Petroleum Geology

1. Petroleum Geology

2. The Context of Petroleum Geology

3. What is petroleum geology
• It is the application of geology (the study of rocks) to the
exploration for and production of oil and gas.
• Geology itself is strongly based on chemistry, physics and
biology, involving the application of essentially abstract
concepts to data.
• In the past these data were basically observational and
subjective.
• Petroleum geology, in particular still rely on value judgments
based on experience and an assessment of validity among the
data presented.
• Exploration had advanced over the years as various geological
techniques were developed.

4. A History of Petroleum
Ancient: • Egypt: oil to preserve mummies
• China: natural gas for fuel
• Babylonia: oil to seal walls and pave streets
• America: tar to seal canoes
First Drilling: • America: using cable tool: to 70’ in 1859
First Product: • Kerosene for lamps (Gasoline an unwanted by-product)
Demand: • Industrial Revolution
- Internal Combustion Engine (1885)
- Global Economic Growth

5. Natural Oil Spills

6. Anticlinal Theory
Petroleum Accumulates in Structural Closure
Gas
Oil
Water
Drill here!

7. Exploration and Production : Seismic Surveys
•Seismic surveys are used to locate likely rock structures
underground in which oil and gas might be found
• Shock waves are fired into the ground. These bounce off layers
of rock and reveal any structural domes that might contain oil
We’ve just established what kind of structures tend to trap oil and gas in the Earth’s
crust, but how do we locate potential traps underground? One technique is to use
seismic surveys. In this technique, a Vibrator Truck fires shock waves into the
ground. The shock waves pass through some rock layers and bounce off others. By
recording how long it takes for the shock waves to arrive back at the surface allows
geologist to build a picture of the internal structure of the rocks beneath their feet.
An example of a seismic survey is shown in the diagram on the right. It reveals a
large underground dome in the rocks. As we have seen domes often trap oil and gas
so this may be a potential site to drill.
notes: The term seismic is derived from the Greek for “shake” (think earthquakes!)

8. Industry ‘Technological’ Milestones
1883: Anticlinal theory (where to drill)
1914: Seismograph invented (remote sensing)
2D Seismic Line
Gulf of Mexico (offshore)

9. Industry ‘Technological’ Milestones
1883: Anticlinal theory (where to drill)
1914: Seismograph invented (remote sensing)
1920s: Introduction of rotary drilling (well control, environment)

11. Large Land Drilling Rig
Rotary Drilling Rig Schematic

12. Industry ‘Technological’ Milestones
1883: Anticlinal theory (where to drill)
1914: Seismograph invented (remote sensing)
1920s: Introduction of rotary drilling (well
control, environment)
Start of waterflooding (improved
recovery)
1924: First electrical well logging (formation
evaluation)

13. Industry ‘Technological’ Milestones
1883: Anticlinal theory (where to drill)
1914: Seismograph invented (remote sensing)
1920s: Introduction of rotary drilling (well control, environment)
Start of waterflooding (improved recovery)
1924: First electrical well logging (formation evaluation)
1930s: Offshore drilling (access to prospective areas)

14. Jack-Up Drilling Rig (Texas Federal Waters ~150’ water depth)

15. Industry ‘Technological’ Milestones
1883: Anticlinal theory (where to drill)
1914: Seismograph invented (remote sensing)
1920s: Introduction of rotary drilling (well control, environment)
Start of waterflooding (improved recovery)
1924: First electrical well logging (formation evaluation)
1930s: Offshore drilling (access to prospective areas)
1960s: Digital computers (data manipulation)
1970s: Directional drilling
1980s: 3D seismic (enhanced imaging)

17. Relief Well Control

18. Petroleum System

19. DEFINITION
A Petroleum System is defined as a natural system that
encompasses a pod of active source rock and all related oil
and gas and which includes all of the geologic elements and
processes that are essential if a hydrocarbon accumulation is
to exist.
(Leslie B. Magoon and Wallace G. Dow, AAPG Memoir 60)
MR@Aug2008

20. • Source Rock - A rock with abundant hydrocarbon-prone organic
matter
• Reservoir Rock - A rock in which oil and gas accumulates:
- Porosity - space between rock grains in which oil accumulates
- Permeability - passage-ways between pores through
which oil and gas moves
• Seal Rock - A rock through which oil and gas cannot move
effectively (such as mudstone and claystone)
• Migration Route - Avenues in rock through which oil and
gas moves from source rock to trap
• Trap - The structural and stratigraphic configuration that focuses
oil and gas into an accumulation
Source: AAPG
PETROLEUM SYSTEM ELEMENTS
-DEFINITION
MJH@Mac2007

21. The elements
Overburden
Overburden
Seal layer
Source rock layer
Source rock layer
Reservoir layer

22. Top of oil window
Top of gas window
The processes
Generation Expulsion Accumulation
GOC
OWC
Migration Preservation

28. Reservoir Heterogeneity in Sandstone
Heterogeneity
Segments Reservoirs
Increases Tortuosity of
Fluid Flow
Heterogeneity May
Result From:
Depositional Features
Diagenetic Features
(Whole Core Photograph, Misoa
Sandstone, Venezuela)

29. Reservoir Heterogeneity in Sandstone
Heterogeneity Also May
Result From:
Faults
Fractures
Faults and Fractures may
be Open (Conduits) or
Closed (Barriers) to Fluid
Flow
(Whole Core Photograph, Misoa
Sandstone, Venezuela)

30. Questions?