Mexican Petroleum, also known as Petroleos Mexicanos or Pemex, is a Mexico-based company engaged in the exploration and processing of oil and gas, as well as hydrocarbons. Pemex's operations are categorized into four segments: Exploration and Production (E&P), Refining, Gas and Basic Petrochemicals and Pemex Petrochemicals. The E&P unit explores for and produces crude oil and natural gas. Its Refining unit converts crude oil into oil-bearing products and derivatives, and is engaged in the marketing and distribution of these products. The Gas and Basic Petrochemicals segment is responsible for processing of natural gas and its liquids, as well as for transportation, commercialization and storage of gas by-products. The Pemex Petrochemicals unit elaborates, commercializes and distributes petrochemical products, such as methane and ethane derivatives, aromatics and their derivatives, propylene and its derivatives, as well as oxygen and nitrogen.