellbore associated 

with unequal horizontal compressive stresses about the 

wellbore. Wellbore breakouts are elliptical in cross 

section and are aligned in the direction of minimum 

horizontal compressive stress (SHmin ). The idea that 

breakouts reflect local in situ stress conditions is 

supported by the agreement between stress directions

In Situ Stress Analysis of Wellbore Breakouts, Oklahoma and Texas F1
inferred from breakouts and stress orientations obtained 

using other types of stress data such as earthquake focal 

mechanisms, hydraulic-fracturing measurements, and 

geologic indicators of stress (Gough and Bell, 1981, 

1982; Hickman and others, 1985; Plumb and Hickman, 

1985; Dart and Zoback, 1989).

Breakout-data analysis is an important tool in 

understanding present-day stress conditions in areas 

where more detailed stress measurements are not available. An understanding of in situ stress conditions is 

essential in evaluating seismic hazards, recent crustal 

deformation, and the potential for slip on existing faults. 

In the petroleum industry, knowledge of borehole stress 

conditions can be critical in the engineering and design of 

drilling operations and hydraulic-fracturing treatments 

(Dart and Zoback, 1989).

The eastern Anadarko basin, Marieta basin, and 

Bravo dome area were selected for study on the basis of 

data availability, proximity to the Anadarko basin, and 

involvement in the structural and tectonic evolution of 

Oklahoma and the Texas Panhandle. This paper offers a 

more detailed analysis of data presented in earlier 

reports (Dart, 1987; Dart and Zoback, 1987).

Acknowledgments. I thank the following individuals and companies for the generous assistance in 

acquiring much of the data needed for this study: David 

Walker (Baker and Taylor Drilling Co., Amarillo, Tex.); 

Mark Ramsey and E.G. Kerns (Cities Service Oil and 

Gas Corp., Oklahoma City, Okla.); Bill Osten (Phillips 

Petroleum Co., Oklahoma City, Okla.); T.A. Deines, 

Stephen O'Niell, and P.L. Clymer (Marathon Oil Co., 

Midland, Tex.); J.A. Norton (Consolidated Oil and Gas, 

Inc., Denver, Colo.); Greg Riepl (States Petroleum Inc., 

Irving, Tex.); DJ. Wechsler, Daniel Hanson, and M.D. 

Wittstrom (Chevron U.S.A. Inc., Oklahoma City, Okla.); 

Jackie Ritchey and Bill Clement (AnSon Gas Corp., 

Oklahoma City, Okla.); Ted Price (Samedan Oil Corp., 

Oklahoma City, Okla.); S A. Maier (The Anchutz Corp., 

Oklahoma City, Okla.), Phil Schrenier and A.R. Dowell 

(Texaco U.S.A., Denver, Colo.); and Tom Verolust 

(Mustang Production Co., Oklahoma City, Okla.).

Conversations with D.G. Davis of the Colorado 

School of Mines and W.J. Perry Jr., S.H. Frezon, M.L. 

Zoback, and H.S. Swolfs of the U.S. Geological Survey 

were very helpful in clarifying a number of important 

points. I am indebted to W.J. Perry Jr., H.S. Swolfs, J. 

Schmoker, M. Cecil, and M.L. Zoback for their critical 

reviews of the text.

GEOLOGIC SETTING

Located on the boundary between the Great Plains 

and Central Lowlands physiographic provinces, the study 

area (fig. 1) is a region of deep sedimentary basins filled 

with thick sequences of Paleozoic marine rocks separated

by uplifted basement structures of Cambrian and Precambrian igneous and metamorphic rocks (Jordan, 1967; 

Johnson and others, 1972; Johnson and Denison, 1973; 

Johnson and others, 1984). The primary west-northwest 

structural trend of basins and basement highs extends 

across southern Oklahoma into the Texas Panhandle. 

This trend developed in the Paleozoic Era during periods 

of basement faulting, igneous intrusion, basin subsidence, and orogenic deformation (Ham and others, 1964; 

Hoffman and others, 1974; Wickham, 1978; Perry, 1989). 

The stratigraphic history of the region is dominated by 

episodes of carbonate and shale deposition attributed to 

eustatic fluctuations and intervals of clastic deposition 

associated with subareal erosion of uplifted areas.

The eastern Anadarko basin underlies most of 

central Oklahoma (figs. 1 and 2). It is bounded on the 

south by the Amarillo-Wichita uplift, the Marietta and 

Ardmore basins, and the Arbuckle uplift and on the east 

by the Nemaha ridge. The Frontal fault system forms a 

reverse-faulted zone of detachment that separates the 

Anadarko basin to the north from the Amarillo-Wichita 

uplift (Gilbert, 1983; Perry, 1989). The basin is deepest 

along this boundary; an accumulation of more than 

40,000 ft of Paleozoic sediments forms the most complete Paleozoic section in the Midcontinent structural 

province (Adler and others, 1971). This Cambrian to 

Permian section is composed of Cambrian to Mississippian carbonate rocks and shale unconformably overlain by Pennsylvanian to Permian clastic sedimentary 

rocks (Petroleum Information Corporation, 1982). The 

lower part of this section formed during a period of 

shallow marine deposition and rapid basin subsidence 

(Feinstein, 1981); the upper part was deposited in 

response to erosion of the Amarillo-Wichita and Criner 

uplifts to the south and east of the basin (Moore, 1979). 

Faulting along the eastern and southern boundaries of 

the basin occurred during the formation of the AmarilloWichita uplift and in response to compressional tectonism associated with uplift of the Ouachita Mountains 

and the Nemaha ridge (fig. 1) (Gilbert and Donovan, 

1982; Burchett and others, 1985). Evidence of recent 

movement on faults within the Frontal fault system in 

southern Oklahoma is supported by geomorphic and 

stratigraphic data. Ramelli and others (1987) and Luza 

and others (1987) have documented Quaternary oblique 

slip with down-to-the-south movement on the Meers 

fault and possible recent movement on the Washita 

Valley fault.

The Marietta basin in Oklahoma (figs. 1 and 3) at 

the eastern end of the Amarillo-Wichita uplift is within 

the Southern Oklahoma aulacogen. This northwesttrending synclinal structure is bounded on the northeast 

by the Criner uplift and on the southwest by the WaurikaMuenster uplift. The early depositional history of this 

area, which predates the formation of the Marietta

F2 Evolution of Sedimentary Basins Anadarko Basin
102° 100° 96°

w

£

09

i

!

M

34°

HOLLISI HARDEMAN 

U. BASIN

100 200 KILOMETERS

Figure 1. Generalized structure of Oklahoma and the Texas Panhandle. Location of study areas (screened areas) and 

shown. Modified from Nicholson (1960), Johnson and others (1972), Morris (1974), Haley (1976), and the Petroleum Inf
35 C

_ ___ MAJOR IGARFIELD 

BLAINEJKINGFISHER

i

_j__ ! oV\ NOBLE LOGANT" " ~

/

OK27

OK105,

OK102-108 

ANADARKO BASIN

PAYNE

OKLAHOMk CITY \ OKLAHOMA CITY

(OK9 UPLIFTT | V . klNCOL:N_ m ___

SPOTTAWATOM1E

I

I

I0 10 20 30 40 KILOMETERS

I I I I i

EXPLANATION

, Jhrust fault Sawteeth on upper plate

 Strike-slip fault Arrows indicate relative horizontal 

movement

-g Dip-slip fault Upthrown (U) and downthrown (D) blocks 

shown

Fault Dashed where inferred

F4 Evolution of Sedimentary Basins Anadarko Basin
syncline, involves deposition of a thick sequence of 

Cambrian to Ordovician carbonate rocks overlain by 

Upper Ordovician through Lower Mississippian limestone, sandstone, and shale (Henry, 1968).

The Wichita orogeny in Late Mississippian to 

Middle Pennsylvanian (early Atokan) time and the 

Arbuckle orogeny in early Desmoinesian to early 

Virgilian time were significant events in the structural 

and depositional histories of the Marietta basin (Tomlinson and McBee, 1959). Formation of the Criner and 

Muenster-Waurika uplifts and faulting and folding 

associated with initial development of the Marietta syncline accompanied the Wichita orogeny (Tomlinson and 

McBee, 1959). Early syncline development is possibly 

associated with deformation of the Southern Oklahoma 

aulacogen (Wickham, 1978). Significant deposition 

within the syncline did not begin until late Middle 

Pennsylvanian (Desmoinesian) time (Frederickson and 

Redman, 1965). The Marietta syncline was little affected 

by tectonism of the Arbuckle orogeny. During this period 

of erogenic activity, the Criner uplift acted as a structural 

barrier to southwest compressional stresses and 

associated crustal shortening and faulting (Frederickson 

and Redman, 1965). At the close of the Pennsylvanian 

Period, however, Virgilian- and Permian-age sediments 

were eroded from the Arbuckle Mountains and 

deposited over the area (Frederickson and Redman, 

1965). Basin subsidence associated with sediment 

loading continued into post-Permian time (Frederickson 

and Redman, 1965).

The Bravo dome (figs. 1 and 4), located within the 

larger Permian basin, is a Late Mississippian to Early 

Pennsylvanian tectonic feature between the Dalhart and 

Palo Duro basins (Budnik and Smith, 1982). Formation 

of the Bravo dome coincided with development of the 

Amarillo-Wichita uplift. By mid-Permian time, carbonate and clastic (arkosic) sedimentary rocks deposited 

in response to Late Mississippian to Early Pennsylvanian 

tectonism completely covered structural features such as 

the Bravo dome and filled the smaller basins in the region 

(McGookey and Goldstein, 1982). Within this part of the 

Texas Panhandle, a sequence of Permian-age halitebearing formations interbedded with marine mudstone,

Figure 2 (facing page). Structure map of the eastern Anadarko basin. Direction of wellbore enlargement is indicated 

by dot with solid line; line length is proportional to statistical 

quality (A-C); for example, OK27 is B quality, and OK16 is C 

quality. Bimodal-orthogonal data sets and data sets that are 

not bimodal but do have orthogonal data are indicated by 

paired solid lines and paired solid and dashed lines, 

respectively. Line lengths for some bimodal-orthogonal and 

orthogonal data sets are commonly shorter because of 

D-quality standard deviations. Open triangle with line indicates hydraulic fracturing data (von Schonfeldt and others, 

1973). Structural features from Chenoweth (1972).

siltstone, anhydrite, and dolomite units covers the Bravo 

dome structure (Presley, 1980). This overlaying sedimentary accumulation is cut by a series of northweststriking high-angle faults that define basement structures 

(fig. 4) (Dutton and others, 1982). The most prominent 

of these is the Potter County fault, which separates the 

Bravo dome from the Dalhart basin. Basement faults 

associated with Paleozoic tectonism of the AmarilloWichita uplift are probably reverse faults (Dutton and 

others, 1982). Deformation, associated with these faults, 

of late Tertiary-age Ogallala Formation strata is 

indicative of Cenozoic fault movement in the Texas 

Panhandle (Budnik, 1987).

WELLBORE ENLARGEMENT DATA

Wellbore enlargement (breakout) stress data are 

the measured long-axis orientations of stress-related 

elliptical features on standard four-arm, high-resolution 

dipmeter and fracture-identification well logs. Breakoutstress studies are economical because of the availability 

of well-log data through institutional, commercial, and 

industrial sources.

Two types of wellbore enlargements are important 

to this study: (1) stress-induced breakouts associated 

with shear failure of the wellbore, and (2) orthogonally 

oriented, stress-related fracture borehole enlargements 

likely associated with either drilling-induced hydraulic 

fracturing of the wellbore or favorably oriented preexisting fractures or closely spaced joint sets intersecting 

the wellbore (fig. 5) (Dart and Zoback, 1989). Fracturerelated wellbore enlargements should be oriented in the 

direction of SHmax , perpendicular to the trend of breakouts in the same well, creating an orthogonal-bimodal 

distribution of enlargement orientations. Fracturerelated enlargements due to preexisting fractures reflect 

the trend of these fractures. Whether hydrostatically 

induced or preexisting, fractures intersecting the borehole probably aid in the formation of stress-related, 

elliptically shaped wellbore enlargements.

Statistically, wellbore enlargement data sets are 

treated as axially symmetric, circular-normal distributions of two-dimensional vectors (Batschelet, 1965; Dart, 

1987). The results of standard statistical calculations for 

mean direction, mean deviation, and standard deviation 

are displayed as rose diagrams of data sets (figs. 6-8). To 

avoid having the analyst or the reader make biased 

interpretations of inferred stress orientations, rosediagram plots are proportional to petal area, not petal 

length (Werner, 1976).

In the three areas studied, borehole data from a 

total of 46 selected wells consisting of 40 well data sets 

(tables 2-4) were analyzed. Only well data sets having 

statistical qualities of C or better (table 1) (M.L. Zoback, 

written commun., 1987) and bimodal-orthogonal and

In Situ Stress Analysis of Wellbore Breakouts, Oklahoma and Texas F5
97°30'

o>

CD 

D)

S2. 5" 

w 

I

o>

a

D)

I

CD 

D) 

(0

34°00' h

EXPLANATION

 Fault

 I Anticline

10 KILOMETERS

J

Figure 3. Structure map of the Marietta basin. Direction of wellbore enlargement indicated by dot with solid line; 

statistical quality (A-C); for example, OK62 is B quality and OK32 is C quality. Bimodal-orthogonal data sets and data 

do have orthogonal data are indicated by paired solid lines and paired solid and dashed lines, respective

bimodal-orthogonal and orthogonal data sets are commonly shorter because of D-qualrty standard deviations. Structu

(1972).
Dip-slip fault Upthrown (U) and downthrown 

(D) blocks indicated. Dashed where inferred

30 KILOMETERS

Figure 4 Structure map of the Bravo dome area. Direction of welibore enlargement indicated by dot with solid 

line- line length is proportional to statistical quality (A-C); for example, TX12 is C quality. Bimodal-orthogonal data 

sets and data sets that are not bimodal but do have orthogonal data are indicated by paired solid lines and paired 

solid and dashed lines, respectively. Line lengths for some bimodal-orthogonal and orthogonal data sets 

commonly are shorter because of D-quality standard deviations. Open triangle with line indicates hydraulic 

fracturing data (von Schonfeldt and others, 1973). Structural features from McGookey and Goldstem (1982).

In Situ Stress Analysis of Welibore Breakouts, Oklahoma and Texas F7
SH

SH

Figure 5. Cross sectional schematics of wellbores showing original borehole shape (dashed line) and enlarged borehole 

shape (solid line). Breakout (A) and fracture (B) elliptical wellbore enlargements are shown.

orthogonal data sets were used in the statistical calculations of study-area data composites (figs. 6-8, tables 

2-4). Well locations and calculated mean orientations of 

the data are plotted in figures 2-4.

Plotted data (figs. 2-4) for individual well data sets 

consist of four or more wellbore enlargement orientations. Bimodal-orthogonal data sets have orthogonal 

modes of relatively equal numbers of wellbore enlargement orientations, whereas orthogonal data sets generally have only one wellbore enlargement orientation 

orthogonal to a preferred (primary) mode of the data. 

For bimodal-orthogonal data sets, the mean orientations 

of both modes are plotted as solid lines (figs. 2-4). 

Preferred modes and orthogonal trends in orthogonal 

data sets are plotted as solid and dashed lines, 

respectively.

Breakout data from the 16 well data sets in the 

eastern Anadarko basin study area form a consistent 

north-northwest trend. There are no bimodal data sets, 

and only three of the data sets have minor orthogonal 

east-northeast trends (fig. 2, table 2). Stress-related 

fracture wellbore enlargements rarely occur in the eastern Anadarko basin study area.

Common in the Marietta basin and the Bravo 

dome area are bimodal-orthogonal and orthogonal data 

sets and well data sets consisting entirely of inferred 

fracture wellbore enlargements (figs. 3 and 4). In the 

Marietta basin, 1 of the 12 well data sets consists 

exclusively of northwest-oriented breakout data, 5 data 

sets are composed of east-northeast to northeastoriented inferred fracture enlargements, 6 data sets are 

bimodal-orthogonal, and 3 data sets are orthogonal by

definition (table 3). A similar situation was observed in 

data for the Bravo dome area where of the 12 data sets 3 

consist exclusively of breakout data, 3 consist exclusively of inferred fracture wellbore enlargements, 4 are 

bimodal-orthogonal, and 2 are orthogonal by definition.

ROCK TYPES OF ENLARGEMENT 

FORMATION

Probably because of the predominance of carbonate and shale rocks throughout the study region 

(American Association of Petroleum Geologists, 1983a, 

b), both breakouts and fracture enlargements are most 

common in limestone, dolomite, and shale rock units 

(tables 5 and 6, fig. 9).

In the eastern Anadarko basin, 62 percent of the 

breakouts and 80 percent of the fracture wellbore

Figure 6 (facing page). Three-dimensional histograms and 

frequency rose diagrams for the eastern Anadarko basin. 

Distributions of wellbore enlargements are shown with 

azimuth (A) versus depth (subsea) and (B ) versus frequency of occurrence (feet or number). See text for 

explanation of statistical values shown. Depths in 1,000-ft 

increments. Approximate stratigraphic contacts: Upper and 

Middle Pennsylvanian at 5,500 ft; Middle and Lower 

Pennsylvanian at 7,000 ft; Lower Pennsylvanian and top of 

Mississippian, Devonian, and Silurian at 9,000 ft; base of 

Mississippian, Devonian, Silurian, and Upper Ordovician at 

10,200 ft; Upper and Middle Ordovician at 10,700 ft; Middle 

and Lower Ordovician at 11,200 ft; Lower Ordovician and top 

of Cambrian at 12,500 ft; base of Cambrian and top of 

Precambrian at 13,000 ft.

F8 Evolution of Sedimentary Basins Anadarko Basin
Eastern Anadarko Basin 

n = 4,887 

r = 1,465 

Mean = 354° 

Std. err. =0.3° 

Ang. dev. = 22°

250

200

85

Upper

Middle

Pennsylvanian

Lower (Sr|8le. sandstone, limestone) 

Mississippian, Devonian 

y Silurian (limestone, shale)

Ordovician

(shale, dolomite, sandstone, limestone) 

Cambrian

sandstone, conglomerate) 

Precambnan (granite)

7.0 21.0

14.0

Eastern Anadarko Basin 

n = 84 

r = 21

Mean = 349° 

Std. err. = 2.5° 

Ang. dev. = 23°

Upper

Middle

Pennsylvanian

(shale, sandstone, limestone) 

Lower '

Mississippian, Devonian 

Upper Silurian (limestone, shale)

Ordovician 

(shale, dolomite, sandstone, limestone) Lower 

Cambrian

(sandstone, conglomerate) 

Precambnan (granite)

,n Situ Stress Analysis of Wellbore Breakouts, Oklahoma and Texas F9
85

Marietta Basin 

n = 2,404 

r =453 

Mean = 288° 

Std. err. = 0.7° 

Ang. dev. =35°

Pennsylvanian 

sandstone, limestone, shale)

Lower Mississippian, Devonian, 

and Silurian (limestone, shale)

Marietta Basin 

n = 66 

r = 8

Mean = 278° 

Std. err. = 4.3° 

Ang. dev. = 35°

Pennsylvaman 

sandstone, limestone, shale)

Lower

Mississippian, Devonian, 

and Silurian (limestone, shale) 

Upper

Ordovician (shale, limestone, 

sandstone)

F10 Evolution of Sedimentary Basins Anadarko Basin
enlargements are in limestone (fig. 9). In the Marietta 

basin, an equal percentage (43) of both breakout and 

fracture wellbore enlargements are in limestone (fig. 9). 

Thirty percent of the breakouts are in formations of 

sandstone, shale, and limestone, and 27 percent of the 

fracture enlargements are in shale. In the Bravo dome 

area, 49 percent of the breakouts and 34 percent of the 

fracture wellbore enlargements are in dolomite, whereas 

35 percent of the breakouts and 43 percent of the 

fracture enlargements are in shale (fig. 9).

The formation of stress-induced breakouts and 

stress-related fracture wellbore enlargements in particular rock types are less likely a function of rock type and 

more probably a function of the abundance of carbonate 

and shale rocks in the stratigraphic section represented in 

the dipmeter log records analyzed and the existing in situ 

stresses within the areas studied. That is, stress conditions necessary to initiate stress-induced and stressrelated wellbore enlargement development probably are 

present within the dominant sedimentary rock types 

logged.

FRACTURE ENLARGEMENTS AND 

DATA SCATTER

Orthogonal trends in bimodal data sets associated 

with breakout and fracture-related wellbore enlargement 

orientations contribute significantly to increased standard deviations for individual well data sets and to the 

dispersion (data scatter) in data composites for the 

Marietta basin and Bravo dome study areas (figs. 6-8).

In this study, breakout and fracture-related wellbore enlargements were differentiated by comparing 

their enlargement orientations with known directions of 

SHmax from hydraulic-fracturing measurements (figs. 2 

and 4, table 7). The data suggest that north-northwest to 

northwest-oriented wellbore enlargements are breakouts 

and that northeast-oriented wellbore enlargements are 

fracture-related wellbore enlargements.

Comparison of conductivity values associated with 

the cross sectional long and short wellbore enlargement 

axes (short/long axis conductivity ratios) has been

Figure 7 (facing page). Three-dimensional histogram and 

frequency rose diagrams for the Marietta basin. Distributions 

of wellbore enlargements are shown with azimuth (-4) versus 

depth (subsea) and (B) versus frequency of occurrence (feet 

or number). See text for explanation of statistical values 

shown. Depths are in 500-ft increments. Approximate 

stratigraphic contacts: Upper and Middle Pennsylvanian at 

5,000 ft; Middle and Lower Pennsylvanian at 7,500 ft; Lower 

Pennsylvanian and top of Mississippian, Devonian, and Silurian at 7,700 ft; base of Mississippian, Devonian, Silurian, and 

Upper Ordovician at 8,300 ft; Upper and Middle Ordovician 

at 9,000 ft.

suggested as a possible method of distinguishing breakout from fracture-related wellbore enlargements (Blumling, 1986). This method should work well only when the 

formation in which the enlargement has formed is of low 

porosity; that is, favorably oriented preexisting vertical 

fractures or drilling-induced hydraulic fractures associated with fracture wellbore enlargements may create a 

more direct path for induced current and thus higher 

conductivity values (D.G. Davis, oral commun., 1988) 

than the current path associated with the curvilinear 

shear failure of breakout wellbore enlargement formation (Dart and Zoback, 1989). In highly fractured or 

porous rock, dispersion of a directed current should 

result in lower conductivity values and thus make differentiation of wellbore enlargement type difficult. 

Detailed information concerning the rock type and 

porosity of the units in which wellbore enlargements 

formed is necessary to more accurately differentiate 

wellbore enlargement type. Greater accuracy in distinguishing between types of wellbore enlargements may 

be achieved, however, by using digitized dipmeter well 

logs, which should afford the analyst a greater sampling 

frequency of conductivity data.

In the areas studied, fracture and joint patterns 

observed at the surface and at depth agree with orientation trends observed in wellbore enlargement data. A 

study of subsurface fractures in the "Mississippi Lime" 

(driller's term) and the Devonian and Silurian Hunton 

Limestone (9,055-9,331 ft below ground surface) of 

Kingfisher County in the eastern Anadarko basin (fig. 2) 

reveals a bimodal pattern of vertical natural fractures 

(Brevetti and others, 1984): a primary north-south trend 

and a secondary east-west trend. These fractures are 

within the depth interval for breakout occurrence. The 

mean orientations of both fracture trends are subparallel 

with the mean orientations of breakouts and with the 

minor set of orthogonally oriented wellbore enlargements inferred to be fracture related.

In the Slick Hills area of Oklahoma, adjacent to 

and north of the Meers fault in the southwest corner of 

the eastern Anadarko basin (fig. 2) and approximately 

70 km northwest of the Marietta basin, Wilhelm and 

Morgan (1986) observed a bimodal pattern of geographic lineaments oriented between N. 30°-60° W. and 

N. 40°-50° E. These "well-constrained" lineament patterns are interpreted as being associated with northweststriking left-lateral and high-angle thrust faults and 

northeast-striking right-lateral faults (Wilhelm and 

Morgan, 1986). This bimodal pattern agrees with the 

mean orientations of breakouts and orthogonally 

oriented, inferred fracture-related wellbore enlargements from wells in the Marietta basin (fig. 3).

In the Bravo dome area of the Texas Panhandle 

(fig. 4), surface and subsurface fractures also form 

bimodal trends oriented roughly west-northwest and

In Situ Stress Analysis of Wellbore Breakouts, Oklahoma and Texas F11
388.0 129.3

258.6

129.3 388.0

258.6

Bravo Dome Area 

n = 1,851 

r = 388 

Mean = 23° 

Std. err. = 0.8° 

Ang. dev. =33°

200

Permian

siltstone, mudstone, 

conglomerate, anhydrite, 

mestone) 

shale, limestone)

Pennsylvaman 

clastic rocks, limestone)

Bravo Dome Area 

n = 66 

r = 10 

Mean = 348° 

Std. err. = 4.5° 

Ang. dev. = 36°

Permian

siltstone, mudstone, 

conglomerate, anhydrite, 

limestone) 

shale, limestone)

Pennsylvaman

 3,850 / (clastic rocks, limestone) 

-4,850-

F12 Evolution of Sedimentary Basins Anadarko Basin
Table 1 . Quality criteria for breakout (wellbore 

enlargement) data

[A breakout data set is considered very poor (VP) if its 

standard deviation is greater than 30°, regardless of the 

number of breakouts measured. Leaders ( ) indicate any 

number of breakouts. Table from M.L. Zoback (written 

commun., 1987)]

Data set 

quality

A

B

C

D

VP

Number of 

breakouts

>10

>6

>4

<4

...

Angular 

deviation

<12°

>12°, <20°

>20°, <25°

>25°, <30°

>30°

northeast (Gustavson and Budnik, 1985; Gustavson and 

Finley, 1985). Although the bimodal trends of these 

fractures are somewhat random, agreement does exist 

between the bimodal trends of subsurface near-vertical 

fractures (Gustavson and Budnik, 1985) observed in the 

Stone and Webster Holtzclaw No. 1 well (fig. 4) and 

northwest- and northeast-oriented wellbore enlargements in the Bravo dome area.

In all three study areas, the mean orientations of 

breakouts and inferred fracture wellbore enlargements 

are about the same as bimodal orientations of observed 

natural fractures within or adjacent to these areas. This 

finding tends to support a genetic relationship between 

the formation of some wellbore enlargements and preexisting vertical fractures.

Studies show that drilling-induced hydraulic fracturing is related to an increase in hydrostatic pressure 

within the wellbore or to a decrease in rock tensile 

strength (Ellis and Swolfs, 1983; Stock and others, 1985). 

Unfortunately, an association between hydraulic fracturing and the formation of inferred fracture wellbore 

enlargements could not be verified for the study areas 

due to the unavailability of detailed drilling records of 

pumping pressures and fluid weights; however, changes 

in relative conductivity on dipmeter logs do show the 

coincidence of wellbore enlargements and fonnational or 

bedding boundaries.

A possible mechanism for the development of 

fracture-related enlargements of either type involves the 

"chipping out" of the wellbore during the drilling process 

(D.G. Davis, oral commun., 1988). By this means, the 

wellbore is enlarged ellipticalty in an area weakened by

Figure 8 (facing page). Three-dimensional histogram and 

frequency rose diagrams for the Bravo dome area. Distributions of wellbore enlargements are shown with azimuth 

(A) versus depth (subsea) and (B) versus frequency of 

occurrence (feet or number). Clastic rocks are granite wash. 

See text for explanation of statistical values shown. Depths 

are in 500-ft increments. Approximate stratigraphic contacts: 

Permian and Pennsylvanian at 1,700 ft; Pennsylvanian and 

Precambrian at 5,000 ft.

drilling-induced hydraulic fractures or by favorably 

oriented, open, preexisting vertical natural fractures or 

joint sets intersecting the borehole. The process of 

fracture-related enlargement formation may be aided by 

the erosional effects of circulating drilling fluid and 

drill-string wear.

Due to the difference in horizontal stress concentrations about the borehole, favorably oriented preexisting vertical fractures intersecting the wellbore 

should remain open and thus increase the possibility of 

mechanical wellbore enlargement. A possible example of 

this process is given by Gustavson and Budnik (1985) in 

their discussion of the preferred northeast orientation of 

fracture-related solution features in the Permian saltbearing stratigraphy of the Texas Panhandle and 

northeast-oriented hydraulic fractures induced in the 

Stone and Webster Holtzclaw No. 1 well (fig. 4). Gustavson and Budnik postulated that dissolution of saltbearing formations was more rapid in the direction of 

SHmax along northeast-oriented fractures.

Fractures intersecting the wellbore do not always 

develop wellbore enlargements. Eighty-four fractures 

observed as conductive anomalies on fracture identification logs from six Marietta basin wells (The Anchutz 

Corporation, unpub. data, 1987) exhibit very few wellbore enlargements. These 84 fractures, having a mean 

azimuth of N. 42° E. and primarily in the Upper Ordovician Viola Limestone, were compared with 35 northeastoriented wellbore enlargements from 13 additional wells 

in the same basin. Many of the 35 northeast-oriented 

wellbore enlargements, inferred to be fracture related, 

are in limestone and shale formations and are associated 

with fracture-conductivity anomalies. These 35 wellbore 

enlargements have an average orientation of N. 65° E. 

The 27° difference in orientation between these two 

groups of data may be due in part to variations in natural 

fracture orientation, spacing, and dip or to the variation 

between present-day and paleostress orientations.

Preexisting fractures intersecting the borehole at 

azimuths parallel or subparallel with the SHmin direction 

may also contribute to development of stress-induced 

breakouts. This appears to be the case for at least one 

wellbore enlargement in the eastern Anadarko basin, 

well OK16 (fig. 2). This wellbore enlargement is associated with a conductivity anomaly indicative of fracturing but is oriented in the direction inferred for breakouts. This situation is not interpreted to be a 90° rotation 

of the stress field but rather the formation of a stressinduced breakout within an interval of the wellbore 

weakened by preexisting northwest-oriented vertical 

fracturing or jointing.

An increase in the difference in horizontal stress 

magnitudes associated with gravitational loading, rock 

properties, and bedding thickness (Amadei and others, 

1988) may also contribute to the formation of fracture

In Situ Stress Analysis of Wellbore Breakouts, Oklahoma and Texas F13
<

2. Table 2. Wellbore enlargement data for the eastern Anadarko basin

 [Latitude and longitude are degrees north and west, respectively. Well depth is feet below sea level; ground level is elevation in feet; logged and data inter

3 number are totals of vertical feet and number of individual wellbore enlargements. Log quality: G, good; VG, very good; F, fair; P, poor. See table 1 fo

o^

% Well index 

§= number County

§ OK4

ff

* OK5

CD 

0)

5" OK9

(0

> OKU

a

S» OK15* 5"

g1 OK16

2.

3 OK17*

OK18

OK22*

OK27

OK36

OK38

OK40

OK100

OK102-

108*

OK105

Grady

Grady

Canadian

McClain

Grady

Grady

McClain

Grady

Grady

Kingfisher

Logan

Cleveland

Cleveland

Comanche

Canadian

Canadian

Latitude

34.887

34.930

35.485

35.141

34.985

35.216

34.928

34.872

34.729

35.749

35.905

35.346

35.319

34.725

35.659

36.530

Longitude

97.737

97.668

97.906

97.585

97.739

97.881

97.337

97.667

97.732

97.910

97.146

97.182

97.246

98.240

97.731

99.052

Ground 

level

1,064

1,155

1,342

1,210

1,070

1,242

1,115

1,003

1,229

1,091

902

1,205

1,086

1,206

1,250

1,394

Well 

depth

13,273

13,990

12,546

9,891

13,073

12,204

7,894

12,408

10,059

8,771

4,185

5,073

5,522

8,978

6,904

11,491

Logged 

interval

11,192-

13,219

8,824-

13,374

10,036-

12,536

5,778-

9,871

10,415-

13,031

10,544-

12,154

5,813-

7,863

9,278-

12,398

3,649-

10,059

6,091-

8,795

2,161-

4,100

3,033-

5,521

3,521-

5,521

1,182-

6,831

4,934-

6,902

9,491-

11,488

Data 

interval

11,192-

13,205

11,658-

12,666

10,086-

14,035

6,811-

8,541

11,641-

12,803

10,990-

11,861

5,847-

6,673

10,078

11,898

3,991-

6,318

6,091-

8,217

2,446-

3,911

3,133-

5,286

3,762-

5,186

3,202-

6,727

5,084-

6,707

10,223-

11,362

Composite of study area data

Oual

Feet

170

45

38

389

232

135

169

189

525

225

437

229

375

579

793

357

4,887

Number

4

4

4

8

5

4

4

4

9

6

7

4

4

5

5

7

84

Log Stati

G

F

VG

G

F

G

G

F

G

VG

G

P

F

F

P-G

G

*The distribution of directional data was bimodal with orthogonally oriented trends of unequal population size.
Table 3. Wellbore enlargement data for the Marietta basin

[Latitude and longitude are degrees north and west, respectively. Well depth is feet below sea level; ground level is elevation in feet; logged and data int

number are totals of vertical feet and number of individual wellbore enlargements. Log quality: G, good; F, fair; P, poor. See table 1 for explanation o

Well index

number County Latitude

OK32 Jefferson 34.135

OK55 1 Jefferson 33.103

OK522 Love 33.949

Ground

Longitude level

97.626 816

97.675 793

97.266 918

Well Logged

depth interval

6,871

9,934

10,547

4,471-

6,464

5,407-

6,527

8,911-

10,516

_ 

v>

g

(j>

0

w

£.

w

a

<

=

1

io

1

I

O

£

1

o>

i

S1

S

OK60 Love 33.976

OK612 Love 34.023

OK62 Love 34.022

OK64- Love 33.963

671

OK66 Love 33.956

OK72- Jefferson 34.137

83-S42

OK77- Love 34.004

78 l

OK792 Love 34.022

OK852 Love 33.960

Composite of study area data

97.387 930

97.492 855

97.476 840

97.320 785

97.331 845

97.595 839

97.474 913

97.476 876

97.352 954

8,123

8,028

7,708

9,123

8,799

7,999

7,819

7,760

8,399

'The distribution of directional data was bimodal with orthogonally oriented trends

5,054-

8,100

6,028-

9,771

5,590-

7,799

6,900-

9,126

6,739-

8,798

5,789-

7,998

5,774-

7,796

5,708-

7,745

6,333-

8,383

Data

interval Feet

5,987- 216

6,592

5,726- 152

6,446

8,939- 116

10,211

5,776- 115

7,908

7,214- 106

7,894

5,818- 421

7,619

6,228- 286

8,776

8,337- 162

8,635

7,049- 312

7,798

7,072- 163

7,698

6,508- 173

7,654

6,833- 151

8,189

2,373

Oua

Number

4

5

4

4

6

10

7

4

5

6

5

4

64

Log Sta

G

F

F

P

G

G

G-F

P

F-F

F-G

G

F

of unequal population size.

^The distribution of data was bimodal with orthogonally oriented trends of approximately equal population size.
m

E 

o

^ Table 4. Wellbore enlargement data for the Bravo dome area 

o. [Latitude and longitude are degrees north and west, respectively. Well depth is feet below sea level; ground level is elevation in feet; logged and data inte

3 number are totals of vertical feet and number of individual wellbore enlargements. Log quality: G, good; F, fair; P, poor. See table 1 for explanation o

3

? Well index

o, number

8 TXll

w

I TX12

3

I TX13 1

1

QD TX15

8

3 TX201

TX212

TX23

TX281

TX29

TX32

TX372

TX471

County

Oldham

Oldham

Oldham

Oldham

Oldham

Oldham

Oldham

Oldham

Oldham

Oldham

Oldham

Oldham

Latitude Longitude

35.370 102.306

35.465 102.372

35.379 102.260

35.390 102.163

35.443 102.379

35.355 102.301

35.388 102.331

35.328 102.368

35.297 102.335

35.371 102.213

35.366 102.237

35.404 102.330

Ground

level

4,020

3,279

3,615

3,257

3,500

3,706

3,715

3,575

3,542

3,539

3,590

3,451

Well

depth

4,202

4,857

4,475

2,781

4,757

3,733

4,076

4,064

3,235

3,750

3,596

6,887

Logged

interval

2,192-

4,198

2,861-

4,864

2,469-

4,469

1,438-

2,779

2,740-

4,747

2,833-

3,583

2,075-

4,075

1,965-

4,063

1,232-

3,232

1,650-

3,739

400-

3,618

837-

6,839

Data

interval

2,322-

3,244

3,446-

4,393

2,788-

3,655

2,291-

2,611

3,110-

3,747

3,031-

3,305

2,340-

3,157

2,428-

4,019

1,233-

1,744

2,453-

3,100

826-

2,786

1,227-

5,691

Composite of study area data

Feet

184

360

229

166

85

95

55

128

128

53

129

239

1,851

Number

8

7

7

4

4

4

4

6

4

4

4

10

66

Log

G

F

F

G

G

F

G

F

F

F

F

G

Qua

Stat

The distribution of data was bimodal with orthogonally oriented trends of approximately equal population size. 

The distribution of directional data was bimodal with orthogonally oriented trends of unequal population size.
wellbore enlargements in the study areas . Amadei and 

others proposed a model of gravity-induced variation in 

stress magnitudes in anisotropic, stratified rock masses 

by treating layered strata as finite mechanical units. This 

model predicts that induced components of horizontal 

stress can vary in magnitude between rock units, either 

less or more than the vertical stress.

Formation of randomly oriented wellbore enlargements associated with lower confining pressures at 

shallow depths (Dart, 1987; Springer, 1987) can generally be ruled out as a contributor to data scatter 

because near-surface (< 1,000 ft subsea) wellbore 

enlargements are commonly washed out and enlarged in 

both orthogonal directions. These data were not considered reliable and were not used.

Small differences in horizontal-stress magnitudes 

(Springer, 1987), as measured in the Stone and Webster 

Holtzclaw No. 1 well (fig. 4), may contribute to dispersion among enlargement orientations in the Bravo dome 

area. This cannot be said, however, for the eastern 

Anadarko and Marietta basins because in situ measurements of horizontal stress magnitudes are not available.

The observed randomness in wellbore enlargement 

orientations in the Marietta basin and Bravo dome areas 

is not thought to be related to a large horizontal stress 

ratio and variation in borehole shape (Morin and others, 

in press). Large horizontal stress differences were not 

observed in the Stone and Webster Holtzclaw No. 1 well 

(Stone and Webster Engineering Corporation, 1983), 

and the aseismicity of the study region (fig. 1) (Stone and 

Webster Engineering Corporation, 1983) suggests a 

small difference in regional horizontal stresses.

INFERRED STRESS DIRECTIONS AND 

RELATIVE STRESS MAGNITUDES

Directions of SHmax calculated from stress measurements (table 7) agree with directions of SHmax inferred 

from breakout data (table 8) in the study region. The 

average direction of SHmax inferred from hydraulicfracturing measurements for the region (fig. 1) is N. 50° 

E., and the average direction of SHmax inferred from 

breakout data for the three study areas is N. 56° E.

The relative magnitudes of S1} S2 , and S3 within the 

study region can be evaluated from available hydraulicfracturing data, evidence of recent faulting, and the 

frequency of breakout occurrence with depth. Values of 

Sv SHmin , and SHmax magnitudes from hydraulicfracturing measurements exist for one well (Stone and 

Webster Holtzclaw No. 1) within the study region (fig. 2, 

table 7). The relationship of principal stress magnitudes 

from the Stone and Webster Holtzclaw well No. 1 (fig. 4),

located 80 km southeast of the Bravo dome area in the 

Palo Duro basin, is

&1 >S2 >S3 , or Sv >SHmax >SHmin , or SV >SNE >SNW .

The ratio of Sv to SHmax is 1.19 and the ratio of SHmax to 

SHmln is 1.28 for siltstone and limestone formations 

(table 7). Stresses measured for intervening salt 

formations deviate from this stress relationship. Because 

salt is an elastoplastic rock, stresses measured in salt 

formations are not considered reliable indicators of the 

regional stress field (Borjeson and Lamb, 1988).

In the Arbuckle uplift (fig. 1), surface overcoring 

stress measurements (table 7) are an unreliable indication of stress conditions within the region because of 

the domed structure of this igneous body (H.S. Swolfs, 

oral commun., 1988). Breakout stress data from the 

vicinity of the Arbuckle uplift agree only generally with 

stress directions calculated from the overcoring measurements in this area.

Stress-magnitude calculations using mini-frac 

(H.S. Swolfs, oral commun., 1988) and leak-off test data 

(Ervine and Bell, 1987) could not be made for the three 

study areas because these types of borehole pressure test 

data are not available.

Relative horizontal stress differences may be 

approximately inferred by examining the frequency of 

breakout occurrence with depth. Initiation of shearfailure spalling and rate of breakout development probably are controlled by the horizontal stress difference 

about the wellbore and the confining strength of the rock 

(Mastin, 1984; Haimson and Herrick, 1985; Zoback and 

others, 1985). Assuming that the fracture gradient, the 

pressure per unit depth required to fracture or cause the 

rock to separate (Society of Professional Well Log 

Analysts, 1984), and the magnitudes of Slt S2 , and S3 all 

increase at their respective rates with depth, the following 

conditions are likely true: (1) when breakouts do not 

occur or are random in orientation, SH^^SH^; 

(2) when breakouts do occur, SHmax/SHmin > 1 (Zoback 

and others, 1985); (3) when the frequency of breakout 

occurrence increases with depth, the horizontal stress 

difference increases with depth (because the fracture 

gradient is also assumed to be increasing with depth but 

at a slower rate); (4) when the frequency of breakout 

occurrence remains about the same with depth, the 

horizontal stress difference is probably constant; and 

(5) when the frequency of breakout occurrence 

decreases with depth, the horizontal stress difference 

may decrease with depth or increase at a slower rate than 

the increase in the fracture gradient. Thus, breakout 

occurrence and the extent of breakout development in 

any given area is likely associated with the rates at which 

in situ stresses change with depth.

In a seismically active area where S1 is horizontal, 

such as the New Madrid area of the Mississippi EmbayIn Situ Stress Analysis of Wellbore Breakouts, Oklahoma and Texas F17
EASTERN

ANADARKO

BASIN

Undetermined!?)

F18 Evolution of Sedimentary Basins Anadarko Basin
ment (Zoback and Zoback, 1980), stress-induced wellbore enlargements from two wells (Dart, 1987) appear to 

be of greater vertical length (table 9) and have a distinct, 

characteristic shape (as seen on the dipmeter log). In 

contrast, in a relatively aseismic area such as the Palo 

Duro basin (Stone and Webster Corporation, 1983), 

where Sj is vertical and where in the near surface S2 may 

not be significantly greater than S3 (table 7)(Borjeson 

and Lamb, 1987), wellbore enlargements in nearby wells 

(Bravo dome area), on average, appear to have shorter 

vertical lengths (table 9) and less well defined trace 

character on the dipmeter log (log quality on table 4). If 

wellbore enlargements are compared for areas having 

different levels of seismic activity but with similar 

sedimentary rock types, as is probably the case for the 

New Madrid seismic zone and the Bravo dome area, 

wellbore enlargement length and frequency of occurrence are likely a function of the horizontal stress 

difference.

Figures 6-8 illustrate the relationship of wellbore 

enlargement vertical length and frequency of occurrence 

to depth. For the eastern Anadarko basin data (fig. 6), 

frequency of breakout occurrence (number) does not 

decrease with depth for the logged interval ( 3,000- 

 13,000 ft); however, breakout length does decrease 

with depth (fig. 6). This decrease is expected given the 

longer time period during which breakouts can develop 

in the upper part of the borehole and the subsequent 

longer exposure time to drill-string wear. Although the 

marked decrease in breakout occurrence between depths 

of about 6,000 and 9,000 ft (fig. 6) cannot be accounted 

for, it may be the result of an increase in rock tensile 

strength or a decrease in the ratio of horizontal stresses 

within this interval of Middle Pennsylvanian (Desmoinesian and Atokan) and Lower Pennsylvanian (Morrowan and Springeran) formations.

In the Marietta basin (fig. 7), both breakouts and 

fracture wellbore enlargements occur at approximately 

the same frequency with depth. The fact that they seem 

to terminate at about 9,000 ft may be related to the small 

number of wells (three) that were logged below this 

depth. In the Marietta basin data, scatter among breakout orientations contrasts with the tight grouping of 

northeast-oriented fracture-related wellbore enlargements. This contrast may be a function of the ratios of 

principal stresses in situ. A decrease in the ratio of

Figure 9 (facing page). Vertical bar graphs of wellbore 

enlargement type and rock type of enlargement occurrence 

for the eastern Anadarko basin, Marietta basin, and Bravo 

dome study areas. Bars represent percentages of the total 

data set for each study area. Enlargement types: B'out, 

breakout; Frac, fracture; (?), undetermined. Rock types: Sh, 

shale; Ss, sandstone; Ls, limestone; Dolo, dolomite; Silt S, 

siltstone; Ign, igneous; Clast, clastic.

horizontal stresses in the Marietta basin may contribute 

to scatter among breakout orientations, whereas an 

increase in the ratio of Sv to SHmax may contribute to 

drilling-induced hydraulic fracturing of the wellbore and 

the formation of fracture enlargements. In normalfaulting stress regimes where S1 is vertical, drillinginduced hydraulic fracturing is more likely to occur than 

in compressive stress regimes where Sj is horizontal 

(Healy and others, 1984; Stock and others, 1985).

Breakout and fracture wellbore enlargements 

occur with depth at approximately the same frequency 

(number) in the Bravo dome area data (fig. 8). Fracture 

enlargements have longer vertical lengths than breakouts 

and, as in the Marietta basin data, form a tighter 

grouping of northeast-oriented fracture-related wellbore 

enlargements than northwest-oriented breakout wellbore enlargements (fig. 8). Neither breakouts nor 

fracture-related wellbore enlargements occur below 

5,750 ft. Only 1 of the 12 well data sets had a logged 

interval extending below this depth. In the logging 

interval above 5,750 ft, both breakout and fracture wellbore enlargement development decrease with depth. 

Very few wellbore enlargements of either type occur 

within the 1,500-ft interval between 4,250 and 7,500 ft 

(fig. 8). This apparent decrease in wellbore enlargement 

development below 4,250 ft may indicate changing stress 

ratios (Sv/SHmax and SHmax/SHmin ) with depth. The 

tight grouping of well-developed fracture-related 

enlargements in the Bravo dome area data may indicate 

a normal-faulting stress regime. Hydraulic-fracturing 

measurements of Slf S2 , and S3 from the Stone and 

Webster Holtzclaw No. 1 well in the northern Palo Duro 

basin (fig. 4) confirm that this part of the Texas 

Panhandle (fig. 1) is a normal-faulting stress regime.

Several important observations can be made 

concerning the state of stress within the study region.

1. Strike-slip and reverse-fault movement on the 

Meers fault (fig. 2) and possible displacement on other 

west-northwest-oriented faults in the Frontal fault 

system of southern Oklahoma are inconsistent with a 

normal-faulting stress regime indicated for the Texas 

Panhandle.

2. Hydraulic-fracturing measurements in the 

Stone and Webster Holtzclaw No. 1 well (fig. 4, table 6) 

were made at shallow depths (1,854-2,794 ft below 

ground surface). The ratios of Sv/SHmax and SHmax/ 

SHmin are close to 1.0. The difference in SHmax and 

SHmin magnitudes increases with depth, whereas the 

difference in Sv and SHmax magnitudes decreases with 

depth. The ratios of stresses may be different at depth 

than they are near the surface.

3. The Bravo dome and northern Palo Duro 

basin areas lie on or very near the boundary between the 

southern Great Plains and Midcontinent stress provinces. 

The states of stress for these two provinces are

In Situ Stress Analysis of Wellbore Breakouts, Oklahoma and Texas F19
Table 5. Stratigraphic units logged

[Lithologic abbreviations: sandstone (SS), limestone (LS), shale (SH), dolomite (DOLO), conglomerate (CONG), and mudstone (MDS). Quotation mar

generally drillers' terms. Permian(?)=undifferentiated Wolfcampian-age clastic and limestone formations. Stratigraphic nomenclature follows usage of 

(1971), Preston and others (1982), McGookey and Goldstein (1982), American Association of Petroleum Geologists (1983a, b), and Petroleum Inform

formation tops]

System Series

Eastern Anadarko basin Marietta basin

Lithologic unit Lithologic unit

Permian

Leonardian

Wolfcampian

C

Virgilian

Missourian

Desmoinesian

Pennsylvanian

(part)

Atokan

Pawhuska Formation (LS) 

"Endicott sand" 

"Lovell sand" 

"Tonkawa sand" 

Hoxbar Group

Avant Limestone Member 

Dewey Limestone 

Hogshooter Limestone 

"Layton sand" 

"Checkerboard sand" 

"Cleveland sand" 

"Wade sand" 

Confederate Limestone Member

Deese Group

"Hart sand"

"Big Lime"

"Oswego lime" 

Cherokee Group

"Prue sand"

Verdigris Limestone

"Skinner sand"

"Pink lime"

"Osborne sand"

"Red Fork sand"

Inola Limestone

"Bartlesville sand"

"Gibson sand"

Atoka Formation (SH.LS)

Novi Limestone

Hoxbar Group 

Daube Limestone 

Anadarche Limestone 

"Hewitt lignite" 

"Palacine shale" 

Confederate Limestone Member 

"Chubbee sand"

Deese Group (LS,SS,SH) 

"Detrital zone" 

"Lower Deese" (coal) 

"Maroon shale" 

"Pennsylvanian sand" 

"Sanders" ("Lower Deese Group"?, SS.SH)

C

C
Table 5. Continued

System Series

Eastern Anadarko basin Marietta basin 

Lithologic unit Lithologic unit 

Morrowan

Pennsyl- Springerian

vanian

(part)

Dornick Hills Group 

Primrose Sandstone

Springer Group (SH)

"Upper Norton sandstone" 

"Cunningham sand" 

"Britt sandstone"

Dornick Hills Group (SH,SS,LS,CONG) 

"Pennsylvanian detrital zone"

Situtress Analysis ofWellbore Breakouts, Oklahoma andTexas

pian

Upper 

Lower 

Devonian

Silurian Lower

Upper

Middle 

Ordovician

Lower

Upper 

Cambrian

Precambrian

Mayes Limestone 

Sycamore Limestone

Woodford Shale 

"Misener sandstone" 

Hunton Group (LS) 

Bois d'Arc Limestone

Chimneyhill Limestone

Sylvan Shale 

"Sylvan dolomite" 

Viola Limestone 

Simpson Group 

Bromide Formation (SS.LS) 

Tulip Creek Formation (SS) 

McLish Formation (SS)

Oil Creek Formation (DOLO,LS, SH, SS) 

Joins Formation (DOLO.LS) 

Arbuckle Group (LS)

Timbered Hills Group 

Reagan Sandstone (SH.CONG)

Granite

Mayes Limestone 

Sycamore Limestone

Woodford Shale 

Hunton Group (LS.SH)

Viola Limestone 

Simpson Group 

Bromide Formation (LS.SS)

McLish Formation 

Birdseye Limestone Member 

"Green shale" (Oil Creek? Formation)
Table 6. Wellbore enlargement type, frequency of occurrence, and orientation

[Azimuth (in degrees) is the median for every 10° interval between 90° W. and 90° E. Wellbore enlargement type and frequency are shown. Type: 

B, breakout; F, fracture; asterisk (*), uncertain. Frequency of occurrence is the number of discrete wellbore enlargement intervals. Quotation 

marks indicate informal usage of names. Permian (?) indicates undifferentiated Wolfcampian-age clastic and limestone formations]

Formation

Azimuth

West East

85 75 65 55 45 35 25 15 5 5 15 25 35 45 55 65 75 85

EASTERN ANADARKO BASIN

Avant Limestone Member

Hogshooter Limestone 

"Checkerboard sand"

"Cleveland sand"

Confederate Limestone Member

Deese Group 

"Hart sand" "Big Lime" 

"Prue sand"

"Osbome sand"

Atoka Formation

"Chester limestone"

"Mississippi limestone" 

Hunton Group 

Bois d'Arc Limestone

Chimneyhill Limestone 

Sylvan Shale 

Viola Limestone

Bromide Formation

Tulip Creek Formation 

McLish Formation

Oil Creek Formation

Arbuckle Group 

Reagan Sandstone

B2 B2 Bl

Bl Bl 

Bl B3 Bl Bl

Bl

B2

Fl Fl B2 Bl B2 

Bl

Bl

Bl

Bl

Bl

*1 

Bl Bl 

Bl B2 Bl

B2 

*1 B2 Bl Fl Fl 

*1 Bl B4 B3 B3 B3 Bl

B3 B2 Bl

Bl Bl 

Bl Bl Bl

Bl B2

Bl Bl 

Bl Bl

Fl

MARIETTA BASIN

Confederate Limestone Member

Deese Group 

"Maroon shale"

"Sanders"

Dornick Hills Group 

Woodford Shale

Viola Limestone

Simpson Group 

Bromide Formation

Birdseye Limestone Member 

Green shale (Oil Creek Formation)

Bl

*2 B3 B3 Bl 

Bl Bl Fl Fl

B2 Bl

*1 Bl Bl Bl F2 F2

*3 B2 B6 B2 Bl F2 F4 Fl

Bl Bl Fl 

Bl F2

Fl

Fl

Fl 

Fl

F2 F2 Fl

F2 Fl

Fl

BRAVO DOME AREA

"Panhandle lime"

"Brown dolomite"

Permian (?) 

Cisco Group 

"Pennsylvanian shale 

"Missourian shale"

"Upper granite wash" 

Granite

Bl

*1 Bl B2 B5 B6 B3 B2 B3 *2 Fl F4 F3

Bl B2 Bl 

*1 F2 F2 

B2 Bl Bl Bl Bl *2 Fl F3 Fl 

Bl

Bl F2 

Bl Fl

F2 Fl

Fl

interpreted as being opposite (Zoback and Zoback, 

1980). The southern Great Plains stress province is a 

region of extensional tectonics with SHmin =SNNE, 

whereas the Midcontinent stress province is a region of 

compressional tectonics with SHmax =SNE (Zoback and 

Zoback, 1980). Therefore, near-surface stress conditions 

in the Bravo dome area may deviate from those farther 

east within the Midcontinent stress province.

4. In view of available hydraulic-fracturing data 

(table 7) and the apparent recent strike-slip and reverse 

movement on the Meers fault (Ramelli and others, 1987; 

Luza and others, 1987; Madole, 1988), a transitional 

stress regime is inferred for the study region, changing 

from normal faulting (Sv >SHmax >SHmin or 

SV >SN.E >SNW ) in the Texas Panhandle to strike-slip 

(SHmax >Sv >SHmin or SNE >Sv>SNW ) and reverse

F22 Evolution of Sedimentary Basins Anadarko Basin
Table 7. In situ stress data, south-central United States

[Study type: HF, hydraulic fracturing; OC, overcoring. Leaders (--) indicate no data available]

type

HF1

OC2

HF3

Location

Kingfisher Co., Okla.,

eastern Anadarko basin.

Johnston Co., Okla.,

Arbuckle uplift.

Randall Co., Texas,

Palo Duro basin

Rock type

Granite

Siltstone

Anhydrite

Salt

Salt

Limestone

Depth (ft from 

ground surface)

4.5

1,854

2,334

2,434

2,505

2,794

Sy (psi)

0

1,835

2,335

2,780

2,950

2,810

SHmin (psi)

-

519

1,110

-

2,915

3,500

1,940

SH max (psi)

--

1,075

1,260

~

«

2,650

SH max (direction)

N. 65° E.

N. 94° E.

N. 30° E.

N.40° E.

N. 60° E.

N. 60° E.

N. 45° E.

von Schonfeldt and others (1973). 

2From Hooker and Johnson (1969). 

From Borjeson and Lamb (1987).

Table 8. Inferred stress directions from wellbore enlargement orientations

Location

Eastern Anadarko basin 

Marietta basin 

Bravo dome area

Primary rock type 

in which 

enlargements occur

Limestone and shale 

Limestone and shale 

Dolomite and shale

Enlargment depth 

interval (ft subsea)

From To

-2,446 -13,205 

-5,726 -10,499 

-924 -6,516

SHmax from 

breakout data

N. 78° E. 

N. 41° E. 

N. 49° E.

Azimuth of 

fracture 

enlargment

N. 51° E. 

N. 65° E. 

N. 37° E.

Table 9. Comparison of wellbore enlargement data from different stress regimes 

[Number of wellbore enlargements is a total from all well-data sets, regardless of statistical quality]

Number of Vertical feet 

Number of Total vertical wellbore of wellbore 

Study area (stress regime) well-data sets feet logged enlargements enlargement

Mississippi Embayment 1 

Eastern Anadarko basin^ 

Marietta basirr 

Bravo dome area4

1 

14 

16 

18

5,471 

40,637 

35,971 

42,406

11 

82 

88 

108

1,784 

3,700 

2,851 

3,364

Number of 

wellbore 

enlargements 

per well -data 

set (avg.)

11.0 

5.9 

5.5 

6.0

Average 

Vertical feet Average of wellbore 

of wellbore vertical enlargements 

enlargements length (ft) 1,000 ft of 

per well-data of wellbore borehole 

set (avg.) enlargments logged

1,784 

264 

178 

187

162 

45 

32 

31

2.0 

2.0 

2.5 

2.6

Compressional stress regime.

3Extensional (?) stress regime. 

Extensional stress regime.

faulting (SHmax >SHmin >Sv or SNE >SNW >SV ) in 

Oklahoma.

Given such a limited stress-magnitude data base 

(tables 7, 8), speculation on the relative magnitudes of 

vertical or horizontal stresses within the study region is 

problematic.

TRANSPRESSIONAL (OBLIQUE 

COMPRESSIONAL) STRESSES AND 

FAULT-BOUNDED BLOCKS

Many of the data sets from the Marietta basin and 

the Bravo dome area are bimodal (figs. 2-4, 7, 8, 10), 

whereas in the eastern Anadarko basin bimodal data sets

of enlargement orientations are less common (figs. 2, 6, 

10). The abundance of bimodal-orthogonal data sets in 

the Marietta basin and the Bravo dome area reflects the 

fracture history and suggests a local change in stress 

conditions related to mapped subparallel surface faults in 

the Marietta basin (fig. 3) and mapped subparallel 

basements faults in the Bravo dome area (fig. 4). Well 

locations in the eastern Anadarko basin (fig. 2) are 

distributed over a broad area and generally are not 

located between subparallel faults.

Preexisting fractures in an array of orientations 

may exist within blocks bounded by subparallel faults. 

The area between or above subparallel discontinuities 

likely has experienced an intense fracturing history

In Situ Stress Analysis of Wellbore Breakouts, Oklahoma and Texas F23
00 

0) w5"

169° 169°

20-i 20 -\

10

04 

i i

W EASTERN ANADARKO BASIN N

260° 280°

80° I 100°

W

300° 320° 340 

120' 140° 160 

MARIETTA BASIN

0 X /^

0- r^ i i i

1 61

'"~\

0\-e/"

260° i 280° 300° 320° 340° 

80" ' 100 120° 140° 160° 

W MARIETTA BASIN

 

A 

0°

180

N

38°

30 -i

I- 20 -

10 -

I

W BRAVO DOME AREA

Figure 10. Histogram of wellbore enlargement data for the eastern Anadarko basin, Marietta basin, and Bravo dome study a

distribution of enlargement orientations from the Marietta basin and the Bravo dome areas. Only data from wells with A-C statist

distribution were used (tables 1-4). Plots are a function of the percentage of the data used, either feet or number. Plot groups: 

azimuth; B, Cumulative number of individual wellbore enlargements for a given azimuth.
resulting in formation of sets of favorably oriented 

fractures or joints that would increase the likelihood of 

fracture-related wellbore enlargement development.

Where fracture-related enlargements have formed 

in response to drilling-induced hydraulic fracturing, an 

increase in the occurrence of fracture-related wellbore 

enlargements may reflect a local change in the regional 

stress field. Drilling-induced hydraulic fracturing is more 

likely to develop in a normal-faulting stress regime 

(Healy and others, 1984; Stock and others, 1985). An 

extensional (normal) faulting stress regime in the Marietta basin study area suggested by the occurrence of 

fracture wellbore enlargements may be a local stress 

anomaly in an otherwise compressional stress regime. 

Rogers (1984) and Hempton and Neher (1986) described structural settings in which extensional and compressional stresses develop between and near the ends of 

left-stepping and right-stepping en echelon strike-slip 

faults in response to regional horizontal compression 

oblique (transpressional) to their strike. Subparallel 

faults in the Marietta basin and Bravo dome area are not 

en echelon by definition; however, these two areas 

structurally resemble the areas described by Rogers 

(1984) and Hempton and Neher (1986). This similarity 

of structural settings and orientations of horizontal 

stresses suggests that extensional stress conditions 

(normal-faulting regime) may exist within blocks 

bounded by west-northwest-trending subparallel faults 

where SHmax is oblique to their strike.

A comparison of the calculated orientations of 

SHmax from breakout data (table 8) shows a 37° 

difference between the eastern Anadarko and Marietta 

basins and a 29° difference between the eastern Anadarko basin and the Bravo dome area. SHmax orientations calculated for the Marietta basin and the Bravo 

dome area differ by only 8°. The similarities of these two 

differences (37° and 29°) may correlate with the apparent 

similarities in structural settings of the Marietta basin 

and the Bravo dome area and with the possible local 

variation in horizontal stresses associated with the 

orientation of SHmax and west-northwest-trending subparallel faults.

CONCLUSIONS

From wellbore breakout data, SHmax is inferred to 

be N. 78° E. for the eastern Anadarko basin, N. 41° E. for 

the Marietta basin, and N. 49° E. for the Bravo dome 

area. Bimodal sets of wellbore enlargement data are 

interpreted as consisting of a north-northwest to northwest mode of stress-induced breakouts and an eastnortheast to northeast mode of stress-related fracture 

enlargements. Fracture-related wellbore enlargements 

are likely associated with drilling-induced hydraulic 

fracturing of the wellbore or with preexisting vertical

fractures or closely spaced joint sets intersecting the 

wellbore. The occurrence of breakouts and fracturerelated wellbore enlargements does not seem dependent 

on any sedimentary rock type. The stress regime for the 

study region most likely is transitional between normal 

faulting at shallow depths in the Bravo dome area of the 

Texas Panhandle and strike-slip and reverse faulting in 

Oklahoma, exclusive of the Marietta basin. Bimodalorthogonal data sets of wellbore enlargement orientations may be more likely to develop in wells in areas 

bounded by subparallel faults striking oblique to the 

SHmax direction (transpressional stress). An extensional 

(normal-faulting) stress regime in the Marietta basin 

may be a local fault-related stress anomaly.

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Marcher, M.V., and Roberts, J.F., 1972, Geology and 

earth resources of Oklahoma, an atlas of maps and cross 

sections: Oklahoma Geological Survey Educational 

Publication 1, 8 p.

Johnson, K.S., Bruchfield, M.R., and Harrison, W.E., 1984, 

Guidebook for Arbuckle Formation field trip, southern 

Oklahoma: Oklahoma Geological Survey Special 

Publication 84-1, 23 p.

Johnson, K.S., and Denison, R.E., 1973, Igneous geology of the 

Wichita Mountains and economic geology of Permian 

rocks in southwest Oklahoma: Geological Society of 

America Guidebook for Field Trip 6, 35 p.

Jordan, Louise, 1957, Subsurface stratigraphic names of 

Oklahoma: Oklahoma Geological Survey Guidebook VI, 

220 p.

____ 1967, Geology of Oklahoma A summary: Oklahoma 

Geology Survey, Oklahoma Geological Notes, v. 27, no. 

12, p. 215-229.

Luza, K.V., Madole, R.F., and Crone, A.J., 1987, Investigation 

of the Meers fault, southwestern Oklahoma; final report: 

Oklahoma Geological Survey Special Publication 87-1, 

75 p.

Madole, R.F., 1988, Stratigraphic evidence of Holocene 

faulting in the mid-continent; the Meers Fault, southwestern Oklahoma: Geological Society of America 

Bulletin, v. 100, no. 3, p. 392-401.

Mastin, L.G., 1984, The development of borehole breakouts in 

sandstone: Stanford, California, Stanford University, 

M.S. thesis, 101 p.

McGookey, D.A., and Goldstein, A.G., 1982, Structural 

influence on deposition and deformation at the northwest margin of the Palo Duro Basin, in Geology and 

geohydrology of the Palo Duro Basin, Texas Panhandle A report on the progress of nuclear waste isolation 

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Moore, G.E., 1979, Pennsylvanian paleogeology of the 

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Morin, R.H., Newmark, R.L., Anderson, R.M., and Barton, 

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Morris, R.C., 1974, Sedimentary and tectonic history of the 

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University of Texas, Austin, Bureau of Economic 

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Perry, WJ., Jr., 1989, Tectonic evolution of the Anadarko Basin 

region, Oklahoma: U.S. Geological Survey Bulletin 

1866-A, 19 p.

Petroleum Information Corporation, 1982, The deep Anadarko 

Basin: 359 p.

___ 1983, Oil and gas map of the United States including 

basins, uplifts, and basement rocks. Scale 1:3,500,000.

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Raja, Reddy, 1982, An evaluation of water resources by 

enhanced on recovery oeprations, cement field, Cad do 

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Mapping of stress field in the upper Earth's crust of the 

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U.S. Geological Survey, 78 p.

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Wickham, J.S., and Denison, R.E., eds., Structural style 

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Wilhelm, S.J., and Morgan, K.W., 1986, Utilization of Landsat 

thermatic-mapper data for lineament analysis of the

Slick-Hills area: Oklahoma Geological Survey Guidebook 24, p. 35-39.

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R.M., 1985, Well bore breakouts and in situ stress: 

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F28 Evolution of Sedimentary Basins Anadarko Basin frU.S. GOVERNMENT PRINTING OFFICE: 1990-573-049/26014
SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS

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