Research On The Preparation Of Ceramic Proppant With Coal Gangue And Usage In Coalbed Methane Wells

Coalbed methane(CBM)belongs to unconventional natural gas and China has a rich resource reserves that ranks in the third of the world. Currently, the exploitation of CBM tends to ground drilling that need a large amount of proppants in the process of hydraulic fracturing. The CBM wells in Shanxi is within the 2000 m depth, and the proppant used in hydraulic fracturing mainly depends on resin-coated quartz sand, which has the shortcomings of low intensity, sphericity deviation, small varieties and insufficient sources, also the production of quartz sand conflicts to environmental protection policy in China.Compared with oil and shale gas, the proppant used in CBM has a lower closed pressure, namely crushing ratio with less than 10% in 35 MPa closed pressure.Therefore, owing to decrease of technical parameters, it is possible for coal gangue to be used to prepare proppant used in CBM. Preparation process on the proppant was studied and some achievements have been obtained in this paper.The calcination characteristic of gangue from Yangquan was studied. The results show that there are quality and thermal changes in 30?~280??450?~750??1000?~1300?. Combined with XRD and SEM of calcined production of gangue, absorbed water is excluded before 300?; structural water and oxides containing C and S are excluded between 450 ? to 750?; metakaolinite is transformed to Al-Si spinel, mullite and quartz between 1000 ? to 1150 ?;from 1150 ? to 1300 ? large amount of Al-Si spinels are transformed to mullite and quartz. The quality is almost no change, no energy peak valley at1300?~1500?.The calcination characteristic of gangue will provide the theory foundation and sintering system for preparation of ceramic proppant with gangue.Coalbed methane wells fracturing proppant was researched mainly with raw materials of coal gangue and II bauxite. And the effect of additive amount of coal gangue, from 90wt% to 10wt%, and sintering temperature on the performance of ceramic proppant were also studied. The results show thatceramic proppant meets industry standards of coalbed methane wells when additive amount of coal gangue is 50 wt% and sintering temperature is at 1300?. It's the highest bulk density is 1.29 g/cm3 and the lowest crush ratio is 9.76% under 35 MPa closed pressure. When additive amount is 70 wt%, the crush ratio exceeds the industry standard. Therefore, the maximum additive amount of coal gangue is 50 wt% under the experimental conditions in this paper. Based on the above additive amount of coal gangue, the influence of sintering temperature on the properties of ceramic proppant was studied. The results show that main phases of the ceramic proppant are mullite and cristobalite. With increasing sintering temperature, the content of mullite increases gradually and the crystallinity became better. When sintering temperature is above 1350 ?, the sample appears over-burned and mullite phase is wrapped with molten glassy phases. The crush ratio of ceramic proppant decreases first and then increases with the increase of sintering temperature, while bulk density of the ceramic proppant presents an inverse trend. The ceramic proppant sintered at 1250 ?appears the best performances, namely the highest bulk density is 1.31g/cm3 and the lowest crush ratio is 8.13% under 35 MPa closed pressure.