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The Multiphase Flow Meters Rule In Well Pad Central Processing

  December 2016 / January 2017

The Mulitphase Flow Meters Rule in Well Pad Central Processing
By: Vince Giangarlo, Giangarlo Scientific

Traditionally the multiphase flow metering was carried out by large separator vessels where gravity separated the liquid and the gas. In these systems single phase flow meters were needed to measure output of each phase. This measurement often was not in real time and could not adapt to changes in well production.

Now, many shale producers have multiple wells per pad configurations and are moving to a central processing facility handling multiple pads. The Multiphase flow meter is being used for well testing at the individual pads eliminating well test separators and relief valves at the pad locations.

midstream_2_decjanThis makes reservoir management a lot easier and gives the operators an additional tool for evaluating the efficiency of the separators. As the reservoir ages, operators can conveniently add identifiable secondary flows that are now measured by multiphase flow meters without the need for more separators. Most producers report improvements in well test accuracy and field allocation factors.

One advanced system offered by Agar Corporation is not affected by changes in viscosity, temperature, pressure and contains no radioactive sources/nuclear sources. This system does not use gamma ray devices and is not affected by salinity value shifts experienced with gamma ray spectroscopy devices.

The AGAR MPFM uses a combination of Agar Coriolis and momentum meters (dual venturi meter) to solve the equations for Multiphase Flow Measurement. There is periodically some confusion when discussing Gas Volume Fraction and Gas Void Fraction. Gas void fraction (GVF) is calculated as the ratio of the cross-sectional area of gas when compared to the total cross-sectional area of the pipe. The gas volume fraction is a ratio of the gas volume flow rate compared to the total volume flow rate.


The Agar Multiphase Flow Meter (MPFM-50) solution

The Agar MPFM-50 is a complete system that integrates commonly used oilfield measurement technologies. Agar combines these devices to accurately measure the flow rates for oil, water and gas in a multiphase environment. The Agar MPFM-50 consists of 5 major components as shown in Figure 1:
A. Coriolis meter
B. Agar OW-200 water cut meter
C. Agar ID-201 interface detector
D. Dual venturi meter
E. Pressure transmitters

midstream_1_decjan
Agar has developed a coriolis meter able to handle the full range of GVF with very low operating differential pressure (DP). Agar has designed a new controller for its coriolis which is able to provide the linear response required to accurately measure the mass flow and multiphase density using the coriolis effect in a ‘straight pipe’ design.

In order to determine both the GVF and the total flow under high GVF conditions (above 25%), it is necessary to combine the coriolis reading with a second flow device.

midstream_3_decjanThe Agar momentum meter consists of a venturi section used to determine real-time flow rates of liquid and gas.  Its principle of operation uses fundamental knowledge from fluid mechanics and numerical methods. The differential pressures are measured relative to their corresponding inlet pressures.

By combining the venturi with the density input from the coriolis, a second mass flow is determined. It is used to determine the slip ratio by solving the differential equations of the mass flows measured by both flow devices (coriolis and venturi). The Agar coriolis combined with the Agar momentum meter (dual venturi) allows for measurement of the total flow and GVF in real time. By using the GVF and total flow, the MPFM can calculate the liquid flow rate and the flow rate of the gaseous phase.

Accuracy compared to test separators and test tanks and other test equipment.

Eagle Ford, Bakken, & Niobrara: 
The AGAR MPFM-50 has provided accurate results in the multiple unconventional shale plays compared to results from test tanks, even where the Gas Void Fraction was over 95% and the oil was foamy. Agar instruments were utilized to provide Oil, water and gas flow rates, water cut, Gas Void Fraction (GVF), Gas Oil Ratio (GOR), Pressure & Temperature. The outstanding performance showed accurate averaged results for the water cut and liquid measurement on the MPFM-50 were within 5%

midstream_4_decjanRemote sites:
The MPFM-50 combined with a wireless connection comes in a portable unit suitable for well testin in satellite sites where a MCC or DCS terminal is not available. The remote connectivity feature provides access from the office to the meter at any time and in real time.

Summary:
The AGAR MPFM-50 enables production engineers to optimize the performance of the well production with real time monitoring. As a well testing tool it can eliminate the need for additional tanks and separators. The MPFM -50 provide can reduce capital expenditures and reduce operating costs for the short and long term.

About the Author:
Agar Corporation is represented locally by Giangarlo Scientific in the Marcellus and Utica Shale Regions of the United States.

Please contact:
Oil and Gas Instrumentation Group
Giangarlo Scientific Company
162 Steuben Street
Pittsburgh, PA 15220
Office: 800-229-8850
www.giangarloscientific.com

Vince Giangarlo
Agar Manufacturer’s Representative
Sales@giangarloscientific.com