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ABSTRACT In recent years, with increasing global demand for oil and gas resources and continuous decline in conventional oil and gas production, the global development focus has shifted from conventional medium to high permeability reservoirs to low permeability and tight oil reservoirs. As a result, nanoparticles (NPs) have found a promising role in enhanced oil recovery as potential improved oil recovery agents in low permeability. Despite many experiments that have proved that nanoparticles can be adsorbed on the rock surface in a macroscopic perspective, the adsorption mechanism and the effects of molecular structure on the adsorption behavior of nanoparticles on rock surfaces remain scarce. Here, the fundamental phenomena involved in hydrophobic nanoparticles adsorption on rock surface and the effect of mineral composition on adsorption mechanism were elucidated by the analysis of molecular dynamics simulation. The simulation results show that water molecules could form two adsorption layers on both quartz and kaolinite surfaces. Hydration layer thickness of kaolinite is greater than that of the quartz surface. The solid/liquid interface hydration layer thickness of quartz–water system is approximately 0.71 nm, while the thickness of kaolinite–water system is approximately 0.75 nm. Furthermore, coulombic interactions are the main influencing factor for the stable adsorption of nanoparticles on the wall. Nanoparticles can only break through the first adsorption layer to absorb on the layer. Finally, wetting angle tests were conducted which indicated that SiO2 nanoparticles can be adsorbed on the surface and have a good wetting reversal effect. Our study highlights the adsorption mechanism of nanoparticles on a molecular level, which may help to promote the development of low permeability and tight oil reservoirs.

A Oilfield is Fluvial Facies Low Permeable Reservoir, main layer is Low bend distributary channel sand body deposition, In order to better understand the distribution of single sand body and remaining oil in the reservoir, inspection well coring and tracer tests have been carried out successively in the same well area of the oilfield, based on these data, it is found that, the actual distribution of single sand body is very different from the original description in both vertical and plane. Discovered by the inspection well core data, the scale of the vertical single-phase body was too large. It was originally considered to be the mudstone interlayer inside the 0.2m single sand body, which is actually the interlayer between different single sand bodies, and this situation was confirmed by the trace data five years later. The distribution position and scale of single sand body on the plane are also different from the original description. It was thought that the oil and water well sand body with good internal connection in the same single sand body is actually not connected. Therefore, the experience of these data on vertical and horizontal single sand body identification is summarized to guide the subsequent single sand body characterization of the oilfield, so as to better guide the oilfield to describe the remaining oil and adjust and tap the potential.

Foam injection is widely applied in amounts of fields to drilling, production, and formation protection. Sometimes, the application result is disappointing, which is caused by the failure of bubble generation in foam flooding. Therefore, it is necessary to seek ways for improving the performance of foam injection. An increased disturbance to the stratum, like the vibration caused by a seismic oil recovery technique, would be helpful. In the current work, the seepage of air foam in porous media under low frequency (LF) vibration is analyzed with experiments and an investigation of bubble creation/destruction rate change is carried out using mathematical modeling. The resistance factor of foam flooding under indoor vibration increases by 1.5 times and the valid time is obviously extended compared with when no vibration is used. The optimal vibrating acceleration and frequency of 0.7 m/s2 and the natural frequency of the cores-nearby of 18 Hz are achieved in the indoor experiments. Under vibration, the bubble generation rate increases, while bubble break rate by internal expansion or by gas diffusion and transfer decreases. An interesting phenomenon is also observed, which might develop a power level formula between the initially defined dimensionless MRF (maximum foam flooding resistance factor) and dimensionless DMRF (duration of maximum foam flooding resistance factor). The power product and sum of the power exponents of the above formula both equal approximately to 1. With the assistance of LF vibration, the increase of security, adaptability, and efficiency in foam injection may improve the reservoir recovery and extend its application.

South layer in Zanarol Oilfield has nearly 30 million tons of oil reserves. However, as the reservoir is the thin (4.4-16.1 m), poor in physical properties (0.3-1 × 10-3 μm²), and low in formation pressure, etc. It is difficult to achieve economic production by vertical wells, horizontal wells are also low in productivity. By introducing the integrated staged completion, acid fracturing, gas lifting and commissioning technique, stage number selection, parameter optimization. ECP + multi-slide sleeve completion, liquid nitrogen pre-injection and gas lifting in one trip has been realized. Field application results show can increase the control area of horizontal wells, improve reservoir conductivity, shorten flowback time after acid fracturing and enhance single well production. Horizontal well staged acid fracturing, which achieves the effctivly reserves producing in this area, is of great instructive significance for for the high efficient development of reserves in low-permeable reservoirs. [ABSTRACT FROM AUTHOR]

Properties of the surfactant SHSA - 03 - JS applied to Block 7 in Jiangsu oilfield were studied in terms of evaluation on decreasing interfacial tension capability, e-mulsifying capacity, changing rock wettability capability, adsorption amount and oil displacement efficiency. The flooding mechanism of surfactant flooding mechanism on low permeability reservoirs was also investigated. The results showed that the interfacial tension of SHSA - 03 - JS and rude oil can reach the order of 10 mN/m with the concentration of 0. 05 % ~ 0. 6 % , and even reduced to 10-3 mN/m n a concentration range of 0. 1 % ~ 0. 3%. At the same time, the surfactant could change the oil - wet quartz to water-wet. In addition, the adsorption amount of SHSA - 03 - JS in Block 7 reservoir sand was 4. 78 mg/g when the injection concentration was 0.3%. Lastly, the core-flooding est in lab showed that the oil displacement efficiency of surfactant flooding with 0. 3% SHSA - 03 - JS was 11. 47% higher than that of the water flooding. In brief, SHSA-03- JS could meet the requirements for surfactant flooding in Block 7, Jiangsu oilfield. [ABSTRACT FROM AUTHOR]