The denoising effect of the negative pressure wave signal and the extraction of the feature vector are the key factors affecting the accuracy of the oil pipeline leakage detection. Aiming at the false negatives and false positives in pipeline leak detection, this paper proposed an improved fully integrated empirical mode decomposition algorithm (improved CEEMDAN) with adaptive white noise to preprocess the negative pressure wave signal. The CEEMDAN decomposition is performed on the negative pressure wave signal measured by the upstream and downstream pressure sensors of the pipeline to obtain a plurality of intrinsic mode functions (IMF). And the effective IMF component is selected according to the correlation coefficient principle of the dual channel sensor. An entropy⁃based eigenvector is proposed, and the energy entropy, kurtosis entropy and permutation entropy of the effective IMF component are input to support vector machine (SVM) to distinguish different working conditions. Through field data verification, the improved CEEMDAN combined with the entropy⁃based feature vector can effectively improve the accuracy of oil pipeline leakage condition identification, and has certain field application value.

In this paper, Changqing crude oil was emulsified under pressure in different dissolved gas environments (CO2, CH4, N2) by using crude oil emulsifier with pressure dissolved gas. The solubility (Rs) , water separation rate (fv), interfacial tension (γ), interfacial modulus of elasticity (εd), viscosity of dissolved gas crude oil (μ) and apparent viscosity of dissolved gas crude oil emulsion (μap) were measured by means of solubility measurement device, emulsion stability analysis device, interfacial tension tester and high pressure rheometer. The results show that the presence of oil⁃water interfacial film inhibits the migration of gas from the outer phase to the inner phase to a certain extent, so that the solubility of the dissolved gas oil emulsion is less than the solubility of the internal and external phases. Under the environment of dissolved CO2, because of the minimum interfacial tension between oil and water, the best emulsification effect is obtained, and the W/O emulsion droplets with pressure are the most compact. Under the environment of dissolved CO2, because of its minimum interfacial tension between oil and water, the smallest droplets are formed in W/O emulsion and the emulsifying effect is the best. At the same time, due to the elastic modulus of oil⁃water interface is the largest, the emulsion system is the most stable, and the viscosity ratio of emulsion system is the most obvious than that of crude oil system. In contrast, in the environment of N2 dissolution, the stability of the emulsion system is poor, and it is easy to demulsify.

After the shutdown of the waxy crude oil pipeline, the wax⁃crystals in the crude oil will gradually separate out when the temperature in the pipe falls below the wax precipitation point. According to the variation of viscoelasticity of waxy crude oil with temperature in temperature drop process, a method for dividing the temperature⁃drop stage during the shutdown of pipeline was put forward by using the relation of the storage modulus, loss modulus and loss angle with temperature. The temperature drop process was divided into three stages with the critical point of wax precipitation point and the temperature point when the storage modulus and loss modulus were equal (loss angle equaled 45 degrees). Taking the Huage pipeline as an example, FLUENT was used to describe the temperature drop process and calculate the solution. In addition, crude oil with different properties was selected to verify the method, and the rule of temperature drop in waxy crude oil pipeline was obtained.

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.

In this paper, the adsorption behavior of polyoctadecyl acrylate (POA) in model crude oil on the surface of nano⁃SiO2 particles modified by methyl was investigated by performing molecular dynamics (MD) simulations. The adsorption model of model crude oil including POA molecule on the surface of nano⁃SiO ₂ particles was constructed. The model crude oil consists of asphaltene, resin, aromatic hydrocarbons and alkanes. The surface of nano⁃SiO ₂ particles was modified with three different degree of methyl. Several parameters such as the adsorption energy, relative density distribution, the mean square displacement and radial distribution function were analyzed. The results show that the unmodified surface is firstly adsorbed by asphaltene of strong polarity while the surface of 100% methyl⁃modified is firstly adsorbed by n⁃alkanes. The surface of 50% methyl⁃modified particles is firstly adsorbed by aromatic hydrocarbons. The results also indicate that the surface of 50% methyl⁃modified particles is not only more conducive to the stable adsorption of POA molecules, but also conducive to POA molecules to form a better adsorption configuration. What’ more, on the surface of 50% methyl⁃modified particles, the interaction between POA molecule and C ₂₄H ₅₀ molecules is stronger, and the distribution of C ₂₄H ₅₀ molecules is more aggregated. Finally, the study of this paper provides a method for studying the mechanism of pour point depressants composed of polymer and inorganic nanoparticle and provides theoretical guidance for the experimental modification of nanometer particles in nano⁃hybrid pour point depressant.

The actual denoising effect of wavelet denoising methed was studied through pipe flow test apparatus, which simulated the actual pipeline leakage condition. The reason why small leak was not easy to be found was explained from two expects through timefrequency analysis of the leakage signal attenuation process. And the disadvantages of the most commonly used wavelet de-noising method to deal with small leakage signal were also discussed. On this basis, a new threshold function was established to improve the signal reconstruction accuracy and the advantage was analyzed mathematically. Next, a blind source separation algorithm based on maximum signal-to-noise ratio (SNR) was proposed, which integrated wavelet transform with blind source separation. By separating the known structural signal, the applicability of this method was illustrated, and the practical denoising effect and industrial application value of the fusion algorithm were verified.

Dissolution of CO ₂ in crude oil can change its rheological properties notably, which makes it widely used in the fields of oil displacement, viscosity reduction, transportation and so on. In this study, a pressurized stirring-viscometric equipment was designed based on the stirring viscometry theory, and the corresponding viscometric method was also proposed, so that the viscosity of CO ₂ heavy oil mixture could be determined under the simulation conditions of pipeline transportation. On the basis of this equipment and method, the effects of pressure, shear rate and temperature on the viscosity of CO ₂ heavy oil mixture were probed. It was found that the viscosity of CO ₂ heavy oil mixture decreased exponentially with the increase of pressure. The viscosity of heavy oil system can be greatly reduced by dissolving gas pressure of 2 MPa. Meanwhile, the shear thinning feature became more obvious with increasing pressure of CO ₂. Moreover, the viscosity reducing rate became greater with decreasing temperature at the same pressure. The results of this study provide technical support for the feasibility of transporting viscosity-reduced heavy crude oil by CO ₂.

Based on different proportions of CO2 and CH4 mixture gas source, the experiment pretreated Changqing oil by using selfmade saturated dissolved gas crude oil processing device under simulated stratum conditions, and then saturated dissolved gas crude oil was got through step by step depressurizing under gathering and transportation conditions (0~3.5 MPa). Crude oil's solubility (Rs), volume factor (Bo), condensation point (TZ), viscosity (μ) and yield value (τy) were studied by using highpressure equipment, which could measure properties of live oil, and highpressure rheometer. The results showed that Rs and Bo increased with the increase of pressure. As the temperature increased, Rs decreased and Bo increased. When experiments were conducted with the same temperature and pressure, Rs (CO2) was the double of Rs(CH4), and the Rs of mixture gas was between the two formers, and the crude oil got better expansion effect with the mixture gas. Among mixture gas, molar ratio of 9∶1 (n(CO2)/n(CH4)) had the best expansion effect, and such mixture gas had best improvement of crude oil's condensation point, viscosity and yield value.

A dynamic wax deposition model for Jienuo crude oil was established through laboratory wax deposition experiments. With safe operations ensured, taking the sum of average daily power and pigging costs（average daily costs of pipeline operation） as the objective function, a pigging frequency model for unheated oil pipelines was developed. Based on the operation data of Linyi-Zhaozhaizi stations in Linyi-Puyang pipeline, the influence of outlet temperature, throughput and soil temperature on optimized pigging frequency were analyzed. The results show that the average daily costs of pipeline operation will be increased while the pigging frequency will be extended with decreasing of the outlet temperature. The average daily costs of pipeline operation will be increased while the pigging frequency will be shortened with rising of the throughput, and the average daily costs of pipeline operation will be decreased first and then increased while the pigging frequency will be extended with increasing of the soil temperature.

        Given the frequent accidents attributed to abnormal pressure fluctuation and the less effectiveness of preventive measures of complex pipe network, the FTA method of graph theory was applied to solve this problem. Induced mechanism of abnormal pressure fluctuations was interpreted and the FTA model of pressure abnormal fluctuations in complex pipeline network was firstly proposed and established in this paper. An imported crude oil pipe network was taken as a case study by using the Delphi method and fuzzy mathematics theory to solve the model. Results agree well with the actual statistics. Then K-means clustering method was carried on to analyze the three importance of typical basic events and the three-tier structure of the abnormal fluctuations is proposed using the DTA method, which lies a theoretical basis for the analysis on abnormal events as well as the optimization of the prevention and control measures. This paper mainly offers a new research idea in the field of operation security and integrity management of the large, complex pipe network especially when the historical data is far from complete.

It is difficult to manage gathering & transportation pipelines because of their complicate operating conditions. Based on the Chuanping 4623 gathering & transportation pipeline in Changqing oilfield and its operating parameters. The appropriate models, such as flow pattern model, liquid holdup calculation model, pressure drop calculation model and wax deposition model, were selected by comparative analysis. Then, the variation of operating pressure, temperature, liquid holdup, effective inner diameter, gas/liquid superficial velocity and wax deposition rate with pipe distance and operating time was analyzed by programming and calculating the models. The simulating results showed that the wax deposition rate, pressure, temperature, liquid superficial velocity and liquid holdup reduced, while gas superficial velocity increased with the increasing of pipeline length (except for the first 60 meters). The wax deposition rate, temperature, gas/liquid superficial velocity increases, the pressure and liquid holdup decreased at the same node with the increase of operating time within 36 operating hours.