Calculate Resistivity Porosity - Flushed Zone - Residual Hydrocarbons Correction

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Resistivity derived porosity - Flushed Zone - Residual Hydrocarbons Correction

For the calculation of resistivity derived porosity at the flushed zone, there are cases where a residual hydrocarbons correction needs to be made. In this case, water saturation of an uninvaded zone and the saturation exponent valuesneed to values must be known. The expression is summarized as the following:

Where:
• ɸ= porosity
• a= tortuosity factor
• Sw= water saturation of the uninvaded zone
• m= cementation exponent
• n= saturation exponent
• Rmf= resistivity of the mud filtrate at formation temperature
• Rxo= shallow resistivity from a very shallow reading device such as lateolog-8, microspherically focused log, or microlaterolog

Calculate Resistivity Porosity (ɸ) - Flushed Zone- Residual Hydrocarbons Correction
a:		Rmf: ohm-m
Rxo: ohm-m		Sw: Decimal
n:		m:

Made by Henry Herrera

Calculate Resistivity Porosity - Flushed Zone Rxo

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Resistivity derived porosity (ɸ) - Flushed Zone Rxo

At the flushe zone, resistivity derived porosity can also be calculated. In this case, resistivity of the mud filtrate at formation temperature must be know and the shallow resistivity from a very shallow reading device, besides the tortuosity and cementation exponent values. The equation is expressed the following way:

Where:
• ɸ= porosity
• a= tortuosity factor
• m= cementation exponent
• Rmf= resistivity of the mud filtrate at formation temperature
• Rxo= shallow resistivity from a very shallow reading device such as lateolog-8, microspherically focused log, or microlaterolog

Calculate Porosity (ɸ)
a:		Rmf: ohm-m
Rxo: ohm-m		m:

Made by Henry Herrera

Calculate Resistivity Porosity - Sw = 1

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Resistivity derived porosity (Sw= 1)

In water bearing zones, where water saturation equals a 100% (Sw= 1), Archie's equation for resistivity derived porosity, is shorten because it is not neccesary to use water saturation because equals 1, neither the saturation exponent, and it is simplified as the following expression:

Where:
• ɸ= porosity
• Rw= resistivity of formation water at formation temperature
• Rt= true formation resistivity (i.e., deep induction or deep laterolog corrected for invasion)
• a= tortuosity factor
• m= cementation exponent

Calculate Resistivity derived porosity (ɸ) - Sw = 1
a:		Rw: ohm-m
Rt: ohm-m		m:

Made by Henry Herrera

Calculate Resistivity Porosity

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List of equations assignment

Resistivity derived porosity (resistivity porosity)

Starting from the well known Archie's equation, regularly known better for water resistivity calculations, it is also used for the resistivity derived porosity. This equation includes the values of tortuosity factor, formation and water resistivities, water saturation, and saturation and cementation exponents, and the expression is the following:

Where:
• ɸ= porosity
• Sw= water saturation of the uninvaded zone
• Rw= resistivity of formation water at formation temperature
• Rt= true formation resistivity (i.e., deep induction or deep laterolog corrected for invasion)
• a= tortuosity factor
• m= cementation exponent
• n= saturation exponent

Calculate Resistivity derived Porosity (ɸ)
a:		Rw: ohm-m
Rt: ohm-m		Sw: Decimal
n:		m:

Made by Henry Herrera