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CO2 EOR (enhanced oil recovery) will be one of main technologies of enhanced unconventional resources recovery. Understanding effect of permeability and fractures on the oil mobilization of unconventional resources, i.e. tight oil, is crucial during CO2 EOR process. Exposure experiments based on nuclear magnetic resonance (NMR) were used to study the interaction between CO2 and tight oil reservoirs in Chang 8 layer of Ordos Basin at 40 °C and 12 MPa. Effect of permeability and fractures on oil mobilization of exposure experiments were investigated for the different exposure time. The oil was mobilized from matrix to the surface of matrix and the oil recovery increased as the exposure time increased. The final oil recovery increased as the core permeability increased in these exposure experiments. Exposure area increased to 1.75 times by fractures resulting in that oil was mobilized faster in the initial stage of exposure experiment and the final oil recovery increased to 1.19 times from 28.8 to 34.2%. This study shows the quantitative results of effect of permeability and fractures on oil mobilization of unconventional resources during CO2 EOR, which will support CO2 EOR design in Chang 8 layer of Ordos Basin.

CO2 EOR (enhanced oil recovery) will be one of main technologies of enhanced unconventional resources recovery. Understanding effect of permeability and fractures on the oil mobilization of unconventional resources, i.e. tight oil, is crucial during CO2 EOR process. Exposure experiments based on nuclear magnetic resonance (NMR) were used to study the interaction between CO2 and tight oil reservoirs in Chang 8 layer of Ordos Basin at 40 °C and 12 MPa. Effect of permeability and fractures on oil mobilization of exposure experiments were investigated for the different exposure time. The oil was mobilized from matrix to the surface of matrix and the oil recovery increased as the exposure time increased. The final oil recovery increased as the core permeability increased in these exposure experiments. Exposure area increased to 1.75 times by fractures resulting in that oil was mobilized faster in the initial stage of exposure experiment and the final oil recovery increased to 1.19 times from 28.8 to 34.2%. This study shows the quantitative results of effect of permeability and fractures on oil mobilization of unconventional resources during CO2 EOR, which will support CO2 EOR design in Chang 8 layer of Ordos Basin.

Flue-gas foam/surfactant polymer flooding is a novel technology to enhanced oil recovery for heavy oil reservoir after hot water flooding with safety and efficiency. However, high temperature and the complex composition of flue gas greatly influence the foaming ability of the foaming agent, and weaken the plugging and profile control ability of the foam. Hence, screening suitable foam agents is of great significance. Here, a typical terpolymer of N‒methyl butenone carboxylates, alkyl phenyl sulfonates and pyrrolidone was selected as an efficient foam agent. The foaming performance and stability of the foam agent remained unchanged after 300 °C aged for 72 h in the flue gas atmosphere. Foam performance and stability tests in the simulative flue gas environment, adsorption properties of oil sands, and resistance factor evaluation were carried out. It showed good foam performance and stability, low adsorption capacity (0.77 mg/g), low interfacial tension (10−2 mN/m) and high resistance factor (>418), which indicated that the terpolymer (PNCAS) can reduce the gas channeling and increase the sweep area. The results of homogeneous and heterogeneous model experiments and microscopic mechanism suggested that foam flooding can greatly improve oil recovery while the low permeable sand-pack recovery can increase almost 42% in comparison with the conventional hot water flooding.

The ultrasonic guided wave testing method is very effective in monitoring the safety of complex structures. The fundamental shear horizontal (SH) wave mode has the advantage that the propagation velocity does not change with the frequency. However, accurately recognizing the ultrasonic signal is difficult due to the SH guided wave’s bidirectional propagation characteristics generated by the Lorentz force mechanism. Therefore, it is necessary to achieve unidirectional focusing of Lorentz force-generated SH guided waves. A newly designed SH guided wave electromagnetic acoustic transducer (EMAT) is proposed with an interlaced periodic permanent magnet (PPM) and AC coils of different phases. A 3D model based on the electromagnetic mode and the solid mechanics mode using COMSOL software is calculated and compared with the bidirectional focusing EMATs. The results show that there are many influencing factors in the structural design of the transducers, and the focal radius and the angle of the individual PPMs are discussed in this work. The results indicate that the new unidirectional EMAT shows superiority in many cases, and the decrease of the focal radius with a suitable aperture angle will increase the focusing intensity of the signal.

Molecular dynamics simulations have been performed to investigate the structural properties of hydroxyl-substituted alkyl benzenesulfonate monolayers formed at the water/vapor and water/decane interfaces. We report a detailed study of the interfacial properties—liquid density profile, hydrogen bond structure, surfactant aggregate structure and order parameter—of the novel anionic surfactant, sodium 2-hydroxy-3-decyl-5-octylbenzenesulfonate (C10C8OHphSO3Na). Simulation results show that: with increasing number of surfactant molecules, the average number of intramolecular hydrogen bonds per surfactant molecule in the monolayer decreases, but the structures forming the intramolecular hydrogen bonds still play a dominant role; the hydrophobic part of the alkyl tail chain, especially the decyl substituent on the third carbon atom in the benzene ring, becomes straighter, and more ordered towards the external interface at higher surfactant coverage; two-dimensional radial distribution functions can describe the characteristic of surfactant aggregate structures and highlight the decane phase effect on the orientation of the hydrophobic part of the surfactant; the surfactant molecules readily form long-range hydrogen bonded structures. Our results are an important complement to experimental studies. We used the all-atom model by employing the GROMACS and ffAMBER programs in the simulations, which provides a new way to simulate the interfacial behavior of alkyl benzenesulfonate surfactants.

Molecular dynamics simulations on the interface between liquid water and liquid n-alkane (including octane, nonane, decane, undecane and dodecane) have been performed with the purpose to study the interfacial properties: (I) density profile; (II) molecular orientation; (III) interfacial tension and the temperature effect on the interfacial tension. Simulation results show that at the interface the structures of both water and n-alkane are different from those in the bulk. Water has an orientational preference due to the number of hydrogen bonds per molecule maximized. N-alkane has a more lateral orientation with respect to the interface in order to be in close contact with water. The calculated individual phase bulk density and interfacial tension of water/n-alkane systems are in good agreement with the corresponding experimental ones.

Viscoelastic properties of two polymers, partially hydrolyzed polyacrylamide and partially hydrolyzed modified polyacrylamide, widely used in chemical flooding in the petroleum industry, were investigated at three interfaces, water–air, water–dodecane, and water–crude oil, by means of a dilational method provided by I.T. Concept, France, at 85 °C. Polymer solutions were prepared in brine with 10,000 mg/l sodium chloride and 2000 mg/l calcium chloride. It has been shown that the viscoelastic modulus increases with the increment of polymer concentration in the range of 0–1500 mg/l at the water–air interface. Each polymer shows different viscoelatic behavior at different interfaces. Generally speaking, values of the viscoelastic modulus ( E ), the real part ( E ′), and the imaginary part ( E ″) at the crude oil–water interface for each polymer are lower than at the air–water or water–dodecane interface. The two polymers display different interfacial properties at the same interface. Polymer No. 2 gives more viscous interfaces than polymer No. 1. All the information obtained from this paper will be helpful in understanding the interfacial rheology of ultra-high-molecular-weight polymer solutions.

The adsorption behavior of zwitterionic surfactant dodecyl sulfobetaine (DBS) on a silica/solution interface with Ca(2+), Mg(2+) existing in aqueous solution is explored by atomistic molecular simulations. The interaction energy contribution of van der Waals and electrostatic potentials in the surfactants/water/silica system are respectively calculated, from which the electrical interaction can be found to play a decisive role in the adsorption tendency of DBS on the silica surface with or without inorganic ions, despite different mechanisms. The distinct decrease of energy has been found to be derived from electrical interaction when DBS adsorb on the silica surface covered by Ca(2+) or Mg(2+). Therefore, it can be predicted that the cationic ions combined on the negatively charged silica surface in a mineral water medium might decrease the adsorption trend of DBS on the silica surface, which has been experimentally proven by TOC measurement. Structural information of the close interface layer and the distribution of water molecules are analyzed after the complete molecular dynamics simulation using a ternary model. Ca(2+) and Mg(2+) combined on the silica surface can reduce the adsorption amount of DBS by preventing the direct interaction between DBS and surface, and bringing about the orientation reversal of DBS molecules to break the order of adsorption interface layer. Furthermore, changes in the status of the water spreading on the silica surface caused by the complexation of cations are also an important reason in the adsorption reduction.

Hollow fibre based liquid phase microextraction (HF-LPME) with high performance liquid chromatography (HPLC) was developed for the determination of alkaloids in Corydalis yanhusuo. Three alkaloids (protopine, tetrahydropalmatine, tetrahydroberberine) were extracted from a 10 mL alkaline sample (donor phase) to an organic phase impregnated in the pores of the hollow fibre, and then, they were extracted to an acidic solution (acceptor phase) in the lumen of the fibre. The extract was determined directly by HPLC. Parameters affecting the HF-LPME include the organic solvent, pH of the donor and the acceptor phase, the extraction time and the stirring speed were investigated systematically. To minimize the error of the injection, palmatine was added as an internal standard (I.S.). Under optimal conditions, calibration curves were obtained in the range of 0.1–1.0 mg L−1 with a reasonable linearity (r 2 > 0.993) and the limits of detection (LODs) ranged between 10.0 × 10−3 mg L−1 and 13.7 × 10−3 mg L−1. Additionally, enrichment factors with 100 to 184-fold were obtained. The method was then applied to the crude extract of Corydalis yanhusuo successfully.

Chengdao oil field is a large oil-gas field, which is situated in a very shallow water area of Bohai Bay of China. According to the complicated maritime and geological situation, the compositive study method containing several kinds of appropriate new techniques has been applied in the course of researching work on the geology and engineering situation of the reservoir. For example: The technique of logging constraining seismic inversion has been applied to predict the fluvial sand body's scales. As a result, the coincidental rate of the total number of layers up to 88% and the coincidental rate of the total thickness up to 92%.On the base of the study in pilot test area, multiple techniques, such as reservoir simulation and economic evaluation, have been applied to optimize the developing plan and preserve the pressure levels of the reservoir. It can also be used to determine the reservoir productivity and predict developing project parameters. The coincidental rate of reservoir productivity is 97.8%.The application of enlarging well spacing and irregular well sites aiming at the main oil-hearing sand bodies has saved investment and improved economic efficiency. The project of Shengli offshore oilfield productivity building has been established on the base of compositive study on the reservoir geology. It contains 33 Well Group, 119 wells totally. The successful ratio of drilling is up to 100% and the accumulated productivity is up to 2,480,000 tons. By present, a set of techniques appropriate to the development of very shallow water oil field has been formed and the high-speed and high-efficiency development of Chengdao oil field has been achieved by using it.