PRODUCED WATER COMPOSITIONAL DATABASE

	This version of the produced water database is a subset of a larger database originally provided to 
the USGS by GeoINFORMATION at the University of Oklahoma.  The origin of the database is traced to 
the Petroleum Laboratory at Bartlesville, Oklahoma that was originally operated by the U.S. Bureau of 
Mines and subsequently by the Department of Energy.  In the 1980s, the database was provided to the 
University of Oklahoma.  The database as received by the USGS included 77,650 records and 102 fields.  
The review process and complete description of each field within the database are presented below.

DESCRIPTION OF DATA REVIEW

	Four principal data-types were reviewed in detail:  location, geologic setting, sample type and 
major ion composition.  Review criteria were applied liberally to retain as many records as possible.  
Records that were retained include a location within a state and county (except for offshore wells), a 
reference to a geologic setting (basin or province), a sample type other than drilling, work-over or fluids 
open to external input, and contain consistent major ion chemical composition data.  The resulting database 
contains 58,706 records that satisfy the criteria described below.
Records in the database contain results from test holes as well as producing wells.  Samples from 
the test wells were retained because they generally intersect geologic units with a history or potential of 
petroleum production.  Although this database may be described to contain formation water compositions, 
the large number of samples collected from the petroleum production system removed from the wellhead is 
more consistent with a produced water designation.  A few of the records are for water collected from water 
wells.  These may have been collected to identify possible sources of water for enhanced recovery 
operations and were also retained in the database.

Location
	Parameters that identify the geographic location of the sampled well include state, county, latitude and 
longitude, and oil and gas field name.  These parameters were reviewed for consistency.  Records that were 
not consistent and could not be corrected independently were deleted from the database.  State and county 
names were corrected for consistency of spelling and location.  Latitude and longitude of the sampled well 
were retained if they were originally reported in the database or added if the coordinates could be 
calculated using the public lands survey information.  Approximately 20% of the records list field latitude 
and longitude as entered in the original database for the sample location.  Oil and gas field names were 
corrected for consistency of names, field code and location by comparing with entries in the 1998 Field 
Code Master List database that is maintained by the Energy Information Agency of the Department of 
Energy 
(http://www.eia.doe.gov/pub/oil_gas/natural_gas/data_publications/field_code_master_list/historical/1998/
html/fcml_1998.html).

Geologic Setting
	The geologic setting of the sample is described by the geologic basin (province), the name of the 
geologic unit from which the fluid was produced and the age of that geologic unit.  Entries describing the 
geologic setting used in the original database were revised to conform to the nomenclature used by the 
American Association of Petroleum Geologists (AAPG).  Geologic names and ages of the sampled units 
were compared with the USGS Lexicon of Geologic Names (hgmdb.usgs.gov/Geolex/geolex_home.html) 
and the stratigraphic charts presented in Gautier and others (1995).  Names of geologic units varied and 
included groups, formations, and members.  Where possible all three names were included.  The position of 
the sample site relative to the USGS assessment provinces, identified in Gautier and others (1995), was 
added to the database for all records with a latitude and longitude or county location.  All records for 
onshore wells list a geologic basin and 66% have a geologic unit and age.

Sample type
	Water is collected by several methods and at various points during well completion and petroleum 
production.  The method and location of sample collection can substantially affect the composition of the 
water sample because of mineral precipitation, degassing, addition of oxygen, contamination by drilling or 
workover fluids, water mixing, and evaporation.  Originally more than 5000 different descriptors were used 
to describe the method/location of sample collection.  These were consolidated into 18 general categories 
intended to indicate general sample types as described in Table 2.  In general, samples collected from a drill 
stem test or production test yield the best results for formation water analyses.  Samples collected from a 
wellhead are considered the best representation of produced water as they are likely to be water brought to 
the surface prior to treatment and separation.

Chemical composition
	Review of the database focused on the major dissolved ions and total dissolved solids (TDS) 
because these values can be checked for internal consistency using simple calculations (Hitchon and 
Brulotte, 1994).  The major dissolved species typically include: sodium, potassium, calcium, magnesium, 
chloride, bicarbonate, and sulfate.  The sum of the ions should equal the TDS for a good water analysis.  
Records that have water analyses within 15% of the TDS were considered acceptable.  The charge balance 
was also calculated as the sum of cations minus the sum of anions divided by the total ion content (all 
values in units of equivalents/liter).  Records with a charge balance within 15% were considered 
acceptable.  Application of these evaluations to this database is problematic in that sodium in most standard 
formation water analyses is determined by difference and therefore will likely result in good mass and 
charge balance.  
As described by Hitchon and Brulotte (1994), several other chemical parameters can assist in 
identifying poor analyses or contaminated samples.  All samples with pH>9 and <4 and samples with 
potassium concentrations greater than five times the sodium content were deleted.  These compositions are 
likely the result of contamination due to treatment of a well (Hitchon and Brulotte, 1995).
	Chemical compositions of the 58,706 records that were retained in the database (Fig. 1) meet the 
review criteria described above, but may not represent complete water analyses.  Water analyses of oil and 
gas production waters may include 1) incomplete analyses, 2) the sum of sodium and potasssium as sodium 
only, 3) the sum of calcium and magnesium as calcium, or 4) no report of pH.  Complete major ion 
chemical compositions (pH, Na+, Ca2+, Mg2+, K+, SO42-, Cl- and HCO3-) are given for only 7,722 records in 
the revised database.  Most records lack results of a potassium analysis.  For many preliminary 
assessments, incomplete analyses though not desirable may be suitable for many types of evaluation.  
Detailed water assessments, however, (particularly geochemical modeling), require complete analyses.



FIELD NAMES AND DESCRIPTIONS

1. UNIQID -- Unique identifier (Long Integer). Numeric identifier used as primary key for each record.  
Original entries were text format.  Format was changed to numeric.  Values are as originally entered.  (Null 
entries: 0)

2. STATECODE -- Code for the state (Text, 2).  Two character designation assigned to conform to the 
FIPS code.  Entry based on the state name in the STATE field after that field was completely reviewed.  
STATECODE was added during USGS review of the database.  (Null entries: 0)

3. STATE -- Name of state (Text, 14).  Full spelling of state name.  Entry verified to be consistent with 
latitude, longitude, county and field name for non-null entries in those fields.  Records with inconsistent 
entries among these parameters were removed from this version of the database.  Offshore wells located in 
federally managed waters are also assigned to a state to indicate approximate location.  (Null entries: 0)

4. REGDIST -- Regional district (Text, 4).  Identifies the oil and gas district within Texas.  Entries were 
verified in 2001 by consistency of REGDIST with COUNTY as defined by the Texas Railroad 
Commission (web site below).  Verification and correction was conducted manually using a database query 
to list all unique combinations of counties in Texas and their associated REGDIST.
Reference to Texas Railroad Commission designations available at: 
http://www.rrc.state.tx.us/divisions/og/information-data/ogicd.html.  (Null entries: 44,657)

5. COUNTY -- County name (Text, 50).  Name corrected for spelling using TIGER database.   Original 
records listed multiple counties for some records.  Corrections were made manually by comparing TIGER 
county listing with a table of unique county spellings for each state prepared by a query to the database.  
Discrepancies in spelling between TIGER and COUNTY were checked by manually comparing with 
county spellings listed in official state web sites.  Entries were revised to make other location parameters 
(latitude and longitude, field name, township, range and section) consistent with entry.  Consistency for 
records with LATITUDE and LONGITUDE was verified by plotting (ARCVIEW) the record locations on 
a county boundary basemap (ESRI).  Records in which field name, county or latitude and longitude 
remained inconsistent after review were deleted.  (Null entries: 0)

6. CNTYCODE -- Three digit code for the county (Text, 4).  Corrected where necessary to be consistent 
with county FIPS code according to the TIGER database.  Entries were reviewed manually using a listing 
of unique entries prepared by a database query of COUNTY and CNTYCODE entries.  (Null entries:  0)

7. GEOBASIN -- Geologic basin (Text, 50).  Basin name as originally entered in the database.  Minor 
corrections were made for consistency of spelling.  Corrections were made manually by preparing a table of 
unique GEOBASIN entries and comparing with established spellings of defined geologic basins.  (Null 
entries:  125)

8. USGSPROV -- Geologic province consistent with USGS 1995 National Oil and Gas Assessment 
assignments (Text, 50).  Valid records are limited to those entries with valid county designations.  Province 
was assigned using a GIS overlay operation (ArcInfo IDENTITY command) w/ a national province 
coverage (available at http://energy.cr.usgs.gov/oilgas/noga/).  For records lacking accurate latitude and 
longitude USGSPROV was assigned manually by comparing COUNTY designation with USGSPROV 
boundaries.  (Null entries: 514 (equal to number of federally managed offshore wells; these areas were not 
included in the definition of USGS Provinces.))
.
9. USGSREG -- Geologic region consistent with USGS 1995 National Oil and Gas Assessment 
assignments (Text, 50).  Region was assigned using a GIS overlay operation (ArcInfo IDENTITY 
command) w/ a national region coverage (available at http://energy.cr.usgs.gov/oilgas/noga/)  For records 
lacking accurate latitude and longitude, USGSREG was assigned manually by comparing USGSPROV 
designation with USGSREG boundaries.  Records for wells located in federally managed offshore wells 
were assigned as MMS wells consistent with agency jurisdiction for assessment.  (Null entries: 0)

10. FIELD -- Oil and gas field (Text, 40).  Field names in the original entries were checked against the 
1998 Field Code Master List (FCML) maintained by the Energy Information Agency of DOE.  Comparison 
of the FIELD entries with the FCML was conducted with a visual basic program written to make 
corrections to FIELD (for details see FLDFLAG).  Many of the corrections were format and spelling 
corrections that were done manually.  Deletion of unrecognized names was part of the correction.  The 
county location listed for FIELD in FCML was also checked against COUNTY in each record to verify 
consistency.  If inconsistent, the record was deleted.  Minor changes in formatting relative to the listing in 
FCML were required for some field names. Entries with apostrophes ( ') were modified to remove the 
apostrophe so that search routines and supporting visual basic programs could aid in data review.
Site of 1998 FCML 
http://www.eia.doe.gov/pub/oil_gas/natural_gas/data_publications/field_code_master_list/historical/1998/h
tml/fcml_1998.html.  (Null entries: 8,154)

11. FLDCODE -- Oil and gas field code (Text, 10).  The numeric code for the field name as corrected in 
the above field.  Numeric codes used were checked for consistency with the 1999 release of the EIA Field 
Code Master List (FCML) as described in FIELD and FLDFLAG.  (Null entries: 12,238)

12. FLDFLAG -- Field name correction flag (Number, Integer).  This field was inserted into the database 
by the USGS to record the type of correction made to the FIELD entries.  Explanation of entries: 0, oil and 
gas FIELD name and FLDCODE are absent; 1, FLDCODE matches entry of the invalid field name 
database, FIELD is null; FIELD and FLDCODE corrected according to recommendations of the invalid 
field name database (part of FCML);  2, FIELD name is presented in the invalid fields database, FIELD 
and FLDCODE corrected to be consistent with correction recommended in invalid fields database; 3, 
FIELD name not in FCML but FLDCODE matches FCML entry, changes made to correct FIELD entry to 
be consistent with FLDCODE; 4, FIELD name changed to conform to change of alias name in FCML; 5, 
FIELD and FLDCODE are both valid entries in the FCML but are inconsistent, entries manually corrected 
to be consistent with COUNTY; 6, FIELD and FLDCODE are consistent and match FCML as entered;  7, 
FIELD is wildcat; 8, FIELD entry spelling or other editorial correction made to make name consistent with 
FLDCODE;  9, correction was made to spelling or other editorial correction to make FIELD consistent with 
entries in FCML, for these records FLDCODE was null but added to correspond to FIELD; Where 
resolution was not possible FIELD and FLDCODE set equal to null.  (Null entries: 0)

13. SECTION -- Section (Text, 2).  Section number as assigned by the public lands survey grid.  Value as 
entered in the original database.  (Null entries: 18,670)

14. TOWNSHIP -- Township (Text, 5).  Township location as assigned by the public lands survey grid.  
Values are as entered in the original database.  Minor corrections to format were made manually to 
standardize the listing of direction and number.  (Null entries: 19,010)

15. RANGE -- Range (Text, 5).  Range location as assigned by the public lands survey grid.  Values are as 
entered in the original database.  Minor corrections to format were made manually to standardize the listing 
of direction and number.  (Null entries: 18,919)

16. LATITUDE -- Latitude location of the well (Number, Double).  Entries derived from original well 
locations in the database, the latitude of the oil and gas field containing the well as listed in the original 
database, or calculated from a spatial calculator that determines a centroid latitude from the section, 
township and range coordinates.  The spatial calculators were used for:  Arizona, California, Colorado, 
Idaho, Iowa, Kansas, Montana, Nebraska, New Mexico, Oklahoma, Oregon, South Dakota, Utah, and 
Wyoming.  Latitude for other states with township, range, and section information were not calculated.  
Conversions for Oklahoma were conducted using an online calculator available from Geo Information at 
the University of Oklahoma (http://www.geo.ou.edu/index.htm).  Locations for Iowa were calculated using 
a spatial calculator available from the Iowa Department of Natural Resources 
(http://samuel.igsb.uiowa.edu/gettrs ).  Locations for other states were calculated using TRS2LL a freeware 
program written in 1995 by Martin Wefald (http://www.geocities.com/jeremiahobrien/trs2ll.html; see also 
http://www.esg.montana.edu/gl/trs-data.html).  (Null entries: 4,916)

17. LONGITUDE -- Longitude location of the well (Number, Double).  Entries derived from original well 
locations in the database, the latitude of the oil and gas field containing the well as listed in the original 
database, or calculated from a spatial calculator that determines a centroid longitude from the section, 
township and range coordinates (PLS, public land survey).  The spatial calculators were used for:  Arizona, 
California, Colorado, Idaho, Iowa, Kansas, Montana, Nebraska, New Mexico, Oklahoma, Oregon, South 
Dakota, Utah, and Wyoming.  Latitude for other states with township, range, and section information were 
not calculated.  Conversions for Oklahoma were conducted using an online calculator available from Geo 
Information at the University of Oklahoma (http://www.geo.ou.edu/index.htm).  Locations for Iowa were 
calculated using a spatial calculator available from the Iowa Department of Natural Resources 
(http://samuel.igsb.uiowa.edu/gettrs).  Locations for other states were calculated using TRS2LL a freeware 
program written in 1995 by Martin Wefald (http://www.geocities.com/jeremiahobrien/trs2ll.html; see also 
http://www.esg.montana.edu/gl/trs-data.html).  (Null entries: 4,916)

18. LOCGRADE -- Location grade (Text, 2).  Values inserted into the database to record the reliability 
with which the LATITUDE and LONGITUDE of the sampled well are known.  Values of LOCGRADE 
include: B, LATITUDE and LONGITUDE given in original database; C, LATITUDE and LONGITUDE 
calculated from township, range, and section location; D, LATITUDE and LONGITUDE are for the oil and 
gas field not for the individual well; values as entered in the original the database (assumed to be the field 
centroid);  G, LATITUDE and LONGITUDE are unknown.  (Null entries: 0)

19. API -- Well number assigned according to API crteria(Text, 12).  American Petroleum Institute well 
number assigned in the original database.  Entries are unchanged from the original database.  (Null entries: 
26,478)

20. WELLNAME -- Name of the sampled well (Text, 50).  Entries are unchanged from the original 
database.  (Null entries: 3,246)

21. COMPDATE -- Completion date (Date, MM/DD/YYYY).  Date that the well was completed.  Format 
changed from text (original database) to date.  Entries in which month was absent were manually modified 
to have "01" as the month; those lacking day likewise are "01".  Otherwise entries are as presented in the 
original database.  (Null entries: 55,542)

22. SAMPFORM -- Sampled formation name (Text, 24).  Geologic unit(s) from which the sample was 
produced (screen or perforated interval).  Entries are unchanged from the original database.  (Null entries: 
4,699)

23.REVSAMPFORM -- Revised sample formation name (Text, 50).  Geologic units from which the 
samples was produced.  Corrections to SAMPFORM made to be consistent with stratigraphic columns in 
the USGS 1995 National Oil and Gas Assessment and the USGS Geologic Names Lexicon 
(http://ngmdb.usgs.gov/Geolex/geolex_home.html   Corrections were made in 2000 by manually by listing 
the unique SAMPFORM entries for each state and comparing those entries to the references listed above.  
Changes were made using an update query on the database to replace existing entries with those more 
consistent with standard stratigraphic nomenclature as defined in the above references.  Entries are 
presented in an effort to depict the hierarchy of units.  "/" identifies greater unit to the left (group, 
formation, member) while the unit on the right is contained within the unit on the left (formation, member, 
unit, bed etc.)  A"-" identifies units that are either equivalent in rank or not part of the same higher units.  
Null entries indicate an null entry in SAMPFORM or the entry in SAMPFORM could not be directly 
related to the reference listings of geologic units.  (Null entries: 17,252)

24. #FORMS -- Number of producing formations (Text, 2).   USGS entered parameter indicating the 
number of formation produced by each well (S, single; M, multiple; ? unknown).  Entries were made 
manually and are based on the entries in RevSAMPFORM.  (Null entries: 0)

25. SAMPFORMAGE -- Geologic age of the sample formation (Text, 3).  Three digit code assigned to 
correspond to the age of sample formation.  Entry as presented in the original database.  (Null entries: 
28,343)

26. REVSAMPFORMAGE -- Geologic age of the sample formation (Text, 3) revised to conform to Table 
1 (attached).  Corrections to SAMPFORM made to be consistent with stratigraphic columns in the USGS 
1995 National Oil and Gas Assessment and the USGS Geologic Names Lexicon 
(http://ngmdb.usgs.gov/Geolex/geolex_home.html.  Corrections to this field were completed in 2000.  (Null 
entries: 9,515)

27. UPPERDEPTH -- Depth of the top of the sampled interval (Number, Long integer).  Entry as originally 
entered in the database, with change of format from text to number.  (Null entries: 10,853)

28. LOWERDEPTH -- Depth of the bottom of the sampled interval (Number, Long integer).  Entry as 
originally entered in the database, with change of format from text to number.  (Null entries: 18,735)

29. METHOD -- Location/method of where the sample was collected from the sampled well (Text, 50).  
Entry as contained in the original database.  (Null entries: 17,838)

30. REVMETHOD -- Revised location/method of sample collection site (Text, 20).  USGS added field to 
simplify entries in METHOD to a simplified list of methods including:  wellhead, DST, separator, 
heater/treater, tank, bailer, swab, bomb, openhole, production, production test, formation test, bleeder, and 
unknown.  A listing of the more common METHOD entries and their assigned REVMETHOD entries are 
listed in Table 2.  (Null entries: 0)

31. MethGRADE -- USGS assigned grade assigned to the location/method of sample collection (Text, 1).  
Grades intended to reflect the relative ability of the sample to represent the composition of produced water.  
B:  well head, production; C: drill Stem, formation or production tests; D: swab, bailer; E: separator, 
heater/treater, tank,  F: unknown.  MethGRADE entries and their corresponding REVMETHOD and 
METHOD are listed in Table 2.  (Null entries: 0)

32. SAMPDATE -- Date sample was collected (Date, MM/DD/YYYY).  Date that the water sample was 
collected.  Format changed from text (original database) to date.  Entries in which month was absent are 
listed as "01"; those lacking day likewise are "01".  Otherwise entries are as presented in the original 
database.  (Null entries: 16,025)

33. pH -- pH of the water sample.  pH was converted from character to numeric format and corrections 
were made of the type of entry.  Records with pH values less than 4 and greater than 9 were excluded from 
this compilation because values outside the range are typically a product of contamination by chemicals 
used during drilling and workovers.  (Null entries: 18,441)

34. UNITS -- Concentration units mg/L or ppm.  Units are as used in the original version of the database.  
(Null entries: 0)

35. BICARB -- Concentration of bicarbonate ion in UNITS.  Converted from character to numeric format.  
Values of the entries could not be verified independently.  Recoding of some entries was according to the 
following scheme:  values of  -3 replace original character entries of "ND", "NA" or null entries; -2 replace 
original character entries of "none",  "negative", or "nil", -1 replaces original character entries of "trace" 
and "minor".  (Null entries: 0)

36. CALCIUM -- Concentration of calcium ion in UNITS.  Converted from character to numeric format.  
Values of the entries could not be verified independently.  Recoding of some entries was according to the 
following scheme:  values of  -3 replace original character entries of "ND", "NA" or null entries; -2 replace 
original character entries of "none",  "negative", or "nil", -1 replaces original character entries of "trace" 
and "minor"..  (Null entries: 0)

37. CHLORIDE -- Concentration of chloride ion in UNITS.  Converted from character to numeric format.  
Values of the entries could not be verified independently.  Recoding of some entries was according to the 
following scheme:  values of  -3 replace original character entries of "ND", "NA" or null entries; -2 replace 
original character entries of "none",  "negative", or "nil", -1 replaces original character entries of "trace" 
and "minor".  (Null entries: 0)

38. MAGNESIUM -- Concentration of magnesium ion in UNITS.  Converted from character to numeric 
format.  Values of the entries could not be verified independently.  Recoding of some entries was according 
to the following scheme:  values of  -3 replace original character entries of "ND", "NA" or null entries; -2 
replace original character entries of "none",  "negative", or "nil", -1 replaces original character entries of 
"trace" and "minor".  (Null entries: 0)

39. POTASSIUM -- Concentration of potassium ion in UNITS.  Converted from character to numeric 
format.  Values of the entries could not be verified independently.  Recoding of some entries was according 
to the following scheme:  values of  -3 replace original character entries of "ND", "NA" or null entries; -2 
replace original character entries of "none",  "negative", or "nil", -1 replaces original character entries of 
"trace" and "minor".  (Null entries: 0)

40. POT-SODIUM -- Concentration of the sum of potassium and sodium ions in UNITS.  Converted from 
character to numeric format.  Values of the entries could not be verified independently.  Recoding of some 
entries was according to the following scheme:  values of  -3 replace original character entries of "ND", 
"NA" or null entries; -2 replace original character entries of "none",  "negative", or "nil", -1 replaces 
original character entries of "trace" and "minor"  (Null entries: 0)

41. SODIUM -- Concentration of sodium ion in UNITS.  Converted from character to numeric format.  
Values of the entries could not be verified independently.  Recoding of some entries was according to the 
following scheme:  values of  -3 replace original character entries of "ND", "NA" or null entries; -2 replace 
original character entries of "none",  "negative", or "nil", -1 replaces original character entries of "trace" 
and "minor".  (Null entries: 0)

42. SULFATE -- Concentration of sulfate ion in UNITS.  Converted from character to numeric format.  
Values of the entries could not be verified independently.  Recoding of some entries was according to the 
following scheme:  values of  -3 replace original character entries of "ND", "NA" or null entries; -2 replace 
original character entries of "none",  "negative", or "nil", -1 replaces original character entries of "trace" 
and "minor".  (Null entries: 0)

43. TDS -- Concentration of total dissolved solids in UNITS.  Converted from character to numeric format.  
Values of the entries could not be verified independently but were checked for consistency with the sum of 
major ions in the MASSBAL field.  Entry of 3 indicates records in which TDS was not given and 
presumably not determined.  (Null entries: 0)

44. CHARGBAL -- Calculated value of charge balance (Number, single precision).  Calculated as: (sum of 
equivalents of cations  sum of equivalents of anions) divided by the sum of the equivalents of all ions.  
Most records have good charge and mass balance due to the determination of sodium by difference.  Values 
outside the range of 0.15 to 0.15 were deleted.  (Null entries: 0)

45. MASSBAL -- Calculated value of mass balance (Number, single precision).  Calculated as the sum of 
major ion species (sodium, potassium, potsodium (as sodium), calcium, magnesium, chloride, sulfate, and 
bicarbonate) divided by the reported total dissolved solids.  Values outside the range of  0.85 to 1.15 were 
deleted.  Values were not calculated for TDS entries of 3.  (Null entries: 39)

46. SOURCE -- Identifies the source of the record.  Typically this lists the name of the petroleum company 
or the analytical laboratory responsible for the analytical data.  These entries are unchanged from the 
original database.  (Null entries: 29,882)


References

Gautier, D.L., Dolton, G.L., Takahashi, K.I., and Varnes, K.L., 1995, National Assessment of Oil and Gas 
ResourcesResults, Methodology, and Supporting Data, U.S. Geological Survey Digital Data 
Series DDS-30 Release 2.

Hitchon, Brian and Brulotte, M., 1994, Culling criteria for "standard" formation water analyses:  Applied 
Geochemistry  v. 9, p. 637-645.

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