Formation Evaluation

Test Your Knowledge

Formation Evaluation Quiz

Instructions: Choose the best answer for each question.

1. What is the primary purpose of formation evaluation?

a) To identify the location of oil and gas reservoirs. b) To analyze the characteristics and properties of rock formations. c) To extract oil and gas from the reservoir. d) To design and build drilling rigs.

2. What is the term for the process of sending specialized probes down a wellbore to measure formation properties?

a) Well logging b) Reservoir simulation c) Geological interpretation d) Seismic analysis

3. Which of the following is NOT a parameter measured by logging tools?

a) Porosity b) Permeability c) Fluid saturation d) Wind speed

4. What type of log measures the natural radioactivity of the formation?

a) Resistivity log b) Sonic log c) Gamma ray log d) Density log

5. Formation evaluation data helps to determine all of the following EXCEPT:

a) The volume of hydrocarbons present b) The best location for drilling wells c) The profitability of a reservoir d) The weather conditions at the drilling site

Formation Evaluation Exercise

Scenario:

You are a geologist working on an oil exploration project. You have collected data from a well log that shows the following:

• Porosity: 20%
• Permeability: 10 millidarcies
• Fluid Saturation: 80% oil, 20% water

Task:

Based on this data, analyze the potential of this formation as a viable oil reservoir. Consider factors like porosity, permeability, and fluid saturation.

Instructions:

1. Briefly describe the characteristics of a good oil reservoir.
2. Explain how the given data supports or contradicts these characteristics.
3. Based on your analysis, make a recommendation about the potential of this formation for oil production.

Techniques

Chapter 1: Techniques

Unveiling the Subsurface: Formation Evaluation Techniques in Oil and Gas Exploration

Formation evaluation, a cornerstone of the oil and gas industry, relies on a diverse range of techniques to gather critical information about subsurface formations. These techniques, often referred to as "logging", involve sending specialized probes, known as logging tools, down a wellbore to measure various parameters of the surrounding formations.

Here's a breakdown of some of the key formation evaluation techniques:

1. Wireline Logging:

• Description: The most common technique, wireline logging involves lowering logging tools down a wellbore on a cable, measuring formation properties and transmitting data to the surface in real-time.
• Advantages: Versatility, ability to measure multiple parameters simultaneously, cost-effectiveness.
• Disadvantages: Limited access in deviated or horizontal wells, potential for cable snags or damage.

2. Logging While Drilling (LWD):

• Description: This technique integrates logging tools directly into the drill string, allowing measurements to be taken during drilling operations.
• Advantages: Real-time data acquisition, continuous monitoring, ability to log in complex well geometries.
• Disadvantages: Limited measurement options compared to wireline logging, higher operational costs.

3. Measurement While Drilling (MWD):

• Description: MWD focuses on directional drilling and wellbore positioning, providing real-time information about wellbore trajectory and inclination.
• Advantages: Precise wellbore control, improved drilling efficiency, reduction in drilling hazards.
• Disadvantages: Limited formation evaluation capabilities compared to LWD.

4. Nuclear Magnetic Resonance (NMR) Logging:

• Description: NMR logging uses magnetic fields to measure the hydrogen content and properties of fluids within porous rock formations.
• Advantages: Provides detailed information on porosity, permeability, and fluid saturation.
• Disadvantages: Higher operational costs, limited applicability in certain formations.

5. Seismic Interpretation:

• Description: Seismic data analysis helps create 3D images of the subsurface, identifying potential reservoir targets.
• Advantages: Provides large-scale geological information, assists in well placement.
• Disadvantages: Limited resolution, indirect information about formation properties.

6. Coring:

• Description: This technique involves retrieving physical rock samples from the formation for detailed analysis.
• Advantages: Provides direct information about the formation's composition and properties.
• Disadvantages: Expensive, time-consuming, limited accessibility in some formations.

These diverse techniques work together to provide a comprehensive understanding of the formation's characteristics, ultimately supporting optimal oil and gas production strategies.