advanced seismic imaging for geothermal development
DESCRIPTION
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. “Integrative” versus “Differential” Geophysical Methods. - PowerPoint PPT PresentationTRANSCRIPT
Copyright © 1998-2011 Optim Inc. and University of Nevada
John N. LouieUniversity of Nevada, Reno
Satish PullammanappallilBill HonjasOptim Inc.
www.seismo.unr.edu/~louie
optimsoftware.com
Advanced Seismic Imagingfor Geothermal Development
“Integrative” versus “Differential”Geophysical Methods
Grav, Mag, MT, Refraction integrate over volumes
Seismic Reflection & Radar image point changes
Copyright © 1998-2011 Optim Inc. and University of Nevada
Copyright © 1998-2011 Optim Inc. and University of Nevada
Problem: Applying Seismic Exploration for Geothermal Projects
“Cornerstone” of oil & gas exploration and development… …But until recently, not used for geothermal projects
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 Proven effectiveness of advanced processing techniques
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 Constrain down-dip geometry of reservoir structures
Characterize features that are significant for evaluating subsurface permeability
Correlate down-dip geometry of features mapped on the surface Image tectonic structures
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
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 ofPre-stack Kirchhoff Migration
Minimal pre-processing No need for numerous pre-processing steps common to
conventional seismic data processing Savings on man hours
Directly images structures in depth 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
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
Seismic exploration is necessary for increasing the feasibility of geothermal projects
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 Dixie Valley, Churchill County, Nevada
Production and Resource Management – Integrative
Coso geothermal field, Inyo County, California Exploration and Resource Management – Integrative
Pumpernickel Valley, Nevada Exploration – Differential
Astor Pass, Pyramid Lake, Nevada 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
Okaya & Thompson, 1985
Copyright © 1998-2011 Optim Inc. and University of Nevada
Dixie Valley ConclusionsA previously unknown basin-ward half graben
located by seismic data correlates with production and injection wells within the Dixie
Valley geothermal field.
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
NBMG Map 151
Dixie Valley
The low-angle fault is why there is no resource to the south!
Copyright © 1998-2011 Optim Inc. and University of Nevada
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
Production and Resource Management – Integrative
Coso geothermal field, Inyo County, California Exploration and Resource Management – Integrative
Pumpernickel Valley, Nevada 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 2500 foot slice 3000 foot slice
3500 foot slice 4000 foot slice
Copyright © 1998-2011 Optim Inc. and University of Nevada
Coso: Prestack Kirchhoff Migration
West WestEast East
Copyright © 1998-2011 Optim Inc. and University of Nevada
Coso ConclusionsThe seismic survey identified discrete thermal reservoir
areas within the Coso geothermal field.
Defined boundaries of two distinct reservoirs within a volcanic pile
Imaged brittle-ductile transition Predicted orientation and location of fracture
system 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 Seismic exploration can be used to reduce risk and increase
productivity in all phases of geothermal development Exploration Production Resource management
Seismic exploration is economic and feasible 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
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
Production and Resource Management – Integrative
Coso geothermal field, Inyo County, California Exploration and Resource Management – Integrative
Pumpernickel Valley, Nevada 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
Pumpernickel Valley -
Preliminary interpretation of
seismic data
5
4
3
Only the range-front 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 ConclusionsThe seismic survey imaged hidden basin-ward step
faults directly as seismic reflectors.
Network of 2-D lines explored prospect at a fraction of the cost of 3-D
Acquisition specially designed for best SeisOpt® velocity results
Good velocity info allowed imaging faults and alluvial stratigraphy
NGP is proceeding with drilling soon
Copyright © 1998-2011 Optim Inc. and University of Nevada
Geothermal Project Case Studies Dixie Valley, Churchill County, Nevada
Production and Resource Management – Integrative
Coso geothermal field, Inyo County, California Exploration and Resource Management – Integrative
Pumpernickel Valley, Nevada Exploration – Differential
Astor Pass, Pyramid Lake, Nevada Exploration – Differential
Astor Pass: 2-D WAZ Acquisition Upper 2 km 10-25 m V.R. Up to 240
channels
Lines 2-7 km long Source-receiver
spacing 17-67 m
Copyright © 1998-2011 Optim Inc. and University of Nevada
Copyright © 1998-2011 Optim Inc. and University of Nevada
Astor Pass: Fault
Discoverywith
Direct Fault-Plane
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 inversion- separate Dr, Dl, Dm
Copyright © 1998-2011 Optim Inc. and University of Nevada
Astor Pass ConclusionsThe seismic survey discovered new fault sets.
Fault-plane image quality depends on survey orientation- 3-D imaging in process
Excellent imaging of Tertiary volcanic stratigraphy- domes versus flows
Faults and stratigraphy verified from new wells
Fault imaging allows seismic attribute, AVO analysis of geothermal reservoir
Copyright © 1998-2011 Optim Inc. and University of Nevada
Nevada Is Looking for anAsst. Professor of Geological Engineering 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:
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 !