Modular Multiphase Flow Meter Wetgas test at CEESI

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1 Modular Multiphase Flow Meter Wetgas test at CEESI Enrico Feltresi, Pietro Fiorentini Federico Lucchini, Pietro Fiorentini Alessio Tonelli, Pietro Fiorentini ABSTRACT Pietro Fiorentini Totem HS, is a 0-100% GVF Multiphase Flow Meter (MPFM) that has been working in regular service onshore and offshore in Multiphase regime through major O&G companies. This paper presents the comparison of the performance obtained with different sensor/model combinations of Wetgas test performed at CEESI Colorado in October The improvements of reliability and cross diagnostic benefits guaranteed by a modular solution are also presented. The MPFM Totem HS MPFM uses a combination of 5 independent measurement principles: Venturi tube, Gamma densitometer, Near Infrared (NIR) Water Liquid Ratio (WLR) detector, Impedance sensor, array Cross Correlation velocity sensor. In order to maximize the Gas/Oil/Water flow rates accuracies, the control system selects the optimal sensor combination and the appropriate mathematical model according to the flow regime. The Wetgas mode employs three sensors and mathematical model combinations: Venturi, gamma density and NIR water fraction meter or velocity sensor, gamma density and NIR water fraction meter and, at the end, a gamma free solution Venturi, velocity sensor and NIR water fraction meter. 1 INTRODUCTION The measurement of different phases in wet gas flow is becoming more important, but also one of the demanding requirements in oil and gas industry. Different methods are available for measuring wet gas flow rate. For example, Venturi flow meters, according the ISO TR standard, are widely used. But they have strong limitations in three phase measurements. Pietro Fiorentini developed a MPFM suitable to work within 0-100% GVF and 0-100% WC. The MPFM integrates five independent measurement techniques: Venturi tube, Quick-Gamma densitometer, Near Infrared WLR detector, Impedance sensor, Cross Correlation flow velocity sensor. The control system selects the optimal sensor combination and appropriate mathematical model according flow regime to maximize the Gas/Oil/Water flow rates accuracies. In particular, specifically for wet gas flow measurements, Pietro Fiorentini developed dedicated metering solution with and without radioactive sources: respectively the Wetgas Meter Xtreme SHS and Xtreme S. In this paper are presented and compared the performances of this two meters in a dedicated wet gas application, also through a blind-test. The data have been 1

collected at the Colorado Experiment Engineering Station Inc. (CEESI) a picture of the installation can be found on Figure 1. Figure 1 Picture of the Installation at The CEESI Laboratory.

2 collected at the Colorado Experiment Engineering Station Inc. (CEESI) a picture of the installation can be found on Figure 1. Figure 1 Picture of the Installation at The CEESI Laboratory. 2 MATHEMATICAL MODEL The mathematical flow model, used in the PF multiphase and wetgas meter, combines the measurement of several modules (Venturi DP, Impedance, NIR WLR, Cross-correlation, Quick-Gamma density, etc.) to determine the three unknowns of interest (Q gas, Q oil, Q water ). The overdetermined system let the model select both an independent way of combining the inputs and the most suitable algorithm to assess the final results. As a consequence, the system uses the additional inputs not only to improve the accuracy of the final results, but also as a self-diagnostic feature to cross-check the performance. 2

3 2.1 Algorithm The leading equations involved in the mathematical model are listed below: = ( 1 ) Q =Area (1 GVF) Velocity ( 2 ) = ( 3 ) = ( 4 ) = (1 ) ( 5 ) = ( 6 ) = (1 )+ ( 7 ) = (1 )+ ( 8 ) = (, ) ( 9 ) =, ( 10 ) = (, ) ( 11 ) =, ( 12 ) The mathematical flow model determines the variables below reported in the following sequential order: first WLR, then GVF, Q liq and at the end Q gas. Each of them can be calculated independently using different algorithms: WLR determination Name Modules Method WLR 1 NIR WLR The NIR WLR meter will measure the WLR directly WLR 2 Impedance QGamma The combination of Impedance (capacitance or conductance) and the Qgamma density will determine both the WLR and GVF at the same time ( using equation 7, 8, and either 9 and 10 or 11 and 12). WLR 3 Impedance X-Corr Velocity Venturi DP GVF determination The WLR is found by combining the Impedance, the x- correlation velocity and the Venturi DP (using equation 1, 4, 7, 8, and either 9 and 10 or 11 and 12). Name Modules Method GVF 1 Impedance The GVF is calculated using equations 9 and 10 or 11 and 12 with the impedance inputs. 3

4 GVF 2 GVF 3 QGamma (WLR 1) X-Corr Velocity Venturi DP The density from the QGamma can be used to determine the GVF by using equation 7 and 8. Combining the Impedance, the x-correlation velocity and the Venturi DP, the GVF is found Qliq determination. Name Modules Method Qliq 1 Venturi The Qliquid can be found by using the WLR, GVF and the Venturi DP by combining equations 4, 5 and 6. Qliq 2 X-Correlation The Qliquid can be found by using the WLR, GVF and the X-Correlation velocity by using equations Qgas determination. Name Modules Method Qgas 1 Venturi The Qgas can be found by using the GVF and the Venturi velocity by combining equations 4, 5 and 6. Qgas 2 X-Correlation The Qgas can be found by using the GVF and the X- Correlation velocity by combining equations 1, 2 and 3. Figure 1 Block Diagram of the PF mathematical model. Based on the available inputs (e. g. Gamma-Density, DP, etc.), i.e. the modules on the physical meter in use, the most effective combination of algorithm is selected. This diagram (Figure 1) shows immediately the benefits of the redundancy in case of failure of one input: there is more than one path/method to reach the final results. 4

5 3 Test Facility The experimental test has been performed at the CEESI Wet Gas Facility in Colorado USA before the 2015 winter shutdown (October 2015), see a block diagram of the flow loop facility on Figure 2 and the specification can be found on Table 1. Figure 2 CEESI Wet Gas Flow Loop block diagram. Laboratory Specification Gas Media Natural gas Liquid Media Exxsol D80, Freshwater Test Section Pipe Size 4 Sch 80 Pressure 10 to 75 bara Temperature 21 to 38 deg C Gas Flow Rate 325 to 1800 m3/hr Exxsol D80 Flow Rate to 25 m3/hr Water Flow Rate to 25 m3/hr Water Cur Range 0% to 100% Table 1 CEESI 4 Wetgas Flow Loop Specification 5

6 3 DATA The data collected has been selected inside the envelope of the meter ranging from 0% to 100% WLR and GVF greater than 90% as shown on Figure 3. Figure 3 On the plot on the top side is shown the distribution of the data collected as function of liquid flow rate and gas flow rate, grey dots are data, the blue line is the operating envelope for the meter. On the plot on the bottom side is shown the distribution of the data collected during the test as function of WLR and GVF. 6

7 4 TEST RESULTS South East Asia Flow Measurement Conference The results of the test performed at CEESI are reported below for Gas and liquid Flow Rate, then the WLR is shown. Each model is presented separately. 4.1 Gas Flow Rate The results for the Gas flow rate are reported for the Xtreme SHS on Figure 4 as function of the Flow Loop reference, for the Xtreme S can be found on Figure 5. Figure 4 On the left-hand side plot is reported the Gas Flow Rate measured versus the Flow Loop Reference, yellow square are the data, the dashed line are representing an uncertainty of 4%. On the right-hand side plot is shown the Gas Flow rate deviation from reference as function of GVF, yellow square are data the dashed line show the uncertainty. Data are collected with the Xtreme SHS. Figure 5 On the left-hand side plot is reported the Gas Flow Rate measured versus the Flow Loop Reference, yellow square are the data, the dashed line are representing an uncertainty of 4%. On the right-hand side plot is shown the Gas Flow rate deviation from reference as function of GVF, yellow square are data the dashed line show the uncertainty. Data are collected with the Xtreme S. 7

8 4.2 Liquid Flow Rate South East Asia Flow Measurement Conference The results for the liquid flow rate are reported for the Xtreme SHS on Figure 6 as function of the Flow Loop reference, for the Xtreme S can be found on Figure 7. Figure 6 On the left-hand side plot is reported the Liquid Flow Rate measured versus the Flow Loop Reference, grey squares are the data, the dashed line are representing an uncertainty of 12%. On the right-hand side plot is shown the liquid Flow rate deviation from reference as function of GVF, grey squares are data the dashed line show the uncertainty. Data are collected with the Xtreme SHS. Figure 7 On the left-hand side plot is reported the Liquid Flow Rate measured versus the Flow Loop Reference, grey squares are the data, the dashed line are representing an uncertainty of 12%. On the right-hand side plot is shown the Liquid Flow rate deviation from reference as function of GVF, grey squares are data the dashed line show the uncertainty. Data are collected with the Xtreme S. 8

9 4.3 Water liquid ratio results The Water liquid ratio performance was the same for both models. The Xtreme meters uses the same Near Infrared WLR detector. The results are reported on Figure 8 as function of the Flow Loop reference. Figure 8 On the left-hand side plot is reported the WLR measured versus the Flow Loop Reference, blue squares are the data, the dashed line are representing an uncertainty of 4%. On the right-hand side plot is shown the WLR deviation from reference as function of GVF, blue squares are data the dashed line show the uncertainty. 4.4 Performance comparison The following table (Table 2) shows a comparison of the performances of the two models. Qgas [%] Qliq 90<GVF<99 GVF>99 Xtreme S ± 4.0 ± 4.3 Xtreme SHS ± 3.0 ± 4.2 [m 3 /h] WLR [%] Xtreme S ± 3.6 ± 5.4 Xtreme SHS ± 1.1 ± 1.5 Xtreme SHS & S ± 3.0 ± 3.8 Table 2 Performance comparison for the two models under test: Xtreme S and Xtreme SHS. In the table are reported the accuracy at 90% Confidence Level in different ranges of GVF. 9

10 5 CONCLUSION South East Asia Flow Measurement Conference The Xtreme S and Xtreme SHS were able to provide accurate measurements in the whole range of wet gas conditions. The WLR measurement even at high GVF was accurate within the ±4%. The uncertainty in Gas flow rate were for both models less than 4%. The measurement principles used in the meters are well established and widely used in the oil & gas industry, but the novel idea presented in this paper is the improvements due to reliability and the benefits of a cross diagnostic system guaranteed by a modular solution. The benefits of a multi-modular (Xtreme SHS) solution can clearly be seen in the better performances as compared with the Xtreme S (non-radioactive), e.g. as shown in the uncertainty of the liquid flow rate. Moreover the multiple sensing solution (Xtreme SHS) guarantees the performance even in case of failure of one module. 6 NOTATION Area GVF WLR DP Velocity ρ ϵ σ cross section area of the meter in-situ gas fraction Water liquid ratio delta pressure across the Venturi throat for simplicity slip and other flow regime effects are neglected density permittivity conductivity 10

Diagnostic System for Venturi Meters

Diagnostic System for Venturi Meters Richard Steven, DP Diagnostics PO Box 121, Windsor, Colorado, 80550, Colorado Tel: 1-970-686-2189, e-mail: rsteven@dpdiagnostics.com 1. Introduction Venturi flow meters