Main pipeline pressure testing standards between China and Russia are introduced,and the differences them are analyzed in detail,including the pipe section length,testing medium,strength testing pressure,tightness testing pressure and pressure holding time,process piping pressure testing of gas or oil stations,leakage inspection methods of process piping pressure testing,piping pressure technology under 0 ℃,mandatory pressure testing(re-testing and periodic tesing),piping pressure monitoring,safety measures of pressure testing and environment protection.Finally,Recommendations to draw up and revise the standards about the pipeline constructed in the permafrost are given.
Laser Raman spectroscopy needs neither high-purity carrier gas nor the separation of sample gas,and can simultaneously analyze multiple gas components with a fast speed of measurement,a high efficiency of gas analytic test and even a low analytic cost.That is why it is widely used in material science,petroleum industry,chemical industry,environmentally-friendly biotechnology,medical field,geological studies,etc.However,due to the small scattering area and the weak scattering strength of gas molecules,the application of Laser Raman spectroscopy to natural gas component analysis is still at the laboratory research stage,and its accuracy and reproducibility are to be highly improved.In view of this,through the analysis of such application prospect,it is presented that the integration of laser light source,spectroscopy surface-enhanced Raman scattering and fiber probe technologies will significantly improve the intensity of Raman scattering light,as a result,to effectively improve the test sensitivity,reproducibility and accuracy of natural gas component analysis.On this basis,it is also predicted that a satisfactory Laser Raman analyzer will be possibly developed to achieve instant and simultaneous analysis of natural gas components.Apart from that,with this analyzer,we can also achieve the simultaneous analysis of gas composition,harmful substances and other impurities.And that will make it possible for Laser Raman Spectroscopy to be widely applied to natural gas component analysis.
The fracture diagnostic technology of micro-seismic mapping is widely applied in the U.S.shale gas wells.A number of research results from abroad show that the larger the stimulated reservoir volume,the better the well performance;fractures are no longer shaped in a two-wing structure but in a complex network,from which a technical term of stimulated reservoir volume(SRV) has come into being.However,present studies abroad are still at the level of how to improve the SRV.In order to make the SRV being correctly and widely accepted in China,we introduce a new concept of volume fracturing,give its definition in both broad sense and narrow sense,and put forward the reservoir condition,key technical points,and main techniques of forming fracture network.Moreover,based on a comparison analysis of traditional fracturing and volume fracturing,a net pressure determination equation is studied for shear fracture propagation,and their difference in seepage mechanism is emphasized.The shortest-distance seepage all-round from matrix to fracture is first presented herein.Finally,breaking with the traditional way of avoiding the fracture interference,the induced stress model of a single cluster fracture is established to obtain the optimal fracture spacing,providing guidance to the multi-stage and multi-cluster fracturing design and laying the foundation for technical development,completion and wide application of volume fracturing in China.
Numerical solution of the wave equation is one of core technologies for wave equation forward modeling,reverse time migration and full waveform inversion.In this paper,I review finite difference for numerical solution of wave equation and absorption boundary conditions,and discuss the hybrid absorption boundary conditions and different finite difference methods such as the time-space domain dispersion-relation-based finite difference, the adaptive variable-length spatial finite difference,the optimized finite difference.The paper introduces applications and progresses of these methods in reverse time migration and waveform inversion.
This article focuses on comparing among the first-order accuracy Hudson model,the second-order accuracy Hudson model,the Schoenberg model,the Kachanov model and the Eshelby-Cheng model.The paper summarizes the expressions of elasticity coefficient of the different models.Elastic wave equation numerical simulation is used to simulate propagation characteristics of waves in these fracture models respectively for dry fracture and water-filled fracture with different fracture density and fracture aspect ratio.And wave field snapshots and the phenomenon of shear-wave splitting from the simulation are analyzed.The following observations are obtained from the study: The fracture density affects the anisotropy feature of the P-and S-waves and the fracture fillings influence the anisotropy of the medium;while the fracture aspect ratio and the fracture fillings impact on the propagation characteristics of shear waves.Shear-wave splitting changes significantly with the increasing crack density,but the fracture aspect ratio and the fracture fillings have little effect on shear-wave splitting.
The three current technologies for activated sludge reduction include uncoupling technology,predaoriness on bacteria and lysis-cryptic growth. Minimization technique on the basis of lysis-cryptic growth sludge ozonation has good treatment effect and application prospect. This paper emphasizes the discussion on mechanism of sludge ozonation and its influence factors. Considering the application of ozonation in the sewage disposal plant,the effect of sludge disintegration after ozonation on biological sewage treatment is discussed.
Silica-dispersed NiMo hydrodesulfurization catalysts were synthesized by the deposition-precipitation method. For comparative purposes,bulk NiMo catalysts were obtained by co-precipitation.The silica-dispersed NiMo catalyst had highly active metals content.Silica was employed to disperse active metals for full utilization of active components.The BET analysis showed that the silica-dispersed NiMo catalysts had a high surface area(147.0m~2/g) and pore volume(0.27 mL/g),whereas the bulk NiMo catalysts exhibited a very low surface area(87.5 m~2/g).Transmission electron microscopy results proved that the active components were dispersed on the SiO_2 substrate.X-ray diffraction patterns of the silicadispersed NiMo catalyst and the bulk NiMo catalyst were indexed to NiMoO_4.The hydrodesulfurization activity of silicadispersed NiMo catalysts was much higher than that of reference catalysts and could be up to twice greater than those of commercial NiMo alumina-supported systems per gram of catalyst.The activity testing results also demonstrated that the silica-dispersed NiMo catalyst was an effective hydrodesulfurization catalyst.
Aiming at the low-resolution and instability of crosswell seismic travel-time tomography,a total variation regularization waveform inversion(TVWI) method for crosswell seismic data was proposed. High resolution velocity distribution between two wells can be obtained by TVWI using crosswell seismic data.TVWI is based on Gauss-Newton wave equation inversion,which converts the velocity calculation of crosswell seismic data into wave equation inversion and achieves the wave equation inversion through minimizing the difference between the calculated seismic data and observed data. The local linearization step by step iteration method is used to optimize the nonlinear objective functional.The total variation constraint item is added to the wave equation inversion objective functional, to improve the stability and the resolution of inversion.A complex velocity model was designed to verify the validity of TVWI method,and the result shows that for the different given initial velocity, all the inversion has relatively high accuracy.The initial velocity model which has large difference to real velocity was selected to discuss the dependence of TVWI method on the picking of initial value.Inversion result shows that it is not depend on the picking of initial value,but if the initial value is not well picked,the iteration times and computation cost will increase.Finally,anti-noise ability of TVWI method was tested,and it was proofed to be strong ability.
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