Dec 20 (Reuters) - Ecopetrol Sa ECO.CN :
* ECOPETROL EXPANDS ITS PRESENCE IN BRAZIL'S PRE-SALT IN ALLIANCE WITH SHELL AND CHEVRON
* ECOPETROL WILL HOLD A 10% STAKE IN SATURNO BLOCK
* ECOPETROL HOLDS A 10% INTEREST IN BLOCK'S NEW COMPOSITION, WHILE SHELL, OPERATOR, AND CHEVRON EACH HOLD A 45% INTEREST