Coriolis flow meter having flow tube with equalized pressure differential

A controlled pressure drilling system for a wellbore, the drilling system conducting flow of drilling fluid, the drilling fluid having gas, liquid, and/or solids and being at a first pressure level for drilling the wellbore, the system comprising:

• at least one choke in fluid communication with the wellbore and controlling the flow of the drilling fluid from the wellbore;
• and
• a Coriolis flow meter disposed in fluid communication upstream of the at least one choke and measuring the flow of the drilling fluid from the wellbore, the Coriolis flow meter comprising:
• at least one flow tube being adapted to vibrate and conducting the flow of the drilling fluid at the first pressure level from an inlet side to an outlet side, the at least one flow tube configured to withstand a pressure limit, of internal pressure relative to atmospheric pressure, that is less than the first pressure level of the drilling fluid to which the at least one flow tube is exposed;
• a vessel enclosing the at least one flow tube in a chamber and holding an internal fluid separate from the drilling fluid at a second pressure level in the chamber about the at least one flow tube;
• and
• a controller monitoring variation in the first pressure level of the drilling fluid conducted through the at least one flow tube, the controller regulating the second pressure level of the internal fluid relative to the first pressure level and controlling a pressure differential across the at least one flow tube to conduct the drilling fluid at the first pressure level above the pressure limit of the at least one flow tube.

A drilling system for a wellbore, the drilling system conducting flow of drilling fluid, the drilling fluid having gas, liquid, and/or solids and being at a first pressure level for drilling the wellbore, the system comprising:

• at least one pump in fluid communication with the wellbore and delivering the flow of the drilling fluid to the wellbore;
• and
• a Coriolis flow meter disposed in fluid communication between the at least one pump and the wellbore and measuring the flow of the drilling fluid to the wellbore, the Coriolis meter comprising:
• at least one flow tube being adapted to vibrate and conducting the flow of the drilling fluid at the first pressure level from an inlet side to an outlet side, the at least one flow tube configured to withstand a pressure limit, of internal pressure relative to atmospheric pressure, that is less than the first pressure level of the drilling fluid to which the at least one flow tube is exposed;
• a vessel enclosing the at least one flow tube in a chamber and holding an internal fluid separate from the drilling fluid at a second pressure level in the chamber about the at least one flow tube;
• and
• a controller monitoring variation in the first pressure level of the drilling fluid conducted through the at least one flow tube, the controller regulating the second pressure level of the internal fluid relative to the first pressure level and controlling a pressure differential across the at least one flow tube to conduct the drilling fluid at the first pressure level above the pressure limit of the at least one flow tube.

A drilling method for a wellbore, the method comprising:

• conducting flow of drilling fluid in a drilling system, the drilling fluid having gas, liquid, and/or solids and being at a first pressure level for drilling the wellbore;
• measuring the flow by vibrating at least one flow tube of a Coriolis flow meter conducting the flow from an inlet side to an outlet side, the at least one flow tube configured to withstand a pressure limit, of internal pressure relative to atmospheric pressure, being less than the first pressure level of the drilling fluid to which the at least one flow tube is exposed;
• and
• controlling, with a controller, a pressure differential across the at least one flow tube to conduct the drilling fluid at the first pressure level above the pressure limit of the at least one flow tube by monitoring variation in the first pressure level of the drilling fluid conducted through the at least one flow tube and regulating, relative to the first pressure level, a second pressure level of an internal fluid separate from the drilling fluid in a chamber of a vessel disposed about the at least one flow tube.