Pressure-driven bypass control for higher plug-milling circulation
The diverter valve uses pressure drop across a choke port and a spring-loaded piston to open or close bypass ports automatically. At lower rates, flow goes to the mud motor; above the designed opening range, part of the flow is diverted to the annulus for better debris transport.
Challenge
During plug milling, circulation must power the mud motor, cool the mill, carry plug debris, and clean the wellbore. In fluid-loss or long-lateral conditions, simply increasing pump rate can exceed the motor operating envelope.
Tool solution
The automatic diverter valve balances motor flow and annular circulation. Below the opening range, bypass ports remain closed and flow goes to the motor. As rate increases, the bypass opens automatically and directs additional flow into the annulus.
Validation
Bench tests showed an actual opening range of 350-360 L/min and an approximate 30% bypass ratio at the design condition, consistent with design and simulation. Joint testing showed no significant adverse effect on mud-motor speed, torque, or power.
Field application
In field operation, circulation rate reached up to 610 L/min with stable pressure and flow response. Returned solids increased from less than 5 kg to about 25 kg, and the largest returned debris reached 38 mm.
Review value
The case demonstrates how an automatic downhole diverter valve can increase annular debris transport while maintaining stable mud-motor operation in CT plug milling, fluid-loss, and long-lateral applications.
