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WELL PROBLEMS AND SOLUTIONS
pg. 60 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
Well Produced Problems
Objectives
Understand the Well produced problems
Know how to remedy these problems.
Know what kind of problems that can occur within a separator.
Know how to remedy these problems.
Emulsions
Emulsions are stable mixtures of two immiscible liquids. Emulsions arestabilized by an emulsifying agent which is a film of surface active agents that
reduces the interfacial tension between the oil and water. Given sufficient time,
most emulsions will dissipate naturally.
However, to reduce the retention time needed and break the emulsion, the film
of emulsifiers is normally altered by heat, chemicals, mechanical devices or a
combination of the three.
The two main emulsion types are:
(1) water-in-oil (invert) emulsion(2) oil-in-water (direct) Emulsion
DemulsifiersThe demulsifiers or emulsion breaker chemicals are surface active and must
specifically target the particular emulsion being produced. The desired chemical
will penetrate the fluid, disrupt the emulsifying film, breaking the emulsion and
allowing the liquids to disperse. The demulsifiers can be injected downhole, inthe manifold or pipelines and by batch in storage tanks
Foaming Crude OilIf the pressure is reduced on certain types of crude oil, tiny spheres (bubbles) of
gas are encases in a thin film of oil when the gas comes out of solution. This
results in foam, or froth. Foaming greatly reduces the capacity of oil and gas
separators since a much longer retention time (up to 20 minutes) is required to
adequately separate and stabilize a given quantity of oil
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WELL PROBLEMS AND SOLUTIONS
pg. 61 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
The main factors that assist in "breaking" foaming oil are:
1. Settling or retention time
2. Agitation
3. Heat
4. Chemicals (ex. Foam breakers or solvents w/silicone additives)
5. Vortex inlets
Paraffin DepositionParaffin deposition in oil and gas separators reduces their efficiency and may
render them inoperable by partially filling the vessel and/or blocking the mist
extractor and fluid passages. Paraffin can be effectively removed from
separators by steaming or by use of solvents.Paraffin buildup downhole can cause serious reduction in production to the
point of complete blockage. Some of the possible solutions employed, may
include:
Wireline scrapping
Hot oil treatments/circulation
Bacteria injection (certain types feed on paraffin)
Liquid Load up in Gas WellsThe occurrence of liquid loading up in the flowing tubing or annular string is
usually associated with wells of low to moderate gas productivity and high
water or oil to gas production ratios.
Initial indications of liquid in the hole may be an unusually low shut-in
wellhead pressures and/or a large difference between tubing head and casing
head pressures if there is no packer in the hole.
Hydrating ConditionsThe formation of hydrocarbon ice crystals or hydrates will occur at any point in
a gas or liquid hydrocarbon flow system, where the temperature reaches the
hydrate point for the pressure condition and the nature of the fluid in the system.
As a general rule, the hydrating temperature rises with higher pressures, and
starting with methane, also rises with the higher carbon components.
Since the throttling of a stream causes a drop in temperature by expansion, someof the common hydrating points on a surface flow system are:
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WELL PROBLEMS AND SOLUTIONS
pg. 62 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
Chokes
Valves
Orifices
Sharp bends or restrictions in piping
Sand, MudSand production is more likely to occur with high productivity wells. The sand
may originate from the formation rock and be "sloughed off" into the wellbore,
or it may be sand recovered following a frac stimulation job. The risk of sand
production increases with higher drawdowns. Underbalanced perforating is
believed to produce perforations which are cleaner and less prone to sand
production because of reduced differential pressures at the perforations. Otherservices that may be employed, depending on the wells parameters, include:
Gravel packs / sand screens
Sand consolidation treatments
Sand production can be monitored at surface by:
BS&W samples at the choke manifold.
Erosion probes at choke manifold
Sand detectors measure the acoustical noise created by sand impinging
eitheron a probe in the flow stream or on the internal wall of the flow pipe.
H2SHydrogen sulfide, H2S, often called "sour gas," packs a double barreled punch.
H2S is a poisonous gas. There is the indirect threat to human safety caused by
H2S attack on metals, especially steel, used in pressure control equipment. H2S
is a colourless, flammable gas having an offensive odour and sweet taste. The
smell at low concentrations is similar to that of rotten eggs.
SymptomsExposure results in irritation, principally smarting of the eyes, a persistent
cough,
Tightening or burning of the chest, and skin irritation. There is no known
antidote for H2S.
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WELL PROBLEMS AND SOLUTIONS
pg. 63 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
General Well Trends
CLEAN-UP PHASE
Wellhead pressure
Wellhead pressure will drop from the shut-in pressure as the well is opened
to flow.
Wellhead pressure will increase ass the fluid cushion and extraneous fluids
are replaced by lighter reservoir fluids
Wellhead pressure will slowly decrease with depletion of the reservoir
Wellhead Temperature
Well head temperature will increase with the flow of hot reservoir fluids
Wellhead temperature will stabilize with well flow stabilization
Annulus Pressure
Anuluspressure maybe altered for the operation of annulus pressure (apr)tools.
Annuluspressure will increase with the flow of hot reservoir fluids
Annuluspressure will stabilize with well flow stabilization
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WELL PROBLEMS AND SOLUTIONS
pg. 64 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
BS&W Extraneous fluids will decrease and eventually dissipate
Water cut will stabilize
Salinity
Salinity will stabilize near formation water
PH After acidizing, waterpH will Steadily move toward 7.
H2S H2Slevels win increase then somewhat stabilize
Co2 Co2 levels will stabilize
Downstream of Choke Pressure
Pressure downstream of the choke will dependent upon wellhead pressure,
choke Size, fluid flow rates and test systems
Critical now conditions should exist
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WELL PROBLEMS AND SOLUTIONS
pg. 65 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
Downstream of Choke Temperature will be less than well head temperature
due to expansion at the choke causing a cooling effect
Tank Volume
Extraneous liquid return will be initially high. Rates will be whp/choke
dependent
Flare/Burner
Quality ofburn will initially indicate the return of extraneous fluids.
Quality and intensity of fire will improve with the production of higher
percentages of reservoir fluids
Oil burner pressure will be dependent upon flow rate and nozzle(s)
arrangement; stabilizes with well flow.
Problem Solving Abnormal Trends
Clean-Up phase
Symptoms Cause ActionWell head Presure
Increasing Choke plugging Adjust choke
Choke Hydrates Use Heater
Chemical Injection
Increase Rate
Low Productivity Well
Continuing Clean-up
Nothing-Normal
Unloading of liquid in
in surges
Increase or Decrease
Choke Setting
Decreasing WellLoading Up Normally increase
Choke Size
Choke Cutting Inspect
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WELL PROBLEMS AND SOLUTIONS
pg. 66 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
Wellhead Temperature
Decreasing Tubing hydration Reduce Rate
Chemical Injection
ShutIn
Annulus Pressure
Increasing Test String Leak Bleed Off
Possible Shut-In
Decreasing Test Siring Leak
Packer Leak
Abort IfNecessary
BS&W
Increasing Water ConingSand Production
Reduce Rate
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WELL PROBLEMS AND SOLUTIONS
pg. 67 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
Downstream of Choke Pressure
Increasing Choke Cutting
Downstream Restriction
Check Flow System
Decreasing Choke Plugging Adjust choke
Hydrate Formation Determine Hydrate
Point.
Adjust Choke, Use
Heater,
Chemical Injection
Downstream of Choke Temperature
Decreasing Larger Pressure Drop Stage chokes, Remain In
Critical Flow, Use
Heater
Choke Plugging Adjust choke
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WELL PROBLEMS AND SOLUTIONS
pg. 68 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
Oil Burner Pressure
Increasing Nozzle Plugging Clear Nozzle
Decreasing Nozzle Cutting
Rate Declining
ReplaceNozzle
Stable Well Flow
Wellhead Pressure & Temperature will have stabi1ized at the end of clean-
up Annulus Pressure With stabilization of well flow; it will have stabilized
BS&W
Basic sediment should be insignificant
Water cut should be relatively constant
Salinity Should be relatively constant
Downstream of choke pressure
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WELL PROBLEMS AND SOLUTIONS
pg. 69 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
With stable well now and critical flow at choke, downstream pressure will be
dependent upon Separator
Downstream of choke temperature
Will increase with decrease of pressure drop across the choke, will decrease
with increase ofpressure drop
Heater Temperature
If necessary, will be Stable provided stability of well flow and thermostatic
control
Separator Pressure
Willbe stable after final settingof controls
Separator Temperature.
Will be relatively constant provided heater temperature and/or well flow are
stable
Gas Measurement
Pressure Upstream of Orifice Effectively equal to separator pressure
Pressure downstream of orifice (Static) Slightly less than separatorpressure;
with stable flow. will increase with higher separator back pressure And/or
larger orifice plate size.
Differential Pressure
With stable flowdeviation of pressure upstreamand downstream of orifice is
dependent upon separator pressure & and orifice size; variance win increase
with decrease of separator pressure and/or small orifice.
Downstream Gas Temperature
Will be less than separator temperature due to expansion
Gas Specific Gravity
With stable well and separator conditions will be relatively constant: may be
seen to vary inversely with separator pressure
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WELL PROBLEMS AND SOLUTIONS
pg. 70 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
H2S - Will be increasing constant
Co2- Willbe relatively constant
Oil Measurements
Oil Flow rates - With stable now will be relatively constant
Oil Temperature-Willbe close to separator temperature.
Oil API Gravity- With stable ratewill be relatively constant
BS&W- Water cut should be negligible
Shrinkage - Maybe seen to vary directly with changes in separatorpressure
Water Measurements
Water Flow rates With stable flow willbe relatively constant
GOR Saturated Oil Reservoir Will initially increase then stabilize
Other Reservoirs With stable flow should be relatively constant
Separator GOR - Will be affected by separator conditions; increases with
decreasing separatorpressure increases with increasing temperature.
Problem Solving Abnormal Trends
Stable Well Flow
Symptoms Cause Action
Well head Pressure
Increasing Choke plugging Adjust choke
Choke Hydrates Use Heater
Chemical Injection
Increase Rate
Low Productivity Well
Continuing Clean-up
Nothing-Normal
Unloading of liquid inin surges
Increase or DecreaseChoke Setting
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WELL PROBLEMS AND SOLUTIONS
pg. 71 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
Decreasing WellLoading Up Normally increase
Choke Size
Choke Cutting Inspect
Wellhead Temperature
Decreasing Tubing hydration Reduce Rate
Chemical Injection
ShutIn
Annulus Pressure
Increasing Test String Leak Bleed OffPossible Shut-In
Decreasing Test Siring Leak
Packer Leak
Abort IfNecessary
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WELL PROBLEMS AND SOLUTIONS
pg. 72 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
BS&W
Increasing Water Coning
Sand Production
Reduce Rate
Downstream of Choke Pressure
Increasing Choke Cutting
Downstream Restriction
Check Flow System
Decreasing Choke Plugging Adjust choke
Hydrate Formation Determine Hydrate
Point.
Adjust Choke, Use
Heater,
Chemical Injection
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WELL PROBLEMS AND SOLUTIONS
pg. 73 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
Downstream of Choke Temperature
Decreasing Larger Pressure Drop Stage chokes, Remain In
Critical Flow, Use
Heater
Choke Plugging Adjust choke
Separator Static Pressure
Increasing Back Pressure Problem Examine Controller/
Valve
Action
Downstream Restriction Check flow System
Decreasing Back Pressure Problem Examine Controller/
Valve
Action
Wrong Valve open Check Relief, Drain,
Liquid valves for exit
point
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WELL PROBLEMS AND SOLUTIONS
pg. 74 YENNAI HYDROCARBONS AND SERVICES PVT. LTD.
Upstream Restriction Check flow System
Erratic Back Pressure Problem Examine controller/valve
Action: If cycling,
increase
P.B: If hunting, Decrease
Below Bubblepoint Reduce Rate: Put more
Back pressure on well
Separator Differential Pressure
Increasing Choke Cutting Verify WHP Drop
Replace Choke
Liquid or Leak In
Barton Downstream Line
Drain or Inspect
With Soapy Water
Temperature Increase Ambient or Heater
Decreasing Choke Plugging Verify WHP Drop
Adjust Choke
Liquid or Leak In
Barton Downstream Line
Drain or Inspect
With Soapy Water
Temperature Decrease Ambient or Heater
Separator Oil Meter Rates
Increasing Passing Gas Raise level, prove meter
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WELL PROBLEMS AND SOLUTIONS
pg 75 YENNAI HYDROCARBONS AND SERVICES PVT LTD
at tank
Decreasing Damaged Meter Use Secondary Meter
repair/replace parts
Erratic Wrong Sensitivity Adjust Proportional band
setting
BS&W
Increasing Water level height Lower water level
Separator Water meter rates
Increasing Passing gas Raise level, prove meter
at tank
Decreasing Damaged Meter Use secondary tank
repair/Replace parts
Tank ReadingsErratic Foamy Oils, Emulsions Allow More Retention
Time. Use two
Compartment vessel
Liquid Densities Drain off Heavier liquid
to improve u-tube in
sight glass
Oil Burner Pressure
Increasing Nozzle Plugging Clear Nozzle
Decreasing Nozzle Cutting
Rate Declining
ReplaceNozzle
Flare visual
Abnormal Burn Separator Liquid Lower liquid Level,
checkSeparatorValving
for Exit Point