The Boscán Oil Field is located 40 km southwest of

Maracaibo Maracaibo ( , ; ) is a city and municipality in northwestern Venezuela, on the western shore of the strait that connects Lake Maracaibo to the Gulf of Venezuela. It is the largest city in Venezuela and is List of cities in Venezuela by population ...

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

, and covers an area of about 660 square kilometers (240 square miles). The

field Field may refer to: Expanses of open ground * Field (agriculture), an area of land used for agricultural purposes * Airfield, an aerodrome that lacks the infrastructure of an airport * Battlefield * Lawn, an area of mowed grass * Meadow, a grass ...

produces a 10.5 degree

API gravity The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light a petroleum liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks ...

crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...

from the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

Misoa Formation locally called the Boscán Formation. Current estimates of oil in place are greater than 25 billion barrels of oil. The field was discovered in 1946 by Chevron with drilling of the Zulia 7F-1 well (renamed BN-257) which tested . This well encountered reservoir section very close to the Boscán east bounding fault at about measured depth (MD). Production began in 1947. Coastal and mixed-swamp plants are considered to have been the basis of the oil being formed. The field is currently operated by the Empresa Mixta Petroboscan, a joint venture between Petroleos de Venezuela (PDVSA) and Chevron.

Stratigraphy

The

stratigraphic section A stratigraphic section is a sequence of layers of rocks in the order they were deposited. It is based on the principle of original horizontality, which states that layers of sediment are originally deposited horizontally under the action of ...

at Boscán Field consists of

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

s and

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

s of

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

and

ages deposited in a tidally-influenced fluvial-deltaic depositional setting. The Oligocene sediments are commonly non-oil bearing and are dominantly

y. The Eocene sands are part of the Misoa Formation and form the producing reservoir section locally known as the Boscán Formation.

Structure

The Boscán structure is a southwest-dipping monocline (flat, tilting surface) which contains oil over a very large depth range from to below

sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...

. The reservoir is broken by a series of

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

s, many of which have strike-slip movement; these faults may compartmentalize the reservoir over parts of the field.

Trapping mechanism

The productive section in the field is associated with a regional

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...

between the Oligocene Icotea Formation and the older Eocene sandstones. Shales and other tight formations in the Icotea Formation provide the trap preventing vertical migration. On the east side of the field a large

strike-slip fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

provides additional trapping of oil, preventing it from moving laterally to the east.

Production

Boscán Field has produced over of oil, less than 6% of oil in place. There have been a total of 950

oil well An oil well is a drillhole boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas m ...

s drilled in the field with approximately 525 active wells as of December, 2015. Current production is approximately 110,000 barrels per day. The reservoir drive is a combination of weak

aquifer An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...

drive on the south flank, solution gas expansion, and gravity drainage. Produced water is currently injected at a rate of approximately 90,000 barrels per day for pressure maintenance support.

References

{{DEFAULTSORT:Boscan Field Oil fields of Venezuela

Stratigraphy

Structure

Trapping mechanism

Production

See also

References