Study On Cement Performance Under Low Return-velocity Of Kuche Piedmont Block

Well leakage is often occurred during the cementing due to the complex geologic structure and strait Safety pressure range in the area of the salt layer,block front kuqa mountain,Tarim oilfield.In recent years,there is a new technology,leak-off by low return rate in cementing,to save the problem and full the cementing annulus at one time.The displacement in cementing will be greatly reduced,the return speed and shear rate will be reduced accordingly,which will affect the performance of the cement.However,there is no evaluation method for cement under low return rate.In order to solve this problem,set up a new evaluation method of cement,more suitable for low return rate cementing in block front kuqa mountain base on standard GB/T 19139-19139,and evaluate performance of the cement system which used in salt layer,and analyze mechanism.In order to simulate the heating rate of slurry with different displacement,designed the heating time was 70-140min according to the injection rate and borehole size,in laboratory experimentation.And the shear rate of cement in casing and annulus is simulated at different speeds of thickening instrument.According to the field data,designed 10-150rpm rotating speed to simulate the effect of on the performance of cement slurry with different displacement rate.Selects the experimental pressure is 140MPa and the experimental temperature is 120?160? according to the field data.Exploration The influence of different speed and temperature rise time on stability,temperature resistance,the thickening time and strength development of cement.The experimental results show that the stability of cement under high temperature is improved.With the decrease of the OFITE HTHP Consistometer speed,the thickening time of the cement will be prolonged,the amplitude can reach 220%,the strength of the cement will be reduced,and the average intensity of the 14 days will be reduced to-29%under 160?.The thickening time of the cement will be shortened when the heating time is prolonged,the range can be up to 29%,the cement strength will be accelerated,and the average strength of 14 days will increase by 17%.Through the formulation and conditions of ?177.8mm+182mm tail pipe cementing in Keshen 603,the variation of cement performance in the paper is fully verified.For further study,Pure aksu G grade cement was selected as the research object.selects 50?70 ? for experimental temperature;30?50min as heating up time;selects 150?10rpm as the OFITE HTHP Consistometer speed.The results show that the change trend of pure cement is the same as salt layer cement.It is known that the cement has not produced new hydration products in the induction stage of hydration under low-speed by means of phase analysis and microscopic morphology observation.But there are lower levels of calcium silicate hydrate gel and Ca(OH)2.The cement particles in the induction stage of hydration are more likely to be connected with each other at low speed,and make the shell of hydration products is thickened,the expansion of the shell of hydration products is prolonged,so the hydration process of cement slurry is slowed down.