This presentation is all about Petroleum Engineering, Prospecting oil and gas, drilling and various drilling methods, logs and its types, different Drive Mechanisms, etc......

1. IN THE NAME OF ALLAH, THE MOST GRACIOUS, THE
MOST MERCIFUL

3. BY
Arshad Ayub
To
Sir Waqar Ahmad
PETROLEUM ENGINEERING

4. Focus of My Presentation
1) Prospecting and exploration of oil and gas
2) Basic concepts of geophysical and geochemical exploration
methods
3) Drilling and well logging
4) Reservoir characteristics
5) Drive mechanism
6) Energy and pressure maintenance
7) Secondary and enhanced recovery

5. What is Petroleum Engineering?
 Petroleum Engineering is the
field of engineering that deals
with the exploration, extraction
and production of oil.
 It also deals with the production
of Natural Gas production.
 It is a field of engineering
concerned with the activities
related to the production of
hydrocarbons, which can either
be Crude Oil or Natural Gas.

6. What are Oil and Gas?
 Oil and Gas are substances found
within the earth crust.
 They are thought to come from
decomposed plants and animals
matter.
 Scientists believe that the plants and
animals died long ago, and were
slowly buried by thick layers of
sediments.
 Over long period of time and with
pressure and temperature the organic
materials were converted to oil and
gas which we found today.

7. Prospecting Oil and Gas
 Finding petroleum reservoirs requires very precise location and definition of
subsurface rock masses.
 Surface Geological Prospecting
 Observation of rocks by trained geologist (where subsurface layers reach
the surface), can identify lithology and asses the potential for hydrocarbon
source rock, reservoir quality and trapping mechanism in an area under
study.
 Then Geological map is made from this observation, to show the position of
the geologic features and provide description of the physical characteristics
and fossils content of strata.
 Many oil and gas reservoirs are 1000’s of feet beneath the surface.

8. What is Geophysical Exploration?
 Sub-Surface Geological Prospecting
 The application of the principles of physics to study the
subsurface in search of hydrocarbons.
 Geophysical investigation of the subsurface involves taking
measurement at or near the earth`s surface that are influenced
by the internal distribution of physical properties.
 Its objective is to find new hydrocarbon resources at low cast
and in short period of time.

9. Geophysical Methods
 Petroleum exploration and production are concerned with the
geological interpretation of geophysical data.
 Three types of geophysical methods are used:
1) Magnetic Method
2) Gravity Method
3) Seismic Method
 Magnetic and Gravity methods are used only in predrilling
phase.
 Seismic method is used both in exploration and development
phases.

10. Gravity and Magnetic Method
 Gravity and Magnetic method are also known as “potential
fields”.
 They are used to give an indirect way to see beneath the earth
surface by sensing physical properties of rocks (density and
magnetization).
 These methods can help locate minerals, faults and petroleum
resources.

11. Gravity Method
 Measured Parameters
 Gravity method measures spatial variation in the earth`s
gravitational field.
 Operative Physical Property
 Gravity method uses density of the rocks.
 Change in gravitational field is due to the difference in density
of the subsurface rocks.
 Gravity method is based on two laws: Universal Law of
Gravitation and Second Law of Motion.

12. Magnetic Method
 Magnetic methods have been used since 1920.
 Magnetic methods play a big role in locating oil and gas fields.
 Measured Parameters
 Magnetic method measures the spatial variation in the strength
of the geomagnetic field.
 Operative Physical Property
 Magnetic method uses magnetic susceptibility and
reminiscence of the rocks.

13. Seismic Method
 Seismic surveying is the most important of the three.
 Principle: Generating seismic pulse at or near the earth
surface and record the amplitude and travel times of reflected
or refracted waves.
 Seismic survey is mostly concerned with the primary waves.
 It is the best and most definitive Geophysical method.
 Seismic data can provide very nearly direct indications of oil
and gas.
 It will give more information of the subsurface.

14. Types of Seismic Exploration
 Depending on the angle of incidence, some of the rays are refracted
and some reflected.
 So there are two types of seismic survey:
i. Seismic Reflection
ii. Seismic Refraction
 But seismic survey is more concerned with reflected ray path than
refracted one.
 Reflection Coefficient: Ratio of amplitudes of reflected and
incident waves.
 It is positive if velocity and density increases and negative if velocity
and density decreases.
 Velocity and density increases with increase in depth.

15. Steps in Seismic Exploration
 Seismic exploration involves three steps:
1) Data Acquisition: Data is recorded on the geophones, which
is transmitted to the recording trucks.
2) Data Processing: The recorded data is processed into a
format suitable for geological interpretation. Seismic data
processing include mathematicians, physicists, electronic
engineers and computer programmers.
3) Interpretation:

16. Geochemical Exploration
 Geochemical methods are a group of ways of prospecting and
exploring for petroleum and natural gas formations.
 One of these is Chemical analysis of gases, water, rock and
soil.
 Purpose
a) Presence of dispersed petroleum in the subsurface.
b) Traces of the influence of petroleum substances on gases,
water, rocks, soils and organisms.
c) Substances or conditions which customarily accompany oil
and gas pools.

17. Geochemical Methods
 They may be direct or indirect methods of prospecting for
petroleum.
 Structural hydro chemical surveys (to show the subsurface geologic
structures) are example of indirect methods.
 It is important in areas with buried structures and Geologically
Closed regions where tectonics of surface is different from tectonics
of deep oil formations.
 Geochemical method of prospecting petroleum should be used in
close association with other methods.
 Without other methods, it leads to incorrect conclusions.
 The geologists examine all the facts obtained by various methods
and makes the final decision.

18. Drilling
 Drilling is a cutting process that
uses a drill bit to cut a hole of
circular cross-section in solid
materials.
 Drilling rigs are used for drilling
wells.
 Wells are drilled to explore
petroleum.
 There are two types of drill:
1. Drills which produce rock chips
2. Drills which produce core
samples (cylindrical section of a
rock body)

19. Drilling Rigs
 There are several types of offshore drilling rigs, designed to
work in variety of locations.
 Jackups are moveable drilling structures with bottom supports.
They have columnar legs.
 Platforms are not moveable like Jackups. They are
immoveable. They are made of steel or cement.
 Semisubmersible drilling units stay afloat offshore on giant
pontoons. When filled with water the pontoon partially
submerge the unit to a desirable depth. Most reliable in rough
seas.

20. Drilling Rigs

21. Types of Drilling
 Conventional Drilling
 They are drilled vertically from the
surface straight down to the zone.
 This is a traditional method and still
common type of drilling.
 Horizontal drilling
 Using technologies such as bottom
driven bits, drillers are able to
execute a sharp turn and drill
horizontally along a thin pay zone.

22. Types of Drilling
 Slant Drilling
 Drilling at an angle from
perpendicular (commonly 300 to
450).
 This method is used to minimize
surface environmental
disturbance.
 Directional Drilling
 Drilling has advanced from
horizontal and slant drilling to
drilling that can change direction
and depth several times in one
well bore.

23. Well Logging
 It is the process of recording various physical, chemical,
electrical or other properties of the rock or fluid mixtures
penetrated by drilling a borehole into the earth`s crust.
 Well log is a record kept during the drilling of a well, especially
of the geological formations penetrated.
 It is one of the oldest and most used methods that depends on
the geophysical properties of rocks in the subsurface.
 These methods are good when the surface outcrops are not
available.

24. Well Logging
 Seismic data can be used to determine
the subsurface structure but a direct
sample of the rock in necessary to know
the lithology.
 The most practical way is to drill a well
and record all the useful information
possible from core.
 Modern drilling uses lubricating mud
that is pumped down to the drill pipe to
cool and lubricate the drill area.
 Lubricating Mud is a mixture of
bentonitic clay and oil or water, plus
Barite to regulate density.

25. Types of Well Logging
 Logs can be classified into several types under different categories.
 Radioactivity Logs
i. Gamma Ray log
ii. Caliper log
iii. Neutron log
iv. Density log
v. Lithodensity Log
 Electrical Log
i. Resistivity log
ii. Self Potential (SP) log
 Sonic or Acoustic log
 Nuclear Magnetic Resonance Logging
 Dielectric Logging

26. Gamma Ray Log
 It is also known as shale log.
 Measures the radioactivity of the formation and evaluation of
radioactive minerals, such as potassium and uranium deposits in
clay rocks like shale.
 The radioactivity is measured in API (American Petroleum Institute)
units.
 Deflection of baseline to the left show change of lithology from shale
to clean lithology.
 Gamma rays can penetrates steel, so the log can be run in cased
holes.
 Unaffected by fluids.
 Gamma reading is affected by hole diameter, so run together with

27. Caliper Log
 Caliper tools measure hole size and
shape.
 The mechanical caliper measure variation
in bore hole diameter with depth.
 It is very useful in relaying information
about the quality of the hole and reliability
of other logs.
 Example: Large hole where dissolution or
falling the walls of the hole results in
errors in other log responses.
 Most caliper are used with GR logs and
typically will remains throughout.

28. Neutron Log
 Principle: Bombarding the
formation with neutrons and
determining how many become
captured by the hydrogen nuclei.
 Neutron logs measure the amount
of hydrogen present in water atoms
of a rock.
 It can be used to measure porosity.
 Because shale have high amount of
water, the neutron log will read quite
high porosities.
 It must be used with GR logs.

29. Density Log
 Principle: It measures the electron density of a formation.
 Uses radioactive source to generate gamma rays.
 Gamma ray collides with electron in formation, losing energy.
 Detector measures intensity of back scattered gamma rays, which is related
to electron density of the formation.
 Electron density is a measure of bulk density.
 Bulk density depends upon Lithology, porosity, density and saturation of
fluids in pores.
 The higher the gamma ray reflected the greater the porosity of the rock.

30. Density Log

31. Lithodensity Log
 It is also a density log, it
measures the bulk density.
 It includes the addition of a new
parameter (i.e.) Photoelectric
cross-section (Pe).
 Pe records the absorption of low
energy gamma rays by a
formation.
 It is less dependent on porosity.

32. Resistivity Log
 Principle: Records the resistance of
interstitial fluids to the flow of an electric
current.
 Current is either transmitted directly
through electrodes or magnetically
induced.
 It is measured in ohm-meter.
 Porous formation with salt water have very
low resistivity.
 Formations that contain oil/gas generally
have much resistivities.
 One must be careful of very high values,
as it often represents zones of either
anhydrates or non-porous intervals.

33. Self Potential (SP) Log
 Principle: Measuring the difference
in electrical potential between two
electrodes in milli-volts.
 If the fluid is better conductor (salt
water) than the drilling mud, the
curve will deflect to the left.
 If the fluid is poor conductor (fresh
water or oil) than it will deflect to
right.
 It is similar in shape to GR log (but
can not identify thin beds), and both
can be used alternatively for
correlation purposes.

34. Sonic Log
 Principle: It measures travel
time of an elastic wave through
formation.
 Formation having greater pore
space will result in greater travel
time and vice versa for non
porous section.
 Measures the porosity of the rock.
 Must be used with other logs like
gamma rays etc. for better
understanding.
 Detecting fractures and evaluating
secondary porosity.

35. Nuclear Magnetic Resonance Log
 Extremely effective in measuring
porosity and permeability.
 It has the advantage of direct
measuring the hydrogen of fluids
in pore space.
 It avoids lithology effect on
porosity determination.
 When carefully calibrated, it can
be used to identify gas reservoir.

36. Dielectric Log
 A log of high frequency dielectric properties of a formation.
 Dielectric constant is a factor that controls dielectric
propagation through a medium.
 It includes two curves:
I. Relative Dielectric Permittivity
II. Resistivity
 RDP can be used to distinguish hydrocarbons from water.
 Advantage: Low frequency log permits large depth
investigation.

37. Reservoir Characteristics
 Porosity and Permeability are not quite sufficient for a rock to be a
Reservoir.
 Reservoir behavior relative to oil and gas accumulation and
production involves porosity and permeability but it is based upon
several important engineering factors.
 Porosity: Amount of void spaces in a rock measured as a
percentage of the rock volume.
 Effective Porosity: connected porosity where void space has flow
through potential is called effective porosity.
 Non-effective porosity: Where void spaces are isolated.
 They both form the total porosity (all the void spaces).

38. Types of Porosity
 Primary porosity
 Pore space in rock at the time of
deposition is primary or original
porosity.
 It is reduced by compaction and
related diagenetic processes.
 Secondary Porosity
 Ground water solution,
recrystallization and fracturing cause
secondary porosity.
 Example Cavern formation in
Limestone.

39. Permeability
 Property of a rock containing connected porosity and allow the
passage of fluids through it.
 Some rocks are more permeable than others because of their
intergranular porosity or fracture porosity.
 It is measured in Darcie.
 Relative Permeability: It is a concept used to convey the
reduction in flow capability due to the presence of multiple
mobile fluid.
 Absolute Permeability: Ability to transmit a single fluid through a
rock.

40. Reservoir Drives
 Recovery of hydrocarbon from oil
reservoir is commonly recognized to
occur in several recovery stages.
They are:
 Primary Recovery
 Secondary Recovery
 Tertiary Recovery (Enhanced Oil
Recovery)
 Infill Recovery
 Primary Recovery: Recovery of
hydrocarbons from the reservoir using
the natural energy of the reservoir as
a drive.

41. Reservoir Drives
 Secondary Recovery: Recovery driven by the injection
of water or gas from the surface.
 Tertiary Recovery (EOR): A range of techniques that are
applied to reservoirs in order to improve production.
 Infill Recovery: It is carried out when recovery from the
previous three phases have been completed.
 It involves drilling cheap production holes between
existing boreholes to ensure that the whole reservoir has
been fully depleted of its oil.

42. Primary Recovery Drive Mechanisms
 Reservoir drive mechanism supplies the energy that moves the
hydrocarbon from a reservoir container to the well bore by
removing fluid near the wellbore.
 Hydrocarbons may be produced by various mechanisms.
 There are five drive mechanisms which cause oil and gas to flow
up the well bore:
 Water Drive
 Gas Drive
 Gas Solution or Dissolved Gas Drive
 Gravity Drainage
 Combination or Mixed Drive

43. Water Drive
 A reservoir drive mechanism whereby
the oil is driven through the reservoir
by an active aquifer.
 In water drive production oil or gas
trapped within a reservoir may be
viewed as being sealed within a water
filled U-tube.
 When the trap is opened, oil and gas
will flow from the reservoir because of
the hydrostatic head of water.
 All the reservoirs does not have
continuous recharge of earth surface.

44. Water Drive
 The degree of water pressure
depends upon the size and
productivity of the aquifer.
 Water invades the lower part of the
trap to displace the oil.
 With an effective water drive, the flow
rate remains constant during the life
of the fluid.
 But oil production declines inversely
with increase in water production.
 It is the most effective drive
mechanism, with a recovery factor of
up to 60%.

45. Types of Water drive
 Edge Water Drive
 Where only part of the areal
extent is contacted by water.
 Bottom Water Drive
 Where the water underlies
the entire reservoir.

46. Gas Cap Drive
 It occurs when the field contains both oil and gas zone.
 Principle
 Expansion of free gas in response to pressure drop.
 The change in fluid volume results in production.
 As production begins, the pressure drops, which causes
escape of the dissolved gas in oil.
 This gas move up to the gas cap thus expands to occupy the
space vacated by oil.

47. Gas Cap Drive
 Pressure and oil production drops
steadily, while gas to oil ratio
naturally increases.
 It is very different from the water
drive fields.
 It is less effective than water drive
mechanism.
 Its recovery factor is 20-50%..

48. Dissolved Gas Drive
 Sometimes called solution gas
drive.
 Occurs in oil fields that initially
have no gas cap.
 As production begins, pressure
drops and gas bubbles from oil
and expands, forcing oil out of the
pore towards the boreholes.
 As the gas expands it helps to
maintain reservoir pressure.
 Least efficient drive mechanism
and highly undesirable.
 Its recovery factor is 7-15%.

49. Gravity Drainage
 The density difference between oil, gas and
water result in their segregation in the
reservoir.
 This process can be used as a drive
mechanism, but is relatively week.
 It is used in combination with other drive
mechanism.
 The best conditions for this are:
i. Thick oil zone
ii. High vertical permeabilities
 Rate of production is very low but can give
rise to extremely high recoveries (50-70%).

50. Combination Or Mixed Drive
 In practice a reservoir
contains at least two drive
mechanisms.
 It is the job of the reservoir
manager to identify the
strength of the drives as
early as possible in the life
of the reservoir to optimize
the reservoir performance.

51. Secondary Recovery
 It is the result of human
intervention in the reservoir to
improve recovery.
 It is done when the natural drives
decreased to low efficiencies.
 The purpose of secondary
recovery is to maintain reservoir
pressure and to displace
hydrocarbons towards the
wellbore.
 Two techniques are commonly
used:
 Water Flooding
 Gas Flooding

52. Secondary Recovery
1) Water Flooding
 This method involves the
injection of water at the
base of a reservoir to:
i. Maintain the reservoir
pressure, and
ii. Displace oil towards
production wells

53. Secondary Recovery
2) Gas Flooding
 It is similar to water flooding
method in principal.
 It is used to maintain gas
cap pressure even if oil
displacement is not
required.

54. Enhanced Recovery
 Also known as tertiary recovery
method.
 Primary and Secondary recovery
methods usually only extract about
35% of the original oil in place.
 Many enhanced oil recovery method
have been designed to increase this
figure. Some of them are:
1) Thermal EOR
2) Chemical EOR
3) Miscible Gas Flooding

55. Thermal EOR
 Heat is used to improve oil
recovery by reducing the
viscosity of heavy oils and
vaporizing lighter oils. The
techniques includes:
1) Steam injection
2) In situ combustion
3) Microwave heating downhole
4) Hot water injection
 It is hazardous to environment,
however the most efficient EOR
method.

56. Chemical EOR
 In this method chemicals are
added to water in the injected fluid
to alter the flood efficiency in such
a way to improve oil recovery.
 This can be done in many ways:
I. Increasing water viscosity
II. Decreasing the relative
permeability to water
III. Increasing the relative
permeability to oil
IV. Decreasing the interfacial tension
between the oil and water phases

57. Miscible Gas Flooding
 This method uses a fluid that is
miscible with the oil.
 Such fluid has no interfacial tension
with the oil.
 This flush out all the remaining oil in
place.
 Mostly Gas is used, as gas is
miscible in oil, have high mobility and
can easily enter all the pores in the
rock.
 Three types of gas are commonly
used:
1. Carbon dioxide
2. Nitrogen
3. Hydrocarbon Gases

58. Infill Recovery
 At the end of the reservoir life, infill drilling is done to improve
the production rate.
 Direct access to oil is done, which are left unproduced by all
the natural and artificial drive mechanisms.
 It may be very coasty, while the product might not be great.

59. References
 Selley, Richard C., and Stephen A. Sonnenberg. Elements of petroleum
geology. Academic Press, 2014.
 North, FK. Petroleum geology. Springer, 1985
 Basic Petroleum Geology Peter K link (3rd Edition)
 Rivas, José. "Gravity and magnetic methods." Short Course on Surface
Exploration of Geothermal Resources (2009): 1-13.
 Eventov, Leonid. "Applications of magnetic methods in oil and gas
exploration." The Leading Edge 16.5 (1997): 489-492.
 Карцев, Алексей Александрович. Geochemical Methods of Prospecting
and Exploration for Petroleum and Natural Gas. Univ of California Press,
1959.
 https://www.slideshare.net/hzharraz/well-logging