Under the background of "double carbon", energy saving and carbon reduction is the key to the green transformation of offshore oil and gas extraction industry. Taking the offshore oil and gas field development projects in the Bohai Sea as the research object, we established a model of the total cost of electricity and carbon for offshore oil and gas field development, compared and analyzed the carbon emission and economic benefits of green power consumption under the on-shore power mode of four offshore oil and gas field development projects, and elucidated the impacts of the price of green power and the price of carbon trading on the economic benefits. The results show that the total cost of electricity and carbon is negatively correlated with the proportion of green power consumption, green power consumption can reduce carbon emissions by about 80% on average, and the economic benefits of purchasing green power for offshore oil and gas field development projects are more obvious. As the carbon trading market and green power green certificate trading system tends to improve, there will be more room for economic benefits to rise. If we consider the environmental premium of green power consumption increases, green power price increases will have a negative impact on economic efficiency.