Study On Cementing Material System Suitable For Steam Injection Thermal Recovery Of Heavy Oil

Heavy oil resources account for more than 70%of the world's remaining petroleum resources.Heavy oil production usually uses steam injection.The steam temperature is as high as 350°C.Conventional oil well cement rings often have a decrease in compressive strength at high temperatures.Therefore,the development of a cementitious material system suitable for the strength requirements of heavy oil steam injection thermal recovery wells is of great significance for the safe production of heavy oil and the improvement of the production life of heavy oil wells.On the basis of literature research,the compressive strength of different cementitious material systems at different temperatures was studied experimentally,and the cementitious material systems with resistance to high temperature(350-380°C)strength degradation were optimized.X-ray diffraction and scanning electron microscope were used to analyze the hydration products and microstructures.Combining with theoretical analysis,the composition of hydration products of high temperature resistant cement stone was obtained:C₃A_3.5P₄S₃H₁₈and C₆S₆H.On this basis,the molecular structure design of the silicate-based high-temperature cementitious material system was carried out,and three kinds of composition schemes of the silicate-based high-temperature cementitious material system were designed.The experimental results showed that the silicate-based high-temperature cementitious material system(Jiahua G-grade cement+200 mesh silica sand+0.44 water-solid ratio,in which the calcium-silica ratio of the system was 1.00).At the same time,the high temperature resistant cementitious material system of phosphoaluminate(phosphoaluminate cement+0.4 water cement ratio)was obtained by experiments.Through the optimization of additives,two sets of cement slurry systems suitable for different heavy oil thermal recovery conditions were constructed:Portland-based high temperature resistant cement slurry system and phosphoaluminate high temperature resistant cement slurry system.The experiment of 7 rounds of simulated field steam huff and puff shows that the average compressive strength of silicate-based high temperature cementitious material system is 50.9 MPa from the first round to the seventh round at 350°C,and that of phosphoaluminate high temperature cementitious material system is 18.5 MPa from the second round to the seventh round.Phosphoaluminate cementitious material system is more resistant to acid corrosion.The cured surface is not corroded in hydrochloric acid solution with p H=1,and the compressive strength decreases slightly.The research results have important guidance and application value for the production life of steam soak and combined flooding heavy oil thermal recovery wells.