BASIC CHEMISTRY FOR MEASUREMENT

BASIC CHEMISTRY FOR MEASUREMENTMatterAnything that possesses mass and occupies space. Made up of elements and compounds

Elements and compounds Element is the simplest form in which matter exists. The universe consists of 109 known elements.

FLOW MEASUREMENTCustody Transfer A measuring system comprising mechanical, instrument and computer parts whose registered measured quantity is used for sale where there is a change in ownership. This system normally has an uncertainty of +/-0.25 % of standard volume.

Allocation MeteringA measuring system comprising mechanical, instrument and computer parts whose registered measured quantity is used for allocation between two or more Contractors which involved in sharing the same facilities for their operation . This system normally has an uncertainty of +/-1%.

** Above as defined by PPGUA -

Flow MeasurementTypical Flow Measurement System Consists of:Primary Meter (DP, Turbine , USM, etc)Secondary Instrumentation (PT, TT, Densitometer)Data Acquisition System (PLC, HMI)Flow Computing System (Flow Computer)ProverSampling SystemAnalyzer Quality Measurement System

Typical Liquid Metering System

Type of Flow MeterHead (Differential Pressure) Flow MetersPositive Displacement MeterTurbine MeterUltrasonic Flow MeterMagnetic Flow MeterVariable Area Flow MeterVortex Shedding Flow MeterMass Flow Meter - CoriolisDifferential Pressure Flow Meter

DP METER

Multiphase Flow Meter vs Wet Gas MeasurementsWhat is Multiphase Meter?Multiphase meters are devices that measure oil, gas, and water flow rates of a well stream without separating these components into individual phases. Wet gas measurement also can considered as multiphase flow measurements but for high GVF (>90%).

Wet Gas Meter????Wet Gas MeasurementsWet gas flow is a special sub-set of two phase flow. XLM < 0.3As the wet gas definition does not differentiate between phase components, a wet gas flow can be a flow with 0.3 LM X that has one or more liquid component(s).

Wet Gas MeasurementCommon Term:Superficial Gas Velocity (SGV)This term refers to the gas velocity in a pipeline system that would be present if there were no liquid present in the gas stream, If liquid is however present in the system, the actual gas velocity will be higher due to the reduction in available pipe area caused by the liquid present taking space in the pipe.Superficial Liquid Velocity (SLV)The term superficial liquid velocity refers to the liquid velocity that would be present if there were no gas present in the gas stream and is related to the SGV.Liquid Load (LL)Liquid load, or mass ratio, is a wet gas correlation term that is used to describe the amount of liquid present in the flowing gas stream. This term is usually defined as the ratio of the liquid mass flow-rate to the gas mass flow-rate and is commonly expressed and used in calculations as percentage value.Gas Volume (void) Fraction (GVF.)GVF, or gas volume fraction, is defined as the ratio of the gas volumetric flow-rate to the total volumetric flow-rate. The total volumetric flow-rate is the sum of the liquid volumetric rate and the gas volumetric flow-rate. These volumetric flows are usually expressed in actual (not standardized )volumetric terms.Wet Gas MeasurementCommon Term:

Liquid Volume Fraction (LVF).LVF, or liquid volume fraction, is defined as the ratio of the liquid volumetric flow-rate to the total volumetric flow-rate. The total volumetric flow-rate is the sum of the liquid volumetric flow-rate and the gas volumetric flow rate. These volumetric flows are also usually expressed in actual (not standardized) volumetric terms.

Lockhart & Martinelli Parameter (or dimensionless number).The term Lockhart Martinelli Number (X) isa dimensionless parameter that is used to correlate gas and liquid flow in a pipe. It was derived by two engineers Lockhart and Martinelli whom worked on steam flow measurement in the late 50s in the UK and has been put forward by wet gas researchers in wet gas calculations.

Liquid Hold-up (Hold Up).Liquid Hold-up is described as being the area occupied by the liquid in a wet gas stream when viewed at a specific location of the cross-section of the pipe, relative to the total cross sectional area of the pipe at the same location.

Measurement Over-Reading (or over-measurement error).When a flow measurement device operating in a wet gas environment and reports a higher flow-rate than it should, it is considered to have what is termed over reading or over measurement error .

Wet Gas MeasurementCommon Terms:

Under Reading (or under measurement error).When a flow measurement device reports a lower flow-rate than is actually occurring it is considered to have produced an under-reading or under-measurement error.Froude Number.The gas velocity may be also expressed as a dimensionless number, known usually as the Densitometric Froude Number:Multiphase Flow.This term describes two or more types of liquid components flowing in the gas stream at the same time, it is then referred to as multiphase flow. Typical liquids include oil, condensate and water, sometimes solids may be entrained which can make the mixture harder to measure and more difficult to determine a mathematical representation of the said components flow-rates.