Difference between revisions of "Depositional trap regime"

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  | part    = Traps, trap types, and the petroleum system
 
  | part    = Traps, trap types, and the petroleum system
 
  | chapter = Classification of exploration traps
 
  | chapter = Classification of exploration traps
  | frompg  = 2-1
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  | frompg  = 2-30
  | topg    = 2-42
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  | topg    = 2-33
 
  | author  = Richard R. Vincelette, Edward A. Beaumont, Norman H. Foster
 
  | author  = Richard R. Vincelette, Edward A. Beaumont, Norman H. Foster
 
  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch02/ch02.htm
 
  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch02/ch02.htm
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  | isbn    = 0-89181-602-X
 
  | isbn    = 0-89181-602-X
 
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Traps in the depositional regime formed primarily by processes that created facies changes between reservoir and seal-quality rocks. Besides deposition by sedimentary processes, this regime also includes deposition by igneous processes.
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Traps in the depositional regime formed primarily by processes that created facies changes between reservoir and seal-quality rocks. Besides deposition by sedimentary processes, this regime also includes deposition by [[igneous]] processes.
  
 
==Classes==
 
==Classes==
 
The basis for the three classes of the depositional regime is the geometric arrangement of the facies resulting from depositional processes. The subclasses describe reservoir composition or lithology. Where described, trap styles can be listed based on the lithology or composition of the sealing rocks. The outline below shows the classes and subclasses of the depositional regime.
 
The basis for the three classes of the depositional regime is the geometric arrangement of the facies resulting from depositional processes. The subclasses describe reservoir composition or lithology. Where described, trap styles can be listed based on the lithology or composition of the sealing rocks. The outline below shows the classes and subclasses of the depositional regime.
 
+
{{clear}}
'''System:''' Stratigraphic
+
{| class = "wikitable"
:'''Regime:''' Depositional
+
|-
:Trap boundaries are created primarily by depositional processes and can involve igneous rocks as well as sedimentary rocks. Three classes are recognized, based on whether the trap involves an isolated reservoir, an updip pinch-out, or depositional relief on top of the reservoir.
+
! System || Regime || Class || Subclass || Style
::'''Class:''' Isolated (local) depositional reservoirs
+
|-
::Reservoir rock is partially or completely isolated by sealing rocks, which provide top, side, and often bottom seals. These traps are often of limited areal extent, with trap closure defined largely by reservoir distribution.
+
| rowspan = 11 | ''Stratigraphic'' || rowspan = 11 | ''Depositional''; Trap boundaries are created primarily by depositional processes and can involve igneous rocks as well as sedimentary rocks. Three classes are recognized, based on whether the trap involves an isolated reservoir, an updip pinch-out, or depositional relief on top of the reservoir. || rowspan = 3 | ''Isolated (local) depositional reservoirs''; Reservoir rock is partially or completely isolated by sealing rocks, which provide top, side, and often bottom seals. These traps are often of limited areal extent, with trap closure defined largely by reservoir distribution. || colspan = 2 | ''Sandstone reservoirs''; Partially or completely isolated by seal.
:::'''Subclass:''' Sandstone reservoirs
+
|-
:::Partially or completely isolated by seal.
+
| colspan = 2 | ''Carbonate reservoirs''; Partially or completely isolated by seal.
:::'''Subclass:''' Carbonate reservoirs
+
|-
:::Partially or completely isolated by seal.
+
| colspan = 2 | ''Igneous reservoirs''; Partially isolated by seal.
:::'''Subclass:''' Igneous reservoirs
+
|-
:::Partially isolated by seal.
+
| rowspan = 4 | ''Depositional pinch-outs''; Depositional processes form an updip pinch-out of permeable rock into impermeable rock. Trap closure is usually created by an updip re-entrant of the pinch-out boundary or by a combination of the pinch-out with other trap elements, such as tectonic nosing or [[hydrodynamics]]. Pinch-out boundaries typically involve top, side, and bottom seals. || colspan = 2 | ''Regional sandstone pinch-outs''; Regional updip pinch-outs of sandstone into an impermeable facies such as shale or [[anhydrite]].
::'''Class:''' Depositional pinch-outs
+
|-
::Depositional processes form an updip pinch-out of permeable rock into impermeable rock. Trap closure is usually created by an updip re-entrant of the pinch-out boundary or by a combination of the pinch-out with other trap elements, such as tectonic nosing or [[hydrodynamics]]. Pinch-out boundaries typically involve top, side, and bottom seals.
+
| colspan = 2 | ''Local sandstone pinch-outs''; Local updip pinch-outs of sandstone into an impermeable facies such as shale or anhydrite.
:::'''Subclass:''' Regional sandstone pinch-outs
+
|-
:::Regional updip pinch-outs of sandstone into an impermeable facies such as shale or anhydrite.
+
| colspan = 2 | ''Regional carbonate pinch-outs''; Regional updip pinch-outs of carbonate into an impermeable facies such as shale or anhydrite.
:::'''Subclass:''' Local sandstone pinch-outs
+
|-
:::Local updip pinch-outs of sandstone into an impermeable facies such as shale or anhydrite.
+
| colspan = 2 | ''Local carbonate pinch-outs''; Local updip pinch-outs of carbonate into an impermeable facies such as shale or anhydrite.
:::'''Subclass:''' Regional carbonate pinch-outs
+
|-
:::Regional updip pinch-outs of carbonate into an impermeable facies such as shale or anhydrite.
+
| rowspan = 4 | ''Depositional relief traps''; Process forms positive relief on top of the reservoir; this topographic relief between top seal and reservoir creates the trap closure. || colspan = 2 | ''Sandstone depositional relief traps''
:::'''Subclass:''' Local carbonate pinch-outs
+
|-
:::Local updip pinch-outs of carbonate into an impermeable facies such as shale or anhydrite.
+
| rowspan = 3 | ''Carbonate depositional relief traps'' || ''Carbonate reservoirs sealed by shale''
::'''Class:''' Depositional relief traps
+
|-
::Process forms positive relief on top of the reservoir; this topographic relief between top seal and reservoir creates the trap closure.
+
| ''Carbonate reservoirs sealed by tight carbonate''
:::'''Subclass:''' Sandstone depositional relief traps
+
|-
:::'''Subclass:''' Carbonate depositional relief traps
+
| ''Carbonate reservoirs sealed by evaporites''
::::'''Style:''' Carbonate reservoirs sealed by shale
+
|}
::::'''Style:''' Carbonate reservoirs sealed by tight carbonate
 
::::'''Style:''' Carbonate reservoirs sealed by evaporites
 
  
 
==Families==
 
==Families==
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Note that the same genetic families and subfamilies can be used for different depositional classes (geometry). This lets cross-correlations be made between different geometric trap classes within similar genetic settings, e.g., isolated reservoirs or pinch-outs within the shallow marine environment. Thus, if desired, trap classes can be combined under similar trap families. Examples of the more common depositional trap superfamilies, families, and subfamilies are given below.
 
Note that the same genetic families and subfamilies can be used for different depositional classes (geometry). This lets cross-correlations be made between different geometric trap classes within similar genetic settings, e.g., isolated reservoirs or pinch-outs within the shallow marine environment. Thus, if desired, trap classes can be combined under similar trap families. Examples of the more common depositional trap superfamilies, families, and subfamilies are given below.
  
'''Regime:''' Depositional reservoirs
+
{| class = "wikitable"
:'''Class:''' Isolated depositional reservoirs
+
|-
::'''Subclass:''' Isolated carbonate reservoirs
+
! rowspan = 3 | Regime || rowspan = 3 | Class || rowspan = 3 | Subclass || rowspan = 3 | Superfamily || rowspan = 3 | Family || rowspan = 3 | Subfamily || colspan = 4 | Variety
:::'''Superfamily:''' Marine carbonate reservoirs
+
|-
::::'''Family:''' Open-shelf (high-energy) carbonates
+
! rowspan = 2 | Reservoir Variety || colspan = 3 | Seal Variety
:::::'''Subfamily:''' Shoal
+
|-
::::::'''Variety:''' Oolite
+
! Top || Side || Bottom
::::::'''Variety:''' Skeletal
+
|-
::::'''Family:''' Tidal-zone carbonates
+
| rowspan = 27 | ''Depositional reservoirs'' || rowspan = 12 | ''Isolated depositional reservoirs'' || rowspan = 3 | ''Isolated carbonate reservoirs'' || rowspan = 3 | ''Marine carbonate reservoirs'' || rowspan = 2 | ''Open-shelf (high-energy) carbonates'' || rowspan = 2 | ''Shoal'' || colspan = 4 | ''Oolite''
:::::'''Subfamily:''' Tidal channel
+
|-
::'''Subclass:''' Isolated sandstone reservoirs
+
| colspan = 4 | ''Skeletal''
:::'''Superfamily:''' Marine sandstone traps
+
|-
::::'''Family:''' Shallow-water sandstone reservoirs
+
| ''Tidal-zone carbonates'' || colspan = 5 | ''Tidal channel''
:::::'''Subfamily:''' Beach
+
|-
:::::'''Subfamily:''' Barrier island
+
| rowspan = 8 | ''Isolated sandstone reservoirs'' || rowspan = 6 | ''Marine sandstone traps'' || rowspan = 3 | ''Shallow-water sandstone reservoirs'' || colspan = 5 | ''Beach''
:::::'''Subfamily:''' Offshore bar
+
|-
::::'''Family:''' Deepwater sandstone reservoirs
+
| colspan = 5 | ''Barrier island''
:::::'''Subfamily:''' Turbidites
+
|-
:::::'''Subfamily:''' Turbidite channel
+
| colspan = 5 | ''Offshore bar''
:::::'''Subfamily:''' Submarine fans
+
|-
:::'''Superfamily:''' Alluvial sandstone reservoirs
+
| rowspan = 3 | ''Deepwater sandstone reservoirs'' || colspan = 5 | ''[[Turbidite]]s''
::::'''Family:''' Fluvial
+
|-
:::::'''Subfamily:''' Channel
+
| colspan = 5 | ''Turbidite channel''
::::::'''Variety:''' Deltaic
+
|-
::::'''Family:''' Deltaic
+
| colspan = 5 | ''Submarine fans''
:::::'''Subfamily:''' Distributary channel
+
|-
::'''Subclass:''' Isolated igneous reservoirs
+
| rowspan = 2 | ''[[Alluvial]] sandstone reservoirs || ''Fluvial'' || ''Channel'' || colspan = 4 | ''Deltaic''
:::'''Superfamily:''' Intrusive igneous bodies
+
|-
::::'''Family:''' Intrusive sills
+
| ''Deltaic'' || colspan = 5 | ''[[Distributary channel]]''
:'''Class:''' Depositional pinch-outs
+
|-
::'''Subclass:''' Sandstone pinch-outs
+
| ''Isolated igneous reservoirs'' || ''Intrusive igneous bodies'' || colspan = 6 | ''Intrusive sills''
:::'''Superfamily:''' Marine sandstone pinch-outs
+
|-
::::'''Family:''' Shallow marine
+
| rowspan = 7 | ''Depositional pinch-outs'' || rowspan = 4 | ''Sandstone pinch-outs'' || rowspan = 3 | ''Marine sandstone pinch-outs'' || rowspan = 3 | ''Shallow marine''; Updip pinch-out of shallow marine sands into lagoonal or basinal shales and silts. || rowspan = 3 | ''Barrier bar'' || colspan = 4 | ''Pinch-out into lagoonal shale''
::::Updip pinch-out of shallow marine sands into lagoonal or basinal shales and silts.
+
|-
:::::'''Subfamily:''' Barrier bar
+
| colspan = 4 | ''Pinch out into marine shale''
::::::'''Variety:''' Pinch-out into lagoonal shale
+
|-
::::::'''Variety:''' Pinch-out into marine shale
+
| ''Deep marine'' || colspan = 5 | ''Turbidite''; Updip pinch-out of marine turbidite sandstone into marine shale.
::::'''Family:''' Deep marine
+
|-
:::::'''Subfamily:''' Turbidite
+
| ''Lacustrine sandstone pinch-outs'' || colspan = 6 | ''Lacustrine delta pinch-out''
:::::Updip pinch-out of marine turbidite sandstone into marine shale.
+
|-
:::'''Superfamily:''' Lacustrine sandstone pinch-outs
+
| rowspan = 3 | ''Carbonate pinch-outs'' || rowspan = 3 | ''Marine carbonate pinch-outs'' || ''Tidal zone'' || ''Tidal-flat carbonate pinch-out'' || colspan = 4 | ''Pinch-out into silts and shales''
::::'''Family:''' Lacustrine delta pinch-out
+
|-
::'''Subclass:''' Carbonate pinch-outs
+
| rowspan = 4 | ''Pinch-out into tight dolomites and anhydrite''
:::'''Superfamily:''' Marine carbonate pinch-outs
+
|-
::::'''Family:''' Tidal zone
+
| ''Open shelf (high energy)'' || ''Carbonate bank pinch-out'' || ''Rudistid [[limestone]] bank'' || ''Marine shale'' || ''Tight shelf limestone ''
:::::'''Subfamily:''' Tidal-flat carbonate pinch-out
+
|-
::::::'''Variety:''' Pinch-out into silts and shales
+
| rowspan = 6 | ''Depositional relief'' || rowspan = 2 | ''Sandstone'' || ''Eolian sandstone reservoirs'' || colspan = 6 | ''Dune''
::::::'''Variety:''' Pinch-out into tight dolomites and anhydrite
+
|-
::::'''Family:''' Open shelf (high energy)
+
| ''Marine sandstone reservoirs'' || ''Deep water'' || colspan = 5 | ''Turbidite fan''
:::::'''Subfamily:''' Carbonate bank pinch-out
+
|-
::::::'''Reservoir variety:''' Rudistid limestone bank
+
| rowspan = 4 | ''Carbonate'' || rowspan = 4 | ''Marine carbonate reservoirs'' || rowspan = 4 | ''Bioherms''; Trap results from depositional relief created by porous organic carbonate buildup sealed by overlying and adjacent tight lithologies. These buildups are commonly referred to as reefs. A wide variety of reef traps have been described and classified based upon both the environment of deposition and geometry of the carbonate reservoir. Oil and gas have been trapped in barrier reefs, fringing reefs, platform reefs, atoll reefs, patch reefs, pinnacle reefs, reef mounds (or mud mounts), and carbonate banks.<ref name=JG1984 /> These terms can be used as subfamilies, as noted below. If a more detailed classification is needed, varieties can be established based upon the facies and genesis of the sealing units surrounding the buildups. || colspan = 5 | ''Pinnacle reefs''; High-relief, circular or ovoid mounds created by upward grown of carbonate frame-building organisms in basinal setting. Reef typically contains a significant amount of high-energy carbonate detritus (grain-stones, wackestones) as well as boundstones and framestones. Reef width is less than 10% of height.<ref name=JG1984>James, N. P., and H. H. J. Gelsetzer, 1984, Introduction, in H. H. J. Geldsetzer, N. P. James, and G . E. Tebbutt,eds.,Reefs—Canada and Adjacent Areas: Canadian Society of Petroleum Geologists Memoir 13, p. 1–8.</ref>
::::::'''Seal variety:'''
+
|-
:::::::'''Top:''' Marine shale
+
| colspan = 5 | ''Platform reefs''; Larger reefal carbonate buildup in which lateral dimensions are measured in kilometers and in which reef width is more than 10 times reef height.<ref name=JG1984 />
:::::::'''Side:''' Tight shelf limestone
+
|-
:'''Class:''' Depositional relief
+
| colspan = 5 | ''Patch reefs''; Small, low-relief carbonate mounds developed by frame-building organisms on top of a shelf.
::'''Subclass:''' Sandstone
+
|-
:::'''Superfamily:''' Eolian sandstone reservoirs
+
| colspan = 5 | ''Mud mounds''; Depositional carbonate mounds consisting largely of clean lime [[mudstone]] with relatively little macro-fossil debris.
::::'''Family:''' Dune
+
|-
:::'''Superfamily:''' Marine sandstone reservoirs
+
| rowspan = 2 | ''[[Unconformity|Supraunconformity]] traps'' || ''Onlap pinch-out'' || ''Nonmarine erosion surface'' || ''Sequence-boundary unconformity onlap'' || ''Depositional re-entrant'' || ''Deltaic sandstone pinch-out'' || colspan = 2 | ''Deltaic shale'' || ''Subunconformity units''
::::'''Family:''' Deep water
+
|-
:::::'''Subfamily:''' Turbidite fan
+
| ''Subclass: Buttress pinch-outs'' || ''Nonmarine erosional surface'' || ''Sequence-boundary unconformity buttress'' || ''Pinch-out against erosional ridge'' || ''[[Alluvial]] sandstone'' || ''Nonmarine shale'' || ''Marine shale of sub crop ridge'' || ''Marine shale beneath unconformity''
::'''Subclass:''' Carbonate
+
|}
:::'''Superfamily:''' Marine carbonate reservoirs
 
::::'''Family:''' Bioherms
 
::::Trap results from depositional relief created by porous organic carbonate buildup sealed by overlying and adjacent tight lithologies. These buildups are commonly referred to as reefs. A wide variety of reef traps have been described and classified based upon both the environment of deposition and geometry of the carbonate reservoir. Oil and gas have been trapped in barrier reefs, fringing reefs, platform reefs, atoll reefs, patch reefs, pinnacle reefs, reef mounds (or mud mounts), and carbonate banks (James and Gelsetzer, 1989). These terms can be used as subfamilies, as noted below. If a more detailed classification is needed, varieties can be established based upon the facies and genesis of the sealing units surrounding the buildups.
 
:::::'''Subfamily:''' Pinnacle reefs
 
:::::High-relief, circular or ovoid mounds created by upward grown of carbonate frame-building organisms in basinal setting. Reef typically contains a significant amount of high-energy carbonate detritus (grain-stones, wackestones) as well as boundstones and framestones. Reef width is less than 10% of height (James and Geldsetzer, 1989).
 
:::::'''Subfamily:''' Platform reefs
 
:::::Larger reefal carbonate buildup in which lateral dimensions are measured in kilometers and in which reef width is more than 10 times reef height (James and Geldsetzer, 1989).
 
:::::'''Subfamily:''' Patch reefs
 
:::::Small, low-relief carbonate mounds developed by frame-building organisms on top of a shelf.
 
:::::'''Subfamily:''' Mud mounds
 
:::::Depositional carbonate mounds consisting largely of clean lime mudstone with relatively little macro-fossil debris.
 
:'''Class:''' Supraunconformity traps
 
::'''Subclass:''' Onlap pinch-out
 
:::'''Superfamily:''' Nonmarine erosion surface
 
::::'''Family:''' Sequence-boundary unconformity onlap
 
:::::'''Subfamily:''' Depositional re-entrant
 
::::::'''Reservoir variety:''' Deltaic sandstone pinch-out
 
::::::'''Seal variety:'''
 
:::::::'''Top:''' Deltaic shale
 
:::::::'''Bottom:''' Subunconformity units
 
::'''Subclass:''' Buttress pinch-outs
 
:::'''Superfamily:''' Nonmarine erosional surface
 
::::'''Family:''' Sequence-boundary unconformity buttress
 
:::::'''Subfamily:''' Pinch-out against erosional ridge
 
::::::'''Reservoir variety:''' Alluvial sandstone
 
::::::'''Seal variety:'''
 
:::::::'''Top:''' Nonmarine shale
 
:::::::'''Side:''' Marine shale of subcrop ridge
 
:::::::'''Bottom:''' Marine shale beneath unconformity
 
  
 
==See also==
 
==See also==
Line 149: Line 118:
 
* [[Erosional trap regime]]
 
* [[Erosional trap regime]]
 
* [[Diagenetic trap regime]]
 
* [[Diagenetic trap regime]]
 +
 +
==References==
 +
{{reflist}}
  
 
==External links==
 
==External links==
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[[Category:Traps, trap types, and the petroleum system]]  
 
[[Category:Traps, trap types, and the petroleum system]]  
 
[[Category:Classification of exploration traps]]
 
[[Category:Classification of exploration traps]]
 +
[[Category:Treatise Handbook 3]]

Latest revision as of 20:28, 4 January 2024

Exploring for Oil and Gas Traps
Series Treatise in Petroleum Geology
Part Traps, trap types, and the petroleum system
Chapter Classification of exploration traps
Author Richard R. Vincelette, Edward A. Beaumont, Norman H. Foster
Link Web page
Store AAPG Store

Traps in the depositional regime formed primarily by processes that created facies changes between reservoir and seal-quality rocks. Besides deposition by sedimentary processes, this regime also includes deposition by igneous processes.

Classes

The basis for the three classes of the depositional regime is the geometric arrangement of the facies resulting from depositional processes. The subclasses describe reservoir composition or lithology. Where described, trap styles can be listed based on the lithology or composition of the sealing rocks. The outline below shows the classes and subclasses of the depositional regime.

System Regime Class Subclass Style
Stratigraphic Depositional; Trap boundaries are created primarily by depositional processes and can involve igneous rocks as well as sedimentary rocks. Three classes are recognized, based on whether the trap involves an isolated reservoir, an updip pinch-out, or depositional relief on top of the reservoir. Isolated (local) depositional reservoirs; Reservoir rock is partially or completely isolated by sealing rocks, which provide top, side, and often bottom seals. These traps are often of limited areal extent, with trap closure defined largely by reservoir distribution. Sandstone reservoirs; Partially or completely isolated by seal.
Carbonate reservoirs; Partially or completely isolated by seal.
Igneous reservoirs; Partially isolated by seal.
Depositional pinch-outs; Depositional processes form an updip pinch-out of permeable rock into impermeable rock. Trap closure is usually created by an updip re-entrant of the pinch-out boundary or by a combination of the pinch-out with other trap elements, such as tectonic nosing or hydrodynamics. Pinch-out boundaries typically involve top, side, and bottom seals. Regional sandstone pinch-outs; Regional updip pinch-outs of sandstone into an impermeable facies such as shale or anhydrite.
Local sandstone pinch-outs; Local updip pinch-outs of sandstone into an impermeable facies such as shale or anhydrite.
Regional carbonate pinch-outs; Regional updip pinch-outs of carbonate into an impermeable facies such as shale or anhydrite.
Local carbonate pinch-outs; Local updip pinch-outs of carbonate into an impermeable facies such as shale or anhydrite.
Depositional relief traps; Process forms positive relief on top of the reservoir; this topographic relief between top seal and reservoir creates the trap closure. Sandstone depositional relief traps
Carbonate depositional relief traps Carbonate reservoirs sealed by shale
Carbonate reservoirs sealed by tight carbonate
Carbonate reservoirs sealed by evaporites

Families

Genetic families for the various depositional trap classes and subclasses have been established based primarily on the genesis of the reservoir. Where desired, trap varieties can be added based on the genesis or origin of the sealing units. Larger superfamilies have been created based on the general depositional environment of the reservoir, i.e., marine, continental, or lacustrine.

Note that the same genetic families and subfamilies can be used for different depositional classes (geometry). This lets cross-correlations be made between different geometric trap classes within similar genetic settings, e.g., isolated reservoirs or pinch-outs within the shallow marine environment. Thus, if desired, trap classes can be combined under similar trap families. Examples of the more common depositional trap superfamilies, families, and subfamilies are given below.

Regime Class Subclass Superfamily Family Subfamily Variety
Reservoir Variety Seal Variety
Top Side Bottom
Depositional reservoirs Isolated depositional reservoirs Isolated carbonate reservoirs Marine carbonate reservoirs Open-shelf (high-energy) carbonates Shoal Oolite
Skeletal
Tidal-zone carbonates Tidal channel
Isolated sandstone reservoirs Marine sandstone traps Shallow-water sandstone reservoirs Beach
Barrier island
Offshore bar
Deepwater sandstone reservoirs Turbidites
Turbidite channel
Submarine fans
Alluvial sandstone reservoirs Fluvial Channel Deltaic
Deltaic Distributary channel
Isolated igneous reservoirs Intrusive igneous bodies Intrusive sills
Depositional pinch-outs Sandstone pinch-outs Marine sandstone pinch-outs Shallow marine; Updip pinch-out of shallow marine sands into lagoonal or basinal shales and silts. Barrier bar Pinch-out into lagoonal shale
Pinch out into marine shale
Deep marine Turbidite; Updip pinch-out of marine turbidite sandstone into marine shale.
Lacustrine sandstone pinch-outs Lacustrine delta pinch-out
Carbonate pinch-outs Marine carbonate pinch-outs Tidal zone Tidal-flat carbonate pinch-out Pinch-out into silts and shales
Pinch-out into tight dolomites and anhydrite
Open shelf (high energy) Carbonate bank pinch-out Rudistid limestone bank Marine shale Tight shelf limestone
Depositional relief Sandstone Eolian sandstone reservoirs Dune
Marine sandstone reservoirs Deep water Turbidite fan
Carbonate Marine carbonate reservoirs Bioherms; Trap results from depositional relief created by porous organic carbonate buildup sealed by overlying and adjacent tight lithologies. These buildups are commonly referred to as reefs. A wide variety of reef traps have been described and classified based upon both the environment of deposition and geometry of the carbonate reservoir. Oil and gas have been trapped in barrier reefs, fringing reefs, platform reefs, atoll reefs, patch reefs, pinnacle reefs, reef mounds (or mud mounts), and carbonate banks.[1] These terms can be used as subfamilies, as noted below. If a more detailed classification is needed, varieties can be established based upon the facies and genesis of the sealing units surrounding the buildups. Pinnacle reefs; High-relief, circular or ovoid mounds created by upward grown of carbonate frame-building organisms in basinal setting. Reef typically contains a significant amount of high-energy carbonate detritus (grain-stones, wackestones) as well as boundstones and framestones. Reef width is less than 10% of height.[1]
Platform reefs; Larger reefal carbonate buildup in which lateral dimensions are measured in kilometers and in which reef width is more than 10 times reef height.[1]
Patch reefs; Small, low-relief carbonate mounds developed by frame-building organisms on top of a shelf.
Mud mounds; Depositional carbonate mounds consisting largely of clean lime mudstone with relatively little macro-fossil debris.
Supraunconformity traps Onlap pinch-out Nonmarine erosion surface Sequence-boundary unconformity onlap Depositional re-entrant Deltaic sandstone pinch-out Deltaic shale Subunconformity units
Subclass: Buttress pinch-outs Nonmarine erosional surface Sequence-boundary unconformity buttress Pinch-out against erosional ridge Alluvial sandstone Nonmarine shale Marine shale of sub crop ridge Marine shale beneath unconformity

See also

References

  1. 1.0 1.1 1.2 James, N. P., and H. H. J. Gelsetzer, 1984, Introduction, in H. H. J. Geldsetzer, N. P. James, and G . E. Tebbutt,eds.,Reefs—Canada and Adjacent Areas: Canadian Society of Petroleum Geologists Memoir 13, p. 1–8.

External links

find literature about
Depositional trap regime
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