For the vast majority of simulation cases a billion cells is several orders of magnitude larger than is commonly used. At this “hero-scale” the main goal is to stress-test simulators and to show off capability. Typical reservoir models used in the industry range in size from a few hundred thousand to a few million cells. If we think of one of these models as a standard definition HDTV, then the billion-cell example would have 250 times the resolution of a 4K television. It gives enormous resolution and clarity, but comes with high computational cost. The purpose of our billion-cell calculation was to highlight ECHELON’s capabilities and the efficiencies that GPU computing offers. With help from colleagues at iReservoir, we created a model using publicly available log data collected from a large Middle East carbonate field. We built a three-phase model with 1.01 billion cells and 1,056 wells.