This paper presents a comprehensive process synthesis superstructure toward the production of C-2 to C-4 olefins from natural gas via the methanol intermediate. The superstructure of alternatives includes multiple natural gas conversion pathways, multiple methanol conversion technologies, and an extensive olefin purification section. Simultaneous heat, power, and water integration is incorporated for the optimal utility usage within the refinery. A branch-and-bound global optimization framework approach is utilized to guarantee the global optimality. The profit of the proposed refinery is maximized across different scales and price levels. The optimal topology consistently includes the methanol-to-olefins, MTO, technology due to its high selectivity into high value olefins. The proposed refinery can be significantly profitable even under undesired price scenarios (June 2015 prices). The proposed plants yield positive net present values for scales above 500 MT/day, regardless of the price level investigated. Increasing the plant scale significantly increases the plant profitability and the net present value due to economies of scale. The results suggest that the proposed natural gas to olefins, GTO, refineries are economically viable without increasing the greenhouse gas emissions compared to typical fossil-fuel based processes.