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Basics of seismic interpretation

What is seismic interpretation Basic principles

Basics of seismic interpretation

What is seismic interpretation

What is Seismic Interpretation?

Objectives: lRecognize hydrocarbon anomaly

lValidate anomaly’s

geologic framework

composition⇒amplitude interpretation

Jakosky, 1960

Management’s Risk Requirement Identify where art dominates and science deviates in the

structural and amplitude interpretations.

What is Seismic Interpretation?

Objectives: Recognize hydrocarbon anomaly

Validate anomaly’s

geologic framework ⇒structural interpretation

amplitude interpretation

Management’s Risk Requirement Identify where art dominates and science deviates in the

structural and amplitude interpretations.

Suggestions from the Past Anomalies with New Petrophysical Properties

Anomalies with New Petrophysical l Oil and gas emit corpuscular radiation.

l Desirable minerals radiate observable vibrations.

l Hydrocarbon rocks have a gravity force that is proportional

to 1/r rather than 1/r

l Oil and gas send out electromagnetic waves.

l Organic substances, such as oil and gas, exhibit sexual characteristics.

(Blau, Geophysics, v. 1, no. 1. pg.1 ) or (TLE, 1983, v.2, #3, p.28

Slight Problem: Though desirable by most, none of the above can be validated.

Suggestions from the Past Anomalies with New Petrophysical Properties

Petrophysical Properties Oil and gas emit corpuscular radiation.

Desirable minerals radiate observable vibrations.

Hydrocarbon rocks have a gravity force that is proportional

to 1/r rather than 1/r 2 .

Oil and gas send out electromagnetic waves.

Organic substances, such as oil and gas, exhibit sexual characteristics.

(Blau, Geophysics, v. 1, no. 1. pg.1 ) or (TLE, 1983, v.2, #3, p.2831)

Slight Problem: Though desirable by most, none of the above can be validated.

The Art and Science of Interpretation

Art... Systematic application of experience to assign the geologic framework and

composition (the earth model).

Science... Application of physical sciences to the earth model.

Risk is based on the uniqueness of the

The Art and Science of

... Systematic application of rules based on past experience to assign the geologic framework and

composition (the earth model).

Application of physical sciences to validate the earth model.

Risk is based on the uniqueness of the validation.

Components of the Hydrocarbon System

Greve, 1997

Components of the Hydrocarbon

The Art and Science of Interpretation

ACCH

Corollary: Geophysical data can’t be interpreted without knowing the answer. [Art … set of rules]

The Art and Science of

ACCH

Geophysical data can’t be interpreted without knowing the answer. [Art … set of rules]

Interpretation => interpretation

Is Time PullUp a Paleo High?

Interpretation => ACCHtime

Up a Paleo High?

Verification “Seismic reflection amplitude … can in many cases distinguish between gas related amplitude and other … anomalies …”

Interpretation => interpretation

Verification “Seismic reflection amplitude … can in many cases distinguish between gas related amplitude and other … anomalies …”

Interpretation => ACCHamplitude

After the invention of CMP method、 these new technique increased the number and variety of geological data which can be abstracted from seismic data. The application of seismic exploration is much more prosperous than ever before.

1970’s 1960’s 1950’s

The Onset of Interactive

Real time prestack and poststack processing on work station

The Onset of Interactive Interpretation

Interpretation have the ability of simple poststack precessing Interpretation (indoor)

Processing (Computer Precessing Center)

Acquisition (Field)

The era of bitch processing

The onset of digital processing era

Recording of seismic reflection is divided into three stage

The Good Old Days

Only one person (one computer) is needed to perform data acquisiton, processing and

interpretate it in the field

Traveltime Interpretation Eras

、vibrator、digital processing, the use of these new technique increased the number and variety of geological data which can be abstracted from seismic data. The application of seismic exploration is much more prosperous than ever before.

1980’s 1990’s The 21st century

The Onset of Interactive Processing

Real time prestack and poststack processing on work station

The Onset of Interactive Interpretation

Interpretation have the ability of simple poststack precessing

Processing (Computer Precessing Center)

The era of bitch processing

The onset of processing intergration

Processing and Interpretation are integrated into a same

platform

Acquisiton Intergration

Seismic crew with multitask of design, acquisition, precessing,

interpretation

Traveltime Interpretation Eras

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

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

related attributes

Borehole seismic technology Vertical seismic profile (VSP）

Multicomponent seismic

Amplitude Interpretation Eras

First Era Bright Spot (1970 1899 –Knott Theory Amplitude vs incident angle

1919 –Zoeppritz Theory Amplitude vs incident angle

1951 –Gassmann Theory Petrophysical link to seismic

1955 –Koefoed Application

1961 –Bortfeld Theory Linear approximation equation

1976 RosaApplication

Second Era AVO (1982 1982 OstranderVerification of AVO

1985 ShueyApplication Rockproperty emphasis atdifferent incident angles.

Amplitude Interpretation Eras

Bright Spot (1970 1982) Amplitude vs incident angle

Amplitude vs incident angle

Petrophysical link to seismic

Poisson’s Ratio from RC(θ)

Linear approximation equation

RC(θ) elastic inversion

AVO (1982 Present) OstranderVerification of AVO

property emphasis atdifferent incident angles.

Basic principles

• Seismic and geological interfaces • Horizon tracking and correlation • Well ties • Fault patterns and identification • 2D mapping • 3D mapping • DHIs (Direct Hydrocarbons Indicators)

Basic principles

Seismic and geological interfaces Horizon tracking and correlation

Fault patterns and identification

DHIs (Direct Hydrocarbons Indicators)

The relationship between seismic reflection interface and geological interface

a. Well 1 and well 5

The relationship between seismic reflection interface and geological interface

a. Well 1 and well 5

b. Add Well 24 to figure a 4 to figure a

c. Seismic section across well 1 c. Seismic section across well 15

Notes 1. The seismic reflection contrast not a lithological approximately corresponds unconformity;

2. The seismic interfaces geological interface, correspondence between

3. Parasequences may but do not produce reflections

reflection is from a velocity lithological contrast; it

corresponds to a geological

interfaces is often parallel to the interface, but there is no

between them. may affect the wave forms reflections.

Geological model vs. seismic imaging

Geological model vs. seismic imaging

Marmousi model. A 2D seismic model devised by the Institut Franc¸ais du Petrole to test 2D migration algorithms. There is a hydrocarbon accumulation (and flat spot) in the anticline under the decollement. (a) The model at 1:1 scale ratio (from Versteeg, 1994); (b) model with different grey density indicating different velocities: (c) CMP stack of the seismic data. (d) Time migration of the CMP stack; (e) Prestack depthmigration of 1% of the data. (From Youn and Zhou, 2001).

Basic principles


Basic principles




Horizontal tracking basics

a. Event continuity and similarities

b. Similar wave train and characteristics:

amplitude, frequency and phase.

Horizontal tracking basics

Event continuity and similarities

Similar wave train and characteristics:

amplitude, frequency and phase.

Basic principles


Basic principles




3000

2800

2600

2400

2200

2000

4 4 9 0

4 2 9 0

4 0 9 0

3 8 9 0

3 6 9 0

3 4 9 0

3 2 9 0

3 0 9 0

2 8 9 0

2 6 9 0

2 4 9 0

T0 (s)

depth (m) 99SN10

40

K

T

J2S5

J2S4

J2S3

J1S2

J3S6-7

J1S1T+H

J1S1LST

2.3.2 2.3.2 Calibration of horizon Calibration of horizon

80 120 1 10 100

GR RT u5 F

sequ ence

Syste m tract

2 5 3 5

2 7 0 0

3 1 6 0

3 3 5 7

3 4 6 6

3 70 4

3 8 9 4

4 0 5 0

m

m

m

m

m

m

m

m

J 3 S 6

J 2 S 5

J 2 S 4

J 2S 3

J 1 S 2

J 1 S 1

HST

TST

LST

LST

TST

HST

TST

LST HST

TST LST

HST TST

LST

LST

TST

HST

Layers

Calibration of horizon Calibration of horizon VSP VSP、、synthetise seismic data synthetise seismic data

Tie at the intersecting points Tie at the intersecting points

Lateral correlation Lateral correlation

Legend well 2D area 3D area Basin border well tie section 1 well tie section 2

Basic principles


Basic principles




Fault nomenclatures

.

Fault nomenclatures

Fault nomenclatures

.

Fault nomenclatures

Fault types

Fault identification

(1) Broken events and wavetrain (2) Number of events increase or decrease or disappear (unconformity)

3) Rapid changes in seismic events (4) Events branch off, merge, distort, and the phase changes (small faults)

(5) Fault plane reflection, diffracted wave

Fault identification

(1) Broken events and wavetrain (2) Number of events increase or decrease or

conformity) 3) Rapid changes in seismic events (4) Events branch off, merge, distort, and the phase

(5) Fault plane reflection, diffracted wave

(1) Broken events or wave trains (1) Broken events or wave trains (medium and small faults)

(2) Number of events increase or decrease or disappear (2) Number of events increase or decrease or disappear

(3) Rapid changes in seismic events (3) Rapid changes in seismic events

(4) Events branch off, merge, distort, and the phase changes (small faults

Model of small fault and vertical resolution

(4) Events branch off, merge, distort, and the phase changes small faults)

Model of small fault and vertical resolution

(4) Events branch off, merge, distort, and the phase changes (small faults

Events distort

(4) Events branch off, merge, distort, and the phase changes small faults)

Events distort and break

(5) Fault plane reflection and diffracted wave (5) Fault plane reflection and diffracted wave

Basic principles


Basic principles




Fence diagrams Fence diagrams composited from a grid of

seismic record sections. (Courtesy Chevron Oil Co.)

• (b) Computerdrawn isometric fence diagram of six seismic lines. (Courtesy GrantNorpac.)

• (c) Same as (b) except with data above some picked horizon removed.

• (d) Fence diagram to show spatial relationship of data from a series of eight wells. (From Brown and Fisher, 1977, 222.)

Basic principles


Basic principles




Contour maps from 3D data Contour maps from 3D data

Time slices. The area is 3.68.0 km;

• (a) through (g) time slices for t 1.580 to 1.604 s at 4 ms intervals;

• (h) timecontour map made by tracing one contour from each of the preceding time slices, starting with the outside of the central area on map (a). (Courtesy Haliburton Geosciences.)

• •

•

FIG. A16. Arbitrary line. (a) A time slice through a migrated 3D seismic volume using different colors to indicate positive and negative reflectivities and color intensity to indicate magnitude. (b) Vertical sections connecting well locations is an arbitrary line. Arbitrary lines often consist of several connected straightline segments. (Courtesy Prakla Seismos AG.)

3D data display 3D data display

3D data display 3D data display

Basic principles


Basic principles




Direct hydrocarbon indicators Direct hydrocarbon indicators

• Flat spot • Bright spot

Artifacts: Fake downward structure caused by low velocity of mud Artifacts: Fake downward structure caused by low velocity of mud