China-Russia Crude Oil Pipeline Research Articles

Thermo-mechanical stability analysis of thermosyphons for pipeline soil and their optimal layout in permafrost regions

In permafrost regions, warm-oil buried pipelines release vast amounts of heat energy to surrounding soils and lead to rapid permafrost degradation. Settlement disasters induced by permafrost degradation significantly increase the probability of pipeline failure. The two-phase closed thermosyphon (TPCT) can cool soil, inhibiting permafrost degradation, but its deployment is still at the experimental stages along the China–Russia Crude Oil Pipeline (CRCOP). Therefore, it is important to determine an optimal layout for TPCTs that can achieve both effective cooling and cost control. In this study, a strategy for a nonlinear thermo-mechanical coupled model is proposed through Python–Abaqus secondary development. Based on it, the thermal and mechanical effects of TPCTs under different spacings, as well as their optimal layout, are numerically investigated. Closer TPCT spacing leads to a lower degradation rate of frozen soil and a lower peak TPCT heat flux. In addition, the peak pipeline von Mises stress in the transition zone increases for greater TPCT axial distances over time. When the TPCT axial distance is ≤8 m, the minimum pipeline principal strains remain below the critical compression strain over 50 years. Finally, a backpropagation neural network is constructed to predict the maximum pipeline compressive strain, and most prediction results fall within the 95% confidence interval.

Differences in the removal efficiency of heavy metals in soils with different vegetation backgrounds along the China-Russia crude oil pipeline

Differences in the removal efficiency of heavy metals in soils with different vegetation backgrounds along the China-Russia crude oil pipeline

Permafrost degradation induced by warm-oil pipelines and analytical results of thermosyphon-based thawing mitigation

The China–Russia Crude Oil Pipeline (CRCOP) has been in operation for more than ten years, and its oil temperature has been increasing annually. Problems with ground surface subsidence and pipeline settlement were found in geological investigations along the CRCOP, indicating the risk of pipeline instability. In this study, a system was established to monitor pipeline–permafrost interactions along the CRCOP. It was found that the seasonal thawing depth (STD) of a borehole 2 m away from the horizontal line of the CRCOP reached about 11 m in 2022. Based on the on-site measured boundary, a laboratory experiment was conducted to study the evolution of the thermal regime, and to investigate the cooling effect of thermosyphons. The results indicated the consistent existence of a thaw bulb surrounding the pipeline, which was open in warm seasons but remained closed in cold seasons and expanded in three directions at different speeds. Thermosyphoning erased the thaw bulb and altered the thermal evolution of the permafrost, with a gradually decreasing STD. The results of this research can serve as a reference for thermal regime assessments of the CRCOP and thaw settlement mitigation along the CRCOP, as well as for other counterparts across the world.

Distribution and Degradation Processes of Isolated Permafrost near Buried Oil Pipelines by Means of Electrical Resistivity Tomography and Ground Temperature Monitoring: A Case Study of Da Xing’anling Mountains, Northeast China

Human engineering activities and climate warming induce permafrost degradation in the Da Xing’anling Mountains, which may affect the distribution of permafrost and the safety of infrastructure. This study uses the electrical resistivity tomography method, in combination with field surveys and ground temperature monitoring, to investigate the distribution and degradation characteristics of permafrost and influencing factors at a typical monitoring site (MDS304) near the China-Russia Crude Oil Pipeline (CRCOP). The results show that the isolated permafrost in this area is vulnerable to further degradation because of warm oil pipelines and thermal erosion of rivers and ponds. The isolated permafrost is degrading in three directions at the MDS304 site. Specifically, the boundary between permafrost and talik is on both sides of the CRCOP, and permafrost is distributed as islands along a cross-section with a length of about 58–60 m. At present, the vertical hydrothermal influence range of the CRCOP increased to about 10–12 m. The active layer thickness has increased at a rate of 2.0 m/a from about 2.4–6.8 m to 2.5–10.8 m from 2019 to 2021 along this cross-section. Permafrost degradation on the side of the CRCOP’s second line is more visible due to the river’s lateral thermal erosion, where the talik boundary has moved eastward about 12 m during 2018–2022 at a rate of 3.0 m/a. It is 2.25 times the westward moving speed of the talik boundary on one side of the CRCOP’s first line. In contrast, the talik boundary between the CRCOP’s first line and the G111 highway also moves westward by about 4 m in 2019–2022. Moreover, the maximum displacement of the CRCOP’s second line caused by the thawing of frozen soil has reached up to 1.78 m. The degradation of permafrost may threaten the long-term stability of the pipeline. Moreover, the research results can provide a useful reference for decision-makers to reduce the risk of pipeline freeze-thaw hazards.

Applicability analysis of thermosyphon for thermally stabilizing pipeline foundation permafrost and its layout optimization

Rapid permafrost thawing triggered by heat release from the buried warm-oil pipeline would result in the instability of the pipeline, posing a potential risk of an oil spill in permafrost regions. Therefore, how to precisely control the ground temperature to mitigate pipeline foundation permafrost from thawing is of significant importance. Thermosyphon is a widely-accepted and extensively-used countermeasure against permafrost thawing in permafrost engineering. This paper presents 3-year (2015–2018) monitored data of ground temperature and geophysical survey results conducted by electrical resistivity tomography in April 2018, to investigate the thermal stabilizing effect of thermosyphons installed nearby the China-Russia crude oil pipeline (CRCOP) and the influencing factors. Furthermore, numerical simulation tests were conducted to evaluate their long-term cooling applicability and to optimize their layout parameters. Field observations show that the thermosyphons can cool down and even freeze the thawed soil layers around the CRCOP, prohibiting the infiltration of water into the thawing front to some extent and effectively mitigating the rapid thawing of permafrost beneath the pipeline. The performance of the thermosyphons is greatly influenced by the method and time of thermosyphon installation, as well as layout parameters including the number and longitudinal spacing. Two pairs of thermosyphons with a shorter spacing are unable to control the thawing of the underlying permafrost due to the non-anticipated higher oil temperature, the thermal erosion of water ponding, and climate warming. The simulated results indicate that thermosyphons perform well in the first 5 years after installation. Thermosyphon lowers the mean annual temperature of soils surrounding it by about 2 and 1.4 times when the evaporator section length is increased by 50% and the longitudinal spacing is decreased by 0.5 m, respectively. The application of thermosyphons has proven its strength for thermally stabilizing the pipeline foundation permafrost along the CRCOP.

A newly integrated ground temperature dataset of permafrost along the China–Russia crude oil pipeline route in Northeast China

Abstract. The thermal state of permafrost in the present and future is fundamental to ecosystem evolution, hydrological processes, carbon release and infrastructure integrity in cold regions. In 2011, we initiated a permafrost monitoring network along the China–Russia crude oil pipeline (CRCOP) route at the eastern flank of the northern Da Xing'anling Mountains in Northeast China. We compiled an integrated dataset of the ground thermal state along the CRCOP route consisting of meteorological data near the southern limit of latitudinal permafrost, ground temperature (GT) data in 20 boreholes with depths of 10.0–60.6 m, soil volumetric liquid water contents (VWCs) and 2D electrical resistivity tomography (ERT) data at different sites. Results demonstrate a permafrost warming during 2011–2020 in the vicinity of the southern limit of latitudinal permafrost, as manifested by rising GTs at almost all depths in response to climate warming. Local thermal disturbances triggered by the construction and operation of CRCOPs have resulted in significant permafrost warming and subsequent thawing on the right-of-way (ROW) of the pipelines. This permafrost thaw will persist, but it can be alleviated by adopting mitigative measures, such as an insulation layer and thermosyphons. The in situ observational dataset is of great value for assessing the variability of permafrost under the linear disturbances of the CRCOPs and related environmental effects, for understanding hydro–thermal–mechanical interactions between the buried pipelines and permafrost foundation soils, and for evaluating the operational and structural integrity of the pipeline systems in the future. The dataset is available at the National Tibetan Plateau/Third Pole Environment Data Center (https://doi.org/10.11888/Cryos.tpdc.272357; Li, 2022).

Thermal and mechanical analysis of the China–Russia Crude Oil Pipeline suffering settlement disaster in permafrost regions

In permafrost regions, the soil settlement disaster owing to permafrost degradation has become one of the important reasons for buried warm-oil pipelines failure. In this paper, the 3D sequential thermo-mechanical coupled model is carried out to investigate the interaction between buried warm-oil pipeline and surrounding permafrost. The effects of parameters, including thaw-settlement coefficient, length of transition zone, diameter-thickness ratio and internal pressure, on the pipeline mechanical behavior are numerically investigated. Among them, the thaw-settlement coefficient and length of transition zone present more significant effects on the peak strain of the pipeline. In addition, the effects of insulation layer and two-phase closed thermosyphon (TPCT) on pipeline–soil interaction are investigated in thermal and mechanical fields. With no protective measure, the permafrost layer under pipeline will completely degrade in about 20 years with 0.33m/a. The pipeline is considered to reach failure limitation even within 10 years. However, under the influence of combined measure, the permafrost degradation rate is only about 1/10 of that without protective measure. The peak compressive strain is significantly lower than the critical compressive strain, and the pipeline remains safe for 50 years. Therefore, the combined measure is an ideal method for ensuring pipeline safety in permafrost regions.

Proposal of a New Method for Controlling the Thaw of Permafrost around the China–Russia Crude Oil Pipeline and a Preliminary Study of Its Ventilation Capacity

The China–Russia crude oil pipeline (CRCOP) has been in operation for over ten years. Field observation results have shown that a thaw bulb has developed around the CRCOP which expands at a rate of more than 0.8 m∙a−1 in depth. In view of the deficits of existing measures in mitigating permafrost thaw, a new control method is proposed based on active cooling. According to the relationship between total pressure loss and the driving force of natural ventilation, the wind speed in a U-shaped air-ventilation pipe around the CRCOP is calculated. By analyzing the theoretical calculation and numerical analysis results, it is found that the influence of thermal pressure difference on the natural ventilation of the structure can be negligible, and the influences of resistance loss along the pipe and local resistance loss in the pipe are similarly negligible. Exhaust elbows greatly improve the ventilation performance of the U-shaped air-ventilated pipe. This study developed a novel structure around warm-oil pipelines in permafrost for mitigating thaw settlement along the CRCOP and other similar projects across the world.

Stress–Strain Assessments for Buried Oil Pipelines Under Freeze-Thaw Cyclic Conditions

Abstract In this study, outdoor freeze-thaw cyclic tests on the Q345 steel pipeline portion were conducted to analyze the buried oil pipeline stress evolution in a seasonally frozen soil area, namely, the Mohe–Daqing portion of China–Russia crude oil pipeline. The results obtained show that under the freeze-thaw cycle, the variation trend of soil temperature around the pipeline exhibited a hysteresis pattern, which was similar to that of atmospheric temperatures. The soil frost heaving force was shown to drop with depth, and its value at the pipe top was higher than that at the pipe bottom. With the number of freeze-thaw cycles, the frost heaving force of the soil first increased and finally stabilized, while the principal stress of the pipeline increased gradually, and its extreme value tended to be stable after 7–8 cycles, which was consistent with the “ratchet effect” theory. The above findings made it possible to elaborate on a more efficient freeze-thaw cyclic test setup for clarifying the mechanism of frozen soil/pipeline interactions.

Characteristics of the active-layer under the China-Russia Crude Oil pipeline

Active layer is a key component for permafrost environment studies as many subsurface biological, biogeochemical, ecological, and pedogenic activities prevail in this layer. This study focuses on active layer temperature monitoring in an area with sporadic permafrost at two adjacent sites along China-Russia Crude Oil Pipeline (CRCOP), North-East China. Site T1 is located in disturbed ground on the right-of-way (on-ROW) 2 m away from the center of the oil pipeline. T2 is located in a natural and undisturbed site, around 16.6 m off-ROW. Our objective was to study seasonal variability of the active layer depth and thermal regime from October 2017 to September 2018. The monitoring sites consist of soil temperature probes arranged in a vertical array at different depths at both sites. The following parameters were computed: number of isothermal days (ID), freezing days (FD), thawing days (TD), freezing degree days (FDD), thawing degree days (TDD), number of freeze-thaw days (FTD). The mean air temperature in the monitoring period reached - 3.2°C. The temperature profile indicates that the maximum active layer thickness observed during the study period was 10 m at T1 and 2 m at T2. The majority of the soil temperatures were above or close to 0°C, resulting in great values of TDD, especially in the first 4 m depth. TDD for T1 were predominant and ranged between 600–1160°C·days (0–4 m depth) reflecting the influence of oil temperature from the pipeline. In T2 borehole FDD were predominant for all the soil layer depths resulting in less permafrost degradation. This comparison emphasizes the significant influence of vegetation removal and the dispersed heat from the pipeline on the active layer thickness.

Assessment of Freeze–Thaw Hazards and Water Features along the China–Russia Crude Oil Pipeline in Permafrost Regions

The China–Russia crude oil pipeline (CRCOP) traverses rivers, forests, and mountains over permafrost regions in northeastern China. Water accumulates beside the pipe embankment, which disturbs the hydrothermal balance of permafrost underlying the pipeline. Ground surface flows along the pipeline erode the pipe embankment, which threatens the CRCOP’s operational safety. Additionally, frost heave and thaw settlement can induce differential deformation of the pipes. Therefore, it is necessary to acquire the spatial distribution of water features along the CRCOP, and analyze the various hazard probabilities and their controlling factors. In this paper, information regarding the permafrost type, buried depth of the pipe, soil type, landforms, and vegetation were collected along the CRCOP every 2 km. Ponding and erosive damage caused by surface flows were measured via field investigations and remote sensing images. Two hundred and sixty-four pond sites were extracted from Landsat 8 images, in which the areas of 46.8% of the ponds were larger than 500 m2. Several influential factors related to freeze–thaw hazards and erosive damage were selected and put into a logistic regression model to determine their corresponding risk probabilities. The results reflected the distributions, and forecasted the occurrences, of freeze–thaw hazards and erosive damage. The sections of pipe with the highest risks of freeze–thaw and erosive damage accounted for 2.4% and 6.7%, respectively, of the pipeline. Permafrost type and the position where runoff encounters the pipeline were the dominant influences on the freeze–thaw hazards, while the runoff–pipe position, buried depth of the pipe, and landform types played a dominant role in erosive damage along the CRCOP. Combined with the geographic information system (GIS), field surveys, image interpretation and model calculations are effective methods for assessing the various hazards along the CRCOP in permafrost regions.

Rapid permafrost thaw induced by heat loss from a buried warm-oil pipeline and a new mitigation measure combining seasonal air-cooled embankment and pipe insulation

In permafrost regions, the pipelines buried under the ground are widely used for long-distance transportation of fossil fuel, which contributed to research focusing on the interaction between such pipelines and surrounding permafrost. In this study, field observations were conducted since 2011 to investigate the thermal interaction between the China-Russia Crude Oil Pipeline and the surrounding permafrost. Air and oil temperatures at the study site were collected, and the ground temperatures on and off the right-of-way of the pipeline were observed. The observations showed that the large heat loss from the buried pipeline made a rapid increase in the ground temperatures and thawing of underlying permafrost. To slow down the rapid permafrost thawing, a new design was proposed by combining a seasonal air-cooled embankment and pipe insulation. A coupled model was developed to describe the complicated heat transfer process among the ambient air, embankment, warm-oil pipe and permafrost. The numerical simulations showed the design could effectively transfer the heat from the pipeline to the environments in the cold season and reduce the heat intake of the permafrost subgrade in the warm season. The design can be effectively used to control the ground thermal regimes of pipeline systems built in cold regions.

Thermal influence of ponding and buried warm-oil pipelines on permafrost: a case study of the China-Russia Crude Oil Pipeline

Thermal influence of ponding and buried warm-oil pipelines on permafrost: a case study of the China-Russia Crude Oil Pipeline

Study on permafrost thermal stability and disturbance of the Mohe-Daqing oil pipe and its accompanying road of China-Russia Crude Oil Pipeline

The Mohe–Daqing oil pipeline (MDOP) of China–Russia crude oil pipeline (CRCOP) goes through a 441 km permafrost in high-latitude regions, the most critical problem of which is the thawing settlement of the oil pipe. Global warming effect, oil temperature, and construction technology causes the increase of ground temperature and accelerates the degradation of permafrost. The influence of geohazards on the existing CRCOP and its accompanying road was investigated in this study, which showed that the current engineering had been affected by freezing-thawing influence. It would be more serious for the thermal disturbance between each other. In view of this problem, the thermal stability of the oil pipe and accompanying road was simulated based on the MDOP, considering various scenarios of different oil temperatures, whether global warming is considered or not, whatever the thermal insulation layer is and regardless of the different distances from the accompanying road. The numerical results indicate that the oil temperature had considerable influence on the thawing rate of permafrost. Placing the thermal insulation material around the oil pipe can effectively mitigate or even control the degradation of permafrost. With this measurement, the thaw depth has remained stable after 5 years of construction, and had been controlled within 3.0 m when the thermal insulation thickness reached 8.0 cm. The accompanying road can also have an adverse effect on the permafrost for its thermal interaction with the oil pipe. The larger the distance, the lesser the thermal disturbance. Therefore, the thermal stability of MDOP can positively adopt a suitable oil temperature for thermal insulation thickness, along with an optimized distance away from the accompanying road as well. This study would also provide an essential theoretical and technological support for the design of oil pipeline in other permafrost regions.

Relationship between ponding and topographic factors along the China-Russia Crude Oil Pipeline in permafrost regions

Relationship between ponding and topographic factors along the China-Russia Crude Oil Pipeline in permafrost regions

Analysis of ground temperature variation in differential settlement of China-Russia crude oil pipeline: field monitoring and numerical simulation

In vast areas of rich frozen soil, the intense heat exchange between the hot oil pipeline and surrounding soil results in the continuous melting of permafrost under the pipeline and the continuous sinking of the pipeline. Moreover, the settlement rate and depth of the pipeline are also different due to the influence of ice content and the thickness of rich frozen soil layer. Therefore, in this paper, based on the field measured data, by adopting the method of numerical simulation, the temperature rise process of the soil around the pipeline under the condition of different subsidence rate and different thickness of rich frozen soil layer is studied. The results show that with the increase of the thickness of the frozen soil layer, the degradation depth of the upper limit of the artificial frozen soil in the lower part of the pipeline increases gradually. Under the same thickness of the frozen soil layer, the influence of the settlement rate of the pipeline on the upper limit of the artificial frozen soil in the lower part of the pipeline mainly concentrates on the initial operation stage of the pipeline; with the increase of the thickness of rich frozen soil layer, the upper limit difference of artificial frozen soil under different settlement rates of pipelines at the same time increases gradually. Of different sedimentation rate and the rich soil layer under the condition of ice -6 m depth of geothermal heating process monitoring, the geothermal heating process can be divided into three stages: melting stage (I), rapid heating stage (II), slow heating stage(III). With the increase of the settling depth, the duration of the phase I and II is significantly reduced, the heating rate is significantly promoted, the duration of phase III is increased significantly and the heating rate is gradually reduced.

Pipeline–permafrost interaction monitoring system along the China–Russia crude oil pipeline

In-situ monitoring system is absolutely necessary for a long-distance linear pipeline infrastructure in permafrost regions due to the complicated interaction between buried pipeline and its harsh permafrost environment. To study this complex problem, a comprehensive in-situ monitoring system has been designed and established along the China–Russia Crude Oil Pipeline (CRCOP), which is one of vital energy channels for importing crude oil from Russia to China. This monitoring system can record the meteorological data, ground temperature and water content within the permafrost foundation, vertical settlement of the oil pipe, ground surface deformation on the pipeline right-of-way (on-ROW), as well as the thaw bulb around the pipeline at four sites with different engineering geological conditions. In this paper, the layout and instrumentation of the whole monitoring system and monitoring methods are described in detail, and then the thermal regime of permafrost on-ROW and off-ROW and cooling performance of the mitigative measures on foundation soils are evaluated. Results show that heat dissipated from the CRCOP lead to the rapid degradation of permafrost on-ROW and produce different sizes of thaw bulb around the oil pipelines. The mitigative measures, including insulation layer, two-phase closed thermosyphon and U-shaped air-ventilated pipes, are effective to minimize permafrost degradation and ensure the thermal stability of permafrost foundation along the CRCOP. Some recommendations are proposed for future research and for the monitoring system to be improved. This monitoring system can provide multi-field data to clarify the interaction between pipeline and permafrost degradation under different geological conditions, and guide the design and maintenance of the buried warm pipeline in permafrost regions.

Permafrost warming along the Mo’he-Jiagedaqi section of the China-Russia crude oil pipeline

The permafrost along the China-Russia Crude Oil Pipeline (CRCOP) is degrading since the pipeline operation in 2011. Heat dissipated from the pipeline, climate warming and anthropogenic activities leads to permafrost warming. The processes of permafrost warming along the CRCOP were studied based on the monitoring of air and soil temperatures, and electrical resistivity tomography (ERT) surveys. Results show that: (1) the mean annual air temperature (MAAT) in permafrost regions along the CRCOP increased with a rate of 0.21°C/10a–0.40°C/10a during the past five decades; (2) the mean annual ground temperature (MAGT, at −15 m depth) of undisturbed permafrost increased by 0.2°C and the natural permafrost table remained unchanged due to the zero-curtain effect; (3) permafrost surrounding the uninsulated pipeline right-of-way warmed significantly compared with that in a natural site. During 2012–2017, the MAGT and the artificial permafrost table, 2 m away from the pipeline centerline, increased at rates of 0.063°C/a and 1.0 m/a. The thaw bulb developed around the pipe and exhibits a faster lateral expansion; (4) 80- mm-thick insulation could reduce the heat exchange between the pipeline and underlying permafrost and then keep the permafrost and pipe stable. The MAGT and the artificial permafrost table, 4.8 m away from the center line of the pipeline, increased by 0.3°C/a and 0.43 m/a, respectively. Due to the heat disturbance caused by warm oil, the degradation of wetland, controlled burn each autumn and climate warming, the permafrost extent reduced and warmed significantly along the CRCOP route. Field observations provide basic data to clarify the interactions between CRCOP and permafrost degradation and environmental effects in the context of climate change.

Permafrost thawing along the China-Russia Crude Oil Pipeline and countermeasures: A case study in Jiagedaqi, Northeast China

The China-Russia Crude Oil Pipeline (CRCOP) traverses 441-km-long permafrost zones in northeastern China. Since the pipeline operation in 2011, significant ground surface subsidence occurred within the trench of the pipeline in warm and ice-rich permafrost zones. Oil temperatures from three pump stations were obtained and the soil temperatures around the pipe at two cross sections along the CRCOP in Jiagedaqi, northeast China were monitored during the period from 2011 to 2017. With the date records, permafrost thawing and thaw bulb development around the pipe were investigated in this study, as well as the cooling effect of thermosyphons experimentally installed around the pipe. Results showed that the mean monthly oil temperature ranged from 0.4 to 17.9 °C and increased slowly with operation time increase. Due to thermal effect of the warm oil, the artificial permafrost table near the pipe was approximately 5.9 m greater than that in the natural ground 5 years after pipeline operation. A thaw bulb developed around the pipe and expanded at a rate of more than 1.0 m/a in depth. Following the permafrost thawing, ground subsidence around the pipe was significant. The buried depth of the pipe declined with a rate of approximately 0.35 m/a during the study period. To mitigate the permafrost thawing and the pipe settlement, a pair of thermosyphons were experimentally installed at the two sides of the pipe in March 2015. After 2 years of installation, the shallow foundation soils were cooled down and the thaw bulb was partially re-frozen. However, there was still a thawed layer beneath the pipe. Long-term thermal regime of foundation soils under the cooling effect of the thermosyphons needs further investigation.

Field observations of cooling performance of thermosyphons on permafrost under the China-Russia Crude Oil Pipeline

The buried China-Russia Crude Oil Pipeline (CRCOP) traverses 441-km discontinuous permafrost zone and has been operating at positive oil temperature since 2011. The underlying permafrost is degrading and thaw settlement occurs in the trench. An instrumented site was established to monitor ground temperature and water content under the CRCOP to evaluate permafrost degradation and cooling performance of the thermosyphons installed near the pipe. Field observations show that: (1) mean annual oil temperatures are higher than 0 °C and show a gradual warming trend (average increase by 2 °C during the observation period from 2012 to 2016; (2) the active layer thickness (ALT) increases by 2.7 m and the deep (15–20 m) permafrost temperature, 2 m away from the uninsulated pipe, rises 0.2 °C from 2014 to 2017; (3) thermosyphon can cool the soils surrounding the pipe and effectively mitigate thawing of underlying permafrost depending on its number, spacing and working duration; and (4) a thaw bulb surrounding the pipe exists even in winter due to a higher oil temperature. Field observations provide a better understanding of permafrost degradation, cooling effect and design parameters of thermosyphons, and basic data for numerical validation, implications for other similar cold regions pipeline engineering.