mappingbook (William A. Thomas)

William A. Thomas

With a Foreword by
Philip E. LaMoreaux

American Geological Institute
In cooperation with
Association of American State Geologists
Geological Society of America
National Park Service
U.S. Geological Survey

 value of geologic maps

geologic maps are the single most important and
valuable tool we have for understanding and living
with the Earth around us. Their usefulness is so broad
that geologic maps are the most requested scientific product
produced by state and federal geological surveys. Kentucky’s
experience with geologic maps exemplifies their value and
utility.

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contents

Using Geologic Maps for Habitat
Prediction Tim Connors 28
2 Geologic Maps and Cave Resources
Kentucky Geological Survey 30
3 Geologic Maps and Mineral Resources
Jonathan G. Price 32
4 Geologic Map Delineates Landslide
Hazards Gregory C. Ohlmacher,
James R. McCauley, John C. Davis 34
5 Geologic Map Depicts Sinkhole
Susceptibility David K. Brezinski,
James P. Reger, Gerald R. Baum 36
6 Geologic Maps Identify Landslide
Hazards Russell W. Graymer,
Richard J. Pike 38
7 Geologic Map Helps To Protect
Groundwater William A. Thomas,
Willard E. Ward, W. Edward Osborne 40
8 Geologic Map Guides Earthquake
Damage Prediction Scott D. Stanford 42
9 Geologic Maps Identify Post-Wildfire
Hazards Vince Matthews, David Gonzales 44
10 Geologic Maps Guide the Delineation
of Ecosystems Scott Southworth,
Danielle Denenny 46
11 Geologic Map Delineates Volcanic Hazards
Joe D. Dragovich, David K. Norman 48
12 Geologic Maps Delineate Sand and Gravel
Resources Beth L. Widmann, Jim Cappa 50
13 Geologic Maps Identify Could Resources
and Past Mining Clifford H. Dodge 52
14 Geologic Map Guides Transportation
Planning Edward C. Murphy 54
15 Geologic Map Aids Mitigation of
Earthquake Damage George Plafker 56
16 Using Geologic Maps To Find
Groundwater Peggy S. Johnson 58
Glossary 60
Credits 61
State Geological Surveys 62
Index 63
AGI Environmental Geoscience Program
& AGI Foundation 64

Geological Structures and Maps

Geological Structures
and Maps
A PRACTICAL GUIDE

Geological Structures
and Maps
A PRACTICAL GUIDE
Third edition
RICHARD J. LISLE
Cardiff University

 

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Contents

Geological Maps 

 Uniformly Dipping Beds 

 Folding 

 Faulting 

 Unconformity 

 Igneous Rocks 

 Folding with Cleavage
Further Reading

Preface

GEOLOGICAL maps represent the expression on the earth’s
surface of the underlying geological structure. For this
reason the ability to correctly interpret the relationships
displayed on a geological map relies heavily on a knowledge
of the basic principles of structural geology.
This book discusses, from first principles up to and
including first-year undergraduate level, the morphology of
the most important types of geological structures, and
relates them to their manifestation on geological maps.
Although the treatment of structures is at an elementary
level, care has been taken to define terms rigorously and in
a way that is in keeping with current professional usage. All
too often concepts such as ‘asymmetrical fold’, ‘fold axis’
and ‘cylindrical fold’ explained in first textbooks have to be
re-learned ‘correctly’ at university level.
Photographs of structures in the field are included to
emphasize the similarities between structures at outcrop
scale and on the scale of the map. Ideally, actual fieldwork
experience should be gained in parallel with this course.
The book is designed, as far as possible, to be read
without tutorial help. Worked examples are given to assist
with the solution of the exercises. Emphasis is placed
throughout on developing the skill of three-dimensional
visualization so important to the geologist.
In the choice of the maps for the exercises, an attempt
has been made to steer a middle course between the
artificial-looking idealized type of ‘problem map’ and real
survey maps. The latter can initially overwhelm the
student with the sheer amount of data presented. Many of
the exercises are based closely on selected ‘extracts’ from
actual maps.
I am grateful to the late Professor T.R. Owen who
realized the need for a book with this scope and encouraged
me to write it. Peter Henn and Catherine Shephard of
Pergamon Books are thanked for their help and patience.
Thanks are also due to Vivienne Jenkins and Wendy
Johnson for providing secretarial help, and to my wife Ann
for her support.

FUNCTIONS AND PROPERTIES OF DRILLING FLUIDS

• What is Drilling Fluid or Mud?
• “It is a mixture of liquids and chemicals that allow the drilling and completion of a well”.
• Drilling Fluid has to provide many functions in order that these objectives be achieved.

Primary Functions 

• Lift and Carry Drilled Cuttings to Surface
• Control Formation Pressures
• Maintain a Stable “In Gauge” Hole
• Cool and Lubricate the Bit
• Lubricate the Drill String
• Secure Hole Information
• Power / Transmit signals from Downhole Tools
• Prevent fluid from entering the formation
• Permit separation of solids at surface
• Form a thin low permeability filter cake  

Negative Functions

• Not injure people or be damaging to the environment.
• Not require unusual or expensive methods of completion
• Non damaging to the fluid bearing formation
• Not corrode or cause excessive wear of drilling equipment
• Ridiculously expensive

• The Drilling Fluid Company must be able to:
• Provide cost effective solutions to the operators drilling problems
• Maintain the mud properties
• Provide an adequate supply of products on site and at the base
• Provide adequate reporting
• Engineer the fluid in widely differing conditions and locations
• Provide back up testing facilities
• Avoid damaging the reservoir  

Balancing Sub-Surface Pressures 

lThe pore pressure depends on:

The density of the overlying rock

The density of the interstitial fluid

Whether the rock is self supporting or is 

supported by the fluid.

Tectonic activity

Surface terrain

 

lIf the fluid hydrostatic pressure does not balance the 

pore pressure the following may occur:

Influxes of formation fluid into the wellbore

Lost circulation

Hole Instability

Stuck pipe

  1) Balancing Sub-Surface Pressures

lThe pressure balancing the formation pressure is composed from the hydrostatic pressure under static conditions:

nP = Depth (ft) x Density (ppg) x 0.052

lUnder circulating conditions the effective pressure is increased by the pumping pressure. This forms the Equivalent Circulating density (ECD):

 

2) Remove Cuttings From the Well Bore

The most important parameter is the Annular Velocity (A.V.)

Where possible the annular velocity should be 100 ft/min, higher in deviated holes.

In large hole sections the A.V. can be as low as 20 ft/min.

If the A.V. is insufficient to clean the hole the 

 viscosity must be increased

 

For top hole high viscosities must be used

Cuttings removal is harder in deviated and 

horizontal holes as the vertical component of the 

mud is reduced.

 3) Suspension of Solids

Whenever the pumps are switched off solids will start

 

 to settle. This can result in:

 

Bridging off of the wellbore

 

Stuck pipe

 

Hole fill

 

Loss of Hydrostatic

 

A gel structure is required to suspend the cuttings

 

under zero shear conditions:

 

The gel structure is caused by time dependant 

 

attractive forces which develop in the fluid. 

 

The longer the fluid is static the stronger these

 

 forces become

 

The gel structure should be easily broken

 

The gel properties are especially important for

 

 deviated and horizontal wells as the distance

 

solids have to settle is very small

 

4) Minimise Formation Damage

 

Damage to the formation while drilling to the 

 resevoir:

Formation swelling (Normally clay and 

 

Salt formations)

 

Washouts (Clay and Salt formations or 

any unconsolidated formation)

This can result in:

 

–Difficult directional control

–Poor zonal isolation

–Excess mud and cement costs

–Poor Hole Cleaning

–Stuck Pipe

–Difficult fishing jobs

 

 

 

Damage to the reservoir will result in loss of production or  the need for remedial treatment. This can result from:

Solids blocking reservoir pores

Emulsion droplets blocking reservoir pores

Swelling clays

Ions from the formation and drilling fluid forming insoluble salts

5) Isolate the Fluid From the Formation

The differential pressure forces fluid into the wellbore, resulting  in whole mud or filtrate entering the formation. Either, or both, of these is undesirable because:

The loss of whole mud into the wellbore is expensive and damaging

The loss of filtrate into the wellbore may cause formation damage

The flow of fluid is affected by the 

formation of a filter cake

The  filter cake  reduces the flow of fluid 

into the formation.

Special additives are added to improve 

the cake quality:

–Bridging material

–Plate like material

–Plugging material

The filter cake should be thin with a low 

permeability

This avoids reducing the effective 

hole diameter

It also reduces the chance of 

differential sticking

   

6) Cooling and Lubrication

The drilling fluid removes heat from the bit

 which is then dispersed at the surface

Fluid formulations are not changed to

 improve this function

Very occasionally the temperature of 

the fluid exceeds the flash point. In this

 case it is necessary to improve surface

 cooling

Extra lubrication may be required between

 the drill string and the casing or wellbore, 

especially in directional wells

Liquid additives are used (IDLUBE), or 

Oil based mud

Solid additives are sometimes used 

such as glass beads or nut plug

Drill pipe rubbers are sometimes 

added to reduce wear between the 

casing and drill pipe

 7) Support Part of the Tubular Weight

lAids in supporting part of the weight

 of the drill string and casing

 

lThe degree of buoyancy is directly 

 

proportional to the density of the 

 

fluid.

The fluid density is never 

 

changed to increase the buoyancy

 8) Maximise Penetration Rates

The fluid properties greatly 

 

influence penetration rates by:

 

Removing cuttings from 

 

below the bit and wellbore

 

Reducing the cushioning 

 

effect of solids between the

 

 bit teeth and the formation

 

Reducing the hydrostatic

 

 differential

 

Increasing the jet velocity

 

 

  9) Control Corrosion

 

The fluid should be non corrosive to the:

Drill string

Casing

Surface equipment

Corrosion can lead to:

Wash outs

Twist offs

Pump failure

Surface Leaks

 

11) Other Functions

 

Power Down hole motors

Turbines to turn the bit or 

power MWD / LWD equipment

Transfer information from 

measurement equipment to the

 surface

This is done with a pressure

 pulse