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    North American Gas

    FIELD OF THE FUTURE

    Deliquification Forum 2007:

    Deliquification Basics

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    Agenda10:00

    12:00

    Safety/Intro

    Production Related Geology

    Production Operations

    Fundamentals

    Problem Solving Liquid Loading

    1:00

    3:00

    Working the Problems

    Objectives

    How reservoir characteristics define and impact liquidloading

    The part the production cycle plays in liquid loading,

    pros and cons of artificial lift

    Basics of deliquification, what data to consider when

    analyzing liquid loading: critical velocity and using

    Turner/Coleman unloading curves, casing/tubing

    pressures, flow regimes, production trends

    Real life NAG liquid loading problems, lessons

    learned, best practice sharing

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    No Equations

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    The Key Elements Of Hydrocarbon Geology

    Geology is the study of the Earth, the materials

    of which it is made, the structure of thosematerials, and the processes acting upon them; an

    important part is the study of how these elements

    have changed over time.

    Our overview will focus on:

    Formation

    Migration

    Storage

    Recovery

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    Initially, much of the Earth is covered with water.

    Hydrocarbon Formation

    Over millions of years, trillions of plants and animals living in the oceans die

    and are mixed with and covered by sediment entering the water as

    the land

    masses erode, building up layer upon layer.

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    Heat, Time and Pressure

    As these layers are being deposited, they are being changed by the high

    temperatures found below the surface, time in millions of years,

    and the

    pressure created by layer after layer being laid down.

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    Gas, Oil, and Water

    Trapped with in these layers is the water left by the ancient oceans and the

    ooze left over by decaying plants and animals, often buried more

    than two

    miles down. Time, temperature and pressure cook

    the ooze in to gas and oil.

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    Coalification

    We also will find coal, and the gas trapped with in the coal, in

    these layers.

    When plant material is preserved fast enough to prevent decay and when

    coupled with time, pressure and heat, it turns first to peat and

    then to coal.

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    Initially the hydrocarbons exist only in tiny pockets. The buoyancy of the

    materials, and the pressure of the earth slowly squeeze them out

    of the rock

    forcing a migration. The moving fluids meet up with others rising to the

    surface.

    Migration

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    Migration contd.

    As the hydrocarbons migrate, the lighter gas rises to the top, with oil coming to

    rest below it, and water left at the bottom. It is important to note that you may

    have all three phases in the reservoir rock, or any combination.

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    Storage - Sedimentary Rock

    Sedimentary rock, up to 4 miles thick, is formed by the layers of falling

    sediment over millions of years. The most common types are chalk, sandstone,

    limestone, clay and shale and contain much of the worlds hydrocarbons.

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    Source Rock

    Reservoir Rock

    Seal Rock

    Storage Source, Reservoir, and Seal Rock

    As the layers were buried, they attained different characteristics. The source

    rock is where the hydrocarbons were formed. The reservoir rock is the storage

    container of the hydrocarbons with migration only to be stopped by a seal rock,

    holding the hydrocarbons in place.

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    Coal-bed Natural Gas

    Coal bed natural gas is generated and stored in coal beds. Gas in coal seams is

    stored in three basic ways: adsorbed to coal particles and held by molecular

    attraction, within pore spaces, cleats and fractures of the coal, and dissolved in

    water contained within the coal.

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    Porosity & Permeability

    By definition, reservoir rock must have:

    Capacity to store fluids

    Ability to transmit fluids

    Porosity is fluid storage capacity in a rock or how much you have

    Measured as % of rock void space

    Tight gas between 3

    10%

    Permeability

    is the measure of ability of the rock to transmit fluids

    or how easy fluids will flow through the rock

    Measured in units called darcies

    or millidarcies

    Tight gas < .01 md

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    High Porosity

    Porosity is the percentage void space within rock that may contain fluids.

    Porosity can be primary porosity, such as space between grains that were not

    compacted together completely.

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    Low Porosity

    Low Porosity is the low percentage of void space.

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    High Permeability

    Permeability is a measure of the ability of a rock or unconsolidated material to

    transmit fluids. It is of great importance in determining the flow characteristics

    of hydrocarbons in oil and gas reservoirs.

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    Low Permeability

    Gas reservoirs with lower permeability are still exploitable because of the lower

    viscosity of gas with respect to oil. Tight

    gas wells typically have

    permeabilites of less than 0.01 md.

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    Conventional

    Sands

    Free gasFree flowing

    Core picture

    Tight

    Sands

    Free gasSlow flowing

    Shale

    Free & desorbed gasSlow flowing

    Coal-bed

    Methane

    Desorbed gasFree flowing

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    Tight Gas Rock Low Porosity, Low Permeability

    Shoreface

    & Shallow Marine Sand

    Average Porosity: 3.5% Best Permeability:0.012

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    Types Of Traps

    Structural

    Structural traps hold oil and gas

    because the earth has been bent and deformed insome way. The trap may be a simple dome or big

    bump, a crease in the rocks, or it may be a trap

    formed by a fault.

    Stratigraphic

    Stratigraphic traps are depositional

    in nature. This means they are formed in place,

    usually by sandstone ending up enclosed in shale.

    The shale keeps the oil and gas from escaping the

    trap.

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    Stratigraphic Trap

    The stratigraphic trap is a feature that ensures the hydrocarbons remain

    trapped in the subsurface. This trap is a feature that contains the hydrocarbons

    with a change in rock type like sand to shale.

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    Structural Traps - Anticline

    An anticline is a fold that is convex with the oldest beds found

    in the middle.

    Anticlines are favored locations for oil and natural gas

    drilling; the

    hydrocarbons low density causes it to migrate upward to the higher parts of

    the fold, until stopped by an impermeable layer.

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    Structural Traps - Faults

    Faulted rock commonly forms traps for the accumulation of hydrocarbons.

    They often also occur around reef complexes and collapse features such as

    ancient sinkholes.

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    Structural Traps Salt Dome

    An example of this kind of trap starts when salt is deposited by

    shallow seas.

    Since the density of salt is generally less than that of surrounding material, it

    has a tendency to move upward toward the surface. Hydrocarbons can

    accumulate on the sides of the large bulbous dome.

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    Reservoir Drive MechanismsThe reservoir drive mechanism is the process in which

    reservoir fluids are caused to flow out of the reservoir

    rock and into a well bore by natural energy. It is alsoreferred to as natural energy drivedriving the

    hydrocarbons toward the wells and up to the surfaces

    during the early life of a well. It controls the productionof the reservoir.

    The 2 main drive mechanisms that we will discuss are:

    Water drive

    Gas/Depletion drive

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    Water Drive - Bottom

    Water drive reservoirs depend on water

    and rock expansion to force the

    hydrocarbons out of the reservoir andinto the well bore. Water drive keeps

    the pressure high, so the objective is to

    try to produce as much gas as you can

    and outrun the water. Water drive is

    very rare in tight gas wells. The two

    types of water drive are:

    Bottom-water drive

    The stronger

    type of water drive. It forces thehydrocarbons up from the bottom of

    the reservoir.

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    Water Drive - Edge

    Edge-water drive is the weaker of the two types of water drive. It forceshydrocarbons in from the sides of the reservoir.

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    Gas/Depletion Drive Reservoir

    Depletion drive reservoirs remove

    volume, causing the gas to expand,

    and as long as pressure is low at thewell, the gas will continue to expand

    towards the top of the well head.

    Pressure in wells continually drops as

    drive energy is depleted, impactinghow liquids will be carried out of the

    well.

    Additionally, there is no water drive in

    depletion drive; water is in the pores of

    the rock..

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    Gas Drive in a Coal Reservoir

    Coal is a depletion drive; the flow

    characteristics are vastly different.

    In a coal reservoir you normally must remove

    water first allowing the gas to expand, the

    cleats to shrink, thereby increasing the

    permeability.

    As long as pressure is low at the well, the

    gas will continue to expand towards the top

    of the well head.

    Pressure in coal wells will also drop asenergy is depleted, just as in tight gas wells,

    impacting how liquids will need to be carried

    out of the well.

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    Sources of Water

    Often where there is gas, there is water. There are

    principally two ways to deal with this water, lift it

    out of the well, or leave it down there. Liquid can

    take two primary forms, water and liquid

    hydrocarbons such as light oil.

    These are the

    different ways water can find its way in to a well.

    Free Formation Water

    Condensation

    Water from Another Formation

    Water Coning

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    Free Formation

    Salt water can exist in the hydrocarbon reservoir. It is water trapped in the rock

    at the time the rock was deposited. It may be derived either from ocean water

    or land water, has persisted with little change in composition since it was

    buried with the sediment. Often this water is corrosive.

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    Condensation

    Water and/or hydrocarbons may enter

    the well bore with the gas at depth

    where higher temperatures andpressures keep the liquid in its vapor

    phase.

    Reducing the pressures the vapor rises

    with the gas, cooling as it does,changing to liquid in the tubing.

    Water from condensation is very fresh

    and calculations can tell us the

    maximum quantity that can be

    expected.

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    Water From another Formation

    Water can also enter the well bore somewhere away from the perforations

    because of a casing leak caused by corrosion

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    Water Coning

    The upward encroachment of water caused by pressure drawdown from

    production. If the gas rate is high enough, water may be sucked

    from a

    water zone below, or from an aqueous zone above or below the producingzone.

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    Ways Reservoir Characteristics Impact Liquid Loading

    Reservoir Characteristics

    Formation: Tight Gas

    Porosity: 3 -

    10%

    Permeability:

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    Drilling: putting a hole in the ground

    Completing a Well: activities and methods of preparing a well for theproduction of gas.

    Casing: series of metal pipes that turn hole

    into well

    Completion & Completion Techniques: finishing a well so it isready to produce

    Well Testing: determine the potential of the well, pressure/raterelationship during shut-in, flowing times, productivity testing,formation information

    Production: process by which reservoir fluids are brought to surface

    Maintenance & Repair (Workover): repairing/ replacing productiontubing and packers, repairing artificial lift, cleaning out wellbore,stimulation, swabbing, recompletion, etc.

    Processing & Testing Reservoir Fluids: treating and measuring fluid

    production/injection, separation of fluids, water disposal

    Production Cycle of Well

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    DrillingThis is the first of all firsts, drilling a hole in the ground.

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    Although most wells deviate at leastslightly from the vertical, well boregeometry is important to how awell is produced, completed and

    what artificial lifts may be used.

    It

    can also affect well from a flowregime perspectivethe greater theangle in a well, the less efficient thelifts because the gas outruns

    the

    liquid.

    Well Bore Geometry Types:

    Straight

    Directional

    Deviated

    Highly Deviated

    Lateral/Straight

    Multilateral

    Well Bore Geometry

    Deviated

    Highly

    Deviated

    Lateral/Horizontal

    Multilateral Well

    Slotted Liner Completion

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    Well Bore Geometry - Multilateral

    Deviated

    StraightHighly Deviated

    Horizontal/ Lateral

    Advantages:

    reduce footprint, more contact with reservoir,

    accelerated production, better wellbore

    placement, less drill sites

    Disadvantages:

    production allocation, testing & diagnostics, high

    angle wells speed up liquid load

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    Multi-Well Pad

    Advantages: reduce footprint, reduce facility costs, generate ownpower, allows for simultaneous operationsDisadvantages:

    high angle wells start to liquid load faster

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    Well Completion

    The process of finishing a well so that itis ready to produce natural gas. Itencompasses the activities and

    methods of preparing a well for theproduction of gas.

    A well casing

    is what segregates the

    formations from each other, through

    cement. Well casing refers to a seriesof metal tubes that are installed to turna hole

    into a well.

    Conductor casing

    Surface casing

    Intermediate or Liner String orProduction Casing

    Tubing

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    Well completion is the process of finishing a well so that it is

    ready to

    produce natural gas.

    There are 3 basic methods of completing a well:

    Open-Hole

    Cased-Hole

    Slotted-Liner

    Well Completions

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    Completions

    Open Hole Cased Hole

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    Completions, cont.

    Slotted Liner

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    Various Well Completions Lateral WellsConcrete Packand Perforations

    Gravel Pack and

    Slotted Liner

    Gravel Pack andWire Screen

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    Completion Techniques

    Wire Wrapped

    Gravel Pack

    Hydraulic

    Stimulation

    Perforations

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    Well Head

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    Extraction, Treatment, Selling

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    Maintenance and Repair (Workover)

    Service and work over rigs aresimilar to drilling rigs butsmaller in size and they usuallydo not have circulation or rotarysystems. Common jobs suchas depth measurements andlogging

    are performed with

    tools suspended on a wire line.

    The most commonmaintenance jobs arerepairing/replacingproduction tubing andpackers, repairing artificiallifts, cleaning the well bore

    and stimulation. Also,selecting the artificial lifts to beused in a well is consideredmaintenance.

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    Well Stimulation

    Process to enlarge old channels or create new ones in theproducing formation to enhance production. Two examplesare fracturing

    and acidizing:

    Hydraulic fracturing

    occurs when a fracturing fluid is

    injected at high pressures to cause fractures in the productionzone; it works well in low permeability, sandstone reservoirs.Because most NAG gas is produced from low porosity &permeability tight gas wells, hydraulic fracturing is done toincrease the amount of reservoir exposure to the well.

    Signification to deliquification

    is that the types of

    deliquification

    methods used could be impacted by

    proppant

    flowback. Depending on the deliquification

    technique, the fracture may, and will most likely, become part

    of the wells storage capacity. This causes the well to havedifferent characteristics for build up and flow periods.

    Acidizing

    has much less affect on deliquification

    thanfracturing. The acid reacts chemically with the rock to dissolve

    it, thus enlarging the existing flow channels and opening newones to the well bore. The reservoirs most commonly acidizedare the carbonate reservoirs, limestone and dolomite.

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    Processing and testing the reservoir fluids includes treating and measuring

    fluid productions/injection and also allows for water disposal.

    In processing and testing, gas and water samples are very useful. Daily

    water samples are used to test for corrosion, calcium, chloride and other

    compounds and elements.

    When a well is drilled through multiple formations, gas samples are also

    used to test which formation is producing the gas.

    Processing and Testing the Reservoir Fluids

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    Primary Methods of Unloading a WellThere are various ways of unloading a well that has filled with water; some

    techniques require mechanical devices and are referred to as artificial lifts.

    Artificial lifts are required to raise gas to the surface after natural energy

    becomes weak and the well ceases to flow. The following are the 5 mainmethods of unloading a well:

    Cycling

    Foam

    Plungers

    Beam Pump

    Compression

    Other ones that BP uses

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    Rate,MCFD

    Time

    Normal Decline

    Loading

    Goal of Artificial Lift

    Unloading Well to Mitigate Production Loss

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    CyclingAs the reservoir

    pressure depletes, we

    use cycling to returnthe well into its own

    natural rhythm.

    Closed/

    UnloadingLoaded FlowingOpen

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    Cycling

    Advantages

    Low initial cost

    Capable of being automated

    Used on wells with limitations and

    in combo with other remedies

    Easy, doesnt require tech

    expertise

    Unloads well & keeps it producing

    with minimal cost

    Effective in early life of well

    Disadvantages

    Wastes energy that could be

    utilitzed

    more efficiently, typically

    results in liquid fallback

    Unless automated, cant adjust

    with changing conditions requiring

    operator time to optimize

    Cannot reach maximum production

    without mechanical interface

    Works for limited time and then

    must be replaced

    Cant reach low bottom hole

    pressures

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    Foaming

    Foaming is a relatively inexpensive

    initial cost solution for gas well

    deliquification; it is a type of liquid

    and gas emulsion.

    The primary benefit of foaming is

    that the liquid is held in the bubble

    film and exposed to more surface

    area which in turn leads to a low-

    density mixture and less gasslippage. Two operating limitations governthe application of foam to theunloading of low rate gas wells:

    the success of foam surfactants in

    reducing bottomhole

    pressure and

    economics.

    OpenClosed

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    Foaming

    Advantages

    Helps minimize

    venting

    Capable of being automated or

    truck treated

    Useful in wells not capable of

    using other remedies (eg. offshore)

    Simple & inexpensive for low rate

    wells

    Disadvantages

    Cost, especially if automated or

    truck treated. Ongoing.

    Some water must be present to

    make this work

    Can plug tubing, particularly when

    no water is present

    Scale enhancer

    Valuable operator time is used

    When automated, cant adjust withchanging conditions

    Safety; chemical handling, MSDS,

    PPE, electrical equip safety

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    PlungersA plunger is a mechanical device dropped in well and utilized to

    push the liquids out.The well is shut in to allow the plunger to fall through the liquid;the well is then flowed allowing the critical velocity developed

    while the well was shut in to push the plunger to the top of the well, lifting the fluids out of the well bore.We are mainly concerned with three types of Plungers:

    Conventional

    Two Piece

    Flow-through

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    Plunger Cycle

    The compromise

    that usually yields

    the greatest

    production is

    found when

    balancing the

    plunger cycle

    frequency andplunger velocity

    that is not so fast

    that it damages

    the equipment orso slow that the

    plunger does not

    surface

    (approximately

    750 ft per minute).

    Loaded Shut in Flow Loading

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    Two Piece Plunger

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    Flow-through and Conventional Plungers

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    Plungers

    Advantages

    Low cost to purchase, install,

    move

    Low maintenance

    Can be automated to adjust for

    changing well conditions

    Works well in standard to large

    tubing strings

    With adequate GLR (gas liquid

    ratio) and pressure (400

    scf/bbl/1000 ft) can lift high liquidrates

    Disadvantages

    Under wrong conditions, plunger is

    a projectile and can blow off top oftree

    Requires more analytical

    capabilities of operator, so requires

    more time and attention

    Stalls out at low bottom hole

    pressure

    Hard to operate in small tubing and

    with sand

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    Beam Pump

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    Beam Pump Cycle

    Beam pumps may

    be the most

    common methodto remove liquids

    from gas wells.

    The main

    components of abeam pump are: a

    sucker rod, a

    sucker rod pump

    and a walking

    beam.

    LoadingFlow/LoadingUp StrokeDown stroke

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    Beam Lift

    Advantages

    Simple, efficient and easy to use

    Capable of achieving absolute

    minimum FBHP

    Use up to PxA

    Can be automated with pump off

    controllers to make changes as

    well conditions change

    Disadvantages

    High cost to purchase, install,

    maintain

    High maintenance

    Prime movers

    gas engines high

    maintenance, difficult to control;

    electric motors expensive tooperate

    Gas locking worse than normal in

    high GLR wells

    Safety

    more moving parts, more

    opportunity for error

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    CompressionIn general, compression lowers the

    surface pressure of a well with the

    intent of lowering bottom-hole

    pressure and increasing the gasvelocity to equal or greater than the

    critical unload velocity

    It also lowers the pressure on the

    formation.

    Compression helps artificial lift

    methods to various degrees.

    Compression is a technique that isoften used to assist in unloading the

    wells.

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    Compression Types

    Wellsite

    (permit).

    Satellite

    Echo SpringsPlant

    new 140

    MMSCFD

    Train Jan.

    2002

    Patrick Draw

    Plant

    Bypass

    Processing/Bypassing

    Plant A

    Plant B

    Bypass

    Export

    Export Pressure =1000 psiSatellite DischargePressure =600 psi

    Wellsite

    Discharge

    Pressure =300 psi

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    Compression

    Advantages

    Increases rate by lowering suction

    (line) pressure and unloads

    Very attractive when small

    changes in pressure give big

    changes in rate

    Can be rented and maintained byvendor

    Can be used on wells with

    mechanical limitations

    Can be used with plungers, stopclocks, and recirc

    Disadvantages

    Wont kick off a well. Often a

    short term fix and downhole

    solution is later required

    Purchase/rental and operation

    costs; high maintenance

    Safety

    fire hazards, moving parts

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    Other Artificial Lift OptionsESP PCP

    http://en.wikipedia.org/wiki/Image:Electrical_Submersible_Pump.pnghttp://en.wikipedia.org/wiki/Image:Electrical_Submersible_Pump.png
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    Surface handling of Gas Well Fluids

    Gas, Oil and Water go to

    Production Unit (Tpak)

    which heats and separates

    gas from liquid

    Separator inside Production Unit

    Dehydration unit removes water vapor and meters gas

    Water and oil stored for trucking

    Orifice Meter inside

    Dehydrator

    Fluctuations in pressure or flow at different points can cause loading

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    Mechanics Of Gas Well Liquid Loading

    Pressure

    Velocity

    Friction

    Gravity

    Critical velocity

    Pressure Velocity

    FrictionGravity

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    Critical Velocity/Rate

    Every gas well has a critical

    gas velocity below which

    liquid cannot be effectivelytransported from the well

    bore.

    Below the rate or critical

    velocity, liquids are noteffectively removed from the

    well bore and will settle to

    the bottom of the tubing

    creating a plug

    of liquid.

    Pressure Velocity

    FrictionGravity

    Critical Velocity

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    Activity Mechanics of Gas Well Liquid LoadingActivity 1

    Challenge

    The blue elements, water,

    would fall to the bottom of

    the tubing loading the wellwith water.

    Pressure Velocity

    FrictionGravity

    Critical Velocity

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    Understanding Unloading Curves

    The gas velocity at which liquids accumulate is predictable and can

    be related to flow rates in various tubing sizes; unloading curves

    show this relationship.

    Using these curves, you can predict if a well may be liquid loaded.

    At lower surface-flowing pressures, a lower flow rate is required to

    keep a well unloaded.

    At higher flowing pressures, a higher flow rate is required. With this

    in mind, the goal is to keep a well unloaded and operate at the

    lowest possible flowing pressure.

    Also important to remember is that there difference betweenTurner and Coleman unloading curves. It is recommended that

    when surface flowing pressure is less than a 1000 psi, use

    Coleman curves; above 1000 psi, use Turner curves.

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    0

    100

    200

    300

    400500

    600

    700

    800900

    1000

    0 200 400 600 800

    Flowing (Tubing) Pressure, PSIA

    MinC

    riticalVelo

    cityRate,m

    cfd

    2.375

    2.016

    1.90

    1.66

    Unloading Rates for Various Tubing Sizes -Turner

    Tubing Size

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    The Inflow Performance Relationship (IPR)

    A tool used in production engineering to assess well performance

    by plotting the well production rate against the flowing bottom-holepressure (BHP).

    The data required to create the IPR are obtained by measuring the

    production rates under various drawdown pressures, or calculating

    the difference between the average reservoir pressure and the

    flowing bottom-hole pressure.

    The reservoir fluid composition and behavior of the fluid phases

    under flowing conditions determine the shape of the curve.

    The IPR clearly shows that we will need to constantly adjust in

    order to maximize production.

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    0

    100

    200

    300

    400

    500

    600

    700

    800

    0 50 100 150 200 250 300

    Production Rate, mcfd

    Flo

    wingBottom-hole

    Pressure,psia

    Higher Pressure Gas Well

    Lower Pressure Gas Well

    Typical IPR Curves for Low/high Pressure Wells

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    Rate,MCFD

    Time

    Normal Decline

    Loading

    Goal of Artificial Lift

    Unloading a Well to Mitigate Production Loss

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    Tubing and Casing Pressures Open AnnulusNormal Loaded100 PSI

    Flowing Tubing

    Pressure

    130 PSI Casing

    Pressure

    100 PSI

    Flowing Tubing

    Pressure

    220 PSI Casing

    Pressure

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    Tubing and Casing Pressures LeaksTubing Leak Casing Leak

    100 PSI

    Flowing Tubing

    Pressure

    100 PSI Casing

    Pressure

    100 PSI

    Flowing Tubing

    Pressure

    80 PSI Casing

    Pressure

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    Casing and Tubing Pressure-Plot

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    Tubing and Casing Pressures Packer UnloadedNormal 1 Min. Shut In100 PSI Flowing

    Tubing Pressure

    0 PSI Casing Pressure

    130 PSI Flowing

    Tubing Pressure

    0 PSI Casing Pressure

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    Tubing and Casing Pressures Packer LoadedFlowing Loaded 1 Min. Shut In

    0 PSI

    0 PSI Casing Pressure 0 PSI Casing Pressure

    100 PSI Flowing

    Tubing Pressure101 PSI Flowing

    Tubing Pressure

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    Flow RegimesMist Annular Slug Bubble

    Decreasing Gas Velocity

    GasFlow

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    Four Flow Regimes Mist

    The gas phase is continuous and most of the liquid

    is entrained in the gas as a mist. The pipe wall is

    coated with a thin film of liquid and creating friction,

    but pressure gradient is determined predominately

    from the gas flow.

    Gas flow rates are still high.

    IPR curve is being followed

    Production rates are smooth

    Mist

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    Four Flow Regimes Plot Mist FlowMist Flow

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    Four Flow Regimes Annular Flow

    Some liquid may be entrained as droplets in the gas and

    pipe wall friction may increase. Gas dominates the pressure

    gradient, but liquid accumulation is becoming significant.

    Gas rates begin to decline.

    Velocity approaching critical rate

    Tubing and casing pressure gradient increases (can be not

    considerable)

    Production rates are more erratic

    Liquid production may be constant or falling.

    Bottom-hole pressures increase

    Production trend may fall below decline curve projections

    Annular

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    Four Flow Regimes Plot Annular FlowAnnular Flow

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    Four Flow Regimes Slug Flow

    Gas bubbles expand as they rise and coalesce into

    larger bubbles, then form slugs. Liquid phase is now

    the continuous phase. The liquid film around the slugs

    may fall downward. Both gas and liquid significantly

    affect the pressure gradient.

    Velocity shows marked decline.

    Liquid production may show a marked decrease.

    Gas production may increase

    Bottom-hole pressures may show marked increase

    Production trend falls below decline curve projections

    Slug

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    Four Flow Regimes Plot Slug FlowSlug Flow

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    Four Flow Regimes Bubble Flow

    The tubing is almost completely filled with liquid. Free

    gas is present as small bubbles, rising in the liquid. Liquid

    contacts the wall surface and the bubbles serve only to

    reduce the density.

    Velocity shows marked decline.

    Liquid production may shows marked decrease.

    Gas production may suddenly improve with outintercession for a short period

    Production at this very low rate may continue as bubbles

    continue to rise through the liquid.

    Bubble

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    Four Flow Regimes - BubbleBubble Flow

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    Decreasing Gas Rate TIME

    Well

    Dead

    Initial

    Production

    Unstable FlowStable Flow Stable Flow

    Rate

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    High Rate Data- 4 Hour to 1 Minute Data Scan8:30 11:00