Development and Characteristics of a High Temperature Environmentally Friendly Nanocellulose Filter Loss Reducer

Although modified natural polymers such as celluloses have found wide application in drilling fluids, celluloses modified with conventional methods have only limited room for further improvement of their temperature resistance, hence, modified celluloses presently in use can only be used at temperatures below 150 ℃. Borrowing from nano cellulose's excellent characteristics, such as small size, large specific surface area, strong rigidity and high surface activity, a nano cellulose crystalline was developed by hydrolysis of refined cotton with sulfuric acid, and the nano cellulose was in turn made into a nano cellulose filter loss reducer CNCFL-1 through surface functional modification with chloroacetic acid. CNCFL-1 was characterized with degree of substitution measurement, IR spectroscopy and transmission electron microscopy. The comprehensive performance of CNCFL-1 was evaluated measuring its particle size, Zeta potential, rheology, temperature resistance, filtration control capacity and environmental friendliness. The working mechanism of CNCFL-1 was investigated. It was found that the molecules of CNCFL-1 are rich in polar groups such as hydroxyl, carboxyl and sulfonic acid groups, and have degree of substitution of 1.25. The Zeta potential of CNCFL-1 is greater than 30 mV at pH range of 3-13, thus having good dispersion stability. The particle sizes of CNCFL-1 are 50-80 nm. The EC₅₀ value of CNCFL-1 is 31,600 mg/L, and is nontoxic and environmentally friendly. CNCFL-1 performs excellently in controlling high temperature filtration rate through adsorption, viscosifying and tight plugging with its nano sizes. At a concentration of only 1%, the filtration rate of a 4% brine mud can be reduced by 66.92% after hot rolling the mud for 16 h at 160 ℃. Apparently the performance of CNCFL-1 is better than that of PAC-LV and CMC-LV.