Patent attributes
A closed-loop hydraulic drilling system generates choke characteristic curves or data that more accurately reflects the relationship between the commanded choke valve position and the resulting pressure drop across the choke valve for a given flow rate and fluid density. The choke characteristic curves may be generated through a calibration procedure and then used during normal operations to more accurately monitor return flow and manage wellbore pressure. The specific gravity of an injected calibration fluid and pressure drop across the choke valve may be determined and correlated to the current choke valve position to reflect the choke characteristic curve in situ, thereby providing for more precise control of wellbore pressure and enabling condition monitoring of the choke valve. In addition, an improved closed-loop hydraulic drilling system does not require a flow meter, enabling the adoption of MPD systems in low-specification and economically constrained applications.
