Evaluation of the coupled impact of silicon oxide nanoparticles and low-salinity water on the wettability alteration of Berea sandstones

This study investigated experimentally the coupled effects of hydrophilic SiO_(2) nanoparticles(NPs)and low-salinity water(LSW)on the wettability of synthetic clay-free Berea sandstone.Capillary pressure,interfacial tension(IFT),contact angle,Zeta potential,and dynamic displacement measurements were performed at various NP mass fractions and brine salinities.The U.S.Bureau of Mines(USBM)index was used to quantify the wettability alteration.Furthermore,the NP stability and retention and the effect of enhanced oil recovery by nanofluid were examined.The results showed that LSW immiscible displacement with NPs altered the wettability toward more water wet.With the decreasing brine salinity and increasing NP mass fraction,the IFT and contact angle decreased.The wettability alteration intensified most as the brine salinity decreased to 4000 mg/L and the NP mass fraction increased to 0.075%.Under these conditions,the resulting incremental oil recovery factor was approximately 13 percentage points.When the brine salinity was 4000 mg/L and the NP mass fraction was 0.025%,the retention of NPs caused the minimum damage to permeability.

二氧化硅纳米颗粒与低矿化度水对Berea砂岩润湿性的影响

为了研究亲水SiO_(2)纳米颗粒与低矿化度水对无黏土人造Berea砂岩岩心润湿性的影响,在不同纳米颗粒质量分数和盐水矿化度下开展了毛管压力、界面张力、接触角和Zeta电位测试及动态驱替实验,采用美国矿务局(USBM)润湿性指数量化砂岩润湿性的改变,评估纳米颗粒的稳定性和滞留性及纳米流体提高原油采收率的效果。研究表明,SiO_(2)纳米颗粒与低矿化度水混合驱替可以使砂岩更加水湿。随盐水矿化度降低、纳米颗粒质量分数增加,油水界面张力和接触角均减小;当盐水矿化度降至4000 mg/L,纳米颗粒质量分数增至0.075%时,润湿性改变最为明显,此时原油采收率提高约13个百分点。盐水矿化度为4000 mg/L、SiO_(2)纳米颗粒质量分数为0.025%时,纳米颗粒滞留引发的渗透率伤害最小。

地应力测量精度及其全要素量化表征研究

针对行业现状对地应力测量精度定义及其全要素量化表征方法进行了研究。概述了地应力测量方法、常用试验技术及其测量精度方面存在的问题与原因。从闭环测量角度给出了地应力测量及其精度的定义,在对测量精度研究分类和总结的基础上,提出了地应力测量精度表征体系的构成和分层,指出了测量精度研究的意义、测量方法与测量技术的定义及其测量精度问题。阐述了地应力测量精度全要素量化表征的思路和含义、三维物理模型测量精度试验装置、坐标设定和表征程序,给出了平均方式和最大值方式的表征指标,以及二维和三维测量的精度表征公式,对角度误差的计算方法进行了讨论,对表征方式与技术研发要求的对应关系进行了说明。以早期的USBM孔径变形计和CSIRO空心包体应变计物理模型试验结果的测量精度表征为例,展示了测量精度的量化表征过程,与原有测量精度表征指标进行了对比,获得上述试验技术最大值方式单一指标的总体测量误差分别为10%和27%。首次获得了两试验方法的全要素测量精度数据,比较显示前者的总体测量精度大大优于后者。