化学交联聚乙烯醇的降滤失机理  

Mechanisms Involved in Fluid Loss Control of Oilwell Cement Slurries by Chemically Crosslinked Polyvinyl Alcohol

作　　者：陈涓[1] 彭朴[1] 汪燮卿[1] 

机构地区：[1]中国石化石油化工科学研究院,北京100083

出　　处：《油田化学》2002年第2期101-104,117,共5页Oilfield Chemistry

摘　　要：所研究的化学交联聚乙烯醇 (PVA) ,为PVA与形成共价键的交联剂在 5 0℃、后期 pH值 <5的条件下在水溶液中反应生成的 ,相对分子质量 3.5× 10 5～ 6 .5× 10 5,含有少量杀菌剂和稳定剂。对照化学剂为一种络合交联的PVC ,或称混合交联PVA ,即与水泥干混的PVC加硼酸钠。实验研究结果表明 :加入 0 .4% (BWOC)化学交联PVA可使G级油井水泥浆 10～ 10 0℃的API滤失量降至 5 0mL以下 ,加量增至 0 .6 %时 12 0℃滤失量为 5 4mL ,抗盐 (NaCl)能力可达 80 g/L(75℃数据 ) ,均远优于混合交联PVA ;加入化学交联PVA的水泥浆 ,1分钟滤失量占 30分钟滤失量的 6 0 %以上 ;加量 0 .1%～ 0 .15 %区间滤失量急速下降 ,加量继续增加时滤失量不再明显下降 ;化学交联PVC在水泥颗粒表面的等温吸附符合Langmuir单分子层吸附模型 ;基于达西定律考察滤失量与滤液粘度之间的关系 ,发现化学交联PVA降低滤失量的主要因素不是增粘作用 ,而是滤饼渗透率降低 ,在滤饼下面、过滤介质表面形成一层有一定韧性的完整致密聚合物膜 ,此膜在升温至 12 0℃时仍稳定不变 ,滤失量不显著增大 ,而混合交联PVA形成的膜 ,接近 10 0℃时开始破坏 。The chemically crosslinked polyvinyl alcohol (CCPVA) studied is prepared by crosslinking PVA in aqueous solution at 50℃ and pH<5 (at later stage )through covalent bonds and contains bactericide and stabilizer. Molar mass 3.5×10 5-6.5×10 5. A complex-crosslinked PVA, PVA and sodium borate (SB) premixed with cement, is taken as control. It is shown that for the grade G oilwell cement slurries treated by 0.4% (BWOC) CCPVA, the API filtrate loss (FL) is well below 50 mL at 10-100℃ (and is of 57 mL at 120℃ when 0.6% CCPVA added), the tolerancy to NaCl reaches 80 g/L on the date at 75℃ and these characteristics are much worse for the slurries treated by PVA+SB. The FL value of CCPVA-treated slurries in 1 min accounts more than 60% of whole FL in 30 min, the FL of slurries dramatically lowers when 0.1-0.15% CCPVA added and does not decreases when additional CCPVA introduced. The adsorption isotherm of CCPVA-treated slurries onto cement particles is fit for Langmuir's model of monomolecular layer adsorption. The relationship between FL amount and filtrate viscosity (Darcy's law) shows that main factors in FL reduction by CCPVA is not viscosifying effect but reduction in filter cake permeability: a tough, monolithic and compact polymer film is formed on the filter membrane surface under the filter cake and kept stable on heating up to 120℃ so that the FL is not increased notably meanwhile the film formed with PVA+SB starts to destroy near 100℃ and this results in abrupt increase of FL.

关 键 词：交联聚乙烯醇 降滤失剂 油井水泥浆 水泥外加剂 作用机理 成膜作用 

分 类 号：TE256.6[石油与天然气工程—油气井工程]