Real time flow rate and rheology measurement

1 . A flow measurement apparatus, comprising:

a main flow passage having a first flowmeter;

a bypass flow passage connected in parallel with the main flow passage, the bypass flow passage having a first flow restrictor, a second flowmeter, and at least one first sensor configured to measure a first pressure differential across the second flowmeter, the second flowmeter comprising a mass flowmeter, in which the first flowmeter is connected in the main flow passage one of upstream of the bypass flow passage and downstream of the bypass flow passage; and

a control system configured to determine at least one rheological parameter of a non-Newtonian fluid based on outputs of the at least one first sensor and the second flowmeter when a flow rate of the non-Newtonian fluid is greater than 100 gallons per minute, in which the control system is configured to determine the at least one rheological parameter of the non-Newtonian fluid based on an output of the first flowmeter when the flow rate of the non-Newtonian fluid is less than or equal to 100 gallons per minute.

2 . The flow measurement apparatus of claim 1 , further comprising:

a second flow restrictor located in the main flow passage between an inlet and an outlet of the bypass flow passage; and

at least one second sensor which measures a second pressure differential across the second flow restrictor,

wherein the control system is further configured to determine a total flow rate through the main flow passage and the bypass flow passage based on the rheological parameter and the outputs of the at least one first sensor, the at least one second sensor, and the second flowmeter.

3 . The flow measurement apparatus of claim 2 , in which the at least one second sensor comprises a differential pressure sensor connected to upstream and downstream sides of the second flow restrictor.

4 . The flow measurement apparatus of claim 2 , in which the at least one first sensor comprises a differential pressure sensor connected to upstream and downstream sides of the second flowmeter.

5 . The flow measurement apparatus of claim 1 , in which the second flowmeter is positioned in the bypass flow passage upstream of the first flow restrictor.

6 . The flow measurement apparatus of claim 1 , in which the first flow restrictor is positioned in the bypass flow passage upstream of the second flowmeter.

7 . The flow measurement apparatus of claim 1 , in which the first flow restrictor is a variable flow restrictor.

8 . The flow measurement apparatus of claim 7 , in which the variable flow restrictor is configured to vary a restriction to flow through the bypass flow passage, thereby maintaining a flow rate through the second flowmeter within a predetermined range.

9 . The flow measurement apparatus of claim 1 , in which the second flowmeter comprises a Coriolis flowmeter.

10 . The flow measurement apparatus of claim 1 , in which the control system comprises instructions for determining the at least one rheological parameter.

11 . The flow measurement apparatus of claim 1 , in which the control system comprises instructions for determining a total rate of fluid flow through the flow measurement apparatus.

12 . A method for measuring a rheological fluid property of a non-Newtonian fluid, comprising:

measuring a volumetric flow rate through a first flowmeter connected in a main flow passage;

measuring a first differential pressure across a second flowmeter in a bypass flow passage, the second flowmeter comprising a mass flowmeter, in which the first flowmeter is connected in the main flow passage one of upstream of the bypass flow passage and downstream of the bypass flow passage;

measuring a mass flow rate through the bypass flow passage;

determining the rheological fluid property of the non-Newtonian fluid from the first differential pressure and the mass flow rate through the bypass flow passage when a flow rate of the non-Newtonian fluid is greater than 100 gallons per minute; and

determining the rheological fluid property of the non-Newtonian fluid from the volumetric flow rate through the first flowmeter when the flow rate of the non-Newtonian fluid is less than or equal to 100 gallons per minute.

13 . The method of claim 12 , further comprising:

connecting a flow measurement apparatus between an outlet of a pump and an inlet of a tubular string extending into a well, the flow measurement apparatus comprising the main flow passage, the bypass flow passage being connected in parallel with the main flow passage and having a first flow restrictor and at least one first sensor which measures the first pressure differential across the second flowmeter, and the main flow passage having a second flow restrictor and at least one second sensor which measures a second pressure differential across the second flow restrictor.

14 . The method of claim 13 , in which the determining comprises determining the rheological fluid property based on outputs of the at least one first sensor and the at least one second sensor.

15 . The method of claim 13 , further comprising:

determining a total rate of fluid flowing into the tubular string based on an output of the second flowmeter and the determined rheological fluid property.

16 . The method of claim 15 , further comprising:

varying at least one of an output of the pump and a restriction to flow through a choke manifold based on the determined total rate of fluid flowing into the tubular string.

17 . The method of claim 13 , in which the second flowmeter is positioned in the bypass flow passage upstream of the first flow restrictor.

18 . The method of claim 13 , in which the first flow restrictor is positioned in the bypass flow passage upstream of the second flowmeter.

19 . The method of claim 13 , in which the first flow restrictor is a variable flow restrictor.

20 . The method of claim 19 , further comprising varying a restriction to flow through the bypass flow passage, thereby maintaining a flow rate through the second flowmeter within a predetermined range.