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For high temperature and high salinity reservoirs, the foam formulation system is required to have better foaming capacity and foam stability under formation conditions in tertiary EOR. In order to obtain a new foam agent suitable for this type of oil reservoir, through the compounding and testing of 7 common oilfield foam chemical agents, 15 formulated foam agents are tested and screened. Then the foam displacement experiment of the dual sand packs model was established to simulate the new foam flooding process. The production dynamic of the high-permeability sand pack and the low-permeability sand pack was captured and analyzed, and EOR mechanism of the foam system in the heterogeneous reservoir was clarified. The experimental results show that the formulation of B4(anionic & nonionic combined surfactant) & FSN100(fluorinated surfactant) with a mass proportion of 2:3 (BF23) has the best performance in terms of foaming properties, low interfacial tension reduction, and oil washing efficiency. Furthermore, BF23 foam injection greatly increased the recovery factor from 36.7% to 61.6%, clearly displacing the remaining oil in the low-permeability pack. Finally, the new foam agent solution used in Shenger block of Shengli Oilfield shows its good value for enhanced oil recovery. [ABSTRACT FROM AUTHOR]

Aiming at the challenges of rapid heat dissipation, limited swept efficiency, and a rapid water cut increase in steam huff and puff development in heavy oil reservoirs, an alternating steam and CO2/viscosity reducer huff and puff method for IOR was proposed. In this work, the effect of CO2 on the physical properties of heavy oil was evaluated, and the optimal concentration of viscosity reducer for synergistic interaction between CO2 and the viscosity reducer was determined. Next, novel huff and puff simulation experiments by three sandpack models of different sizes in series were analyzed. Then, the IOR difference between the pure steam huff and puff experiments and the steam-alternating CO2/viscosity reducer huff and puff were compared. Finally, the CO2 storage rate was obtained based on the principle of the conservation of matter. The results show that the optimal viscosity reducer concentration, 0.8 wt%, can achieve a 98.5% reduction after combining CO2. The steam-alternating CO2/viscosity reducer huff and puff reached about 45 cm at 80 °C in the fifth cycle due to the CO2/viscosity reducer effects. CO2/viscosity reducer huff and puff significantly reduces water cut during cold production, with an ultimate IOR 15.89% higher than pure steam huff and puff. The viscosity reducer alleviates heavy oil blockages, and CO2 decreases oil viscosity and enhances elastic repulsion energy. The highest CO2 storage rate of 76.8% occurs in the initial stage, declining to 15.2% by the sixth cycle, indicating carbon sequestration potential. These findings suggest that steam-alternating CO2/viscosity reducer huff and puff improves heavy oil reservoir development and provides theoretical guidance for optimizing steam huff and puff processes. [ABSTRACT FROM AUTHOR]

Steam displacement is prone to cross-flow, small swept area, large oil–water ratio, large oil–water interfacial tension, and low oil displacement efficiency. Compared with steam flooding, foam flooding can effectively reduce the residual oil in the small throat of the main flow channel and the small hole in the near flow channel and increase the overall recovery factor. Therefore, researchers carried out CO2 and chemical agent-assisted steam displacement. However, at present, there is a lack of research on the occurrence mechanism and model of residual oil. Steam flooding often encounters challenges such as cross-flow, limited sweep area, and high oil–water ratio. Foam flooding offers a promising alternative by effectively reducing residual oil in narrow throats and the near flow channel, thereby enhancing overall recovery rates compared to steam flooding alone. Therefore, chemical agent-assisted steam flooding was applied to enhance heavy oil recovery. However, the occurrence mechanism and model of residual oil after chemical agent-assisted steam is not clear. To fill this gap, the CO2 foam viscosity reducer assisted steam (CFVAS) flooding technology has been adopted and carried out in several studies. First, the foam viscosity reducer was prepared and its foam properties (viscosity reduction effect, foam volume, and half-life) were tested. Subsequently, the CFVAS displacement experiments after steam flooding were carried out, and the flow behavior of the remaining oil in multiple regions (main flow channel, near flow channel, and far flow channel) was analyzed. Finally, the shape and number of remaining oil under different displacement stages were compared, and the occurrence mode of remaining oil under CFVAS displacement was determined. The results indicate the following: (1) During steam flooding, the amount of near flow channel residual oil decreased with injected pore volumes (PV), transforming into columnar structures in small perforations and film-like formations in far flow channels. (2) CFVAS flooding, including the foam stability mechanism, flow channel adjustment mechanism, and emulsification and dispersion mechanism, can improve overall recovery rates by 55.2% by driving the remaining oil in near flow channels. (3) During CFVAS flooding stage, crude oil mobility notably improved and flooding front expanded more evenly. Residual oil primarily existed as oil-in-water (O/W) emulsions with discontinuous columns. (4) In the CFVAS flooding stage, residual oil mainly formed O/W emulsions through emulsification and dispersion, with foam-filled large and medium pores, concentrating residual oil in thick and middle throats. This work can provide important references for injecting CO2 gas into reservoirs to enhance heavy oil recovery and promote carbon sequestration. [ABSTRACT FROM AUTHOR]

Although waterflooding treatment assisted by traditional viscosity reducer yields additional oil recovery, this increments in production sometimes cannot meet the production requirements. To solve this problem, it is necessary to analyze and understand the flow mechanism of heavy oils in the waterflooding process assisted by the viscosity reducer. This study employed an etched glass micro-model to visualize the flow behavior of heavy oils under assistance of a novel multi-functional viscosity reducer with the condition of high temperature and ultra-heavy oil. The water flooding and novel viscosity reducer flooding experiments were carried out, and the state and shape of the remaining oil phase were observed from the global perspective and the microscopic local perspective in the etching micro-glass. Results show that the viscosity reducer solution can not only greatly reduce viscosity of heavy oil but also decrease oil-water interface tension. In the waterflooding process, the continuous oil group and long oil slug are the main characteristics of remaining heavy oil in the reservoir. By waterflooding with the new viscosity-reducer, the remaining oils exist as short slug and droplet, and 3 times wider flooding area for fluid-flow was observed than conventional waterfloodings. [ABSTRACT FROM AUTHOR]

The dispersion characteristic of nanoparticles is of more interest in some engineering applications, including polymer filling, foam stability, chemical catalysis, and materials surface package. In this paper, the surface modification of SiO2 nanoparticles was carried out based on molecular dynamics simulation. The characteristics of aggregation and diffusion of SiO2 nanoparticles were explained by the radial distribution function (RDF), concentration profile, length distribution, mean squared displacement (MSD), and microscopic testing (MT). The results showed that the orbital provided by the three types of atoms (H, O, and Si) corresponding to the different bandwidths caused the energy alternation of state density. According to the results of RDF, the HO bond energy mainly provided by the water molecules showed the maximum bond energy with 463 kJ/mol. The results indicated that the bonds breakage and formation were accompanied by changes in total energy, kinetic energy, non‐bond energy, and potential energy. After the modification of SiO2 nanoparticles, the concentration profile of the water molecules decreased first at 1–8.5 Å and then increased at 8.5–17.2 Å, but the length distribution climbed to 15.7 at 0.975 Å. When the temperature reached 398 K, the peak value of the length distribution declined to 13.6 Å and the relative concentration profile of water molecules fluctuated around 1.0. With the increase of salinity, the peak value of length distribution reached 15.7 at 0.975 Å, but the concentration profile of water molecules at 3.1–9 Å decreased quickly and then gradually increased. The results of MSD and MT about water molecules presented the largest diffusion coefficient appeared at 398 K and had the best dispersion effect owing to the average kinetic energy among the molecules. Conversely, the diffusion coefficient decreased with the incremental solution salinity because the inhabitation of sodium for the motion of water molecules resulted in the ion bridging and hydrogen bonding. [ABSTRACT FROM AUTHOR]

Byline: Qingjie Zhu, Youpo Su, Desheng Dash Wu Risk assessment for suitability is one of the main problems in city landuse planning for disaster prevention. Decision-making strategy using GIS-based Ordered Weighted Averaging (OWA) method is discussed through analysing OWA evaluation procedure. Data of geological disaster in Tangshan City are used to calculate the distances from dangerous areas or safety area to yield evaluation criteria for all disaster factors of land-use suitability.