Preparation And Properties Of Ultra-light Weight And High Strength Fracturing Proppant

Due to social development and environmental pressure,the proportion of the clean energy in China's energy structure will gradually increase,conventional natural gas resources and unconventional natural gas resources such as coalbed methane and shale gas will become the main energy sources in the future.The efficient exploitation of these energy sources is an urgent problem to be solved at present.Hydraulic fracturing technology,as an effective process for increasing oil production and extending oil service during oil extraction,plays an important role in the exploitation of oil and gas wells.Due to the particularity of geological structure and the requirements of environmental protection,ultra-light weight and high strength fracturing proppant has become an urgent need for the development of unconventional natural gas resources such as shale gas and coalbed methane.In this paper,ultra-light weight and high-strength fracturing proppant was prepared by pressureless sintering with the main raw material of bauxite and kaolin clay,respectively,supplemented by the K-feldspar and industrial alumina as raw materials respectively,and the additive was dolomite and V₂O₅,respectively.The effects of the sintering process and additives on the performance of fracturing proppant were systematically studied.The phase composition and microstructure of the proppant were analyzed by X-ray diffraction?XRD?and scanning electron microscopy?SEM?.In addition,the preparation of ultra-light weight fracturing proppant was attempted by using the method of preparing porous ceramic.The conclusion are divided into the following several parts.?1?By adding an appropriate amount of K-feldspar to the raw materials,the content of Al2O3 in the raw materials was reduced,thereby reducing the density of fracturing proppant.The results show that the bulk density and apparent density of the fracturing proppant prepared by adding the K-feldspar are 1.30g/cm3 and 2.61g/cm3 respectively,which is 31.54% and 8.77% lower than that without adding K-feldspar.?2?The addition of dolomite,on the one hand,can reduce the sintering temperature,on the other hand,promoting the growth and development of mullite crystals with forming the liquid phase during the sintering process,thereby improve the strength of the proppant.The optimized proppant sample was sintered at 1330? for 2h with 2wt% dolomite doping,shows a breakage ratio of 4.51% under the closing pressure of 52 MPa.?3?Through the formulation and optimization of the firing system,the ultralight weight and high-strength proppant was prepared in the temperature range of 1300? to 1350? using the bauxite and K-feldspar as raw material and dolomite as the additive.The proppant can meet the SY/T 5108-2014 requirements.?4?V₂O₅ has a significant effect on the growth of mullite whiskers in fracturing proppant,after adding the V₂O₅,the system can form the liquid phase at a lower temperature,which is beneficial to the growth and development of the mullite crystals,and V₂O₅ can promote the directional growth of mullite crystals into needle-like mullite whiskers,the staggered growth of mullite whiskers improves the strength of proppant samples.However,excessive amount of V₂O₅ will increase the liquid phase,which has an adverse effect on the strength of samples.?5?The optimum sintering temperature and the optimum amount of V₂O₅ for the preparation of fracturing proppant were obtained by bending strength test using coal kaolin and industrial alumina as raw materials and V₂O₅ as additives.The results show that the ceramic sample has a optimized strength when the sintering temperature was 1400? and the amount of V₂O₅ was 1wt%,which can up to 66.38 MPa.The proppant,which was prepared under this condition,shows a bulk density of 1.25 g/cm3,an apparent density of 2.68 g/cm3,and a breakage ratio of 5.23% under pressure of 52 MPa,the broken grade reached 7.5K.?6?The density of proppant can be reduced by adding the pore-forming agent,which was always used to prepare the porous ceramic,but also reduce the crushing capacity of the fracturing proppant.