Presentation 5 - Archie's Law & Borehole Environment

7/30/2019 Presentation 5 - Archie's Law & Borehole Environment

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Archies law & Borehole

Environment

By:Saleem Q. Tunio

Faculty of Geoscience & Petroleum Engineering

Universiti Teknologi PETRONAS1TUNIO' 2012


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Formation fluid saturation

Formation fluid saturation is an important quantity:

It is necessary to determine the volume of fluids

(water and hydrocarbons) present;

It may give us some indication as to what will be

produced.

But

We often have to estimate several parametersthat are needed to make the saturationcalculation.

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(Source: Wkipedia)

Tortuosity factor,

The constant , called the tortuosity factor, cementation intercept,

lithology factoror, lithology coefficientis sometimes used. It is

meant to correct for variation in compaction, pore structure

and grain size

Cementation exponent,

The cementation exponent models how much the pore network

increases the resistivity, as the rock itself is assumed to be

non-conductive.

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(Source: Wkipedia)

Saturation exponent,

The saturation exponent usually is fixed to values close to 2. The

saturation exponent models the dependency on the presence

of non-conductive fluid (hydrocarbons) in the pore-space, and

is related to the wettability of the rock

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The Borehole Environment


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The Borehole Environment

Hole diameter (dh) The size of the borehole determined by the diameter of the drill

bit.

Drilling Mud Resistivity (Rm) Resistivity of the fluid used to drill a borehole and which

lubricates the bit, removes cuttings, maintains the walls of the borehole and maintains

borehole over formation pressure. Drilling mud consists of a variety of clay and other

materials in a fresh or saline aqueous solution and has a measurable resistivity.

Mudcake Resistivity (Rmc) Resistivity of the mineral residue formed by

accumulation of solid drilling mud components on the wellbore walls as the mud fluids

invade the formations penetrated by the borehole.

Mud Filtrate (Rmf) Resistivity of the liquid drilling mud components that infiltrate the

formation, leaving the mudcake on the walls of the borehole.


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Resistivity values for the drilling mud, mudcake, and mud filtrate are determined

during a full mud press and are recorded on a logs header.

Invaded Zone The zone which is invaded by mud filtrate. It consists of a flushed

zone (Rxo) and a transition or annulus zone (Ri). The flushed zone (Rxo) occurs close

mto the borehole where the mud filtrate has almost completely flushed out the

formations hydrocarbons and/or water. The transition or annulus zone (Ri), where a

formations fluids and mud filtrate are mixed, occurs between the flushed zone (Rxo)

and the univaded zone (Rt).

Uninvaded Zone (Rt) Pores in the univaded zone are uncontaminated by mud

filtrate; instead, they are saturated with formation fluids (water, oil and/or gas).


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Mud invasion


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Invasion - continued


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Presentation 5 - Archie's Law & Borehole Environment