U.S. President Donald Trump’s proposal to double tariffs on steel and aluminum from Turkey could push up costs even further for domestic oil and gas pipeline projects, as energy executives said they were already struggling from earlier tariff rises.  There are more than a dozen U.S. energy pipelines on the drawing board, some of which are still seeking financing. The projects would pave the way for greater U.S. oil and gas exports and relieve a bottleneck in West Texas shale fields that is starting to pinch output in the region. Turkey delivers just 4 percent of steel mill imports, valued about $1.18 billion last year, according to the U.S. Department of Commerce. But […]