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  | isbn    = 0891816607
 
  | isbn    = 0891816607
 
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Stratigraphically complex fields are those that exhibit a high degree of vertical and lateral heterogeneity that is directly controlled by the environment of deposition (Table 1). This heterogeneity occurs at all scales (see [[Geological heterogeneities]]). It can result in a highly variable distribution of rock properties within one reservoir and the division of a single stratigraphic interval into multiple reservoirs that act as independent, self-contained compartments.
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Stratigraphically complex fields are those that exhibit a high degree of vertical and [[lateral]] heterogeneity that is directly controlled by the environment of deposition (Table 1). This heterogeneity occurs at all scales (see [[Geological heterogeneities]]). It can result in a highly variable distribution of rock properties within one reservoir and the division of a single stratigraphic interval into multiple reservoirs that act as independent, self-contained compartments.
    
==Degree of hetrogeneity==
 
==Degree of hetrogeneity==
 
{| class = "wikitable"
 
{| class = "wikitable"
 
|-
 
|-
|+ {{table number|1}}Tentative, relative depositional heterogeneity ranking of reservoir facies based primarily on Texas petroleum fields
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|+ {{table number|1}}Tentative, relative depositional heterogeneity ranking of reservoir facies based primarily on Texas [[petroleum]] fields
 
|-
 
|-
 
! Depositional Environment
 
! Depositional Environment
 
! Heterogeneity Rank
 
! Heterogeneity Rank
 
|-
 
|-
| ''' Siliciclastic Systems '''
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| colspan=2 | ''' Siliciclastic Systems '''
|
  −
 
   
|-
 
|-
 
|   Submarine slope/fan/canyon fill, silty to muddy
 
|   Submarine slope/fan/canyon fill, silty to muddy
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| 8.0
 
| 8.0
 
|-
 
|-
|   Fluvial or deltaic sandstone on carbonate shelf
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|   Fluvial or deltaic [[sandstone]] on carbonate shelf
 
| 8.0
 
| 8.0
 
|-
 
|-
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| 2.0
 
| 2.0
 
|-
 
|-
| ''' Carbonate Systems '''
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| colspan=2 | ''' Carbonate Systems '''
|
  −
 
   
|-
 
|-
 
|   Evaporitic flats (sabkhas)
 
|   Evaporitic flats (sabkhas)
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| 8.5
 
| 8.5
 
|-
 
|-
|   Open shelves, extensive diagenesis
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|   Open shelves, extensive [[diagenesis]]
 
| 8.0
 
| 8.0
 
|-
 
|-
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| 8.0
 
| 8.0
 
|-
 
|-
|   Karstic unconformity zones
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|   Karstic [[unconformity]] zones
 
| 8.0
 
| 8.0
 
|-
 
|-
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* Questionable correlation of depositional packages between wells
 
* Questionable correlation of depositional packages between wells
 
* Presence of numerous vertical [[permeability]] barriers at a variety of scales
 
* Presence of numerous vertical [[permeability]] barriers at a variety of scales
* Complex [[porosity]]-permeability and [[capillary pressure]] relationships (a broad scatter in the data indicates different lithofacies and pore types)
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* Complex [[porosity]]-permeability and [[capillary pressure]] relationships (a broad scatter in the data indicates different [[lithofacies]] and pore types)
 
* Anomalous changes in pressure gradient
 
* Anomalous changes in pressure gradient
 
* Variable oil and water chemical composition
 
* Variable oil and water chemical composition
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* Multiple [[fluid contacts]] at different structural elevations
 
* Multiple [[fluid contacts]] at different structural elevations
* Irregular reservoir distribution (such as a dry hole surrounded by producers)
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* Irregular reservoir distribution (such as a [[dry hole]] surrounded by producers)
 
* Anomalous fluid relationships (such as a gas zone underlying an oil zone or an oil zone downdip of water)
 
* Anomalous fluid relationships (such as a gas zone underlying an oil zone or an oil zone downdip of water)
 
* Irregular and/or highly directional waterflood response
 
* Irregular and/or highly directional waterflood response
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==Evaluation==
 
==Evaluation==
 +
 +
[[file:evaluating-stratigraphically-complex-fields_fig1.png|thumb|300px|{{figure number|1}}Example of electrofacies map showing distribution of SP log patterns. (From Galloway and Cheng.<ref name=pt06r35>Galloway, W. E., Cheng, E. S. S., 1985, Reservoir facies architecture in a microtidal barrier system—Frio Formation, Texas Gulf Coast: The University of Texas Bureau of Economic Geology, Report of Investigations, v. 144, 36 p.</ref>)]]
    
Recognition and three-dimensional characterization of reservoir heterogeneity in a stratigraphically complex field requires a well-by-well analysis of the following:
 
Recognition and three-dimensional characterization of reservoir heterogeneity in a stratigraphically complex field requires a well-by-well analysis of the following:
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* Understand the basic regional and local geological setting.
 
* Understand the basic regional and local geological setting.
* Describe lithofacies and interpreted depositional environment(s) (see “Lithofacies and Environmental Analysis of Clastic Depositional Systems”).
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* Describe lithofacies and interpreted depositional environment(s) (see [[Lithofacies and environmental analysis of clastic depositional systems]]).
 
* Determine the relationship between lithofacies/depositional environment and reservoir distribution and quality.
 
* Determine the relationship between lithofacies/depositional environment and reservoir distribution and quality.
 
* Determine reservoir distribution.
 
* Determine reservoir distribution.
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* Use reservoir simulation model to manage field.
 
* Use reservoir simulation model to manage field.
 
* Refine reservoir description and calibrate reservoir simulation model.
 
* Refine reservoir description and calibrate reservoir simulation model.
  −
[[file:evaluating-stratigraphically-complex-fields_fig1.png|thumb|{{figure number|1}}Example of electrofacies map showing distribution of SP log patterns. (From <ref name=pt06r35>Galloway, W. E., Cheng, E. S. S., 1985, Reservoir facies architecture in a microtidal barrier system—Frio Formation, Texas Gulf Coast: The University of Texas Bureau of Economic Geology, Report of Investigations, v. 144, 36 p.</ref>.)]]
      
==See also==
 
==See also==
 
* [[Introduction to geological methods]]
 
* [[Introduction to geological methods]]
 
* [[Lithofacies and environmental analysis of clastic depositional systems]]
 
* [[Lithofacies and environmental analysis of clastic depositional systems]]
* [[Monte carlo and stochastic simulation methods]]
   
* [[Subsurface maps]]
 
* [[Subsurface maps]]
 
* [[Flow units for reservoir characterization]]
 
* [[Flow units for reservoir characterization]]
 
* [[Effective pay determination]]
 
* [[Effective pay determination]]
* [[Multivariate data analysis]]
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* [[Cross section]]
* [[Geological cross sections]]
   
* [[Evaluating structurally complex reservoirs]]
 
* [[Evaluating structurally complex reservoirs]]
 
* [[Conversion of well log data to subsurface stratigraphic and structural information]]
 
* [[Conversion of well log data to subsurface stratigraphic and structural information]]
 
* [[Evaluating tight gas reservoirs]]
 
* [[Evaluating tight gas reservoirs]]
* [[Correlation and regression analysis]]
   
* [[Reservoir quality]]
 
* [[Reservoir quality]]
* [[Carbonate reservoir models: Facies, diagenesis, and flow characterization]]
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* [[Carbonate reservoir models: facies, diagenesis, and flow characterization]]
 
* [[Fluid contacts]]
 
* [[Fluid contacts]]
 
* [[Geological heterogeneities]]
 
* [[Geological heterogeneities]]
 
* [[Evaluating fractured reservoirs]]
 
* [[Evaluating fractured reservoirs]]
 
* [[Evaluating diagenetically complex reservoirs]]
 
* [[Evaluating diagenetically complex reservoirs]]
* [[Statistics overview]]
      
==References==
 
==References==
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[[Category:Geological methods]]
 
[[Category:Geological methods]]
 +
[[Category:Methods in Exploration 10]]

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