principal displacement zone
The zone or plane of dip-slip or strike-slip that accounts for greatest proportion of accumulated strain. Subsidiary structures such as synthetic and antithetic faults and folds (e.g., fault splays, back-thrusts, fracture zones, en echelon folds) will be kinematically linked to the PDZ.
En echelon folds
two or more folds arranged with similar orientations that are distributed in a relatively narrow and persistent zone
Restraining bend
Strike-slip motion at a bend in the PDZ that produces compressional structures such as thrusts and pop-up ridges. The left or right handedness of bends is determined by looking along the trend or strike of the fault
Releasing bend
Strike-slip motion at a bend in the PDZ that produces extensional structures. Pull-apart, or strike-slip basins are commonly developed at releasing bends. The left or right handedness of bends is determined by looking along the trend or strike of the fault
Pull-apart basin
a structural basin where two overlapping (en echelon) strike-slip faults or a fault bend creates an area of crustal extension undergoing tension, which causes the basin to sink down.
Inverted basin
the relative uplift of a sedimentary basin or similar structure as a result of crustal shortening.
Transverse Ranges
a group of mountain ranges of southern California, in the Pacific Coast Ranges physiographic region in North America.
Salton Sea
a shallow, landlocked, highly-saline body of water in Riverside and Imperial counties at the southern end of the U.S. state of California
Dead Sea
high salinity step-over rift
Pole of rotation
A point on the Earth's surface which defines a line through the centre of the Earth about which the relative motion of two plates may be described.
Small circles of rotation
Assuming transform faults in oceanic crust are pure strike-slip, they normally follow small circles on the earth’s surface. One may use them to find the pole of rotation for divergent plates moving apart on a sphere
High-friction strike-slip fault
the buildup of stress along the margin of two stuck plates that are trying to slide past one another. They eventually rupture along the fault. The rock is deformed as it builds up strain in the plates; stress increases along the contact.
Low-friction strike-slip fault
have little deformation at the contact
Positive flower structure
linear antiforms that are cut longitudinally along their apex by the upward-diverging strands of a wrench fault.
Negative flower structure
linear, shallow synforms that are displaced by upward-diverging strands of a wrench fault having mostly normal separations.
Thick-skinned fault
crustal shortening that involves basement rocks and deep-seated faults
Thin-skinned fault
eformation in plate tectonics at a convergent boundary which occurs with shallow thrust faults that only involves cover rocks (typically sedimentary rocks), and not deeper basement rocks.
Right-lateral
a type of strike-slip fault where the right block moves toward you and the left block moves away.
Left-lateral
If the block opposite an observer looking across the fault moves to the left
Dextral
the block on the other side of the fault moves to the right, or if straddling the fault the right side moves toward the observer.
sinistral
(left-handed) if the block on the other side of the fault moves to the left, or if straddling the fault the left side moves toward the observer.
Oblique-slip
occurs when there is a downward movement of the earth's surface, like that experienced with 'normal movement', while at the same time having a sideways movement.
Transtensional
characterized by both extensional structures (normal faults, grabens) and wrench structures (strike-slip faults)
Transpressional
a type of strike-slip deformation that deviates from simple shear because of a simultaneous component of shortening perpendicular to the fault plane. This movement ends up resulting in oblique shear.
Simple shear
In asymmetric rifts ('Wernicke' model) simple shear occurs at depth. The locus of lower crustal extension may be displaced from the upper crustal rift. Highest heatflow and volcanic activity may be offset from rift axis. Sense of asymmetry may shift along strike, producing transfer zones
Strain ellipse
fault plane strike is normal to the axes of en echelon folds and parallel to the compressional axis.
San Andreas fault zone
a continental transform fault that extends roughly 1,200 kilometers through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip.
Indent-linked strike-slip fault
Continental collision can cause crustal shortening and thickening by thrusting and escape or by extruding crustal blocks along conjugate strike-slip faults within the plate. These types of collision-related strike-slip faults between continental blocks are classified as indent-linked strike-slip faults
Trench-linked strike-slip fault
lie parallel to the trench in the accommodating part of the trench-parallel component of oblique convergence of subducting plates
Synthetic (Riedel) shear
Parallel arrays of faults that form during the early stages of strike-slip formation. They are oriented at low angles to the principal displacement zone, commonly about 15o, and are synthetic to the PDZ. As deformation continues the Riedel shears become linked and part of the PDZ.
Antithetic (Anti-Riedel) shear
depart by ∼75° from the Riedel shear zones of which they are a part, and are especially abundant in transfer zones where they create hard linkages between overstepping R-shears
Horsetail splay
Feature which results when displacement of strike-slip tectonics is distributed through branching splay faults forming an imbricate fan.
En echelon normal faults
closely-spaced, parallel or subparallel, overlapping or step-like minor structural features in rock (faults, tension fractures), which lie oblique to the overall structural trend
Sidewall repot
An alternative to continuous coring is the retrieval of discrete samples from the wellbore face known as sidewall cores
Shutter ridge
Ridge formed by vertical, lateral, or oblique displacement crossing an area with ridge and valley topography, which displaced part shutting in the valley.
Sag pond
a natural depression associated with a fault or associated with a pull-apart basin along a fault system can hold water, even temporarily
Bookshelf faulting
model in which initially ridge-parallel faults are rotated by simple shear
Pure strike-slip
A straight purely strike-slip fault can move without causing any distributed deformation in the wall rocks
Divergent strike-slip
This is a result of oblique seafloor spreading where the direction of motion is not perpendicular to the trend of the overall divergent boundary
Tectonic escape
a branch of strike-slip tectonics that involves the collision and deformation of two continental plates.
North Anatolian fault zone
an active right-lateral strike-slip fault in northern Anatolia, and is the transform boundary between the Eurasian Plate and the Anatolian Plate.
Lazy-S basin
pull-apart basins between sinistral faults
Z-shaped basin
pull-apart basins between dextral faults
Rhomboidal basin
pull-aparts or "rhomb grabens" result from lengthening of an S or Z-shaped basin with increased strike-slip offset and characteristically contain two or more sub-circular deeps within the basin floor
Spindle-shaped basin
initial opening across releasing fault bends produces spindle-shaped basins defined and often bisected by oblique-slip faults connecting the discontinuous ends of the strike-slip faults
Pull-apart floored by oceanic crust
As plates made of oceanic crust pull apart, a crack in the ocean floor appears. Magma then oozes up from the mantle to fill in the space between the plates, forming a raised ridge called a mid-ocean ridge.
Death Valley
a graben, or rift valley, formed by the sinking of a tremendous expanse of rock lying between parallel uplifted, tilted-block mountain ranges to the east and west.
Highly transpressional strike-slip fault
a type of strike-slip deformation that deviates from simple shear because of a simultaneous component of shortening perpendicular to the fault plane. This movement ends up resulting in oblique shear.
Vienna basin
tectonic burial basin and sedimentary basin in the seam area between the Alps, the Carpathians and the Pannonian Plain. And is characterized by four distinct tectonic phases; (1) Early Miocene piggyback basin, (2) Middle–Late Miocene pull-apart basin, (3) Late Miocene–Pliocene compression and basin inversion, and (4) Quaternary basin formation
slab rollback
occurs during the subduction of two tectonic plates, and results in seaward motion of the trench. Forces perpendicular to the slab at depth (the portion of the subducting plate within the mantle) are responsible for steepening of the slab in the mantle and ultimately the movement of the hinge and trench at the surface
Pannonian basin
a geomorphological subsystem of the Alps-Himalaya system, specifically a sediment-filled back-arc basin which spread apart during the Miocene
Ridge basin
a type of fault-bend basin developed in front of a releasing bend on the San Gabriel Fault, along which the upper crust stretched and subsided to form a space in which sediments could be accommodated.
Los Angeles basin
a sedimentary basin located in southern California, in a region known as the Peninsular Ranges. The basin is also connected to an anomalous group of east-west trending chains of mountains collectively known as the Transverse Ranges. The present basin is a coastal lowland area, whose floor is marked by elongate low ridges and groups of hills that is located on the edge of the Pacific Plate.
Oceanic transform fault
faults that offset mid-ocean ridges slip through earthquakes and aseismic creep
Null point
The point of change from net extension to net contraction in inverted basins
Inversion
The reversal of features, particularly structural features such as faults, by reactivation
Sunda-style fold
Fold structure which changes from an anticline at the crest to a syncline or half-graben at depth.
Pre-inversion
Strata deposited prior to basin inversion
Post-inversion
Strata deposited following basin inversion
Syn-inversion
Strata deposited during basin invesion
Seals
A relatively impermeable rock, commonly shale, anhydrite or salt, that forms a barrier or cap above and around reservoir rock such that fluids cannot migrate beyond the reservoir
Breached trap
exposed oil trap after erosion or fault controlled deformation
secondary migration
the subsequent movement of hydrocarbons within reservoir rock; the oil and gas has left the source rock and has entered the reservoir rock
Evaporite seals
Certain evaporite minerals, particularly halite, can form excellent cap rocks or seals for hydrocarbon traps because they have minimal porosity and they tend to deform plastically
Giant oil and gas fields
all fields containing at least 500 million barrels of known recoverable crude oil
Light oil
an oil of low specific gravity or relatively low boiling point (as below about 200° C). Such as aromatic hydrocarbons
heavy oil
a form of unconventional oil that is thick and highly viscous, and therefore does not flow to production wells under normal reservoir conditions.
Condensate
a mixture of light liquid hydrocarbons, similar to a very light (high API) crude oil. It is typically separated out of a natural gas stream at the point of production
Natural oil and gas seeps
Crude oil and natural gas naturally enter the ocean at areas known as "seeps." These hydrocarbons leak out of the ground through fractures and sediments
Gas flushing
consists of an inert gas such as nitrogen, carbon dioxide, or exotic gases such as argon or helium which is injected and frequently removed multiple times to eliminate oxygen
Biodegration
the breakdown of organic matter by microorganisms, such as bacteria and fungi
Hydrodynamic flushing
cleaning of an oil system with high pressurized water
Water washing
the process of stripping. the more soluble hydrocarbons from a gas. or oil accumulation via dissolution in the. associated aquifer.
Tar accumulation
accumulation of heavy oil
Optimum preservation zone
Goldilock zone for hydrocarbon generation and preservation
deep destructive zone
happens where an oceanic and continental plate move towards each other. The heavier, more dense oceanic plate is forced under the continental plate. As it sinks below the continental plate the oceanic plate melts due to friction in the subduction zone. The crust becomes molten called magma. caused by dense oceanic crust at a steep angle
shallow destructive zone
happens where an oceanic and continental plate move towards each other. The heavier, more dense oceanic plate is forced under the continental plate. As it sinks below the continental plate the oceanic plate melts due to friction in the subduction zone. The crust becomes molten called magma. Caused by shallow dipping light continental crust.
Source kitchen
An area of the subsurface where source rock has reached appropriate conditions of pressure and temperature to generate hydrocarbons
Arabian basin
Paleozoic intraCratonic basins overlying crystalline basement. The Mesozoic basins formed as the results of the Late Permian and Early Triassic opening of the adjacent Neo-Tethys Ocean and the development of its margins (Tethys passive margins).
Michigan basin
sedimentary rocks that were deposited in a circular depression that formed in Earth's crust during Paleozoic time
Cratonic basin
sites of prolonged, broadly distributed but slow subsidence of the continental lithosphere, and are commonly filled with shallow water and terrestrial sedimentary rocks.
West Siberian basin
the largest hydrocarbon (petroleum and natural gas) basin in the world. relatively undeformed Mesozoic sag that overlies the Hercynian accreted terrane and the Early Triassic rift system.
Rio Grande Rise
separates the Santos and Pelotas Basins and is composed of western and eastern areas. Hot spots and faulting. is an aseismic structural high towering more than 3 km above the South Atlantic Ocean floor.
Walvis Ridge
is an aseismic ocean ridge in the southern Atlantic Ocean. More than 3,000 km (1,900 mi) in length, it extends from the Mid-Atlantic Ridge, near Tristan da Cunha and the Gough Islands, to the African coast (at 18°S in northern Namibia). The Walvis Ridge is one of few examples of a hotspot seamount chain that links a flood basalt province to an active hotspot.
Louann Salt
a widespread evaporite formation that formed in the Gulf of Mexico during the Callovian in the mid Jurassic.Louann formed in a rift as the South American and North American Plates separated, from an embayment of the Pacific Ocean.
Campeche salt
the contemporaneous salt layer that developed on the south margin of the Gulf rift. It extends from Campeche, Mexico north along the west margin of the Campeche Bank north of the Yucatan Peninsula. The Orca Basin is a distinctive brine pool on the Louisiana continental shelf.
Phase 1 opening in Gulf of Mexico
Yucatan and associated
tectonic blocks that now comprise eastern Mexico were translated eastward from the Pacific realm into positions near the modern western Gulf.
Phase 2 opening in Gulf of Mexico
Yucatan and the South Florida block were translated southeastward relative to North America,
rotating 6.7° counterclockwise about a pole located at 34°N, 74°W. This resulted in ca. 430 km of southeastward extension on the North
American coastal plain, 120 km of southward extension on the northern Yucatan shelf, and displacement of the South Florida Block from a
pre-rift position on the northwest Florida shelf to its modern position.
Fracking
is a well stimulation technique involving the fracturing of bedrock formations by a pressurized liquid.
geosteering
the optimal placement of a wellbore based on the results of realtime downhole geological and geophysical logging measurements rather than three-dimensional targets in space.
Bakken shale
Intra-cratonic basin in Montana, North Dakota, Saskatchewan and Manitoba. Wedged between 2 cratons creating depression and trends NS with anticline traps. Has to be fracked
Williston basin
a large intracratonic sedimentary basin in eastern Montana, western North Dakota, South Dakota, and southern Saskatchewan, that is known for its rich deposits of petroleum and potash. The basin is a geologic structural basin but not a topographic depression;
Permian basin
a large sedimentary basin in the southwestern part of the United States. The basin contains the Mid-Continent Oil Field province. This sedimentary basin is located in western Texas and southeastern New Mexico.
Eagle Ford shale play
a sedimentary rock formation in Texas. predominantly composed of organic matter-rich fossiliferous marine shales and marls with interbedded thin limestones.
Marcellus shale play
The Marcellus Shale was formed from the very first deposits in a relatively deep, sediment- and oxygen-starved (anoxic), trough that formed parallel to the mountain chain. sedimentary rock found in eastern North America.
parent well
the first well that is drilled on a piece of land or location
Well spacing
a restriction on the number of wells that can be drilled on a given area.
Intra-cratonic sag basin
occur in the middle of stable continental or cratonic blocks. They are rarely fault bounded, although strike-slip faulting can occur within them.
Nesson anticline
the largest hydrocarbon productive structure in the North Dakota portion of the Williston basin. Structural trap related to the Bakken formation. Depression with anticlines at the bottom
Brittleness
hard but liable to break or shatter easily.
Sub-salt sag basin
Bains that form after rifting events that filled with salt.
Kwanza basin
Sub-salt sag basin play that lies in the lower region of the Angola Basin. It was formed due to the opening of the South Atlantic Ocean in the late Cretaceous period. It is characterized by a thick basement and crustal-scale domain
Campos basin
s considered a divergent boundary basin and its development relates to an extensional geotectonic context that was established due to the separation between the South American and African tectonic plates.
Santos basin
Sub-salt play in South Atlantic. the stages of development described as rift, proto-oceanic, and oceanic
Offset well
is an existing wellbore that may be used as a guide for planning a well
Paleogeographic map
the end product of the sequence stratigraphic analysis.
Stratigraphic trap
variations within the rock strata themselves (e.g., a change in the local porosity and permeability of the reservoir rock, a change in the kinds of rocks laid down, or a termination of the reservoir rock) play the important role.
Structural trap
a type of geological trap that forms as a result of changes in the structure of the subsurface, due to tectonic, diapiric, gravitational and compactional processes.
closure
the uplift of sediments juxtaposed to the piercement dome, by the top seal being an overlying impervious bed and the lateral seals being formed by structural dip, by sealing faults, or by the piercement salt.
Direct hydrocarbon indicator (DHI)
an anomalous type of seismic amplitude that may occur due to the presence of hydrocarbons. They occur due to a change in pore fluids, which cause a change in the bulk rock’s elastic properties.
Burial plot
A diagram that shows the depth of burial corrected for compaction of each rock unit (subsidence curve) versus the timing of the essential elements in a petroleum system