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How can i calculate saturation of OBM filtrate for Wet and HC zones(SOBM =Sxoo)

How can i also extract the saturation of mud filtrate from the invaded Bulk Density Relation for both original wet and HC sand units.

Kindly send any ideas here.

You can estimate the saturation of oil filtrate in the invaded zone Sof in a well drilled with Oil Base Mud, using the following equations:
In a water bearing zone:
Sof = 1 – Sxo
Where, Sxo is the water saturation in the Invaded Zone.

In an oil (or hydrocarbon) bearing zone:
Sxo + Sh + Sof = Sw + Sh
Sof = Sw - Sxo
Where, Sw is the water saturation in the virgin (uninvaded) zone, Sxo is the water saturation in the invaded zone and the Sh is the original formation oil saturation (which is the same for the virgin zone as well as the invaded zone).
The water saturation Sxo in the invaded zone can be estimated using one of the following logging tools:
1) Dielectric Logging tool to compute water-filled porosity in the invaded zone.
2) Pulsed Neutron Logging tool, either using Sigma (salinity dependence) or Carbon-Oxygen ratio to derive Sxo.
3) Nuclear Magnetic Resonance logging tool, if there is an appreciable difference in the viscosity of the OBM filtrate and the formation oil.
These tools are required because a micro-resistivity log such as MSFL cannot be run in a well drilled with OBM.

Thank you for the reply..let me go and study it in detail.But in a scenario, that i have only the different depth reading resistivity logs,do you imply that only a Water-based mud would have been used.

I also asked about; How i could also extract the saturation of mud filtrate from the invaded Bulk Density Relation for both original wet and HC sand units.?

Thanks

No, based only the resistivity logs with different depths of investigation, you cannot assume that water base mud was used. It depends on what type of resistivity tool was run.
In an Oil Base Mud environment, you can only use an Array Induction type of tool. You cannot run a laterolog type of tool, including a mico-resistivity tool like MSFL cannot be used.
If a laterolog log resistivity log together with an MSFL log have been run, the well was definitely drilled with Water Base Mud.
On the other hand, an Array Induction Resistivity tool could have been run in either WBM or OBM environment.
An Array Induction type of resistivity tool does not provide you with an Rxo (resistivity of the invaded zone) log, although sometimes the shallowest induction resistivity log has been used as an approximate equivalent of Rxo. This may or may not be true, depending on the invasion profile.

As to your second question of deriving the Sof (oil filtrate saturation in the invaded zone) using the bulk density log, here are my comments.
You need to make some assumptions if you want to use the density log, which is a shallow reading device to compute Sof in the invaded zone for a water bearing zone.
You need to know or assume the density of the OBM filtrate under downhole conditions, the reservoir must also be relatively clean (clay free). Otherwise, you will have to take into account the clay effect on the density log in the volumetric equation.
However, if the reservoir is hydrocarbon bearing, it becomes more complicated. You need to know the density of the formation oil also to solve the volumetric equation based on the density log. It becomes more complex to solve the equation and you will need some other logs to do that.