Well Logging

Summary

This video explains the process and purpose of well logging, a technique used to record physical properties of soil at different depths in a borehole. It highlights the significance of well logging in determining soil structure, locating aquifers, and guiding groundwater exploitation. The video details various logging methods, including neutron, sonic, density, and electrical logging, each of which measures different physical parameters like porosity, sonic velocity, density, and resistivity. The tutorial also explains the equipment used, including tools for capturing data, and demonstrates the importance of well logging in optimizing borehole construction and water extraction.

Takeaways

• 😀 Well logging is the process of recording physical parameters of the soil at various depths in a borehole using specialized tools.
• 😀 The primary purpose of well logging is to understand the geological layers and locate aquifers for groundwater extraction.
• 😀 Well logging tools are lowered into a borehole, and data is captured and recorded, including soil structure and water-bearing layers.
• 😀 Well logging helps determine the appropriate placement of well screens in boreholes for effective groundwater extraction.
• 😀 The main physical parameters measured during well logging include electrical potential, resistivity, sound wave velocity, rock density, and energy absorption by rocks.
• 😀 Well logging can be done using different methods, such as Open Hole Logging (before casing is installed) and Cased Hole Logging (after casing is installed).
• 😀 Open Hole Logging allows the use of all well logging techniques, while Cased Hole Logging is limited to specific logs like Gamma Ray (GR) and Cement Bond Log (CBL).
• 😀 Neutron Logs measure neutron loss upon collision with formations, providing insights into rock porosity, such as in sandstone or limestone.
• 😀 Sonic Logs measure the travel time of sound waves through rock layers, helping to determine rock characteristics and porosity.
• 😀 Density Logs use gamma rays to measure the electron density of rock formations, indicating the rock's density, which can reveal useful geological information.
• 😀 Electrical Logs measure the resistivity and potential difference of rocks to help identify rock types (like clay or sand) and their water content.

Q & A

What is the purpose of well logging?

The purpose of well logging is to detect physical parameters of the soil at different depths in a borehole by inserting a tool into the well and recording the results.

How is well logging performed?

Well logging is performed by lowering a tool into a borehole, connecting it to a cable, which is then linked to a recording machine that tracks various physical parameters of the soil at each depth.

What kind of physical parameters of the soil can be detected through well logging?

Well logging can detect several physical parameters including electrical potential of rocks, resistivity, seismic wave velocity, formation density, and energy absorption of rocks.

Why is knowing the aquifer layer important in well logging?

Knowing the location of the aquifer layer is crucial for groundwater exploitation, as it helps in determining the optimal locations for placing pipe screens in the borehole.

What are the two types of well logging methods based on the casing presence?

If the casing is not installed, open hole logging is used, allowing for all types of well logging methods. If the casing is installed, only certain methods like caliper logs, NMR, and CBL can be performed, known as cased hole logging.

What is the function of the screen pipe in well logging?

The screen pipe in well logging is used to filter water from the aquifer layer and prevent sediment from entering the well, ensuring proper water extraction for use.

What is neutron log used for in well logging?

Neutron log is used to measure neutron loss caused by collisions with rocks at each depth, providing information on the porosity of the formation in percentage.

What is the Sonic log and how does it work?

The Sonic log measures the travel time of sound waves through the rock formations. The tool sends out signals from both ends of the device, and the time it takes for the signals to return is recorded to analyze the rock properties.

What is density log and what does it measure?

The density log measures the electron density of a formation by shooting gamma rays into the formation. The amount of energy lost indicates the density of the rocks, typically expressed in grams per cubic centimeter.

What is electrical logging and how is it conducted?

Electrical logging involves injecting electricity into the ground at various depths and measuring the potential difference and resistivity. This helps to identify the type of rocks and determine the suitability for groundwater extraction.