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Glossary of Technical Terms Used in Drilling & Well Completion: Short String (dual completion)

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Short String (dual completion)

Understanding the "Short String" in Dual Completion Wells

In the world of oil and gas production, maximizing resource extraction is paramount. Dual completion wells, where two separate zones within a single wellbore are produced simultaneously, offer a strategic approach to achieving this. Understanding the "short string" is crucial to grasp the intricate workings of such wells.

Defining the Short String:

The "short string" refers to the completion string leading to the upper completion in a side-by-side dual completion well. This string typically runs from the surface to the upper production zone, encompassing components like tubing, packers, and downhole equipment specifically designed for the upper zone.

Why "Short"?:

The term "short" arises from the fact that this string is shorter than the "long string" leading to the lower completion. This difference in length is essential for isolating the two zones and managing production independently. The short string is designed to be significantly shorter to accommodate the depth difference between the two production zones.

Components of the Short String:

A typical short string includes:

  • Tubing: The primary conduit for production fluids, specifically designed to withstand the pressure and temperature conditions of the upper zone.
  • Packers: Mechanical devices placed at the interface between the short string and the long string, creating a barrier to prevent fluid communication between the two zones.
  • Downhole equipment: Includes valves, chokes, and other equipment specific to the upper completion, allowing for independent control and optimization of production from that zone.
  • Surface equipment: Includes flowlines, separators, and other surface facilities dedicated to the production and processing of fluids from the upper zone.

Advantages of the Short String:

  • Independent production: Allows for separate control and optimization of production from each zone, maximizing overall well productivity.
  • Zone isolation: Ensures that fluids from the upper zone do not enter the lower zone and vice versa, preventing intermingling and potential contamination.
  • Flexibility in production: Permits selective production from either or both zones, depending on reservoir conditions and market demands.

Challenges associated with the Short String:

  • Wellbore stability: The short string's shorter length can lead to greater potential for instability in the wellbore, requiring careful design and installation.
  • Packer reliability: Packers are critical components, and their failure can result in communication between the zones, compromising production efficiency.
  • Complexity: Dual completion systems are inherently more complex than single completion wells, requiring specialized expertise for design, installation, and operation.

Conclusion:

The short string is an essential component of side-by-side dual completion wells, enabling the independent production and management of two different zones within a single wellbore. Understanding its role, components, and potential challenges is crucial for maximizing resource recovery and ensuring safe and efficient operation of these complex wells.

Test Your Knowledge

Quiz: Understanding the Short String in Dual Completion Wells

Instructions: Choose the best answer for each question.

1. What does the term "short string" refer to in a dual completion well? a) The completion string leading to the lower completion zone. b) The completion string leading to the upper completion zone. c) The tubing string connecting the surface to the downhole equipment. d) The casing string that lines the wellbore.

Answer

b) The completion string leading to the upper completion zone.

2. Why is the "short string" called "short"? a) It is shorter than the casing string. b) It is shorter than the long string leading to the lower completion. c) It is designed for producing short bursts of oil and gas. d) It is a shorter length of tubing compared to other completion strings.

Answer

b) It is shorter than the long string leading to the lower completion.

3. Which of the following is NOT a typical component of a short string? a) Tubing b) Packers c) Casing string d) Downhole equipment

Answer

c) Casing string

4. What is a key advantage of using a short string in a dual completion well? a) Simplifies wellbore construction. b) Reduces the risk of wellbore instability. c) Allows for independent production from each zone. d) Eliminates the need for downhole equipment.

Answer

c) Allows for independent production from each zone.

5. Which of the following presents a challenge associated with using a short string? a) Limited production capacity. b) Difficulty in isolating the zones. c) Increased risk of wellbore instability. d) Higher initial installation costs.

Answer

c) Increased risk of wellbore instability.

Exercise: Short String Design

Task: You are designing a dual completion well with the following parameters:

  • Upper zone depth: 10,000 ft
  • Lower zone depth: 12,000 ft
  • Tubing size: 2.875 inches

Design the short string for this well, including the following:

  • Tubing length: Calculate the length of the tubing required for the short string.
  • Packer location: Determine the depth at which the packer should be placed to isolate the upper zone.
  • Downhole equipment: List at least two essential pieces of downhole equipment for the upper zone completion.

Note: You can assume standard industry practices and safety regulations for well completion.

Exercice Correction

**Tubing Length:** 10,000 ft (from surface to the upper zone)

**Packer Location:** 10,000 ft (at the top of the upper zone, to isolate it from the lower zone)

**Downhole Equipment:** * **Production Valve:** To control flow from the upper zone. * **Choke:** To regulate flow rate and pressure.

**Explanation:** The tubing length for the short string is equal to the depth of the upper zone. The packer is placed at the top of the upper zone to prevent fluid communication between the two zones. The production valve and choke are essential downhole equipment for controlling and managing production from the upper zone.

Books

  • "Petroleum Engineering: Drilling and Well Completions" by John C. Bowman (This textbook provides a comprehensive overview of well completion techniques, including dual completions.)
  • "Well Completion Design: A Practical Approach" by William J. Lee (Covers various completion designs, including dual completions, with emphasis on practical applications.)
  • "The Practical Handbook of Well Completions: From Concept to Completion" by Richard A. Dean (This handbook offers a detailed guide to completion design, installation, and troubleshooting, including sections on dual completion wells.)

Articles

  • "Dual Completions: Optimizing Production from Multiple Reservoirs" by SPE Journal (This technical paper discusses the advantages and challenges of dual completion systems, with a focus on maximizing production efficiency.)
  • "Case Study: Successful Application of Dual Completion in a Tight Gas Formation" by Journal of Petroleum Technology (Provides a practical example of using dual completion to improve production in a challenging reservoir.)
  • "Packer Technology for Dual Completions: Ensuring Effective Zone Isolation" by Oil & Gas Engineering Journal (Explores the importance of packers in dual completion wells, highlighting their design and functionality.)

Online Resources

  • SPE (Society of Petroleum Engineers): https://www.spe.org/ (This organization offers a vast database of technical papers, presentations, and other resources related to oil and gas production, including dual completion technologies.)
  • OnePetro: https://www.onepetro.org/ (OnePetro hosts a collection of technical literature and data related to the oil and gas industry, with searchable content on dual completions.)
  • Schlumberger: https://www.slb.com/ (Schlumberger, a leading oilfield services company, provides technical information and case studies on various completion techniques, including dual completions.)

Search Tips

  • Use specific keywords: "dual completion wells", "short string", "packers", "zone isolation", "production optimization"
  • Combine keywords with operators: "dual completion wells AND short string"
  • Include specific well types: "horizontal well dual completion", "tight gas dual completion"
  • Add site: operator: "site:spe.org dual completion"
  • Explore image search: Look for diagrams and illustrations of short string components and dual completion systems.
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