Advanced seismic imaging for geothermal development
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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.

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Advanced Seismic Imaging for Geothermal Development

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Advanced seismic imaging for geothermal development

Advanced Seismic Imagingfor 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

“Integrative” versus “Differential”Geophysical Methods

Grav, Mag, MT, Refraction integrate over volumes

Seismic Reflection & Radar image point changes


Problem applying seismic exploration for geothermal projects

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.


Solution solve the velocity problem

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.


Advanced seismic technology

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


Advanced processing techniques

Advanced ProcessingTechniques

  • 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


Advantages of pre stack kirchhoff migration

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


Seisopt analysis of seismic data for geothermal projects

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


Geothermal project case studies

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


Advanced seismic imaging for geothermal development

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


Advanced seismic imaging for geothermal development

Optimized Velocity Model


Advanced seismic imaging for geothermal development

  • 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.


Velocity tomography depth migration

Velocity Tomography  Depth Migration


Gravity and seismic data dixie valley nv

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


Velocity tomography depth migration1

Velocity Tomography + Depth Migration


Velocity tomography depth migration2

Velocity Tomography + Depth Migration

Okaya & Thompson, 1985


Dixie valley conclusions

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.

  • 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.


Dixie valley the low angle fault is why there is no resource to the south

Dixie ValleyThe low-angle fault is why there is no resource to the south!

NBMG Map 151


Advanced seismic imaging for geothermal development

Southern Dixie ValleyThe low-angle fault may not tap deep enough into the crust to channel geothermal fluids.


Geothermal project case studies1

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


Advanced seismic imaging for geothermal development

Coso Geothermal Field: Exploration and Resource Development

Generalized geologic map showing the study area. Modified from Duffield and Bacon, 1979.


Advanced seismic imaging for geothermal development

Reservoir boundaries

Optimized Velocity Model


Advanced seismic imaging for geothermal development

  • Coso 2.5D Volumetric Model

  • Interpolate between velocities along individual 2D lines

  • Reveals 3D geometry of features observed along 2D lines


Advanced seismic imaging for geothermal development

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

3000 foot slice

2500 foot slice

4000 foot slice

3500 foot slice

Coso 2.5D Volumetric Model


Advanced seismic imaging for geothermal development

East

West

East

West

Coso: Prestack Kirchhoff Migration


Coso conclusions

Coso Conclusions

The 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.


Conclusions of early projects

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.


Geothermal project case studies2

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


Pumpernickel valley nevada

Pumpernickel Valley, Nevada


Pumpernickel valley raw record

Pumpernickel Valley Raw Record


Pumpernickel valley velocity line 3

Pumpernickel Valley Velocity Line 3


Pumpernickel valley prestack migrated line 3

Pumpernickel Valley Prestack Migrated Line 3


Pumpernickel valley preliminary line 3

Pumpernickel Valley Preliminary Line 3


Pumpernickel valley velocity line 4

Pumpernickel Valley Velocity Line 4


Pumpernickel valley prestack migrated line 4

Pumpernickel Valley Prestack Migrated Line 4


Pumpernickel valley preliminary line 4

Pumpernickel Valley Preliminary Line 4


Pumpernickel valley velocity line 5

Pumpernickel Valley Velocity Line 5


Pumpernickel valley prestack migrated line 5

Pumpernickel Valley Prestack Migrated Line 5


Pumpernickel valley preliminary line 5

Pumpernickel Valley Preliminary Line 5


Pumpernickel valley preliminary interpretation of seismic data

3

4

5

Pumpernickel Valley - Preliminary interpretation of seismic data

Only the range-front fault is manifested at the surface


Pumpernickel valley nevada preliminary fault traces based on seismic only

Pumpernickel Valley, NevadaPreliminary fault traces based on seismic only


Pumpernickel conclusions

Pumpernickel Conclusions

The 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


Geothermal project case studies3

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

Astor Pass: 2-D WAZ Acquisition


Astor pass fault discovery with direct fault plane images

Astor Pass: Fault Discoverywith Direct Fault-Plane Images


Astor pass imaging volcanic stratigraphy

Astor Pass: Imaging Volcanic Stratigraphy


Now that we have direct fault images we can analyze

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


Astor pass conclusions

Astor Pass Conclusions

The 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


Nevada is looking for an asst professor of geological engineering

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!


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