查看更多>>摘要：The cavitation cloud impingement of the jet in the rock breaking process was experimentally investi-gated to reveal the jet erosion mechanism in drilling of petroleum exploitation.Serial erosion tests and flow visualization were performed,where the cavitation cloud motion in the erosion crater was obtained with the designed transparent specimen.Various erosion patterns were identified in the whole erosion process based on the eroded specimen topography.The shallow eroded crater with a shrinking erosion area is generated by the combination of impinging and scattering cavitation clouds.The increase of ld promotes the development of cavitation cloud σc but reduces the impingement frequency fd,suggesting that the jet aggressive ability is enhanced when the balance between ac and fd is reached.The cavitation cloud motion in the erosion crater was investigated with the transparent specimen.The erosion in the crater at shorter exposure periods Te is generated by the combination of impingement and restricted scattering of cavitation clouds.With the continuous development of the erosion damage,the jet's aggressive ability is diminished due to the erosion expansion on sandstone,where the cavitation clouds impinge on the target and then collapse and vanish without restricted scattering.
查看更多>>摘要：Supercritical CO2(SC-CO2)fracturing,being a waterless fracturing technology,has garnered increasing attention in the shale oil reservoir exploitation industry.Recently,a novel pre-SC-CO2 hybrid fracturing method has been proposed,which combines the advantages of SC-CO2 fracturing and hydraulic frac-turing.However,the specific impacts of different pre-SC-CO2 injection conditions on the physical pa-rameters,mechanical properties,and crack propagation behavior of shale reservoirs remain unclear.In this study,we utilize a newly developed"pre-SC-CO2 injection → water-based fracturing"integrated experimental device.Through experimentation under in-situ conditions,the impact of pre-SC-CO2 in-jection displacement and volume on the shale mineral composition,mechanical parameters,and fracture propagation behavior are investigated.The findings of the study demonstrate that the pre-injection SC-CO2 leads to a reduction in clay and carbonate mineral content,while increasing the quartz content.The correlation between quartz content and SC-CO2 injection volume is positive,while a negative correlation is observed with injection displacement.The elastic modulus and compressive strength exhibit a declining trend,while Poisson's ratio shows an increasing trend.The weakening of shale mechanics caused by pre-injection of SC-CO2 is positively correlated with the injection displacement and volume.Additionally,pre-injection of SC-CO2 enhances the plastic deformation behavior of shale,and its breakdown pressure is 16.6％lower than that of hydraulic fracturing.The breakdown pressure demon-strates a non-linear downward trend with the gradual increase of pre-SC-CO2 injection parameters.Unlike hydraulic fracturing,which typically generates primary fractures along the direction of the maximum principal stress,pre-SC-CO2 hybrid fracturing leads to a more complex fracture network.With increasing pre-SC-CO2 injection displacement,intersecting double Y-shaped complex fractures are formed along the vertical axis.On the other hand,increasing the injection rate generates secondary fractures along the direction of non-principal stress.The insights gained from this study are valuable for guiding the design of preSC-CO2 hybrid fracturing in shale oil reservoirs.
查看更多>>摘要：The pressure-preserving controller is the core part of deep in-situ pressure-preserving coring(IPP-Coring)system,and its pressure-preserving capability is the key to IPP-Coring technology.To achieve a good understanding of the influence of mechanical properties of materials on the ultimate pressure-bearing capability(UPB-Capability)of the pressure-preserving controller,the IPP-Coring experimental platform was developed to test the UPB-Capability of pressure-preserving controllers of four different materials.The experimental results show that the UPB-Capability of pressure-preserving controllers with different material varies greatly.A numerical model of the pressure-preserving controller was developed to study the influences of mechanical parameters of materials on the UPB-Capability of the pressure-preserving controller after the accuracy of the numerical model is verified by experiments.The results indicate that the yield strength(YS)and Poisson's ratio(PR)of the material have little effect on the UPB-Capability of the pressure-preserving controller,whereas the elastic modulus(EM)of the material has a significant effect.A generalized model of the UPB-Capability of the pressure-preserving controller is developed to reveal the mechanism of the influence of material properties on the UPB-Capability of the pressure-preserving controllers.Considering these results,the future optimization direction of the pressure-preserving controller and material selection scheme in practical engineering applications of the pressure-preserving controller are suggested.
查看更多>>摘要：In the production of the sucker rod well,the dynamic liquid level is important for the production effi-ciency and safety in the lifting process.It is influenced by multi-source data which need to be combined for the dynamic liquid level real-time calculation.In this paper,the multi-source data are regarded as the different views including the load of the sucker rod and liquid in the wellbore,the image of the dyna-mometer card and production dynamics parameters.These views can be fused by the multi-branch neural network with special fusion layer.With this method,the features of different views can be extracted by considering the difference of the modality and physical meaning between them.Then,the extraction results which are selected by multinomial sampling can be the input of the fusion layer.During the fusion process,the availability under different views determines whether the views are fused in the fusion layer or not.In this way,not only the correlation between the views can be considered,but also the missing data can be processed automatically.The results have shown that the load and pro-duction features fusion(the method proposed in this paper)performs best with the lowest mean ab-solute error(MAE)39.63 m,followed by the features concatenation with MAE 42.47 m.They both performed better than only a single view and the lower MAE of the features fusion indicates that its generalization ability is stronger.In contrast,the image feature as a single view contributes little to the accuracy improvement after fused with other views with the highest MAE.When there is data missing in some view,compared with the features concatenation,the multi-view features fusion will not result in the unavailability of a large number of samples.When the missing rate is 10％,30％,50％and 80％,the method proposed in this paper can reduce MAE by 5.8,7,9.3 and 20.3 m respectively.In general,the multi-view features fusion method proposed in this paper can improve the accuracy obviously and process the missing data effectively,which helps provide technical support for real-time monitoring of the dynamic liquid level in oil fields.
查看更多>>摘要：During injection treatments,bottomhole pressure measurements may significantly mismatch modeling results.We devise a computationally effective technique for interpretation of fluid injection in a wellbore interval with multiple geological layers based on the bottomhole pressure measurements.The perme-ability,porosity and compressibility in each layer are initially setup,while the skin factor and partitioning of injected fluids among the zones during the injection are found as a solution of the problem.The problem takes into account Darcy flow and chemical interactions between the injected acids,diverter fluids and reservoir rock typical in modem matrix acidizing treatments.Using the synchronously recorded injection rate and bottomhole pressure,we evaluate skin factor changes in each layer and actual fluid placement into the reservoir during different pumping jobs:matrix acidizing,water control,sand control,scale squeezes and water flooding.The model is validated by comparison with a simulator used in industry.It gives opportunity to estimate efficiency of a matrix treatment job,role of every injection stage,and control fluid delivery to each layer in real time.The presented interpretation technique significantly improves accuracy of matrix treatments analysis by coupling the hydrodynamic model with records of pressure and injection rate during the treatment.
查看更多>>摘要：Heavy oil is an important resource in current petroleum exploitation,and the chemical composition information of heavy oil is crucial for revealing its viscosity-inducing mechanism and solving practical exploitation issues.In this study,the techniques of high-temperature gas chromatography and high-resolution mass spectrometry equipped with an electrospray ionization source were applied to reveal the chemical composition of typical heavy oils from western,central,and eastern China.The results indicate that these heavy oils display significant variations in their bulk properties,with initial boiling points all above 200 ℃.Utilizing pre-treatment and ESI high-resolution mass spectrometry,an analysis of the molecular composition of saturated hydrocarbons,aromatic hydrocarbons,acidic oxygen com-pounds,sulfur compounds,basic nitrogen compounds,and neutral nitrogen compounds within the heavy oil was conducted.Ultimately,a semi-quantitative analysis of the molecular composition of the heavy oil was achieved by integrating the elemental content.The semi-quantitative analysis results of Shengli-J8 heavy oil and a conventional Shengli crude oil show that Shengli-J8 heavy oil lacks alkanes and low molecular weight aromatic hydrocarbons,which contributes to its high viscosity.Additionally,characteristic molecular sets for different heavy oils were identified based on the semi-quantitative analysis of molecular composition.The semi-quantitative analysis of molecular composition in heavy oils may provide valuable reference data for establishing theoretical models on the viscosity-inducing mechanism in heavy oils and designing viscosity-reducing agents for heavy oil exploitation.
查看更多>>摘要：The gelation of crude oil with high wax and asphaltene content at low temperatures often results in the block of transportation pipeline in Africa.In recent years,it was reported that surface hydrophobic-modified nanoparticles have important applications in crude oil flow modification.In this work,four kinds of core-shell hybride nanoparticles by grafting poly(octadecyl,docosyl acrylate)and poly(acry-late-a-olefin)onto the surface of nano-sized SiO2 were synthesized by grafting polymerization method.The chemical structure of nanoparticles was analyzed by Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and thermogravimetric analysis(TGA).The rheological behaviors of crude oil and precipitation of asphaltenes in the presence of nanoparticles were studied by measuring the viscose-temperature relationship curve,the cumulative wax precipitation amount,and morphology of waxes and asphaltenes.The results indicate that the docosyl polyacrylate@SiO2 nanoparticle(PDA@SiO2)can reduce the cumulative wax precipitation amount of crude oil by 72.8％,decline the viscosity of crude oil by 85.6％at 20 ℃,reduce the average size of wax crystals by 89.7％,and inhibit the agglomeration of asphaltene by 74.8％.Therefore,the nanoparticles not only adjust the crystalline be-haviors of waxes,but also inhibit the agglomeration of asphaltenes.Apparently,core-shell hybride nanoparticles provides more heterogeneous nucleation sites for the crystallization of wax molecules,thus inhibiting the formation of three-dimensional network structure.The core-shell polymer@SiO2 hybride nanoparticles are one of promising additives for inhibiting crystallization of waxes and agglomeration of asphaltenes in crude oil.
查看更多>>摘要：It has been demonstrated that almost all polymer-clay nanocomposites show higher temperature sta-bility than that of pure polymer,which is attributed to the active exfoliated clay nanosheet firmly adsorbed onto the polymer chains,due to polerization and nucleation effect,the clay nanosheets could protect the polymer chains from destroying.To prove such mechanism,the water-soluble polymer nanocomposites(AAA/SLS-MMT)were synthesized by the in-situ polymerization of 2-acrylamide-2-methyl-propane sulfonic acid,acrylamide,4-acryloylmorpholine,and organically modified montmoril-lonite.The techniques of nuclear magnetic resonance,atomic force microscopy and scanning electron microscopy etc.,clearly characterized the successful synthesized of sample's structure,the exfoliated MMT nanosheet adsorbed polymer chain's scale,and well-dispersed morphology,espectively.The adsorption model,X-ray photoelectron spectroscopy presented the existence of strong adsorption,while molecular simulation calculations first concluded that the strong adsorption energy was-13032.06 kcal/mol.Thermo-gravimetric-analysis proved the temperature of maximum thermal degradation of powder sample(AAA/1.0 wt％SLS-MMT)was over 298 ℃.After ageing at 180 ℃ for 4 h,the apparent viscosity of 5 g/L AAA/1.0 wt％SLS-MMT aqueous solution was 326.7 mPa-s,while that of pure polymer(AAA)was only 8.3 mPa-s.This optimized sample has the smallest FLAPI value at all test temperatures from 180 to 220 ℃ in both fresh and salt water based drilling fluid.All the evidences of high temperature resistance indicate that the strong adsorption can enhance the thickness of hydrated shell and adsorption of clay particles in drilling fluid at high temperature.Such mechanism supplied the better way to design high-temperature resistant fluid loss additives for deep and ultra-deep oil and gas formation engineering.
查看更多>>摘要：Developing a green economy is key to achieving the 2030 Sustainable Development Goals.This paper uses the SBM-GML index,which includes non-desired outputs,to measure the trend of regional green economic efficiency changes and analyze the impact mechanism and realization path of industrial transformation on green economic efficiency.The research results show that advanced industrial structure has a positive influence on green economic efficiency nationwide,while energy utilization structure and energy utilization efficiency have positive partial intermediary effects in the influence path;industrial structure rationalization is also significantly positively related to green economic effi-ciency nationwide,and the mediating effect of energy utilization is positive.The impact of industrial transformation on green economic efficiency has regional heterogeneity,and the mediating effect of energy use also differs.Among them,the impact effect in the eastern region is basically consistent with the national sample,but is negative in the central and western regions.This paper proposes counter-measures in terms of adjusting the industrial structure,improving energy efficiency,and perfecting industrial and energy policies,which can provide theoretical and practical references for promoting the transformation and upgrading of regional industrial structure,optimizing energy utilization,and advancing the efficiency of the national and regional green economy.
查看更多>>摘要：Based on the HS 4-digit code trade data in UNCOMTRADE from 1995 to 2020,this paper analyzes the characteristics of the evolution of the global PG trade network using the complex network approach and analyzes the changes in its resilience at the overall and country levels,respectively.The results illustrated that:(1)The scale of the global PG trade network tends to expand,and the connection is gradually tightened,experiencing a change from a"supply-oriented"to a"supply-and-demand"pattern,in which the U.S.,Russia,Qatar,and Australia have gradually replaced Canada,Japan,and Russia to become the core trade status,while OPEC countries such as Qatar,Algeria,and Kuwait mainly rely on PG exports to occupy the core of the global supply,and the trade status of other countries has been dynamically alternating and evolving.(2)The resilience of the global PG trade network is lower than that of the random network and decreases non-linearly with more disrupted countries.Moreover,the impact of the U.S.is more significant than the rest of countries.Simulations using the exponential random graph model(ERGM)model revealed that national GDP,institutional quality,common border and RTA network are the determinants of PG trade network formation,and the positive impact of the four factors not only varies significantly across regions and stages,but also increases with national network status.
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