Reservoir Engineering

RFT

RFT: Unlocking the Secrets of Reservoirs - Repeat Formation Tester

In the oil and gas industry, understanding the characteristics of underground reservoirs is crucial for successful exploration and production. One powerful tool used to gather this critical information is the Repeat Formation Tester (RFT).

What is an RFT?

An RFT is a specialized downhole instrument designed to repeatedly measure the pressure and fluid properties of a reservoir formation. It's deployed on wireline, typically after a well has been drilled and cased. The RFT operates by isolating a specific zone in the formation and conducting pressure measurements over time. This allows engineers to gather valuable data about:

  • Reservoir pressure: This data is essential for determining the reservoir's productivity and predicting future production rates.
  • Fluid properties: Analyzing the fluid samples retrieved from the formation helps understand the composition (oil, gas, water), viscosity, and other key parameters.
  • Reservoir permeability: By observing the rate at which pressure declines, engineers can estimate the permeability of the formation, indicating its ability to allow fluids to flow.

How does it work?

An RFT consists of a series of components, including:

  • A packer: This inflatable device seals off the target zone in the formation, isolating it from the surrounding area.
  • A pressure gauge: Measures the pressure within the isolated zone, providing accurate readings over time.
  • A sampling system: Allows for the collection of fluid samples from the formation for analysis.

Once deployed in the well, the RFT is activated, and the packer is inflated to isolate the target zone. Pressure measurements are then taken at regular intervals, allowing engineers to observe pressure changes over time. These measurements provide insights into the reservoir's fluid properties, pressure gradients, and flow characteristics.

Benefits of RFT:

  • Detailed reservoir characterization: Provides comprehensive data on reservoir properties, aiding in production optimization and field development planning.
  • Improved production forecasting: Accurate pressure and fluid data enhance the prediction of future production rates and well performance.
  • Enhanced well management: RFT data helps identify potential production issues and optimize well completion strategies.
  • Reduced uncertainty: By providing more accurate information about the reservoir, RFT helps mitigate uncertainties associated with exploration and production decisions.

Conclusion:

The Repeat Formation Tester is a valuable tool for oil and gas professionals, offering a detailed understanding of reservoir properties and facilitating informed decisions for successful exploration and production. By leveraging the data obtained from RFTs, engineers can optimize field development, enhance production, and maximize the economic potential of oil and gas reservoirs.


Test Your Knowledge

Instructions: Choose the best answer for each question.

1. What is the primary function of a Repeat Formation Tester (RFT)?

a) To measure the temperature of the reservoir formation. b) To inject fluids into the reservoir for stimulation. c) To repeatedly measure pressure and fluid properties of a reservoir formation. d) To identify the presence of hydrocarbons in a well.

Answer

c) To repeatedly measure pressure and fluid properties of a reservoir formation.

2. Which of the following components is NOT part of a typical RFT system?

a) Packer b) Pressure gauge c) Sampling system d) Drilling bit

Answer

d) Drilling bit

3. What information does an RFT provide that is crucial for production forecasting?

a) Wellbore diameter b) Reservoir pressure c) Drill pipe size d) Cement bond log data

Answer

b) Reservoir pressure

4. How does an RFT help mitigate uncertainties in exploration and production decisions?

a) By analyzing the composition of the wellbore fluid b) By determining the depth of the reservoir c) By providing more accurate information about the reservoir properties d) By identifying potential drilling hazards

Answer

c) By providing more accurate information about the reservoir properties

5. Which of the following is NOT a benefit of using an RFT?

a) Improved production forecasting b) Enhanced well management c) Reduced uncertainty d) Determining the best location for a new well

Answer

d) Determining the best location for a new well

RFT Exercise: Analyzing Pressure Data

Scenario: An RFT was deployed in a well to measure reservoir pressure. The following pressure readings were obtained at different times:

| Time (hours) | Pressure (psi) | |---|---| | 0 | 3000 | | 2 | 2950 | | 4 | 2900 | | 6 | 2850 | | 8 | 2800 |

Task:

  1. Plot the pressure data on a graph (time vs. pressure).
  2. Calculate the average pressure decline rate (psi/hour).
  3. Using the pressure decline rate, estimate the reservoir pressure after 12 hours.

Exercice Correction:

Exercice Correction

1. The plot should show a linear decline in pressure over time. 2. Average pressure decline rate = (3000 psi - 2800 psi) / 8 hours = 25 psi/hour 3. Estimated pressure after 12 hours = 2800 psi - (25 psi/hour * 4 hours) = 2700 psi


Books

  • Reservoir Engineering Handbook by Tarek Ahmed, published by Gulf Professional Publishing. This comprehensive handbook covers various aspects of reservoir engineering, including formation testing techniques.
  • Well Testing by Matthew D. Johnson, published by Elsevier. This book provides a detailed explanation of well testing methods, including Repeat Formation Testing.
  • Petroleum Engineering Handbook by G.P. Merrill, published by Society of Petroleum Engineers (SPE). This handbook offers a broad overview of petroleum engineering practices, with sections dedicated to formation evaluation and testing.

Articles

  • "Repeat Formation Tester (RFT) for Reservoir Evaluation" by Schlumberger, available on their website. This article provides a detailed overview of RFT technology, its applications, and benefits.
  • "Reservoir Pressure Transient Analysis: Interpretation of RFT Data" by Halliburton, available on their website. This article focuses on interpreting pressure transient data obtained from RFTs.
  • "Case Studies on the Application of Repeat Formation Testers in Reservoir Characterization" by SPE, available through their online library. This collection of case studies showcases real-world applications of RFTs in different reservoir settings.

Online Resources

  • Schlumberger - Formation Testing: https://www.slb.com/services/formation-testing - This website offers a detailed explanation of various formation testing techniques, including RFTs, along with case studies and technical documents.
  • Halliburton - Formation Evaluation & Testing: https://www.halliburton.com/services/formation-evaluation-and-testing - Similar to Schlumberger, Halliburton provides information on formation testing, including RFTs, and various related services.
  • SPE - Technical Resources: https://www.spe.org/ - The Society of Petroleum Engineers website offers a vast repository of technical articles, presentations, and publications related to reservoir engineering and formation testing.

Search Tips

  • "Repeat Formation Tester" + "Reservoir Characterization" - This search will provide articles and resources specifically focused on how RFTs are used to understand reservoir properties.
  • "RFT" + "Case Studies" - This search will identify real-world applications of RFTs in different geological settings.
  • "Formation Testing" + "Technical Papers" - This search will lead to a collection of research papers and presentations on various aspects of formation testing, including RFTs.

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