Subsurface Mapping Introduction. Objectives of subsurface mapping Methods Before you start.
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Transcript of Subsurface Mapping Introduction. Objectives of subsurface mapping Methods Before you start.
Subsurface Mapping
Introduction
Introduction
Objectives of subsurface mapping
Methods Before you start
Objectives
Most of the Earth’s structure and stratigraphy are hidden
Structure/stratigraphy may host features of economic or academic importance
Need to be able to map/interpret the subsurface
Objectives
Petroleum industry Explore for and develop oil and
natural gas reserves Mining
Explore for and develop minerals and other economic deposits
Groundwater Explore for and develop
groundwater
Objectives Waste disposal
Find suitable repositories for waste
Environmental remediation Geotechnical engineering
Locate and map the distribution of layers with specific properties
Academic studies Structure, stratigraphy
Etc.
Objectives
This course: focus on petroleum
Why? Methods applicable to other
fields Best datasets
Objectives
Develop the most reasonable subsurface interpretation(s) for the area being studied, even in areas where the data are sparse or absent Integration of different types of data
Interpretations used to direct future exploration & development
Methods Wireline logs Core, cuttings (“samples”) Seismic data (2-D, 3-D) Potential field data (gravity,
aeromag) Ground-penetrating radar Engineering data (fluids,
pressures, etc.) Previous reports Etc.
http://sofia.usgs.gov/publications/wri/94-4010/upperflaq.html
Geophysical logs used in groundwater studies
http://www.geoprobe.com/products/tools/geotechnical/cptpro_log.htm
Geotechnical borehole logs
Air Guns
Streamer Tail buoy
Marine seismic vessels typically tow arrays of air guns and streamers containing hydrophones a few meters below the surface of the water.
Messinian Salt – Mediterranean SeaMessinian Salt – Mediterranean Sea
Courtesy TGS-Nopec
Salt
Vibroseis Operations - AlgeriaVibroseis Operations - Algeria
Courtesy François Gauthier
•Dip panels
Waiting on 84wy314
Courtesy Anadarko
Mapping Faults Using Dip Panels in Thrust Mapping Faults Using Dip Panels in Thrust RegimesRegimes
Seismic Cube
Slicing and Dicing to Extract Geologic InformationSlicing and Dicing to Extract Geologic Information
Timeslices
Methods
Previous reports Paper copies of data (analog) Digital data: computer-based
interpretations
Methods
Caveat: Without understanding what you’re doing, you’ll get a wrong answer.
Working with computers, you’ll get a wrong answer at light speed (but it may be good-looking!).
Methods
Interpretations (maps, etc.) are working hypotheses, never “final” May need to update, revise as
new data become available Easier with digital data
Applies to ANY branch of (Earth) Science!!!
Collect Data
Interpret Data
Drill
Collect Data
Interpret Data
Drill
Collect pertinent data and reports
Build Database
Scan through data(quality, phase,
geology)
Scan through data(quality, phase,
geology)
Tie well and seismicdata (vsp, synthetics,
tops, paleo, etc.)
Tie well and seismicdata (vsp, synthetics,
tops, paleo, etc.)
Pick Horizons & Faults
Pick Horizons & Faults
Mapping&
Analysis
Mapping &Analysis
(I ntegration)
ReservoirProperty
Prediction
ReservoirProperty
Prediction
Output to Simulator
Output to Simulator
Output to SimulatorDrilling
Collect pertinent data and reports
Build Database
Collect pertinent data and reports
Build Database
Scan through data(quality, phase,
geology)
Scan through data(quality, phase,
geology)
Scan through data(quality, phase,
geology)
Scan through data(quality, phase,
geology)
Tie well and seismicdata (vsp, synthetics,
tops, paleo, etc.)
Tie well and seismicdata (vsp, synthetics,
tops, paleo, etc.)
Tie well and seismicdata (vsp, synthetics,
tops, paleo, etc.)
Tie well and seismicdata (vsp, synthetics,
tops, paleo, etc.)
Pick Horizons & Faults
Pick Horizons & Faults
Pick Horizons & Faults
Pick Horizons & Faults
Mapping&
Analysis
Mapping &Analysis
(I ntegration)
Mapping&
Analysis
Mapping &Analysis
(I ntegration)
ReservoirProperty
Prediction
ReservoirProperty
Prediction
ReservoirProperty
Prediction
ReservoirProperty
Prediction
Output to Simulator
Output to SimulatorOutput to Simulator
Output to Simulator
Output to SimulatorDrillingOutput to SimulatorDrilling
Before you start…
Need clear definition of objectives Structure? Stratigraphy?
Exploration? Development? Etc. Without knowing where you’re going,
you’re unlikely to get there…
Before you start…
Need good understanding of structural geology, stratigraphy and other related fields The more geology one knows, the more
reasonable the resulting interpretation Need good understanding of
physical basis for any geophysical methods being used
Prestack Depth Migration ExampleSubsalt – Offshore GOM
Before you start…
Use correct mapping techniques and methods Prepare reasonable subsurface maps
and cross-sections “Maps and cross-sections are the
primary vehicles used to organize, interpret and present available subsurface information”
Digital products (e.g., volumes) becoming more common
http://www.kgs.ku.edu/Workshops/IVF2000/nissan-ivf/tocnav640.html
Geocellular model:Each cube is assigned initial
properties (porosity, permeability, fluid saturation etc.)
3D display of georeferenced scanned images of collar locations, geological cross-sections, integrated with drillholes displaying assay concentrations, and magnetic and gravity modeled bodies.
www.rockware.com
Before you start…
Need to define fault behaviour in 3-D Faults may have important affects on
location, movement of fluids Show location of faults on maps, but
also map fault surfaces May need to do structural
reconstruction to validate accuracy of fault interpretations
A 2-D expression of a fault
Twiss and Moores, 1992
Faults are 3-D features
Fault visualization (Hart et al., 2001)
0m i 2 .5m i
0km 2.5kmFault visualization (Sagan and Hart, in press)
Courtesy Midland Valley
Before you start… All subsurface data need to be used
to develop a reasonable and accurate subsurface interpretation Geologic (including paleontologic),
geophysical, engineering Attention to resolution, accuracy of
each type Integration of different types of data
results in more robust interpretation
Before you start… Need to document the work done.
Lots of data likely to be collected and/or generated – document in a format that may be referenced, used, revised
People working on project may change, may want to “revisit” work many years after it is done
Electronic media (PowerPoint files, hypertext documents, etc.) good vehicles – especially when working with digital data
Really great stuff Fred, but how did you generate it?
Ummm….
Summary
Subsurface mapping of important economic & fundamental importance
Push towards digital, computer-based interpretation
Need to understand fundamentals – geology, geophysics
Integration of different types of data results in more robust interpretation