**WELLOG ****
WATER SATURATION**

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**REVISED ****08****-08-2007**

**© 2006-2007 ****WELLOG**

**All Rights Reserved**

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**Determination of water saturation is the ultimate objective in oil
well log analysis. **

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**Basic determinations have historically been made using the
following methods:**

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**Keep in mind – many factors influence the bottom line in well log
interpretation and log analysis. These equations only form a starting point –
not the final answer!**

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**
Sw
= (Ro/Rt) ^{1}^{/2}**

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**
Sw
= (F * Rw/Rt) ^{1}^{/2}**

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**
Sw
= (1/ ****F**^{m}** * Rw/Rt) ^{1}^{/2}**

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**SHALE CORRECTION:**

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**Improved Water saturation results are obtained using corrected
porosity. Porosity may need correction for shale and other out of matrix
errors.**

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**
Sw
= ((.81 * Rw/Rt) ^{1}^{/2} – (Vsh
* Rw /.4 Rsh))/**

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**
Sw
= ((a * Rw)/(**** (F****e/(1-Vsh)) ^{m } * (1-Vsh)/(1/Rt – Vsh/Rsh)))^{1/n}
Laminar
Equation **

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**
Sw
= ((a * Rw)
* (1/Rt – Vsh/Rsh)/ (**** (F****e/(1-Vsh)) ^{m
}))^{1/n}
Parabolic
Equation**

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**Sw
= ((a * Rw)
* (1/Rt – Vsh/Rc)/ (**** (F****e/(1-Vsh)) ^{m
}))^{1/n}
Hossin
Equation **

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**
Sw
= (1/**** F****sd) * (Rw/Rt) ^{1}^{/2} – Vsh * (Rw/Rc)^{1/2} Doll Equation**

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** Sw = Click
for (Simandoux) Simandoux
Equation**

**WATER SATURATION NOMOGRAPH:**

**A nomograph
can provide a quick way to analyze log data and determine water saturation.**

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**Barrels of oil determination as follows:**

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**Oil Reserve
(Recoverable oil) bbls
= (7758.4 * ****F ***** (1-Sw) * Recovery
factor * h * A/FVF**

**FVF = Formation Volume
Factor**

**Recovery Factor:**

**Calculation of Recovery Factor value is complex. Recovery factor
will vary with the producing energy mechanism, hydrocarbon viscosity and
geometry, formation permeability, and pore geometry. Recovery factor may also
be considered in terms of both recovery by primary
production and by total recovery after secondary recovery operations. As a rule
of thumb one may use a recovery factor of 30 percent for solution gas drive
reservoirs, 50 percent for gas cap drive reservoirs, and 70 percent for water
drive reservoirs.**

**Formation volume factor:**

**Formation volume factor is the space in the producing formation
occupied by one barrel of stock tank oil. FVF is generally estimated by adding
.05 for each 100 cubic feet of gas produced with each barrel of oil to a base
value of 1.05. A detailed study of subsurface temperature and pressure, gas and
crude oil gravity will result in a more accurate calculation of formation
volume factor.**

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**UNCERTAINTY:**

**All measurements come with a certain amount of uncertainty. Learn
more about how to quantify uncertainty.**

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**If you have questions – ask ****WELLOG****!**

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**Contact ****WELLOG**** at info@wellog.com**

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