Part 1 Oil and gas industry segments

exploration and production (E&P) because it encompasses activities related to

searching for, recovering, and producing crude oil and natural gas.

   Licensing

Exploration

  Appraisal

  Development         Production         Abandonment

Negotiation with Government or with the owner of the territory

Activities to search for oil and gas deposits on the certain location beneath the earth surface

Activities to define the oil and gas volume and characteristic more precisely after discovery

Activities to build the subsurface and surface facilities to produce oil&gas safely and efficiently

Activities to extract hydrocarbons to the surface and process them

Activities to plug wells and remove surface facilities

shale
oil sands
tight oil

gas through a network of pipelines, trucks, rail, ships, tankers

and barges to the downstream sector.

Storage
oil is stored in tanks
gas is stored underground

Transportation
marine vessels
railroads
trucks

Gathering
Field processing
Fractionation

and purifying natural gas as well as the marketing and

distribution of products derived from them.

Refining & purifying
refineries convert crude oil into variety of products (gasoline, diesel, asphalt, jet fuel, plastics, lubricants and etc.)

Retail
provision thousands of products to the end-user customers around the globe

oil is oil in its natural state before it has

been processed or refined.
Natural gas (also called fossil gas) is a naturally occurring hydrocarbon gas mixture consisting primarily of methane.

and geophysical surveys on the features of interest (known as leads)
Once a lead

has been identified, geophysicists will conduct more detailed mapping over it using energy or seismic waves.
Finally, when a prospect (a lead which has been evaluated and is ready to drill) has been identified and evaluated  an exploration well is drilled in an attempt to conclusively determine the presence or absence of oil and gas. 

       Well logging     

of the variations in the pull of gravity from the

rocks in the upper layers of the earth`s surface. Denser rocks have greater gravitational attraction than less dense rocks. For example, a structural uplift of denser rocks will appear as an anomaly on the gravity map.
Gravity surveys for hydrocarbons are carried out on land, in the air on helicopters, and at sea on ships.

the earth`s gravitational field, whereas magnetic bodies frequently owe their

magnetization to the magnetic field of the earth. For this reason, magnetic anomalies are often subject to change with latitude.

Magnetic method
The magnetic method is the oldest geophysical method, and is based on the measurement of variations in the magnetic field due to changes of structure or magnetic susceptibility of the rocks. 

Today magnetic surveys for hydrocarbon
exploration are usually carried out from the 
air or from a ship.

magnetic "susceptibility" and "remanent magnetism". 

Rocks and formations fall into two

natural groups:
Igneous rocks and iron ores which are strongly
magnetic
sedimentary rocks, which are generally weak in
magnetization

Sedimentary rocks generally have a smaller
susceptibility than igneous or metamorphic 
rocks , so an interpretation of the recorded
anomalies can yield the maximum depth value for a
sedimentary basin.

a picture of deep rock structures. The idea is to

make artificial rock waves and record how they travel through the Earth. 

REFLECTION SEISMOLOGY
Reflection – when an incident 
compressional wave strikes a boundary between two media having different velocities of wave propagation, part of the energy is reflected from the boundary. 

REFRACTION SEISMOLOGY
Refraction – the portion of the incident energy that is not reflected and is transmitted through the boundary and into the second layer. 

right conditions for an oil trap – the right source

rock, reservoir rock and etc.
Geological mapping is basically a technique which allows a 
graphical presentation of geological observations and interpretations.

Given this collection of information, the geologist can develop a detailed model of the subsurface feature structure and rock composition, and make an educated guess as to the location of potential oil and gas reservoirs.

In fact, most promising areas are already mapped, but 
companies are re-mapping. This work is assigned to geologists, 
whether employed directly by an large companies or under a 
contract from a private firms.

natural gas are based on the premise that hydrocarbons migrate

upward from subsurface petroleum accumulations and produce anomalous patterns near the surface.  
Geochemical method is still in an experimental stage and requires extremely precise analysis technique. 
Geochemical exploration techniques are both direct or indirect. 
Direct techniques require analysis of microquantities of hydrocarbons that occur in the free state in the soil interstices or that are adsorbed on the fine-grained portions of the soil. 
Indirect geochemical methods are based on the detection, in near-surface soils or in vegetation, of inorganic alteration products that result from upward migration of hydrocarbons.