How does porosity affect resistivity?

How does porosity affect resistivity?

The resistivity of rocks has a tendency to decrease with increasing porosity. The resistivity of the rocks increases with the increase in the pore fluid resistivity, regardless of the rock types.

What is formation resistivity factor?

The formation resistivity factor of a porous medium is a valuable concept in the area of formation evaluation. It has been denned as the ratio of the resistivity of the medium when completely saturated with a conducting fluid to the resistivity of the saturating fluid.

What is formation porosity?

Gas porosity is the fraction of a rock or sediment filled with a gas. Determining the true porosity of a gas filled formation has always been a problem in the oil industry. Well logging interpretation of the amount of hydrocarbon in the pore space of a formation, relies on the fluid being oil.

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What is Archie’s equation used for?

Based on Adebayo et al (2014), the first application of Archie’s equation is used to determine the formation factor F, where the formation factor of rock is defined as the ratio of rock resistivity when 100\% saturated by brine water, Ro, to the brine water resistivity Rw (Bassiouni 1994, Hamada et al2012).

What is resistivity in fluid?

Resistivity is a fundamental material property which represents how strongly a material opposes the flow of electric current.

What is resistivity in oil and gas?

1. n. [Formation Evaluation] The ability of a material to resist electrical conduction. It is the inverse of conductivity and is measured in ohm-m. The resistivity is a property of the material, whereas the resistance also depends on the volume measured.

How is porosity of formation calculated?

The first equation uses the total volume and the volume of the void. Porosity = (Volume of Voids / Total Volume) x 100\%. The second equation uses the total volume and the volume of the solid. Porosity = ( ( Total Volume – Volume of the Solid ) / Total Volume ) x 100\%.

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What is porosity in geology?

More specifically, porosity of a rock is a measure of its ability to hold a fluid. Mathematically, it is the open space in a rock divided by the total rock volume (solid and space). A rock may be extremely porous, but if the pores are not connected, it will have no permeability.

What do resistivity logs measure?

Resistivity logging is a method of well logging that works by characterizing the rock or sediment in a borehole by measuring its electrical resistivity. Resistivity is a fundamental material property which represents how strongly a material opposes the flow of electric current.

How do you find effective porosity?

Total porosity minus clay-bound water (CBW). Log effective porosity. In essence, total porosity minus shale water, where solid minerals and the volume of shale (Vsh) constitute the matrix (non-effective porosity) and the remaining volume constitutes the effective porosity.

What is resistivity solution?

Answer: Resistivity of any solution : When current flow in the solution through two electrodes resistance is proportional to length and inversely proportional to cross sectional area A. Thus, Resistivity of any solution is the resistance of one cm cube.

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What is the formation resistivity factor?

Formation resistivity factor is the ratio of the resistivity of 100\% water saturated rock to the resistivity of the water with which it is saturated. F = Ro / RW .The resistivity

Why is resistivity so difficult to measure?

Resistivity is the one of the most difficult formation parameters to measure accurately because of the complex changes that occur during and after drilling a well and that may still be occurring during logging.

How do you calculate the resistivity of a hydrocarbon formation?

The overall resistivity of the formation containing a hydrocarbon (Rt) is obtained from one of the long-spaced (deep reading) logs, and Rw is obtained from the SP log or from analysis of the formation water [ 28 ]: (10.27) S w = F r R w / R t 1 / n − V s h Sw = Formation water (brine) saturation, Fr = Formation resistivity factor = a / φm,

What factors affect the resistivity of a particulate system?

Sorting and Packing (in particulate system) The last six factors have effect through the influence on the conduction path. Confinement or overburden pressure may cause a significant increase in resistivity by blocking of some conduction paths and reduction in the cross sections which are available for flow.