It is crucial to accurately characterize methane absolute adsorption in kerogen nanoporous media for gas-in-place evaluation and well productivity prediction. Assuming that methane forms a single-layer adsorption in kerogen nanopores, a large number of approaches have been reported to convert the experimentally measured excess adsorption to the absolute adsorption. Recently, we have shown that methane adsorption behavior depends on the pore size and may be very different from the single-layer adsorption model, such as the Langmuir model. Thus, it is necessary to explicitly consider the pore size distribution (PSD). While these conversion methods have been extensively used, their validity in the characterization of methane absolute adsorption in nanoporous materials, such as kerogen, has not been systematically assessed. As in our previous work, we used model kerogen with varying PSDs and grand canonical Monte Carlo simulations to model methane adsorption up to 500 bar to assess various commonly used methods converting excess adsorption to absolute adsorption. We find that the predetermined density methods using 373 or 424 kg/m3 may show unphysical phenomena and Langmuir as well as SDR models can largely overestimate the absolute adsorption. On the other hand, the Ono–Kondo (OK) lattice model with PSD can accurately characterize the absolute adsorption in nanoporous media. Interestingly, Langmuir and SDR models coupled with PSD can provide comparable predictions to OK with PSD. In addition, we also suggest to use the high-pressure excess adsorption data (up to 500 bar), instead of the commonly used low-pressure excess adsorption measurements (up to 150 bar). Our work also calls for the accurate characterization of PSD in nanoporous materials to obtain their absolute adsorption capacity.

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Traditional polymer flooding technology is difficult to be used in high temperature and high salinity reservoirs, due to the property limitation of HPAM. It is the key of chemical flooding EOR to develop a new type of polymer, which can tolerate high temperature and high salinity and has high sweeping capacity. Through microemulsion / suspension polymerization technique, a new particle-type polymer is developed. The polymer size is in the range of 30 nm to 112 μm, and can be divided into three size sections: nanometer, micrometer, and submillimeter. The microscope is used to observe the appearance, and the apparent viscosity of the dispersion is also measured, with which the temperature and salinity resistance and water absorbing and expanding property of the new polymer can be evaluated. A 2.1 m long core model is made to test the in-depth migration of the polymer particle. The resistance factor and residual resistance facter evaluation method for traditional polymer is borrowed to test the retention property of the new polymer in cores. Parallel dual-pipe artificial and natual cores are used to simulate the IOR/EOR property of the new polymer for sand and carbonate reservoirs. The lab tests show the new polymer can tolerate high temperature, 120 °C, and high salinity, 200000 mg/L. The polymer particle can swell by 3-10 times in water by hydration, but do not change much in oil. The apparent viscosity of the new polymer liquid is 1-3cp, so it can be easily injected into deep reservoir. It can increase water flowing resistance, but not increase that of oil. When being used, the new polymer is a type of discontinuous liquid distributed with soft polymer particles, which is different from the traditional polymer, HPAM, which is a type of continuous viscous fluid. The IOR/EOR mechanism of the new polymer is different from that of the traditional polymer. As a type of dispersion displacing phase liquid, the new polymer can dynamically modify the permeable ability of different areas, by which the oil and water mobility can be modified effectively, achieving the aim of enhanced oil recovery. The studies preliminarily established the property evaluation method for particle-type polymer, and discovered the IOR/EOR mechanism of the new particle-type polymer. The pilot test conducted in a reservoir with high temperature, 120 °C, and high salinity, 14.9-21.7×104 mg/L, with Ca2+ / Mg2+ concentration of 2500 mg/L, obtained obvious oil rate increase and water cut decrease effect, and achieved technical and economical success.

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The preparation and classification of nanocellulose are briefly introduced, and the modification of nanocellulose and the application of modified nanocellulose in oilfield chemistry are reviewed. The principles and methods of surface modification, including surface adsorption, oxidation, acetylation, silanization, etherification, and polymer grafting, are summarized. Meanwhile, this paper focuses on the application of nanocellulose research progress in drilling fluid, enhanced oil recovery, and oilfield sewage treatment. In addition, the application issues and natural advantages of nanocellulose are analyzed, and suggestions and ideas on how to expand its application are put forward. Finally, the development and potential application of nanocellulose in oilfield chemistry are proposed.