Ning Sun,Mingwei Gao,Jiawei Liu,Guang Zhao,Fei Ding,Qing You,Caili Dai
With the increasing demand for oil and gas resources, deep tight oil and gas reservoirs have gradually become the focus of global oil and gas exploration and development. Hydraulic fracturing technology based on water-base fracturing fluid plays a more and more important role in improving the recovery of tight oil reservoirs. Under the background of global CO 2 emission reduction, a CO 2 -responsive clean fracturing fluid with controllable gelling/gel breaking at high temperatures was constructed in this paper. The system was not only friendly to the reservoir and environment, but also overcame the shortcomings of the traditional clean fracturing fluid with undesirable temperature resistance. The viscosity characteristics and viscoelastic behavior of temperature-resistant clean fracturing fluid were investigated through high-temperature rheology experiments. The interaction between fluid and rock was investigated through the core flow experiment. The results showed that the clean fracturing fluid had the characteristics of good CO 2 responsiveness, excellent shear resistance at high temperatures, high drag reduction, satisfactory gel breaking performance, low filtration and low core damage. The complex three-dimensional network structure formed by the intertwined micelles and vesicles improves the temperature resistance of the clean fracturing fluid. It is expected that the fluid can not only be used to improve oil recovery in tight oil reservoirs, but also be used to solve the leakage problem in CO 2 storage underground.
Xiaomeng Wang,Fengfan Zhang,Jian Zhang,Guang Wang,Juan Zhang,Meiqin Lin,Zhaoxia Dong,Zihao Yang
Nanomaterials have great potential as novel materials for enhancing oil recovery in low-permeability reservoirs. Spontaneous aggregation hampers their application effectiveness and may lead to irreversible reservoir damage. In this study, monodisperse crumpled SiO2 nanoparticles (C-SiO2) with central radial pore channels were synthesized by using the spherical micelle self-assembly method. After hydrophobic modification, modified C-SiO2 formed a highly stable nanodispersion with the assistance of sodium dodecyl sulfate and octadecanol. Results showed that C-SiO2 exhibited reduced external surface area, increased active sites, and excellent dispersibility. The C-SiO2 dispersion demonstrated excellent temperature tolerance (90 °C) and salt resistance (20000 mg/L, including 4000 mg/L Ca2+), outstanding enhanced oil recovery performance, and negligible reservoir damage. Injecting 0.5 pore volume of the C-SiO2 dispersion at a concentration of 0.025 wt % enhanced oil recovery by 14.25%. The C-SiO2 dispersion effectively mobilized residual oil through the combined action of multiple mechanisms. This study provides an effective approach to enhancing the development of low-permeability reservoirs. It also advances the understanding of C-SiO2 synthesis and stable nanodispersion design, which is crucial for future oil recovery applications.
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