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This page last updated: January 11, 2000
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Field Naming
Handbook, March 1996
Introduction
This handbook was prepared as a guide and reference to the field naming process at MMS.
An oil and/or gas field in the Federal OCS of the Gulf of Mexico is defined* as an area
consisting of a single reservoir or multiple reservoirs all grouped on, or related to, the
same general geologic structural feature and/or stratigraphic trapping condition. There
may be two or more reservoirs in a field that are separated vertically by intervening
impervious strata, or laterally by local geologic barriers, or by both.
The MMS Gulf of Mexico Field Naming Committee, comprising a petroleum engineer, a
geologist, and a geophysicist, assigns field names to leases with qualifying oil and gas
discoveries. It reviews new producible lease and first production memoranda submitted by
the District Offices, as well as well logs, geophysical data, geologic maps, and other
pertinent data to establish the existence of a new field or the extension of an existing
field.
Field names are assigned for a lease or group of leases so that natural gas and oil
resources, reserves, and production can be allocated on the basis of the geologic
framework of the unique feature that contains the hydrocarbon accumulation. The Committee
strives to include all leases determined capable of producing and associated with a
specific geologic structure in a single field. In the case of a common platform serving a
large structure as well as a minor satellite structure, the Field Naming Committee may
consider it one field. Field names may be changed at the lessee's or lessor's request when
adequate geologic and/or production data would support such a change.
The new field is usually named after the area and block on which the discovery well is
located. The area encompassed by a field will be revised from time to time to include
additional leases on a geologic structure, leases that have been proven productive by new
drilling, and to split leases into separate fields to adhere to the definition of a field.
On the following pages are twelve examples of geologic structures in the Gulf of Mexico
and MMS field designations for their overlying leases.
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*"MMS Guidelines for the Application, Review, Approval, and Administration of the
Deepwater Royalty Relief Program."
Major Points on Assigning Leases to Fields
- Structural lows are used to separate fields with structural trapping mechanisms.
- Faults are rarely used to separate fields.
- The structure or stratigraphic condition with pay having the largest areal extent on a
lease determines the field expanse.
- Reservoirs that overlap areally are always combined into a single field regardless of
the fact they may be on two separate structures or stratigraphic conditions. Fields are
never separated vertically.
- Wells from the same platform can be in two separate fields.
- One well is rarely in two fields, i.e., a well with two completions, each in a separate
field.
Outline of Examples
Example No. |
Title |
1 |
Salt Dome with Fault Trap
Downdip on the Domal Structure
(Trap Not Directly in Contact With the Salt)Piercement salt dome with traps against the
salt and a fault trap down on the flank. Traps against the salt in blocks 2, 3, and 4 have
hydrocarbon discoveries. The fault trap in block 13 has a discovery. Blocks 2, 3, 4, and
13 would all be considered on the same structure and therefore in the same field.
Cross Section on Example 1. |
2 |
Two Structural Highs with a
Separating Structural Low The structural low between the two anticlinal features in
this case is sufficient to designate two separate fields.
Cross Section on Example 2. |
3 |
Series of Structural Highs Bounded by a Common Regional Growth Fault Example 3-Figure 1-Geologic Setting:
Series of structural highs bounded by a regional growth fault. The highs are separated by
distinct lows.
Example3-Figure 2-MMS Field
Designation: These three distinct structural highs would be separated into three
fields - Fields A, B, and C.
Example 3-Figure 3-Shifting Lease
Boundaries on the Above Example: In this figure the grid is shifted slightly. The
structural highs would remain separate fields, however, leases would be apportioned rather
than whole leases assigned to fields; Blocks assigned to:
Field A Blocks 2, 3, and the northern half (N/2) of 8.
Field B Southern half (S/2) of Block 8, Block 13, and the northwestern quarter (NW/4) of
Block 14.
Field C Southern half and northeastern quarter (S/2, NE/4) of Block 14, and Blocks 16 and
17. |
4 |
Unrelated Shallow and Deep Structures (Adding a Separate Deep Structure to
Example 3) Deeper rollover structure on the downthrown side of the same
regional growth fault as shown in Example 3. This structure is geologically unrelated to
the above domal high. There are two options to name the field depending on the horizontal
distance between the two structures.
Figures 1, 2, and 3- Shallow and Deep Structures Separated Horizontally: Even though
this deep structure is along and lower on the same growth fault as previously shown in
Field B (Example 3), it would be considered a separate field. The two structures are
separated horizontally and their reservoirs do not overlap in an areal view.
Figures 4, 5, and 6 Reservoirs of Deep and Shallow Structures Overlapping Horizontally:
Another example would be the deep structure shifted underneath the shallow structure. The
two structures cannot be separated horizontally because their reservoirs overlap in an
areal view.
Example 4-Figure1-Deeper
Unrelated Structure Added To Example 3. Shallow and Deep Structures Separated
Horizontally.
Example 4-Figure 2-Cross Section
on Figure 1 (Example 4) and Figure 1 (Example 3).
Example 4-Figure 3-Reservoirs of
Deep (Example 4-Figure 1) and Shallow (Example 3-Figure 1) Structures Not Overlapping
Horizontally, Therefore Divided Into Two Separate Fields.
Example 4-Figure 4-Another
Variation-Shallow and Deep Structures Not Separated Horizontally
Example 4-Figure 5-Cross Section
on Figure 4 (Example 4) and Figure 1 (Example 3).
Example 4-Figure 6-Reservoirs of
Deep and Shallow Structures Overlap Horizontally and Therefore are Considered a Single
Field |
5 |
Shallow Stratigraphic Trap
(Bright Spot) and a Deeper Unrelated Structure This is an example of a deep
structure covering a large area with a shallow stratigraphic trap above. The field name
designation of a particular lease depends on the structure the wells from that lease
penetrate. If only the shallow bright spot is reached, the field name is based on the
areal extent of that bright spot. However, if a well on the lease also reaches the deeper
larger structure, the larger structure would be the basis for the field name. A lease
could initially be named by the shallow structure and later have a deeper discovery,
therefore putting the lease on a larger, deeper structure. At that point, its name would
change to reflect its inclusion in the larger structure.
Cross Section on Example 5 (Two
Separate Fields)
Cross Section on Example 5
(Larger Structure - Basis for Field Name) |
6 |
Series of Traps Against a Large
Fault Without Separating Structural Lows A long fault with a series of traps against
the fault. There are no separating lows between the traps; therefore, they are combined
into a single field.
Cross Section on Example 6 |
7 |
Reservoirs on Both Sides of a
Large Growth Fault Normally faults dont't separate fields. No matter how large a
fault or vertical separation of reservoirs, if there is an absence of a separating
structural low, they are considered to be in the same field. In this example, the large
fault does not separate the trap on the downthrown side from the structural high on the
upthrown side. Although there is a horizon break and a large vertical separation between
the two pay horizons, they would still be considered the same field.
Cross Section on Example 7 |
8 |
Multiple Stratigraphic Traps (Bright Spots) Stratigraphic bright
spot reservoirs are generally considered individual fields. A couple of exceptions are:
(1.) If two or more bright spots overlap in an areal view, they are grouped into a single
field. (2.) If two or more bright spots are on one lease, they are usually grouped into a
single field.
Example 8-Figure 1-Two Shallow
Stratigraphic (Bright Spot) Reservoirs Separated Horizontally.
Example 8-Figure2-Same Two
Shallow Reseroirs as Figure 1; However the Grid is Shifted (Single Field).
Example 8-Figure 3-Two Shallow
Areally Overlapping Bright Spot Reservoirs (Single Field). |
9 |
Subsalt and above the Salt Reservoirs (On Separate Structures) on the Same
Lease Geologic setting : Two hydrocarbon accumulations on the same lease that
are not related to the same structural feature. The shallow reservoir is on an anticlinal
high and the deep reservoir is found below the salt, trapped against a salt weld. The
reservoirs vertically overlap.
MMS Field Designation: Even though these two reservoirs do not appear to be related
structurally, one being shallow (6000') and above the salt, and the other being subsalt
(13,000'), they would be considered in the same field. The reservoirs overlap vertically
and the MMS does not separate fields by depth. If the reservoirs did not overlap
vertically, the reservoirs would be in separate fields.
Example 9-Figure1-Shallow
Accumulation on Anticlinal Structure
Example 9-Figure 2-Deep Subsalt
Accumulation
Example 9-Figure 3-Cross
Sectional View
Example 9-Figure 4-Reservoir
Map-Aerial View |
10 |
Salt Ridges with Multiple Fields In
this example, there are flank traps against a salt ridge. These traps with pay are
separated by lows, and therefore are considered separate structural highs and separate
fields.
Cross Section on Example 10 |
11 |
Two Separate Structures with an Overlapping Shallow Stratigraphic Trap In
this example, there are two structural traps separated by a low. These two would be
considered separate fields except for an overlying shallow stratigraphic trap. A shallow
reservoir overlies both deeper reservoirs, causing all three to be combined into a single
field.
Example 11-Figure 1-Two Deeper
Structural Traps Separated by a Low with a Shallow Overlapping Stratigraphic Trap.
Example 11-Figure2-Reservoirs of
Deep and Shallow Traps Overlap Horizontially and Therefore are Considered a Field. |
12 |
Multiple Accumulations with
Different Structural Styles in a Salt-bounded Mini-basin This example contains four
different hydrocarbon accumulations, each with a different structural style: a piercement
salt dome with a flank trap, a fault trap, stratigraphic trap, and a trap against a salt
ridge.
Because of their structural size and relative positions they would be placed into three
fields. Field A would be the salt dome with flank trap in Block 3. Field B would be the
two traps along the fault in Block 7. Although one is a stratigraphic trap, its proximity
to the fault and the structural trap on the upthrown side would cause the two to be
combined. There are lows separating these two traps from the salt dome to the north and
the trap against the salt ridge to the south. Field C is the salt ridge trap.
Cross Section on Example 12 |
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