Page 87 - Intelligent Digital Oil And Gas Fields

58 Intelligent Digital Oil and Gas Fields

• Flow after separation system: This system measures oil and water directly at
the tank; gas is measured using an orifice meter. Important measurements
are derived from this data including the gas-oil ratio (GOR), the water
cut (ratio of water to liquid), and liquid-gas ratio (LGR). Frequently, oil
and water density are measured using centrifuge principles, and gas den-
sity is measured using correlations.

2.1.3.6 Multiphase Flowmeter
A multiphase flowmeter is an alternative to separators and individual fluid
meters is a three-phase meter. MPFM removes the need and expense of a
separator and three individual flowmeters and replaces that equipment with
a single, but more expensive, single meter. The technology for these types of
meters is rapidly progressing, including nuclear and sonic-type meters. As
with Coriolis meters, pricing has become reasonable for many applications.
An MPFM is generally placed after the wellhead and before a separation sys-
tem, which allows for better MPFM utilization than placing it after the sep-
aration system. To allow gravity to separate the phases and generate uniform
bubble flow pattern, the MPFM should be set up in a vertical upflow posi-
tion. Fig. 2.11 shows the main components of an MPFM, which are listed
below:
• Venturi meter measures the total mass flow and bulk velocity by differ-
ential pressure.
• Dual-energy γ-ray densitometers or neutron interrogation is a detector
to measure phase fraction and mixture density and features. This non-
intrusive device directly measures the density of a mixed fluid. It is able
to separate the liquid from the gas phase by measuring the atomic veloc-
ities of oxygen and hydrogen.
• Infrared meter is an electronic detector that measures the capacitance of
water in an oil-dominated flow. Also a nonintrusive device, it estimates
the water cut or the amount of fraction of water volume in the total
liquid.
• Inductance and capacitance meters are electronic devices that measure
water conductivity and resistivity, respectively.
• Gas composition meter estimates the percentage of hydrocarbon com-
+
position (e.g., C1, C2, C3 up to C7 ) in a gas stream.
A new generation of MPFM can also measure other critical properties, such
as solution pH, water salinity, wax content in oil, gas gravity, and oil gravity;
estimate the flow regime; and calculate Reynolds, Bond, and gravity num-
bers, and the solid content in fluids.