A booklet distributed to some Oregon schools by NW Natural, titled “Natural Gas: Your Invisible Friend,” has drawn criticism from environmental advocates.Courtesy/Gleb Bahmutov The title seems benign enough: “Natural Gas: Your Invisible Friend.”The cover of the activity book shows the sun peeking over clouds and shining down on a pristine globe, with a fossilized fish skeleton next to a glowing blue flame. The frame of a hydraulic fracking tower rises in the background.Note to readers: if you purchase something through one of our affiliate links we may earn a commission.