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Case Log Tools: Everything You Need To Know

Case-Hole logging began with the gamma-ray log in the late 1930s and has continued to the present. Casing saves the hole from exterior contaminants and keeps the fluid from getting amalgamated. 

From evaluating new wells to optimizing reservoir management, case hole logs provide you with valuable data and assist in logging operations. With accurate information about the fluid content and reservoir rock, you can minimize any risks that may occur at the worksite.

Here are some of the case-logging tools that will help you to create and inspect well-defined wellbore:

Basic Cased-Hole Logging Tools

Generally, there are three types of logging tools for cased hole well services:

  • Saturation
  • Correlation
  • Porosity

The saturation device determines water saturation in the wellbore when porosity and salinity are known. The correlation instrument co-relates the open and cased-hole measurements. Likewise, the porosity device measures the porosity when you already know the Lithology. 

Some of the commonly used tools are:

Spectral Gamma Ray For Cased-Hole

This tool provides an insight into the mineral composition of the fluid. A gamma-ray spectrum resolves into three components of radiation, i.e., Potassium (K), Uranium (U), and Thorium (Th). 

The method uses 5-window spectroscopy to resolve the gamma-ray spectra into K, Th, and U curves. It provides data that is used to study features of sand or clay around the wellbore.

Saturation Log For Cased-Hole

Saturation tool such as the Pulsed Neutron gives porosity, sigma, and C/O measurements through just one trip into the wellbore. You can evaluate the water saturation level, borehole salinity, and water velocity inside the casing.

Formation Resistivity Of Cased-Hole

This tool inserts the current using the sidewall contact electrodes. Most of the current remains inside, and a minimal amount escapes the formation. This potential difference created by the escaped current is measured by the electrodes and is proportional to the conductivity.

It helps you to measure resistivity behind the casing in new, as well as the old wells. You can also locate the position of hydrocarbons and residual oil present in the formation. 

Cased-Hole Inspection Tools

After all the cased-hole logging processes are done, it is essential to conduct time to time inspection t check if the wellbore is in good condition. Some of the inspection tools are:

Electrical Potential Tool

The electrical potential tool in wireline services derives the direction and magnitude of the current that enters or departs through the casing. It can help you to locate the casing abnormalities like small pits and holes of size up to 5mm. 

Calipers For Casing

Case hole calipers are important tools for an efficient casing. They identify any variations or distortions in the diameter of the well casing. Depending upon their size, they have different applications. For example, a small cased-hole caliper is used for examining tube-casing. And, a large caliper is used to examine well-casing.

Electromagnetic Tool To Inspect Corrosion

The electromagnetic phase shift tool estimates the amount of metal used up in the tubing due to corrosion. It comes in two types, each with a different application. One measures the width of the remaining metal, and the other identifies defects in the walls of the casing. 

Ultrasonic Tool

It provides complete information about the thickness and radius of the casing. The process involves an ultrasonic transducer that points low at the level of cement evaluation. This way, it helps to shelter the whole thickness evaluation of the casing measurements. 

So, these are some of the tools used for logging and inspecting cased-holes. These tools are commonly deployed into wireline operations for abstracting valuable data while casing the new wellbore or inspecting any distortions in the existing one.

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