The DataSphere® FloStream flowmeter is designed specifically to meet the requirements of the well in relation to material selection and expected flow rates. FloSteam flowmeter system operation is based on the Venturi principle, a concept first demonstrated by Italian engineer Giovanni Battista Venturi in 1797, and first put into practical use nearly a century later, in 1887, by Clemens Herschel.
The FloStream flowmeter employs two ROC™ permanent downhole gauges (PDGs) to measure absolute pressures at the Venturi inlet and the throat. A Venturi tube is a device consisting of a conical, convergent inlet connected to a cylindrical restriction (called the “throat”) and a divergent conical section, which allows the pressure drop to be recovered. When flow occurs through the Venturi, there is a drop in pressure between the inlet and the throat sections. If pressure measurements are made at the inlet and the throat, the pressure drop can be measured directly. The pressure drop can then be related to mass flow rate.
The FloStream flowmeter uses the same modular design as the Halliburton dual-gauge mandrels; i.e., exactly the same gauges, mounting arrangements and terminations. The downhole cable, cable protectors, connectors, and subsea control system interface are identical between flowmeter and standard gauge systems.
In addition, the time required and the procedures followed during run-in-hole for both systems are also identical. The difference is on the inside bore of the mandrel, where a Venturi profile is either machined or a wireline retrievable section installed.
The wireline retrievable section allows for the following:
Changing of the Venturi profile should the flow rate change significantly
Removal of the restriction imposed should it become necessary to carry out some well maintenance operation below the flowmeter
Replacement should the Venturi profile become worn
Depending on completion design, there may be a wireline run required to set the Venturi after the completion is landed, but if no wireline work is required below the flowmeters, the Venturi can be installed in the mandrel prior to run-in-hole.
The lock profile and seal bores for the Venturi section are machined in the production bore of the mandrel. The Venturi is then suspended from this lock to allow insertion or removal of the Venturi using standard wireline running tools.