seismic ecquisition

Getting started Introduction to seismic

exploration

XiangYang Li

Getting started – Introduction to seismic

exploration

Yang Li

Introduction

Geophysical exploration

Seismic exploration

Essential processes of seismic exploration Seismic data acquisition

Seismic data processing

Seismic data interpretation

Modern seismic methods

Milestones and historical developments

Notes

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Essential processes of seismic exploration




Methods to explore the Earth’s subsurface

Geological exploration


Geochemical exploration

Drilling

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Methods to explore the Earth’s subsurface

Geological exploration


Geochemical exploration

Utilizing the differences in the rock’s physical properties to understand the subsurface structure and rock formation


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Utilizing the differences in the rock’s physical properties to understand the subsurface structure and rock formation


Geophysical methods

Gravity – Rock’s density difference

Magnetic – Rock’s magnetic property

Electric – Rock’s electrical property

Seismic – Rock’s elasticity

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Geophysical methods

Rock’s density difference

Rock’s magnetic property

Rock’s electrical property

Rock’s elasticity

(1) Originated from physics Magnetic field, electrical field, gravity, wave theory, radiation, etc…

To study the earth’s variation in physical property and physical phenomenon

Unlike geological methods, it is an indirect method to study the rock and rock formation

Can provide information on both the near surface and the deep surface

Basic characteristics of Geophysical methods

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Magnetic field, electrical field, gravity, wave theory,

To study the earth’s variation in physical property and physical

Unlike geological methods, it is an indirect method to study the rock

Can provide information on both the near surface and the deep surface


(2) There exist two transformations for the use of geophysical methods to study the subsurface geology: 1) transform the geological problem into a geophysical problem, and establish the links between the geological features and the geophysical anomalies;

2) transform the observed geophysical anomalies into geological features based on the established links, and expressed the anomalies in terms of geological maps.


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(2) There exist two transformations for the use of geophysical methods to study the subsurface geology: 1) transform the geological problem into a geophysical problem, and establish the links between the geological features and the

forward modelling

2) transform the observed geophysical anomalies into geological features based on the established links, and expressed the anomalies in terms of geological maps. inverse solution


(3) The geophysical solution or interpretation is non

1) different geological bodies may have the same physical properties

2) the combination of different size, shapes, fluid type and geometry among the geological bodies may produce the same physical phenomenon


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(3) The geophysical solution or interpretation is nonunique

1) different geological bodies may have the same physical properties

2) the combination of different size, shapes, fluid type and geometry among the geological bodies may produce the same physical


(4) Applicability of the geophysical methods

Every geophysical method has its limitations and applicability


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(4) Applicability of the geophysical methods

Every geophysical method has its limitations and applicability


Comparison of Geophysical methods Methods for oil exploration

Percentage

Seismic

Gravity

Magnetic

Electric

E & M

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Comparison of Geophysical methods Methods for oil exploration

E & M

Welllogging

Geotherm

al

Radiation

Others

S01: Introduction


Seismic exploration






Notes

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S01: Introduction






Seismic exploration

Seismic provides the main source of data about the

subsurface at, or approaching, reservoir scale

The main principle of seismics is to send a vibration

(elastic wave) down to our target, and allow this

energy to interact with that target

Some of this energy propagates back to the surface

and is recorded. Unfortunately we also record many

other interactions.

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Seismic exploration

Seismic provides the main source of data about the

subsurface at, or approaching, reservoir scale

The main principle of seismics is to send a vibration

(elastic wave) down to our target, and allow this

energy to interact with that target

Some of this energy propagates back to the surface

and is recorded. Unfortunately we also record many

Seismic exploration

We try to extract the relatively small part relating to our

target interaction. This is a complex task, and has

neither a unique, nor an objective solution

Data processing involves subjective interpretation

Seismic interpretation estimates geometry and

properties the Earth. Again, this has a highly

nonunique solution, and interpreters should always be

encouraged to present it as such.

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Seismic exploration

We try to extract the relatively small part relating to our

target interaction. This is a complex task, and has

neither a unique, nor an objective solution

Data processing involves subjective interpretation.

Seismic interpretation estimates geometry and

properties the Earth. Again, this has a highly

nonunique solution, and interpreters should always be

encouraged to present it as such.

Seismic reflection survey

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The basic process of seismic exploration

Excite a seismic wave

Producing a vibration on the surface

Record of seismic wave

Recording the waves reflected back from the subsurface

Reconstruct the process of the wave propagation

From the recorded waves, reconstructing the process of the

wave propgation, including its reflection point and ray pathes,

and the geological information can then infered from the

reconstructed images

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The basic process of seismic exploration

Producing a vibration on the surface

Recording the waves reflected back from the subsurface

Reconstruct the process of the wave propagation

From the recorded waves, reconstructing the process of the

wave propgation, including its reflection point and ray pathes,

and the geological information can then infered from the

Basic principles

Ways to infer subsurface geological structure

1. using head waves, or refracted waves

2. using reflected waves

Early seismic exploration is based on refracted waves

（1919—1921）

From the 1930’s, reflected waves started to use for oil exploration. Modern seismic exploration are

primarily based on the reflected waves

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Ways to infer subsurface geological structure

1. using head waves, or refracted waves；

Early seismic exploration is based on refracted waves

s, reflected waves started to use for

oil exploration. Modern seismic exploration are

primarily based on the reflected waves

Basic principle

Source geophone spread , 18

spread and terminal. http://www.globalgeophysical.com/about_ggs.html

Basic principle –

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Marine

Common midpoint

The number of times the same point on a reflector is sampled as the fold of coverage.

For example: 12 different shot geophone locations

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Common midpoint

The number of times the same point on a reflector is sampled as the fold of coverage.

For example: 12 different shot geophone locations

Basic principles Waves excited on the surface propagate downwards and reflect

back to the surface

Sand

Shale

Limestone

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Waves excited on the surface propagate downwards and reflect

Surface

Interface 1

Interface 2

An example

Example of the reflection seismic section. The x yaxis denotes the twoway running time of the seismic waves. If the seismic propagation velocity is known, the running time can be converted into depth values.

http://www.bgr.bund.de/cln_101/nn_335676/EN/Themen/GG__Geophysik/Mari ne__Geophysik/Seismik/Bilder/seism__verfahren__2__reflexionsseism__sektio n__p__en,templateId=neuesFenster.html 22

Example of the reflection seismic section. The xaxis denotes the horizontal distance, the way running time of the seismic waves. If the seismic propagation

velocity is known, the running time can be converted into depth values. http://www.bgr.bund.de/cln_101/nn_335676/EN/Themen/GG__Geophysik/Mari ne__Geophysik/Seismik/Bilder/seism__verfahren__2__reflexionsseism__sektio n__p__en,templateId=neuesFenster.html

An example

Uninterpretated section

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Interpreted sections

Water sand

Gas sand

S01: Introduction


Seismic exploration






Notes

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S01: Introduction






Essential processes

Seismic data acquisition Seismic data processing Seismic data interpretation

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Essential processes


Essential processes 1 st stage：seismic data acquisition field work logistics: survey layout, source, recording equipment

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Essential processes seismic data acquisition

field work logistics: survey layout, source,

Seismic Data acquisition

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Data acquisition

Seismic data acquisition systems

The fundamental purpose of seismic surveys is to accurately record ground motion caused by known sources in a known location. The record of ground motion with time constitutes a seismogram. The essential instrumental requirements are to 1. generate a seismic pulse with a suitable source 2. detect the seismic waves in the ground with a suitable

transducer. 3. record and display seismic wave forms on a suitable

seismograph.

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Seismic data acquisition systems

The fundamental purpose of seismic surveys is to accurately record ground motion caused by known sources in a known location. The record of ground motion with time constitutes a

The essential instrumental requirements are to generate a seismic pulse with a suitable source detect the seismic waves in the ground with a suitable

record and display seismic wave forms on a suitable

Detectors Vibrator truck

Seismic field work

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Vibrator truck Recording truck

Seismic field work

Offshore reflection seismic data acquisition using airguns and streamer

http://www.bgr.bund.de/cln_101/nn_335676/EN/Themen/GG__Geophysik/Marine__G eophysik/Seismik/Erfassung/erfassung__inhalt__en.html 30

Offshore reflection seismic data acquisition using airguns and streamer

Source: BGR http://www.bgr.bund.de/cln_101/nn_335676/EN/Themen/GG__Geophysik/Marine__G eophysik/Seismik/Erfassung/erfassung__inhalt__en.html

Essential processes


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Essential processes 2 nd stage ：indoor data processing

based wave propagation theory, using computer to reconstruct the process of wave propagation from the recorded data。

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Essential processes indoor data processing

based wave propagation theory, using computer to construct the process of wave propagation from


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Processing Flows

Demultiplexing Trace header generation < data Spherical divergence correction Noise attenuation Deconvolution before stack Band pass filter Trace normalization Static correction

Processing Flows

Trace header generation <…observers’

Spherical divergence correction

Deconvolution before stack

Processing flows (contd)

Velocity Analysis Normal Move Out Correction Trace mute AVO analysis CMP Stack Residual statics estimation & application Dip Move Out Correction Velocity analysis


Normal Move Out Correction

Residual statics estimation & application Dip Move Out Correction


DMO stack Signal enhancement Decon after stack Time Variant Filter Migration Data display


Processing Flows

Demultiplexing Trace header generation < data Spherical divergence correction Noise attenuation Deconvolution before stack Band pass filter Trace normalization Static correction

Processing Flows

Trace header generation <…observers’

Spherical divergence correction

Deconvolution before stack

SEISMIC DATA PROCESSING

Software from various contractors

SEISMIC DATA PROCESSING

Software from various contractors

Essential processes


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Essential processes 3 rd stage: Seismic data interpretation

based on the established linkes between wave anomalies and geological features, interpret the reconstruct wavefields in terms of subsurface structures and rock formation properties

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Essential processes stage: Seismic data interpretation

based on the established linkes between wave anomalies and geological features, interpret the reconstruct wavefields in terms of subsurface structures and rock formation properties

Interpretation of seismic data

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As for interpretation, from the processed seismic data the geological structure and the development of the earth's crust are deduced. On the basis of the seismic reflection horizons a geological layer model is developed. The results of other marine geoscientific exploration methods are also considered.

Seismic reflection profile and interpretation from the Mentawai forearc basin

http://www.bgr.bund.de/cln_101/nn_335676/EN/Themen/GG__Geophysik/Marine__Geophysik/Seis mik/Bilder/interpretation1__p__en,templateId=neuesFenster.html


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As for interpretation, from the processed seismic data the geological structure and the development of the earth's crust are deduced. On the basis of the seismic reflection horizons a geological layer model is developed. The results of other marine geoscientific exploration

Seismic reflection profile and interpretation from the Mentawai forearc basin

http://www.bgr.bund.de/cln_101/nn_335676/EN/Themen/GG__Geophysik/Marine__Geophysik/Seis mik/Bilder/interpretation1__p__en,templateId=neuesFenster.html


Structural interpretation

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Structural interpretation

S01: Introduction


Seismic exploration






Notes

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S01: Introduction







3D seismic exploration Vertical Seismic profiles Crosswell seismic Multicomponent seismic 4D seismic Other methods

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3D seismic exploration Vertical Seismic profiles

well seismic Multicomponent seismic

3D Layout

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One Day of Operation

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One Day of Operation

3D Layout in marine operations

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3D Layout in marine operations

Differences between 2D and 3D seismic

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Differences between 2D and 3D seismic

Comparison of 2D with 3D

2D results

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Comparison of 2D with 3D

3D results



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VSP

ZeroOffset VSP

Checkshot survey

Offset VSP

Walkaway VSP

3D VSP

Reverse VSP

Geophone

WESTERN ATLAS

Wireline

BA99212x

Geophone

WESTERN ATLAS

Source Recording

ZeroOffset VSP

Geophones WESTERN

ATLAS

Source Wireline

spacing 50 ft. spacing 50 ft.

BA99212y 54

WESTERN ATLAS

Source Recording

Checkshot survey

Geophones WESTERN

ATLAS

Source Wireline

spacing 500 ft. spacing 500 ft.

Zero offset

BA99212z 55

Checkshot survey

WESTERN ATLAS

Source Recording

Offset VSP

Geophone

WESTERN ATLAS

Wireline

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WESTERN ATLAS

Source Recording

offset

Crosswell & Single well geometries

BA99212ff

Crosswell & Single well geometries

Frac monitoring

Minifrac monitoring Hydraulic fracturing monitoring

Fluid flow

Seismic receiver

Packer BA99212ii 58

frac monitoring single well Hydraulic fracturing monitoring multi well

Fluid flow

Mini Mini frac frac survey survey

Crosswell seismic survey geometry

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Crosswell seismic survey geometry

Wave modes

present in a shot gather 60 present in a shot gather

Crosswell reflection section

(with 3D surface seismic traces superimposed)

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Crosswell reflection section

D surface seismic traces superimposed)



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Multicomponent seismic

http://www.crewes.org/ResearchLinks/ConvertedWaves/page2.php 63


http://www.crewes.org/ResearchLinks/ConvertedWaves/page2.php

Detectors (Geophones)

Three component geophones

http://www.crewes.org/ResearchLinks/ConvertedWaves/page2.php 64

Detectors (Geophones)

Three component geophones

http://www.crewes.org/ResearchLinks/ConvertedWaves/page2.php

Outline of marine multicomponent acquisition

http://www.westerngeco.com/content/services/marine/multicomponent/index.asp? 65

Outline of marine multicomponent acquisition

http://www.westerngeco.com/content/services/marine/multicomponent/index.asp?

Multicomponent records

Xcomponent

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Ycomponent Zcomponent


Xcomponent Ycomponent

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component Zcomponent

Multicomponent VSP

Xcomponent Ycomponent

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Multicomponent VSP

component Zcomponent

Multicomponent images

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Multicomponent images



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Repeated 3D Seismic

Differencing

Time 2 Time1

4D Seismic Technology

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Analysis of 4D differences

Time 2

Residual oils

4D Seismic Technology

An example of 4D seismic from the Gulf of Mexico

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An example from the Gulf of Mexico

Left: oil (green), water (blue) and borehole logging data Right: residual oil (green) and gas (red)

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An example from the Gulf of Mexico

and gas (red) distribution interpreted from

(red) distribution interpreted from 4D seismic

Seismicwhiledrilling (SWD)

Drill bit

Recording Rig sensor

Onshore & offshore TOMEX surveys : reverse VSP processing

crosscorrelation

BA99212ee

drilling (SWD)

Recording

Receivers

TOMEX surveys : reverse VSP processing correlation

Spatial Computation of Microseismic Events

FRACMAP Model

Treatment Well

Display Courtesy

ESG Canada Ltd. and

Acoustic Mapping Consultants

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Spatial Computation of Microseismic Events

ESG Analysis Observation

Well

Treatment Well

S01: Introduction


Seismic exploration






Notes

77

S01: Introduction






Milestones

Seismic recording has gone through three stages:

1、Photorecords –recording the surface vibration using photo graphic equipment, and processed completely by a human brain

2、Analogue tape recording—tape recording the subsurface vibration, similar to voice tape recording, and processed by analogue computers

3、Digital recording – digitally recording the subsurface vibration and processed by a mainframe digital computers

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Seismic recording has gone through three

recording the surface vibration using photo graphic equipment, and processed completely by a human brain

tape recording the subsurface vibration, similar to voice tape recording, and processed by

digitally recording the subsurface vibration frame digital computers

Started in the 1960’s…

Three key technologies

1) field digital recording systems

2) Vibroseis – controlled sources

3) multiple coverage and stacking

The digital revolution…

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Started in the 1960’s…

Three key technologies：

1) field digital recording systems

controlled sources，

3) multiple coverage and stacking

The digital revolution…

The 1980’s… Rapid development of processing and interpretation technologies in the 1980’s:

1．Seismic attributes analysis （1）Amplitude attributes (e.g. AVO

（2）Velocityrelated attributes

（3）Instantaneous attributes

2．Borehole seismic technology （1）Vertical seismic profile (VSP

（2）crosswell seismic

3．3D seismic

4．Multicomponent seismic

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Rapid development of processing and interpretation technologies in the 1980’s: Seismic attributes analysis Amplitude attributes (e.g. AVO）；

related attributes

Instantaneous attributes

Borehole seismic technology Vertical seismic profile (VSP）


3D seismic

A leap forward from 2D to 3D

Started in the 1980’s

More accurate seismic imaging

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A leap forward from 2D to 3D

Started in the 1980’s

More accurate seismic imaging

The 1990’s

1. High resolution seismic 2. 4D seismic – time lapse seismic 3. Seismic 3D depth imaging

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1. High resolution seismic time lapse seismic

3. Seismic 3D depth imaging

The 21st century…

1．Integration

Geophysical integration: Seismic, logging, gravity, magnetic…

Exploration and production integration: geophysics with petroleum engineering

2. The era of reservoir geophysics…

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The 21st century…

Geophysical integration: Seismic, logging,

Exploration and production integration: geophysics with petroleum engineering

2. The era of reservoir geophysics…

Introduction


Seismic exploration






Notes

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Notes

1. Exploration methods 2. Geophysical exploration 3. Essential processes of seismic

exploration 4. Milestone； 5. Major breakthroughs

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Exploration methods； Geophysical exploration； Essential processes of seismic

Major breakthroughs

seismic ecquisition

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