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Upscaling petrophysical well log properties and summaries with GeolOil


GeolOil has a dedicated module to upscale petrophysical properties from LAS well logs. (Think of upscaling as a summary or equivalent value, similar to an average). The module can compute upscaled values for intensive and extensive properties, as well as other special cases.


An Intensive property, is a physical property for which its summary, upscaled or representative single value does not depend upon the sample size or overall volume. Classical examples of intensive properties are density, porosity, and water saturation. Extensive properties inherently depend upon the sample size or volume.


Examples of extensive properties are equivalent hydrocarbon column (depends upon the zone's thickness: the thicker, the larger), and bulk volume of water in a zone. Likewise, reservoir properties like net-reservoir thickness, net-sand thickness, and net-pay can be considered as special cases of extensive upscaling computed on the summation of indicator lithotypes. Generally speaking, average types are related to intensive upscaling, and totals or nets are related to extensive upscaling.


GeolOil allows to define an unlimited amount of upscaling types. Each upscaling will have its own combination of computation type, lithology or facies definition, the zones, layers or vertical cells where it will be computed, the resulting upscaled values or summaries, as well as the creation of a staircase style log curve to display and compare the results against the original log curve. Typical reservoir properties computed by GeolOil are:

  1. Net reservoir thickness.
  2. Net-Pay thickness.
  3. Maximum true vertical depth continuous-pay thickness. (A must have for heavy oil and SAGD technology screening).
  4. Isochore Thickness.
  5. Net to Gross Ratio.
  6. Coalescence between adjacent geological layers.
  7. Porosity in reservoir rocks.
  8. Porosity in pay rocks.
  9. Upscaled porosity in whole layers gross rocks.
  10. Water Saturation.
  11. Clayness and shaliness of sandstones.
  12. Formation Water Resistivity by the Hingle algorithm.


The figure below shows the main upscaling list panel, with SW upscaling highlighted


GeolOil panel of upscaling listing.



The figure below shows the upscaling processing panel. Notice that an intensive upscaling was specified for SW.


GeolOil panel of upscaling processing algoritms.



GeolOil allows to define lithology types in several ways. There can be available indicator flag curves for lithologies and facies, or the user can define a lithology through a series of filters and cutoffs. For instance, gross rocks should not be filtered, so the whole column should be accepted. Likewise, lithologies like clean sandstones should be filtered by a low Gamma Ray curve signal (for example, GR below 65 units API) and photoelectric factor of around 1.9 B/E units. Limestones should be filtered by PEF curve values around 5 B/E units, and so forth for other lithologies.


The processing panel should have filled as much as possible, all the relevant curve numbers for the requested upscaling computation. For example, if the upscaling of water saturation on gross rocks is desired, the user must specify the curve numbers both for porosity and water saturation (since correct SW upscaling depends not only on SW itself, but also on its porosity). Also, the target property (row item 0) must has the same water saturation curve number. This is the way GeolOil will know to use the right equations to upscale water saturation.


Treatment of outliers can be specified in the processing panel. For instance, if the user needs to upscale porosity, what is the best processing treatment that has to be done for negative values?. Clearly, negative values for porosity should not be allowed to enter into the computations. A negative outlier value might be rejected (discarded and thrown away), or trimmed (converted to a value like 0.0). The user also has options to discard unreliable depth zone intervals.



The figure below shows the curves and cutoffs filtering panel.


GeolOil panel of upscaling curves and cutoffs filters.



The figure below shows the zonation panel, where curve outputs can be defined and additional zone filters applied


GeolOil zonation panel.



The figure below shows the results panel, where upscaled values are tabulated for each layer or cell zone


GeolOil panel of upscaling results in tabular view.



The figure below shows the plot of an upscaled SW curve (UPS_SW), shown in black with a staircase steps pattern


GeolOil plot of an uspcaled staircase steps style SW curve.





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