Chapter 5 Flashcards
What are the main objectives for well logging
To provide information for reservoir evaluation.
To gather data for well completion and repair.
Describe how well logging works
➢ A logging set-up consists of the wire, a wireline tool, a
winching gear and a vehicle which contains appropriate
data analysis and recording equipment.
➢ The actual running of a log involves lowering a tool at
the end of a logging cable into an oil/gas well. A
sensor, incorporated in a sonde together with its
associated electronics, is suspended in the hole (well)
by a multiconductor cable.
➢ Data is transmitted to the control panel at surface
through the wire and recorded digitally. All data
recording and processing is now done digitally using
powerful computers and processors.
➢ As the cable is raised or lowered, it activates some
depth-measuring device, which in turn activates a
recording device.
➢ Finally, some form of reproduction takes place to
provide a hard copy of the recorded data which is
called the well log.
The Sonde was the first well log tool. What did it measure
It measures electrical resistivity
List well logging applications
➢ Lithology identification.
➢ Determination of reservoir characteristics (e.g. porosity, saturation, and
permeability.
➢Identification the fluid type in the pore space of reservoir rock ( gas, oil,
water).
➢ Identification of productive zones and reserves.
➢ Determination the depth and thickness of productive zones.
➢ Reservoir properties mapping.
➢Determination formation dip and hole angle and size
➢Monitoring the reservoir parameters when production is in progress.
What is non-conductive boreholes
oil-based and air-based muds and
cased holes
What is Conductive boreholes
Water-based drilling mud
What are the types of well logging
Mud logging
Open hole logging
cased hole logging
production logging
Describe mud logging
During drilling mud is pumped down the drill string forcing the rock cuttings
up to the surface. These cuttings are analyzed by laboratory analysis working
in a transportable laboratory known as a mud logging unit installed at the well
site.
What an the samples from mud logging tell us about the well
✓ Rate of penetration (ROP)
✓ Determination of lithology
✓ Presence of hydrocarbons
✓ Preliminary indication of the well location (seismic data)
✓ Indication of pressure conditions
✓ Monitoring of bit performance
✓ Weight on bit
✓ Mud weight
✓ Estimated pore pressure
What are the types of well logging used for open hole logging
a. Wireline Logging (WL): Electrical logs, Sonic logs, Caliper logs,
Dipmeter logs and Radioactive logs
b. Logging while drilling (LWD)
Describe wireline logging
➢ The tools are introduced into the well on a cable, the
obtained data are transmitt to the surface recording system via
cable.
➢ Performed after interuption or termination of drilling in this
situation, drilling pipes and bit should be out and well be empty.
Describe logging while drilling
➢ The logging device is introduced on the drill pipe and
collected data are memorized in the tool, the data are
downloaded to the surface recording system after termination
or interuption of drilling.
➢ Very efficient in horizontal drilling.
➢Indications of reservoir rock and fluid quality while drilling.
➢ Some tools also are able to record drilling parameters such
as RPM and drilling speed.
What do electrical logs measure
electrical properties of the
formation rock and fluid.
What do caliper logs measure
Measure the geometry of the wellbore.
What do dipmeter logs measure
Measure the dip of the formation.
Wat do sonic logs measure
Measure the elastic or wave properties of the formation
What do radioactive logs measure
Gamma ray measures the radioactive absorption properties
Fill in the blanks
Cased hole and production logging:
This type is used ______ well completion.
A concrete lining or casing has be inserted to ________ the wellbore.
The portion of the well bore that has had metal casing placed and
cemented to protect the open hole from _______, _______, well bore
_________ problems or a combination of these
after
stabilize
fluids, pressures, well bore stability
What are the two most important cased hole logs
cement bound logging (CBL) and variable density logs (VDL)
Fill in the blanks:
Drilling a hole in the formation will cause a disturbance in the vicinity of
bore hole by the invasion of drilling mud into the formation.
➢ Ideally the size of the borehole is ______ to the size of the drill bit.
➢ Shale swelling, salt dissolution and collapse of poorly cemented rocks
may ________ the borehole diameter.
➢ Mud cake build up may ________ the size of the borehole diameter.
➢ The change in the borehole diameter and the contamination caused by
the drilling mud will affect the ________ ______ and appropriate corrections
should be considered.
Equal
increase
decrease
logging tools
What are the characteristics that affect log quality
Depth of investigation
Logging speed
Vertical resolution
Investigation geometry
Describe how depth of investigation affects log quality
Depth of investigation: Depends on the porosity of formation. Different
logging tools, has different characteristics, however, most of them have
shallow depth of investigation which can mostly reach the flushed zone or
transition zone.
Describe how logging speed affects log quality
The running speed of the tools will cause statistical
fluctuations and sampling interval variations. These can affect the vertical
resolution.
Describe how vertical resolution affects log quality
This is related to the depth of investigation. The bed
thickness should be larger than the distance between the source and
detector of each logging tool. Generally, logging tools with large depth of
investigation have low vertical resolution.
Describe how investigation geometry affects log quality
Different logging tools have different measurement
geometries.
What does invasion represent
The difference between the fluid pressure and drilling
mud pressure will cause a flow of the drilling fluid to the
formation in the permeable zones of the borehole
What does mud cake represent
The formation rock acts as a filter and keeps the
particulates of the mud at the borehole wall, this particle
build up on the wall is called mud cake
What does mud filtrate represent
The remaining liquid part of the mud which enters the
formation is called mud filtrate
What does the flushed zone represent
Mud filtrate will replace the reservoir fluid and enters the
formation, this zone where the reservoir fluid is replaced
is called flushed zone
What does the transition zone represent
The zone next to the flushed zone further into the
formation where the mud invasion is incomplete is called
transition zone.
What does the uninvaded zone represent
The untouched portion of the formation by the mud is
called uninvaded zone
Fill in the blanks:
High permeability formations results in _______(shallow or deep)
invasion and ______(thin or thick) layer of mud cake.
deep
thick
Fill in the blanks:
High porosity formations results in _______(more or less) storage
of mud filtrate per invasion distance and the
________(smaller or larger) depth of invasion.
more
smaller
Wireline companies provide correction graphs for
their logging tools to consider the effect of
__________ on well logging readings.
invasion
What does the log display and structure include
- Logging company and log name.
- Well identification and location information.
- Other log and services run in the well.
- Depth and elevation details.
- The log run number.
- The depth of the bottom of the hole.
- The depth of the top and bottom of the logged interval.
- Casing information
- Bit information.
- Drilling mud information
- Mud, mud filtrate and mud cake resistivities.
- Time between end of logging circulation before logging and when
logging tool reached the bottom of the hole. - Temperature.
- The logging truck information.
- The logging company representatives information
What does the bubble point curve represent?
Represents the conditions of temperature and pressure at which the first bubble occurs when u drop the pressure or increase the temperature.
The bubble-point curve (line BC) is defined as the
line separating the liquid-phase region from the two-phase region.
What does the dew-point curve represent
Represents the conditions of pressure and temperature at which the first droplet of liquid forms when a gas is cooled and/or the pressure is increased.
The dew-point curve (line AC) is defined as the line
separating the vapor-phase region from the two-phase region.
What is the Circondentherm (Tct)
—The Cricondentherm is defined as the maximum
temperature above which liquid cannot be formed regardless of pressure.
The corresponding pressure is termed the Cricondentherm pressure pct.
What is the Circondenbar (Pcb)
The Cricondenbar is the maximum pressure above
which no gas can be formed regardless of temperature. The corresponding
temperature is called the Cricondenbar temperature Tcb.
What does the critical point represent on a P-T diagram
The critical point for a multicomponent mixture is referred
to as the state of pressure and temperature at which all intensive properties
of the gas and liquid phases are equal (point C). For the two-phase system
at this point both phases coexist. At the critical point, the corresponding
pressure and temperature are called the critical pressure pc and critical
temperature Tc of the mixture.
Describe an undersaturated oil reservoir
In these reservoirs the initial reservoir pressure is greater than the bubble
point pressure of the reservoir fluid (pi> pb). No free gas exists until the
reservoir pressure falls below the bubble point pressure.
This includes when PR < Pb(gas section and oil section - gas cap reservoir) and also when PR > Pb (No gas section, all is dissolved in the oil).
Describe a saturated oil reservoir
In these reservoirs the initial reservoir pressure is equal to the bubble-point
pressure of the reservoir fluid (pi= pb). At this point the gas begins to separate from the oil (PR = Pb) and form a gas cap.
What are the types of crude oils
Ordinary black oil
Low-shrinkage black oil
Volatile crude oil
Near critical crude oil
What is the gas-oil ratio, oil gravity, and colour for ordinary black oil
200-700 scf/STB
15-40 API
Brown to dark green
What is the oil formation volume factor, gas-oil ratio, oil gravity, and colour for low-shrinkage black oil
less than 1.2 bbl/STB
less than 200 scf/STB
less than 35 API
black or deeply coloured
What is the oil formation volume factor, gas-oil ratio, oil gravity, and colour for volatile crude oil
less than 2 bbl/STB
2000 - 3200 scf/STB
45-55 API
greenish to orange
What is the oil formation volume factor, gas-oil ratio, and how much heptane’s and ethane’s for near critical crude oil
higher than 2 bbl/STB
excess of 3000 scf/STB
12.5 to 20 mol% heptanes-plus,
35% or more of ethane through
hexanes, and the remainder
methane.
What do we classify the reservoir if it is above critical point
This is a natural gas reservoir
What are the types of natural gas reservoirs
Retrograde gas-condensate reservoir
Near critical gas-condensate reservoir
Wet-gas reservoir
Dry-gas reservoir
What is the gas oil ratio, condensate gravity and colour of a retrograde gas-condensate reservoir
- Gas-oil ratios between 8,000 to 70,000 scf/STB.
- Condensate gravity above 50°API
- Stock-tank liquid is usually water-white or slightly colored.
What is the gas oil ratio, condensate gravity and colour of a near critical gas-condensate reservoir
- Gas-oil ratios between 8,000 to 70,000 scf/STB.
- Condensate gravity above 50°API
- Stock-tank liquid is usually water-white or slightly colored.
What is the gas oil ratio, condensate gravity and colour of a wet-gas reservoir
- Gas oil ratios between 60,000 to 100,000 scf/STB
- Stock-tank oil gravity above 60°API
- Liquid is water-white in color
What is the gas oil ratio of a dry-gas reservoir
greater than 100,000scf/STB
As we go from a liquid to a gas in a reservoir, the gas-oil ratio increases or decreases?
increases
As we go from a liquid to a gas in a reservoir, the stock tank oil gravity (API) increases or decreases?
increases
As we go from a liquid to a gas in a reservoir, the colour becomes lighter or darker?
lighter
For a retrograde gas-condensate reservoir, where does the T lie?
the reservoir temperature T lies between the critical
temperature Tc and cricondentherm Tct of the reservoir fluid.
For a near critical gas-condensate reservoir, where does the T lie?
the reservoir temperature T is close to the critical
temperature of the reservoir fluid
For a wat-gas reservoir, where does the T lie?
the reservoir temperature T is above the
cricondentherm of the reservoir fluid. They contain significant heavy
hydrocarbons such as propane, butane and others
Does the hydrocarbon mixture from a dry-gas reservoir stay as a gas in both the reservoir and surface
yup
What are the natural drive mechanisms
Rock and liquid expansion drive
Depletion drive
Gas cap drive
Water-drive mechanism
Gravity-drainage-drive mechanism
Combination-drive mechanism
Describe rock and liquid expansion drive
The pressure in the reservoir is reduced, which causes the expansion of the individual rock grains as well as formation compaction. This reduces the fluid pressure and the porosity. This mechanism is an unfavorable energy source for oil reservoirs.
Describe the depletion drive
Source of energy is from the release of gas from the crude oil and expansion of the gas as the reservoir pressure is reduced. The expansion
of the gas will force the oil from pore spaces to the wellbore.
Describe the gas cap drive
sources of energy are the expansion of the gas-cap and the expansion of the solution gas as it is liberated.
These reservoirs typically have low water content.
Which of the following increase the oil recovery for a gas cap drive. : Size of the original gas cap, Vertical permeability, Oil
viscosity, Degree of conservation of the gas, Oil production
rate, and Dip angle .
Size of the original gas cap, Vertical permeability, Degree of conservation of the gas, and Dip angle .
Describe the water-drive mechanism
source of energy is from the expansion of water.
The gas cap is small, but provides expansion energy
Describe the gravity drainage system
The source of energy is from the differences in densities. his causes gravity drainage.
Which of the following factors increase recovery from gravity drainage reservoirs: Permeability in the direction of dip, Dip of the reservoir, Reservoir producing rates, Oil viscosity
Permeability in the direction of the dip and dip of the reservoir
Describe combination drive mechanisms
reservoirs which have more than one energy drive. They can be more complicated for estimation purposes
What is the inflow performance relationship (IPR)
it is the relationship between the flow rate of the well q and the flowing pressure of the well pwf.
When is the IPR a straight line
When is it in a single phase flow
When is the IPR not a straight line
when it is at a pressure below the bubble point
Outflow performance relates to estimating the pressure rate relationship in the __________ as the reservoir fluids move to the _________ from bottomhole through tubulars
wellbore
surface
As much as ___% of the total pressure loss in a flowing well may occur
during the fluid lifting to the surface.
80%
How would we find the well deliverability
Combining the IPR and TPR curves and finding the
intersection of these curves will yield the deliverability point.
the IPR represents what the _________ can deliver, and
the TPR represents what the ________ can deliver
reservoir
well
Describe an artificial lift.
a method to boost the production rate from
producing wells. This can be used when pressure or flow rate is low.
Pumps are installed to provide lift pressure or gas injection to decrease hydrostatic pressure in the wellbore.
What are the major types of artificial lifts
beam pumping
Electrical submersible pumping (ESP)
Hydraulic pumping
Gas lift
What are the two types of artificial lift pumps
Positive displacement pumps
Dynamic displacement pump
Describe the positive displacement pump
These pumps move fluid from a suction chamber to a
discharge chamber. The examples of such pumps are reciprocating rod pumps,
hydraulic piston pumps and progressive cavity pumps (PCPs).
Describe the dynamic displacement pump
These pumps will force the fluid to move from inlet to
outlet under its own momentum. The examples of these pumps are electrical
submersible pumps (ESPs) and hydraulic jet pumps.
Describe Beam pumping
designed to be inserted inside the tubing. The pump is connected to the surface facilities by a string of sucker rods.
What are advantages of beam pumping
✓Low repair and maintenance costs
✓Can be adjusted to different production rates by changing the
speed and length of strokes
✓The salvage value is high for downhole pump and surface
beam unit
What are the disadvantages of beam pumping
✓Limited to low production rates (less than 1000 STBD)
✓Applicable only to onshore wells
✓Limited application for deep, inclined and horizontal wells
describe a progressive cavity pump.
Fluid is transferred as the rotor turns, and the cavities between the rotor and stator move upward
Fill in the blanks for a progressive cavity pump description: They are versatile, generally very efficient, and excellent for handling fluids with
high ________ content. They are not good choices for _______ wells due to torsional stress and
temperature limits.
solids
deep
Describe a hydraulic pump
Hydraulic pump systems use a power fluid (usually
light oil or water) that is injected from the surface to
operate a downhole pump.
What are the types of hydraulic pumps
reciprocating hydraulic pump and jet pump
fill in the blanks: The main advantage of _________ _______ is that
multiple wells can be produced using a single surface
power fluid installation
Hydraulic pumps
What are the advantages of a hydraulic pump
✓Can be used at depths from 1000 to 17,000 feet.
✓Capable of producing at rates from 100 to 10,000 B/D.
✓Can be hydraulically circulated in and out of the well, thus eliminating the need for
wireline or rig operations to replace pumps and making this system adaptable to changing
field conditions.
✓Suitable for heavy, viscous fluids.
What are the disadvantages of a hydraulic pump
✓Potential fire hazards if oil is used as a power fluid.
✓Limited in producing fluids with high solids content, and high GOR.
describe how a electric submersible pump works
An electric submersible pumping (ESP) system
includes a downhole centrifugal pump driven by
a submersible electric motor, which is connected
to a power source at the surface.
What are the advantages of ESP
✓Ability to handle high rate: 100 to 60,000 B/D, including high water-cut fluids.
✓High-temperature tolerance (above 350°F) using high-temperature motors and
cables.
✓If placed in straight or vertical sections of the well, ESPs can be used in high-angle
and horizontal wells.
✓Ability to lift corrosive fluids and sand by modification.
✓The most efficient lift method on a cost-per-barrel basis.
✓Low maintenance.
✓Minimal surface facilities requirement
What are the disadvantages of the ESP
✓Limitations in well with high GOR. In wells producing high GOR fluids, a downhole
gas separator must be installed.
✓Limited production ranges determined by the number and type of pump stages;
changing production rates requires either a pump change or installation of a variable
speed surface drive.
✓The tubing must be pulled for pump repairs or replacement.
✓Poor ability to pump sand
Describe how a gas lift works
Gas lift involves injecting high-pressure gas from the surface into the producing fluid
column through one or more subsurface valves set at predetermined depths (determined by
gas lift valves design procedures).
What are the two types of gas lifts
Continuous gas lift
Intermittent gas lift
What are the advantages of the gas lift
✓Gas lift can be used in deviated or crooked wellbores,
✓Suitable for high-temperature environments and high-GOR wells.
✓Economically viable for modification (replacing with a new design) in case wireline
retrievable gas lift valves are used.
What are the disadvantages of the gas lift
✓The availability of gas and the costs for compression and injection.
✓Lift efficiency can be reduced by corrosion and paraffin.
✓Not suitable for fully depleting low-pressure, low-productivity wells.
✓Causing downhole pressure surges during intermittent gas which may lead to
excessive sand production.
What are the factors affecting the artificial lift selection concerning reservoir characteristics
1.IPR
2.Liquid production rate
3.Water cut
4.Gas-liquid ratio, viscosity
5.Oil formation volume factor
6.reservoir drive mechanism
What are the factors affecting the artificial lift selection concerning wellbore characteristics
1.Well depth
2.Completion type
3.Casing and tubing sizes
4.Wellbore deviation
What are the factors affecting the artificial lift lift selection concerning surface conditions
1.Flow rates
2.Fluid contaminants
3.Power sources
4.Field location
What are the factors affecting the artificial lift selection concerning field operation characteristics
- Long-range recovery plans
- Pressure maintenance operations
- Enhanced oil recovery projects
- Field automation
- Availability of crew and support services
What is IOR
Improved oil recovery
What is the definition of IOR
defined as any
process, or combination of processes, that may
be applied to economically increase the oil
production
Does IOR include natural drive mechanisms of the reservoir
nope
What are types of IOR
waterflooding, artificial lift,
gas injection, horizontal drilling, multilateral
drilling, hydraulic fracturing, and enhanced oil
recovery (EOR).
As the production increases the differential pressure ________
decreases
Are artificial lifts considered primary recovery?
Yes
During primary recovery, how much OOIP is produced
around 10%
OOIP = original oil in place
What type of methods is used during secondary recovery
injecting water to the production zone or gas into the gas cap
After implementing primary and secondary how much percent of OOIP is recovered
15% - 40%
Which methods are used during tertiary recovery?
thermal, chemical, and gas injection, and EOR
What are the three major types of EOR methods
chemical EOR, thermal EOR, and Miscible displacement
After implementing EOR how much percent of OOIP can be recovered
30% tp 60%
Describe how EOR gas injection/miscible flooding works
miscible gases
will be injected into the reservoir. This will
improve the pressure maintenance and also the
oil displacement (by reducing the interfacial
tension between oil and water)
Which is the most common type of EOR method
Gas injection/ miscible flooding
What gases are used for gas injection and which of them is most commonly used
CO2, hydrocarbons (such as propane or
methane), and nitrogen. However, the most
common one is CO2 as it is the cheapest one
while it has good viscosity reduction
capabilities.
Describe how chemical flooding works
use chemical solutions such as micellar, alkaline, or soap-like
substances to reduce the oil/water surface tension. Polymers such as
polyacrylamide or polysaccharide may also be used to increase the sweep
efficiency.
What is sweep efficiency
is a measure of the effectiveness of an EOR method that
depends on the volume of the reservoir contacted by the injected fluid.
What are the four sequences for a chemical flooding injection process
(1) Preflush (low-salinity water), (2) Chemical solution
(micellar or alkaline), (3) Mobility buffer (water thickened with polymer) (4)
Driving fluid (water), which displaces the chemicals and the resulting oil bank
toward production wells.
Fill in the blanks:
Non-thermal methods aim to ________ the viscosity of oil
(miscible and immiscible gas injection), ________ the viscosity
of the displacing fluid (polymer flooding), or _________ the
interfacial tension (chemical flooding).
reduce
increase
reduce
Fill in the blanks:
Non-thermal recovery techniques most suitable for: (1)
Viscosity of crude: ___-___ cP, (2) Formation thickness: less
than ___ ft, (3) Formation depth: greater than _____ ft, (4)
Permeability: less than ___ md,
50-200
30
3000
1
Are thermal methods most commonly used for light or heavy oils?
Heavy crude oils
What are types of thermal methods
➢In-situ
combustion
flooding)
➢Cyclic steam stimulation
➢Steam flooding
➢Hot waterflooding
➢Electro-thermal heating
➢Hybrid processes
What factors have drawn companies to heavy oil production
Improved profitability, technological advances, huge reserve
size, low geological risk and low capital investment
Fill in the blanks:
90% of global heavy oil reserves are in ________ and
_________, and the heavy oil and bitumen reserves are
estimated to be _____ times more than conventional crude oil
reserves.
Canada and Venezuela
five
In the world there is an estimated ______ trillion barrels of conventional crude oil
1.02
In the world there is an estimated ______ trillion barrels of heavy oil and Bitumen
5.6
Which of the following is most commonly used
Thermal, chemical, HC gas, CO2
Thermal
What is the average porosity for heavy oil reserves
high porosity of 30%
What is the average oil saturation for heavy oil reserves
50-80%
What is the average formation thickness for heavy oil reserves
50ft to several hundred feet
What is the average depth for heavy oil reserves
shallow depth less than 3000ft
What is the average permeability for heavy oil reserves
High permeability of 1 to several darcies
What are the two main mechanisms in steam flooding
- Decreasing the viscosity of heavy oil by applying heat
- Physical displacement similar to waterflooding
Which EOR method is the least expensive
Hot-water flooding
Which method has a better performance dealing with clay swelling problems. efficient in maintaining reservoir pressures and provides higher injection compared to steam
Hot-water flooding
what is in-situ combustion
fire flooding
in-situ combustion aims to recover more from shallow or deep crudes? and less or more viscous crudes?
deep reservoirs
more viscous
Does in-situ combustion burn the crude oil?
yes, about 10% of the least desirable portion of the oil
Fill in the blanks:
In-situ combustion _______ the viscosity, partially _________ the oil in place, and
drives it forward by a combination of steam, hot water, and ______
drive. The burning front which is called combustion zone would
move in the formation and displace the remaining fluid in place
into the _________ wells.
reduces
vaporizes
gas
producing
What does CSS stand for
cyclic steam stimulation
Describe CSS
Steam is injected at 300 to 400 ºC into a well at a high rate and high pressure for a certain amount of time
Huff and Puff
How much percent does the CSS process recover OOIP
20%
What are the 3 steps of huff and puff / CSS
steam injection
soaking period
oil production
What does SAGD stand for
Steam Assisted Gravity Drainage
Describe how SAGD works
employing a pair of
horizontal wells and conducting steam stimulation. The horizontal well are drilled 4 to 6 meters above each other and
the steam is injected from the above well and the heated heavy oil
is drained and produced from the lower well. The steam is injected through the horizontal injection and the
steam chamber expands upwards from the injection well. The
heated oil drains down the steam chamber via gravity.
What does VAPEX stand for
vapour assisted petroleum extraction process
How does VAPEX work
the solvent analog of the steam-assisted
gravity drainage process (SAGD), which reduces oil viscosity
by diluting the in-situ heavy oil or bitumen with the help of
injected vapourized solvents.
