Upstream (exploration and production), midstream (processing and transportation) and downstream (refining and marketing) operations.

Three component sectors define the global oil and gas industry: upstream, midstream, and downstream:

1. Upstream segment of natural gas business – Exploration and Production (E&P) – The E&P cycle includes exploration, appraisal, development, production and abandonment. This phase includes exploration, development, production and marketing of natural gas. Everything from acquiring the seismic data (acquisition, processing and interpretation thereof), processing other data such as well logs, core analysis, integrating all the data, carrying out appraisals, making reserves estimations and chances of success, making decision as to drill or not to drill exploration well, carrying out drilling with the appropri9ate rig, to the phase of development of the field which includes to safely and economically install the appropriate facilities to produce the hydrocarbons discovered in the field.

2. Midstream segment of natural gas business – This is the link between the exploration and production of natural gas or oil and its consumption by end-users. It consists of natural gas gathering, processing, storage and transportation of Petroleum (crude oil, natural gas, LNG). The transportation is done via the construction and operation of high pressure transmission systems and low pressure distribution networks and/or Liquefied Natural Gas facilities (liquefaction, shipping and regasification). The processing phases includes the process of converting the raw fluids from the wellbore into sales quality hydrocarbons and wastes. The process includes inter alia issues such as separators (separates oil, gas and water): compressors (increases pressure to drive the gas); dehydration (removes water from gas); metering (measures volumes/energy of the gas); slug catcher (entry separator designed to cope with surges of fluids). The Transmission and Distribution (T&D) section includes high pressure transmission system and low pressure distribution network pipelines to supply natural gas to the end consumer

3. Downstream segment of the oil and gas business – refers to the refining of crude oil and the Sale & Marketing of natural gas and products derived from the refining of crude oil to end consumers. The end consumers include mostly the gas fired power generation plants and/or industrial and commercial consumers

Thus we have:
Exploration and production
Processing
Transmission and Distribution
LNG
End-Users