PBR - NYSE. Petroleo Brasil SA Petrobras has formed a Darvas box entry at an all time high following a recent volume spike we had in April. The buyers are well in control of this stock as can be seen by the steadily rising OBV. Using the Darvas Trading Method, I would place a buy stop order to purchase the stock if it breaks out of its box, above the 77.61 high. I would place a tight Darvas stoploss just below the box, around 67.50 to protect the position.