2 Fundamentals
About this chapter
A solid foundation in geology as well as algebra and trigonometry is essential to
understanding directional drilling techniques and procedures. Geology, a science based
on the history and structure of the earth, combined with a thorough knowledge of
mathematics, forms the core discipline necessary for proficiency in this complex
business. Although it is far beyond the scope of this manual to completely describe the
total essence of geology and mathematics, this chapter is designed to refresh any
knowledge that should already be a part of the directional drilling trainee.
Objectives of this Chapter
On completing this chapter the directional driller should be able to do the following
exercises:
Part A/Petroleum Geology
1. Describe the phases that occurred during the formation of the earth that resulted in the
various features of its surface and inner structures.
2. Be prepared to explain the several terrigenous sediments (clastic) that can found
under the Earth’s surface.
3. Be prepared to describe the four general classes of sedimentary materials and how
they are categorized by relative size.
4. Be prepared to define pyroclastic sediments and explain the various of sub-groups.
5. Describe the basic concepts of structural geology and how the various elements are
related to exploration and production of petroleum.
Part B/Algebra and Trigonometry
1. Observe and explain miscellaneous equations of algebraic and trigonometric
mathematics.
2. Be prepared to describe geometric descriptions of a circle.
3. Understand and solve equations applicable to various straight line problems.
4. Demonstrate an understanding of angles resulting from intersecting lines.
5. Demonstrate an understanding of circles and parts of circles resulting from
intersecting lines.
6. Demonstrate an understanding of the trigonometric quadrants identified by sine,
cosine and tangent; solve various equations using these quadrants.
2.1 Petroleum Geology
Rock is a natural substance composed of a mineral or group of minerals which lead to the
formation of rocks and to accumulations of hydrocarbons. A study of this phenomenon is
aimed to help directional drillers in understanding of geological environments. Geology
is so essential to the petroleum industry that a knowledge of the basic principles of this
science is desirable for anyone associated with oil or gas.
Geological information is acquired by observing rocks and their relationship to each
other as they were formed in the layers of the earth. Chronological events can then be
reconstructed in order to understand rock formations and, in the particular field of
petroleum geology, to be able to predict where oil accumulations might occur.
2.1.1 Basic concepts of geology
2.1.1.1 Early History of the Earth
The earth is thought to have originated some 4 to 5 billion years ago out of a condensing
cloud of cosmic dust. During its early life, the earth passed through a molten or partially
molten stage induced by gravitational compression or the release of energy by
radioactive elements. During this stage, the components of the earth separated to produce
a heavy core 4,400 miles in diameter, a mantle of lighter material some 1,800 miles thick
and a crust of the lightest materials some 10 to 30 miles thick (Figure 2-1). At the same
time, large amounts of water vapor and gases erupted to form the primeval atmosphere.
A second stage can be considered as the atmosphere developed and the earth cooled, rain
began to fall. Water coming down from the heights and flowing to the valleys eroded the
surface of the earth by removing particles of rocks whereas sedimentary accumulations
deposited in the lower reliefs.
The tectonic activity resulting from the internal adjustments led to the formation of
horsts and grabens filled with sedimentary deposits (Figure 2-2), as it is attested by the
Red Sea between Asia and Africa.
Life began in the oceans sometime in the Precambrian period and eventually spread onto
the land during the Devonian period (about 350 million years ago).
Fossils preserved in deposits attest to the progressive evolution of the fauna and flora
and enabled the succession of rocks to be subdivided into eras and smaller subdivisions.
The more important ones are shown in Table 2-1.
2.1.1.2 How is the duration of eras and subdivisions measured?
Absolute ages for these subdivisions were determined from studies of radioactive
minerals.
2.1.2 The Sedimentary Cycle
The classic cycle is one of uplift, weathering, erosion, transportation, deposition,
lithification and renewed uplift.
2.1.2.1 Weathering
Weathering can be either a physical process, a biological process or a chemical process
which all result in the breakup and the decay of rocks at the earth’s surface. Erosion is the
process or removing newly formed sediments and is caused by four agents which are also
responsible for the subsequent transportation of the sediment. This sediment
transportation can be achieved through the action of gravity, water, glaciers or wind.
2.1.2.2 Erosion and deposition
Erosion results from the action of many agents such as wind, freezing water, waves and
moving ice, which remove particles from the surface of the earth (Figure 2-3).
Unconsolidated deposits (A) resulting from the accumulation of those particles were
compacted by the weight of the overlying sediments (B) and, under the action of pressure
and heat, were transformed into metamorphic rocks. Most oil and gas accumulations
occur in sedimentary rocks.
2.1.2.3 Diagenesis
A name given to the processes which change sediments to a rock. As the energy of the
transporting agent slows down, removed sediments will deposit; the coarsest part would
drop first whereas the fine fraction (such as clay) might then be slowly deposited further
away. This natural segregation of coarse materials from fine, and the soluble from
insoluble, form the basis for the classification of sedimentary rocks.
Diagenesis occurs under the effects of compaction, dewatering (water squeezed out of
the sediments) or cementation (chemical processes). All these mechanisms can be
combined over a certain period of time.
About this chapter
A solid foundation in geology as well as algebra and trigonometry is essential to
understanding directional drilling techniques and procedures. Geology, a science based
on the history and structure of the earth, combined with a thorough knowledge of
mathematics, forms the core discipline necessary for proficiency in this complex
business. Although it is far beyond the scope of this manual to completely describe the
total essence of geology and mathematics, this chapter is designed to refresh any
knowledge that should already be a part of the directional drilling trainee.
Objectives of this Chapter
On completing this chapter the directional driller should be able to do the following
exercises:
Part A/Petroleum Geology
1. Describe the phases that occurred during the formation of the earth that resulted in the
various features of its surface and inner structures.
2. Be prepared to explain the several terrigenous sediments (clastic) that can found
under the Earth’s surface.
3. Be prepared to describe the four general classes of sedimentary materials and how
they are categorized by relative size.
4. Be prepared to define pyroclastic sediments and explain the various of sub-groups.
5. Describe the basic concepts of structural geology and how the various elements are
related to exploration and production of petroleum.
Part B/Algebra and Trigonometry
1. Observe and explain miscellaneous equations of algebraic and trigonometric
mathematics.
2. Be prepared to describe geometric descriptions of a circle.
3. Understand and solve equations applicable to various straight line problems.
4. Demonstrate an understanding of angles resulting from intersecting lines.
5. Demonstrate an understanding of circles and parts of circles resulting from
intersecting lines.
6. Demonstrate an understanding of the trigonometric quadrants identified by sine,
cosine and tangent; solve various equations using these quadrants.
2.1 Petroleum Geology
Rock is a natural substance composed of a mineral or group of minerals which lead to the
formation of rocks and to accumulations of hydrocarbons. A study of this phenomenon is
aimed to help directional drillers in understanding of geological environments. Geology
is so essential to the petroleum industry that a knowledge of the basic principles of this
science is desirable for anyone associated with oil or gas.
Geological information is acquired by observing rocks and their relationship to each
other as they were formed in the layers of the earth. Chronological events can then be
reconstructed in order to understand rock formations and, in the particular field of
petroleum geology, to be able to predict where oil accumulations might occur.
2.1.1 Basic concepts of geology
2.1.1.1 Early History of the Earth
The earth is thought to have originated some 4 to 5 billion years ago out of a condensing
cloud of cosmic dust. During its early life, the earth passed through a molten or partially
molten stage induced by gravitational compression or the release of energy by
radioactive elements. During this stage, the components of the earth separated to produce
a heavy core 4,400 miles in diameter, a mantle of lighter material some 1,800 miles thick
and a crust of the lightest materials some 10 to 30 miles thick (Figure 2-1). At the same
time, large amounts of water vapor and gases erupted to form the primeval atmosphere.
A second stage can be considered as the atmosphere developed and the earth cooled, rain
began to fall. Water coming down from the heights and flowing to the valleys eroded the
surface of the earth by removing particles of rocks whereas sedimentary accumulations
deposited in the lower reliefs.
The tectonic activity resulting from the internal adjustments led to the formation of
horsts and grabens filled with sedimentary deposits (Figure 2-2), as it is attested by the
Red Sea between Asia and Africa.
Life began in the oceans sometime in the Precambrian period and eventually spread onto
the land during the Devonian period (about 350 million years ago).
Fossils preserved in deposits attest to the progressive evolution of the fauna and flora
and enabled the succession of rocks to be subdivided into eras and smaller subdivisions.
The more important ones are shown in Table 2-1.
2.1.1.2 How is the duration of eras and subdivisions measured?
Absolute ages for these subdivisions were determined from studies of radioactive
minerals.
2.1.2 The Sedimentary Cycle
The classic cycle is one of uplift, weathering, erosion, transportation, deposition,
lithification and renewed uplift.
2.1.2.1 Weathering
Weathering can be either a physical process, a biological process or a chemical process
which all result in the breakup and the decay of rocks at the earth’s surface. Erosion is the
process or removing newly formed sediments and is caused by four agents which are also
responsible for the subsequent transportation of the sediment. This sediment
transportation can be achieved through the action of gravity, water, glaciers or wind.
2.1.2.2 Erosion and deposition
Erosion results from the action of many agents such as wind, freezing water, waves and
moving ice, which remove particles from the surface of the earth (Figure 2-3).
Unconsolidated deposits (A) resulting from the accumulation of those particles were
compacted by the weight of the overlying sediments (B) and, under the action of pressure
and heat, were transformed into metamorphic rocks. Most oil and gas accumulations
occur in sedimentary rocks.
A name given to the processes which change sediments to a rock. As the energy of the
transporting agent slows down, removed sediments will deposit; the coarsest part would
drop first whereas the fine fraction (such as clay) might then be slowly deposited further
away. This natural segregation of coarse materials from fine, and the soluble from
insoluble, form the basis for the classification of sedimentary rocks.
Diagenesis occurs under the effects of compaction, dewatering (water squeezed out of
the sediments) or cementation (chemical processes). All these mechanisms can be
combined over a certain period of time.
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