Development and Study on a High Temperature Salt Resistant Filter Loss Reducer for Well Cementing

A high temperature salt resistant zwitterionic filter loss reducer DRF-4L has been developed to deal with problems encountered in filtration control of drilling fluids, such as poor resistance to high temperature, poor resistance to high salinity, viscosifying the mud at low temperatures as well as severe thinning at high temperatures. DRF-4L has special cationic groups in its molecules and is synthesized through free radical water solution polymerization. The molecular structure and temperature tolerance of DRF-4L were characterized using IR spectroscopy, thermogravimetric analysis and ESEM. The performance of DRF-4L was evaluated. It was found that DRF-4L has wide work temperatures (30-210℃) and excellent filtration control ability. at 210℃ (BHCT), a cement slurry treated with 4% DRF-4L had API filter loss of 42 mL. Saturated salt cement slurries treated with DRF-4L had API filter loss less than 50 mL. Cement slurries treated with DRF-4L do not thicken at low temperatures and only very slightly disperse at elevated temperatures. DRF-4L is very beneficial to improving the initial rheology and to enhancing the high temperature stability of cement slurries. Cement slurries containing DRF-4L has fast developed early strength, the 12 h compressive strength of the set cement at 90℃ is at least 14 MPa, and the late strength of the set cement develops normally. Cement slurries with low density, normal density and high density, or latex cement slurries, if treated with DRF-4L as the major treatment agent, have good overall properties, and are able to satisfy the needs of cementing high temperature deep and ultra-deep wells.