环保型改性纳米碳酸钙降滤失剂的合成与性能评价

Synthesis and performance evaluation of environment-friendly modified nano-calcium carbonate filtrate reducer

纳米碳酸钙在钻井液中具有降滤失及封堵作用、且环保,但分散性差、易团聚,导致效果不理想。使用硅烷偶联剂对纳米碳酸钙进行表面改性,再通过自由基共聚法将抗温、抗盐单体接枝到改性纳米碳酸钙表面,得到改性纳米碳酸钙降滤失剂SDNPJ-2,采用红外光谱(FTIR)、热重分析进行表征,同时对比评价其综合性能,通过对膨润土基浆粒径、zeta电位分析,滤饼扫描电镜(SEM)分析,考察SDNPJ-2在黏土颗粒上的吸附特征,研究改性纳米碳酸钙降滤失剂在水基钻井液中的降滤失机制。结果表明:SDNPJ-2可抗230℃高温;1%SDNPJ-2可分别使4%膨润土基浆、25%盐水基浆、10%CaCl_(2)基浆150℃/(16 h)老化后的API滤失量降低70%、89%和85%,可抗氯化钠250000 mg/L、抗氯化钙100000 mg/L,降滤失效果优于国外同类目前最优产品Driscal D;生化需氧量(BOD_(5))为558 mg/L、BOD_(5)/COD(化学需氧量)达22.6%,可生物降解;SDNPJ-2通过酰胺基团吸附于黏土表面、改善其分散性,优化体系粒径级配、通过物理堆积有效封堵滤饼和地层孔隙,两方面协同达到优良的降滤失效果。

Nano calcium carbonate exhibits filtration reduction performance and plugging effect in drilling fluid,and it is environmentally friendly.But it has poor dispersion and is easy to agglomerate,resulting in unsatisfactory results.In this paper,the surface of nano calcium carbonate was modified by silane coupling agent,and then the monomers with temperature and salt resistant performance were grafted onto the surface of modified particle by free radical copolymerization to obtain modified nano-calcium carbonate fluid loss reducer SDNPJ-2.It was characterized by infrared spectroscopy(FTIR)and thermogravimetric analysis,and the comprehensive properties were compared and evaluated.In addition,the adsorption characteristics of SDNPJ-2 on clay particles were investigated by particle size of bentonite base mud,Zeta potential analysis,scanning electron microscopy(SEM)analysis of clay and the measurement of the adsorption capacity of clay particles further reveal the mechanisms modified nano-calcium carbonate fluid loss reducer in water base drilling fluids.The results show that SDNPJ-2 can resist high temperature of 230℃.After aging at 150℃/(16 h),adding 1%SDNPJ-2 can make 4%bentonite base slurry,25%brine base slurry,and 10%CaCl_(2) base slurry API fluid loss decreased by 70%,89%and 85%,respectively.It can resist 250000 mg/L of sodium chloride and 100000 mg/L of calcium chloride.The filtration reduction effect is better than that of the same kind of foreign product Driscal D.The BOD_(5) value is 558 mg/L,and the ratio of BOD_(5)/COD is 22.6%,which is biodegradable.SDNPJ-2 is adsorbed on the clay surface through amide groups to improve its dispersion,optimize the particle size grading of the system,and effectively block the filter cake and formation pores through physical accumulation.The two aspects work together achieve excellent filtration reduction effect.