水基纳米聚硅在低渗油藏中的降压增注研究

Depressurizing and Injection-augmenting Behavior of Water-based Silica Nanoparticle in Low-permeability Reservoir

纳米聚硅降压增注剂分散在介质中多以聚集态存在,难以进入细小孔道,甚至导致孔道堵塞。本文将一种采用原位表面修饰技术制备的水基纳米聚硅降压增注剂在分散剂作用下分散在水中,利用透射电子显微镜、激光粒度分布仪等分析手段对水基纳米聚硅进行了结构表征,研究了纳米聚硅分散液的相分散、相分离及其砂岩表面的吸附行为,并通过现场试验考察了纳米聚硅分散液的降压增注能力。结果表明:具有强吸附-超疏水核结构的水基纳米聚硅以0.2%的质量分数分散于水中,透光率大于99%,平均粒径为7 nm,Zeta电位达-43.1 mV,分散稳定。同时,分散液在高矿化度及低pH值条件下可实现强吸附-超疏水性核的有效分离,并牢固吸附在岩石孔隙表面,从而改变岩石表面润湿性,形成疏水性孔隙表面。在低渗透油田注水井现场应用时,江苏油田应用7口井平均注水压力下降26.4%,注水量增加106.7%,有效期大于10个月。

The silica nanoparticles used as depressurizing and injection-augmenting agent was mostly dispersed in the medium with aggregate structure,which resulted in it was difficult to be injected into the small pores and even leaded to blockage of the pores. In this paper,a kind of water-based nano-silica with in-situ surface modification was dispersed in water with the action of dispersant, and was characterized by transmission electron microscopy and dynamic light scattering. Their phase dispersion and separation behavior as well as adsorption measurement were studied. Meanwhile,the depressurizing and injection-augmenting ability of the silica nanoparticles dispersion was investigated through field tests. The results indicated that the as-prepared water-based silica nanoparticles exhibited super hydrophobicity and was able to disperse in water as monodisperse particle with a grain size of about 7 nm, as a result,the transmittance of the silica nanoparticles dispersion was greater than 99% and the Zeta potential was -43.1 mV. Besides,the as-prepared super-hydrophobic nano-silica could be well separated from the dispersion system and adsorbed on porous core of wells,which could make the hydrophilicity of the cores transform into hydrophobicity. The as-prepared water-based silica nanoparticle as a depressurizing and injection-augmenting agent could reduce the pressure and increase the injection rate of the reservoir by 26.4% and 106.7%,respectively,and the period of validity was more than 10 months.