The following companies had unusual price changes in Bogota trading. Stock symbols are in parentheses and prices are as of 4 p.m. local time.

The IGBC Index gained 0.2 percent to 12,529.52, while the Colcap Index rose 0.8 percent to 1,525.05.

Ecopetrol SA (ECOPETL CB), Colombia’s largest oil company, gained 0.7 percent to 4,045 pesos.

Petroleos de Venezuela SA and Ecopetrol are studying a possible joint venture in the heavy crude fields of the Orinoco Belt, Rafael Ramirez, Venezuela’s Oil Minister, said yesterday on state television.

Ramirez, speaking during a signing ceremony in Caracas between Venezuelan President Hugo Chavez and Colombia’s Juan Manuel Santos, said that the two companies will begin with mature oil fields in western Venezuela.

Inversiones Argos SA (INVARGOS CB), parent company of Colombia’s biggest cement maker, rose 3.7 percent, the most in eight months, to 15,800 pesos. Colombia’s October cement sales increased 14 percent from a year ago, the national statistics agency said yesterday on its website.

Inversiones Argos was given a 2012 year-end target price of 23,500 pesos yesterday by brokerage Bolsa y Renta.

The company’s absorption of assets in the spinoff of its Cementos Argos unit has turned it into a “diversified holding” with exposure to Colombia’s infrastructure sector, according to an e-mailed report by analysts including Carlos Eduardo Gonzalez.