Operation Of Oil Pipelines Research Articles

Ultimate Axial Load Prediction Model for X65 Pipeline with Cracked Welding Joint Based on the Failure Assessment Diagram Method

Crack defects in the girth welds of pipelines have become an important factor affecting the safe operation of in-service oil pipelines. Therefore, it is necessary to analyze the factors affecting the safe operation of pipelines and determine the ultimate load during pipeline operation. Based on the failure assessment diagram (FAD) method described in the BS 7910 standard, the key factors affecting the evaluation results of the suitability of X65 pipeline girth welds are analyzed, and the effects of crack size, pipe geometry, and material properties on the evaluation results are investigated. The results indicate that the crack depth is more crucial to the safe operation of the pipeline than the crack length. While the effect of wall thickness is not significant, the misalignment can seriously aggravate the stress concentration. In general, the higher the yield ratio and tensile strength of the pipe material, the more dangerous the condition at the weld. The ultimate axial load that a crack-containing girth weld can withstand under different combinations of the above factors was determined. Furthermore, a data driven model via the optimized support vector regression method for the ultimate axial load of the X65 pipe was developed for engineering application, and the comparison results between the FEM results and the predicted results proved its accuracy and reliability.

Early warning method for overseas natural gas pipeline accidents based on FDOOBN under severe environmental conditions

The completion and operation of transnational long-distance oil and gas pipelines will not only alleviate shortages of oil and gas resources in China, but also lead to new development opportunities in the countries along their routes. However, the frequent occurrence of severe environmental disasters has led to several uncertainties regarding the long-term safe and stable operation of overseas pipelines, including pipeline fracture, fire, explosions, etc. In this paper, the fuzzy dynamic object-oriented Bayesian network (FDOOBN) theory was introduced to establish an early warning method for overseas natural gas pipeline accidents under harsh environmental conditions. Firstly, for the harsh environmental conditions (lightning, rain, and wind) at pipeline laying stations, accident scenarios under a single harsh environmental condition and the combination of multiple harsh environmental conditions were constructed. The object-oriented concept was adopted to modularize the station system and equipment, and the dynamic Bayesian network (DBN) model of each subsystem of the station was established. Then, the conditional probability parameters in the model were determined by the fuzzy mathematical method. The DBN model of each subsystem and the dynamic object-oriented Bayesian network (DOOBN) model of the entire station system based on the process flow of the station and the object-oriented concept were introduced in turn to establish the fuzzy dynamic Bayesian network (FDBN) model and the FDOOBN model respectively. The dynamic early warning system for station risk under harsh environmental conditions was finally realized. Finally, the prediction errors of environmental parameters, such as meteorological conditions, were introduced to modify the reliability of the model. The results show that compared with the traditional model, the error-corrected FDOOBN model not only has a better performance in simplifying the modelling process and fully integrating expert experience, but also has an increase in dynamic warning range, further improving the reliability of accident warnings.

Study on Safe and Optimized Operation of Crude Oil Pipeline

Study on Safe and Optimized Operation of Crude Oil Pipeline

Impacts of structural parameters of baffle plate on jetting pigging robot in the underwater oil and gas pipeline

During the operation of oil and gas transportation pipeline, condensate forms on the inner wall of the pipeline can lead to reduced transportation efficiency and potential safety hazards. Pigging is a widely used technology to remove deposition in pipelines. From the studies, it is found that the effect of pigging largely depends on the structure of the pig. The jetting pig is a new type of pigging device designed to prevent the blocking in the pigging process, and its baffles play an important role in guiding the jet fluid. In this paper, the impact of the structure of the baffle plate on the downstream flow field of the jetting pig is simulated and analyzed. The surface of the baffle plate is changed by using the curve of the contraction section of the water tunnel. It is found that the baffle plate structure has a great influence on the flow field at the outlet of the jet pig: (1) The increase of buffle area leads to the increase of turbulent kinetic energy and the decrease of velocity; (2) The rise of edge angle lead to the regular change of turbulent kinetic energy; (3) Different curved surfaces make the change of turbulent kinetic energy and velocity. The results in this study are helpful for a better understanding of mechanism of jetting pig and improved design of mechanical structure for improved pigging performance.

Parametric study on the trench designing for X80 buried steel pipeline crossing oblique-reverse fault

The safety operation of buried long-distance oil and gas pipelines has long been threatened by the active fault movement due to earthquake. In this paper, a three-dimensional numerical model of X80 buried pipeline crossing oblique-reverse fault was established considering the existence of pipeline trench and backfill soil. The values of parameters were derived from the Third West-to-East Natural Gas Transmission Pipeline Project in China. The strain development and deformation features of pipeline for local buckling and tensile fracture were obtained. The influence of various trench design parameters (pipeline burial depth, trench slope inclination, backfill soil type and thickness) on the failure process was discussed. Meanwhile, based on the failure criterion of buried pipelines, the critical fault displacements corresponding to different trench design schemes were studied. It is shown that the failure of pipelines can be avoided by reasonable trench design in the areas of low seismic intensity. Finally, the optimal scheme was further given to provide a reference for the seismic design of buried pipelines at oblique-reverse fault crossings.

GRAPHO-ANALYTICAL ANALYSIS OF OIL SPILLS WITH GRAVITY FLOW FROM MULTIPHASE PIPELINES

It is important to determine the amount of oil spilled in order to assess the losses and environmental impacts caused by accidents during the operation of oil pipelines. In the article it was proposed a grapho-analytical method based on the analysis of accidental oil spills from pipelines for the correct determination of the amount of hydrocarbons released into the environment in different modes. It has been proved that the assumption that the flow of oil into the environment due to the fact that the atmospheric pressure during the accident is not at the maximum point of the route profile, but at the accident site (hole) is not correct. At present, in normative documents and literature sources, unlike monophasic flows, there are almost no correct methods for estimating and calculating oil and gas spills for multiphase flows. Considering the importance of determining in which part of the pipeline the oil will leak in case of real accidents, the studies were carried out on the basis of the compacted profile of the pipeline. In the article, it was identified oil spills, as well as the fact that the gravity-flow regime is 3-5% of the volume of the pipeline and the conditions under which the complete unloading of the pipeline is possible. Keywords: oil spill, gravity-flow, hydrostatic pressure, vapor pressure, compacted profile, grapho-analytical method.

Data Analysis and Discussion on the Reliability of the Control Principle of a Sealed Crude Oil Pipeline

The current control principles of long-distance crude oil pipeline production and operation are all obtained by theory in the design stage, and lack of on-site actual operation verification. Based on the pigging data of the pipeline put into production in 2017, the simulation software SPS was used to establish the model. Based on the operating data of the pipeline in recent years, the control principles in the preliminary design are checked one by one to verify the reliability of the control principles and propose corresponding improvement suggestions for existing defects. The research results show that the initial control principle of the pipeline has two actual operation defects. One is the low setting value of the water hammer pressure relief valve in the BS station, and the second is the advance protection program error under the failure condition of the MD station; The simulation obtains the set value of the pressure relief limit of each station entry and exit under the principle of advanced protection, and the set value can be adjusted appropriately according to the pressure of the entry and exit pipelines of each station; the response time of each step of the control principle under different fault conditions is simulated, Provide optimization suggestions for some control principles. The above research results can minimize the failure results produced by the failure conditions under the premise of ensuring the effective control principle.

COMPARATIVE ANALYSIS OF CALCULATION METHODS FOR CENTRIFUGAL PUMPS TAKING INTO ACCOUNT LIQUID VISCOSITY IN ESTIMATING EFFICIENCY

In the main oil transport system of Russia, at present, the main indicator of the energy efficiency of the oil pipeline operation is the cost of electricity for pumping, while the main part of the cost of electricity falls on the drive of pumping units. To predict these energy costs, it is necessary to be guided by the planned pumping modes, as well as the actual parameters of the technical condition of the pumps, which directly depend on the actual efficiency of the mainline and booster pumping units. The planned pumping modes are known in advance, and it is not difficult to calculate the required amount of electricity. However, the actual cost of pumping can significantly exceed the planned value, since the actual efficiency of pumping units can be quite noticeably different from the rated values. Thus, an adequate assessment of the actual value of the efficiency of pumping units, and, first of all, of the main main-line pumps as the most energy-intensive equipment, is an urgent and difficult task that depends on a number of factors. The authors compared two methods for recalculating the passport values of the efficiency of main-line pumps: the method described in State Standard 6134-2007 «Dynamic Pumps. Test Methods» and method of N.Z. Aitova and L.G. Kolpakov. Comparison of the calculated values of the efficiency of pumps with the actual values of the efficiency of industrial pumps, which were determined by the actual values of the oil flow rate, pressure at the discharge and suction nozzles of the pump, the power consumption of the engine from the network was made. As a result, it was concluded that N.Z. Aitova and L.G. Kolpakov method, taking into account the speed coefficient, gives more reliable results of the efficiency assessment, which is confirmed by the actual data.

Experimental Study on Local Scour and Related Mechanical Effects at River-Crossing Underwater Oil and Gas Pipelines

Among the various geological disasters that threaten the safe operation of long-distance oil and gas pipelines, water-damage disasters are numerous and widely developed. Especially the pipelines crossing river channels or gullies are vulnerable to scouring hazards from storms and floods. A water-damage disaster physical model was established to investigate the characteristics of the riverbed scour profile and the pipeline force when the pipeline was buried at different depths under the condition of different particle size riverbed sediment. Results indicated that the equilibrium scour depth changed in a spoon shape with the gradual increase of the embedment ratio in general. The equilibrium scour depth formed by the fine sand riverbed was the largest, about 1.5 times the pipeline diameter. When the pipeline was half exposed, the clay riverbed was more resistant to the scour of the river than the riverbed of fine sand and very fine pebbles with a larger particle size. In the riverbed of three particle sizes, fine sand was more difficult to withstand the scour of the river. The scour profile formed by the sand bed around the pipeline and the force and deformation of the pipeline were related to pipeline location and riverbed sediment type. Results of this study might be useful for the safety warning and protection measures of underwater pipeline crossing.

Keystone Pipeline Rupture Investigation

The National Transportation Safety Board coordinated with the Pipeline and Hazardous Materials Safety Board to investigate the November 16, 2017, rupture of Keystone Mainline number 1 crude oil pipeline operated by TransCanada Oil Pipeline Operations, Incorporated. The rupture resulted from a fatigue crack that initiated from near-surface cracks associated with sliding contact damage at the top of the pipe and propagated to failure within 7.4 years of pipeline operation. The surface damage was characterized by photography, scanning electron microscopy, energy-dispersive x-ray spectroscopy, metallography, and dimensional analyses, and findings indicated the damage was produced by contact with a steel component likely from a vehicle used during the original construction after the pipeline was positioned in the trench.

Detection of oil losses in main pipeline damage

The enterprises and companies dealing with the oil transportation and operation of oil pipeline pay special attention to the improvement of methods for spill detection and prevention of oil losses. The improvement of the methods and means of failure prevention, development of reliable ways of pipeline protection from corrosion, as well as the methods of well-timed specifiction of damage point and loss elimination are necessary for efficient control of oil losses in the failures. The paper analyzes the reasons for occurring failures in the main pipelines. The graphic-analytical method for definition of damage point within the pipeline is presented as well.

CALCULATION FOR THE STRENGTH AND ENSURING THE OPERATION SAFETY OF PIPELINES WITH EXTERNAL CORROSION

Background The main oil and gas pipelines are mainly laid underground. Under the influence of the environment surrounding the underground pipeline, over time, there is a decrease in the protective properties of the outer insulation coating of the pipeline. In addition, for various reasons, mechanical destruction of the coating occurs in certain sections of the pipeline. These processes lead to external corrosion of the pipe wall in sections of underground pipelines. Corrosion is associated with a decrease in pipe wall thickness and an increase in the level of hoop stresses in them. As a result, the problem arises of assessing the strength of pipes and ensuring the safe operation of pipelines with external corrosion. At present, the installation of a metal sleeve on a pipeline in places with external corrosion has received a fairly widespread use. The coupling takes a part of the load from the operating pressure and thereby reduces the load and hoop stresses on the corroded section of the pipeline. At the same time, the coupling creates a local deformation stiffness under the operating pressure with a significant change in the stressstrain state of the pipeline. The stress-strain state of a pipe-wire with external corrosion and a sleeve installed on it depends on the geometric characteristics of the pipe and sleeve, as well as the residual pipe wall thickness after corrosion. Aims and Objectives Ensuring the strength of a pipeline with external corrosion repaired with the use of a coupling and the safe operation of oil and gas trunk pipelines based on a reasonable calculation of the geometric characteristics of the repair couplings. Results Calculation formulas were obtained and, on their basis, an assessment of the magnitude of stresses from the action of the working pressure in the walls of the pipeline and the coupling in the corroded section, as well as in the sections of the pipeline along the edges of the repair coupling outside of it, was carried out. Technical solutions are proposed to ensure the safe operation of a pipeline section with external corrosion, repaired using repair couplings.

Разработка эмпирической модели прогнозирования механических характеристик металла сварных соединений для оценки их работоспособности в процессе эксплуатации нефтепроводов и резервуаров

Разработка эмпирической модели прогнозирования механических характеристик металла сварных соединений для оценки их работоспособности в процессе эксплуатации нефтепроводов и резервуаров

Research on Oil and Gas Pipeline Operation Optimization Based on Improved Newton-Raphson Method

Oil and gas pipelines are the main channel to ensure national energy security and national economic development due to the safety and efficiency of the transportation coast. To achieve an optimal state of pipeline operation in terms of safety and efficiency is the crucial important issue throughout the life cycle of a pipeline system. However, the optimization problem of the pipeline network system is a typical Mixed Integer Non-Linear Problem (MINLP) which are extremely difficult to solve. An optimal solution to keep pipeline operated in most efficient state under the premise of safe operation is given in the paper by using the dynamical programming method. Firstly, the improved Newton-Raphson method is used to solve the discrete pipeline system, and the operating parameters such as temperature, pressure and flow of any section surface in the pipeline are obtained. The fluid parameter values of the each discrete nodes can ensure the safety of the pipeline. Based on this, the total energy consumption cost is set as the objective function, and the oil and gas pipeline operation optimization model is then established, and the dynamic programming method is used to solve it, so that it can obtain the optimal solution of the current working conditions in a reasonable computational cost. The actual example shows that the energy cost of the optimized operation scheme can be reduced by 6.8% compared with the pre-optimization scheme.

Обобщенный показатель эффективности использования насосного оборудования

The article is devoted to assessing the efficiency of operation of trunk oil pipelines. Based on the analysis, a generalized indicator of the efficiency of use of pumping equipment was obtained, which allows us to predict the ef-ficiency of operation of pumping equipment as a whole on the technologi-cal section of the pipeline. The article also presents the main components of the indicators.

Influence of accounting for thermodynamic processes on the processes of mixture formation during sequential pumping of petroleum products

In this paper, we study the processes of mixing when using the technology of transportation of light oil products-sequential pumping by direct contact. Modeling of mixing processes is carried out taking into account the influence of parametric and thermodynamic factors. For numerical modeling, a software package was developed that allows not only modeling and calculating the parameters of the oil pipeline operation in real time with subsequent graphical visualization, but also comparing them with real data processed by operators at production facilities.

Oil pipeline hydraulic resistance coefficient identification

The purpose of the study is to identify the hydraulic resistance coefficient of the main oil pipeline. Oil transportation through pipelines is the most efficient way to deliver oil from suppliers to consumers. The volume of transported oil depends on the pipeline hydraulic resistance. In practice, the hydraulic resistance coefficient is determined by the value of the Reynolds number and the pipeline internal surface roughness. The Reynolds number depends on the oil viscosity, which changes in a non-isothermal pipeline due to the heat exchange of the oil flow with the environment. The pipeline internal surface roughness changes during main oil pipeline operation. The identification of the pipeline hydraulic resistance coefficient is necessary for accurate calculations of the technological modes of the main oil pipeline. The SCADA (supervisory control and data acquisition) system determines the actual oil data (pressure, temperature, flow rate) along the main oil pipeline length in real time. Based on the results of the thermal-hydraulic calculations and the SCADA system, the hydraulic resistance coefficient identification method was built. The methodology was tested in the OPS-3—Koschagil, Severnye Buzachi—Karazhanbas, Prorva—Kultumiyev, Kassymov—Bolshoi Chagan main pipeline sections. The approbation results have shown sufficient accuracy in identifying the hydraulic resistance coefficient of oil pipelines. The obtained hydraulic resistance coefficient dependences were used to determine the oil transportation technological modes in industrial pipelines.

Study on the Operation Safety and Reliability of a Waxy Hot Oil Pipeline with Low Throughput Using the Probabilistic Method.

When the hot oil pipeline is running at a low throughput, it easily enters into an unstable condition, which seriously threatens the safety of the hot oil pipeline operation. In this study, the unsteady heat transfer and flow mathematical models for the hot oil pipeline system were established first by comprehensively considering the uncertainty of parameters during pipeline operation, such as the operating parameters (throughput and oil temperature), physical properties of crude oil (freezing point, viscosity, and thixotropic parameters), and environmental parameters (buried deep soil temperature and soil thermal conductivity). Then, the efficient Latin hypercube sampling (LHS) stochastic numerical algorithm was applied and further developed to quantitatively describe the operation safety of hot oil pipelines with low throughput in the form of probability. On the basis of the abovementioned research, the qualitative relationship between pipeline flowrate and friction loss is obtained. Finally, taking an actual crude oil pipeline as an example, the failure probabilities of the pipeline under different operating conditions were analyzed in detail. Combined with the target safety level of pipeline operation, the minimum allowable throughput of pipelines was determined. This study revealed the flow and heat transfer law of hot oil pipelines with low throughput and determined its operation safety and reliability under different operating conditions.

Исследование причин образования асфальтосмолопарафиновых отложений товарной нефти в условиях эксплуатации магистральных нефтепроводов

The results of investigations of the main causes and the most significant factors of intensification of paraffin deposition in main oil pipelines are presented. A comprehensive analysis of the composition and properties of commercial oils and their sediments was carried out, according to which phase diagrams of equilibrium of oil dispersed systems were obtained using the example of commercial oils from Bashkir fields. Based on the phase diagrams, a curve of wax oil saturation was constructed, the analysis of which confirms that the existing thermobaric conditions during the operation of main oil pipelines do not allow transporting oil without the risk of waxing. It was noted a special influence of the value of the temperature gradient in the near-wall zone and the imbalance of the ratio of high-molecular oil components in commercial batches formed in the process of joint pumping on the intensity of waxing of sections of oil pipelines complicated by deposits, which was confirmed by statistical data on the frequency of pigging. The regularities obtained in this way are proposed to be used as an express method for predicting complications associated with intensive waxing of main oil pipelines. In order to quickly assess the risks of waxing of sections of main oil pipelines, an indicator is introduced that characterizes the ratio of the content of solid paraffins to the total content of resins and asphaltenes of oil, called the criterion of instability of a commercial oil batch.

Methodology for studying the corrosion of material of oil pipelines operating in marshy soil

The main reason for the operation of oil pipelines is the corrosion of their materials. As a result of corrosion, the destruction of the pipeline, contributing to the leakage of oil, which pollutes the environment, accidents and disasters. The most corrosive areas are areas of high humidity, for example: swamps. In the Russian Federation, about 30 % of the transport network of oil pipelines passes through swampy soil. As the materials of oil pipelines, pipe steels are used, for example Steel of type 3 or 09Mn2Si. The article describes a method for studying the corrosion rate of pipe steels on a laboratory bench that simulates their operation in marshy soil. A comparison is made of the corrosion mechanisms of 09Mn2Si and Steel of type 3 steels in soils with a high content of hydrogen sulfide and the presence of microorganisms by empirical tests based on the above method. The results of gravimetric tests were evaluated and the conclusions were discussed.