Resumen
In China there has been considerable discussion of how one should express the efficiency of energy conversion and production. Energy return on investment (EROI) can be useful for this because its methodology is based on outputs and inputs. Unfortunately, similar to the rest of the world, most of the data available for assessing energy gains and costs for oil and gas in China has to be derived from economic costs and revenues for oil fields. In this paper we derive a first EROI for China based on using this approach and the existing data for production of crude oil and natural gas for the Daqing oil field, the largest oil field in China. We estimate that its EROIstnd expressed as heat equivalent was 10:1 in 2001 but has declined to 6.5:1 in 2009. Based on this trend we project that the EROIstnd will decline to 4.7:1 in 2015, and the net energy from the field will be decreasing substantially. The calculations have some errors because of incomplete data, and if various externalities are taken into account, the EROI of this oil field would be lower than our present estimates. The trends of EROI and net energy suggest that the Daqing oil field will face more difficulty in the future which can not be overcome by government fiat.