Download - Module 01 Introduction
Introduction
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Fundamentals of Seismic Acquisition and Processing
Overall Learning Objectives
1. Understand seismic fundamentals as they affect the interpretation of seismic data.
2. Understand the concepts involved in imaging geologic structures and properties through seismic data acquisition and processing.
3. Comprehend the parameters that can seriously affect seismic data quality and costs.
4. Determine if seismic data has been recorded and processed in a technically correct manner for subsurface objectives.
5. Apply quality assurance steps in acquisition and processing.
6. Communicate effectively with seismic specialists.
Introduction
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Jeff Johnson
3 years Schlumberger NExT Director of Training: Geoscience/Petrophysics - Tulsa
22 years Experience with Amoco/BP Applied Seismic Technology – New Orleans Manager, Geophysical Technology, Amoco International General Manager, Geoscience Research and Technology –
Tulsa/Houston
Academics Stanford Geophysics Degrees Boston College Prof. Geophysics University of Oklahoma Adjunct Research Associate
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Fundamentals of Seismic Acquisition and Processing
Course Overview
• Seismic Wave Propagation and Reflection Principles• Signal Analysis Methods• Acquisition
– Principles– Design– Operations– Quality Control
• Data Processing– Objectives – Signal Corrections– Velocity– Statics– Imaging– Quality Assurance
• Acquisition/Processing for:– Attributes, Inversion, and AVO– Multicomponent
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Learning Methodologies
• Modular • Why modules are important• Powerpoints, short problems, “workshops”,
flip chart• Interactive
– Discussion questions– Share experiences/problems– Learn from each other
• Ask Questions• Daily feedback
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Texas A&M UniversityPetroleum Engineering Center of
Excellence
The University of OklahomaWell Engineering, Geoscience /
Petrophysics Centers of Excellence.
• Commercial Joint-Venture: E&P Training• 150 Short Courses/Programs• University and SLB Instructors• Computer-Based Training• Global Presence• Global Presence
Heriot-Watt University Distance Learning in Petroleum Engineering Center of Excellence
NExTNetwork of Excellence in Training
www.nexttraining.ie
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Module 1
Introduction
Learning objectives
Awareness Level:• Various geophysical methods• Seismic trace, record, section, cube• History of seismic method• Seismic reflection basics• Role of seismic in reservoir life cycle
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Geophysical Surveying MethodsMost geophysical surveying methods can be used either on land or offshore. Each of these methods measures a parameter that relates to a physical property of the subsurface. List of different methods, the parameters they measure, and the related rock properties are indicated in the table 1
Table 1 Geophysical Surveying Methods
METHOD MEASURED PARAMETERPHYSICAL PROPERTY MEASURED OR
DERIVED
SEISMIC TRAVEL TIME AND AMPLITUDE OR REFLECTED/REFRACTED SEISMIC WAVES
ELASTIC MODULI, PROPAGATION VELOCITY, DENSITY?
GRAVITY SPATIAL VARIATIONS IN THE STRENGTH OF THE EARTH’S GRAVITATIONAL FIELD
DENSITY
MAGNETIC SPATIAL VARIATIONS IN THE STRENGTH OF THE GEOMAGNETIC FIELD
MAGNETIC SUSCEPTIBILITY
ELECTRICAL RESISTIVITY
EARTH RESISTANCE ELECTRICAL CONDUCTIVITY
INDUCED POLARIZATION
FREQUENCY-DEPENDENT GROUND RESISTANCE
ELECTRICAL CAPACITANCE
SELF-POTENTIAL ELECTRICAL POTENTIAL ELECTRICAL CONDUCTIVITY
ELECTRO-MAGNETIC
RESPONSE TO ELECTROMAGNETIC RADIATION
ELECTRICAL CONDUCTIVITY AND INDUCTANCE
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Types of Seismic Applications
• 2D land• 3D land• 2D marine• 3D marine• Long offset• Transition zone• Borehole• Multicomponent land• Ocean bottom multicomponent• Time lapse/4D
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Seismic Interpretation
• Objective of seismic acquisition and processing is the accurate interpretation of seismic data
– Travel times– Amplitudes– Attributes– Tied to subsurface control
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Seismic Interpretation
3D Seismic Cube3D Seismic Cube
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S R
• Structure• Lithology• Pore fluid• Fractures• Pressure
What Do We Desire?
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Predict and Characterize Subsurface Reservoirs
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Seismic Interpretation
• Basic Seismic Data Concerns– Travel time distortions– Amplitude fidelity– Noise and artifacts– Resolution– Spatial positioning– Cost
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Today’s Major Problems
• Backscattered noise• Complex near-surface• Multiples• Anisotropy• Parameters for model driven processing
– Velocity– Q– Anisotropy
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SS RR
Measure:Measure:• Travel timeTravel time• AmplitudeAmplitude• Particle motionParticle motion
Infer:Infer:• VelocityVelocity
The Seismic Experiment
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Basic Seismic Measurements
ParticleVelocity
ParticleDisplacementPressure
Tim
e
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The Seismic TraceThe basic unit of seismic data
Amplitude0 +-
Tra
vel T
ime
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Recording Seismic Data
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Typical Scales of Reservoir Investigation
Simulation 100 - 500 feet
Seismic 10’s – 100’s of feet
Logs Inches - feet
Lab Fractions of inch
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Scales of Geological Reservoir Heterogeneity
Fie
ld W
ide
Inte
rwel
lW
ell-B
ore
(modified from Weber, 1986)
Hand Lens orBinocular Microscope
Unaided Eye
Petrographic orScanning Electron
Microscope
DeterminedFrom Well Logs,Seismic Lines,
StatisticalModeling,
etc.
10-100'smm
10-100'smm
1-10'sm
100'sm
10'sm
1-10 km
100's m
Well WellInterwell
Area
ReservoirSandstone
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Subsurface Reservoirs• Can seismic predict some key characteristics and properties?
- Depth
- Geologic Setting - Origin of Rocks/Fluids
- Geologic Structure
- Geometry – thickness, areal extent, volume, seals
- Rock Type
- Heterogeneity – Layering, Faults/Fractures, Compartments
- Porosity
- Fluid Content/Distribution
- Pressure Distribution
- Mechanical Strength
- Permeability
- Drive Mechanisms
- Temperature
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Earth Propertiesas seen by seismic waves
• Inhomogeneous• Attenuative• Anisotropic• Porous• Fluid filled
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Characteristics of Seismic Data
• Band Limited– Low End 5-10 Hz– High End 50-100 Hz
• Spatial Coverage Redundant yet Incomplete• Large Data Volumes (up to 10’s of terabytes)
– 2000-4000 time samples per trace– Record length 6-12 sec– 100,000 - 1,000,000 spatial locations– 12-1000 fold redundancy
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Exploration Seismic
• Most seismic reflection techniques uses only compressional waves– Easier to acquire– Resolution, data quality generally better– More sensitive to fluid properties
• Use of shear and converted wave data is increasing– May give a good image where compressional data
cannot– Sensitive to porosity; insensitive to pore fluid– Combined with compressional data, tells more
about rock and fluid properties -- Poisson’s Ratio
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Seismic Trace, Record and Section
• A seismic trace, or "wiggle trace" is the response of a seismic detector to the earth's movement due to seismic energy.
– Direct arrival– Refraction– Reflection– Noise
• Excursions of the trace from the central line appear as peaks and troughs; the peaks represent "positive" signal voltages, and the troughs represent "negative" signal voltages.
• A seismic record, or common‑shot record, is a side‑by‑side display of all the wiggle traces that were recorded simultaneously from a number of detectors for a single shot point. The "peaks" are toward the right side of the display and are filled in with black to make patterns more visible.
• Zero time is at the top of the record, with time increasing downward . This display is a raw image of the subsurface over a limited area, and it contains noise and other signal distortions.
Seismic Trace and Record
Distance
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Stacking A CMP (Common Midpoint) Gather
S1S2S3S4S5 R1 R2 R3 R4 R5
Collect all data with the same source-receiver midpoint
C M P
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Some Terms
CMP - Common MidpointCDP - Common Depth PointCRP - Common Reflection Point
• These terms are sometimes used interchangeably (and erroneously).
• Individual traces are summed (stacked) to form a single trace trace at each CMP surface location
• Much in seismic acquisition and processing is based on assumptions of horizontal beds and homogeneous media.
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• Moving the “spread” (source plus receivers) one-half spread length between shots produced continuous subsurface coverage
Seismic Reflection Exploration Overview
Shot 1 Shot 2 Shot 3
First Receiver
Last Receiver
First Receiver
Last Receiver
First Receiver
Last Receiver
Surface
Subsurface Reflector
Subsurface Coverage
Continuous or Single-Fold Subsurface Coverage
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• Later, a method called multi-fold or common mid-point (CMP) shooting was developed
• In this method, the spread is moved less than one-half spread length resulting in more over-lap in coverage
• Moving 1/4 spread length means that the same reflections are recorded by two different shots at two different receivers at two different shot-to-receiver distances but the midpoint between shots and receivers is the same! This is called 2-fold shooting
• Increasing the overlap, increases the fold– Move-up of 1/6 spread gives 3-fold– Move-up of 1/8 spread gives 4-fold– Move-up of 1/12 spread gives 6-fold, etc
Seismic Reflection Exploration Overview
S1 S2 M R2 R1 Surface
Reflector
S1 = 1st Source S2 = 2nd Source M = Midpoint R1 = 1st Receiver
R2 = 2nd Receiver
CMP Shooting.
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Seismic Reflection Exploration OverviewMulti-fold Coverage
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Stacked Trace AfterGeometry Correction
CMP0
Tw
o-W
ay T
rave
l Tim
e
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Seismic Trace, Record and Section
• A seismic survey generates a large number of shot records to cover the area under study. Many steps of processing are applied to the data to enhance the signal, to minimize noise, and to increase resolution. All the traces corresponding to a surface midpoint are combined into a single trace, called a common‑mid‑point stack.
• Seismic section
When processing is complete, all the common‑depth‑point stacks are displayed side by side to make a seismic section, which is the final output of a 2D seismic survey.
A Seismic Section
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3-D Seismic3-D Seismic
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3-D Prospect Layout Example
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Major Steps in Seismic Reflection Exploration
• Pre-planning
• Data Acquisition
• Data Processing
• Interpretation
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Pre-Planning
• Primary & secondary targets• Survey main objectives• Document objectives and priorities• Allocate acquisition & processing budgets• Set data quality specifications• Establish reasonable schedules and deadlinesEstablish reasonable schedules and deadlines• Locate & modify lines of survey• Specify methods & equipment types• Determine acquisition parameters
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Geologic Objective
• Trap type - structural, stratigraphic or combination
• Depth, thickness and areal extent
• Maximum dip expected
• Regional dip
• Modeling
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Acquisition Parameters
• Receiver group spacing• Receiver group arrays• Number of receiver groups• Line spacing/bin size• Number of lines/bins• Maximum and minimum source-to-receiver
distances (offsets)• Source spacing• Source type/arrays• Recording geometry
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Processing Parameters• Amplitude scaling parameters to compensate
for signal variation in time and space
• Filter frequencies to suppress noise
• Deconvolution parameters to expand signal bandwidth and shape the wavelet
• Surface wave and refraction velocities for noise suppression
• Near-surface velocities to correct for static shifts
• Velocity fields for stacking CMP data and migrating reflections to their proper position
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Reservoir Life Cycle and
Business ValueExploration Appraisal Development Maturity
-
+
Minimize Capex
Minimize Opex
Defer Abandonment
Maximize Production
Maximize Recovery
Accelerate Production
Time
Optimized Development Traditional Development
Cas
h F
low
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Seismic in the Reservoir Cycle
• Exploration –increasing 3D but sometimes still 2D
• Appraisal – 3-D
• Development – High Resolution 3D, Borehole
• Management – 4D/Time-lapse
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Discussion
Is 2-D seismic ever done today?
If so, what is its role?
How does your company perceive the value of seismic methods?
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Business Success Depends on Technology Integration Focused on the Reservoir
Geophysics
Petrophysics Geology
Engineering
Drilling Computing
Reservoir
Prediction Description
PerformanceOptimization
Characterization
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Seismic Today
Quantitative seismic images have become critical for business success in all subsurface reservoir projects.
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Critical Capabilities forSeismic Reservoir Prediction
Rock Physics
Imaging
Attributes
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A Technical Vision
• Seismic data will be routinely transformed to depth images
• Volume image processing and multi-volume picking will provide accurate reservoir / trap frameworks
• Attribute analysis, multi-component inversion, and petrophysical calibration will provide reliable estimates of 3D subsurface rock and fluid properties throughout the reservoir exploration / production cycle.
• Every geophysical prediction will be qualified by its uncertainty / risk.
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Seismic to Reservoir Transformation
Detection
Visualization
Classification
Detection
Visualization
Classification
ReservoirModels
ReservoirModels
FrequencyFrequency
CoherencyCoherency
AngleAngle
PP SS
VectorSeismic
Data
VectorSeismic
Data
MultidimensionalDepth
Images
MultidimensionalDepth
Images
MultipleAttributeVolumes
MultipleAttributeVolumes
AIGeostatisticalInterpretations
AIGeostatisticalInterpretations
Geological / Rock PhysicsConstraints
Geological / Rock PhysicsConstraints
Rock / Fluid Physics Modeling
Calibration
Rock / Fluid Physics Modeling
Calibration
SimulationIterations
SimulationIterations
RatesVolumes
Uncertainty
RatesVolumes
Uncertainty
AVOAVO
Rock / Fluid Physics Modeling
Calibration
Rock / Fluid Physics Modeling
Calibration
Amoco, RIP - 1997Idealized Multidimensional Process
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Summary
What have we learned?
• Objectives of seismic and overall role in reservoir cycle
• Basics of CMP seismic
• Steps in seismic projects
• Role of seismic in E&P business