Development of a Hydraulic Circulation Sub as a Tool to Prevent Mud Losses During Well Drilling

Fractured and cavernous rocks, as well as rocks with increased permeability, are prone to mud losses during oil and gas well drilling. Circulation subs are a promising solution to mitigate mud and technological fluid losses in intervals ranging from 5 to 40 m3/h by sealing the problematic interval. However, current circulation subs designs have notable drawbacks, including limited activation capabilities and usage scenario restrictions. This article provides a comprehensive analysis and characterization of the functional use of circulation subs, along with a qualitative comparative market analysis and patent search for devices activated by ball dropping, hydraulic, mechanical, and electromechanical means. The primary outcome of this research is the development of a functional hydraulic quick-acting activation device that addresses the shortcomings of existing designs. The device’s design allow for future development of assemblies and optimization of their configurations to suit specific operating conditions. It can also serve as a protective measure for the downhole motor and telemetry system against harsh mechanical and chemical action during sealing. The device’s limitations include pressure constraints and the need for flow rate adjustment. The article concludes with an overview of the developed hydraulically activated device and the results of qualitative bench tests, which demonstrate its functionality.