Method for quickly detecting saturation exponent n in laboratory

Abstract

The invention provides a method (three-point method) for quickly detecting a saturation exponent n in a laboratory. The method realizes the following three particular targets: (1) on the premise that capillary force and resistivity balance are ensured, the water saturation and resistivity of a core can be measured accurately; (2) the experiment testing period is shortened to 2 weeks from 2 months; and (3) whether the relationship between the resistance increase and the water saturation of rock conforms to the Archie relationship or not can be judged, and the saturation exponent n is given if the relationship between the resistance increase and the water saturation of rock conforms to the Archie relationship. The three-point method can efficiently detect reservoir saturation without risk.

Description

technical field [0001] The invention relates to a method for measuring rock electrical parameters in the field of exploration geophysics, in particular to a method for quickly measuring reservoir saturation index n in a laboratory. Background technique [0002] Archie established the resistivity increase rate (R I ) and water saturation (Sw) and formation factors (F F ) and porosity (φ), namely the Archie formula: [0003] R I =Rt / Ro=1 / S n W (1) [0004] f F = R 0 / Rw=1 / φ m (2) [0005] In the formula, Rt is the true resistivity of the core saturated with formation water and hydrocarbons, Ro is the resistivity of fully water-bearing sandstone, Rw is the resistivity of formation water, m is the cementation index, and n is the saturation index. Archie's formula establishes a link between porosity measurement and resistivity measurement, and constitutes the theoretical basis for quantitatively evaluating the original oil (gas) saturation of "pure formations" u...

AI Technical Summary

Problems solved by technology

This recommended practice has the following problems: due to consideration of the capillary force and resistivity balance after saturation changes, it usually needs to be stable for 7-10 days at each displacement working pressure point (corresponding to the water saturation of the core). For the resistivity of 5-7 water saturation states, it takes about 2 months to complete the experimental measurement of the saturation index n, and the test period of the experiment is long

However, due to wettability, pore structure, etc., the relationship between rock resistance increase rate and water saturation may not obey the Archie relationship, that is, the image 3 The non-Archie relationship shown

There are risks in using the "two-point method" when it is not possible to know in advance whether the Archie formula will apply

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