Synthesis and Properties of a New High-Temperature and Salt-Resistant Fluid Loss Additive LX-1

To address the problems of current fluid loss additives like low temperature resistance, low salt resistance, narrow application range, and poor compatibility with other cement additives, a new copolymer-type fluid loss additive, i.e., LX-1, was prepared.LX-1 was produced using 2-acrylamido-2-methylpropane sulfonic acid, N, N-dimethylacrylamide, and itaconic acid as the main monomers, and a new type of long-chain hydroxyl-containing compound via radical polymerization. The copolymer was characterized by infrared spectroscopy and thermal weight loss analysis. Results show that the monomers successfully participate in polymerization, and the polymerization product is the target product. The fluid loss additive has good heat resistance and a wide temperature range (30-210℃).The performance evaluation test of the cement slurry shows that, at 150℃, 4% LX-1 can control the API fluid loss of the cement slurry within 50mL, and at 210℃, 6% LX-1 can control the API fluid loss of the cement slurry within 100mL.Moreover, the salt resistance of the cement slurry is excellent. At 90℃, 4% LX-1can control the API fluid loss of the semi-saturated brine cement slurry system to less than 100mL, and 5% LX-1can control the API fluid loss of the saturated brine cement slurry system to less than 100mL.The rheological properties of the cement slurry are good. The fluidity of the cement slurry with 3% LX-1 at room temperature is 24.3cm; compared with that of pure slurry (i.e., 19.0cm), the fluidity of the cement slurry is increased by 27.9%.The fluidity of the slurry decreases from 24.3cm to 21.0cm, a reduction of 13.4%.By contrast, the fluidity of the slurry decreases from 19.0cm to 11.5cm, a reduction of 39.5%.Thus, the fluidity of the cement slurry system is good. In addition, the strength of cement stone containing LX-1develops rapidly;its 1-day compressive strength is 27MPa at 90℃.Subsequently, its compressive strength develops normally. Thus, it has good compatibility with other additives. The chemical curve does not exhibit the "bulging"and"core-covering"phenomena. Therefore, the cement slurry system has high stability and good application prospects. © 2021, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.