THE HISTORY OF EARTH AND LIFE
Review Sheet for Midterm Exam 01
You are responsible for knowing the content of my lectures. This is not everything I lectured on but it
is a lot of it. Do not just study these as what is the definiti
Divergent Basins: Gravity-Induced Faulting
Gravity-induced downslope movement has been invoked by structural geologists to explain an almost dizzying
variety of phenomena on almost all geologic scales. It has been used, for example, as an interpretation o
Divergent Basins: Growth Faults
By far the greatest number of hydrocarbon traps of the non-basement-involved type have been found along passive
margins in association with growth faulting, so named because of its syndepositional nature. They are best
Divergent Basins: Shale Movement Faults
The conditions that encourage the flowage of shale within a thick wedge of clastic deposits are primarily related to
retarded dewatering of shale and to the overall sequence of sediments in a regressive (progradatio
Strike-slip, or non-arc, basins are formed along convergent margins where the plates move by transcurrent faulting.
Strike-slip basins are small basins that form through a combination of both the transcurrent fault movements and
Convergent Basins: Non-Basement-Involved Faulting
The primary structural style in this category is the decollement foreland thrust-fold belt. Due to the thorough work of
such authors as Price and Mountjoy (1970), Dahlstrom (1970), and Bally, Gordy and Ste
Divergent Basins: Salt Movement Faults
Extension above salt structures causes anticlinal warping and normal faulting associated with crestal collapse that
usually occurs with shallow penetration. The latter is sometimes termed keystone, for reasons that s
Convergent Basins: Overview
There are four basin types that form when plates converge near continental margins. These are the forearc, backarc,
strike-slip (or non-arc) and collision basins. All four convergent margin basin types have a number of features
There are two major types of basins that are located in the interior of plates on the stable continental crust or craton.
The first cratonic basin type forms only in the central areas of continents, so these basins have often been called
The concept of structural style is based on comparative tectonics. Its greatest utility lies in identifying certain basic
patterns of deformation and faulting that are repeated in geologic provinces throughout the world. Studies of
1. Intracontinental rifts, proto-oceanic (new ocean) basins and oceanic basins are
genetically related to what type of plate boundary?
2. _ basins are generally long, linear, asymmetric basins with a one-sided
Divergent Basins: Overview
Divergent or rift basins are closely linked with plate divergence and seafloor spreading. These basins generally form
as down-faulted failed arms, where continental plates are stretched but do not completely separate. They are u
Divergent Basins: Basement-Involved Faulting
Regional block faulting is perhaps the most widespread structural style in the earth's crust, characterizing a majority
of the world's passive continental margins ( Figure 1 ),
as well as numerous, lin
Convergent Basins: Basement-Involved Faulting
The two principal elements of basement-related structural styles are compressional fault blocks and their bounding
basement thrusts, which may range in inclination from near-vertical to less than 30 degrees. B
1 Secondary migration is governed primarily by:
2 What rock characteristics tend to make the best reservoirs?
(A) Coarse-to-medium grained, well-sorted.
3 Reservoir permeabilities typically range between:
(C) 5 and 500 millidarcies
Soil Texture Classes
colored marking tape and pen
No reagents required. Use the data produced from particle size analyses procedures.
Use up-to-date computer programs for chec
1 If a basin-wide surface is separating older beds from younger ones, then it is called:
(D) All of the above
2 Surfaces separating contiguous units always have two designations.
3 Which of these subsurface quantities can be contoured?
Simple Fault Traps
More often than not, structural traps containing hydrocarbons result from or are associated with some form of
faulting. Although there are numerous, and sometimes unique, types of fault traps, most generally have an
appearance similar t
Reservoir Porosity and Permeability
There are two fundamental physical properties that a good reservoir must have: (1) porosity, or sufficient void space
to contain significant petroleum; and, (2) permeability, the ability of petroleum to flow through the
Distribution of Trap Types
The formation of large traps concurrent with the stages of petroleum generation and migration has been a major
factor in the formation of most giant petroleum fields (Halbouty et al., 1970). A giant field is one that contains ov
At present, migration is the most poorly understood and least measurable stage in the cycle of generation, migration,
and accumulation. Primary migration, which involves the expulsion of petroleum from the source rocks, is still a
Reservoir Rock Types
Sandstones usually have primary porosity, which decreases with depth of burial as the grains are compacted and
intergranular cementation develops. However, leaching of carbonate cements and unstable minerals in sandstones
can cause go
Stratigraphic traps, due to lateral and vertical changes in rock type, account for about 13% of the world's reserves.
They fall within a wide range of categories. Some are associated with unconformities, whether above or below them
Traps must be sealed by impermeable barriers in order to stop the continued upward migration of petroleum. In the
case of anticlines ( Figure 1 ,
(a), only a vertical seal, or caprock, is required; but faults ( Figure 1 , (b) and stratigrap
Structural traps are the most common exploration target, since they are often relatively easy to detect and have
provided over three-quarters of the world's discovered reserves. This is particularly true of anticlines.
Anticlines may orig
The last critical factor in the cycle of generation, migration and accumulation is the development of a trap. A trap is
a geometric configuration of structures and/ or strata, in which permeable rock types (the reservoir) are surrounde
Using Data Points to Define Surfaces
Regional groups of well logs display distinctive thin sequences, key beds, and
similar curve configurations or kicks which are commonly called "correlation
points". Examination of cuttings and wireline curves at the sa
Using Surfaces to Delimit Units
It is clear to the subsurface geologist that operationally, log markers come first, that
the marker points generate surfaces, and that the surfaces, in turn, delimit or
enclose units. These units may be of three categories:
1. The thickness of a horizontal stratigraphic unit measured in a vertical hole is known as:
(A) an isopach value
2. Which of these terms refers to the thickness of an inclined unit measured in a vertical hole and
not corrected for dip?
General Issues in Interpretation
Figure 1 illustrates the fault-picking operation at a simple level.
We join the apparent breaks or steps in the reflections with a geologically plausible fault trace, continuing the pick
upwards and downwards unti