Buried Oil Research Articles

Corrosion reason analysis and countermeasures of buried oil unloading pipeline in an oilfield

The material, corrosion morphology and characteristics, as well as the compositions of corrosion products of a 20# steel unloading pipeline were studied using on-site C-scan detection, laboratory corrosion morphology analysis, material metallographic analysis, chemical composition analysis and tensile testing. The uniform corrosion and pitting behavior of 20# steel were studied using a high temperature and high pressure autoclave under conditions of 50 °C and CO2 partial pressure of 0.05 MPa, 0.1 MPa, and 0.2 MPa, respectively. The microstructure and composition of the surface and cross-section corrosion product film were analyzed by SEM. The results show that the uniform corrosion rate of 20# steel increases with the increase of CO2 partial pressure. When the CO2 partial pressure reaches 0.2 MPa, there are a large number of corrosion pits on the surface of the sample, and the maximum local corrosion rate reaches 1.8719 mm/a. The corrosion product film has a multi-layer structure, with a surface layer of FeCO3 corrosion product films and an inner layer of (Ca, Mg)CO3 deposition layer. There are obvious corrosion pits at the interface between the corrosion product film and the substrate locally. The severe thinning of the on-site pipeline wall is mainly caused by CO2 corrosion. The defects of the corrosion product film and the deposition of scale layer accelerate local corrosion.

Prediction of external corrosion rate for buried oil and gas pipelines: A novel deep learning method with DNN and attention mechanism

Buried pipelines is easily subjected to external corrosion affected by complex underground environment, such as soil resistivity, pH, dissolved ion concentration, water content and coatings condition. Therefore, external corrosion rate prediction is essential to ensure pipelines intrinsic safety. Generally numerous researches focused on mathematical models and degradation analysis are limited to considering comprehensive corrosion factors. In this work, a novel proposed deep learning method involves a deep neural network (DNN) and attention mechanism which has good robust generalization ability. DNN was used to predict external corrosion rate of buried pipelines with extracting corrosion characteristics data, and attention mechanism is carried on weighting operations of corrosion factors furtherly. The results show that main controlling factors are pipeline age and soil bulk density, sulfate ion concentration and redox potential have less effect by analyzing external corrosion factors dataset, and data reduction and standardization of DNN-attention mechanism model are carried out. The external corrosion rate value predicted by the DNN-attention mechanism model is the closest prediction with the real truth, which the evaluation index root mean square error (RMSE) is 0.0064, and prediction accuracy is 91.91 % compared with convolutional neural network (CNN), CNN-residual, DNN. It proves that it is reasonable to predict pipeline external corrosion rate using DNN-attention mechanism based on publicly pipeline corrosion dataset.

Acoustic scattering characteristics of underwater buried oil pipeline

With the development of offshore oil resources, subsea oil pipelines have emerged. As a fast, economical, and safe way to transport oil resources, subsea pipelines are known as the “lifeline” of offshore oil projects. However, the detection of submarine pipelines is very difficult due to the complex underwater environment. One of the mainstream methods to detect submarine pipelines is the employment of sonar. Hence, the acoustic scattering characteristics of submarine pipelines play an important role in detecting themselves. In this study, the acoustic scattering model of the buried pipeline is established using the finite element method, and the scattering mechanism of the buried pipeline is analyzed. The effects of different frequencies, grazing angles, burial depth, and other factors on the acoustic scattering characteristics of the buried pipeline are investigated, providing the reference significance for detecting submarine pipelines.

Retracted: Prediction of Chemical Corrosion Rate and Remaining Life of Buried Oil and Gas Pipelines in Changqing Gas Field

Retracted: Prediction of Chemical Corrosion Rate and Remaining Life of Buried Oil and Gas Pipelines in Changqing Gas Field

Stress corrosion cracking behavior of buried oil and gas pipeline steel under the coexistence of magnetic field and sulfate-reducing bacteria

Magnetic field and microorganisms are important factors influencing the stress corrosion cracking (SCC) of buried oil and gas pipelines. Once SCC occurs in buried pipelines, it will cause serious hazards to the soil environment. The SCC behavior of X80 pipeline steel under the magnetic field and sulfate-reducing bacteria (SRB) environment was investigated by immersion tests, electrochemical tests, and slow strain rate tensile (SSRT) tests. The results showed that the corrosion and SCC sensitivity of X80 steel decreased with increasing the magnetic field strength in the sterile environment. The SCC sensitivity was higher in the biotic environment inoculated with SRB, but it also decreased with increasing magnetic field strength, which was due to the magnetic field reduces microbial activity and promotes the formation of dense film layer. This work provided theoretical guidance on the prevention of SCC in pipeline steel under magnetic field and SRB coexistence.

Research and Application of Digital Monitoring System for Pulse Current Cathodic Protection of Oil Pipeline

The transportation of crude oil mainly relies on long-distance buried oil pipelines, which are generally made of steel pipes. Oil leakage often occurs due to corrosion, causing environmental pollution and unsafe accidents. A digital monitoring system for pulse current cathodic protection of oil pipelines was studied, with a focus on the composition and functions of the digital monitoring system for pulse current cathodic protection of oil pipelines. In 2022, the system was applied on two oil pipelines in Tongzhai operation area of the Third Oil Production Plant of Changqing oil field. The system realized the pulse current cathodic protection of oil pipelines to prevent corrosion. At the same time, it can digitally monitor the pulse current cathodic Conservation status status and adjust the working state of the potentiostat, and cooperate with the pulse current cathodic protection monitoring expert system for auxiliary analysis, which has received good economic and social benefits.

Analysis of the Spatial Distribution Characteristics of Crude Oils with Different Freezing Points and the Genetic Mechanism of High-Freezing-Point Crude Oils in the Dongying Sag.

The freezing point of crude oils is an important factor affecting the process of exploration, development, and transportation of crude oils. In the Dongying Sag, the freezing point of crude oils varies greatly in space, and high-freezing-point crude oils have been found in many structural belts. The freezing point of crude oils in the Dongying Sag is generally high, ranging from -40 to 80 °C. The distribution of high-freezing-point crude oils in the Dongying Sag is scattered, and they have been found at different depths, layers, and structural belts, with relatively more occurrences in specific areas. Based on the relationship between the wax content and the resin + asphaltene content, the high-freezing-point crude oils in the Dongying Sag can be classified into three types (type A, type B, and type C). Type A, type B, and type C high-freezing-point crude oils are mainly found in the gentle slope zone, depression zone, and uplift zone, respectively. The contents of wax and resins + asphaltenes in crude oils are the key factors controlling the freezing point of crude oils in the Dongying Sag. Oil source correlation using biomarkers and n-alkane carbon isotopes demonstrates that different types of high-freezing-point crude oils are generated from different source rocks, indicating that the source of crude oils is not the only factor controlling the freezing point of crude oils. The hydrocarbon-generating parent material of hydrocarbon source rocks developed in different depositional environments of the Dongying Sag is generally characterized by the dominance of bacteria and algae and is supplemented by terrestrial higher plants. This lays the material foundation for the formation of waxes during the maturation of hydrocarbon source rocks. The change of temperature and pressure conditions during the process of oil expulsion from source rocks and migration in the carrier bed will lead to phase fractionation and composition changes of oils, thus forming type A freezing point crude oils in the slope zone and type B freezing point oils in the depression zone. The increase in resin and asphaltene content caused by biodegradation and water washing in shallower buried oil reservoirs is the reason for the formation of type C high-freezing-point crude oils. The research results indicate that the organic matter composition and hydrocarbon alteration during migration and accumulation jointly control the formation of high-freezing-point crude oils in lacustrine basins. The extensive input of terrestrial organic matter into the source rocks of the lacustrine basin laid the foundation for the formation of high-freezing-point crude oils, and the migration fractionation and biodegradation of the crude oils further promoted the formation of high-freezing-point crude oils.

Identifying potentially dangerous areas of frost heaving and surfacing of the buried oil pipeline

This scientific study aims to automatically identify potentially dangerous areas of frost heaving and surfacing of a buried oil pipeline using the geological description of soil profile. The geological description of soil profile along the proposed route of a pipeline entails the study and identification of various layers of soil to determine the soil's suitability for pipeline installation and support. Enriching the geological description of soils in the first stage was achieved by creating a family of parameters that characterize the presence of water in two states and the interaction of the buried oil pipeline with soil layers. In the second stage, missed and erroneous soil parameters were restored by searching for similar patterns along the route of the pipeline using the enriched geological description of soil profile. Afterward, the selected areas of frost heaving and surfacing were ranked by potential danger in the third stage. The algorithm developed was shown to reduce the risk of damage to the oil pipeline and enrich the geological description of soil profile without additional field works. The results of the study allowed for the allocation of potentially dangerous areas where frost heaving and surfacing occur. The methodology described in the study can be applied in the midstream segment of the oil and gas industry to minimize the risk of pipeline damage.

Assessment of reliability for subterranean corroded pipelines in cold regions using Monte Carlo method and BP neural network

Due to the complexity and instability of the environment in which the buried oil pipeline is located in cold regions, the corrosion of the outer wall of the pipeline often occurs, and the corrosion poses a serious threat to the safety of the pipeline. In order to ensure the safe operation of buried oil pipelines, it is particularly urgent to study the reliability of operating pipelines. In this paper, the external temperature field and soil effect were taken into account, and the finite element method was used to calculate and analyze the results. The fitted formula which can predict the failure pressure of buried corroded pipeline was obtained. After that, the reliability of buried corroded pipelines was studied by using Monte Carlo method and BP neural network. The results show that the fitted formula for predicting the failure pressure of pipelines is more accurate than traditional code. The corrosion depth has the most significant impact on the reliability of pipelines, being 1.85 times that of the corrosion length. The impact of corrosion width, burial depth, frost-heaving rate, and length of the frost-heaving section on the reliability of corroded pipelines is relatively small. The frost-heaving section within 5000 mm can play a certain positive role in the reliability of corroded pipelines.

Identification of ground spilled oil of buried pipeline based on laser absorption spectroscopy: Numerical investigation and experimental verification

The ground diffusion characteristics of buried oil pipeline after leakage and the laser optical transmission mechanism of surface oil film are the basis of spectral detection technology. Based on the computational fluid dynamics to solve the diffusion equation of multiphase flow in porous media, the leakage law of oil under different soil porosity is analyzed in two dimensions: surface diffusion diameter and oil film thickness. TracePro optical simulation is used to study the absorption and reflection patterns of laser at the oil-gas interface, and validation experiments are carried out based on the tunable diode laser absorption spectroscopy method. The results show that oil is easily accumulated on the ground surface with larger soil porosity and in the depressions of the ground surface. When the oil film thickness is greater than 2 mm, the laser cannot transmit the oil layer and the received light intensity is only provided by the mirror reflection at the oil-gas interface. The mechanism of laser detection of oil leaks is the spectral absorption of volatile alkane gases in the upper layer of the oil film by a laser of a specific wavelength.

Experimental Study on Mechanical Response of Oil and Gas Pipelines under Ground Subsidence

At present, accidents of buried pipelines caused by localized ground subsidence are reported frequently. Understanding the mechanical response of pipe soil during subsidence is of great significance to the safe operation of buried pipelines. This paper studies the stress state of buried oil and gas pipelines and their surrounding soil through a series of large-scale model tests in the process of localized ground subsidence. The experiment results show that during the process of subsidence, the axial and hoop strain of the pipeline increases with the expansion of the subsidence area and the subsidence amount. The subsidence amount has a relatively greater influence, and the distribution characteristics of the pipeline strain present obvious regional characteristics. The earth pressure around the pipe shows different changes in the process of subsidence, among which the earth pressure on the upper part of the pipe is the main one. The research results can provide a certain reference for the design and calculation of oil and gas pipelines under foundation settlement.

Numerical Study on the Optimal Thermally Affected Region of a Buried Oil Pipeline.

Crude oil pipeline transportation is usually a closed process under a certain depth of burial, and the condition of oil in the pipeline changes with the continuous decline of temperature during the transportation process. The safety and energy consumption of pipeline transportation are closely related to the accurate prediction of oil temperature. It is a popular technique to use the thermally affected region to overcome the problem of an unclosed calculation domain caused by the semi-infinite soil around the pipeline. However, there is no clear and unified guidance on the thermally affected region at present, and improper region size may lead to a loss of the accuracy of the pipeline system. Therefore, our study answers two questions about the optimal form of the thermally affected region and its economic scope of application. The coupled solution of heat transfer and flow in a tridimensional numerical model is carried out, and the thermodynamic influences of the geometric shape and range of the thermally affected region on the buried pipeline system are investigated. The results show that the rectangular region is more suitable for the modeling of buried oil pipelines, and a region with 16 m width and 9 m height is recommended for the conventional case.

Dynamic monitoring of leaking oil diffusion in porous media: An improved method assisting buried oil pipeline condition assessment

The environmental pollution caused by buried oil pipeline leakage is a typical non-aqueous phase liquid (NAPL) pollution accident. Therefore, it seems more reasonable to assess the condition of buried oil pipelines considering the potential contamination range. The law of oil diffusion in porous soil is very important for the safety management of buried pipelines and the remedy of leakage accidents. This paper proposes a dynamic observation technique of NAPL in porous media for buried oil pipeline leakage. A quantitative relationship between the diesel saturation and color components is established based on the theoretical analysis combined with 21 groups of dyed diesel experimental results. The accuracy of the observation technique is verified by a quantitative analysis of a series of discrete point samplings and a comparison of diesel volume in a diesel diffusion experiment. The results show that the combination of a specified saturation boundary and the color components S and I can effectively track the diesel diffusion fronts. The relative error between the calculated cumulative volume and the injected cumulative volume fluctuates around 5% at different times. This improved technology can effectively make up for the limitation of the traditional light transmission visualization (LTV) under low-intensity light and promote the study of NAPLs diffusion characteristics. Furthermore, the dynamic observation technique of NAPL in porous media for buried oil pipeline leakage monitoring can make a significant contribution to the improvement of the level of buried pipeline leakage accidents and remediation.

Prediction of Chemical Corrosion Rate and Remaining Life of Buried Oil and Gas Pipelines in Changqing Gas Field

Green synthesis and metal oxide composites have attracted much attention from researchers of industry and academia. As a typical application of green synthesis and metal oxide composites, the continuous change of industrial technology and the continuous improvement of the social and economic level, the demand for oil and gas are also increasing. However, the spatial gap between the place of origin and the place of demand for oil and gas resources is large, so the long-distance oil and gas pipeline came into being. However, under the action of time, coupled with the corrosion effect of the soil due to deep burial, some pipelines have serious aging and corrosion phenomena. Therefore, in order to give corresponding guarantees for economic development, we need to conduct in-depth research and analysis of the corrosion of oil and gas long-distance pipelines and give effective solutions. In this paper, the corrosion rate prediction of buried oil and gas pipelines is studied in Changqing gas field. By improving the inertial weights and learning factors of the traditional particle swarm algorithm, the parameters of the generalized regression neural network are optimized and selected, and the corrosion rate prediction model of buried pipelines is finally constructed. Comparative analysis with other swarm intelligence algorithms shows that the improved particle swarm algorithm has stronger convergence ability and higher prediction accuracy than the BP model and SVM model. In addition, based on the detection data collected at the site of the gathering and transportation pipeline in Changqing gas field, this paper uses the extreme value distribution theory and the local corrosion progress formula to establish a prediction model for the residual life of corrosion of buried pipelines. The model established in this paper can effectively determine the risk pipe segment of buried pipeline and provide a decision-making basis for pipeline management departments. The work provides an important application guidance to green synthesis and metal oxide composites.

Quantitative Study of Sensor-Pipe Distance in Noncontact Magnetic Detection of Ferromagnetic Pipelines

Non-contact magnetic detection technology has great application potential in buried oil and gas pipelines due to the non-contact online detection of pipeline damage. However, the non-contact magnetic detecting signal is affected by the distance between the magnetometer and the ferromagnetic pipeline, leading to missed detection of pipe defects. It is essential to calibrate the detection height for the non-contact magnetic detecting signal. In this paper, the spatial analytical model of non-contact magnetic signals above ferromagnetic pipelines is established. Then, a quantitative variation law of non-contact magnetic detecting signals is obtained under different pipe diameters and internal pressures. Next, a signal calculation model based on the detection height h is established. A detection height correction method is proposed to eliminate the influence of detection heights on the magnetic detecting signal. An experimental investigation is carried out to validate the accuracy of the numerical calculation results and correction method. The results indicate that the magnetic detecting signal has a second-order exponential relationship with the detection height h within 0.1 m - 2 m. The average error of the signal correction model is 6.37%. The modified magnetic detecting signal via the signal correction method can reflect the damage status of ferromagnetic pipelines.

Prediction of corrosion failure probability of buried oil and gas pipeline based on an RBF neural network

Risk assessment is critical to ensure the safe operation of oil and gas pipeline systems. The core content of such risk assessment is to determine the failure probability of the pipelines quantitatively and accurately. Hence, this study combines the MATLAB neural network toolbox and adopts an Radial Basis Functions (RBF) neural network with a strong non-linear mapping relationship to build a corrosion failure probability prediction model for buried oil and gas gathering and transmission pipelines. Based on the hazard identification of pipeline corrosion failure, the model summarizes the causes of corrosion failure and determines the input and output vectors of the neural network based on the fault tree. According to the selected learning samples, through the design and training of network parameters, the RBF neural network that can predict the system failure probability is finally obtained. Taking the failure probability of 30 groups of high-pressure gathering and transmission pipelines of gas storage as an example, the capability of inputting the probability of the bottom event and outputting the probability of the top event is demonstrated through training data. Our results show that the calculated failure probability based on the fault tree analysis model is consistent with the predicted failure probability based on the RBF neural network model. Hence, the RBF neural network model is shown to be reliable in predicting the corrosion failure probability of buried pipelines.

Study on the Interference Law of AC Transmission Lines on the Cathodic Protection Potential of Long-Distance Transmission Pipelines

Through inductive coupling, AC transmission lines can generate large amounts of voltage to buried oil and gas pipelines in areas with common corridors, posing a threat to the cathodic protection effect of pipelines. Therefore, this paper investigates the effect of AC transmission lines on the cathodic protection of long-distance pipelines through inductive coupling. COMSOL Multiphysics finite element simulation software is used to calculate the distribution of cathodic protection potential of long-distance pipelines under different voltage levels, parallel spacing, conductor-to-ground height, conductor arrangement and pipeline burial depth for normal operation of AC transmission lines. Comparison and analysis of the AC transmission line on the pipeline cathodic protection potential interference law is conducted. The results show that: 1. AC transmission lines cause serious electromagnetic interference with the pipeline cathodic protection system, which will cause the pipeline cathodic protection potential to shift out of the effective protection area. 2. The maximum value of the induced voltage of the pipeline will appear at the two ends of the pipeline, and the induced voltage of the pipeline in the middle position is 0. 3. The shift of the pipeline cathodic protection potential increases with the increase of voltage level and decreases with the increase of parallel spacing, conductor height and burial depth. The pipeline cathodic protection potential shift is highest when the wires are arranged horizontally and lowest when they are arranged in an umbrella shape.

Study on the Force Characteristics of Aviation Fuel Pipeline under Soil Occupancy Load

Aviation fuel pipeline is one of the important lifelines of aviation coal supply at airports. When crossing a densely populated area, the aviation oil pipeline will inevitably be disturbed by natural and human factors, such as unreasonable soil accumulation near the pipeline, when the soil load is too large, the weak foundation soil will produce different degrees of deformation, the pipeline is subjected to various complex force forms under the action of soil displacement, resulting in a series of damage to the pipeline, and eventually cause pipeline safety accidents, resulting in the loss of people’s lives and property and environmental damage. Therefore, studying the force characteristics and safety prevention and control countermeasures of buried aviation oil pipelines under the surrounding soil pile occupation pressure has a very important guiding role and practical value for ensuring the operation safety of the airport lifeline. In this paper, the stress and deformation of buried oil and gas pipelines under the action of surrounding soil piles are analyzed, the influencing factors of buried oil and gas pipeline stress under the action of soil accumulation are analyzed by finite element software ABAQUS, the detailed stress analysis of the pipeline is carried out,and the finite element simulation method is verified by on-site large-scale stacking tests.

Vibration safety evaluation and vibration isolation control measures for buried oil pipelines under dynamic compaction: A case study

As a common treatment method to improve the bearing capacity of soft soil sites, the strong impact vibration generated by dynamic compaction (DC) has adverse effects on the surrounding environment and adjacent structures. In this paper, a series of in-situ tests were conducted to evaluate the vibration safety of adjacent buried oil pipelines under DC shock. The vibration responses and attenuation rules of the site were analyzed. Meanwhile, a numerical method was employed to discuss and determine the minimum tamping distance and rational parameters for isolation trench. Furthermore, the vertical peak vibration velocity index was used to evaluate the vibration safety of the pipeline under DC load. The results show that the vibration response of the site is manifested as vertical vibration and horizontal vibration, while the vibration response of the buried pipeline is dominated by vertical vibration. The empty trench can block the propagation of vibration waves effectively, in which the depth and its distance to the ramming point are the main factors affecting the vibration isolation effect. The vibration isolation effect of the trench increases with the increase of trench depth and the decrease of the distance from the tamping point. The study proposed parameters for an empty trench with a depth of 5 m and a safety distance of 5 m from the compaction point for the final ground treatment scheme. Good results have been achieved in engineering practice. The analysis results provide new ideas and references for promoting the application of underground pipeline vibration protection technology in DC ground treatment.

Shake table test and numerical analysis of the seismic response of buried long-distance pipeline under longitudinal non-uniform excitation

To investigate the seismic response characteristics of buried pipelines under longitudinal non-uniform seismic excitation, a three-dimensional finite element overall analysis model is established on finite element analysis software based on the shaking table test of buried oil and gas pipelines under longitudinal non-uniform excitation. The calculated results are compared with the experimental analysis results to evaluate the correctness and reliability of the established model. The acceleration response, strain response, and displacement response of buried oil and gas pipelines and surrounding soil under longitudinal traveling wave excitation at different seismic intensities are compared and analyzed using finite element models to supplement the test conditions. The test and analysis results show that the longitudinal displacements at each measurement point under longitudinal non-uniform excitation follow the same pattern except for differences in displacement magnitude and the vibration pattern of the tube and soil when the peak input acceleration reaches 1.00 g. As shown by both experimental and numerical simulation results, the soil acceleration amplification coefficients along the soil height fluctuate between 0.5 and 1.5. The pipe acceleration time curves and Fourier spectrum exhibit the same simulated and experimental pipe acceleration waveforms, and they both show significant amplification in the low to medium frequency band of 5–20 Hz. The testing and numerical simulated pipeline axial strain peak curves are similar and in good agreement, indicating the high reliability of the experimental results.