Methods, systems and devices that utilize a mobile offshore drilling unit (MODU) with other integrated equipment, hereinafter a mobile offshore production unit (MOPU) or a traditional floating production unit (FPU) to produce oil and natural gas from an oil and gas containing subsea geological formation are described. When the MOPU/FPU consumes all produced natural gas in one or more processes onsite to produce products selected from power, liquid petroleum products, hydrogen gas, solid carbon, and combinations thereof, then the production unit is transformed into a Modular MOPU-. Some produced natural gas is used to generate electricity for normal facility operations and additional natural gas consumed to generate electricity for various 4th-phase processes or used as feedstock for the production of value added products in processing equipment such as pyrolysis units, and/or gas-to-liquids units. Maximizing consumption of produced natural gas onsite, optimizes oil production without flaring, and without any export pipelines.