The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.NEW YORK ( Trefis) -- Chevron's ( CVX) troubles in Brazil took a turn for the worse as a new sheen was discovered near the Frade fields. The news was followed by a court decision that some of its executives could not leave the country as prosecutors look to file charges against the company as well as some of its top executives for an oil spill in November last year at the same location. The list of executives barred from leaving the country includes George Buck, who heads Chevron Brazil. Production at the field is being shut down after the company put forth plans to stop production at the field to better understand the geology of the field. A few officials of rig operator Transocean ( RIG) have also been barred from leaving Brazil.