Chevron Venezuela said it expects to sign an agreement within five weeks to build an $800-million to $900-million aromatics plant in Venezuela. The project will be a 50-50 joint venture between Chevron Venezuela, a unit of San Francisco-based Chevron Corp., and Productos Especiales, or Proesca, a unit of state oil company Petroleos de Venezuela. The plant will process refinery byproducts into commercial petroleum aromatics such as benzene, toluene and xylene. Aromatics are used in chemical or gasoline production. PDVSA executives said a decision could be reached as early as next week, and that Chevron is the most likely partner of three companies under consideration. The other two are Amoco Corp. and Koch Industries International. Chevron shares fell 37.5 cents to close at $66.25 on the NYSE.