Forage et complétion de puits

Sidetrack

Déviation : Une deuxième chance en forage et complétion de puits

Dans le monde de l'exploration pétrolière et gazière, le forage d'un puits est une entreprise complexe et coûteuse. Parfois, des circonstances imprévues peuvent entraîner des complications qui rendent le puits initial inutilisable. C'est là qu'intervient la **déviation** - une technique qui permet aux ingénieurs de forage de sauver la situation et de poursuivre leur quête d'hydrocarbures.

**Qu'est-ce que la déviation ?**

La déviation fait référence au processus de forage d'un nouveau puits, appelé **déviation**, à partir d'un puits existant. Cette technique est généralement utilisée lorsque le puits initial rencontre :

  • **Formations géologiques imprévues :** Un puits peut rencontrer des couches rocheuses impénétrables, des failles ou d'autres caractéristiques géologiques inattendues qui entravent la poursuite du forage.
  • **Perte de circulation :** Le fluide de forage peut être perdu dans la formation environnante, ce qui rend difficile le maintien de la pression et le contrôle du processus de forage.
  • **Tuyau coincé :** La colonne de forage peut se coincer à l'intérieur du puits, rendant impossible la poursuite du forage.
  • **Effondrement du puits :** Les parois du puits peuvent s'effondrer, créant une instabilité et compromettant l'intégrité du puits.

**Types de déviation :**

Il existe deux principaux types de déviation :

  1. **Déviation conventionnelle :** Cela implique le forage d'un nouveau puits à partir du puits existant à une profondeur spécifique, généralement au fond du puits initial. La déviation est ensuite forée dans une nouvelle direction pour atteindre la zone cible.
  2. **Déviation parallèle :** Dans ce type, le nouveau puits est foré parallèlement au puits d'origine, généralement à une profondeur moins profonde. Cette technique est utilisée lorsque le puits principal doit être réinjecté ou lorsque la zone cible est située à un niveau différent.

**Pourquoi choisir la déviation ?**

La déviation offre plusieurs avantages par rapport à l'abandon complet du puits initial et à un nouveau départ :

  • **Économies de coûts :** La déviation permet aux ingénieurs de forage d'utiliser la structure et les infrastructures du puits existant, réduisant considérablement le temps et les coûts nécessaires pour atteindre la zone cible.
  • **Sécurité accrue :** La déviation minimise les risques associés au reforage de l'ensemble du puits, réduisant la possibilité de rencontrer les mêmes problèmes géologiques qui ont conduit aux problèmes initiaux.
  • **Efficacité accrue :** Le puits existant sert de guide pour le nouveau puits, permettant un processus de forage plus efficace et précis.

**Les défis de la déviation :**

La déviation n'est pas sans défis :

  • **Intégrité du puits :** Le puits existant doit être suffisamment stable pour supporter les opérations de forage de la déviation.
  • **Géométrie du puits :** La taille et la forme du puits existant peuvent limiter la taille et la direction de la déviation.
  • **Expertise technique :** La déviation nécessite un équipement spécialisé et des ingénieurs hautement qualifiés pour exécuter le processus de forage avec succès.

**Conclusion :**

La déviation est un outil précieux dans l'industrie pétrolière et gazière, offrant une seconde chance d'atteindre de précieuses réserves d'hydrocarbures malgré les défis inattendus rencontrés lors du forage initial. En tirant parti des infrastructures existantes et de l'expertise technique, la déviation offre une solution rentable et efficace pour surmonter les obstacles de forage et maximiser le succès des projets d'exploration.

Test Your Knowledge

Sidetracking Quiz

Instructions: Choose the best answer for each question.

1. What is sidetracking in the context of drilling and well completion?

a) Drilling a new wellbore entirely independent of any existing wellbores. b) Drilling a new wellbore from an existing wellbore to reach a different target zone. c) A technique to increase the diameter of an existing wellbore. d) A method used to stabilize the wellbore walls during drilling.

Answer

b) Drilling a new wellbore from an existing wellbore to reach a different target zone.

2. Which of the following scenarios is NOT a common reason for using sidetracking?

a) Encountering impenetrable rock layers. b) Successful completion of the initial wellbore. c) Lost circulation of drilling fluid. d) Stuck pipe in the wellbore.

Answer

b) Successful completion of the initial wellbore.

3. What is the key difference between conventional and parallel sidetracking?

a) Conventional sidetracking is more expensive. b) Parallel sidetracking is used for deeper targets. c) Conventional sidetracking drills the new wellbore from the bottom of the existing wellbore. d) Parallel sidetracking is less risky than conventional sidetracking.

Answer

c) Conventional sidetracking drills the new wellbore from the bottom of the existing wellbore.

4. Which of the following is NOT an advantage of using sidetracking?

a) Cost savings compared to completely abandoning the initial wellbore. b) Reduced risk of encountering the same drilling issues. c) Increased efficiency due to the existing wellbore acting as a guide. d) Guaranteed success in reaching the target zone.

Answer

d) Guaranteed success in reaching the target zone.

5. What is one of the main challenges associated with sidetracking?

a) The need for specialized equipment. b) The availability of skilled engineers. c) The possibility of encountering unforeseen geological formations. d) All of the above.

Answer

d) All of the above.

Sidetracking Exercise

Scenario: An oil company is drilling a well to reach a hydrocarbon reservoir at a depth of 10,000 feet. However, at a depth of 6,000 feet, the drill string gets stuck due to a geological formation. The company decides to implement sidetracking.

Task: Describe the two possible types of sidetracking that could be used in this scenario and explain which option would be more suitable and why.

Exercice Correction

The company could choose between:

1. **Conventional Sidetracking:** Drill a new wellbore from the bottom of the existing wellbore (at 6,000 feet) in a new direction to reach the target reservoir at 10,000 feet.

2. **Parallel Sidetracking:** Drill a new wellbore parallel to the existing wellbore at a shallower depth, aiming to reach the reservoir at a different horizontal position.

In this scenario, **conventional sidetracking** would be more suitable. This is because the objective is to reach the same target reservoir at the same depth. Conventional sidetracking allows for a direct path to the target zone, avoiding the need to re-drill to the same depth as the original wellbore. Parallel sidetracking would be less effective in this case as it would potentially lead to a different horizontal location within the reservoir.

Books

  • Petroleum Engineering Handbook: This comprehensive handbook offers detailed information on various aspects of drilling, including sidetracking techniques.
  • Drilling Engineering: A Comprehensive Approach: This book provides in-depth knowledge of drilling practices and technologies, including a section on sidetracking and its applications.
  • Well Completion Engineering: This book focuses on the post-drilling phase and covers different techniques for completing wells, including sidetracking.

Articles

  • "Sidetracking: A Cost-Effective Way to Achieve Wellbore Success" by SPE: This article delves into the economic and operational benefits of using sidetracking techniques in drilling operations.
  • "Sidetracking Techniques for Challenging Wellbore Conditions" by Oilfield Technology: This article explores various sidetracking techniques and their applications in different drilling scenarios.
  • "Sidetracking: A Tool for Re-Entry and Reservoir Access" by Schlumberger: This article highlights the role of sidetracking in re-entering wells and accessing different reservoir zones.

Online Resources

  • SPE (Society of Petroleum Engineers): The SPE website offers a vast library of publications, technical papers, and presentations on sidetracking and other drilling-related topics.
  • *Schlumberger: * This leading oilfield services company provides valuable insights into various drilling technologies, including sidetracking, on its website.
  • Baker Hughes: Another major oilfield services company, Baker Hughes offers resources on drilling and well completion technologies, including information on sidetracking.

Search Tips

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  • "Sidetracking well completion"
  • "Sidetracking cost analysis"
  • "Types of sidetracking"
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Techniques

Chapter 1: Techniques

Sidetracking Techniques: A Guide to Drilling Beyond Obstacles

Sidetracking, as discussed previously, is a valuable tool in the oil and gas industry, allowing engineers to navigate unforeseen drilling complications. This chapter delves deeper into the various techniques employed in sidetracking, providing a comprehensive understanding of the process.

1.1 Conventional Sidetracking:

  • Process: This method involves drilling a new wellbore from the existing wellbore at a specific depth, typically at the bottom of the initial wellbore. This new wellbore, the sidetrack, is then drilled in a new direction to reach the target zone.
  • Tools:
    • Whipstock: A wedge-shaped tool placed inside the existing wellbore to initiate the new bore path.
    • Jetting: Using high-pressure jets to create a path for the drill bit.
    • Directional Drilling: Utilizing advanced drilling tools and techniques to control the direction and trajectory of the sidetrack.
  • Advantages:
    • Relatively straightforward execution.
    • Suitable for various geological challenges.
  • Disadvantages:
    • Requires sufficient space at the bottom of the initial wellbore.
    • May be limited in terms of directional changes.

1.2 Parallel Sidetracking:

  • Process: The new wellbore is drilled parallel to the original wellbore, typically at a shallower depth. This method is preferred when re-entering the primary wellbore or targeting a zone at a different level.
  • Tools:
    • Pilot Hole: A small hole drilled to establish the path for the sidetrack.
    • Casing: Steel pipes used to support and seal the wellbore.
  • Advantages:
    • Allows for re-entry into the existing wellbore.
    • Enables targeting zones at different depths.
  • Disadvantages:
    • May require larger wellhead structures.
    • May not be suitable for complex geological formations.

1.3 Other Techniques:

  • Open-hole Sidetracking: Drilling the sidetrack directly through the existing wellbore. This technique is risky and is only used in specific circumstances.
  • Cased-hole Sidetracking: Drilling the sidetrack through a casing string that has already been installed. This method offers greater stability and control.

1.4 Considerations:

  • Wellbore Integrity: The existing wellbore must be stable and able to withstand the pressure and forces associated with sidetracking.
  • Wellbore Geometry: The size and shape of the existing wellbore impact the feasibility of sidetracking.
  • Target Zone Location: The location of the target zone dictates the direction and length of the sidetrack.
  • Drilling Fluids: The type and properties of drilling fluids used are crucial for maintaining wellbore stability and minimizing formation damage.

1.5 Conclusion:

Choosing the appropriate sidetracking technique depends on the specific circumstances of each well. By understanding the various techniques and their advantages and disadvantages, engineers can choose the most effective method to overcome drilling obstacles and achieve exploration success.

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