| During the cementing construction of oil and gas wells,the cement slurry needs to be pumped from the ground to the underground,which requires the cement slurry to maintain fluidity throughout the pumping process.Therefore,it is necessary to add a fluid loss additive to the cement slurry during cementing construction that can reduce the water loss of the cement slurry system.With the gradual reduction of oil mining output and the great reduction of shallow oil and gas resources that are easy to exploit,oil exploration has gradually developed into marine,complex formations,medium wells,deep wells and ultra deep wells.Therefore,in the process of well cementing operations,the requirements for oil well cement additives are higher.The existing fluid loss control agents can no longer fully meet the current cementing needs of complex formations.Aliphatic sulfonate superplasticizer has been widely used in cementing construction due to its high water reduction rate,improved cement fluidity,wide source of raw materials,and good compatibility.On the basis of the synthesis formula of aliphatic fluid loss reducers,this article uses formaldehyde,acetone,and sulfonating agents as the main raw materials.By adjusting factors such as the ratio of aldehyde to ketone,the amount of sulfonating agent,and the amount of alkali,a high molecular weight aliphatic fluid loss reducer was synthesized through gradual polymerization.The optimal experimental plan was obtained,and a new type of aliphatic fluid loss reducer was prepared.The prepared aliphatic fluid loss additive was analyzed by infrared spectrum,gel permeation chromatography,thermogravimetry,cement slurry performance test,Total organic carbon,Zeta potential and cement filter cake scanning electron microscope.The results showed that all monomers participated in the reaction,and the obtained product was the target product;Mn=2.1×10~4,PDI=4.245 indicates that the molecular weight of the aliphatic fluid loss additive is high and its molecular weight distribution is wide.With the increase of molecular weight,the water loss of the cement slurry system first decreases and then increases;The results of thermogravimetric analysis indicate that the molecular chains of the polymer do not undergo significant decomposition before 330℃,indicating that aliphatic fluid loss agents have good temperature resistance;The results of thermogravimetric analysis indicate that the molecular chains of the polymer do not undergo significant decomposition before330℃,indicating that aliphatic fluid loss agents have good temperature resistance;The temperature and salt resistance of aliphatic fluid loss additive were tested.The test results showed that at 100℃,when the dosage of aliphatic fluid loss additive was10%BWOC,the water loss of the cement slurry system was 84 m L(less than 100m L).In the cement slurry system with 36%salt content,the water loss of the system could still be effectively controlled;By measuring the six speed viscosity of the cement slurry system,it was found that compared with pure water slurry,the addition of aliphatic fluid loss reducing agents can significantly improve the rheological properties of the cement slurry system;Through Total organic carbon analysis,Zeta potential analysis and scanning electron microscope analysis,the mechanism of its action was studied.The results showed that the fluid loss reducer blocked the pores in the cement slurry by adsorbing on the surface of cement particles,making the surface of cement filter cake more compact,thus preventing the free water filtration in the cement slurry system,and achieving the effect of controlling water loss.The prepared aliphatic fluid loss additive was mixed with polyethylene imine to measure its water loss control performance.The results showed that when the dosage of the aliphatic fluid loss additive alone was 8%BWOC,the water loss of the cement slurry system was 104m L.As the dosage of polyethylene imine gradually increased,the water loss of the cement slurry system gradually decreased.When the dosage of polyethylene imine reached 1%BWOC,the water loss decreased to 35m L;The results showed that with the increase of the molecular weight of polyethylene imine,the water loss of the cement slurry system gradually decreased;The Total organic carbon analysis,Zeta potential and particle size analysis,and scanning electron microscope analysis of the compound fluid loss additive showed that the polyethyleneimine formed an uncharged polyelectrolyte complex with larger particle size with aliphatic fluid loss additive,and then blocked the pores of the cement filter cake to form a relatively dense filter cake,thus achieving the effect of water loss control. |
