Reservoir heterogeneity​

Reservoir heterogeneity​

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  The first example of reservoir heterogeneity is a formation of consistent mineralogy and grain characteristics that has various spatial patterns (for example bedding, foresets, syn-sedimentary faulting, or simply grain packing). ​
  
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  The second example has no spatial organization (it is massive) but has variable mineralogy and grain size and shape, i.e. it is a poorly sorted material.
  

Degree of heterogeneity ​

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  In attempting to quantify heterogeneity, several approaches considered. ​
  
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  To start defining the degree of heterogeneity in relation to the nature of the investigation; for example in a study of fluid flow, sedimentological structures may be of more importance than variation in mineralogy. ​
  
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  In contrast, in an investigation of downhole gamma ray variability the mineralogical variability (or strictly chemical variability of potassium, thorium and uranium) would be more relevant than any spatial variation.
  

Geological heterogeneities​
The common categories are: wellbore, interwell, and fieldwide scales of heterogeneity​
Heterogeneities at the wellbore ​

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  Affect matrix permeability, distribution of residual oil, directional flow of fluids, potential fluid-rock interactions, and formation damage.​
  
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  Elements of wellbore heterogeneities include the pore network (pores and pore throats), grain size and composition, grain packing, lamination and bedding styles, sedimentary structures, lithofacies, and vertical stratification sequences^.
  

Interwell scale heterogeneities​

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  Elements of interwell scale heterogeneity include lateral bedding geometries, styles, and continuity; systematic lateral and vertical textural patterns; and resultant variations in reservoir quality. ​
  
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  This scale of heterogeneity is probably the most difficult to quantify because wellbore data of the type previously described must be extrapolated to the interwell region. ​
  
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  In many instances, between-well correlations are difficult because lithofacies may not be continuous at interwell spacing. ​
  
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  Thus, interpretation must be guided by an understanding of depositional environments and facies, interpreted from core analysis and compared with modern environments or outcrop analogs where actual observations and measurements have been made
  

Fieldwide scale heterogeneities​

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  Elements of fieldwide variability include reservoir thickness, facies geometries and continuity, and bulk reservoir properties. ​
  
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  Depositional models, determined by geological description at the smaller scales, provide the main basis for interpreting fieldwide reservoir architecture. It is very important to describe the reservoir at this scale adequately because reservoirs, being complex depositional systems, are often compartmentalized, and separate compartments may not be in communication
  

Evaluating Heterogeneity​

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  Techniques are grouped into two themes: ​
  

1. 
   characterizing the variability in a dataset and; ​
   
2. 
   quantifying heterogeneity through heterogeneity measures.