Shellenbaum, D.P. Gregersen, L.J. Delaney, P.R. 2010 vector digital data Report of Investigations RI 2010-2 Fairbanks, Alaska Alaska Division of Geological & Geophysical Surveys 1 sheet, scale 1:500,000 http://www.dggs.alaska.gov/pubs/id/21961 Alaska Division of Oil and Gas personnel collected and interpreted various data sources related to the interpretation of the Base Tertiary unconformity surface in the Cook Inlet Basin, Alaska.Data sources included public literature, public well data information (from the AOGCC-Alaska Oil and Gas Conservation Commission), a palynology database (Greater Cook Inlet Stratigraphic Palynology Control Database and Stud,Zippi, P.A., 2006) and over 2000 miles of 2D marine seismic data (CI-88 and CI-89 licensed from, and complements of, CGGVeritas.) Interpreted formation tops of the Base Tertiary unconformity are tabulated on the map. The purpose of the map is to provide an interpretation of the Cook Inlet basin Base Tertiary depth structure to the public. While most oil and gas exploration companies active in the Cook Inlet Basin have proprietary databases of seismic and well data with which they have created proprietary depth surface maps, a detailed map incorporating a significant amount of seismic data has not been available in the public domain, and to new companies who may be interested in exploring in the basin.This map incorporates seismic data over most of the marine portion overlying the basin.Additionally, this map will be used in a subsequent map of the Mesozoic subcrop surfaces, where Cretaceous and Jurassic subcrops will be displayed on the Base Tertiary depth surface. This dataset includes three shapefiles and an CSV spreadsheet.The files are organized into four entities as described in this metadata file under the "Entity_and_Attribute_Information" section. The files are as follows: >control-points Well locations and interpreted depth to top Mesozoic unconformity in oil and gas wells. This table is provided as Table 1 on the printed map and in the csv file "control-points.csv" >contours Lines of equal elevation (shapefile) >faults Polyline representing the location of a displacement of rocks along a planar surface (shapefile) >folds Polyline indicating the location of an anticlinal or synclinal fold axis (shapefile) 2010 publication date Complete None planned -155.00 -149.00 62.00 59.00 ISO 19115 Topic Category geoscientificInformation Alaska Division of Geological & Geophysical Surveys Structure Map Depth Interpretation Basins Subsurface Structure Alaska Division of Geological & Geophysical Surveys Cook Inlet Cook Inlet Basin Kenai Quadrangle Seldovia Quadrangle Tyonek Quadrangle Alaska Division of Geological & Geophysical Surveys Mesozoic This report, map, and/or dataset are available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below). Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. User specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. Contours outside of the CI88 and CI89 two-dimensional seismic coverage are dashed to indicate uncertainty. Contours outside seismic coverage with little well control have even higher uncertainties, and are designated with question marks.The absolute depth error at any given point on the map is difficult to quantify and results from uncertainties in a) the depth pick in wells, b) interpolation between and extrapolation away from wells, c) time picks on seismic, d)variations in the seismic velocity field, and e) gridding, contouring, and smoothing artifacts, particularly in areas of sparse seismic and well control. There is also a certain amount of spatial uncertainty regarding the intersection of the top Mesozoic unconformity horizon with the Bruin Bay and Castle Mountain - Lake Clark fault systems that bound the basin to the west. The fault traces (Magoon and others, 1976) indicate surface expression, whereas the Base Tertiary surface lies at varying depths. The unconformity depth surface has been contoured as if the faults are single vertical entities, but the reality is certain to be more structurally complex.The magnitude of this spatial uncertainty depends on the dips and complexity of the faults as well as the depth of the Base Tertiary surface.The deeper the surface and the shallower the actual fault dips, the larger the potential error. This report has received two technical reviews by scientists familiar with the subject matter as well as technical editing. The digitized lines representing faults, folds, and contours in this dataset were checked visually for duplication using ESRI ArcMap software. The map was constructed primarily from marine seismic reflection data and oil and gas wells that penetrated the top Mesozoic unconformity.Where the well control is too dense to differentiate at the 1:500,000 scale, an inset map is provided. Previous mapping and well penetrations were used to interpret the top Mesozoic unconformity depth surface where seismic was not available.The data set displays contours as well as fault and fold traces.This dataset does not include locations of oil and gas wells or seismic lines used to interpret the top Mesozoic unconformity. Horizontal positional accuracy of entities outside of the two-dimensional seismic coverage area and where there is little well control is difficult to quantify.Error at any given point results from uncertainties in a) the depth pick in wells, b) interpolation between and extrapolation away from wells, c) time picks on seismic, d)variations in the seismic velocity field, and e) gridding, contouring, and smoothing artifacts, particularly in areas of sparse seismic and well control. The location accuracy of interpreted depths displayed by the depth contours and presented in the "contours file" is discussed in Horizontal Positional Accuracy Report. The depth to the top Mesozoic unconformity for each well is presented in table 1 (Depth to top Mesozoic unconformity in oil and gas wells) and was interpreted using borehole geophysical log character, lithologic logs, and palynology data. The accuracy of our interpreted depths varies according the quality and density of the available data. Additional detail regarding the accuracy of our interpretations at each specific hole is not available. Zippi, P.A. 2006 database unpublished proprietary report, 187 p. www.biostratigraphy.com online 2006 publication date Zippi, 2006 stratigraphic palynology control Alaska Oil & Gas Conservation Commission (AOGCC) 2010 database Annual Report and public well databases 2010 http://doa.alaska.gov/ogc online 2010 publication date AOGCC, 2010 well data Alaska Division of Oil & Gas 2010 document Anchorage, Alaska Alaska Division of Oil & Gas http://www.dog.dnr.state.ak.us/oil/products/publications/publications.htm online 2010 publication date AKDOG, 2010 structure contour data Canadian Stratigraphic Services Lithologic Logs 2010 spreadsheet choose "log index" for details www.canstrat.com online 2010 publication date Canstrat, 2010 well logs Magoon, L.B Adkison, W.L Egbert, R.M. 1976 map USGS Miscellaneous Investigation Map I-1019 3 sheets, scale 1:250,000 250000 paper 1976 publication date Magoon and others, 1976 geology Wilson, F.H. Hults, C.P. Schmoll, H.R. Haeussler, P.J. Schmidt, J.M. Yahle, L.A. Labay, K.A. 2009 map USGS Open File Report OF 2009-1108 2 sheets, scale 1:250,000 250000 paper 2009 publication date Wilson and others, 2009 geologic map CGGVeritas, 2010 2010 document website under Products & Services / Data Library for details www.cggveritas.com online 2010 publication date CGGVeritas, 2010 seismic data DNR Staff Unpublished material vector digital data digital file 2010 publication date DNR, 2010 base map Well Interpretation - Public well logs were obtained from the Alaska Oil and Gas Conservation Commission (AOGCC). The depth to the top Mesozoic unconformity was interpreted using borehole geophysical log character, lithologic logs, and palynology data (Zippi, 2006). Where available, sonic and density logs were edited and combined to create synthetic seismograms used in calibrating to the seismic data. AOGCC, 2010 Zippi, 2006 2010 Seismic Interpretation - The seismic dataset used for interpretation consists of proprietary, speculative two-dimensional marine data (CI88 and CI89 prefix lines, owned and marketed by CGGVeritas and used by the Alaska Department of Natural Resources with permission from CGGVeritas). To tie the seismic data to the well data, calibrations were attempted for all synthetic seismograms of wells on or near seismic lines. Well ties to seismic were analyzed both visually and statistically. Two wells yielded synthetic seismogram to seismic ties of good quality to the top Mesozoic unconformity. Additional synthetic seismograms were useful in predicting the seismic character of the West Foreland Formation. Check shot velocity surveys were publicly available from two wells, OCS 0243 (Falcon) #1 and OCS 0086 (Guppy) #1. Depth-variant velocities were calculated from the synthetic seismogram ties and from the measured check shots to generate a depth and spatially variant velocity field. The following data and observations were integrated to generate the top Mesozoic unconformity seismic interpretation: 1) Time-to-depth relationships based on synthetic seismograms and checkshot velocity surveys 2) Top Mesozoic unconformity well picks displayed in time 3) Top West Foreland Formation seismic interpretation. This prominent seismic horizon is a short distance above, and generally conformable with, the top Mesozoic unconformity. Synthetic seismograms at this horizon generally showed a significant decrease in acoustic impedance, which should translate to a consistent strong reflector on the seismic.Interpretation of this horizon helped guide the underlying top Mesozoic unconformity pick. 4) The top Mesozoic is sometimes an angular unconformity, and seismic reflectors below it can have steeper dips, and be truncated by the unconformity surface. CGGVeritas, 2010 2010 Seismic time-to-depth conversion - Two-way time seismic picks on the top Mesozoic unconformity were gridded to form a surface.Time values were extracted at well penetrations by piercing the time surface with the well paths. The top Mesozoic unconformity depths at the well penetrations were divided by one-way time values to create ‘pseudo-velocities’, or average velocities from the horizon to the surface. An implicit assumption in this depth conversion methodology is that the structural dip varies smoothly between control points. However, wells are mostly drilled on major structural highs in Cook Inlet, resulting in additional velocity control points being needed in areas of inadequate sampling, predominantly in the deeper parts of the basin. The additional control point values were estimated from cross plots of time versus pseudo-velocity, extrapolating an interpreted time-velocity slope to the deeper times observed on the seismic. The velocities from well penetrations and added control were then gridded to form a horizon velocity surface, which was multiplied with the seismic one-way time surface to create a depth surface. The depth surface contours were hand edited to remove computer-generated artifacts, which were especially apparent on the edges of seismic control and near faults and other areas of strong structural variability. 2010 Interpretation Outside Seismic Control - The following data were used to interpret the top Mesozoic unconformity depth surface where seismic was not available: 1) Well penetrations 2) Bounding faults and fold axes 3) Contacts between Mesozoic and Tertiary geologic units from surface geologic mapping 4) Structural contour maps from AOGCC annual reports. Magoon and others, 1976 Wilson and others, 2009 2010 Digital Cartography - Contours, fold axes, and faults were initially constructed using GeoGraphix software.Due to software issues, the data was not exported directly from GeoGraphix in shapefile format.Rather, the data was saved as a .pdf document and sent to Design Presentation Associates for georeferencing and vectorization of all line work.The line work was then checked for positional accuracy and completeness and was attributed in ESRI ArcGIS.All final annotation, editing, and layout was done in CorelDraw. 2010 Base layer was extracted from State of Alaska, Department of Natural Resources, Alaska Statewide Core GIS database. DNR, 2010 2010 Well locations were extracted from the Alaska Oil and Gas Conservation Commission (AOGCC) online catalog, accessed in 2010. Each well is indexed in the AOGCC catalog by well name and and API number. Well locations are displayed in the printed map and well names and API numbers are provided in table 1. Vector Universal Transverse Mercator 5 0.999600 -153.000000 0 500000.000000 0 coordinate pair 0.000001 0.000001 meters contours Universal Transverse Mercator 5 0.999600 -153.000000 0 500000.000000 0 coordinate pair 0.000001 0.000001 meters faults Universal Transverse Mercator 5 0.999600 -153.000000 0 500000.000000 0 coordinate pair 0.000001 0.000001 meters folds North American Datum of 1983 Clarke 1866 6378137 298.25722210088 contours contours.shp Lines of equal elevation Alaska Division of Geological & Geophysical Surveys Elevation vertical depth in feet Alaska Division of Oil & Gas 0 -25000 feet contour_type differentiates contours as index or intermediate and the associated level of certainty for the purpose of symbolizing Alaska Division of Oil & Gas int_dash intermediate_dashed; refers to approximately located intermediate contour Alaska Division of Oil & Gas int intermediate contour Alaska Division of Oil & Gas index_dash approximately located index contour Alaska Division of Oil & Gas index index contour Alaska Division of Oil & Gas faults faults.shp Polyline representing the location of a displacement of rocks along a planar surface. Alaska Division of Geological & Geophysical Surveys Fault_ID defines the type of fault Alaska Division of Oil & Gas normal_seis normal fault derived from seismic interpretation Alaska Division of Oil & Gas strike_slip strike-slip fault Alaska Division of Oil & Gas strike_slip_dash approximately located strike-slip fault Alaska Division of Oil & Gas thrust thrust fault Alaska Division of Oil & Gas thrust_dash approximately located thrust fault Alaska Division of Oil & Gas thrust_seis thrust fault derived from seismic interpretation Alaska Division of Oil & Gas folds folds.shp Polyline indicating the location of an anticlinal or synclinal fold axis. Alaska Division of Geological & Geophysical Surveys Fold_ID refers to the type of fold Alaska Division of Oil & Gas acl anticline Alaska Division of Oil & Gas acl_dash approximately located anticline Alaska Division of Oil & Gas scl syncline Alaska Division of Oil & Gas scl_dash approximately located syncline Alaska Division of Oil & Gas control-points control-points.csv Depth to top Mesozoic unconformity in oil and gas wells this report Well Number provides a cross reference between the well location displayed on the printed map and the interpreted depth values provided in table 1. this report 1 101 API No. API number - AOGCC catalog index number for each well Alaska Oil and Gas Conservation Commission (AOGCC) Alaska Oil and Gas Conservation Commission (AOGCC) catalog index number Measured Depth (ft) measured distance along the path of a wellbore from the kelly bushing to the interpreted top Mesozoic unconformity. this report 670 16650 feet True Vertical Depth, Subsea (ft) vertical distance from sea level to the interpreted top Mesozoic unconformity this report -591 -16221 feet State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys mailing and physical

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