Overview

Directional hydraulic sandblasting perforation is an advanced well completion and reservoir stimulation technology widely used in horizontal wells. It combines abrasive jetting with precise directional control to create perforations in casing and cement, connecting the wellbore with the reservoir in a targeted, efficient manner. The technology is particularly suited for tight formations, unconventional plays, and multistage stimulation.

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1. Directional Perforation Technology Overview

This technology is categorized into two main aspects:

A. Perforation Methods

These refer to the techniques used to physically perforate the casing or formation:

1. Electric Wireline Explosive Perforation
   • Uses shaped charges conveyed via electric wireline to perforate the casing and cement sheath.
2. Hydraulic Jet Perforation
   • Utilizes high-pressure fluid (typically carrying abrasive particles) to create perforations through hydraulic erosion.
3. Steel Wire Tool Punching
   • A mechanical method involving a steel-wire-conveyed tool to punch holes through the casing.

B. Orientation Methods

These define how the perforation is directionally controlled within the wellbore:

1. Gravity-Based Internal Orientation
   • Relies on gravity to orient perforation tools within the internal well casing environment.
2. Gravity-Based External Orientation
   • Uses external gravity reference systems to control the perforation direction from outside the casing.
3. Gyroscopic Tool Orientation
   • Employs gyroscopes to precisely control the azimuth and inclination of the perforation, independent of gravitational direction.

2. Directional Hydraulic Sandblasting Perforation Technology

This section focuses on the directional methods used in hydraulic sandblasting perforation. The technology is classified into two primary types based on the orientation mechanism and corresponding conveyance method:

A. Orientation Methods for Hydraulic Sandblasting Perforation

1. Gravity-Driven Mechanical External Orientation
   • Orientation is achieved mechanically using gravity-based external structures.
   • Deployment Method: Tubing conveyed
2. Gravity-Driven Hydraulic Internal Orientation
   • Orientation relies on internal hydraulic mechanisms guided by gravity.
   • Deployment Method: Coiled tubing conveyed

2.1 Gravity-Based Mechanical External Orientation Tool

Mechanical Directional Hydraulic Jet Fracturing String Structure

Same components as previously illustrated:

• Tubing Connector
• Releasing Tool
• Centralizer
• Rotating Sub
• Mechanical Directional Jetting Tool
• Circulation Valve
• Bottom Packer
• Collar Locator
• Guide Shoe

Main Functions:

1. Directional Jet Nozzle Orientation
   The nozzle direction is preset to enable targeted layer-specific directional jet perforation and fracturing operations.
2. Sliding Sleeve with Selective Jetting Tool
   The directional jetting tool can be equipped with a sliding sleeve. By using pressure differential to activate the sleeve, the nozzle direction is locked, allowing precise layer-specific directional jet perforation and fracturing.
3. Rotating Sub for Gravity-Based Tool Orientation
   The rotating sub provides gravity-based orientation capability for sliding-sleeve-style directional jetting tools.
4. Perforation-Only Option
   If only perforation is required and fracturing is not needed, the bottom packer can be removed from the string.

Main Functions:

• The jet nozzle is directionally oriented in advance, enabling layer-specific directional jet perforation and fracturing operations.
• The tubing control valve is activated by fluid pressure during pumping operations, and automatically closes after pumping stops.

Component: Rotating Sub

The rotating sub is a critical tool used to achieve directional orientation in mechanical jetting systems.

Main Technical Specifications:

1. Pressure Resistance: Up to 70 MPa
2. Flow Capacity: Meets the requirement for 4-way sand-laden fluid discharge within tubing
3. Impact Resistance: Center tube is designed to withstand high-velocity fluid impact

Key Functional Features:

1. Bidirectional Bearing Support
   Enables 360-degree rotation for precise alignment of the jetting nozzle.
2. Angular Freedom Under Deviation
   Allows free rotation within a 30-degree vertical deviation, adapting to downhole doglegs and irregularities.
3. High-Pressure Sealing Without Torsional Load
   The tool bears high-pressure sealing but is isolated from torque loads, preventing mechanical strain during operation.

Component: Directional Jetting Tool

This tool is responsible for generating high-pressure abrasive jets for perforation and/or fracturing, with automatic orientation based on gravitational alignment.

Key Features:

1. Gravity-Based Auto Orientation
   • The tool automatically aligns its jetting ports in the desired direction using gravitational reference, eliminating the need for electronic or manual orientation systems.
2. Customizable Nozzle Configuration
   • The number and type of nozzles can be customized according to operational requirements.
   • The default configuration includes 4 jetting nozzles.
3. Standard Nozzle Specifications
   • Default nozzle diameter: 4.5 mm
   • Each nozzle is capable of discharging more than 60 sand m³ (cubic meters of sand-laden fluid), ensuring high-efficiency abrasive jetting.

Component: Directional Jetting Tool (Structure & Specifications)

Orientation Principle:

• The directional jetting tool is designed with an eccentric center of gravity.
• Under the influence of gravity, the tool automatically rotates to the lowest point, aligning the nozzles in the designated direction.
• This self-aligning design enables directional control without electronic components.
• Nozzle direction is adjustable to suit operational targets.

Dimensional Specifications Table:

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Operation Workflow

Directional Hydraulic Sandblasting Perforation & Fracturing Procedure:

1. Determine Target Depth
   • Based on the pre-designed reservoir modification plan, confirm the required setting depth of the downhole tool string.
2. Tool Positioning & Jet Perforation
   • Once the tool reaches the target depth, begin sand injection through the tubing to perform directional hydraulic sandblasting perforation at the designated formation layer.
3. Post-Perforation Fracturing
   • After perforation, continue sand injection via tubing to carry out hydraulic fracturing through the perforation tunnels.
4. Stage-Wise Treatment
   • Conduct layer-by-layer stimulation from bottom to top, ensuring orderly enhancement of each reservoir section.
5. Reverse Circulation Option
   • In the event of sand accumulation or wellbore blockage, optional reverse circulation washing can be performed to ensure wellbore cleanliness and tool retrieval.

2.2 Gravity-Based Hydraulic Internal Orientation Tool

Main Functions:

1. Pre-Set Nozzle Orientation
   • The spray direction of the jetting nozzle can be preset in advance to achieve accurate layer-specific directional perforation and fracturing operations.
2. Rotating Sub for Gravity-Based Orientation
   • Although not shown explicitly in the diagram, a rotating sub may be included as an assistive component to facilitate gravity-based nozzle alignment.
3. Optional Use for Perforation-Only Jobs
   • If hydraulic fracturing is not required, the bottom packer can be removed, allowing the system to function purely as a jet perforation tool.
4. Hydraulic Orientation Control
   • The internal hydraulic drive ensures strong resistance to torsional forces, enhancing stability and directional control during operation.

Orientation Mechanism Principle

When the tool is lowered to a predetermined position within the wellbore, the internal orientation ball inside the tool is affected by gravity and naturally moves to the lowest point of the tool chamber.

Once it reaches this lowest point, the ball enters a positioning slot, initiating the orientation process. Under fluid flow pressure, a guiding mechanism connected to the jetting nozzle is driven to rotate along the guiding track defined by the ball’s movement.

This mechanism allows the jetting nozzle to complete directional rotation, aligning itself precisely as required for effective perforation.

Reset and Repeatability

After the operation is complete:

• A compression spring automatically resets the orientation mechanism back to its initial state.
• Upon subsequent movement of the tool to the next target location, the system is ready to execute another round of orientation.

Labeled Components (from image)

• Orienter : Gravity-guided mechanical orientation system.
• Jetting Nozzle : Outputs high-pressure abrasive fluid.
• Rotating Sub : Facilitates fluidic-driven rotation and directional stabilization.

Key Features:

• Vertical Gravity-Based Orientation:
  The internal orientation mechanism relies on gravity for vertical alignment, making it resilient to complex downhole conditions.
• Hydraulic Drive Enhancement:
  Utilizes fluid pressure effectively to generate sufficient torque, enabling the jetting assembly to rotate smoothly for directional alignment.
• Simple Structure with High Reliability:
  The mechanism is easy to implement, with high structural reliability, reducing maintenance demands and risk of failure.
• Repeatable Directional Perforation:
  Supports multiple re-orientations and perforation cycles, significantly improving operational efficiency for multistage completions.

Technical Specifications Table:

Construction Workflow

Directional Hydraulic Sandblasting and Fracturing Operation Steps:

1. Determine Tool Setting Depth
   • Based on the targeted formation for stimulation, confirm the appropriate depth for lowering the tool string.
2. Stabilization at Target Depth
   • Upon reaching the predetermined location, pause pumping for 2 minutes, then gradually increase the pressure to 3 MPa and maintain it for another 2 minutes to allow the internal orienting mechanism to settle.
3. Directional Sand Jet Perforation
   • Inject sand slurry through the tubing to perform directional hydraulic sandblasting perforation at the designated layer.
4. Hydraulic Fracturing via Perforation
   • After perforation, continue sand injection through the tubing to fracture the reservoir through the created perforation channels.
5. Section-by-Section Rinse and Cleanout
   • After each interval is completed, inject clean water through the tubing and open two circulation ports to rinse and clean the tool string.
6. Stage-Wise Reservoir Treatment
   • Proceed with the stimulation from bottom to top, treating each target layer sequentially.
7. Optional Reverse Circulation for Sand Removal
   • If sand blockage occurs, reverse circulation can be selectively applied to clean the wellbore and maintain tool operability.

Limitations

Wireline Transmission:

1. Cannot be used in horizontal sections with spiral trajectory;
2. Difficult to retrieve orientation device once deployed — one-time use only.

| Wireline Perforating:
Depends on gravity from eccentric weight to generate rotational force;
If the well has doglegs or poor hole cleaning, orientation angle may not be reliably achieved.

| Mechanical Jet Orientation:

1. Low precision, cannot ensure accurate alignment to the target direction;
2. Sensitive to well trajectory, tool/casing size fit, and friction between tool and casing must be precisely matched.

| Hydraulic Jet Orientation:

1. More complex tool structure;
2. Slightly higher cost.

Conclusion

Directional hydraulic sandblasting perforation provides a precise, controllable, and formation-friendly method to initiate reservoir contact in horizontal wells. By enabling azimuthal targeting and reducing mechanical or explosive damage, this technology significantly improves stimulation efficiency, well integrity, and production performance in complex reservoir environments.

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