Oil pump jacks are seen next to a strawberry field in Oxnard, California February 24, 2015. U.S. oil producers pounced on this month’s 20 percent rally in crude futures to the highest level since November, locking in better prices for their oil by selling future output and securing an additional lifeline for the years-long downturn. The flurry of dealing kicked off when prices pierced $45 per barrel earlier in April. It picked up in recent weeks, allowing producers to continue to pump crude even if prices crash anew. While it was not clear if oil prices will remain at current levels, it may also be a sign producers are preparing to add rigs and ramp up output. This week, Pioneer Natural Resources Co ( PXD.N ), a major producer in the Permian shale basin of West Texas, said it would add rigs with oil prices above $50 per barrel. […]