Analysis of coalbed methane reservoir damage and wellbore instability and research status of drilling fluid technology

Abstract:

Due to the unique “three-low characteristics” and dual-pore structure of coalbed methane （CBM） reservoirs， they are extremely prone to irreversible damage such as stress sensitivity， water sensitivity， and solid-phase invasion during drilling， and face severe risks of wellbore instability. This paper systematically analyzes the special physical and chemical properties of coal rocks and their specific requirements for drilling fluids， and deeply expounds the damage mechanism of drilling fluids on reservoirs and their impact on wellbore stability. The research progress in CBM drilling fluid technology is mainly reviewed： for reservoir protection， core technologies such as low-density drilling fluids， strong inhibition-plugging systems， low-solids/no-solids drilling fluids， and degradable drilling fluids have been formed； for wellbore stability， anti-collapse drilling fluid systems based on multi-component synergistic inhibition and high-efficiency plugging have been developed. The paper summarizes the current technical challenges and points out that future research should focus on geological adaptability， intelligent-responsive drilling fluids， high-efficiency environmental protection materials， etc.， to provide a reference for optimizing CBM drilling fluid technology and improving development benefits.