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86 Cards in this Set

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What is a workover?
It is an intervention in a completed well.
Why are workovers performed?
For Data gathering (cased hole logging - production or injection logging)
Integrity monitoring on tubing, casing , and/or packers
Well repair
To Improve performance (production/injection)
How do workovers imporove production/injection?
You can cleanout debris, solids, formation solids, deposited solids.
Flow assurance preventative or remediation. Stimulation artificial lift, and you can change intervals connected to the reservoir.
Shutoff flow from/to an interval (plug isolate)
Deepen or sidetrack well
What type of surface equipment can be used to do a workover?
Through Wireline
Fullbore pumping of fluid/chemicals through well tubing
Through Tubing
By Pulling tubing
When pumping through tubing intervetion with a coiled tubing cleanout what are the steps to make a wellbore clean?
you fill covering perfs and then forward or reverse jetting to remove the excess crap
How do you plug the bottom interval?
Bottom perfs watered out
use coil or work string to lay sand, cement (and/or plug)
How does a cement squeeze operate to seal performations?
Protect the oil zone
push cement down to the perfs then remove wellbore cement
Then remove the protection for the oil zone and return to service
What are common causes of excess water production?
Open water zone
flow behind pipe and casing leaks
Channeling from injector or aquifer via fracture/fault
coning or cusping
What are the two classes of chemical watershut off?
matrix-penetrating gelant
flowing gel (can only enter fractures or other larger features)
How do you design a matrix gel treatment?
Treat matrix depth to withstand expected pressure change
Account for voids, uneven penetration, losses
Pressure response may dictate volume change
Use established zone isolation options
What are the established zone isolation options?
bridge plug
sand plug
inflatable packer or retainer
dual injection with protective fluid
What is a bullhead shutoff?
A shutoff to push gel into a fracture to block the water produced from there without damaging the formation
What are the safety valves used for?
To shut off flow if equipment above mud line is damaged.
Where were safety valves initially developed for?
Offshore wells
What are the different types of valves?
Ball Valves
Butterfly valves
gate valve
flapper valve
pneumatic surface safety valve
hydraulic surface safety valve
What are the difference between flapper valve vs ball valve?
Flapper valve is simpler to operate (sliding sleeve vs rotation)
Flapper valve less affected by scale, paraffin
What are chokes used for?
Used to slow flow down
What are the two types of choke?
Fixed (also known as positive)
Adjustable
How do chokes work?
They limit production rate by increasing bottom hole flowing pressure
Why would you use chokes?
Regulations
Slugging, problems handling raet at surface
Sand Production
Water or gas coning
Other reservoir management items
What are the typical choke valves
Classic adjustable choke
subsea retrievable choke
What are the general pump types?
Centrigual pump
Positive Displacement
Gas Lift
Jet, Eductor
What are the different positive displacement pumps?
piston
Diaphragm
Progressing cavity
What are centrifugal pumps used for?
Large volume
Low Pressure
Low Viscosity
Generates high shear as fluid passes through vanes.
These pumps cannot self-prime
It does poorly with liquid + gas combination
What are centrifugal pumps based on?
Based on the concept of raising the pressure of a liquid indirectly by increasing the kinetic energy via the centrifugal action of the impeller and converting this kinetic energy to the P/pho term.
They can be used for a wide flowrate range but a narrow pressure range
What are positive displacement pumps based on?
It works on the principle of letting fluid flow into a cavity from a low pressure source, trapping the fluid, and forcing it out to a high pressure receiver by decreasing the volume of the cavity
They can be used for a narrow flowrate range, but a high pressure increase range
What are reciprocating piston pumps usually used for?
Crude oil
What are the two types of reciprocating piston pump?
Single action (used for pumps with 3 or more pistons, and provides higher pressure)
Double action piston stroke (used for duplex pumps, provide higher flow rates)
What is a Diaphragm Pump used for?
Viscous fluid or slurries
Low Rate
Low Pressure
It is pneumatic operates
What do we separate?
Gas (C1-C4, H2S, CO2, N2)
Oil
Water
Dissolved Solids
Solids
What are the key principles are used in separators?
Density and Gravity
What can be done to increase the efficency of separators?
Add mist extractor
Add baffles and diverters and residence time
Use centrifugal force to increase gravity
Vertical Two Phase Separator are meant for what?
A low GOR and a low total output.
What problem can be caused by low flowrate in a Vertical Two Phase Separator?
Gas blowby, because the fluid level is not high enough
What are the two constraints in picking a separator?
It must be able to contain gas and liquid. The liquid must be able to stay long enough so that the gas can separate from the liquid.
What is the retention time needed for a liquid droplet to attain gas-liquid equilibrium?
.5 -3 mins
What is the controling parameter for low pressure with low GOR in a separator?
Liquid Capacity Constraint
When is artificial lift needed?
When there is insufficient reservoir energy to produce reservoir fluids to surface at adeguate rates
What are the two different flowing pressure regimes that need improvement?
Low Pwf - Better IPR, poor VLP
High Pwf - Better VLP, poor IPR
What is artifical lift designed to help?
Intake side for low pressure (for IPR)
and Discharage side for high pressure (for VLP)
What percent of wells need Artifical Lift?
50%
What are the two main methods for artificial lift?
Gas Lift (add natural gas to tubing via annulus)
Bottom Hole Pumping (Sucker Rod Pump, ESP, ect)
How does Gas lift work?
By injecting gas into the lower part of production tubing, the gas aerates the flowing fluid, reducing the fluid comlumn hydrostatic pressure. This lowers bottom hole pressure
How does Bottom Hole pumping work?
It boosts transfer of liquid to wellhead by increasing pressure at turbing inlet. This decreases Pwf by transferring fluid more rapidly to tubing at higher pressure
When is gas lift chosen for artifical lift?
When there is gas available in moderate to deep wells with high fluid rates. There can be a low or high GOR as long as the oil is not heavy. Solids are okay, but may increase maintenance cost. They are low to moderate expensivily when first put in place, but have a lot of maintenance required.
When are rod pumps used for artifcial lift?
When there is low or no free gas in a low pressure well that has a low to fairly high flowrate. There can be any type of oil as long as the hole is straight.
When are ESP's used for artificial lift?
When there is a moderate to deep well with high flow rate. The well can be any type of deviation but it requires a low GOR and a light oil because it can't handle high viscosity. They are very expesnive to put in and to maintain.
Why don't gas lift or pumps have to be set at the bottom?
The depth must just be deep enough to give you the Pwf you need for the rate desired.
What are the two types of gas lift operations?
Continuous (steady state flow to surface)
Intermittent (start and stop flow to surface)
How does a suck rod pump move oil?
Rotary motion of crank
translated to
reciprocating motion of
polished rod
 Sucker rod transmits
reciprocating motion of
rod to down-hole pump
 The pump with barrel
(with standing valve) and
plunger (with traveling
valve)
 When plunger moves
up, standing valve opens
to fill barrel with fluid
 On down stroke,
traveling valve opens so
fluid in barrel is displaced
into tubin
How do you determine the pressure increase needed for a sucker rod pump?
 Input pressure to pump:
• From IPR, determine bottom-hole flowing pressure
(Pwf
) at the given reservoir pressure and desired
production rate
• Subtract pressure drop in wellbore from bottomhole location to location of pump to bottom-hole
flowing pressure
 Output pressure from pump:
• From VLP (pressure drop in wellbore), determine
the pressure above the pump for the given surface
tubing pressure at the desired production rate
What are some common ESP issues with C-PUmps?
There are cavitation problems (gas and heavy oil or any vicous fluid)
Erosion or efficiency decerase by solids
What are some common ESP issues with their motors?
The heat (when placed above fluid inflow)and when the ESP is placed deep in the well the running temp will be much higher.
What are some common ESP issues with cost?
Very expensive to install and repair (because you need to pull tubing)
How do you design a ESP?
pick the flowrate desired, then choose the pump that can produce that flowrate. From that pump determine the pwf that it will produce. With that pwf find the depth needed to produce, and then find the required discharge pressure. Then determine the Pump pressure and head requirements. Form this find the total power requirement.
Why meter flow in the industry?
b/c you need to know what is going where accurately
Where is measurement needed?
at each major step (from separator to treating facilties to storage/transport lines)
What can metering be used for?
reservoir management, prdouction optimization, history matching, well testing, production allocation, custody transfer, fiscal metering, downhole metering and allocation.
Why is metering accuracy required?
With large flowrates, small inaccuracies can cost companies large amount money.
What is linearity when dealing with a meter?
the deviation of the meter's response is within a certain percent of an ideal relationship between flow rate variations and output
What is error when considering meters?
the difference between the meter output and the true value of the flow rate at the time of the mesaurement.
What are some types of flow measurement devices?
turbine meter
orifice plate meter
venturi meter
coriolis meter
ultrasonic meter
What are the basic flow metering concepts?
conservation of mass, energy and momentum
friction
reynolds number
gas laws
liquid expansion
What are the two different types of pressure measurements for a flow meter?
Hydrostatic pressure and dynamic pressure
What are common causes of sand production?
Poorly Consolidated formation
Decrease in reservoir pressure
Drag Forces (high flow rate and/or water breakthrough)
What are common sand production problems?
solid buildup in wellbore
additional pressure drop
voids behind pipe (loss of zone isolation and/or casing or hole collapse)
erosion of turbulars
solids fill surface vessels
What are common sand control methods?
Live with it
Control production rate (drop it)
Put a screen in the wellbore
Gravel Pack
Frac and Pack
Chemical consolidation
Slotted liners are used where?
Because they are simple and inexpensive, they are used in many horizontal open holes to prevent hole collapse. However they are not very effective at filtering small grains.
What are classic wire-wrapped screens used as?
They are used alone b/c the wrapped wire is usually keystone shaped and the material that passes through the outer constiction continues to flow through the screen.
It can also be used inside the gravel pack.
What is a pre packed screen?
A screen that filters sand, however since it is pre packed with uniformly sized sand, it allows for better filtration with minimum flow restriction.
What is a premium stainless mesh filtration screen? Why do they fail?
It has a small mesh to filter solids and fines, however they fail due to plugging or erosion
What are expandable screens used for?
To hold the formation in place and to filter sands and fines
How do expandable screens expand?
Either a fixed cone is pushed down the drillstring to expand it. or pressure cycling from a hydraulic expansion tool causes it to expand
What is important for a gravel pack?
Formation grain size distribution
What is a gravel pack made of?
Sized particles placed in the annular space between an unconsolidated formation and a centralized screen
How is a gravel pack placed?
First a screen is placed, then gravel is filled in the hole to stabilize the hole and sands formation.
What is insitu consolidation?
A resin or other "glue" is pumped down the well to the formation to cement the formation sand grains together.
What is resin coated gravel?
heat or chemicall set material pre coated on properly sized gravel pack grains. They are put in place, cured, and then drilled out to keep formation in place and act as a screen.
What are common production problems?
low productivity
excessive gas production
excessive water production
sand production
liquid loading (only in gas wells)
How do you diagnosis what the causes of a production problem is?
By doing pressure transient testing to determine factors affecting reservoir inflow perfomrnane
Production logging to determine actual production profile and pressure profile in wellbore
Production and pressure history - acutal data
What are causes of low productivity?
Reservoir issues (lower than expected reservoir properties, low relative permeability, heterogeneity)
Flow restictions near wellbore (formation damage, plugged completions)
wellbore restictions
How do you diagnosis low productivity?
Meaure reservior (kH) and skin from pressure transient testing
Caliper log (identify any wellbore restiction)
production logging - identify location and vertical extent of impairment
What are the causes of gas or water production?
casing leaks or channeling behind casing
preferential flow though high permeability zones
coning (gas from top/ water from bottom)
connecting fracture systems for water
How do you diagnosis gas or water production?
For casing leaks
cement bond or ultrasonic logs
production lgos for flow behind casing
remedial action - cement squeeze

For preferential flow through high permeability zones
production logs - determine flow profile and entry location
run a cement squeeze

Coning
Run production logs - determine flow profile and entry location.
Vary production rate or drawdown to determine if conning issues is rate senstive
Cement Squeeze or plug perfs
What are causes for liquid loading?
droping reservoir pressure and gas flow rate
increasing bottom hole pressure with liquid accumulation
flow going from annular flow to slug to bubble flow
How do you remediate liquid loading?
foaming liquid flow
smaller tubing or lower surface pressure
gas-lift or pumping liquid
heating the wellbore
downhole liquid injection