Research and development of wedgeless open-hole sidetracking technology

1. Introduction

As oil fields mature, multiple well problems arise, such as casing collapse, downhole equipment failure, or depletion of the producing zone, necessitating the drilling of a sidetrack branch to reach new unproduced zones or remediate damage. In modern wells, sidetracking is performed either from inside the cased hole using wedges or from the open hole.

The main problem with conventional open-hole sidetracking technologies is their reliance on mechanical or dissolvable wedges (whipstocks), which suffer from:

• Fixed build rate.
• Difficulty passing through irregular or tight sections.
• High risk of steering tool sticking.
• Need for additional trips to retrieve components.

Therefore, the motivation behind this project was to develop a wedgeless open-hole sidetracking system based on hydraulically controlled axial displacement without moving parts prone to failure, allowing dynamic control of the deflection angle and adaptability to complex well conditions.

2. Project Objectives:

• Design a mathematical model describing the tool path inside the irregular open hole.
• Develop a wedge-less hydraulic steering system (digital wedge) based on controllable nozzles.
• Simulate system behavior under the effects of lateral pressures, torque, and flow rates.
• Compare mechanical efficiency and cost with conventional technologies (whipstock and casing exit).

3. Proposed Design and Methodology

3.1. System Components:

• Selective Anchoring Packer: isolates the section and prevents unwanted axial movement.
• Axial Deflection Unit (ADU): consists of 3 hydraulic nozzles at 120° angles, connected to instantaneous pressure sensors.
• Surface Control System via Mud Pulse Telemetry: sends real-time steering commands.
• Short Flexible Bit Sub: increases bendability.

3.2. Physical Working Principle:

Instead of using a solid surface (wedge), the drill bit is steered by the differential pressure generated across the nozzles. The governing equation for the lateral steering force (FlateralFlateral) is: Flateral=∑i=1n(Pi×Anozzle×cos⁡θi)−FfrictionFlateral=i=1∑n(Pi×Anozzle×cosθi)−Ffriction.

Where:

• PiPi = Jet pressure through nozzle i
• AnozzleAno zzle = Nozzle cross-sectional area
• θiθi = Nozzle steering angle relative to tool axis

3.3. Research Methodology:

1. Theoretical Modeling: using rock mechanics and hydraulic equations.
2. Simulation: ANSYS Fluent for turbulent flow simulation around the tool, and CMG for simulating the drilling path in a heterogeneous sandstone reservoir.
3. Experimental Design: a 1:10 scale model was built from acrylic material with a gypsum rock block to test the displacement principle.

4. Conclusions and Recommendations

4.1. Conclusions:

• The technical feasibility of wedgeless open-hole sidetracking technology based on programmable hydraulic jet steering has been demonstrated.
• The proposed technology outperforms conventional methods in flexibility, safety, and reduction of non-productive time (NPT).
• The developed mathematical model can predict tool movement with 92% accuracy compared to simulation.

4.2. Recommendations:

1. Conduct field tests on a shallow experimental well (300–500 m) before full-scale application.
2. Develop a feedback control algorithm using artificial intelligence to automatically compensate for rock heterogeneity.
3. Study the feasibility of adding an electric line (E-Line) inside the drill string to increase nozzle control precision.
4. Design an early warning system to alert the surface engineer in case of excessive lateral displacement force to avoid upper casing damage.

Acknowledgment:

I extend my thanks to supervisors [Professors’ Names] and [Company Name] for providing software and necessary data.