Visible⁃light⁃photoredox catalysis has been recognized as a powerful technique to facilitate activation of organic molecules,enabling achievement of a wide variety of new chemical reactions.The combination of photoredox catalysis and nickel catalysis has shown even greater potential in promoting the cross⁃coupling reactions,owing to the advantages of low energy barrier,mild reaction condition and high selectivity.This review mainly focuses on the progress of carbon⁃carbon and carbon⁃heteroatom bond formation via the combination of photoredox catalysis and nickel catalysis in recently.The mechanisms of visible⁃light⁃photoredox catalyzed C-X (X＝C,N,O,P,S) bond formation are discussed in details.
In this paper,a detailed study of diffusion properties of n⁃dodecane over three different modified Y zeolites was conducted by ZLC (Zero⁃Lengthc⁃Column) method to investigate the influence of pore structure and acidity of zeolites on diffusion.The characterization of XRD,N2 adsorption/desorption and NH3⁃TPD showed that the crystal structure of the modified Y zeolite remained unchanged and the pore structure was similar to that of the modified Y zeolite.However,the ratio of n(Si)/n(Al) decreased,the total acid content on the surface decreased,and the distribution of acid strength also changed significantly.The results of diffusion study showed that the diffusion ability of modified Y zeolite was increased,and the diffusion coefficient of n⁃dodecane in zeolite increased and the diffusion activation energy decreased with the increase of the number of medium and strong acid sites in the sample,which contributed to the improvement of catalytic performance.
The C3N4/AC catalyst was prepared by using the same nitrogen content of cyanamide,thiourea,urea as precursor and activated carbon as the carrier. The reaction performance of C3N4/AC catalyst for the catalytic pyrolysis of 1,2⁃dichloroethane was evaluated by using fixed bed reactor,and the properties of catalyst structure were characterized by SEM,XRD,BET,XPS and TGA. The results showed that the initial activity and selectivity of the catalyst prepared from 0.110 mol precursor were close to 100%,but the stability of the catalyst was different obviously. The catalyst synthesized with urea as precursor had the highest catalyst stability compared with the other two precursors. However,the catalysts synthesized by using low loading of precursors showed differences on the catalytic performance. The structure and morphology of the catalysts with low loading of precursor were investigated. The results showed that when the load was reduced to 0.057 mol,the C3N4/AC catalyst prepared with urea had the highest catalytic activity for dehydrochlorination of 1,2⁃dichloroethane and the best stability.The different morphologies of carbon nitride was synthesized by different precursors. The carbon nitride productivity of thiourea and cyanamide is higher than urea but is more easily to form bulk carbon nitride which will result in poor stability. After all,urea is the optimal precursor for the C3N4/AC catalyst for dehydrochlorination of 1,2⁃dichloroethane.
For air⁃water⁃air⁃water⁃water⁃anion exchange resin system, the effects of solid loading, particle size, separator and different guide tube forms on mass transfer coefficients were studied in an airlift cyclone reactor (HALR) with a volume of 130 L (inner diameter 290 mm and height 2 000 mm) and an apparent gas velocity of 0~0.84 cm/s. The results showed that the volumetric mass transfer coefficients of the three phases system were larger than the two phases. As the particle size increased, the volumetric mass transfer coefficients decreased. The volumetric mass transfer coefficients with the solid separator was a little bigger than the none of separator.The volumetric mass transfer coefficient of the finned draft tube was the largest when the superficial gas velocity was small.
Alkali⁃Surfactant⁃Polymer (ASP) flooding can improve the flooding efficiency for oilfields which are in high water⁃cut period. In different ASP flooding stages, the rheological property of production fluid changes, which could affect the pump efficiency. Based on the improved sucker rod pumping system efficiency model, the pump depth, stroke length, stroke speed and pump diameter have been optimized through iterative algorithm. The effect of centralizer numbers, stroke length, stroke speed and flooding stages on sucker rod pumping system efficiency has been studied. The results indicate that the influence of stroke length and stroke speed is significant. The sucker rod pumping system efficiency first increased obviously and then trends to be gentle with the stroke length and speed increasing. The pumping system efficiency in main slug of ASP flooding is lowest. The centralizers can decrease the sucker rod pumping system efficiency slightly.
Surfactant/Polymer (SP) combination flooding is an effective method to enhance oil recovery of high quality reserves,while its surface produced liquid treatment technology and the simplification and optimization of operating parameters are both still a challenge for the promotion of the chemical flooding technology industrialization.In this paper,the emulsification of SP combination flooding produced liquid is characterized by multi⁃factor perpendicular experiments,and then the effect factors of demulsification and dehydration are studied.Significant test results indicated that,compared with the temperature and water cut,the effect of the concentration of surfactant and polymer in the produced liquid on dispersivity and electronegativity of the bulk was lower,which showed the greater contribution to emulsification stability of produced liquid,thus the demulsification of the produced liquid was declined.Bottle test experiments indicated that a single mechanism of improving demulsification temperature or prolonging demulsification time couldn’t fundamentally improve the dehydration rate of the produced liquid and reduce the oil content in the water after separation,meanwhile,the improvement of the pH of the water phase and the strong shear effect of the flow field would further deteriorate the effect of demulsification,dehydration and the water quality after separation.
As an important curve to understand the law of water flooding, the relationship between water cut and displacement multiples plays an important guiding role in understanding the rules of oilfield flooding, tapping the remaining oil and the law of water cut. However, during the experiment, due to the small size of core and high viscosity of crude oil and water, the accurate experimental data can not be obtained during the dry recovery period, the low water cut period or the middle water cut period, and the abnormal curve appears. The paper creatively establishes mathematical relation between water cut and displacement multiple, and corrects three kinds of abnormal curves of water cut and displacement multiple obtained from water flooding experiments in some heavy oilfields of Bohai Sea. According to the corrected curve, the water flooded map of M5⁃2 oilfield is drown up,which guides the remaining oil tapping the potential of the field.
Bases on the data of geology, drilling, logging and geochemistry, the formation conditions and distribution rules of tight oil reservoir in Fuyu oil layer of Sanzhap area were systematically analyzed. The results show that the study area has four advantages for tight oil accumulation. The crude oil is of good quality and strong fluidity, and the formation condition of the dense oil is superior. High quality hydrocarbon source rocks with wide coverage and large area distribution are close to the tight reservoirs, which provide sufficient oil source for the formation of tight oil reservoir. The compact reservoirs with wide area distribution provide effective reservoir space for the formation of compact oil reservoirs. The formation overpressure matches with the oil source fault, which provides sufficient power for the oil migration. At last, it is pointed out that the tight oil in Fuyu oil reservoir in Sanzhao area has the characteristics of large area (quasi) continuous distribution, strong oil heterogeneity. The channel sand body controls the local sweet area of the tight oil.
The Bayanhushu depression is in the initial stage of exploration, and its sedimentary characteristics and distribution are not clear. In this study, the types and characteristics of sedimentary system in Nantun Formation of Bayanhushu sag are discussed in detail by using core, well logging, seismic and grain size analysis data and combining with regional tectonic and geological background analysis. It is considered that there are 3 depositional systems of fan delta, braided river delta and lake in the study area. Braided River delta deposits and fan delta deposits are mainly developed in the gentle slope zone in the eastern part of the study area and the steep slope zone in the western part, is developed in the middle trough zone between the two.The braided river delta and fan delta deposits are mainly developed in the eastern gentle slope zon and the steep slope zone in the western part, while the lacustrine facies are developed in the middle trough zone. On the whole, the sedimentary pattern shows obvious characteristics of "North South Block and East West zoning". From the western steep slope zone to the eastern gentle slope zone, the sedimentary facies types transit from fan delta to deep lake⁃semi⁃deep lake and then gradually to the discriminate river delta. Reservoir physical properties of braided river delta front and fan delta front sand bodies are good and often adjacent to large⁃scale high⁃quality source rocks. Steep slope inversion structural reservoirs, fault⁃lithologic reservoirs and lithologic reservoirs are easy to form in steep slope zone, gentle slope zone and trough zone, respectively.
In view of the problems of premature formation of CO2 hydrate at the bottom of well and excessive displacement resistance during percolation caused by liquefaction of CO2 under high pressure in the process of exploiting CH4 hydrate by CO2 displacement method, at the same time, in order to obtain high pressure and CH4⁃enriched product gas, mixture of CO2/CH4 was selected as injection gas to study "inhibitor⁃gas displacement" in core displacement device. It was found that when the concentration of CH4 in the injected gas was 57.4%, CH4⁃enriched (72.9%) gas product was obtained at 7.5 MPa. Meanwhile the amount of CH4 in the received gas product was significantly higher than that of the injected CH4. In addition, the effect of methanol solution with low volume fraction (20%) and CH4 mixture with high volume fraction (77.9%) on gas hydrate decomposition was also evaluated. The results showed that with the dissociation of methane hydrate during methanol and CO2/CH4 injection, the CH4 hydrate almost didn't decompose in the deep part of reservoir model, while the formation process of CO2 hydrate was still very significant.
The acoustic emission(AE) technique was used to measure the AE signals of gas⁃liquid slug flow in horizontal pipes with non⁃intrusive and real⁃time monitoring features. Parameters of AE signals were calculated by setting window time and Critical Time of Elongated Bubble(CTEB). The characteristics of AE signal of slug unit were analyzed simultaneously. Based on the time delay of the same liquid slug arriving at two AE sensors, the AE method was used for detecting the translational velocity of liquid slug. Also, the measurement result of AE method was compared with the parallel conductivity method and Nicklin correlation. It is found that the AE signal of slug flow is very clear. The signals of liquid slug head, liquid slug body and elongated bubble decrease gradually and the signals of elongated bubble are below the threshold. The absolute energy and count of liquid slug increase with the superficial liquid and gas velocity respectively. AE technique could be used to monitor the frequency and translational velocity of liquid slug and it is a valuable method for application in the oil and gas field.
The loop pipe apparatus are used to simulate the different conditions of the actual pipeline and denoise the original signal by the wavelet method. Kernel⁃based Principal Component Analysis (KPCA) is used to extract the time⁃frequency domain eigenvalues of the leaked signals, and the final input vector of the neural network is obtained. Because the traditional BP neural network is easy to fall into local minimum when it is used to identify working conditions, the BP neural network is optimized by genetic algorithm (GA) and particle swarm optimization (PSO). Compared with the traditional BP neural network,the result show that the two optimized BP neural networks have stronger ability to identify leakage working conditions. Finally, from the two aspects of test accuracy and training time, two different optimization algorithms are compared and their different application situations are proposed.
An experimental device for high water⁃cut crude oil is designed and built, which mainly includes test pipeline, oil⁃water separation system, data acquisition system and circuit control system. The test section is designed of organic glass tube with a water bath, which observes flow morphology and initial deposition process. Considering the working conditions in the production site, oil⁃water mixing device is designed by drawing lesson of the principle of jet mixer. In order to ensure the effective separation of free water and crude oil during the experiment, an oil⁃water separator suitable for high water⁃cut crude oil is designed on the basis of free water separator. At the same time, a data acquisition system and circuit control system are designed, which can effectively solve the problems of data acquisition and parameter control. After Experimental verification, the experimental device can fulfill the research work of flow and deposition of high water⁃cut crude oil.
In the process of exploration and development, shallow gas does great harm to drilling operations. Currently, how to effectively seal the shallow well section to prevent secondary disasters, is a technical problem in petroleum industry both at home and abroad. There are shallow gas in many blocks in Bohai oilfield, and the most typical one in Bozhong area. The conventional cementing cementing of shallow gas is difficult to meet the sealing requirements, resulting in the leakage of shallow gas to bring economic loss and drilling engineering risk. Aiming at the problem of shallow gas prevention and control, this paper improves drilling technology, cementing method, cement type optimization and auxiliary measures, innovatively introduces resin cement slurry system, and forms a set of sealing technology suitable for shallow gas in Bohai bay, which has been successfully applied in Bozhong A oilfield to ensure drilling operation safety and to achieve greater economic benefits.
Several studies have been done on the acid system and acidizing operation parameters in order to improve acidizing effect on high water⁃cut horizontal well of CFD11⁃2 oilfield.The results show that the corrosion capacity to rock of mud acid is higher than fluoroboric acid and muti⁃hydrogen acid,while the retard capacity to rock of muti⁃hydrogen acid is superior to mud acid and fluoroboric acid.The results by simulate on acidizing operation parameters show that high injection rate is favorable to improving acidizing effect,and the pollution can be removed effectively when acidizing radius is 1~2 m.Soil acid with strong dissolution ability and polyhydrogen acid with high retardation ability were firstly used in acidizing operation of three wells in Caofeidian 11⁃2 oilfield.After field operation,the average daily fluid increment of three wells was 362 m3/d,and the average daily oil increment of single well was 16.4 m3/d.The effect of plugging removal and stimulation was remarkable.
