Russian researchers say they have detected a large spill in Kazakhstan’s Kashagan oil field covering at least seven square kilometers. But the entity that operates rigs in the area denies a spill has occurred. The researchers, working on a project called Transparent World of the Caspian Sea, published a satellite image of the area on their Telegram channel, describing a black spot shown as an oil “slick of anthropogenic origin.” The group’s experts suggested that a production mishap could be the cause. Another theory circulating attributes the spill to accidental discharge of production water …