Multi-dimensional Land Seismic Data-acquisition Techniques and Random Survey Design

162 Pages·2007·31.06 MB·English

Copyright
by
Engin Alkan
2007
MULTI-DIMENSIONAL LAND SEISMIC DATA-ACQUISITION TECHNIQUES
AND RANDOM SURVEY DESIGN

by
Engin Alkan, BSc.

Thesis
Presented to the Faculty of the Graduate School of
the University of Texas at Austin in Partial
Fulfillment of the Requirements for the Degree of
Master of Science in Geological Sciences
The University of Texas at Austin
August 2007
MULTI-DIMENSIONAL LAND SEISMIC DATA-ACQUISITION TECHNIQUES
AND RANDOM SURVEY DESIGN

APPROVED BY
SUPERVISING COMMITTEE
____________________________________
Bob Hardage
Chairperson of Supervisory Committee
____________________________________
Clark Wilson
____________________________________
Robert Tatham
DEDICATION

To God and my family
ACKNOWLEDGMENTS
This thesis report is part of ongoing work that many companies are undertaking to
reduce acquisition cost and risk in large land seismic acquisition programs. I would firstly
like to thank God for allowing me the privilege to be a part of the Jackson School of
Geosciences and the Exploration Geophysics Laboratory in the Bureau of Economic
Geology led by Dr. Bob Hardage.
To Dr. Bob Hardage who is really an excellent mentor and coach for giving me
the guidance to develop excellent project and making me feel a part of an active research
group. Special thanks also go out to Dr. Clark Wilson, Dr. Robert Tatham, and Paul
Murray of the Jackson School of Geosciences, and to Steve Jumper, Steve Forsdick, Tom
Thomas, Seth Conway, and all other Dawson Geophysical employees who have
contributed to the research described here.
Dr. Bob Hardage, my supervisor and mentor, ensured that my project was on
schedule and also ensured that I was on the right path to complete the project. Other
special thanks go to The National Oil & Natural Gas Company of Turkey whose financial
support made thesis work possible.

v
MULTI-DIMENSIONAL LAND SEISMIC DATA-ACQUISITION TECHNIQUES
AND RANDOM SURVEY DESIGN

by Engin Alkan, MS. Geo. Sci.
The University of Texas at Austin, 2007
SUPERVISOR: Bob Hardage

This study analyzes different techniques and innovations of three-dimensional
seismic data acquisition and survey design. Multi-dimensional (both 2-D and 3-D) survey
design requires objective consideration of survey goals, the range of expected Earth
responses, crew and equipment accessibility, acquisition costs, instrument capabilities,
experimental field conditions, and logistic considerations.
Planning a 3-D survey combines operational and technical issues which, in turn,
depend on acquisition and design parameters. Because seismic source effort, crew and
equipment availability, and size and shape of the survey affect survey cost, it is necessary
to understand how all of these factors individually affect the overall data-acquisition
program. The main goals of this thesis are to analyze the effect of receiving station
coordinate randomness on different 3-D seismic data-acquisition and survey design
characteristics, both operationally and technically, and to ultimately optimize the cost and
data quality of seismic surveys.
Many advances have been made in imaging subsurface structures at both shallow
and deep target locations through improved seismic data-acquisition and processing
techniques in the past two decades. Service companies and oil companies continue to
vi
develop new techniques to create better 3-D images with higher resolution and improved
signal-to-noise ratio.
A major problem that confronts onshore seismic exploration companies is the
effects of the acquisition geometry on recorded data. Receiver and source line spacings,
range of offsets, and azimuths, fold variations, and source-generated noise are all
important issues to consider, as are culture, topography, and surface conditions.
This thesis consists of two parts: (1) station randomness effects on acquisition and
survey parameters, and (2) experimental evaluation of Vibroseis sweep parameters. To
perform the latter analysis, field data acquired across Tohonadla field at Bluff, Utah were
processed, and data generated with various Vibroseis sweep parameters were compared.
These analyses allowed data-acquisition and survey design parameters to be related to the
cost of the survey and to data quality.

vii
Table of Contents
List of Figures .........................................................................................................i
Chapter 1: 3D Seismic Data Acquisition and Survey Design Considerations ........1
1.1. Introduction and Background..................................................................1
1.2. Why 3-D surveys.....................................................................................2
1.3. 3-D Seismic Survey Design and Special Considerations .......................2
1.3.1. Field Operations and Survey Considerations .............................3
1.3.1.1. Multi-channel Measurements ..........................................7
The Common Midpoint (CMP) Method ...................................9
Swath Shooting Method ............................................................9
1.3.1.2. Survey Considerations ..................................................10
(a) Seismic Resolution ..........................................................10
(b) Signal-to-Noise Ratio .....................................................12
(c) Sampling Rate .................................................................18
Sampling in the time domain ..........................................18
Spatial Sampling .............................................................19
(d) Migration Aperture ..........................................................22
1.4. Summary ................................................................................................26

Chapter 2: Survey Design Parameters and Randomization ..................................27
2.1. Introduction ............................................................................................27
2.2. 3-D Seismic Data Acquisition and Survey Design Parameters..............27
2.3. Summary ................................................................................................42

Chapter 3: Randomness and Its Effects on Survey Design...................................43
3.1. Introduction ...........................................................................................43
3.2. Acquisition Geometry Effects on Seismic Records ..............................43
3.3. Random Models.....................................................................................48
3.3.1. Random Models Based on Orthogonal Geometry ....................48
3.3.1.1. Randomization Analysis for Template-Shooting ................53
3.3.1.2. Randomization Analysis for Full-Survey Shooting .............73
3.3.2. Randomness Analysis for Converted Waves ............................86
viii
3.3.2.1. Randomness Analysis for Template Shooting ....................86
3.3.2.2. Randomness Analysis For Full-Survey Shooting .............103
3.4. Error Analysis of Randomization Survey ...........................................114
3.5. Summary..............................................................................................114

Chapter 4: Tohonadla Noise Analysis – Source Effort Test ..............................116
4.1. Major Statistics of Oil Fields in Utah .................................................117
4.2. Geologic Setting of the Osage County Study Area ............................117
4.3. Source Effort Testing ..........................................................................121
Quality Control ................................................................................124
4.4. Summary..............................................................................................140

Chapter 5: Conclusions........................................................................................141

References ...........................................................................................................144
Vita ....................................................................................................................147

ix
List of Figures
Figure 1.1– The model of 3D survey design and seismic data acquisition used in this
analysis ...............................................................................................4
Figure 1.2 – The algorithm used to design sweep parameters and acquisition
parameters...........................................................................................5
Figure 1.3 – The algorithm of 3D survey design and geometrical parameters .......6
Figure 1.4 – Data sorting techniques and CMP method ........................................ 8
Figure 1.5 – A swath geometry and its internal shot station configuration ......... 10
Figure 1.6 – Horizontal resolution of seismic data based on aperture...................12
Figure 1.7 – Single reflector model for single shot and receiver array..................13
Figure 1.8 – Effect of number of phones on signal wavelength (top), the effect of
distance between phones on signal wavelength (bottom)................ 15
Figure 1.9 – Array response and attenuation ....................................................... 16
Figure 1.10 – Target spectrum of attenuation for receiver array...........................17
Figure 1.11 – Sampling theorem and anti-alias filter............................................19
Figure 1.12 – Ray propagation model and sampling interval relationship........... 20
Figure 1.13 – Relation between receiver-station interval, geologic dip, velocity, and
frequency for straight ray paths and curved ray paths..................... 22
Figure 1.14 – Relationship between recoverable dip angles with increasing depth and
aperture limit for straight lines..........................................................24
Figure 1.15 - Geologic dip, frequency, and migration aperture relationship for curved
ray path..............................................................................................25
Figure 2.1 – 3D orthogonal seismic data acquisition survey design sample........ 31
Figure 2.2 – 3D acquisition and survey design terms........................................... 31
Figure 2.3 – Fold calculation analysis and fold distribution diagram....................32
Figure 2.4 – Comparison of two 3-D recording swaths and patch shooting geometries
...........................................................................................................33
Figure 2.5 – Comparison of stacking folds created by patch-A and patch-B....... 34
Figure 2.6 – 2D and 3D teepees for different amounts of fold distribution.......... 36
Figure 2.7 – A spread sheet used to design a 3-D survey......................................37
Figure 2.8 – Minimum and maximum offsets.......................................................38
x