the basic idea and knowledge a person should have while starting a course of petroleum engineering

1. Basics of Peroleum Engineering

2. Permeability is a property of a porous medium that characterizes the ease with which
fluids flow though it.
PERMEABILITY
• Intrinsic property of the medium
• Along with the porosity, it tells how fit the
formation is to be classified as a potential
reservoir
• S.I. Unit: m2 (square metre)
• Common unit: darcy ( or milli darcy)
• By knowing the conductivity, permeability
can be calculated by the Darcy’s law.
Factors affecting permeability:
• Porosity
• Stacking of the individual grains (packing)
• Sorting
• Sphericity and roundness (particle properties)
• Diagenesis
• Tortuosity

3. PERMEABILITY
Measurement of permeability:
• Laboratory method: passage of fluid through a cylindrical core. Another
method uses gas flow under pressure (but this has to be corrected by the
Klinckenberg correction)
• Direct or field method: measurement takes place by down hole logging.
Most commonly used log for this is the Nuclear Magnetic Resonance (NMR)
log.
Different types of permeability:
• Absolute or intrinsic or specific permeability
• Effective or phase permeability
• Relative permeability
NOTE: It is the simplest measure of the producibility of subsurface formations.

4. GEOPHYSICS
• Geophysics refers to the study of the Earth’s subsurface on the basis of different
physical properties.
• It covers the fields form the passage of elastic waves within the Earth as well as its
electrical, magnetic and gravity fields.
• Used by exploration personnel to make predictions about the presence and nature
of subsurface hydrocarbon accumulations.
• Problem in geophysics: the inverse problem (the non unique nature of the
solution for a set of measurements)
SEISMIC SURVEY: It employs a source to generate vibrations that propagate into the
subsurface. These waves are reflected by the subsurface terrane. These are picked
up by geophones. By structural imaging,
subsurface layers are identified. The places
along which the velocity changes are
interpreted to be interfaces between different
rock layers.
Additional information (characteristics of
rock layers) can also be obtained.

5. GEOPHYSICS
• Records spatial variation in Earth’s gravitational field.
• This happens because of difference in density of rocks
in the subsurface.
• Corrections have to be applied. (Eg. Bouger Correction)
• Most common oilfield application is to delineate salt
domes (salt domes give a big gravity anomaly due to
their lesser density.)
ELECTRO MAGNETIC SURVEY:
• It works on the basis of the resistivity of the subsurface formations.
• For eg. Rocks saturated with hydrocarbons have higher resistivity and can be detected by EM
surveys.
• Two methods are used for acquiring information:
 Controlled source EM (CSEM): used in marine settings
 Magnetotellurics: uses fluctuations in the Earth’s magnetic field induce by solar wind. ( a
natural EM source.)
MAGNETIC SURVEY:
• It relies on the permanent magnetic properties of rocks. Sedimentary rocks generally have a small
magnetic susceptibility as compared to igneous or metamorphic rocks. Hence, oil bearing
sedimentary rocks can be identified.
• Measures subtle anomalies in magnetic field
• Covers a large area; used mainly for mineral exploration
GRAVITY SURVEY:

7. Oil and Gas Exploration Essentials
Oil and gas exploration is the search by petroleum geologists and geophysicists for
hydrocarbon deposits beneath the Earth's surface.
Elements and processes that are essential for the existence of petroleum
accumulation:-
•Trap:- A barrier to the upward movement of oil and gas
• Reservoir:- Porous and permeable to receive the hydrocarbons
• Source rock:- A rock formation containing organic matter
•Seal:- An impermeable cap to keep fluid in the reservoirs

8. Oil and Gas Exploration Essentials
• Different personnel perform the task of exploration collectively.
Geologists, geophysicists, etc. are all involved here.
• Different surface and sub surface techniques are utilized for
exploration.

9. DRILLING
Spudding In:-
•The commencement of drilling is termed
Spudding in
Drilling Ahead:-
•Drilling ahead means the actual drilling of the
well. Specific drilling processes vary, but many
of the work hazards are similar.
Tripping the bit:-
•Tripping the bit is the physical act of pulling
the drill string out of the wellbore and then
running it back in.
• The mud is circulating to bring cutting and
gases up to the surface k/a circulating bottoms
up.

10. Casing Point
• The casing point is the point in a drilling
project when well drilling operations cease
and the well owners must decide whether
the well should be completed or plugged &
abandoned.
• Casing point may also refer to the depth to
which casing is set in a well.
Leak Off Test
• Leak Off Test is conducted in order to find
the fracture gradient of certain formation at
casing shoe depth.
• The results of the leak off test dictate the
maximum pressure or mud weight that may
be applied to the well during drilling
operations.

11. Drilling Fluid –
Definition
 Suspension or emulsion?
 Emulsion: a mixture of two or more liquids that are normally immiscible
(unmixable or unblendable).
 Suspension: a heterogeneous mixture in which the solute particles do not
dissolve but get suspended throughout the bulk of the medium.

12. Drilling Fluids Types
Drilling Fluid
Water Base Mud
(WBM)
Non-Inhibitive Type
Native Mud Bentonite Mud
Inhibitive Type
Calcium Treated
Mud
Salt Water Mud
Potassium Base
Mud
KCl-PHPA Polymer
Mud
Oil Base Mud
(OBM)

13. Function of Drilling Fluids
 Remove cuttings from the well.
 Control formation pressures by providing
hydrostatic head.
 Suspend and release cuttings.
 Seal permeable formations.
 Maintain wellbore stability.
 Minimize reservoir damage.
 Cool, lubricate, and support the bit and drilling
assembly.
 Transmit hydraulic energy to tools and bit.
 Control corrosion.
 Facilitate cementing and completion.
 Minimize impact on the environment.
Drilling Fluids
Properties
 Density
 Viscosity
 Apparent Viscosity
 Gel Strength
 PV
 YP
 Solid Content
 pH
 Fluid Loss
 Chloride Content

14. Circulating Components
Circulating component consist of the following:
1. Mud Pump
2. Pump Manifold
3. Standpipe
4. Swivel
5. Drillstring
6. Annulus
7. Return Line
8. Shale Shaker
9. Desander
10. Desilter
11. Degasser
12. Mud Pit

15. •Rig Monitors
•Flame Ionization
Detector
•Fluoroscope
•Chromatograph
•Microscope
•Mud log computers
•Vacuum Oven
•Gas analyzer
•Porosity Meter
•X-ray Diffractometer
•Centrifuge

18. Perforation
• A method of establishing effective communication between the
wellbore and the formation
• Involves blasting channels for the fluid to flow – detonators serve the
purpose
Types : Shaped-charge Detonation & Electrical Detonation
• Both of the methods make evident use of explosives – when SCD uses
only secondary explosives, ED uses primary explosives as well.
• Detonators are mounted on a perforating gun.

19. • Types of perforating guns:
• Perforating Parameters: Shots per foot and phasing
• Methods of Perforation:
• Selection: The selection of method and type of the
gun depends on wellbore geology and other
characteristics.
For example, the reservoirs with high horizontal permeability require deeper holes whereas the wells producing more sand are
compatible with large diameter holes and independent of depth of the holes.
Through Tubing Guns Hollow carrier / Casing Guns
1.) Run through the tubing 1.) Tubing is pulled out and gun is run through
casing
2.) Uses small sized charges 2.) Houses larger charges
3.) smaller in diameter 3.) comparatively larger diameter
Tubing Conveyed Perforation Wireline Perforation
1.) Gun attached to the tubing end and then
lowered
1.) Gun is lowered with the help of cable
2.) Drilling/Work-over Rigs are required to
lower the gun
2.) Rig is not required
3.) Benefit : leaves the tubing in place after
the perforation
3.) Benefit: Accurate depth correlation with
CCL
4.) Limitations : Entire tubing has to be pulled
out to retrieve the gun
4.) Limitations : Gun Length and Weight

20. Reservoir Enginnering
• Domain which deals with the evaluation and management.
• It employs the combination of various engineering and scientific
methods to predict the properties of the reservoir.
• Various aspects include:
1.) Reserve estimation
a.) Volumetric method
b.) Material Balance Methods
c.) Decline curve method (semi-logarithemic plot of well prod. Rate v/s time. Type of
curves : exponential, hyperbolic & harmonic curves)
d.) Comparative Methods

22. b.) Reservoir Drive Mechanism Analysis & Drive Indices calculation
c.) Reservoir Modelling
d.) Reservoir Monitoring
e.) Reservoir Characterization – Dry, Retrograde, Wet, Volatile, Heavy oil,
black oil
Reservoir Engineering deals with various factors such a porosity,
permeability, viscosity, compressibility, formation volume factor, PVT
analysis to carry out various above given operations.

23. What is Cementing ?
•Cementing is the process by which cement slurry is placed in the annulus, bonding the
casing to the formation.
•• The conventional method of doing this is to pump cement down the casing and displace it
around the casing shoe into the annulus.
• A good cement job is essential to allow further drilling and production operations to
proceed.
In some cases this can be done in a single operation by pumping cement down the casing,
displacing it around the casing shoe and up into the annulus
• For conductor and surface casing the whole annulus is cemented back to surface
• In longer casing strings (e.g., production casing) the cement job may be carried out in two
stages:
− the first stage is completed in the conventional manner as described above, with
the exception that the cement slurry does not fill the entire annulus, but reaches only a
predetermined height above the shoe
− the second stage involves opening a special tool in the casing string which allows
cement to be displaced from the casing directly into the annulus. This is known as ‘stage
cementing’.

24. •

25. Well Completions
• Completion is a technique where
equipment's are selected & installed in
a well to get optimal production safely
for entire foreseeable producing life of
a oil or gas well.
• The decision to case and cement the
well for production or plug it for
abandonment can be done only after
Formation evaluation using open hole
logs.
• Completion design is a function of
numerous reservoir characteristics,
such as
- Permeability
- Porosity
- Saturation Pressure
- Stability, and
- Compartmentalization

26. Well completions
Types of completions
• Open hole completion: production casing is set on top of the pay zone.
• Cased Perforated completion: producing interval is covered by the production
casing.
• Liner completion: production casing is set on top of the pay zone and is followed
by a liner.
Factors Influencing Well Completion Selection :
• Natural occurrences of the field, i.e. does it have a big reserve to justify
development?
• Potential of oil production and the planning of tertiary recovery, i.e. do we need
any artificial lift in the future?
• Limitations within the operation and the field, i.e. is the oil field located at a
remote area?

27. Reservoir Drive Mechanism
•Affected by natural causes—temperature and overburden pressure
•Gravity play role in segregation
•Drilling causes pressure disequilibrium->maintain by fluid flowing into the well-
>fluid movement depends on
•Fluid do not move uniformly due to
rock and fluid heterogeneity
•Primary natural drive systems
1.Water drive (recovery factor 35% to 75% of OOIP)
•Comes from connected aquifers
•HC extracted ->water drives in a) bottomwater drive(coning) and
b) edgewater drive
•Waterflood->injection of water for production
1. Water drive
2. Solution-gas drive
3. Gas cap drive
4. Gravity drive

28. 2. Gas cap drives (recovery factor 20% to 40% of OOIP)
•Due to expansion of gas at top of reservoir-> bubble point
•Oil leg->completion of well to avoid producing gas
•GOC moves downward->pressure dropped->produced gas injected back.
3. Solution gas drive (recovery factor 5% to 30% of OOIP)
•Saturated reservoir ->initial pressure above bubble point
•Oil produced->reservoir pressure dropped->expanding gas-> support reservoir
and help flow of oil.
•If bubble point reached-> decline in oil production->system falls-> liberated
gas may migrate
4. Gravity drive (recovery factor 5% to 85% of OOIP)
•Gas cap+water drive
•Energy from two direction
a)Towards upward -- hydraulic pressure in oil columns
b)Towards downward – expanding gas column

29. RHEOLOGY
•Study of how material flow as a function of
1. shear or load rate
2. Time
3. Spatial orientation
Affected by MANY factors
1. Temperature 5. Drilling fluid
2. Pressure 6. Cement
3. Rate and duration of shear 7. workover fluid
4. Production fluid 8. completion fluid
• Affect negatively
1. heavy oil production high viscosity diff. to produce
2. Deepwater cooler environment create flow problem
• Viscosity, shear stress (shear rate)

30. Rheology models
Types of fluid flow
1. Newtonian
viscosity dir. por. to shear stress
2. Non-Newtonian
a. Bingham plastic
not flow until yield point
b. Power law
shear stress const. exponential
good fit at low shear stress  no yield point ,no gel strength
c. Hershcel Bulkey models
addition of above two.
• Non –Newtonian fluid is useful
Thixotropic Fluids  ongoing increase in gel strength depend on rest time
• Used in wells in which fractures and lost circulation are concern

31. Well logging

32. Type of well logging

33. Gamma ray

34. Spontaneous potential (SP)

35. Density & Neutron Porosity

36. Electrical log

37. Log Interpretation

38. DEFINING POROSITY
• Porosity – is volumetric void
spaces present in a rock, 2 types
• Permeability – is the ability to
allow fluids to pass through it
• First formation resistivity is
calculated which helps to identify
the HC bearing rock
• NOTE
• Resistivity high HC bearing
rock
• Resistivity low Water
bearing rock

39. • Sonic porosity - Calculated by using speed of sound
• Density porosity - Emits medium range of gamma rays
- Gamma ray hits the e- in formation
- e- density is directly proportional RHOB
- density porosity is calculated by
• Neutron porosity - High energy(10^6 eV) fast neutron
bombardment
- Energy loss takes place while collision
with formation nuclei and reaches to thermal
energy state
- Energy loss is correlated with relative
mass of the nuclei
POROSITY MEASUREMENT

40. • Thermal Energy state- At this state only few thermal neutrons come
back to detector and rest of them captures.
• Then the counts at detector is calculated which is used to measure
Hydrogen index
• Finally we calculate neutron porosity using HI
Generally
• Reservoir rock – having hydrogen associated with Liq. (Oil/Water) in
pore spaces
• Gas – generally gas has low Hydrogen density than oil/water
• High H-atoms means less counts at detector
• Low H-atoms means high counts at detector

41.  CROSS-OVER
Tells about the fluid type and lithology
• Cross plot porosity or Total porosity - is calculated using neutron
and density porosity

42. • Porosity can also be calculated by NMR tools (calculates directly the
liquid filled porosity) and core sampling (provide empirical porosity
which can be different from actual porosity)
• Porosity tells the HC potential so that best recovery of HC can be
achieved

43. Well Testing Fundamentals
• Done while flowing fluid from the reservoir
• This test is to determine whether a formation will produce HC @ rate
of reasonable return with further investments
• During testing : Formation Pressure, K, Skin (damage to the
formation during drilling or other well operation) is calculated
• Production potential test can be performed through different
methods
• A) Production well test
• B) Drill Stem Test
• C) Wireline Formation tester

44. A. Production well test
• In this well is flowed through a test separator.
• Deflector plate - slow down the flow vel.
• Coalescing plate - gather oil into large droplet
• Separator sector
• And as the pressure reaches bubble point pressure or below that, gas
start evolving from oil
• Mist extractor
• And using pneumatic valves gas and fluid exit is controlled and flow rate
is measured using orifice plate meter

45. B. Drill Stem Test
• During production
• Formation fluid is flowed through drill string to the surface @ different
rates through choke valves (controls flow rates)
• Pressure variation curve is plotted vs. time
Pressure Test Types
1. Buildup -Pressure rise is recorded @
bottom hole in shut-in condition
2. Drawdown – well is opened and BHP
start decreasing
3. Falloff/Injection – fluid is injected into
formation , BHP increases
4. Interference – as the well shut-in the
BHP start decreasing is monitored &
recorded. And the time gap gives an
indication of reservoir size & flow
communication

46. • For measuring this time change a technique called Transient analysis
technique is used. It uses a mathematical correlation of formation
pressure, flow rate and time. It leads to conclude
i. HC potential, skin
ii. K, reservoir boundary shape and distance from the wellbore
iii. Initial & Avg. reservoir pressure
• Collectively these pressure tests are called drill stem test
• Isochronal Test - Series of drawdown & buildups
- pumping rate vary for each drawdown , while buildup
continue until the well reaches its original shut in
period
• Modified Isochronal test – Both drawdown & build up periods are of
equal duration
• These tests also give the information of Production potential, K, skin
and AOF(absolute open flow)

47. C. Wireline Formation Tester( WFT)
• Captures fluid sample and measure press.
Downhole at the zone of interest
• Quartz pressure gauge – measure pressure
• Probe – use to suck formation fluid
• Packer assembly – supports the probe
• Sample chamber – use to collect and analysis
• Pump – controls the backpressure and using
control valves diverts the contaminated fluid
into wellbore and uncontaminated to sample
chamber
• DFA (Downhole Fluid Analysis) – To measure
GOR and to monitor sampling process
• Optical Spectroscopy – It identifies the fluid composition
• Well test data has application to correct the reservoir models, which allows
operators to make better long term decisions about their assets

48. Downhole Coring
• Coring is process of obtaining an actual sample of a rock formation from the
borehole and provide essential data for the exploration ,evaluation and
production of oil and gas reservoirs.
• Core provide ground truth of calibration of well logs.
• Production can be optimized based on the analysis of core porosity
,permeability, fluid saturation ,grain density , lithology and texture.
• Core samples can be undertaken in two ways:
• 1.Conventional Coring: It is performed when Zone is being drilled.It is
similar to Conventional drilling and chiefly differe in types of bit used.
• First well is drilled using conventional drill bit and drill string and a
wellsite geologist closely monitors drilling progress to decide when to begin
coring operations.The time of this decision is critical. Correlations with offset
well logs usually provide the first indication that the drill bit is nearing the
coring point. Once the geologist gives the order to begin coring, the driller pulls
the drill bit out of the hole, and the drilling crew exchanges the drilling BHA for
a coring bit and core barrel.
•

49. 2.Sidewall coring :Sidewall cores (SWCs), plugs of rock taken from
the wellbore wall, may offer a cost-effective alternative to
conventional cores.
After the driller reaches a casing point or drills to total depth
(TD), the drillpipe is pulled out of the hole and the well is logged
before casing is set. Sidewall cores typically are obtained after
logs have been run, usually near the conclusion of an openhole
wireline logging job.
Two types of wireline sidewall coring devices—percussion and
rotary—are available. A percussion coring tool, or core gun, has
bullet-shaped core barrels mounted on a carrier (below). The
core gun uses small explosive charges to propel individual core
barrels into the side of the wellbore to capture samples of the
formation. In contrast, a rotary coring tool uses a small,
horizontally oriented coring bit to cut plugs from the side of the
borehole (below).