Preparation And Properties Of Ceramic Proppant Based On Coal Gangue

In order to alleviate the pressure on the ecological environment caused by economic and social development,our country is paying more and more attention to the development and utilization of clean energy.While researching and producing new clean environment-friendly new energy sources,it also rejects some solid wastes with secondary recovery value.The efficient recycling of material resources is taken seriously.Hydraulic fracturing technology is a widely used stimulation technology in the oil and gas industry,and the key is the choice of petroleum fracturing proppants.With the development of low osmotic pressure shale gas and other unconventional natural gas,the development of high strength and low density fracturing proppants has received more and more attention.This paper mainly studies the preparation of low-density high-strength fracturing proppant suitable for shallow unconventional oil and gas reservoirs from two aspects.The first is to use low-alcohol raw materials with lower cost and the main waste kaolinite in coal mining.Coal gangue is the main raw material.After adding MgO and MnO₂ as sintering aids,its performance test results and XRD and SEM characterization methods are used to study the influence on the structure and properties of proppant,and also by adding mullite reinforcement method.The enhancement of the performance of ceramic proppant was studied by the formation of mullite.Secondly,by adding a combination of pore-forming agent and sintering aid,the effect of adding pore-forming agent and fluxing agent on the structure and properties of proppant was studied.The ceramic proppant with lower density and strength was also prepared.Through the above experimental research,the main conclusions are as follows:?1?The ratio of raw materials has an important influence on the form and performance of proppant.The use of gangue raw materials or clinker alone cannot guarantee the morphological proppant with good shape and good performance.When the ratio of raw meal to clinker is at 3:7,a better proppant can be obtained at a firing temperature of 1400°C or higher.?2?Adding MgO can significantly reduce the sintering temperature of the c ceramic proppant and promote the formation of a low-viscosity liquid phase.The formation of the liquid phase helps to promote the dissolution of cristobalite,and promotes its reaction with alumina to form mullite.Increase the strength of the proppant.When the addition amount of magnesium oxide is 2 wt%and the calcination temperature is 1300°C,a high strength ceramic proppant with a crushing rate of only 4.96%under a pressure of 35 MPa and a low bulk density and apparent density is prepared.?3?The addition of MnO₂ can reduce the sintering temperature of the proppant,but it is different from the MgO fluxing mechanism.After the addition of MnO₂,the proppant is ejected during the sintering process at a higher temperature,leaving the excess metal Mn⁴⁺,while the metal Mn⁴⁺ion lacking the oxygen atom in the crystal lattice is very active,and its nucleating ability is very strong,which makes it become The activation center,which promotes the solid phase reaction between the kaolinite and the additive in the matrix,advances the mullite process.On the other hand,the ionic radius of Mn⁴⁺and the ionic radius of Al³⁺are very close,which makes manganese dioxide infinitely solid solution with alumina to form a solid solution,and Mn⁴⁺undergoes a reduction reaction during high-temperature sintering,resulting in its ionic radius.A change occurs,which in turn causes the lattice of the alumina to mutate,lowers the sintering temperature of the sample,and promotes sintering.When the addition amount of MnO₂ is 2 wt%and the sintering temperature is1350°C,the prepared ceramic proppant has a breaking rate of only 8.73%under the closing pressure of 35 MPa.?4?Experiments have shown that the addition of mullite powder can also significantly improve the structure and properties of ceramic proppants.The addition of mullite powder on the one hand causes the rod-like mullite to be staggered in the matrix,so that the strength of the proppant becomes high,but on the other hand,the staggered distribution of the rod-shaped mullite increases the porosity inside the proppant.Although it is beneficial to reduce the density of proppant to a certain extent,it is not good for support and strength.When the addition amount of mullite powder is 10 wt%,the strength of the prepared proppant is the highest when the sintering temperature is 1400°C,and the breaking rate under the closing pressure of 35 MPa is only 5.24%,which is supported by the addition of MgO and MnO₂.The optimum breaking rate of the agent is not much different.When the addition amount of the mullite powder exceeds 30 wt%,the strength of the proppant is equivalent to that when it is not added,and the reinforcing effect of the rod-shaped mullite and the weakening effect of the pores almost cancel each other.?5?The addition of the pore former can indeed reduce the density of the proppant and increase the porosity inside the proppant.The results showed that the bulk density of the proppant decreased by 17.12%,15.75%and 15.76%?average value?after adding carbon powder,calcium carbonate and magnesium carbonate.However,within the experimental range,the breaking rate of the ceramic proppant prepared by adding three pore-forming agents did not reach the standard of 9%or less in the industry.On the basis of selecting the carbon powder as a pore former,MgO is added as an additive to improve the strength of the proppant.The experimental results show that when the amount of carbon powder added is 10 wt%,the amount of MgO added is 2 wt%,and the sintering temperature is 1350°C,the best proppant sample is obtained.The bulk density was 1.35 g/cm³,the apparent density was 2.41 g/cm³,and the breaking rate at 35MPa was 4.58%.