Coalbed Methane Production Prediction In Eastern Margin Of The Ordos Basin

Ordos basin is a large coal-accumulating basin. The main coal mine detection is within the buried depth of 500-1000 m. Generally, the coal exploration degree reduces from the margin of the basin to the center.Structural Division in Ordos basin include seven geological units: western margin thrust belts, Tianhuan Depression, YiShan Slope, central paleo-uplift, Jinxi fault-fold belt, Yimeng uplift, Weibei uplift.The Langmuir volume of raw coal in Permo-Carboniferous coal reservoir in the e astern margin of Ordos Basin is generally high and range from 9.66 to 36.66 m3/t, averaged 15.82m3/t.The Langmuir volume of Fugu mining area in the northen of Shan xi and Tongchuan mining area in the south is 9.66m3/t and 19.9m3/t. It is higher in Ha ncheng mining area which is up to 36.66m3/t. The Langmuir volume of coal reservoir in Hedong coalfield in Shanxi ranges from 9.9 to 22 m3/t and it becomes higher from north to south.According to the result of well testing,the reservoir pressure of the Linxing area in Hedong coalfield is between 3.32 and 15.41 Mpa, and the pressure of gradient of this area is between 0.592 and 1.01Mpa/100 m. while the reservoir pressure in Sanjiao area is between 4.12 and 11.47 Mpa, and the pressure gradient is mostly normal and overpressure, where the pressure gradient of No.4+5 coal seam is between 1.04 and 1.24Mpa/100 m, with an average of 1.11Mpa/100 m, the pressure gradient of No.8+9 coal seam is between 0.871 and 1.09Mpa/100 m, with an average of 1.02Mpa/100m; The formation in Shilou area is undercompacted, with a reservoir pressure between 1.579~7.989 Mpa, and the average pressure gradient of No.4+5 and No.8+9 coal seam is 0.59Mpa/100 m and 0.689 Mpa, generally undercompacted.According to the production date and related parameters, the parameter sensitivity analysis has been made. We also did some history matching of wells in Liulin area. Through the adjustment of related parameters,the simulation results matched well to the production date and permeability and porosity have been adjusted. Besides, the optimization of well pattern and well distance is done, finally, a rectangular well pattern and 300×350m well distance is the optimal selection, and productivity prediction of multi seam commingled production is made. The results show that No.3+4+5 coal seam have a good capacity to produce gas, because of the roof aquifer water, while No.8+9+10 coal seam have a high water production rate, however, the gas production rate will be better with the continuous drainage.Useing the asme method, the productivity of other areas in Ordos basin are predicted. The results shows that CBM production potential in Ordos basin is wel.Finally, grey clustering method is used in evaluation of resource potentiality in Ordos basin, and the result shows that Sanjiao, Liulin, Hancheng, Jixian and Shilou have the best resource potentiality.