Japan Petroleum Exploration Co., Ltd.
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About Oil and Natural Gas


For many years, JAPEX has worked on development and production of oil and natural gas, which are energy resources called fossil fuels.

Fossil fuels are formed from prehistoric organisms decomposed underground over several to tens of millions of years, and are now available for use as energy resources. Fossil fuels in the liquid state is called oil, while those in the gaseous state is called natural gas.

Types of Oil & Natural Gas

Both oil and natural gas are made up primarily of hydrocarbon (H), which is a chemical compound consisting entirely of carbon (C) and hydrogen (H). They can be classified further into a variety of types depending on the structure of molecules and how they are bound.


Oil generally refers to a liquid composed mainly of hydrocarbons and containing some sulfur (S), nitrogen (N), and oxygen (O). Crude oil is a liquid extracted from oil fields underground from which gas and water are removed.


Crude oil samples were taken out from oil fields at our production facilities
(From left to right: extra-light oil, light oil, medium oil, bitumen (extra-heavy oil), oil sands (sands containing bitumen)

By applying heat and taking advantage of different boiling points, crude oil can be distilled and separated into oil. Oil, then, can be classified further, by the level of its density (API*), into light, medium and heavy oils, each of which are used for purposes that fit its properties.

* A measure for the gravity of oil set by the American Petroleum Institute. Crude oil with API more than 39 degrees are classed as "Extra-light", between 34 to 38 degrees are classed as "Light", between 29 to 33 degrees are classed as "Medium", between 26 to 28 are classed as "Heavy", and below 26 are classed as "Extra-heavy".

Major Uses of Oil

Gasoline (naphtha) and diesel oil, which are light in consistency, are used mainly as fuels to power vehicles and machines.

Oils that are medium to heavy inconsistency are used mainly as fuels for powering large-size machines, vessels, and airplanes, as well as for generating electric power. Heavy oils are used also as raw materials for chemical products such as plastic bottles, plastic products, and fibers.

Natural Gas

Natural gas is a flammable gas composed mainly of methane (CH4), which is colorless, odorless, and lighter than air. Natural gas is considered as the energy source with a lower environmental impact than other fossil fuels given its less emissions of carbon dioxide (CO2), nitrogen oxide (NOx), and sulfur oxide (SOx) when burned.

Natural gas, when cooled to 162˚C or -260˚F, is converted into liquefied natural gas (LNG).


Main Uses of Natural Gas

Natural gas is mainly distributed as city gas to general households and other users. It is also in high demand from large-scale plants and industrial facilities, as well as for power generation. Natural gas is also used as raw materials for chemical products.

Origin of Oil and Natural Gas

Oil and natural gas are formed underground, over several to tens of millions of years, from prehistoric organisms decomposed by high subterranean heat and microorganisms. Oil and gas collect in formations underground, where they are prone to accumulate, to form oil/gas fields.

How Oil and Natural Gas Are Formed

[1] Dead plants and animals accumulate and form strata

  • Dead plants and animals on land and under the sea sink into the sea and lake floors, together with microorganisms and dirt, and accumulate there.

[2] They then transform into rocks that have the potential to produce oil/natural gas

  • Dead plants and animals pile up and form strata.
  • Dead plants and animals piled up are decomposed by microorganisms underground, over several to tens of millions of years, into organic compounds from which oil and natural gas can be derived
    • These organic compounds are called kerogen, and kerogen-rich rocks are called source rocks.

[3] Kerogen transforms into oil and natural gas under high-temperature and high-pressure environments

  • Kerogen then transforms into oil and natural gas by high subterranean heat and pressure underground.
  • Oil and natural gas then slowly move upward through subterranean cracks in strata.

[4] Oil and natural gas then accumulate

  • Oil and natural gas moved upward then collect in areas that satisfy the following two conditions:
    • Condition 1: Underneath a dome-shaped dense layer called cap rock
    • Condition 2: In a formation rich in void spaces called a reservoir rock where oil and natural gas are prone to accumulate


How oil and natural gas are formed

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