Study Of High Activity And Low Density Cement Slurry System

Low density cement is widely used in the cementing construction of long sealing and solid section of low-pressure easy leakage layer and low-pressure oil and gas layer to balance the formation pressure and prevent well leakage.However,the low-density cement system has the defects of low early strength and slow strength formation at low temperature,which leads to gas channeling in the early stage of cementing with low-density cement slurry,which seriously affects the cementing quality and the sealing integrity of cement sheath.It is necessary to develop a high early strength and low-density cement slurry system at low temperature.In this paper,based on superfine cement and slag,a high activity reinforcing material drg-1s with wide temperature applicability is developed,and the proportion of each solid material is designed by using the close packing linear model to form a set of high activity and low density cement slurry system with high early strength and fast strength generation.The research conclusions are as follows:(1)A new type of high activity reinforced material DRG-1S was successfully compounded by grinding superfine cement and slag,and proportioning.The reinforced material has remarkable effect on improving the activity of cement system,and has strong temperature applicability.It can play its excellent activity improvement effect in the range of 60～150°C.(2)A set of high activity low density cement slurry system was successfully prepared by using reinforcement material DRG-1S,reducing material Y12000 glass beads,etc.,combined with the proportion design of tightly packed raw materials.The suitable density range of the system is 1.23～1.50 g/cm~3,and the suitable temperature range is 60～150°C.(3)The thickening time and compressive strength of the high activity low density cement slurry system were evaluated.The results show that the compressive strength can reach 8.8 Mpa,14.8 Mpa and 27.8 Mpa respectively after curing 1 d,2 d and 7 d.The thickening time is 210 min and the strength generation time is 280 min under 60°C and 21 Mpa.Compared with the formula using ordinary reinforced materials,the thickening time remains unchanged,the strength increases by about 45%,and the strength generation time is shortened by nearly half.Through the evaluation and test of the micro morphology of high-activity low-density cement slurry/stone,the mechanism of improving the early strength of low-density cement system is comprehensively analyzed,that is,by using high-performance materials and close packing design method to improve the reaction activity of cement system,accelerate the early reaction rate,promote the secondary pozzolanic effect,consume low-strength calcium hydroxide,improve the formation of high-strength C-S-H,and achieve the effect of early strength and high strength.(4)The high activity low density cement slurry system has been successfully applied to Banan 001-H1 well and Zhongjiang 2 well,and the qualified rate of cementing quality is more than 95%,which meets the cementing requirements.