Dissolvable Plugs for Pre-Perforated Liners as a Key to Successful ERD Well Completion

Introduction

In the context of modern Extended Reach Drilling (ERD) operations, achieving efficient and cost-effective well completion is a primary challenge. Dissolvable plugs, specifically designed for pre-perforated liners, present a breakthrough solution by simplifying operations, reducing completion time, and enhancing well performance. Their innovative design allows for temporary isolation of perforations while enabling seamless wellbore fluid circulation and controlled activation of downhole systems.

Background and Importance

Well completions involving pre-perforated or slotted liners are widely used in production zones. Traditional methods, such as non-dissolvable plugs or wash pipes, often impose operational inefficiencies and complications, particularly in ERD wells with complex geometries. Dissolvable plugs, made from advanced aluminum-magnesium alloys, address these limitations by providing a temporary isolation mechanism that dissolves predictably under specific wellbore conditions.

Challenges in ERD Wells

ERD wells pose unique challenges due to their extreme lengths, high deviation angles, and mechanical loads:

• Hole Cleaning: Poor cuttings removal can lead to borehole instability and reduced drilling efficiency.

• Mechanical Stress: Managing axial and torsional loads on the drill string is critical for operational success.

• Wellbore Instability: Long horizontal sections exacerbate issues of differential pressure and wellbore collapse.

• Completion Complications: Delivering the required load to set liners and isolation devices becomes increasingly difficult with extended MD (measured depth).

  
  

Dissolvable plugs offer a reliable solution for mitigating these challenges by eliminating the need for conventional flushing pipes and shear plugs, particularly in high-deviation ERD environments.

Dissolvable Plugs: Function and Specifications

Dissolvable plugs provide temporary perforation isolation while enabling circulation during the run-in-hole (RIH) process. Once in place, the plugs dissolve at a predictable rate, triggered by the surrounding completion fluids.

Key Specifications:

• Type: Threaded

• Material: Dissolvable aluminum-magnesium alloy

• Diameter: From 5 mm

• Operating Temperature: Up to 150°C (300°F)

• Differential Pressure Rating: Up to 250 bar

• Isolation Duration: 1 to 10 days (depending on wellbore conditions)

The dissolution rate can be fine-tuned based on temperature and fluid properties, ensuring controlled activation and seamless integration into completion operations.

Practical Applications

Dissolvable plugs have a wide range of practical applications, including:

1. Pre-Perforated Liners for Circulation: Enable flushing through the casing shoe without shear plugs or wash pipes.

2. Floating Liner Systems in ERD Wells: Facilitate running liners to ultra-long horizons (>4000 m) with reduced risk and operational effort.

3. Hydraulic Packer Activation: Provide temporary isolation to activate downhole hydraulic systems.

4. Cementing Operations: Allow cementing of the upper section of slotted liners.

5. Temporary Isolation in Complex Well Geometries: Ideal for fishbone completions requiring selective zonal isolation.

By dissolving in controlled conditions, the plugs ensure reliable isolation during RIH operations and subsequent release of perforations, optimizing overall completion efficiency.

Benefits:

• Significant reduction in rig time and well completion duration.

• Elimination of additional mill-out trips.

• Adjustable dissolution times tailored to fluid environments.

• Enhanced liner integrity and hermetic sealing.

• Compatibility with hydraulic packers and cemented completions.

• Improved operational efficiency in ERD wells with floating liner systems.

Challenges:

• Accurate selection of dissolvable alloys to match wellbore conditions.

• Strict requirements for perforation quality and installation precision.

• Sensitivity of materials to moisture during transportation and storage.

• Potential changes in downhole conditions that may impact dissolution behavior.

Dissolvable plugs represent a cutting-edge solution for enhancing ERD well completion efficiency. By addressing key challenges such as temporary isolation, controlled fluid flow, and reduced operational complexity, these plugs enable operators to achieve cost-effective and reliable completions. Continued advancements in dissolvable alloy technology and field-proven applications are paving the way for broader adoption across the oil and gas industry.