Page 86 - Intelligent Digital Oil And Gas Fields

Instrumentation and Measurement 57

non-homogenized condition; therefore, a mixer device must be used to
equalize the flow velocity and estimate the mixture density. The follow-
ing equipment combinations can be used before a separation system, but
this configuration requires human intervention and constant device
calibration:
2 Two densitometers plus velocity: requires a meter to measure total
velocity (turbine), a densitometer to measure mixture density, and
second, a densitometer to measure oil phase density at the separation
test system. Additionally, oil, water, and gas-phase voids can be esti-
mated with a mathematical procedure. This is a less expensive option
but sometimes is not practical. This option cannot measure the
gas rate.
2 Velocity plus momentum requires one meter to measure the total
velocity and an orifice meter (differential pressure) to measure the
gas rate. This is also an inexpensive option; however, it cannot mea-
sure the phase densities and cannot distinguish oil from water.
2 Momentum plus density: Gas rate flow and fluid average density can
be obtained, but need another densitometer after the separator to
measure oil density. A Venturi meter can measure the fluid momen-
2
tum (ρ.v ), and a densitometer can measure density of the total fluid.
Use a mathematical calculation to get fluid velocity (v).
2 Interrogation rays plus mass flow: Using a Coriolis meter, the total
flow rate can be estimated with high precision. This meter combined
with a neutron interrogation or infrared ray can estimate water cut in
the bulk current and therefore quantify the oil and water rate. How-
ever, this option does not measure the gas rate, and it can be very
expensive and inaccurate if GVF is higher than 0.8.
• Non-homogenization, measurement, and separations: generally placed before
a separation system. The fluid components flow at different velocities, so
the phase velocity must be measured separately as well as volumetric
composition and its respective density (no mixture). This scenario
requires quite expensive devices and sometimes environmentally sensi-
tive sources, such as neutron interrogation, to calculate the amount of
oxygen and hydrogen present in the flow current, in addition to a pulse
neutron activation to measure both oxygen and hydrocarbon atomic
velocities. Additionally, a γ densitometer is required to measure the mix-
ture density fluid. The MPFM falls under these categories:
2 Bulk flow phases plus phase velocity.
2 Phase density and water cut.