Multiphase Flow Meter Implementation, Verification and Use ... 18130... · •𝑀𝐴 𝑎𝑙is...

21 – 22 February 2018 Houston, TX

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Multiphase Flow Meter Implementation, Verification and Use for Calibration of Virtual Metering in Kashagan

Project

Adilbek Mursaliyev

Beibit Akbayev

Overview of Kashagan

• The Kashagan field is located in the Kazakhstan sector of the Caspian Sea

• The reservoir lies some 4,200 meters below the shallow waters of the northern part of the Caspian Sea.

• The harsh offshore environment of the northern part of the Caspian Sea

• A unique combination of technical and supply chain complexity.

• One of the largest and most complex industrial projects.

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• Satellite islands currently under operation: 2

• One hub island for oil and gas pre-processing

• Oil, gas and sulfur treatment plant in onshore

• One of the satellite islands’ wells equipped with individual MPFMs

Overview of MPFM technology in Kashagan

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• Model: Vx PhaseWatcher

• Venturi tube throat Diameter: 88 mm

• Barium-133 radioactive source and detector assembly

• Differential-pressure sensor

• Pressure sensor

• Temperature sensor.


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Allocation scheme and well testing

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• Mass allocation

• Proportional Reconciliation

• 𝑅𝐹(𝑂𝑖𝑙) = 𝑖=0𝑛 𝑀𝑖

𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙

𝑀𝐴𝑐𝑡𝑢𝑎𝑙

• Where 𝑀𝑖𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 is estimated mass of i-th well and

𝑀𝐴𝑐𝑡𝑢𝑎𝑙 is measured mass at delivery point.

• 𝑀𝐴𝑐𝑡𝑢𝑎𝑙 is sum of oil measured by fiscal metering skid at custody transfer point and tank delta stock.


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M: multiphase flowO: treated liquid oil measured at custody transfer pointG: treated gas measured at custody transfer and internal usersS: Liquid Sulphur measurement


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• Hub island is equipped with one test separator

• Hub wells are routed to test line one by one

• One of the satellite islands have one MPFM shared by wells

• Another satellite island has individual MPFM for each well


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• Important to not penalize real time measurements

• Required to estimate well theoreticalsaccurately where there is not individual meter

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Upstream choke installation challenge

• Conditions at upstream the choke valve varies with the choke operation

• This leads to changes in PVT properties, e.g. shrinkage, density, etc. which impacts the phase and rate calculations;

• MPFM’s fluid model uses one single polynomial equation for PVT and fluid properties by default

• Challenge at and near bubble point. – The transition between above and below bubble

point smooth instead of sharp. This led to incorrect properties values used in the calculations.

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Solution

• Two separate PVT polynomial equations, one for above bubble point and the other for below bubble point.

• The auto switching algorithm developed in DCS:

• which sends Boolean signal (1 or 0 for below or above bubble point) to the flow computers depending on gas fraction and pressure/temperature values.

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Solution

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Solution

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Validation of MPFM

• Flow loop test

• restricted area of flow conditions

• accuracy of the reference instrumentation is correctly known

• Validation required because the MPFMs are operating within wide range of pressure conditions (between 120 – 500 barg)

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Validation of MPFM

• Validation tool built in excel with VBA

• Uses Peng-Robinson cubic equation of state.

• Used for phase fraction and total mass rate validation

• The deviation between calculated and measured total mass rate is within ±1%.

• The deviation for phase fraction is on average within ±5% absolute.

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Validation of MPFM

• Validation check by use of gas outlet measurements at production separators.

• Wells diverted to one production train for one month (segregation of the wells from the rest).

• Load ratios between the production trains from gas measurements at separators.

• The load ratios applied to total oil production at the outlet form the plant

• Compared against measured volume from MPFMs.

• The deviation around 3%.

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Validation of MPFM

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Validation of MPFM

• Additional test performed for 20 hours period:• production only from wells with MPFMs• and the produced and treated oil

accumulated at one tank in onshore. • The MPFM measured cumulative volume was

compared against accumulated oil in the tank. The deviation was 3% as well.

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Virtual flow metering and MPFM

• Availability of downhole gauges• The virtual flow metering concepts slowly

gaining “trust” from subsurface discipline engineers.

• One of the methods - Vertical Lift Performance (VLP) equation

•∆𝑃

∆𝐿= 𝜌𝑔 +

𝑓 𝜌 𝑣2

2 𝑑

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• Not all of the wells are equipped with individual MPFM

• Required to have alternative real time well rate estimation

• The VLP method tested on real time MPFM measurements

• After proving the concept, applied for other wells by tuning against test separator during planned well testing results

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Future improvements

• The real-time MPFM measurements should be used for better understanding the following:

• Impact of slippage between phases to friction loss in the well production tubing;

• Impact of flow pattern to friction loss;• Impact of well curvature (deviation) to

friction loss.• Implement real time PVT and VLP calculations

on PI ACE™ engine.

Multiphase Flow Meter Implementation, Verification and Use ... 18130... · •𝑀𝐴 𝑎𝑙is...

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