Hydrocarbons metering, storage, and export systems

May 2015 G. Moricca 1

Hydrocarbons

Metering, Storage,

and Export Systems

Giuseppe MoriccaSenior Petroleum [email protected]


Metering storage and export

A larger

production

complex

generally has

an

associated

tank farm

terminal

allowing the

storage of

different

grades of

crude to take

up changes in

demand,

delays in

transport etc.

Most plants do not allow local gas storage, but oil is often stored

before loading on a vessel, such as a shuttle tanker taking the oil to a

larger tanker terminal, or direct to crude carrier.


Metering storage and exportOffshore production facilities without a direct pipeline connection generally

rely on crude storage in the base or hull, to allow a shuttle tanker to

offload about once a week.


Metering Systems

Partners, authorities and customers all calculate invoices, taxes and payments based on the actual product shipped out.


Metering Systems

in out

Although some small

installations are still

operated with dipstick

and manual records,

larger installations

have analysis and

metering

equipment.

To make sure

readings are accurate,

a fix or movable

prover loop for

calibration is also

installed.

Liquid Hydrocarbon Metering System


Metering Systems

in out

The figure shows a

full liquid hydrocarbon

(oil and

condensate)

metering system.

The analyzer

instruments on the

left provides product

data such as density,

viscosity

and water content.

Pressure and

temperature

compensation is also

included.



Metering Systems


For liquid, turbine meters with dual pulse outputs are most common.

Alternatives are positive displacement meters (passes a fixed volume per rotation or stroke) and coriolis massflow meters.

These instruments can not cover the full range with sufficient accuracy. Therefore the metering is split into several runs, and the number of runs in use depends on the flow. Each run employs one meter and several instruments to provide temperature and pressure correction.


Metering Systems

Ultrasonic Flowmeters

The ultrasonic flow meters are based on the difference in

transit-time method. Each couple of transducer (channel), built

in the opposite side of the measuring tube, send and receive

acoustic signals through the flow in two opposite directions. One

signal is sent downstream of the flow and one is sent upstream,

both along the same path. A sound wave travels faster with the

flow than one against the flow.

The difference in transit

times is proportional to

the medium’s flow

velocity. The number, shape

and location of the channels,

are the key to compensating

for flow profile effects.


Metering Systems

Ultrasonic Flowmeters

Gas Ultrasonic FlowmeterALTOSONIC V12 / V6

Liquid Ultrasonic FlowmeterALTOSONIC V / III


Metering Systems

Coriolis Mass Flowmeters

The mode of operation of mass flowmeter is based on the Coriolis

principle.

This allows you to determine the mass flow of liquids and

gases from the deformation of the measuring pipe caused by

liquids and gases.

At the same time, the density of the medium can be taken from

the resonance frequency of the pipe that has been caused to

vibrate.

Two sensor coils serve to detect the Coriolis effect.

If there is no flow, both sensors record the same sinusoidal

signal.

Once a flow begins, the Coriolis force acts on the flowing mass

particles of the medium and leads to a deformation of the

measuring pipe and a phase shift between the sensor

signals.


Metering Systems

cont/CoriolisMass Flowmeters

The sensors measure the

phase shift of the

sinusoidal vibrations.

This phase shift is

directly proportional

to the mass flow.

Volume flow is calculated

from mass and density

measurement.


Metering Systems

Liquid and Gas Coriolis Mass Flowmeter: Optimass 2000

These truly straight twin-tube mass flow meters have been specifically developed for high-volume measurements in the oil and gas industry, such as terminals and transport pipelines.

The Optimass 2000 Coriolismass flow meter is easy to install and, measures essentially independent of pressure and temperature and therefore provides accurate, custody-transfer measurement of volume and mass over a wide flow range.


Metering Systems

Electromagnetic Flowmeters

The electromagnetic flowmeter is based on Faraday’s law of

induction.

According this law, a certain voltage is induced in a conductor

or conductive medium, which is moving in a magnetic field.

This voltage is proportional to the movement speed of the

medium.

For electromagnetic flow meters, the induced voltage is

tapped either via two measuring electrodes that are in

conductive contact with the measure substance or in a capacitive

manner with no contact.

An electronic measuring transducer amplifies the signal and

converts it to a standard signal


Metering Systems



Metering Systems

These high-pressure meters find use in well-water injection as well

as flow metering applications in refineries. They are available in

various sizes, materials and liners to cover all needs.



Metering Systems

Gas metering is similar, but instead, analyzers will measure hydrocarbon content and energy value (MJ/scm or BTU, Kcal/scf) as well as pressure and temperature.

The meters are normally orifice meters or ultrasonic meters.

Orifice plates with a diameter less than the pipe are mounted in cassettes. The pressure differential over the orifice plate as well as pressure and temperature is used in standard formulas to calculate normalized flow.

Different ranges are accommodated with different size restrictions.

Gas Metering System


Metering Systems

Gas metering is less accurate than

liquid typically ±1.0% of mass.

There is usually not a prover loop,

instead the instruments and orifice

plates are calibrated in separate

equipment

Gas Metering System


Metering Systems

Venturi Flowmeter

The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe.

Venturi flowmeter is a practical instrument which makes use of the Bernoulli effect and a manometer pressure gauge to determine the flow rate of travelling fluid through the pipe.

The illustration shows that you can express the fluid velocity v1 at the inlet of the device in terms of the difference in pressure measured by the manometer.

Note that it presumes that the density of the flowing gas is constant, which will not necessarily be true.


Metering Systems

The limiting case of the Venturi effect is when a fluid reaches the state of choked flow, where the fluid velocity approaches the local speed of sound.

In choked flow the mass flow rate will not increase with a further decrease in the downstream pressure environment.

Gas and Wet Gas Venturi Tube: VPE 7600


Fiscal metering systems

Metering Facilities located at Mina Al-Ahmadi - Kuwait.

These dynamic metering systems are

provided to enhance the accurate

measurements of crude oil and prevent

losses due to measurement

variances/errors

Meters Operating Principle

Positive Displacement (PD) Meters operate

basically as follows:

measure liquid throughput (volume) by

dividing the flowing liquid stream into discrete

equal volumes and counting them as they are

discharged from the meter.

Source: Kuwait Oil Company



Meters Operating Principle

When crude passes through the meter it causes

the meter rotor to rotate at a rate proportional to

the flow.

The rotor moves through a magnetic field

produced by a magnet.

A magnet pick-up coil, fixed on the meter housing, produces an

output pulse each time the rotor or rotor blade passes through the

field.

A pre-amplifier boosts the pulses and transmits them to the

Flow/Supervisory Computer where the pulses are counted and

calculated based on the meter factor and 'K' factor to give the flow

rate reading.



Cushing Crude Oil Terminal - Oklahoma The metering system consists of sixteen 10-inch positive displacement meters and a dedicated meter prover. The facility is operated from a central control terminal by a single operator through a dual redundant SCADA system.



Bi-directional prover metering systems

The most reliable means of determining and verifying the accuracy of

an Automatic Custody Transfer (ACT) liquid sales meter is to compare

a measured volume of liquid through the meter against the known volume

of a bi-directional meter prover system.

The actual comparison of these volumes is referred to as a "meter proving".

To ensure proving accuracy, it is necessary to collect fluid data, which will be

used in making calculations to determine "true volume".

The basic principle of operation of the bi-directional meter prover is to

provide an accurate and repetitive displacement of liquid through a

pre-calibrated volume between two detector switches.

Accurate displacement of the liquid is accomplished by forcing an inflatable

spheroid through the calibrated section of pipe using fluid energy from the

stream being metered and recording the metered volume.

A ratio is determined between the known volume displaced and the volume

indicated by the meter. This ratio is the "Meter Factor".

Meter Factor is what we multiply the counter register by to obtain

true volume.


Portable Meter Provers




Bi-directional prover metering systems

Bi-directional pipe proversystems establish accurate readings and meter factors for reliability.

Flow and displacer operate in two directions using a four-way valve design.


Fiscal Metering Systems

Overview of Measurement Categories

For petroleum fluids considers three levels of metering accuracy are taken into consideration:

HYDROCARBON HYDROCARBON

LIQUID GAS

FISCAL OR CUSTODY TRANSFER QUALITY MEASUREMENT 0.25 % 1 %FIELD OR PLATFORM ALLOCATION 1 % 3 %WELL ALLOCATION 5 % 5 %

Fiscal Quality Measurement is required at points of custody transfer and at the export of the offshore system where the two points are different. The offshore system may include more than one connected production platform.

Field or Platform Allocation denotes the accuracy required for the total flow from a system to be allocated to a single field or platform in a multi-field or platform development, where total flow is later measured further down the production stream by an approved fiscal quality meter, as described above.

Well Allocation is the level of accuracy required for allocation of total flow to an individual well.



Overall Measurement Uncertainties

The following overall measurement uncertainties* are required:

* Measurement Guidelines in the Newfoundland and Labrador and Nova Scotia Offshore Areas October 2003



Shown in table are potential annual revenue losses due to lack of proper accuracy, precision and accountability estimated by Saudi Aramco*.

* After Youssef Farid Basrawi - Saudi Arabian Oil Company - Crude And Hydrocarbon Measurement Technologies .



Requirements for automated condition

The fiscal measurement systems shall be designed for fully

automated condition based maintenance.

This includes the ability to automatically verify the current

condition of all measured field tags that are of importance to

the integrity of the fiscal measurement system. These field tags

are typically pressure, temperature, density, differential pressure,

flow values (ultrasonic meter values), level in sampling container

(compared to calculated level) etc.

This verification of current condition shall preferably be carried

out using calibrated reference meters.

Where possible, comparative monitoring of parallel meter

runs shall be carried out, i.e. when two or more meter runs are

in operation.



Minimum test requirements for fiscal measurement systems

The supplier shall at each test, as a minimum demonstrate the following:

● the capability and proper operation of the hardware and software;

● the equipment’s ability to meet all functional and technical

requirements;

● that all the spare requirements are included;

● that the communications software and hardware work properly;

● satellite communication, if applicable;

● the operation of the graphics package;

● that all counters, registers, internal switches, etc. will be reset at the

correct hour (project specific) each day, in such a way that no data is

lost and there is no effect on the accuracy of calculations made

following the turn-over;

● that no data will be lost/changed if switching over to a standby system

(project specific);

● that all calculations are correct;

● interface/total functional test to the safety and automation system

(SAS) including displays, alarms, operator interactions etc.


Well Test Measurement Well Test measurement refers to intermittent measurement of

production rates by test separator metering.

Flow rates of each of the three phases are related to well-headparameters (such as choke position or well-head flowingpressure), and the production from each well is integrated over aflowing period to give the total production from each well, andhence the field.

This strategy is fairly widely employed and is often referred to as‘Flow Sampling’.

There are no established standards for its deployment, and thereis therefore considerable scope for in system design andoperation


Thank Youfor

Your attention Giuseppe Moricca

Senior Petroleum [email protected]

linkedin.com/in/giuseppe-moricca-983a6b82Mob. +39 347 7573167

Hydrocarbons metering, storage, and export systems

Technology

Transcript of Hydrocarbons metering, storage, and export systems