Changes

  | 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

  | frompg  = 2-36

  | topg    = 2-42

  | topg    = 2-37

  | 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

! System || Regime || Class || Subclass || Style

! System || Regime || Class || Subclass || Style

|-

|-

| rowspan = 4 | [[Stratigraphic trap]]s || rowspan = 4 | Diagenetic traps || rowspan = 2 | Diagenetic reservoirs; Form where [[porosity]] is created as a result of local diagenetic processes such as dissolution or dolomitization. || colspan = 2 | Secondary dolomite reservoirs; Form as a result of localized secondary dolomitization.

| rowspan = 4 | [[Stratigraphic trap]]s || rowspan = 4 | Diagenetic traps || rowspan = 2 | Diagenetic reservoirs; Form where [[porosity]] is created as a result of local [[Diagenesis|diagenetic processes]] such as [[Carbonate_reservoir_models:_facies,_diagenesis,_and_flow_characterization#Dissolution_and_associated_processes|dissolution]] or [[Carbonate_reservoir_models:_facies,_diagenesis,_and_flow_characterization#Dolomitization|dolomitization]]. || colspan = 2 | Secondary [[dolomite]] reservoirs; Form as a result of localized secondary dolomitization.

|-

|-

| colspan = 2 | Leached (secondary) porosity: Form as a result of localized leaching of nonreservoir-quality rock to create enhanced porosity and permeability. Common beneath unconformity surfaces.

| colspan = 2 | Leached (secondary) [[porosity]]: Form as a result of localized leaching of nonreservoir-quality rock to create enhanced porosity and [[permeability]]. Common beneath [[unconformity]] surfaces.

|-

|-

| rowspan = 2 | Diagenetic seals: Trap boundaries created by plugging original reservoir porosity and permeability by diagenetic cements or minerals. || colspan = 2 | Secondary anhydrite barriers; Form as a result of secondary anhydrite precipitating in original pore spaces.

| rowspan = 2 | Diagenetic seals: Trap boundaries created by plugging original reservoir porosity and permeability by diagenetic cements or minerals. || colspan = 2 | Secondary [[anhydrite]] barriers; Form as a result of [[Carbonate_reservoir_models:_facies,_diagenesis,_and_flow_characterization#Evaporite_mineralization|secondary anhydrite precipitating]] in original pore spaces.

|-

|-

| Secondary clay barriers; Form as a result of secondary clay, commonly kaolinite, precipitating in original pore space. || Secondary pore-throat trap; Caused by a reduction in the size of pore-throat radii of reservoir rocks by depositional or diagenetic processes. These trap types typically have relatively porous units in the sealing facies that are impermeable to oil migration due to capillary restraints but contain producible water.

| Secondary clay barriers; Form as a result of secondary clay, commonly [[kaolinite]], precipitating in original pore space. || Secondary pore-throat trap; Caused by a reduction in the size of [[Pore system fundamentals|pore-throat]] radii of reservoir rocks by depositional or diagenetic processes. These trap types typically have relatively porous units in the sealing facies that are impermeable to oil [[migration]] due to [[Capillary pressure|capillary restraints]] but contain producible water.

|}

|}

==Discussion of diagenetic trap families==

==Discussion of diagenetic trap families==

Families of diagenetic traps based on genesis of the diagenetic processes that created or modified either the reservoir or the seal are somewhat difficult to establish because not all diagenetic processes are well understood and disagreements often exist about the cause of specific diagenetic processes that trapped hydrocarbons. Furthermore, almost all reservoirs and seals have undergone some degree of diagenesis since deposition, making diagenesis at least a secondary trapping element in many fields.

Families of diagenetic traps based on genesis of the diagenetic processes that created or modified either the reservoir or the seal are somewhat difficult to establish because not all diagenetic processes are well understood and disagreements often exist about the cause of specific diagenetic processes that trapped hydrocarbons. Furthermore, almost all reservoirs and seals have undergone some degree of [[diagenesis]] since deposition, making diagenesis at least a secondary trapping element in many fields.

The common occurrence of dolomitized reservoirs is a classic case in point. Dolomitized reefs and dolomitized tidal-flat carbonates are common oil and gas reservoirs. Although dolomitization was a critical element in creating commercial porosity and permeability in these reservoirs, exploration efforts usually focus on defining the original depositional fairway of these reservoirs, i.e., reefs or tidal flats. As a consequence, the primary trap classification of these reservoirs occurs under the depositional trap regime. For our purposes, diagenetic traps are those in which trap boundaries are created by diagenetic processes largely independent of the original depositional environment of reservoir or seal.

The common occurrence of dolomitized reservoirs is a classic case in point. Dolomitized reefs and dolomitized tidal-flat carbonates are common oil and gas reservoirs. Although [[Carbonate_reservoir_models:_facies,_diagenesis,_and_flow_characterization#Dolomitization|dolomitization]] was a critical element in creating commercial porosity and permeability in these reservoirs, exploration efforts usually focus on defining the original depositional fairway of these reservoirs, i.e., [[Carbonate_reservoir_models:_facies,_diagenesis,_and_flow_characterization#Carbonate_sediments_and_environments|reefs or tidal flats]]. As a consequence, the primary trap classification of these reservoirs occurs under the [[depositional trap regime]]. For our purposes, diagenetic traps are those in which trap boundaries are created by diagenetic processes largely independent of the original depositional environment of reservoir or seal.

==Families==

==Families==

! System || Class || Subclass || Family || Subfamily || Variety

! System || Class || Subclass || Family || Subfamily || Variety

|-

|-

| rowspan = 3 | Diagenetic traps || rowspan = 2 | Diagenetic reservoirs || Secondary dolomite reservoirs || Hydrothermal diagenesis || colspan = 2 | Ascending hot brines

| rowspan = 3 | Diagenetic traps || rowspan = 2 | Diagenetic reservoirs || Secondary dolomite reservoirs || [[Hydrothermal diagenesis]] || colspan = 2 | Ascending hot brines

|-

|-

| Leached (secondary) porosity || Subunconformity diagenesis || Dissolving || Karst and cavern formation

| Leached (secondary) porosity || Subunconformity diagenesis || Dissolving || [[Karst]] and cavern formation

|-

|-

| Diagenetic seals || Secondary anhydrite barrier || Subunconformity diagenesis || colspan = 2 | Cementation

| Diagenetic seals || Secondary anhydrite barrier || Subunconformity diagenesis || colspan = 2 | Cementation

|}

|}

==See also==

==See also==

* [[Depositional trap regime]]

* [[Depositional trap regime]]

* [[Erosional trap regime]]

* [[Erosional trap regime]]

==External links==

==External links==

[[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]]