Barefoot Completion

Test Your Knowledge

Quiz: Barefoot Completion

Instructions: Choose the best answer for each question.

1. What is the main characteristic of a barefoot completion? a) It utilizes a complex system of downhole equipment. b) It involves extensive hydraulic fracturing. c) It leaves the pay zone open and uncased. d) It requires specialized tools for production.

2. What is a primary advantage of barefoot completion? a) High initial production rates. b) Excellent control over reservoir pressure. c) Extensive stimulation options available. d) Suitable for complex reservoir formations.

3. When is barefoot completion NOT recommended? a) For reservoirs with stable formations. b) When cost-effectiveness is a priority. c) For reservoirs with complex geology. d) When quick production initiation is desired.

4. What is a potential drawback of barefoot completion? a) Increased wellbore stability. b) Reduced production costs. c) Potential for sand production. d) Limited environmental impact.

5. Which of the following completion methods contrasts with barefoot completion? a) Horizontal drilling. b) Cased hole completion. c) Open-hole drilling. d) Hydraulic fracturing.

Exercise:

Scenario:

You are an engineer evaluating a new oil well for completion. The reservoir is a simple sandstone formation with stable rock characteristics. Cost is a major concern for the project, and quick production initiation is essential.

Task:

Based on the provided information, would you recommend a barefoot completion for this well? Justify your decision by listing two benefits and one potential drawback of using a barefoot completion in this scenario.

Techniques

Barefoot Completion: A Detailed Examination

This document expands upon the concept of barefoot completion, breaking down the topic into distinct chapters for clarity and comprehensive understanding.

Chapter 1: Techniques

Barefoot completion, in its essence, is a minimalist approach. The core technique centers around leaving the producing zone (pay zone) open, without the use of casing or screens within this interval. This direct access to the reservoir allows for relatively unimpeded flow of hydrocarbons. The implementation involves several key steps:

1. Drilling and Casing: The well is drilled to the total depth, encompassing the pay zone. Casing is cemented above the pay zone, providing wellbore stability and zonal isolation from unwanted formations. The depth of the casing setting will depend on the specific geological conditions and well design.

2. Perforation (Optional): In some cases, perforations may be made in the casing above the pay zone to enhance communication with the reservoir. This is not always necessary, especially in high-permeability formations.

3. Packer Installation: A production packer is set at the top of the pay zone. This seals off the annulus between the casing and the tubing, preventing fluid flow from the wellbore into the surrounding formations and vice-versa. The packer ensures that production is only from the desired interval.

4. Tubing Installation: Production tubing is run through the packer and extends into the pay zone. This tubing carries the produced hydrocarbons to the surface.

5. Completion Testing and Production: Once the completion is installed, thorough testing is conducted to assess the well's productivity and identify any potential issues. After successful testing, the well is placed into production.

Variations in technique may include the use of gravel packing above the packer to help prevent sand production, though this is not always required and increases costs.

Chapter 2: Models

Modeling barefoot completions requires a nuanced understanding of reservoir characteristics and fluid flow. Simple reservoir models, such as radial flow models, are often sufficient for initial assessments. These models consider the permeability of the reservoir, the wellbore radius, and the pressure difference between the reservoir and the wellbore. More complex simulations might utilize numerical reservoir simulation software to account for heterogeneous reservoir properties, fluid flow complexities, and potential for sand production.

Predictive modeling is crucial for estimating production rates and assessing the longevity of the barefoot completion. Factors considered in modeling include:

• Reservoir properties: Permeability, porosity, and fluid saturation.
• Wellbore geometry: Well radius and length of the open-hole section.
• Fluid properties: Viscosity, density, and compressibility.
• Production strategy: Flow rate and pressure drawdown.
• Sand production potential: This is a critical consideration, requiring careful analysis of the formation's mechanical properties.

The output of these models informs the decision-making process regarding the feasibility and expected performance of a barefoot completion.

Chapter 3: Software

Several software packages can be utilized in the design and analysis of barefoot completions. These tools range from simple spreadsheet calculations for basic estimations to sophisticated reservoir simulators capable of handling complex reservoir geometries and fluid flow behaviors. Examples include:

• Reservoir simulation software: CMG STARS, Eclipse, and Schlumberger's Petrel are widely used for modeling reservoir behavior, including fluid flow in barefoot completions. These packages allow for detailed simulation of pressure distribution, production rates, and sand production.

• Wellbore simulation software: These tools are used to predict pressure drop within the wellbore and optimize completion design for efficient production.

• Geomechanical modeling software: This is vital for assessing the risk of sand production and formation stability. Examples include ABAQUS and FLAC.

The choice of software depends on the complexity of the reservoir and the level of detail required for the analysis. Simpler reservoirs might only necessitate the use of basic spreadsheet calculations or specialized well completion design software, while complex reservoirs require the use of full-field reservoir simulators.

Chapter 4: Best Practices

Successful implementation of barefoot completions relies heavily on careful planning and execution. Best practices include:

• Thorough geological and geomechanical studies: A detailed understanding of reservoir properties is critical to assess the suitability of a barefoot completion. This includes assessing formation stability, permeability, and sand production potential.

• Careful selection of well location and trajectory: Optimizing well placement within the reservoir can maximize production and minimize risks.

• Proper wellbore cleaning and preparation: Removing drilling debris and ensuring a clean wellbore is essential for efficient fluid flow.

• Rigorous quality control: Close monitoring of all completion operations is vital to ensure the integrity of the completion.

• Regular well monitoring and maintenance: Closely monitoring well performance helps identify potential problems early on. This includes regular pressure and flow rate measurements, as well as periodic production logging.

• Contingency planning: Having plans in place to address potential issues, such as sand production or formation instability, is crucial.

Chapter 5: Case Studies

(Note: Specific case studies require confidential data and are not included here. However, a framework for presenting case studies is provided below.)

Case studies should illustrate the successful application (and potential failures) of barefoot completions in various geological settings. Each case study should include:

• Reservoir characteristics: Description of reservoir properties (permeability, porosity, fluid type, etc.) and geological setting.
• Completion design: Details of the completion design, including casing depth, packer type, tubing size, and any additional equipment used.
• Production performance: Data on production rates, pressure drawdown, and well longevity.
• Cost analysis: Comparison of completion costs with other completion methods.
• Lessons learned: Key insights and lessons learned from the project, including successes, challenges, and recommendations for future applications.

By analyzing multiple case studies, a clear understanding can be developed regarding the effectiveness and limitations of barefoot completions in diverse reservoir conditions. These studies should highlight the importance of careful reservoir characterization and appropriate completion design in achieving successful outcomes.