Basin Analysis

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clinoform

sloping depositional surfaces

Lithosphere

the rigid outer part of the earth, consisting of the crust and upper mantle

mantle

the region of the earth's interior between the crust and the core, believed to consist of hot, dense silicate rocks (mainly peridotite).

underplating

the accumulation of partial melts at the base of the crust where an ocean plate is subducting under continental crust

lithospheric plates

regions of Earth 's crust and upper mantle that are fractured into plates that move across a deeper plasticine mantle.

heat flow

the movement of heat (energy) from the interior of Earth to the surface

Wilson Cycle

a model that describes the opening and closing of ocean basins and the subduction and divergence of tectonic plates during the assembly and disassembly of supercontinents

Bouguer gravity

is a gravity anomaly due to the composition of the earth's crust

Free-air gravity

the measured gravity anomaly after a free-air correction is applied to account for the elevation at which a measurement is made

craton

an old and stable part of the continental lithosphere

Eustatic sea level

the distance from the center of the earth to the sea surface

clastic wedge

refers to a thick assemblage of sediments--often lens-shaped in profile--eroded and deposited landward of a mountain chain; they begin at the mountain front, thicken considerably landwards of it to a peak depth, and progressively thin with increasing distance inland

Prodelta

Lying beyond the sloping front of the main body of a delta, below the depth of effective wave erosion

Shelf edge delta

deliver sediment to the deep water lowstand systems tracts

Maximum flooding surface

the surface that marks the transition from a transgression to a regression systems track

Play concept

A conceptual model for a style of hydrocarbon accumulation used by explorationists to develop prospects in a basin, region or trend and used by development personnel to continue exploiting a given trend

Fairway

The trend along which a particular geological feature is likely

. Heavy oil

A dense, highly-viscous oil that cannot easily flow from production wells under normal reservoir conditions.

light oil

A low density, low-viscous liquid petroelum that flows freely at room temperature.

prospect

A geologic structure in an area of exploration in which hydrocarbons have been predicted to exist in economic quantity.

API

is a measure of how heavy or light a petroleum liquid is compared to water: >10, lighter than water and floats

dry gas

Natural gas with mostly methane that occurs in the absence of condensate or liquid hydrocarbons

wet gas

Natural gas that contains less than 85% methane and more ethane and other more complex hydrocarbons

asthenosphere

The relatively plastic layer of the upper mantle on which the tectonic plates move

Vitrinite reflectance

A measurement of the maturity of organic matter with respect to whether it has generated hydrocarbons or could be an effective source rock

porosity

% of pore volume that can contain fliuds in a rock

depth conversion

transforming seismic data from a scale of time to depth to provide a picture of the structure of the subsurface independent of velocity.

isochron map

A contour map that displays the variation in time between two seismic events

Isopach map

A contour map that connects points of true stratigraphic equal thicknesses

Artifact

Seismic velocity differences in a seismic line reflecting a change in the stratigraphy.

Structural trap

sealed geologic structures capable of retaining hydrocarbons, such as a fault or a fold.

Stratigraphic trap

sealed geologic container capable of retaining hydrocarbons, formed by changes in rock type or pinch-outs, unconformities, or sedimentary features such as reefs.

Kerogen type

Type I, consisting of mainly algal kerogen and highly likely to generate oil; Type II, mixed terrestrial and marine source material that can generate waxy oil; and Type III, woody terrestrial source material that typically generates gas.

moho

The boundary between the crust and the mantle of the Earth, which varies from approximately 5 km [3 miles] under the mid-oceanic ridges to 75 km [46 miles] deep under the continents

onlap

The termination of shallowly dipping, younger strata against more steeply dipping, older strata,

disconformity

A geologic surface that separates younger strata from older strata and represents a time of nondeposition or erosion.

accommodation zone

occur at fault intersections consisting of belts of interlocking, oppositely dipping normal faults.

Facies

The overall characteristics of a rock unit that reflect its origin and differentiate the unit from others around it.

frontier basin

a basin where the exploration activities have not been carried out or a basin with short-term exploration activities and a significant volume categorized as undiscovered resources

Exploration company

companies involved in the high-risk/high-reward area of exploration and production focus on finding, augmenting, producing and merchandising different types of oil and gas

basin modeling

used to analyse the formation and evolution of sedimentary basins, often but not exclusively to aid evaluation of potential hydrocarbon reserves.
At its most basic, a basin modelling exercise must assess:

The burial history of the basin (see back-stripping).
The thermal history of the basin (see thermal history modelling).
The maturity history of the source rocks.
The expulsion, migration and trapping of hydrocarbons.

upstream

searching for potential underground or underwater crude oil and natural gas fields, drilling exploratory wells, and subsequently drilling and operating the wells

downstream

the refining of petroleum crude oil and the processing and purifying of raw natural gas, as well as the marketing and distribution of products

Gamma ray log

A common and inexpensive measurement of the natural emission of gamma rays by a formation. Gamma ray logs are particularly helpful because shales and sandstones typically have different gamma ray signatures that can be correlated readily between wells

Conventional exploration

The conventional oil drilling process includes the drilling of a well, a reservoir having pressure and oil flowing out of the ground

Unconventional exploration

the well is tight and the movement of oil takes longer geologic time. To alleviate the slow process, Chestnut Exploration & Production drills the oil horizontally and fracks it

Carrier bed

provide pathways for hydrocarbons to migrate from source rocks to reservoirs. Coarser grains and more porous. ie:sandstone, carbonates

2-D seismic data

A vertical section of seismic data consisting of numerous adjacent traces acquired sequentially.

3-D seismic data

A set of numerous closely-spaced seismic lines that provide a high spatially sampled measure of subsurface reflectivity

Time slice

A horizontal display or map view of 3D seismic data having a certain arrival time, as opposed to a horizon slice that shows a particular reflection. A time slice is a quick, convenient way to evaluate changes in amplitude of seismic data

Fence diagram

A graphical display of three-dimensional data and interpretations in two-dimensional perspective view. Geologic cross sections can be displayed in a network to form a fence diagram. Stratigraphic changes can be displayed clearly in fence diagrams.

horizontal drilling

s directional drilling in which the digging angle is at least 80 degrees from the perpendicular wellbore. Often useful in conjunction with hydraulic fracturing to explore gas reservoirs that were previously untappable

Fracking

the process of injecting liquid at high pressure into subterranean rocks, boreholes, etc. so as to force open existing fissures and extract oil or gas

Active rifting

thermal erosion of the lower lithosphere due to the upwelling of mantle material from convection or plumes. where rising mantle plumes initiate crustal stretching.

Passive rifting

where extension is caused by far-field stresses (generated at plate boundaries but at distance from them), such that buoyant asthenosphere mantle rises passively, partly in response to isostatic compensation

Mantle plume

a proposed mechanism of convection within the Earth's mantle. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots

Hotspot

volcanic locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle.

Asymmetrical rifting

(simple shear), post-breakup thermal anomalies in the mantle, or pre-existing compositional zones in the crust that predispose one of the margins to more melting than its conjugate

Failed rift

are extensional basins where continental rifting began, but then failed to continue to the point of break-up

Footwall block uplift

The relative amplitude of the footwall and hanging wall vertical movements is dominated by the nature of the fill in the half-graben: loading by sediment pushes the whole structure down, whereas loading by water (sediment-starved) allows more footwall uplift.

Steers head profile

Inactive rift that has gone into the sag phase. Sag due to the upwelling of hot mantle along with cooling and sag. rifting on both sides and rift fill in the basin, loading sediment causing it to subside

Pure shear model for rifting

refers to a change in shape without a change in volume, and a change in which the strain axis (sigma 1, sigma 2, sigma 3) do not rotate. Uniform and symmetrical

Sag basin

thick accumulations of sediment, generally more or less oval in shape, located entirely in the interiors of continental masses

Seaward-dipping reflector

are found on all volcanic passive margins and associated with the transition from continental rifting to full lithospheric separation and seafloor spreading

Simple shear

areas of greatest crustal thinning may be offset from areas of greatest asthenospheric uplift. Greatest heat flow and hence volcanic activity and dyke intrusion may be offset from a zone of highly extended crust. This zone comprises highly rotated blocks between imbricate, curved (listric) normal faults.

Lithospheric detachment

is only possible for a thickened lithosphere, which has been significantly weakened e.g. by water

Simple shear model for rifting

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

Subsidence history

The pre-rift, syn-rift, and post-rift of a rift system

Syn-rift

rocks deposited during an extensional geological regime (i.e. where rocks are under tension) which results in the general widening and deepening of sedimentary basins and allows significant infilling of sediments from the edges of the basin

Syn-rift section

a sequence deposited during active rifting, typically showing facies and thickness changes across the active faults, unconformities on the fault footwalls may pass laterally into continuous conformable sequences in the hanging walls

Thinned continent crust

found in rift zones, where the crust is thinned by detachment faulting and eventually severed, replaced by oceanic crust. The edges of continental fragments formed this way (both sides of the Atlantic Ocean, for example) are termed passive margins.

Volcanic rift margin

rifting is accompanied by significant mantle melting, with volcanism occurring before and/or during continental breakup.

Slab rollback

the process that involves an older oceanic crust, which is colder and more dense than other slabs, subducting at a steep angle. As the older slab collapses into the asthenosphere, it can "roll back" through the mantle

Depocenter

the part of a sedimentary basin where a particular rock unit has its maximum thickness

Transfer fault

A vertical or sub-vertical fault which, via dip-slip and strike-slip movements, allows the juxtaposition of two fault zones which have different displacement characteristics.

Necking zone

2 normal faults on both sides of the rift graben with volcanic upwelling at the floor

Breakup unconformity

an erosional surface characterizing the uplifted margins during rifting stage, often truncating wedge-shaped synrift sediments and separating them from younger postrift sequences that show little/no evidence of extension controlling their deposition

Beta factor

The amount of stretching in a rift system where b/a is beta (stretched width) / a (initial width)

Normal fault linkage

Normal faults grow along-strike by propagation of tips of different segments across relay ramps at any scale

Metamorphic core complex

exposures of deep crust exhumed in association with largely amagmatic extension

dog-leg fault pattern

normal fault pattern where the fault changes direction

Triple-armed rift system

“Y” shaped rift system, where the continental lithosphere is being stretched and is splitting

Decollement

A deformation structure formed by a gliding plane between two rock masses, also known as a basal detachment fault. Compressional settings

Detachment

associated with large-scale extensional tectonics. formed as either initially low-angle structures or by the rotation of initially high-angle normal faults modified also by the isostatic effects of tectonic denudation

Extensional salt detachment

The low density and strength of salt formed by evaporties causes sliding of the overburden and faulting caused by gravity

Passive margin foldbelt

Formed above salt or shale that extend and contract

rollover anticline

syn-depositional structure developed within the downthrown block (hanging wall) of large listric normal faults. develop as a response to extensional collapse of a passive continental margin

Synthetic normal fault

dip in the same direction as the major fault and enhance vertical extent of the fault

Antithetic normal fault

dip in the opposite direction of the major fault and lower the vertical extent

Fault inversion

an extensional fault is reactivated in the opposite direction to its original movement.

Ridge push

is a proposed driving force for plate motion in plate tectonics that occurs at mid-ocean ridges as the result of the rigid lithosphere sliding down the hot, raised asthenosphere below mid-ocean ridges

Salt pillow

subsurface structure containing salt that pierces the surrounding rock and forms in horizontal strata

Louann salt

a widespread evaporite formation that formed in the Gulf of Mexico during the Callovian in the mid Jurassic. The Louann formed in a rift as the South American and North American Plates separated, from an embayment of the Pacific Ocean

Campeche salt

southern Gulf of Mexico forms a late Middle Miocene to Recent passive margin foldbelt detaching in a northward direction over a 2-5-km-thick layer of Bajocian-early Callovian salt.

Conjugate margins

Margins that are joined

Updip extensional zone

characterized by landward-dipping and seaward-dipping normal faults superposed on older contractional detachment folds.

Downdip compressional zone

consists of salt-cored folds, thrusts, autochthonous salt diapirs, allochthonous salt canopies, and detachment folds with kink bands

Salt diapir

a type of geologic intrusion in which a more mobile and ductily deformable material is forced into brittle overlying rocks.

Salt roller

low-amplitude deflections of the upper surface of a salt layer which occur below zones of normal faulting in the overlying sediments

Salt evacuation

Evacuation of salt from a starved minibasin forms an extensive salt wing, which is subsequently remobilized by deposition of upper slope and outer shelf sediments on the wing

Minibasin

a subdivision of a depocenter that in turn is a subdivision of a basin. Sediment thickness is the primary basis for subdividing basins into depocenters. Structural elements separate one minibasin from another within a depocenter.

Salt canopy

Offshore tongues of salt are generated that may join together with others from neighbouring piercements

Salt weld

When a salt layer becomes too thin to be an effective detachment layer, due to salt movement, dissolution or removal by faulting, the overburden and the underlying sub-salt basement become effectively welded together.

Exhumation

the process by which a parcel of rock (that was formerly buried), approaches Earth's surface.

Prograding clastic wedge

are thick (> 500 m), less extensive (< 300 km) successions that consist of numerous, near-complete sequences and short-length shoreline tongues that form rising stratigraphic stacking patterns

underfilled basin

deep water and commonly marine sediments, known as flysch, are deposited

overfilled basin

the basin becomes completely filled. At this point, the basin enters the overfilled stage and deposition of terrestrial clastic sediments occurs.

flexure

the lithosphere can bend under applied loads and recover elastically if the load is removed

foreland basin

a structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend, by a process known as lithospheric flexure

Backbulge

the mass of sediment that accumulates in the shallow but broad zone of potential flexural subsidence cratonward of the forebulge

Eastern Venezuelan foreland basin

is a Neogene foredeep superimposed on a Mesozoic passive margin.

Maracaibo foreland basin

a foreland basin and one of the eight natural regions of Venezuela, found in the northwestern corner of Venezuela in South America. characterized by a large shallow tidal estuary, Lake Maracaibo, located near its center.

Appalachian foreland basin

a foreland basin containing Paleozoic sedimentary rocks of Early Cambrian through Early Permian age.

Orogenic belt

develops when a continental plate crumples and is uplifted to form one or more mountain ranges

Flexural forebulge

a flexural bulge in front of a load on the lithosphere. The load causes the lithosphere to flex by depressing the plate beneath it. Because of the flexural rigidity of the lithosphere, the area around the load is uplifted by a height that is 4% of that of the depression under the load.

Forearc basin

marine depositional basins on the trench side of arcs

Basin asymmetry for foreland basins

The lithosphere behaves as an elastic beam and flexes under the weight of the load forming the asymmetric shape characteristic of foreland basins

Deformation front

typically accompanied by the incorporation of parts of the basin into wedge-top piggy-back basins

Piggyback basin

a minor sedimentary basin developed on top of a moving thrust sheet as part of a foreland basin system. Piggyback basins form in the wedge-top depositional zone of a foreland basin system as new thrusts in the foreland cut up through the existing footwall containing the eroded wedge-top basins in the old thrust sheet.

Transverse filling of foreland basins

fluvial sedimentation orthogonal to the orogen

Longitudinal filling

fluvial sedimentation parallel to the orogen. follows the
present axis of maximum subsidence that parallels the thrust-load expressed by the strike of the thrust belt

Topographic load

extreme lateral mobility results in the vertical stacking of foreland basin depozones in the stratigraphic record.

Wedge top

sits on top of the moving thrust sheets and contains all the sediments charging from the active tectonic thrust wedge. This is where piggyback basins form.

Foredeep

the thickest sedimentary zone of a foreland basin and thickens toward the orogen. Sediments are deposited via distal fluvial, lacustrine, deltaic, and marine depositional systems.

Fold-thrust belt

a series of mountainous foothills adjacent to an orogenic belt, which forms due to contractional tectonics.

Pro-foreland basin

occur on the plate that is subducted or underthrust during plate collision. (1) Accelerating tectonic subsidence driven primarily by the translation of the basin fill towards the mountain belt at the convergence rate. (2) Stratigraphic onlap onto the cratonic margin at a rate at least equal to the plate convergence rate.

Retroarc foreland basin

forms on the upper plate (usually during continent-oceanic plate collision). form behind continental margin arc systems (Figure 3.16a), and they are filled largely with clastic terrigenous sediments derived from a fold-thrust belt behind the arc. A key element in foreland basin development is the syntectonic character of the sediments

Slab breakoff

leads to the generation of a shallow thermal perturbation which may melt the metasomatised mechanical lithosphere given its lower solidus and provide the source for syn-colli sional magmatism. It also allows the uplift and exhumation of high-pressure rocks.

rebound

As the Earth's crust deforms, the rocks which span the opposing sides of a fault are subjected to shear stress. Slowly they deform, until their internal rigidity is exceeded

Basin fill load

additional forces operate on the lithosphere, such as slab-pull, slab-detachment and slab roll-back, and play an important role in shaping the geometry of prowedge and retrowedge foreland basins

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