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1、Copyright 1998-2007 Optim Inc. and University of Nevada,John N. Louie University of Nevada, Reno Satish Pullammanappallil Bill Honjas Optim Inc. www.seismo.unr.edu/louie ,Geophysical Exploration for Geothermal Resources:Advanced Seismic Technology,Problem: Applying Seismic Exploration for Geothermal
2、 Projects,“Cornerstone” of oil 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 struc
3、tures beneath the Coso and Steamboat 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 rela
4、tionship to faults and fractures controlling the reservoir permeability and production,Copyright 1998-2007 Optim Inc. and University of Nevada,Advanced ProcessingTechniques Used,Nonlinear velocity optimization Simulated annealing method to produce high resolution velocity models from first arrivals
5、picked off raw shot gathers Pre-stack Kirchhoff depth migration Directly images subsurface structures oriented in any direction,Copyright 1998-2007 Optim Inc. and University of Nevada,Copyright 1998-2007 Optim Inc. and University of Nevada,Advantages ofPre-stack Kirchhoff Migration,Minimal pre-proce
6、ssing 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, comm
7、on 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 1998-2007 Optim Inc. and University of
8、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
9、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 1998-2007 Optim Inc. and University of Nevada,Geothermal Project Case Studies
10、,Dixie Valley, Churchill County, Nevada Production and Resource Management Coso geothermal field, Inyo County, California Exploration and Resource Management Steamboat Hills geothermal field, Washoe County, Nevada Exploration and Resource Management Pumpernickel Valley, Nevada Exploration,Copyright
11、1998-2007 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 1998-2007 Optim Inc. and Unive
12、rsity of Nevada,Optimized Velocity Model,Copyright 1998-2007 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 analysi
13、s also revealed less dramatic basinward structure in area of Line 10.,Copyright 1998-2007 Optim Inc. and University of Nevada,Velocity Tomography Depth Migration,Copyright 1998-2007 Optim Inc. and University of Nevada,Gravity and Seismic Data, Dixie Valley, NV.,Map showing surface projection of stru
14、cture 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 o
15、f Dr. Dave Blackwell, SMU,Copyright 1998-2007 Optim Inc. and University of Nevada,Velocity Tomography + Depth Migration,Copyright 1998-2007 Optim Inc. and University of Nevada,Velocity Tomography + Depth Migration,Okaya & Thompson, 1985,Copyright 1998-2007 Optim Inc. and University of Nevada,Dixie V
16、alley 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 con
