Concepts of Multi-Phase Flow Measurement

TOPICS THAT WILL BE DISCUSSED INCLUDE:

1.Multiphase flow regimes in horizontal and vertical pipes2.Use of a “Triangle Diagram” to represent 3-phase flows3.Difficulties in multiphase flow measurement4.Multiphase flow meter types and their limitations5.Specifying Multi-phase Flow Meters, and6.Predicting well flow measurement requirements

Concepts of Multi-Phase Flow Measurement

© Enterprise Consultants International, Ltd. Page 2

Concepts of Multi-Phase Flow Measurement

Introduction

Why are multiphase flow meters needed?

Multiphase flow regimes


Why are Multiphase Meters Needed ?

A. Improve oil well and reservoir management

B. Justify tax relief for some wells

C. Monitor Oil & Gas Production

D. Quantify flaring and other losses.


Why is Multiphase Metering Difficult?

Coming out of an oil well, oil, water, and gas phases are mixed together

The oil/water/gas mixture will not be homogeneous in cross-section or over time, and this makes it difficult to measure each phase

Complex flow patterns (called Flow Regimes) mean that measurement is even more difficult


Some Important Terms

© Enterprise Consultants International, Ltd.

GVF – Gas Volume Fraction (Vgas/Vtot @process T & P)

Superficial Gas Velocity – Average of velocities

Superficial Liquid Velocity

Slip – Difference between liquid and gas flow rates

Water Cut - % water in liquid (@Std. T & P)

Multiphase Flow Regimes


Each flow Regime has different measurement challenges.

Traditional flow meters cannot accurately measure these flow regimes.

Gas

Liquid

Annular Flow

Slug Flow

Dispersed Flow

Why Do Flow Regimes Matter ?


Superficial Gas Velocity (m/sec)

1.0 10 100

Supe

rfici

al L

iqui

dVe

loci

ty (m

/sec

)

1.0

10

1

00

Stratified

Plug

DispersedBubble

Slug

Annular

Mist

Wavy

GasLiquid

Diagram is from “State of the Art Multiphase Flow Metering” published by the API

Why Do Flow Regimes Matter ?



1.0 10 100

Supe

rfici

al L

iqui

dVe

loci

ty (m

/sec

)

1.0

10

1

00

Stratified

Plug

DispersedBubble

Slug

Annular

Mist

Wavy

GasLiquid

How Many Flow Regimes are There?


Horizontal Flow Regimes

1. Stratified Flow2. Wavy Flow3. Slug Flow4. Plug Flow5. Bubble Flow6. Dispersed 7. Annular Flow8. Mist

Vertical Flow Regimes1. Churn

2. Slug Flow

3. Bubble Flow4. Dispersed 5. Annular Flow6. Mist

Horizontal Stratified Flow Regime


At low velocities, gravity causes the liquid to flow along the bottom of the pipe, and gas along the top.

Volumetric Flow rate of the gas will be much higher than the liquid.

Flow Direction

GasLiquid

Horizontal Wavy Flow Regime


Waves are caused by turbulence in the gas and liquid.

Wave on surface of the liquid

GasLiquid

Slug Flow Regime


A “Slug” is a liquid wave that reaches to the top of the pipe, sealing gas between successive waves.

In Slug Flow, gas moves faster than the liquid.

Waves

GasLiquid

Plug Flow Regime


Liquid Plug seals the pipe

Gas and Liquid move at the same speed.

Liquid Plug with Gas “Cells” along Top of Pipe

GasLiquid

Bubble Flow Regime


GasLiquid

Bubbles tend to rise to the top of the pipe.

Small to Medium-sized Bubbles

Dispersed Flow Regime


GasLiquid

Tiny bubbles are suspended in the liquid and tend NOT to separate.

Tiny Bubbles suspended in the liquid

Annular Flow Regime


Liquid Flows in an annulus (ring) around the pipe wall.

Gas flows much more quickly along the center of the pipe

GasLiquid

Mist Flow Regime


Mist consists of tiny liquid droplets that are suspended in the gas stream

Fine “Spray” of liquid in fast flowing gas

GasLiquid


Example Horizontal Flow RegimeTransitions

Page 20

Stratified Flow

Wavy Flow

Bubble Flow

Plug Flow

Slug FlowGas

Liquid

Vertical Flow Patterns


Flow patterns in vertical pipes are different, since the stratified and Wavy regimes do not exist, but an additional “Churn” flow regime appears.

MistBubble Flow Churn Flow AnnularSlug FlowDispersed

Vertical Flow Patterns


MistBubble Flow Churn Flow AnnularSlug FlowDispersed

Vertical Flow Regimes



10-1 1 10 100

Supe

rfici

al L

iqui

dVe

loci

ty (m

/sec

)

10-2

10-1

1

10

BubbleSlug

Annular

MistChurn

GasLiquid

Dispersed

Vertical Dispersed Flow Regime


Tiny Dispersed Bubbles

Virtually identical to Horizontal Dispersed Flow,

Tiny bubbles suspended in the liquid are not influenced by gravity.

GasLiquid

Vertical Bubble Flow Regime


GasLiquid

Bubbles tend to rise through the fluid.Gas flow is slightly faster than liquid flow

Small to Medium Bubbles

Churn Flow Regime


Liquid flows can move alternately downward and upward.Gas Flows go much faster than liquid bulk velocity

GasLiquid

Liquid is moving both upward and downward

Vertical Slug Flow Regime


“Slugs” of liquid fill the pipe cross-section, sealing gas between successive slugs.

Gas moves faster than the liquid.

Liquid Seal

GasLiquid

Vertical Annular Flow Regime


Liquid Flows in an annulus (ring) around the pipe wall.

Gas flows much more quickly along the center of the pipe

Annular Flow

GasLiquid

Vertical Mist Flow Regime


Mist consists of tiny liquid droplets that are suspended in the gas stream

Fine “Spray” of liquid in fast flowing gas

GasLiquid

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Concepts of Multi-Phase Flow Measurement