2 IntroductionObjectives of subsurface mappingMethodsBefore you start
3 Objectives Most of the Earth’s structure and stratigraphy are hidden Structure/stratigraphy may host features of economic or academic importanceNeed to be able to map/interpret the subsurface
4 Objectives Petroleum industry Mining Groundwater Explore for and develop oil and natural gas reservesMiningExplore for and develop minerals and other economic depositsGroundwaterExplore for and develop groundwater
5 Objectives Waste disposal Geotechnical engineering Academic studies Find suitable repositories for wasteEnvironmental remediationGeotechnical engineeringLocate and map the distribution of layers with specific propertiesAcademic studiesStructure, stratigraphyEtc.
6 Objectives This course: focus on petroleum Why? Methods applicable to other fieldsBest datasets
7 ObjectivesDevelop the most reasonable subsurface interpretation(s) for the area being studied, even in areas where the data are sparse or absentIntegration of different types of dataInterpretations used to direct future exploration & development
8 Methods Wireline logs Core, cuttings (“samples”) Seismic data (2-D, 3-D)Potential field data (gravity, aeromag)Ground-penetrating radarEngineering data (fluids, pressures, etc.)Previous reportsEtc.
17 Tail buoyStreamerAir GunsMarine seismic vessels typically tow arrays of air guns and streamers containing hydrophones a few meters below the surface of the water.
18 Messinian Salt – Mediterranean Sea Courtesy TGS-Nopec
19 Vibroseis Operations - Algeria Courtesy François Gauthier
20 Mapping Faults Using Dip Panels in Thrust Regimes Waiting on 84wy314* Dip panels are areas of continuous, (near) parallel dip* 'Smooth' changes in dip usually indicate axial planes* Discordant dip panels show fault locations* No data areas are usaully POORLY IMAGED steep dips, not faultsCourtesy Anadarko
21 Slicing and Dicing to Extract Geologic Information Seismic CubeTimeslices
22 Methods Previous reports Paper copies of data (analog) Digital data: computer-based interpretations
29 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…
30 Before you start…Need good understanding of structural geology, stratigraphy and other related fieldsThe more geology one knows, the more reasonable the resulting interpretationNeed good understanding of physical basis for any geophysical methods being used
34 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
38 3D display of georeferenced scanned images of collar locations, geological cross-sections, integrated with drillholes displaying assay concentrations, and magnetic and gravity modeled bodies.
39 Before you start… Need to define fault behaviour in 3-D Faults may have important affects on location, movement of fluidsShow location of faults on maps, but also map fault surfacesMay need to do structural reconstruction to validate accuracy of fault interpretations
45 Before you start…All subsurface data need to be used to develop a reasonable and accurate subsurface interpretationGeologic (including paleontologic), geophysical, engineeringAttention to resolution, accuracy of each typeIntegration of different types of data results in more robust interpretation
46 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, revisedPeople working on project may change, may want to “revisit” work many years after it is doneElectronic media (PowerPoint files, hypertext documents, etc.) good vehicles – especially when working with digital data
47 Really great stuff Fred, but how did you generate it? Ummm….Really great stuff Fred, but how did you generate it?
48 SummarySubsurface mapping of important economic & fundamental importancePush towards digital, computer-based interpretationNeed to understand fundamentals – geology, geophysicsIntegration of different types of data results in more robust interpretation