CHL

CHL: Deciphering the Language of Oil & Gas - Cased Hole Logs

In the world of oil and gas exploration and production, a vast and often complex vocabulary is used to describe the various processes, equipment, and data involved. One such term, CHL, stands for Cased Hole Log. This term, frequently encountered in industry reports and discussions, signifies a crucial tool in the post-drilling phase of oil and gas operations.

What are Cased Hole Logs?

Cased hole logs are specialized surveys conducted after a well has been drilled and cased. These logs, often carried out using specialized logging tools lowered into the well, provide detailed information about the formation surrounding the casing, the condition of the casing itself, and the presence and characteristics of hydrocarbons.

Why are they important?

Understanding the formations and potential hydrocarbon reservoirs after drilling is essential for effective production. Cased hole logs offer valuable insights that enable operators to:

Identify hydrocarbon-bearing zones: These logs reveal the location and characteristics of productive layers within the formation, aiding in the placement of completion equipment and maximizing oil and gas recovery.
Assess reservoir properties: Data from these logs helps determine reservoir thickness, porosity, permeability, and fluid saturation. This information is crucial for reservoir characterization and modeling.
Monitor well performance: Regular cased hole logs can track changes in fluid production, pressure, and reservoir behavior over time, enabling efficient production management and optimizing well performance.
Evaluate casing integrity: These logs can identify any potential damage or corrosion to the casing, ensuring its integrity and preventing potential leaks or environmental issues.
Plan future interventions: Cased hole logs provide valuable information for planning future workovers, stimulations, or other well interventions to maximize production and address any challenges encountered in the well.

Different types of Cased Hole Logs:

There are various types of cased hole logs, each serving a specific purpose:

Nuclear logs: These logs use radioactive sources and detectors to measure properties like density, porosity, and lithology.
Acoustic logs: These logs utilize sound waves to assess casing thickness, cement bond quality, and formation properties.
Electrical logs: These logs measure the electrical conductivity of the formation and can identify hydrocarbons, saltwater, and other fluids.
Production logs: These logs measure the flow rates, pressures, and other parameters related to fluid production from the well.

Benefits of Cased Hole Logging:

Improved reservoir understanding: CHL provides comprehensive data for better reservoir characterization and production optimization.
Efficient well management: Regular monitoring through Cased Hole Logs helps in maximizing production and identifying any potential problems.
Safety and environmental protection: By assessing casing integrity, CHL helps prevent leaks and minimize environmental risks.

Conclusion:

Cased hole logs play a vital role in the efficient and sustainable production of oil and gas. They provide valuable information about the reservoir, well performance, and casing integrity, allowing operators to make informed decisions for maximizing production and minimizing risks. Understanding the term "CHL" and its significance is essential for navigating the complex world of oil and gas operations.

Test Your Knowledge

Quiz: Cased Hole Logs (CHL)

Instructions: Choose the best answer for each question.

1. What does CHL stand for?

a) Casing Hole Logging b) Cased Hole Logging c) Completed Hole Logging d) Core Hole Logging

Answer

b) Cased Hole Logging

2. When are Cased Hole Logs typically performed?

a) Before drilling a well b) During drilling a well c) After a well has been drilled and cased d) During well completion

Answer

c) After a well has been drilled and cased

3. What is NOT a benefit of using Cased Hole Logs?

a) Improved reservoir understanding b) Efficient well management c) Lower drilling costs d) Safety and environmental protection

Answer

c) Lower drilling costs

4. Which type of Cased Hole Log uses sound waves to assess casing thickness?

a) Nuclear logs b) Acoustic logs c) Electrical logs d) Production logs

Answer

b) Acoustic logs

5. What information can Cased Hole Logs provide about a well?

a) Formation properties and hydrocarbon presence b) Casing integrity and well performance c) Potential future interventions d) All of the above

Answer

d) All of the above

Exercise: CHL Application

Scenario: An oil well has been drilled and cased. The operator needs to determine the best location for a new production zone. They have decided to run a Cased Hole Log to assess the reservoir properties.

Task: Based on the information provided below, explain how the Cased Hole Log data can help the operator make an informed decision about the production zone:

Nuclear logs: Show high porosity and permeability in a specific zone between 3,000 and 3,200 feet.
Acoustic logs: Indicate good cement bond quality around the casing.
Electrical logs: Identify a hydrocarbon-bearing zone within the same depth range as the high porosity and permeability.

Write your explanation in a short paragraph.

Exercice Correction

The combined data from the Cased Hole Logs suggests that the zone between 3,000 and 3,200 feet is a promising location for a new production zone. The nuclear logs indicate favorable reservoir properties with high porosity and permeability, which are essential for good hydrocarbon flow. The acoustic logs ensure the casing integrity with good cement bonding, preventing potential leaks and ensuring safe production. Lastly, the electrical logs confirm the presence of hydrocarbons within this zone, further validating its potential as a productive zone. This comprehensive data allows the operator to confidently choose this location for their new production zone.

Books

"Well Logging and Formation Evaluation" by Schlumberger. This classic book provides a comprehensive overview of well logging techniques, including cased hole logging.
"Petroleum Engineering Handbook" by William J. D. van Rensburg. This comprehensive handbook covers various aspects of petroleum engineering, including well logging and formation evaluation.
"The Log Analyst" by Society of Petrophysicists and Well Log Analysts (SPWLA). A periodical publication with articles related to well logging and formation evaluation, including cased hole logs.

Articles

"Cased Hole Logging: A Comprehensive Guide" by Oilfield Technology Magazine. This article provides an overview of cased hole logging techniques and applications.
"Cased Hole Logging for Production Optimization" by SPE Journal. This article discusses the use of cased hole logs for maximizing well performance and production.
"Cased Hole Logs: A Powerful Tool for Reservoir Characterization" by Petroleum Technology Quarterly. This article explores the use of cased hole logs for understanding reservoir properties and distribution.

Online Resources

Schlumberger's website: Schlumberger is a leading provider of oilfield services, including well logging. Their website offers a wealth of information on cased hole logging techniques and applications.
SPWLA website: The Society of Petrophysicists and Well Log Analysts provides resources and information on well logging and formation evaluation.
Oilfield Glossary: This website provides definitions and explanations of various oil and gas terms, including "Cased Hole Log".

Search Tips

Combine keywords: Use keywords like "cased hole logs," "well logging," "formation evaluation," and "production optimization" together in your search queries.
Specify search parameters: Use "site:schlumberger.com" or "site:spwla.org" to narrow your search to specific websites.
Look for PDF files: Many technical articles and presentations on cased hole logging are available as PDF files.