A Semianalytical Model for Advanced Description of Pressure Drop Funnel during Coalbed Methane Production

Area of Science:

• Petroleum Engineering
• Reservoir Engineering

Background:

• Accurate pressure drop funnel description is vital for coalbed methane (CBM) production, especially concerning dewatering and depressurization.
• Understanding production status and potential is key for responsible CBM development.

Purpose of the Study:

• To present a semianalytical model for describing the dynamic pressure drop funnel in CBM wells.
• To improve the precision of CBM production forecasting and resource assessment.

Main Methods:

• Integration of pressure profiles and material balance equations.
• Incorporation of inner/outer boundary conditions and dynamic reservoir characteristics.
• Validation using field data from two CBM wells.

Main Results:

• Dynamic water saturation significantly influences drainage radius expansion, surpassing desorption radius effects for accurate boundary prediction.
• Rapid bottomhole pressure drops lead to smaller production boundaries and reduced well-controlled resources.
• Optimal production strategies promote larger drainage radii and efficient pressure drop funnel propagation.

Conclusions:

• The developed model accurately computes dynamic CBM resources and recovery efficiency.
• It provides a valuable tool for assessing productivity potential in undersaturated CBM reservoirs.
• The model offers a time-saving and practical approach for CBM production management.