Chiapas is rich in petroleum reserves. Oil production began during the 1980s and Chiapas has become the fourth largest producer of crude oil and natural gas among the Mexican states. Many reserves are yet untapped, but between 1984 and 1992, PEMEX drilled nineteen oil wells in the Lacandona Jungle. Currently, petroleum reserves are found in the municipalities of Juárez, Ostuacán, Pichucalco and Reforma in the north of the state with 116 wells accounting for about 6.5% of the country's oil production. It also provides about a quarter of the country's natural gas. This production equals of natural gas and 17,565,000 barrels of oil per year.