Multiphase Transient Flow in Wellbore during Shallow Hydrate Reservoir Drilling in Deep Water

Area of Science:

• Geosciences
• Petroleum Engineering
• Chemical Engineering

Background:

• Deepwater drilling in shallow hydrate formations presents unique challenges due to hydrate decomposition.
• Decomposition alters reservoir temperature, wellbore conditions, and creates complex gas-liquid-solid multiphase flow.
• Inaccurate wellbore pressure prediction from these dynamics can lead to hazardous blowout accidents.

Purpose of the Study:

• To investigate the impact of hydrate decomposition on reservoir temperature fields during drilling.
• To analyze the multiphase flow dynamics considering cutting migration and hydrate decomposition in both reservoir and cuttings.
• To evaluate the influence of operational parameters on hydrate decomposition and wellbore stability.

Main Methods:

• Development of a multiphase flow model for deepwater shallow hydrate formations.
• Validation of the model using experimental data.
• Simulation of drilling scenarios to assess the effects of various parameters.

Main Results:

• Hydrate decomposition significantly affects reservoir temperature and wellbore pressure.
• Wellhead backpressure, drilling fluid density, inlet temperature, and rate of penetration (ROP) influence decomposition rate and void fraction.
• Effective inhibition of hydrate decomposition is achieved through specific operational parameter adjustments.

Conclusions:

• Controlling wellhead pressure, increasing drilling fluid density, reducing drilling fluid inlet temperature, and lowering ROP are crucial for inhibiting hydrate decomposition.
• These strategies help reduce void fraction and maintain stable bottom-hole pressure, enhancing drilling safety in hydrate-bearing formations.