Numerical simulation of coal measure gases co-production

The co-production of coalbed methane,tight gas and shale gas(“Three gases”) from one well bore is an ef- fective method to improve the productivity of single well and utilization rate of underground resources. However,the gas and water production process under geological conditions,especially the contribution rate from different layers,gas pro- duction pressure and gas saturation variation are not clear. In this paper,a numerical model of coalbed methane and tight sand gas co-production was established for the first time. Combined with the geological parameters and gas-water output curve of the test well,the factors controlling the gas production were identified. The results show that that the applicability of the co-production model can be compared with single production models,which shows a good suitabili- ty;the model can achieve the purpose of production rate classification and the contribution of different layers can be classified;the pressure drop rate decreases,the later of the gas production peak come,however,the production rates in late stages show no much difference;the similar of the sandstone and coal pressure systems,the better of the co-pro- duction effect;improving the hydro fracturing results can improve the gas production rate in short term,but show little influence on the accumulated gas production;the effect of shrinkage and stress sensitivity of the coals can significantly improve the gas production effect,however,the physical properties of the coal seam under deep geological conditions need to be further explored. The related results would provide a guidance for the formulation and improvement of drain- age systems of coal measure gases and promote “three gases” co-production from one wellbore a step further.