Application of geophysical logging curves

- Jun 28, 2019-

Application of geophysical logging curves


Electrical Survey

Parameter

Curve feature

Application

Interference

Conditions

Gradient electrode system logging

Apparent resistivity

1. The bottom gradient has a maximum value at the bottom of the high resistance layer and a minimum value at the top.

2. The top gradient has a maximum value at the top of the high resistance layer and a minimum value at the bottom.

1. Determine the resistivity of the stratum.

 

2. Determine lithology based on stratum resistivity.

 

3. Layering

1. This layer shielding effect.

 

2.High-resistance neighboring layer shielding effect

1.Light cement slurry

2.Oil-based mud

3.Salty cement slurry

4.Not used in cased wells

Potential electrode system logging

Apparent resistivity

The curve is symmetric with the center of the formation, with high values on the high-resistance layer, low values on the low-resistance layer, and the rock interface at the half-point of the curve.

1. Determine the resistivity of the stratum.

  

2. Determine lithology according to the stratum resistivity

 

3. Layering with half width

Few Interference

1.Light cement slurry

 

2.Not used for wells that have been casing

Microelectrode logging

Resistivity of two different parts in the well

1. The curve on the high resistance layer has a high value, and the curve on the low resistance layer has a low value.

 

2. There is a difference in the osmotic layer, and there is no amplitude difference on the non-permeable layer.

 

3. The half-width corresponds to the rock formation interface.

1. Determine the permeability of the rock stratum. If the other conditions are the same, the difference is large and the permeability is good, otherwise it is small.

 

2. Especially for stratification.

 

3. Determine lithology, apparent resistivity, and wellbore development.

1. Poor mineralization refers to the degree of mineralization of mud filtrate in formation water salinity. In the same sand layer, the degree of mineralization is greatly different.

 

2. The difference in the amplitude of the limestone section is false.

 

3. Some gray mudstones exhibit anomalous negative anomalies with micro-gradients greater than micropotentials.

1.Light cement slurry

 

2.Not used for wells that have been casing