Shares in President Energy fell sharply on Monday despite a positive update from the group on its Lapacho well in the Chaco region of Paraguay.The company said that while it was too early to say that it had struck oil, there was encouraging evidence that it would be able to do so in the future.President previously announced that a light oil/condensate discovery had been made higher up the well in the Icla formation and that drilling would continue to penetrate the main Santa Rosa target.The group said it has seen evidence of "constant background gas ranging from 3% to over 12%" and that it plans to drill to the base of the Santa Rosa formation to a depth of 4,600m to fully evaluate the target section.Due to the extended drilling period, President pledged to update on further progress towards early December.Shares had dropped 19.7% to 27.90p by 13:42.