“Petroleum from the Ocean” From The Water Encyclopedia
http://www.waterencyclopedia.com/Oc-Po/Petroleum-from-the-Ocean.html
Petroleum (literally, "rock oil") is a substance that has formed beneath the surface of the
Earth over eons. The remains of ancient plants and animals have been buried and
compressed beneath thousands of feet of sand, mud, and rock. The organic materials,
under certain geological conditions, have been transformed by overburden pressure and
subsurface heat into hydrocarbon compounds, such as crude oil and natural gas.
Discovery and Use
Petroleum substances have been discovered and used as fuels for many centuries,
originally at the sites of natural seeps and leaks from fissures in the Earth's surface. In the
modern era, petroleum resources are sought and exploited from locations that are more
difficult and hazardous, including offshore. The petroleum deposits discovered in
offshore areas contain the same kind of hydrocarbon substances as those found onshore.
For example, a form of natural gas called gas hydrate is available both onshore and
offshore, but offshore resources are particularly of interest because of their volume and
potential for future large-scale development.
The reason offshore petroleum exploration and development are so prominent in this
century is that many onshore petroleum resources have either been exhausted, are not
economically producible, or are unable to be fully developed because of restrictions of
national ownership or geopolitical problems. The expansion of resource development
offshore is inevitable because of the growing demand for petroleum and petroleum
products.
Locations of Resources.
Offshore locations where petroleum resources are being found and developed for the
market occur worldwide, wherever prospects for economic development exist. Presently,
the petroleum industry is investing in exploration and development of oil and gas fields in
offshore locations such as Newfoundland, Alaska, California, the Gulf of Mexico, the
Caribbean Sea, Mexico, Brazil, Venezuela, West Africa, the North Sea, the North
Atlantic Ocean, the Caspian Sea, Western Australia, Malaysia, Indonesia, New Zealand,
and the South China Sea. Prospective
This platform, located in the Java Sea, is producing petroleum from a reservoir under the
seafloor.
areas are being sought offshore in all of the onshore petroleum basins, and wherever
correlations of continental geologic structures are found.
Technological Advances
The technology is presently available to explore, drill, produce, and transport petroleum
in water up to 2,300 meters (7,500 feet) deep, and further innovations are predicted to
extend the depth range of future operations. In addition, remote sensing and remote
control technology are being applied in facilities that cannot be directly operated by
personnel, who live and work either in onsite quarters or onshore.
Every country that has dominion over part of the continental shelf of the ocean is
investigating the possibility that petroleum resources may be found and developed there,
with the help of modern technology. The estimated petroleum reserves of a region
provide a solid incentive for capital investment in its economic and social development.
Offshore Exploration.
Exploration of offshore petroleum prospects involves various technologies. Seismic
surveying uses seismic waves propagated in the crust of the Earth to identify and map
rock structures that are likely to contain petroleum reservoirs, such as basins and traps.
When likely structures are found, other technologies are applied to obtain additional
information about the formations being studied. These may include core sampling of the
rocks with geological and laboratory analysis; data logging
Offshore petroleum production yields tremendous economic benefits yet presents
substantial risk to human life and the environment. In March 2001, the Brazilian-owned
Petrobras oil rig collapsed after explosions destroyed its substructure, and several
workers were killed. The company collected or dispersed all but 3,200 gallons of waste
oil at the location, averting a major spill.
and interpretation of formation characteristics; geochemical sampling and analysis of
reservoir rocks and fluids; and reservoir modeling to evaluate the potential for economic
development and exploitation.
The exploration stage is increasingly being integrated with other stages in petroleum
resource development and management, so that all information and data obtained are
additive in understanding the geologic structures being characterized and exploited.
Offshore Drilling.
If the prospects for reservoir and field development are economically feasible, based on
estimates of recoverable reserves, current market prices, and possible environmental
impact, exploratory drilling can begin. The drilling program is designed according to the
characteristics of rocks and formations that have been identified during the exploration
stage.
Offshore drilling involves the use of various technologies and types of equipment,
continually being upgraded and improved for purposes of both cost efficiency and
environmental protection. Drilling ships, semi-submersible drilling barges, or other
mobile drilling units are preferentially used for offshore drilling. In some locations,
permanent drilling platforms are installed offshore so that development wells can also be
drilled at that location, though this was done more often in the past. Offshore wells being
serviced or worked over or redrilled may also require reentry of the boreholes or addition
of more boreholes to an existing well, requiring the use of specialized drilling rigs and
equipment.
The evaluation of the reservoir continues as data are accumulated and as the primary
resources are depleted, and additional boreholes may be installed in order to exploit fully
the oil or gas deposit.
Tanker carriers are a major mode of export for petroleum resources. This tanker is
assisted by a tugboat in the Panama Canal.
Offshore Production.
Production can begin when the wells have been drilled and completed—that is, when all
downhole and surface equipment has been installed and the startup of production is
approved. As noted previously, offshore production involves the use of a wide variety of
equipment and technology. Offshore production structures in the past were commonly
installed as a permanent structure, but modern production structures include specialdesign production ships, mobile production units, columnar and compliant structures and
buoys that are tethered or moored to the sea floor, as well as subsea production systems
with underwater wellheads. If an underwater pipeline is not used to transport the well
fluids onshore or to another production platform, facilities for offshore storage and
offloading may also be installed for pickup by a tanker.
Offshore production wells may be vertically arranged with respect to the producing
formation, or may drain reservoir fluids through inclined or horizontal boreholes. Some
formations may best be drained with multilateral wells, with several branches entering
the producing formation at different depths and in several flow units.
Production may be possible without well pumps in some locations, if there is sufficient
reservoir pressure to drive the fluids toward the wells. However, artificial lift and
pressure boosting of well fluids are common procedures in offshore wells. Enhanced
recovery methods such as gas or water injection are also used to drive or control reservoir
fluid flow toward the wells.
Offshore production and drilling structures that are not removed from their offshore
locations when production ceases and instead are abandoned by operators can be
converted into artificial reefs that provide a habitat for marine life. On the other hand, oil
leaks and spills from the abandoned structures can be ecologically harmful.
Marine Transportation.
The export of oil and gas produced from offshore fields to onshore markets is
accomplished primarily by underwater pipelines or by tanker carriers. Pipelines of
various diameters and design may be buried in the sea floor or lie on top of it; the
pipelines may be connected into systems of flowlines from multiple wells and fields, or
may feed the product they carry to nearby storage tanks or tanker carriers. The tankers
may serve a single well or field, or may gather and deliver products at several ports and
transportation terminals. Both pipeline and tanker designs are changing to better
accommodate well fluid properties, distance and hazards of the transportation route, and
structural standards.
The reliability, economic operation, and environmental protection aspects of both
underwater pipelines and tankers are improving. Remote sensing, remote control, and
deep-water maintenance and repair are both detecting and preventing pipeline leaks. New
standards for construction and operation of tankers are being applied to avoid accidents
and associated spills. New technology is being developed to treat and process well fluids
offshore, in order to decrease the volume of product being transported and to decrease the
risk of leaking or spilling well fluids in the ocean environment.
Economic Value
The value of energy-rich petroleum in all of its forms lies in the many products that can
be made from it and the importance of their uses. Crude oil, natural gas, and other
hydrocarbon compounds are the bases of the fuel products that are essential for modern
modes of transportation, which are predominantly fueled by motor gasoline, jet fuel, and
diesel fuel. Petroleum also provides fuels for heating, industrial-manufacturing processes,
and generation of electricity. Petroleum can be converted into petrochemicals and
derivative products, such as pharmaceutical ingredients, plastics, and building materials,
which represent other portions of the petroleum-source market.
Both supply and demand factors drive the investments and operations that the petroleum
industry makes in exploring and exploiting petroleum resources. When petroleum prices
in the market are high, the industry can afford to produce resources that might otherwise
be uneconomic and can invest in new technology to reach resources that would otherwise
be unavailable. When petroleum prices in the market are low, even proven reserves may
not be produced because the cost of development and production would not allow any
profit for operators.
The definition of reserves depends upon economic factors as well as actual accumulations
of petroleum. Limitations of the technology needed to exploit reserves may also affect the
definition and the potential for present development.
Countries without domestic petroleum resources are increasingly dependent on imported
oil and gas, derived fuels, and petrochemicals, a factor that affects their domestic
security. Petroleum resources define modern trade patterns and stimulate both
international marketing and the potential for war. As petroleum supplies decrease and
their prices climb, the pressure to develop more expensive reserves and to develop
alternative energy sources is expected to increase.
SEE ALSO ENERGY FROM THE OCEAN; MINERAL RESOURCES FROM THE
SPILLS: IMPACT ON THE OCEAN; TRANSPORTATION.
OCEAN; OIL
Carolyn Embach
Bibliography
Energy Information Administration. Annual Energy Outlook 2000: With Projections to
2020. DOE–EIA–0383 (2000). Washington, D.C.: December 1999.
Glasner, David. Politics, Prices, and Petroleum: The Political Economy of Energy. San
Francisco, CA: Pacific Research Institute for Public Policy, 1985.
Hyne, Norman J. Geology for Petroleum Exploration, Drilling, and Production. New
York: McGraw-Hill, 1984.
GAS HYDRATE
Gas hydrate is an ice-like, crystalline solid consisting of gas molecules, each surrounded
by a "cage" of water molecules. Gas hydrate may form as cement in the pore spaces of
sediment as well as in layers and nodules of pure hydrate. Most marine gas hydrate
contains methane.
Pressure and temperature are the two major factors controlling the formation and stability
of gas hydrate. Gas hydrate is stable at the temperatures and pressures that occur in
ocean-floor sediments at depths greater than 500 meters (1,640 feet). Gas hydrates are
also stable in association with permafrost in polar regions, both in offshore and onshore
sediments.