Synthesis And Performance Of A New High-Temperature And Salt-Resistant Fluid Loss Additive

With the decreasing of shallow oil and gas resources,the focus of exploration and development gradually turned to deep wells and ultra-deep wells.Fluid loss additive is one of the main additives,which plays an important role in effectively controlling the water loss of cement slurry,ensuring construction safety and cementing quality.At present,most of the fluid loss additive products used at home and abroad are acrylamides.The amide groups contained in this type of fluid loss additive can easily hydrolyze and desorb under the environment of high temperature and strong alkali,resulting in the water loss of cement slurry uncontrollable,which in turn leads to problems such as poor high temperature and salt resistance of the fluid loss additive,narrow application range,and poor compatibility with other cement additives.In view of the above problems of fluid loss additives and on the basis of the previous work of this research group,the molecular structure of the copolymer was designed,and the compounds(2-acrylamido-2-methylpropanesulfonic acid,Kang acid and N,N-dimethylacrylamide)are the main synthetic monomers,the new long side chain hydroxyl-containing compound-sodium allyloxy hydroxypropyl sulfonate is introduced,and the fluid loss is prepared by free radical polymerization.Through detailed investigation of the various reaction conditions of the synthetic copolymer,the best experimental scheme was selected,and the high temperature and salt resistance fluid loss additive LX-1 was prepared.Infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy analysis and characterization of the fluid loss additive LX-1 showed that all four monomers successfully participated in the polymerization reaction,and the resulting product was the target product.The molecular weight size and molecular weight distribution range of the fluid loss additive were analyzed by gel permeation chromatography.The test results were:Mn=2.9×10~4,PDI=10.603.The result showed that the fluid loss additive LX-1 had a moderate molecular weight and a wide molecular weight distribution.Through thermogravimetric test characterization of the fluid loss additive LX-1,its thermal stability was evaluated.The results show that the fluid loss additive LX-1 will not degrade significantly before 286?,the polymer has excellent temperature resistance.The application performance of the cement slurry of fluid loss additive LX-1 was evaluated,and the test results showed that the static API filtration loss of fresh water cement slurry with 3%fluid loss additive LX-1 content at 90?was 34m L.The temperature application range of the fluid loss additive LX-1 is wide,and it has a good ability to control the water loss in the temperature range of 30?210?.The fluid loss additive LX-1 has excellent salt resistance.Adding an appropriate amount of fluid loss additive LX-1 to the cement slurry in semi-saturated brine and saturated brine can effectively control the amount of fluid loss in the system.The cement slurry added with fluid loss additive LX-1 has excellent rheological properties,which can greatly increase the fluidity and fluidity retention of the cement slurry and effectively improve the rheological properties of the cement slurry.The fluid loss additive LX-1 has a slight effect on the compressive strength of cement stone in the early stage,and the compressive strength in the later stage develops normally.The thickening curve of fluid loss additive LX-1 is stable,and there is no phenomenon of"core"and"bulging".The system has high stability and good application prospects.