Parametric Investigation of Fluid Migration in Casing-Liner Cement Sheaths and Microannulus Using Computational Fluid...

Area of Science:

• Petroleum Engineering
• Fluid Dynamics
• Geology

Background:

• Cement sheath integrity is crucial for wellbore stability and preventing fluid migration.
• Microannuli formation in casing-liner overlaps can compromise zonal isolation.
• Understanding fluid leakage dynamics is essential for effective well design and risk management.

Purpose of the Study:

• To develop a computational fluid dynamics (CFD) model for fluid leakage through cement sheaths in casing-liner overlaps with microannuli.
• To investigate the impact of various parameters on fluid leakage rates under transient conditions.
• To provide insights for optimizing cement sheath properties and well configurations.

Main Methods:

• Development of a fluid dynamic model based on Darcy's law for transient flow.
• Simulation of fluid leakage through a cement sheath with a microannulus in the casing-liner overlap.
• Parametric study analyzing the effects of permeability, porosity, microannulus size, overlap length, pressure, and temperature.

Main Results:

• Increased permeability, larger microannuli, and shorter overlap lengths significantly enhance fluid leakage rates.
• Lower porosity adversely affects leakage, while high operating pressures substantially increase flow rates.
• Fluid compressibility amplifies leakage at high pressures due to gas expansivity, especially under transient conditions.

Conclusions:

• The developed model accurately predicts fluid leakage dynamics in casing-liner overlaps.
• Optimizing cement sheath properties (e.g., permeability, porosity) and overlap design is critical for well integrity.
• Understanding the influence of pressure and fluid compressibility is vital for managing leakage risks in oil and gas wells.