Who's solid or vulnerable on falling oil: Analyst

Weathering the storm of plunging oil prices can be tough for many energy companies. Eric Otto, director of oil exploration and production at CLSA, told CNBC's "Street Signs" on Wednesday that "investors should adopt a defensive stance until the narrative on oil changes."

His stress test of oil at $30 a barrel has produced a clear winner and one that's vulnerable. The top defensive pick was Pioneer Natural Resources because he said it is well-hedged and has a strong balance sheet.

"The earliest that they would need to raise additional capital is the fourth quarter of 2016 so they're sitting pretty well even in the event of a lower oil price environment for an extended period."

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Otto picked Whiting Petroleum as the most vulnerable energy company because "they are largely unhedged and in terms of operations they are a less efficient operator than their peers."