Preparation And Mechanisms Of Ceramic Proppants With Low-density Using Water-based Drilling Cuttings Of Shale Gas

The solid waste named water-based drilling cuttings（WDC）,produced from the second oblique section of Shale-gas exploitation.The accumulation of WDC would not only occupy quantity of land,but also cause environmental pollution,that has become one of the major problems in the environmental protection of shale gas exploitation in China.However,ceramide proppants are the key materials for hydraulic fracturing operations and have been widely applied in oil and gas exploration.The major purpose of this study:WDC was used as an additive to replace some bauxite to prepare low-density ceramic proppant which has been widely used to improve the production of oil and gas fields,so as to achieve the safe and environmentally-friendly disposal and comprehensive utilization of WDC.In the projects examnation,firstly,the raw materials,WDC,bauxite and manganese powder as sintering aid,were mixed evenly in different proportions,and sintered at different temperatures to investigate the main properties of proppant.And,the influence of different sintering temperatures,sintering times and raw materials ratio on the properties of proppant were discussed.Furthermore,the microstructure and phase analysis of proppant were analyzed by X-ray diffraction（XRD）and scanning electron microscope（SEM）.Then,two methods of optimizing the amount of WDC were studied by adding iron oxide as sintering aid and treating WDC with aid.Finally,the thermal dynamic analysis of the proppant sintering process was carried out.The main study results were as follows:（1）The different sintering temperatures,sintering times and raw materials ratio had great influence on the main properties of proppant.With the increase of sintering temperature and sintering times,the breakage ratio of proppant sample with the same raw material proportion gradually decreased at first and then increased,while the bulk density and apparent density were just the opposite.And,with the increase of the WDC content,the breakage ratio of the proppant sintered at 1350℃decreased to a minimum firstly and then increased,while the density increased at first and then decreased.Moreover,when adding suitable WDC,the diffraction peak of mullite phase increased and the grains size of mullite became larger.The network skeleton structure formed by the mutual interweave between mullite grains and the corundum grains improved the strength of proppant significantly.Furthermore,when 40g WDC,160g bauxite and 8g manganese powder were added into,the proppant prepared by sintering at 1350℃presented the optimum performance with 1.47g/cm³ of bulk density,2.67g/cm³ of apparent density and only 4.02%of breakage ratio under 52MPa,which could meet the standards of petroleum and gas industry in the Measurement of Properties of Proppants Used in Hydraulic Fracturing and Gravel-packing Operations（SY/T 5108-2014）.（2）With the increase of the Fe₂O₃ content and the amount of aid using to treat WDC,the breakage ratio of the ceramsite proppant sintered at 1420℃decreased at first and then increased,while the density increased firstly and then decreased.When140g bauxite,60g WDC treated with 100ml hydrochloric acid of 1:1,8g manganese powder and 4g iron oxide were added into,the proppant prepared by sintering 2.0hours under 1420℃presented the optimum performance with 5.43%of acid solubility,4.02%of breakage ratio under 52MPa,1.51g/cm³ of bulk density and 2.77g/cm³ of apparent density,which could meet the standards（SY/T 5108-2014）.It was shown that these two methods had achieved the goal of optimizing the amount of WDC,which increased from 20 percent to 30 percent.（3）The crystal phase reaction of ceramic proppants prepared by WDC was a first order kinetics reaction.And the correlation coefficient R² of sample Z-12 was 0.9976.The correlation of linear equations obtained by the Coats-Redfern integral method was very good.And with the increase of the WDC content,the activation energy of the crystal phase reaction decreased firstly and then increased.When 40g WDC were added into,the activation energy of sample Z-11 decreased to a minimum of52.22kJ/mol.As the amount of acid treatment increases,the activation energy showed an increasing trend.