Readme file - core and well-log porosity data

U.S. GEOLOGICAL SURVEY DIGITAL DATA SERIES DDS-33


        3-D Reservoir Characterization of the House Creek 
        Oil Field, Powder River Basin, Wyoming, V1.00

FORMATS AND EXPLANATIONS FOR SSXTOPS.DAT, SSXPOROS.DAT, COREPOR.DAT AND FLDOUTLN.PLY FILES

The following data files were used to generate statistics and 2-D and 3-D images. Display quality of the below data file samples varies based on the Web browser and other factors. Files are located in the data_set folder. Sources of data are listed in the Technical information on data sources section (techinfo.htm):

Ssxtops.dat contains borehole location/elevation/well symbol/well name/depth to the Upper Cretaceous Ardmore bentonite, and depths to top and base of the underlying Sussex "B" sandstone and the separate sand ridges that comprise it

Ssxporos.dat contains borehole X-Y location, core and well-log porosity data, core permeability, and sample depths relative to the surface, the base of the Sussex "B" sandstone, and the base of the Ardmore bentonite.

Corepor.dat lists core porosity, permeability, water, and oil saturation data for Sussex and Shannon Member sandstones by borehole name and township-range-section location

fldoutln.ply (fields outline polygons) contains the x and y coordinates of the outlines of the House Creek and Porcupine oil fields. Coordinate system is the same as above data files. The two polygons used as clipping polygons for the 3-D models and for display on the 2-D maps. File format is space-delimited point data; X (1:8), Y(9:20)

Ssxtops.dat has formation-tops data by borehole. Format is space-delimited ASCII. Headings are not present in files; heading descriptions and column locations follow the below well listings. Three or more spaces separate each data element. Blanks are marked with an * . Each of the 525 boreholes has a listed township, range, and section (data is sorted relative to this location), and estimated distance in meters from the map origin; central meridian is 106 degrees east and latitude is 44 degrees north. All 2-D and 3-D map images are generated from this origin. Our well-log analysis was augmented by other sources of information; these include Kerr-McGee Corp., Woods Petroleum Corp., Meridian Oil, Petroleum Information Corp., and State of Wyoming Oil and Gas Conservation Commission.

This file was used to delineate sand-ridge and reservoir-grade-sandstone boundaries for isopach maps and 3-D images. Reservoir-grade sandstones are defined as greater than 8.5 percent porosity, in combination with greater than 8 millidarcies (mD) permeability, geophysical well-log signatures, core and thin-section data, and borehole production data. A 10 MV spontaneous potential (SP) well-log deflection bounds gross sandstone intervals. This zone is characterized by a rapid decrease in core and well-log porosity. The boundary occurs at approximately 8.5 percent porosity, although this varies.

Listing of two wells from and format of the ssxtops.dat file

API X Y TRS ELEV YR TD ARDEP SSXTP SSXBD SSXUT SSXUB SSXLT SSXLB SYMB NAME

(1) 4900525013 43840 -30380 N43W7201 5003 78 7925 7752 7806 7811 * * * * 17 1-1 STUART-BRO (2) 4900524816 40990 -30390 N43W7203 4964 78 7996 7844 7891 7909 7896 7898 7904 7905 17 1- WATSON


API  (  1:10 ) American Petroleum Institute well identification number
X     ( 15:19 ) Approximate distance in meters east of the map origin
Y     ( 23:28 ) Approximate distance in meters north or south of the map origin
TRS   ( 32:39 ) Township direction (north or south) and number, range 
                 direction (west or east) and number.  Alpha format
ELEV  ( 43:46 ) Surface elevation of the borehole, in feet
YR    ( 50:51 ) Well completion year
TD    ( 55:59 ) Total drill depth from the surface, in feet
ARDEP  ( 63:66) Depth (in ft) from the surface to the Ardmore bentonite
SSXTP  ( 70:73) Depth (in ft) from the surface to the disconformity between
                  the Sussex "B" sandstone and the overlying Cody Shale.
SSXBD  ( 77:80) Depth (in ft) from the surface to the basal disconformity 
                  between the Sussex "B" sandstone and the Cody Shale.
SSXUT  ( 84:87) Depth (in ft) from the surface to the top of the upper reservoir sandstones.
SSXUB  ( 91:94) Depth (in ft) from the surface to the base of the Sussex "B" 
                   upper reservoir sandstones.
SSXLT  ( 98:101) Depth (in ft) from the surface to the top of the Sussex "B"
                   lower reservoir sandstones.
SSXLB  (105:108) Depth (in ft) from the surface to the base of the Sussex "B"
                   lower reservoir sandstones.
SYMB  (112:113) Well symbols of dry and non-productive (17), injection (15),
                   gas wells (20), oil (22), and oil and gas (29) wells
NAME  (113:132) Well name - in mixed alpha and numeric characters

Ssxporos.dat contains core and well-log porosity, and core-permeability data by borehole for the Sussex "B" sandstone and bounding Cody Shale intervals. Format is space-delimited ASCII. Three or more spaces separate each data element. Heading descriptions and column locations follow the below data list. Blanks are marked with an *. Data are sorted relative to API number, which is also the primary link between data files. Within each borehole, data are sorted by sample depth.

This file contains the raw data used to generate 3-D porosity and permeability images. Core porosity and permeability values are listed for 13 wells within and proximal to the House Creek field. Well-log porosity data are derived from bulk-density and sonic-log traces for about 100 boreholes. Porosity was calibrated to a specific grain density of 2.68 g/cm³; this approximates average grain densities determined from the core analyses and estimated from thin-section examinations.

Listing of data for and format of the ssxporos.dat file

           API             X            Y      SBASDP   SARDEP  SAMPDP    POR     PERM

    4900522703    31287    -24851      -1      -70      8212     5.65     *
    4900522703    31287    -24851      -1      -72      8214     5.71     *
    4900522717    31325    -24044      13      -52      8164     10.7    1.5
    4900522717    31325    -24044      12      -53      8165     7.8      0.75
    4900522717    31325    -24044      11      -54      8166     8.9      22.8
    4900522717    31325    -24044      10      -55      8167     9.9      0.62
    4900522717    31325    -24044        9      -56      8168     6.7      2.4
    4900522717    31325    -24044        8      -57      8169     7.1      0.97
    4900522717    31325    -24044        7      -58      8170     14.9    3.9
    4900522717    31325    -24044        6      -59      8171     15.2    48.2


API   ( 1:10)  American Petroleum Institute well identification number
X     (14:18)  Approximate distance in meters east of the map origin
Y     (22:27)  Approximate distance in meters north or south of the map origin
SBASDP (31:33)  Distance (in ft) of sample above the basal disconformity of
                            the Sussex "B" sandstone
SARDEP (37:41)  Distance (in ft) of sample below the base of the Ardmore bentonite
SAMPDP (45:48)  Depth (in ft) of the sample below ground surface
POR    (52:55)  Core or well-log porosity (in percent)
PERM   (59:62)  Core permeability (mD) for about 13 wells.  An * indicates no data

The Corepor.dat file contains core porosity (volume %) and permeability (mD) measurement data (POR and PERM) of Sussex and Shannon Sandstone Members of the Cody Shale; data are listed by sample depth (DEPTH) in feet below ground surface, and borehole location. This file of data for 37 boreholes is included for archival purposes. Format is tab-delimited ASCII. The below heading is present at the top of this list but not on the archived file. API number and X-Y location are not included, however this information is located in the ssxtops.dat file and can be accessed by linking the township-range-section (TRS) values for both files.

WELL WELL_LOC DEPTH PERM POR OIL WATER WELL_NAME NUMBER TRS (FEET) (MD) (%) (%) (%) AND LOCATION

12 N44W7323 8240 .09 5.40 * * NO. 1-23 FEDERAL 12 N44W7323 8241 1.6 10.0 * * FED2373 12 N44W7323 8242 7.2 16.0 * * SEC. 23, T. 44 N, R. 73 W 12 N44W7323 8243 19. 16.0 * * 12 N44W7323 8244 8.2 14.0 * * 12 N44W7323 8245 9.3 14.0 * * 12 N44W7323 8246 2.7 14.0 * * 12 N44W7323 8247 1.9 16.0 * * 13 N44W7309 8189 .23 6.4 0.0 65.7 NO.1 GOVERNMENT MILES 13 N44W7309 8190 .72 7.9 8.9 66.0 GOVT44 13 N44W7309 8191 22.7 15.0 17.8 26.8 SW NE SEC. 9, T. 44 N, R. 73 W 13 N44W7309 8192 38.6 12.0 12.3 30.3 13 N44W7309 8193 35.8 17.0 13.9 27.8 13 N44W7309 8194 73.5 15.0 17.6 30.5

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