In Oregon, developers believe they’ve made a major breakthrough that solves two problems holding back the next level of geothermal development: creating reservoirs big enough for commercial production and holding down costs. Creating multiple reservoirs from a single well is key to making it economical, because drilling each well is so expensive, said Nicholas Davatzes, an expert in earth and environmental science at Temple, who helped develop a computer model describing the structure of the rock before it was fractured.