Upload
hadiep
View
224
Download
1
Embed Size (px)
Citation preview
Paper 1.4
EXPERIENCES WITH THE MASTER METERING PRINCIPLE AND ULTRASONIC FLOWMETERS
AT OFFSHORE LOCATIONS (FPSO’s)
John Thorogood KROHNE Oil & Gas
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
1
Experiences with the Master Metering Principle and Ultrasonic Flowmeters at Offshore Locations (FPSO’s)
John Thorogood, KROHNE Oil & Gas
1 INTRODUCTION
This paper looks at the operating experiences when using multi path liquid ultrasonic meters
for custody transfer duties offshore. The performance of the duty meters have been checked
with a master meter, which has either been proved in situ or returned to a flow test laboratory.
Results presented in this paper demonstrate the long term stability and high confidence in the
measurement results.
2 FPSO’s
Mobile production units such as FPSO’s (Floating Production, Storage and Offloading
vessels) have become increasingly popular for offshore applications. FPSO’s are mostly used
for smaller oil fields and deepwater oils fields. South East Asia (e.g. Singapore and Korea)
has become the centre for building new FPSO’s and converting oil tankers. South East Asia is
also one of the regions with the highest concentration of mobile offshore production units and
many more will go into operation in the future.
Limited space and weight are important restrictions set by end-users for flow metering
systems on any offshore application and particularly for mobile offshore production units.
Because of the limited accessibility to offshore locations for service and repair, high standards
are set on the quality of flow metering systems. Flow meters should be highly reliable and
require a minimum of maintenance. To save space, end users prefer not to install mechanical
provers offshore. In addition, flow meters or provers should never block the line.
Not surprisingly ultrasonic flowmeters have become increasingly popular for FPSO’s and for
offshore applications in general. The applications vary from fiscal metering to allocation
metering, production metering, export metering, metering of crude oil and seawater after the
separators, well water injection, offloading and shuttle tanker loading. The flowmeters, based
on the transit time principle, have a rugged construction, a large dynamic range, are easy to
install without filters, measure independent of product properties and require minimal
maintenance as they have no internal moving parts.
2.1 Where Is The Custody Transfer Point?
There are a number of different operating scenarios for fiscal authorities when it comes to the
actual point of custody transfer point.
Factors that can affect this point are:
Terms of the contract between oil company and FPSO owner/operator
Oil sales contract and actual point of sales
Location of FPSO and territorial waters
2.1.1 Custody transfer onboard the FPSO
The occurs when the oil company usually contracts the FPSO to a fixed term contract for the
vessel and operation of the production facility.
Therefore the fiscal point is determined on the deck of the FPSO as the crude is produced
into the storage tanks. Specifications for the metering and control system are well defined and
the operation of the facility is strictly controlled and monitored.
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
2
Allocation metering upstream of final separation prior to the main fiscal systems can also
occur.
Discharge of the crude to shuttle tankers is still important but usually handled by single cargo
transfer meters.
Custody Transfer onboard of the FPSO
2.1.2 Custody transfer during the discharge from FPSO to shuttle tanker
In this case the field/s are produced with production and allocation metering taking place into
the storage tanks of the FPSO.
Following a period of production the crude is pumped from the FPSO’s tanks through a fiscal
metering system to a shuttle tanker.
This occurs mostly when the oil company is selling the cargo directly from the FPSO and/or
the shuttle tanker cargo is going to be off loaded in another country.
Custody Transfer during Discharge to Shuttle Tanker
2.1.3 Custody transfer at the shore discharge of shuttle tanker load
In this case production /allocation metering and cargo discharge metering take place as the
crude is transferred from the field via FPSO storage to the shuttle tanker.
At the discharge point for the shuttle tanker the crude is measured in accordance with local
authorities.
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
3
The crude can be either measured by an onboard metering system, receipt metering package
or into shore tanks.
This set up is usually adopted when the oil company is operating all stages and the oil doesn’t
leave territorial.
Three Discharge options from the shuttle tanker to shore:
Custody transfer on discharge from shuttle tanker
3 EXPERIENCE WITH UFM OFFSHORE
The first liquid ultrasonic flowmeters for custody transfer have been in operation at various
North Sea platforms for over 10 years. In the mean time ultrasonic flowmeters for fiscal
metering have been installed at offshore locations including FPSO’s loading shuttle tankers all
over the world. In Brazil for example, one of the countries with the largest installed base of
offshore mobile production units, more and more the complete production, allocation, fiscal
and cargo loading measurement of crude oil relies on ultrasonic flowmeters.
Virtually none of the offshore platforms or FPSO’s has installed a permanent prover. In most
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
4
of the applications one multibeam ultrasonic flowmeter (the master meter) regularly or
continuously checks another multibeam ultrasonic flowmeter(s) (the duty meters).
3.1 The Fluminense PFSO
The FPSO Fluminense was converted from one
of the world’s largest tankers. The FPSO is
located in the Bijupira and Salema oilfields in the
Campas Basin, offshore Brazil and some 250 km
East of Rio de Janeiro. Initial production started
in August 2003 with approx 20,000 barrels of oil
per day from one of the 8 production wells
already completed. Production has gradually
increased to the maximum production rate of
80,000 bpd of relatively light crude oil and
associated gas. The FPSO has a storage
capacity of 1.2 million barrels.
3.1.1 Basic Master-Duty Configuration
Basic Master-Duty Configuration of the Fluminense FPSO
The offloading metering facility, shown in the above picture and schematics, consists of 2 off
24” 5 path KROHNE ALTOSONIC V meters set up in a duty master meter configuration.
This facility is designed to measure the crude oil discharge to the shuttle tankers at 5,500
cm/hr although the meters themselves can handle up to 10,000 cm/hr.
3.1.2 Original calibration of the Master meter
The flowmeters were manufactured and tested on water prior to an original hydrocarbon
calibration where the meters were tested against a large Bi-Directional prover (15 cm
volume).
The test results for the original; calibration are given below. Based on these multiproduct
calibrations the meters have their meter factors loaded into their electronics.
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
5
Original Calibration at SPSE in July 2002
According to local regulatory authorities the master meter will need to be returned to the site
of the original calibration. Initially this exercise had to be completed every year but due to
previous projects and data from other recalibrations, the master meter from the Fluminense
was returned for recalibration after three years of operation.
The master meter was retested in the same location and the recalibration results are shown
plotted against the initial calibration. You can see that there is very good correlation with the
original data. Other factors that affect the actual results include the uncertainty of the flow
laboratory/test facility. The meter was well within custody transfer uncertainties over the
complete operating range of the flow meters
-0.50
-0.45
-0.40
-0.35
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200
flow [m3/h]
Error%
Verification1[%]Serial number : 1252691002
Diameter : 584.2mm/24"
Verification 1 : 04-07-2002 SPSE
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
6
Recalibration versus original calibration at SPSE
3.2 Data from in-situ proving using Master Meter
Normal operation for the metering facility is where the flow is passed through the duty meter
only. This provides the FPSO operator with the lowest pressure drop and therefore the
maximum volume throughput with the installed pumping capacity.
Regular metering operation: Oil flows through the custody transfer ultrasonic duty meter.
As we saw from the flow schematic the flow path can be set up to pass the flow through both
meters when installed on site. In this configuration is possible to monitor the performance of
the duty meter against the master meter.
-0.50
-0.45
-0.40
-0.35
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200
flow [m3/h]
Error%
Verification1[%]
Verification2[%]
Serial number : 1252691002Diameter : 584.2mm/24"Verification 1 : 04-07-2002 SPSE Verification 2 : 03-05-2006 SPSE
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
7
During a batch unloading the flow configuration will be set up to evaluate the flow data from
both the master and duty meters
Inline proving. Oil flows through the Master meter and then through the duty meter.
3.3 Metering Consistency
Data has been presented from shuttle tanker loadings from Ticket number 69 on 6th June
2005 to Ticket number 99 on 11th November 2006. You can see that the variation in the
meter factor between the master and the duty meter has been almost constant at .044 %.
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
8
Data obtained on 6th June 05. Multiple proving tickets on individual batch
BatchNo.
Proving Ticket Flow rate MF
BatchNo.
Proving Ticket Flow rate MF
69 213 5746.64 0.996262 69 218 5859.36 0.995348
69 214 5753.69 0.99642 69 218 5888.74 0.995376
69 214 5746.19 0.995713 69 218 5885.87 0.995144
69 214 5743.98 0.995682 69 218 5888.59 0.995525
69 214 5743.78 0.995965 69 218 5890.48 0.995766
69 214 5746.46 0.996339 69 219 5878.67 0.995248
69 215 5742.59 0.996153 69 219 5876.42 0.994958
69 215 5737.97 0.996235 69 219 5878.10 0.995472
69 215 5738.90 0.996255 69 219 5878.87 0.995361
69 215 5739.14 0.996276 69 219 5877.72 0.995441
69 215 5739.12 0.996269 69 220 5922.53 0.995202
69 215 5705.54 0.996538 69 220 5922.06 0.995106
69 216 5819.97 0.996177 69 220 5920.61 0.995105
69 216 5818.74 0.996162 69 220 5922.27 0.995593
69 216 5819.03 0.996525 69 220 5917.55 0.995206
69 216 5819.71 0.996363 69 221 5913.30 0.995377
69 216 5814.61 0.995880 69 221 5911.01 0.995336
69 217 5806.36 0.996289 69 221 5909.85 0.995296
69 217 5838.68 0.995754 69 221 2926.78 0.995938
69 217 5835.96 0.995687 69 221 2887.15 0.995830
69 217 5838.60 0.995781 69 221 2883.30 0.995371
69 217 5836.77 0.995531 69 221 2876.14 0.995636
69 221 2998.65 0.995946
Typical data taken during on shuttle tanker loading batch number 69 with multi proving cycles, proving ticket 213 to
221.
3.4 Further Advantages of the Chosen Master-Duty Configuration
The chosen configuration has the additional advantage that – in the unlikely event that
someone damages duty meters, the Master Meter can be used as a Duty Meter until the Duty
Meter is replace. It also allows the Master Meter to be removed for offsite calibration without
interrupting the metering service.
Failsafe operation: Oil flows through the Master Meter which if needed can act as a duty meter.
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
9
3.5 Conclusion on Fluminense FPSO Project
This data and the recalibration of the master meter at the original flow laboratory after a three
period has demonstrated a very stable meter performance and has given a high degree of
confidence in the overall measurement system and the uncertainties of the crude oil
offloading measurements.
This methodology has been employed in many high capacity measurement systems using
KROHNE Ultrasonic 5 path meters and where no mechanical proving device is feasible. More
than 150 meters have been installed on FPSO’s to date.
4 FIXED PLATFORM MASTER METER
An operator in the North Sea has had two 5 path KROHNE Altometer liquid ultrasonic meters
installed since 1997.
Master-Duty Configuration for the Snorre / Vigdis to Gullfaks custody transfer metering
These meters are installed in a duty master meter configuration with the master meter being
proved in situ with a portable turbine meter/small volume prover calibration device.
Initially the calibration device was brought to the platform every month for recalibrating the
installed ultrasonic meters; since 1999 the meter are only calibrated every year. Data from
1999 to 2006 is attached.
The meters are located on an offshore platform and measure crude oil from two different
fields and with different ownerships, it is therefore essential that the measurement uncertainty
is low and the ultrasonic meters provide long term accuracy with non maintenance
requirements as the platform is unmanned.
There has been no maintenance required on the ultrasonic meters since they were installed is
1997.Turbine meters working on the same fluid have to be removed and cleaned every week
due to scale build up.
The results show excellent stability over a long period of trouble free operation. The ultrasonic
meter factor is within 0.02% for the last four years of recalibration.
6th South East Asia Hydrocarbon Flow Measurement Workshop
7th – 9
th March 2007
10
4.1 Ultrasonic Meter Factor Stability
The most important factor to the operator is long-term meter factor stability. As the graph
shows, the meter factor of the installed meters shows an extremely high level of consistency.
The trust in the meter that stems from such results enabled the operator to dispense with
regular provings and regular maintenance, hitherto unknown with mechanical meters.
Percentage meter factor variation versus time
5 CONCLUSION
Multi path liquid ultrasonic meters have proved themselves to be ideally suited to provide long
term low uncertainty measurements in hostile operating conditions and with minimal
maintenance.
The master meter concept for these devise has demonstrated that it is possible to achieve
very precise measurements without the expenses and space requirements of a large fixed
mechanical provers. The use of multi path liquid ultrasonic meters on FPSO/FSO and
unmanned platforms has brought significant savings in both CAPEX and OPEX.
6 ACKNOWLEDGEMENTS
The author would like to thank his colleagues and co-authors at KROHNE Altometer and
KROHNE Oil & Gas who provided access to internal and external calibration reports, site
surveys and commissioning reports to enable the data to be collected and presented in this
paper.
Liquid flowmetering systems
Gas flowmetering systems
Supervisory systems
Flow computers
Tank Management Systems
Loading & Offloading systems
Leak Detection Systems
From the well head,through massivepipelines, onto tankersand into the terminalsand refineries; the flowof oil and gas productsneeds to be measuredaccurately and reliably.That is the world ofKROHNE Oil & Gas.
In 2001, the leader in flow metering KROHNE in Duisburg,grouped together all its experts and established a specialistcompany at their main manufacturing site in theNetherlands. The company has grown continuously sincethen. The need for more space while retaining access to aqualified workforce brought KROHNE Oil & Gas to custom-designed premises in Breda.
The dynamic growth continues with the workforce havinggrown to over 160 persons solely dedicated to the oil and gasindustry.
Through acquisitions and expansions KROHNE Oil & Gasnow has 8 manufacturing facilities in the Netherlands, UK,India, Malaysia, USA, Brazil, South Africa headquarters inBreda servicing the world's oil industry through offices of theKROHNE group, in more than 60 countries worldwide.
The scope of KROHNE Oil and Gas starts with custody trans-fer flowmetering for oil, gas and liquefied gas and continuesthrough tank management, loading and offloading and leakdetection and localisation systems.
KROHNE Oil & Gas Overview
KROHNE Oil & GasMinervum 74414817 ZG BredaThe Netherlands
Tel.: +31-76.71.2000Fax.: [email protected]
LithuaniaMalaysiaMauritiusMexicoMoroccoNew ZealandPeruPortugalRomaniaSaudi ArabiaSenegalSerbiaSlovakiaSloveniaSwedenTaiwanThailandTunisiaTurkeyVenezuelaVietnamYugoslavia
Representatives
AlgeriaArgentinaCameroonCanadaChileColombiaCroatiaDenmarkEcuadorEgyptFinlandGabonGhanaGreeceHong KongHungaryIndonesiaIranIrelandIsraelIvory CoastJapanJordanKuwaitLatviaLibya
KROHNE Companies
AustraliaAustriaBelgiumBrazilChinaCISCzech RepublicFranceGreat BritainIndiaIranItalyKoreaMalaysiaNetherlandsNigeriaNorwayPolandSingaporeSouth AfricaSwitzerland SpainTurkeyUkraineUnited Arab EmiratesUSA
© K
RO
HN
E 03
/200
7
All
righ
ts r
eser
ved