Research On The Performance Of Aluminate Cement Stone Used In Heavy Oil Thermal Recovery Conditions

In the case of heavy oil thermal recovery,the high temperature environment of the cement stone is likely to cause cracking of the cement sheath,and the degrading of the strength,which may further cause the failure of the sealing of the cement sheath.From the point of cement matrix materials,this paper employed calcium aluminate cement-based material with good high temperature resistance,and according to the low temperature setting of cementing cement in oil well,the background of working conditions in high temperature environment.The effects of different low temperature curing temperatures on the hydration process of aluminate cement were investigated.The hydration mechanism and mechanical properties of aluminate cement at different temperatures were explained by means of mechanical properties,microstructure,phase composition and hydration heat release rate of cement stone.On the other hand,in view of the strength decline in the low-temperature hydration environment of aluminate cement,this paper explores the mechanism of the influence of slag as supplementary cementing material on the low-temperature hydration performance and high-temperature mechanical properties of aluminate cement stone.At the same time,due to the brittleness of cement-based cementitious materials in high temperature environment,high strength and high toughness basalt fiber and magnesia whiskers were used as cement stone toughening reinforcement materials respectively,and their low temperature mechanics for cement stone was investigated.The effect of high temperature mechanics is enhanced,and the surface of the fiber and whisker is modified by plasma surface treatment to improve the cementation performance between the cement and the reinforced materials.Through the analysis of the mechanical properties,microstructure and thermal analysis of cement stone,the modification mechanism of the reinforcing effect of basalt fiber and magnesia whisker on aluminate cement stone is revealed.The results show that the hydration process,mechanical properties and development of micro-mechanism are different when calcium aluminate cement is hydrated at low temperature of 30?,50?,70? and 90?.Since temperature is an important factor affecting cement hydration,the effect of slag on the hydration process of aluminate cement is different at different hydration temperatures.The compressive strength indicates that the slag has an optimum addition amount in enhancing the hydration of the aluminate cement.Moreover,analysis of the hydration heat of aluminate cement shows that slag can reduce the hydration heat of cement.In the study of the effect of slag on the thermal properties of aluminate cement,the study found that in the low-temperature hydration environment,the thermal conductivity of aluminate cement stone decreases with the increase of slag content,however,the cement stone passes through high temperature.After environmental treatment,the effect of slag on the thermal conductivity of aluminate cement stone first increased and then decreased.This has the same trend as its effect on the compressive strength of cement stone.In the study of using basalt fiber and magnesia whiskers to improve the high temperature toughness and strength of aluminate cement,it is found that both basalt fiber and magnesia whiskers can improve the high temperature toughness of cement stone to varying degrees,and basalt fiber and magnesium oxide crystal When the addition amount is 0.4%and 2.0%,respectively,the effect of high temperature strengthening and toughening of aluminate cement stone is optimal.When the basalt fiber loading is 0.4%,the compressive strength and tensile strength increase from 21.38MPa,0.87MPa to 28.88MPa and 1.52MPa,respectively,and the strength growth rates reach 35.08%and 74.70,respectively.When the amount of magnesium oxide whisker is 2%,the compressive strength and tensile strength increase from 21.3 8MPa,0.87MPa to 30.54MPa and 1.83MPa,respectively,and the strength growth rate reaches 42.84%and 110.34%respectively.In the high temperature environment,the elastic modulus of the modified cement stone sample was reduced to 9650.MPa and 5157.8MPa,respectively,compared with 9932.0MPa of pure cement stone,which was reduced by 3%and 48.07%,respectively.Through the surface treatment of plasma,the surface of fibers and whiskers becomes rougher,and the cementation performance of cement stone is improved.Through the mechanical properties test,the basalt fiber and magnesium oxide whisker after plasma modification are obtained.The reinforcing effect of the mechanical properties of the cement stone is also optimized at the same time.