Research On High Temperature Thixotropic Cement Slurry System

With the continuous development of exploration and development in China,the exploration and development of carbonate gas reservoirs has also show a rapid development trend.Cementing operations in carbonate gas reservoirs have become one of the key points and difficulties in the cementing industry.The cementation pressure stability and leakage prevention of carbonate gas reservoirs are prominent.The thixotropic cement slurry has the characteristics of rapid increase of the gel strength of the slurry in a short time.It is an effective measure to solve such problems,and the current high temperature thixotropic cement slurry There are some shortcomings in the research.To this end,this paper has carried out research on high temperature thixotropic cement slurry system.Through literature research and experimental research,this paper established a method suitable for high temperature evaluation of the thixotropic properties of cement slurry consistency value-added method,and gave the gradation level evaluation standard.A high temperature composite thixotropic agent has been developed with a preferred high temperature thixotropic agent for the purpose of thixotropy at high temperatures.Through experimental research,on the basis of adjusting the strength of high-temperature cement stone,the admixture of high-temperature thixotropic cement slurry is preferred,and a high-temperature thixotropic cement slurry system with excellent performance and meeting construction conditions is constructed.The main performance parameters are:when the amount of xanthan gum is 1.25%,stop the consistency alarm for 30 min;the cement stone 7 d compressive strength is 30.92 MPa;when the retarder is added 2%,the thickening time is 330min;API loss The amount of water is 18 to 47 m L;the permeability is 6.1×10^-6μm².Through XRD and SEM experimental research,the cement hydration products were analyzed,and it was concluded that the addition of the thixotropic agent did not produce new cement hydration products.Based on this,based on the chemical structure characteristics of the thixotropic agent and the existing thixotropic mechanism,the intramolecular and intermolecular interactions of the thixotropic agent and the thixotropic mechanism between the thixotropic agent molecules and the cement particles were obtained.The mechanism of the system for preventing flooding and leakage.According to the relationship between the pump stop time and the pump pressure and the on-site data,the pumping pressure of each formula with different downtime is obtained,and based on the fracture pressure of the formation,the safe shutdown time of different formulas is determined,and the safe downtime of formula 3 is determined.Within 20 min,the safe downtime of Formulation 2 is within 40 min,and there is no construction safety hazard within40 min of Formulation 1 pump stop.