Method for predicting economic peak yield for a single well of coalbed methane

The development of coalbed methane (CBM) in China poses great difficulties because of high investments, low produc- tion and high risks. So a study of the economic effect of a single well at its preliminary stage is helpful for commercial exploitation of CBM. Affected by wellbore flow pressure, initial reservoir pressure, relative permeability, Langmuir pressure and other factors, the trend of declining production of a single CBM well agrees, by and large, with a hyperbolic pattern of decline. Based on Arps’s equation, nearly 200 wells production with different peak yields and initial rates of were simulated. Given the present cost of drill- ing, gas production and engineering on the ground, the gross investment for the development of a single coalbed methane well was estimated for the Fanzhuang block in central China. Considering the current industrial policies for CBM, we established an eco- nomic assessment model and analyzed economic peaks. The results show the economic benefits with or without government subsi- dies at different peak yields of a single CBM well. The results of the evaluation can be directly applied in the Fanzhuang block. The evaluation method, formulated in our study, can be used to other areas with similar conditions.

A review of physical supply and EROI of fossil fuels in China

This paper reviews China’s future fossil fuel supply from the perspectives of physical output and net energy output. Comprehensive analyses of physical output of fossil fuels suggest that China’s total oil production will likely reach its peak, at about 230 Mt/year(or 9.6 EJ/year),in 2018; its total gas production will peak at around350 Bcm/year(or 13.6 EJ/year) in 2040, while coal production will peak at about 4400 Mt/year(or 91.9 EJ/year)around 2020 or so. In terms of the forecast production of these fuels, there are significant differences among current studies. These differences can be mainly explained by different ultimately recoverable resources assumptions, the nature of the models used, and differences in the historical production data. Due to the future constraints on fossil fuels production, a large gap is projected to grow between domestic supply and demand, which will need to be met by increasing imports. Net energy analyses show that both coal and oil and gas production show a steady declining trend of EROI(energy return on investment) due to the depletion of shallow-buried coal resources and conventional oil and gas resources, which is generally consistent with the approaching peaks of physical production of fossil fuels. The peaks of fossil fuels production, coupled with the decline in EROI ratios, are likely to challenge the sustainable development of Chinese society unless new abundant energy resources with high EROI values can be found.