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Water saturation distribution in a reservoir (view source)
Revision as of 20:49, 31 January 2014
, 20:49, 31 January 2014Initial import
{{publication
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Predicting reservoir system quality and performance
| frompg = 9-1
| topg = 9-156
| author = Dan J. Hartmann, Edward A. Beaumont
| link = http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
The distribution of water saturation values within a reservoir depends on the height above free water, hydrocarbon type, pore throat-size distribution, and pore geometry. Mapping S<sub>w</sub> distribution in a reservoir helps us predict trap boundaries.
==Bvw==
Bulk volume water (BVW) equals Φ × S<sub>w</sub>. In zones with the same pore type and geometry, BVW is a function of the height above the [[free water level]]. Above the transition zone, BVW is fairly constant. Below the transition zone, BVW is variable.
A Buckles plot is a plot of S<sub>w</sub> vs. [[porosity]]. Contours of equal BVW are drawn on the plot.
* Points plot on a hyperbolic BVW line where the formation is near immobile water if the points come from a reservoir with consistent pore type and pore geometry.
* Points scatter on a Buckles plot where the formation falls below the top of the transition zone.
The figure below shows how a Buckles plot relates to [[capillary pressure]], fluid distribution, and fluid recovery in a reservoir.
[[file:predicting-reservoir-system-quality-and-performance_fig9-40.png|thumb|{{figure number|9-40}}See text for explanation.]]
==Limitations of BVW==
BVW and Buckles plots can be confusing in interbedded lithologies or in areas where facies changes occur because of changing pore types.
==S<sub>w</sub>—depth plots==
S<sub>w</sub>–depth plots are simple plots of S<sub>w</sub> vs. depth. They illustrate how S<sub>w</sub> varies within a hydrocarbon-bearing zone. Variations reflect different pore types and/or height above free water. An S<sub>w</sub>–depth plot can be used to delineate three things:
* Transition and waste zones
* Flow units
* Containers
Individual plots can [[be prepared]] for wells along dip and strike and correlated to show S<sub>w</sub> changes across a reservoir or field. Below is a hypothetical example of an S<sub>w</sub>–depth plot with estimated S<sub>w</sub> distribution curves for several flow units for a hydrocarbon-bearing zone in a well.
[[file:predicting-reservoir-system-quality-and-performance_fig9-41.png|thumb|{{figure number|9-41}}See text for explanation.]]
==Height–s<sub>w</sub>–pore type diagram==
The empirical ternary diagram below is handy for estimating either height above free water, port type (r<sub>35</sub>), or S<sub>w</sub> for a flow unit when the other two variables are known. For example, if S<sub>w</sub> for a flow unit is 20% and the pore type is macro with a port size of approximately 3μ, then the height above free water for the flow unit is approximately [[length::100 ft]]. Assumptions for the diagram include 30°API gravity oil, saltwater formation water, and water wet.
[[file:predicting-reservoir-system-quality-and-performance_fig9-42.png|thumb|{{figure number|9-42}}See text for explanation.]]
==See also==
* [[Interpreting water saturation]]
* [[Interpreting hydrocarbon shows]]
* [[Predicting hydrocarbon recovery]]
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Predicting reservoir system quality and performance]]
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Predicting reservoir system quality and performance
| frompg = 9-1
| topg = 9-156
| author = Dan J. Hartmann, Edward A. Beaumont
| link = http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
The distribution of water saturation values within a reservoir depends on the height above free water, hydrocarbon type, pore throat-size distribution, and pore geometry. Mapping S<sub>w</sub> distribution in a reservoir helps us predict trap boundaries.
==Bvw==
Bulk volume water (BVW) equals Φ × S<sub>w</sub>. In zones with the same pore type and geometry, BVW is a function of the height above the [[free water level]]. Above the transition zone, BVW is fairly constant. Below the transition zone, BVW is variable.
A Buckles plot is a plot of S<sub>w</sub> vs. [[porosity]]. Contours of equal BVW are drawn on the plot.
* Points plot on a hyperbolic BVW line where the formation is near immobile water if the points come from a reservoir with consistent pore type and pore geometry.
* Points scatter on a Buckles plot where the formation falls below the top of the transition zone.
The figure below shows how a Buckles plot relates to [[capillary pressure]], fluid distribution, and fluid recovery in a reservoir.
[[file:predicting-reservoir-system-quality-and-performance_fig9-40.png|thumb|{{figure number|9-40}}See text for explanation.]]
==Limitations of BVW==
BVW and Buckles plots can be confusing in interbedded lithologies or in areas where facies changes occur because of changing pore types.
==S<sub>w</sub>—depth plots==
S<sub>w</sub>–depth plots are simple plots of S<sub>w</sub> vs. depth. They illustrate how S<sub>w</sub> varies within a hydrocarbon-bearing zone. Variations reflect different pore types and/or height above free water. An S<sub>w</sub>–depth plot can be used to delineate three things:
* Transition and waste zones
* Flow units
* Containers
Individual plots can [[be prepared]] for wells along dip and strike and correlated to show S<sub>w</sub> changes across a reservoir or field. Below is a hypothetical example of an S<sub>w</sub>–depth plot with estimated S<sub>w</sub> distribution curves for several flow units for a hydrocarbon-bearing zone in a well.
[[file:predicting-reservoir-system-quality-and-performance_fig9-41.png|thumb|{{figure number|9-41}}See text for explanation.]]
==Height–s<sub>w</sub>–pore type diagram==
The empirical ternary diagram below is handy for estimating either height above free water, port type (r<sub>35</sub>), or S<sub>w</sub> for a flow unit when the other two variables are known. For example, if S<sub>w</sub> for a flow unit is 20% and the pore type is macro with a port size of approximately 3μ, then the height above free water for the flow unit is approximately [[length::100 ft]]. Assumptions for the diagram include 30°API gravity oil, saltwater formation water, and water wet.
[[file:predicting-reservoir-system-quality-and-performance_fig9-42.png|thumb|{{figure number|9-42}}See text for explanation.]]
==See also==
* [[Interpreting water saturation]]
* [[Interpreting hydrocarbon shows]]
* [[Predicting hydrocarbon recovery]]
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Predicting reservoir system quality and performance]]