Transcript Louie-USC111006x - The Nevada Seismological Laboratory

Advanced Seismic Imaging
for Geothermal Development
John N. Louie
University of Nevada, Reno
Satish Pullammanappallil
Bill Honjas
Optim Inc.
www.seismo.unr.edu/~louie
optimsoftware.com
Copyright © 1998-2011 Optim Inc.
and University of Nevada
“Integrative” versus “Differential”
Geophysical Methods
Grav, Mag, MT, Refraction
integrate over volumes
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Seismic Reflection & Radar
image point changes
Problem: Applying Seismic Exploration for
Geothermal Projects
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“Cornerstone” of oil & gas exploration and development…
…But until recently, not used for geothermal projects
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Lateral complexity prevented accurate velocity modeling
Lack of accurate velocity models prevented focusing of reflection
data
Lack of focused reflectors equals poor seismic image
Poor seismic image results in lack of “added value” proposition
These problems deprived the geothermal industry of the basic
means for economically mapping the subsurface.
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Solution: Solve the velocity problem

Simulated Annealing Velocity Optimization
 Researched at the University of Nevada Seismological
Laboratory during the early 1990’s
 Commercially developed and released by Optim, under
the name SeisOpt® in 1998
SeisOpt iterates through hundreds of thousands of possible
velocity solutions to find the single, or “global”, solution that
best fits the seismic data, assuming no direction or
magnitude of velocity gradient.
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Advanced Seismic Technology
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Proven effectiveness of advanced processing techniques
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Build on success of a DOE-funded pilot study in Dixie Valley (Honjas et al.,
1997; Grant Number DE-FG07-97ID13465)
Optim has projects underway now at geothermal fields worldwide
Utilize new data acquisition parameters

Designed to enhance results from advanced processing techniques
• Image permeable structures at reservoir depth and image tectonic structures
beneath geothermal fields
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Constrain down-dip geometry of reservoir structures
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Characterize features that are significant for evaluating subsurface
permeability
Correlate down-dip geometry of features mapped on the surface
Image tectonic structures
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To determine their relationship to faults and fractures controlling the
reservoir permeability and production
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Advanced Processing Techniques
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Nonlinear velocity optimization
 Simulated annealing method to produce high
resolution velocity models from first arrivals
picked off raw shot gathers
 Refraction – Integrative

Pre-stack Kirchhoff depth migration
 Directly images subsurface structures oriented in
any direction

Reflection – Differential
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Advantages of
Pre-stack Kirchhoff Migration
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Minimal pre-processing
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Directly images structures in depth
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No need for numerous pre-processing steps common to
conventional seismic data processing
Savings on man hours
Uses velocity models from the optimization technique to place
reflectors in their correct location
Avoids unreliable, time to depth conversion, common in
conventional data processing
Images structures oriented in any direction
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Can handle velocity variations in any direction
Can image flat and moderate to steeply dipping structures
Ideal for imaging in areas with extensive faulting and fracturing
Copyright © 1998-2011 Optim Inc.
and University of Nevada
SeisOpt® Analysis of Seismic Data for
Geothermal Projects
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Seismic exploration is necessary for increasing
the feasibility of geothermal projects
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As an example, volumetric depth models of earth
structure have been produced encompassing an 11
square mile area, to a depth of 15,000 feet, at less
than half the cost of a single exploration drill hole
Volumetric depth model can be used to reduce risk
and increase productivity in all phases of geothermal
development
• Exploration
• Production
• Resource management
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Geothermal Project Case Studies
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Dixie Valley, Churchill County, Nevada
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Coso geothermal field, Inyo County, California
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Exploration and Resource Management – Integrative
Pumpernickel Valley, Nevada
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Production and Resource Management – Integrative
Exploration – Differential
Astor Pass, Pyramid Lake, Nevada
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Exploration – Differential
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Dixie Valley Geothermal Field:
Production and Resource Management
Map showing
location of
production and
injection wells
relative to
seismic lines.
Data along
these lines were
re-processed
using SeisOpt®
technology
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Optimized Velocity Model
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Dixie 2.5D
Model
•Further analysis of
production related
structure revealed a
basin-ward synform, or
half graben, that
directly correlated with
location of production
and injection wells.
•Velocity analysis also
revealed less dramatic
basinward structure in
area of Line 10.
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Velocity Tomography  Depth Migration
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Gravity and Seismic Data, Dixie Valley, NV.
Map showing surface
projection of structure
derived from seismic
survey (Solid lines).
Independent gravity
data are also shown as
shaded areas, with
northwest dipping
structure from gravity
data shown as hachured
areas and southeast
dipping structure by
stippled areas.
The gravity and seismic
data correlate well.
Gravity Data courtesy of Dr. Dave Blackwell, SMU
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Velocity Tomography + Depth Migration
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Velocity Tomography + Depth Migration
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Okaya & Thompson, 1985
Dixie Valley Conclusions
A previously unknown basin-ward half graben
located by seismic data correlates with
production and injection wells within the Dixie
Valley geothermal field.
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The half-graben was incorporated into the Dixie Valley
field injection and production model
Its presence was then confirmed via well tracer tests
The seismic survey settled a basic controversy on
whether production and injection within the Dixie Valley
field was related solely to the Dixie Valley fault, or
controlled by basin-ward structures
The true source of production was unknown prior to
revisiting the seismic data with advanced methods.
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Dixie Valley
The low-angle fault is why there is no
resource to the south!
Copyright © 1998-2011 Optim Inc.
and University of Nevada
NBMG
Map 151
Southern Dixie Valley
The low-angle fault may not tap deep enough into the
crust to channel geothermal fluids.
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Geothermal Project Case Studies

Dixie Valley, Churchill County, Nevada


Coso geothermal field, Inyo County, California


Exploration and Resource Management – Integrative
Pumpernickel Valley, Nevada


Production and Resource Management – Integrative
Exploration – Differential
Astor Pass, Pyramid Lake, Nevada

Exploration – Differential
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Coso Geothermal Field: Exploration and Resource Development
Generalized
geologic map
showing the study
area. Modified
from Duffield and
Bacon, 1979.
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Optimized Velocity Model
Reservoir boundaries
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Coso 2.5D
Volumetric Model
•Interpolate between
velocities along individual
2D lines
•Reveals 3D geometry of
features observed along
2D lines
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Coso 2.5D Volumetric Model
Slices through the 3D volume reveal the emergence of distinctive zones of permeability
within the geothermal field. Unlike other geophysical methods, SeisOpt reveals target depth.
2000 foot slice
3500 foot slice
Copyright © 1998-2011 Optim Inc.
and University of Nevada
2500 foot slice
3000 foot slice
4000 foot slice
Coso: Prestack Kirchhoff
Migration
West
Copyright © 1998-2011 Optim Inc.
and University of Nevada
East
West
East
Coso Conclusions
The seismic survey identified discrete thermal reservoir
areas within the Coso geothermal field.
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Defined boundaries of two distinct reservoirs
within a volcanic pile
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Imaged brittle-ductile transition
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Predicted orientation and location of fracture
system
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Imaged deep, “bright lens” reflector which is
thought to be created by high-temperature
thermal brines.
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Conclusions of Early Projects
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Seismic exploration can be used to reduce risk and increase
productivity in all phases of geothermal development
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Seismic exploration is economic and feasible
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Exploration
Production
Resource management
Significant added value
Cost effective, providing a volumetric model encompassing several square
miles, and extending to depths of exceeding 8,000 feet, for less than 1/2
the cost of a single exploration drill hole
Seismic exploration is the only geophysical method that can directly
sample the subsurface to depths exceeding 8,000 feet
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Can be used to calibrate and corroborate MT and gravity data.
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Geothermal Project Case Studies

Dixie Valley, Churchill County, Nevada

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Coso geothermal field, Inyo County, California


Exploration and Resource Management – Integrative
Pumpernickel Valley, Nevada


Production and Resource Management – Integrative
Exploration – Differential
Astor Pass, Pyramid Lake, Nevada

Exploration – Differential
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel
Valley,
Nevada
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel
Valley Raw
Record
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Valley Velocity Line 3
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Valley Prestack Migrated Line 3
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Valley Preliminary Line 3
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Valley Velocity Line 4
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Valley Prestack Migrated Line 4
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Valley Preliminary Line 4
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Valley Velocity Line 5
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Valley Prestack Migrated Line 5
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Valley Preliminary Line 5
Copyright © 1998-2011 Optim Inc.
and University of Nevada
3
Pumpernickel
Valley Preliminary
interpretation of
seismic data
4
5
Only the rangefront fault is
manifested at
the surface
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel
Valley,
Nevada
Preliminary fault
traces based on
seismic only
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Pumpernickel Conclusions
The seismic survey imaged hidden basin-ward step
faults directly as seismic reflectors.
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Network of 2-D lines explored prospect at a
fraction of the cost of 3-D
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Acquisition specially designed for best
SeisOpt® velocity results
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Good velocity info allowed imaging faults and
alluvial stratigraphy
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NGP is proceeding with drilling soon
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Geothermal Project Case Studies

Dixie Valley, Churchill County, Nevada


Coso geothermal field, Inyo County, California


Exploration and Resource Management – Integrative
Pumpernickel Valley, Nevada


Production and Resource Management – Integrative
Exploration – Differential
Astor Pass, Pyramid Lake, Nevada

Exploration – Differential
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Astor Pass: 2-D WAZ Acquisition
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Upper 2 km
 10-25 m V.R.
 Up to 240 channels
Copyright © 1998-2011 Optim Inc.
and University of Nevada

Lines 2-7 km long
 Source-receiver
spacing 17-67 m
Astor
Pass:
Fault
Discovery
with
Direct
FaultPlane
Images
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Astor Pass: Imaging Volcanic Stratigraphy
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Now that we have direct fault
images, we can analyze:
 Seismic
attributes- amplitude, phase,
frequency, edges, shadows, etc.
 AVO-
amplitude versus offset, Poisson’s
ratio
 AVA-
amplitude versus azimuth, fracture
orientation
 Seismic
Copyright © 1998-2011 Optim Inc.
and University of Nevada
inversion- separate Dr, Dl, Dm
Astor Pass Conclusions
The seismic survey discovered new fault sets.
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Fault-plane image quality depends on survey
orientation- 3-D imaging in process
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Excellent imaging of Tertiary volcanic
stratigraphy- domes versus flows
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Faults and stratigraphy verified from new
wells
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Fault imaging allows seismic attribute, AVO
analysis of geothermal reservoir
Copyright © 1998-2011 Optim Inc.
and University of Nevada
Nevada Is Looking for an
Asst. Professor of Geological Engineering
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https://www.unrsearch.com/postings/9727

The Department of Geological Sciences and Engineering seeks a full
time tenure-track assistant professor of Geological Engineering.
The chosen candidate must be committed to both undergraduate and
graduate instruction and will be expected to develop an externally
funded program of research in their specialty.
Specialty areas are open, but existing and emerging critical needs for
the State of Nevada include:
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Geothermal resource development
Hydrologic and geohydrologic resource development and conservation
Minerals and minerals industry sustainability, and
Recognition and mitigation of geological hazards.
Minimum requirements are Ph.D. completion and at least one degree
in geological engineering or a closely related engineering discipline.
Application deadline November 21, 2011 !
Copyright © 1998-2011 Optim Inc.
and University of Nevada