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 
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                                               File Formats Readme

Formats and explanations for 1) ssxtops.dat, 2) ssxporos.dat, and 3) corepor.dat ASCII 
data files used to generate statistics and 2-D and 3-D images.  Files are located in the 
data_set folder.  Sources of data are listed in the Technical information on data sources 
section (techinfo.htm).


           1)  xsxtops.dat contains borehole location/elevation/well symbol/well name/depth to 
the Ardmore bentonite, and depths to top and base of the Sussex "B" sandstone and 
separate sand ridges       

          2)  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.      

          3)  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   
 
          4)  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 approximate 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
----------------------------------------------------------------------------------------------------------- 
4900525013  43840  -30380  N43W7201  5003  78   7925  7752  7806  7811    *     *      *      
*     17   1-1  STUART-BRO
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 percent) 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
NUM.      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