Four basic types of field data are provided in the Significant Oil and Gas Fields of the United States Database: (1) general information, (2) discovery well, (3) production, reserves, and wells, and (4) oil-in-place and gas-in-place. Each is listed in detail as follows:
General Field Information
There are three types of general field information variables: field identification, field location, and field information.
The field identification variables are:
- Unique field identification code
- Field name and composition
- EIA and state field codes (for cross-referencing)
The field location variables are:
- State, district or area, and county or pseudo-county
- Latitude and longitude of field centerpoint
- Water depth (offshore only)
- Geologic province (AAPG-CSD) and subprovince (where appropriate)
- PGC region and province
The field information variables are:
- Year of discovery and discovery method(s)
- Year of first production
- General and specific trap types
- Number of reservoirs and number of major reservoirs/suites
- Maximum proved field acreage
- Field type (oil, gas, or combination)
- Database status (full significant or small field)
The two auxiliary tables in the database supplement this information. The Auxiliary Field Composition Table provides the remainder of complex or lengthy field composition descriptions and their associated EIA and State Field codes. The Auxiliary Counties Table provides the additional county codes for fields located in more than one county.
The field discovery well information in the database identifies the field discovery well and indicates who drilled it, where and when it was drilled, and what the results of this drilling were. The field discovery well variables are:
- Unique field identification code, field name, and state/district code
- API well code
- Lease name and well number
- Original operator name and code
- Location (lease, block or section, township, and range)
- Elevation and water depth
- Spud, rig release, and completion dates
- Total depth and formation at total depth
- Productive formation(s) and interval(s)
- Initial potential(s)
Information on productive formation, producing interval, and initial potentials are provided for as many as three different formations, beginning with the shallowest.
Field Production, Reserves, and Wells
The database provides three types of field production, reserves, and well information. Variables for field production and reserves by product include:
- Unique field identification code, field name, and state/district code
- Annual production of crude oil, natural gas (dry), and natural gas liquids, 1970 to the present
- Cumulative production from inception of crude oil, natural gas, (dry), and natural gas liquids, 1969 to the present
- Proved reserves and known (ultimate) recovery of crude oil, natural gas (dry), and natural gas liquids, 1982 to the present
The field and reservoir production and reserve data for natural gas and natural gas liquids in the database follow the same definitional standards as published national reserve data. Gas production data are expressed as marketable gas, adjusted to exclude reinjected gas, extraction loss, and non-hydrocarbon gases. Natural gas liquids include both lease condensate and plant liquids. These standards are used to provide both the best possible estimates of total field and reservoir sizes and an accurate correspondence between the sums of field and reservoir reserve and production data in the database and the published national and regional reserve and production data.
The reserve estimates provided in the database are calculated by Nehring Associates' staff. Each field and reservoir is reviewed annually for new wells, new recovery projects, workovers, and recompletions and the effects of these on production. Reserve estimates are made predominantly using decline curves. Although we only provide production data in the database on an annual basis, we review average per well monthly declines in all problematic cases for our reserve estimates.
For each geopolitical area in the database (i.e., states and districts), we also compare the sum of our field reserve estimates by product to the area reserve estimates published annually by the Energy Information Administration (EIA). Whenever significant discrepancies exist between our area sums and the EIA estimates, we work to minimize and hopefully eliminate them. For the hundred largest oil and gas fields (which contain 60-70% of all U.S. reserves), we infer field reserves from EIA's published lists of these fields.
The production and reserves information by product are combined into a total recovery table which indicates field size in barrels of oil equivalent (BOE) with the following variables:
- Unique field identification code, field name, and state/district code
- Cumulative production from inception, proved reserves, and known (ultimate) recovery expressed in liquid and liquid equivalents (BOE), 1982 to the present
- Field size classification (expanded AAPG and geometric), 1982 to the present
- Field producing status (producing, shut-in, abandoned or gas storage)
Gas is converted to oil equivalent at a rate of 6000 cf/bbl to obtain all the estimates of BOE production, reserves, and known recovery.
To facilitate economic evaluation, recent year-end well counts are also provided, using the following variables:
- Unique field identification code, field name, and state/district code
- Number of wells (active, producing, service, and shut-in) at year end, 1982 to the present
Field Original Oil-in-Place and Gas-in-Place
The database provides information on both original oil-in-place and original gas-in-place.
The field original oil-in-place variables are:
- Unique field identification code, field name, and state/district code
- Field original oil-in-place (OOIP)
- Source, year, and quality of OOIP estimate
- Current oil recovery factor
The field original gas-in-place variables are:
- Unique field identification code, field name, and state/district code
- Field original gas-in-place (OGIP)
- Source and year of OGIP estimate
- Current gas recovery and shrinkage factors
The gas-in-place data are available only for the Gulf of Mexico OCS.
The four basic types of field data are combined with the New Fields table into the field master table (FMASTER). This table is designed to facilitate a broad variety of field data retrievals.