梳型聚羧酸减阻剂的室内研究

Laboratory Study on Comb-like Polycarboxylic Acid Friction Reducer

针对高压盐水层、大段盐膏层及海上作业直接采用海水配浆固井时,现有减阻剂分散能力差、分散保持性差、缓凝性强的缺点,采用自由基聚合方式开发了具有梳型结构的聚羧酸减阻剂。通过红外光谱、电镜分析和热重分析测定了减阻剂的结构和耐热性,根据行业标准测定了减阻剂加入对水泥浆流变性、稠化性能和强度的影响,并进行了对高密度水泥浆的适应性研究。热重分析结果表明,该减阻剂耐温可达233℃。扫描电镜与原子力显微镜测试表明该减阻剂呈梳型。该减阻剂对水泥浆分散能力强,对饱和盐水和海水配浆体系具有良好的分散作用,缓凝性弱,且不破坏强度,可用海水直接配浆。加入该减阻剂后密度为2.72 g/cm3的水泥浆体系失水量为24 m L,24 h强度为22 MPa,90℃稳定性及流变性好。其对饱和盐水体系良好的分散效果及对高密度水泥浆体系良好的适应性表明,梳型聚羧酸减阻剂是一种高效减阻剂。

Cementing slurries formulated with seawater are generally used in cementing the wells penetrating high pressure saltwater zones, long salt/gypsum formations, or wells drilled offshore. Friction reducers commonly used are diffcult to disperse in the seawater cementing slurries, and have short dispersion duration and strong retarding performance. A polycarboxylic acid friction reducer with comb-like molecular structure has recently been developed to overcome these problems. The friction reducer was synthesized through free-radical polymerization, and was studied for its molecular structure and thermal stability using IR, SEM and thermogravimetric analysis. The effects of the friction reducer on the rheology, thickening performance and strength of cement slurries were measured in accordance with relevant industrial standards. The adaptability of the friction reducer to cement slurry was also studied. Thermogravimetric analysis showed that the friction reducer was stable at temperatures as high as 233 ℃. SEM and atomic force microscope measurement demonstrated that the friction reducer had comb-like molecular structure. This friction reducer was highly dispersible in cement slurries formulated with saturated saltwater or seawater, and had weak retarding power. It didn’t deteriorate the strength of the cement slurries which were formulated directly from seawater.A cement slurry treated with the friction reducer had density of 2.72 g/cm3, flter loss of 24 mL, 24 h strength of 22 MPa, and good stability and rheology at 90 . Good dispersity in saturated saltwater and good adaptability to high density cement slurry indicated that the comb-like polycarboxylic acid friction reducer was of high effciency.