Sedimentary the energy levels, where coarser grades(sand) will accumulate

Sedimentary
basins differ due to the origin of the rocks. Basins generally are the
accumulation of clastic rock which consist of minerals that later formed into
shale, discovered in area that undergone tectonic plate shifts.  These areas undergone a variation of tectonic
shifts either the divergent continental margins or the transform continental margin.
These shifts allow successful sedimentary episodes which formed sedimentary layers
consisting thick sediments in the center that thin towards the edges. During
transgression, sea level rose thus volume of subsidence around the basin
increase compared to the volume of sediments entering the basin, hence
increasing the depth of the oceans. The fine-grained sediments are the
potential petroleum source rocks have low permeability and often carried by the
sea towards the shore forming an accumulation around a low energy environment.
While, the during the regression, the deposits move seaward into a high energy
environment resulting the basin shallower. This sequence occurs as the supply
of sediments is greater that the accumulation amount in the basin. The regression
allows coarse-grained to accumulate due to the high energy level in the basin.
The rocks have high permeabilities and become the reservoir rocks that layered
on top of the source rocks during transgressive phase. The accumulation of
sediments depends on the energy levels, where coarser grades(sand) will
accumulate on base level while the finer grades(clay) are in suspensions
accumulate on top of the coarser grades. During periods of low orogenic
activity, erosion of land is at minimum, chemical weathering occurs at a rapid
rate upon completion, stable components were furnished from igneous and
metamorphic rocks, such as quartz and zircon, for clastic sediments. The
clastic sediments may be cemented by carbonate or clay compound precipitated
from the sea water. The change in climatic conditions of area allow different
types of sediments accumulation in the basin, from clean granular material to
organic material that later serves as source rocks for hydrocarbons as well as
impermeable cap rocks. The change in climatic conditions results in variable
episodes of fine particles on top of coarse particle forming the layers that
become caprocks of the reservoirs. The reactive clays and unstable minerals are
mixed with other grains forming a large portion of cementing agents.

Hydrocarbons
form from the degradation of organic materials from dead plants and animals
through decomposition by bacteria. The depletion of oxygen leads to anaerobic
condition which reduces the organic matter by removal of oxygen. The products
of decomposition will essentially compound of carbon, hydrogen, and oxygen. The
low energy environment during transgression allows sedimentation of organic
matter which would be buried under the fine-grained sediments, so it will be
preserved thus forming the source rocks of petroleum. During the burial, the environment
is slowly approaching the thermodynamic equilibrium with low temperature, the
organic matter is subjected to both microbial and chemical reaction that
transforms into kerogen. Consecutive deposition of sediments leads to deeper
burial which increases both pressure and temperature that lead to formation of
oil from kerogen this process called catagenesis. While on the higher zone,
metagenesis takes place where petroleum changes to graphite and methane. Compaction
occurs as soon as sediments begin to accumulate, the original accumulations are
buried deeper, due to layers of continued sediment on top, the water from the
deeper sediments is expelled, resulting in an increase in density and decrease
in porosity. The chemical changes occurring in the interstitial fluid produce precipitates
that strengthen the cohesive formation of the material. After expulsion of the
pore water, petroleum formed in rich shale may form continuous phase and move
along thread-like channels under applied stress. The optimum temperature for
generation of petroleum us about 200 degree Fahrenheit, assisting the primary
migration of oil. The migration of hydrocarbons from the point of release from
a source rock to the top of the trap intimately associated 

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