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Arctic and Antarctica
Reference:

Well pads frozen foundations at the Yamburg field in a climate change

Petrov Boris Vyacheslavovich

ORCID: 0000-0002-9563-1985

Postgraduate student, Department of Cryolithology and Glaciology, Lomonosov Moscow State University; Engineer of the 2nd category, Yamburg Permafrost Laboratory of the Engineering and Technical Center of Gazprom Dobycha Yamburg LLC

119991, Russia, g. Moscow, ul. Leninskie Gory, 1

borya.petrov.2016@list.ru
Kurbatov Aleksei Sergeevich

Leading Engineer, Yamburg Permafrost Laboratory of the Engineering and Technical Center of Gazprom Dobycha Yamburg LLC

629740, Russia, Yamalo-Nenetskii avtonomnyi okrug, pos. Yamburg, -, -

as.kurbatov@yamburg.gazprom.ru
Polyakov Aleksandr Viktorovich

Head, Yamburg Permafrost Laboratory of the Engineering and Technical Center of Gazprom Dobycha Yamburg LLC

629740, Russia, Yamalo-Nenetskii avtonomnyi okrug, pos. Yamburg, ul. Array-Array, -

A.Polyakov@yamburg.gazprom.ru

DOI:

10.7256/2453-8922.2022.1.37366

Received:

20-01-2022


Published:

05-05-2022


Abstract: The results of long-term observation of the foundations temperature regime and dangerous cryogenic processes development near exploited well pads on the Yamburg field are presented. Temperature observations (1992-2020) includes data on four well pads. Influence of the natural and anthropogenic factors on the permafrost temperature regime was investigated. Based on a great experience of dangerous cryogenic processes field observations, a thermoerosion near gas well pads were characterized. Some well pads are considered, where the increasing of riverbed and ravine thermoerosion required the development of anti-erosion measures. According to observations, well pads frozen foundations temperature increases by an average of 0,039 °C per year. The results of observations show the absence of a pronounced technogenic temperature increase in the frozen well pads foundations, which Cenomanian gas produces. Taliks with a radius of 5-10 m around the wells are observed at the well pads foundations, which Valanginian gas produces. On the slopes and adjacent depressions, the temperature of frozen rocks is high, sandy soils of the dumps are subject to erosion. The development of thermoerosion processes threatens to the well pads foundations near the eroded riversides, in the areas of ice-wedge polygonal tundra.


Keywords:

temperature regime of foundations, temperature observations, well pad, production well, gas temperature, thermerosion, ravine, ice-wedge, Taz Peninsula, Yamburg field

This article is automatically translated. You can find original text of the article here.

Introduction

Natural gas production on the territory of the Yamburgskoye field is carried out by the cluster method. Along with the obvious advantages of this method of extraction associated with the optimization of construction and installation work, maintenance work, reduction of the total area of disturbed natural areas, etc., the use of the method adds some risks that require careful consideration. Such risks include the joint long-term warming effect of production wells on the entire thickness of frozen rocks and the activation of dangerous cryogenic processes in the upper part of the cryogenic stratum. It is known that ice extraction with subsequent compaction of the thawed mass of soil can lead to soil precipitation around production wells [1]. The sedimentation of the foundation soils leads to the loss of the longitudinal stability of the borehole in the permafrost zone due to the disappearance of the lateral support for the well support [2]. In addition, thawing rocks hang on the borehole and thereby create additional axial loads. Their magnitude can reach values leading to a loss of longitudinal stability of the support while maintaining lateral support on thawed soils [3], as well as to significant plastic deformations of structural elements leading to its destruction [4; 5]. Precipitation of significant magnitude, collapse of the direction and the formation of a funnel at the wellhead, etc. they can occur even in areas with low-grained rocks [6]. In general, such violations on the territory of the Yamburgskoye field are considered in sufficient detail. At the same time, the temperature growth trends of the upper layers of the MMP and the resulting risks of the development of cryogenic processes have not been previously considered. Among cryogenic processes, the greatest threat to the KGS is thermal erosion, which is widespread on the territory of the Yamburgskoye field [7, 8, 9]. The development of thermal erosion processes is facilitated by various natural factors (meandering of the riverbed and erosion of high banks, melting of underground ice, dynamics of thermokarst lakes, etc.) and anthropogenic factors (disturbance of vegetation cover, increased snow accumulation in infrastructure areas within the catchments of ravines) [10].

Areas of distribution of polygonal-vein ice require special attention. The development of thermal erosion in these areas often leads to the formation of a large gully network [11, 12, 13], threatening the integrity of the bases of the pipeline binding. The existing risks require constant monitoring of the temperature of the MMP at the mouth of production wells and in the bases of the pipeline binding, the condition of the structures of the wells and pipelines in operation, and the integrity of the sand filling of the bush sites [14]. The purpose of the study is to study the dynamics of the cryogenic characteristics of the soils of the KGS bases under the operating conditions of producing wells and under the influence of landscape and climatic factors. To achieve this goal , the following tasks were set: 1) to identify trends in the temperature of the soils of the bases of the KGS; 2) to consider the influence of production wells on the temperature regime of the soils of the bases; 3) to characterize the conditions for the development of dangerous thermal erosion processes in the area of the KGS.

Research area

The study area is located in the central part of the Taz Peninsula. Most of it is a low-lying, poorly drained swampy plain. The bases of the studied CGS No. 611, No. 110B to a depth of 15 meters are composed mainly of weakly silty alluvial deposits of the second above-floodplain terrace of sandy composition, overlain by technogenic sandy-filled soils. The bases of the studied CGS No. 506, No. 106B are composed of alluvial, lacustrine-alluvial deposits of the second above-floodplain terrace, represented mainly by fine, slightly silty sands overlain by technogenic sandy soils.

The territory has been significantly processed by various exogenous processes, such as thermal erosion, waterlogging, heaving, thermokarst, etc. Vegetation is mainly shrub-moss and grass-moss on elevated and well-drained sections of watersheds and a tussock tundra of fluff, shrubs and mosses on less drained areas. The soils are Arctic tundra and tundra gley with areas of peat-swamp and humus-peat-swamp.

According to the climatic zoning according to the classification of B.P. The Alice research area is located in the Subarctic belt. Winter is cold, the duration of the cold period is 220-250 days. Minimum temperatures drop to -59°C. Summer is short, moderately cool. The warmest period is the end of July–August, at which time the temperature can rise to +30 ° C. The average annual air temperature for the period from 1986 to 2020. it is -7.1 °C. The annual precipitation is 400-700 mm . The distribution of snow on the surface is uneven: from 0.2-0.5 m on flat tundra areas, up to 1.0-1.5 m in ravines and logs. The average thickness of the snow cover during its stable occurrence (November-April) is 0.44 m (according to field measurements of the Yamburg Permafrost Laboratory of the branch "Engineering and Technical Center" of Gazprom Dobycha Yamburg LLC from 2000 to 2020).

The territory of the Yamburgskoye field is located in the zone of continuous distribution of MMP. The thickness of frozen strata in the watershed spaces varies from 300 to 400 m. At lower geomorphological levels, their power can be reduced to 150-250 m, and on floodplains of large rivers up to 20-80 m. The ice thickness reaches a maximum in the upper part of the section of 0.7-0.8 (peat) and 0.3-0.35 (sand, sandy loam) and usually drops to 0.1-0.15 below 2.0-3.0 m. The cryogenic structure of soils is largely determined by their lithological composition and humidity. In clay soils, often layered thin–shelled cryotextures prevail in the upper part of the section, in the lower part of the section - horizontal layering. The sands are hard-frozen mainly with a massive cryotexture.

The MMP temperature values vary widely – from -0.5 to -4 °C. The depth of zero annual amplitudes reaches 10-13 m. The depth of seasonal thawing ranges from 0.3-0.6 m on peat bogs to 1.5-2.2 m in wetlands. In the valleys of large rivers, the roof of the MMP sinks 2.5 m or lower (according to the technical report of the YUZHNIIGIPROGAZ Institute LLC).

Initial data and research methodology

Observations of the temperature regime of the soil bases of the bushes of gas wells of the Yamburg field have been conducted by the Yamburg Permafrost Laboratory of the branch "Engineering and Technical Center" of Gazprom Dobycha Yamburg LLC since 1993 on the bushes of Cenomanian wells - No. 611 and No. 506 and Valangin wells – No. 106B and No. 110B. The beginning of operation of these bushes – 1988-1989.

The sites of these cluster sites – No. 611 and No. 110B, No. 506 and No. 106B are adjacent to each other geographically and are similar in landscape and geological conditions. The observation profiles of thermometric wells at the sites were equipped as part of engineering geocryological studies in the layer of zero annual base amplitudes due to the development of deformations of the supports of the overpasses of pipelines strapping production gas and gas condensate wells.

At the initial stage of observations, observation profiles of 13 thermometric wells with a depth of 10-11 m were equipped within each of the cluster sites (Fig. 1). The profiles diverged radially from production wells No. 6115 for KGS No. 611, No. 5061 for KGS No. 506, No. 10603 for KGS No. 106B and No. 11002 for No.110V. The distance between the thermometric wells inside the row was 5, 10 m. Subsequently, some of the thermometric wells were disabled by snowplowing equipment.

Fig. 1. The layout of thermometric wells at KGS No. 106B as of the beginning of observations (1993)

The wells are equipped with casing metal columns with a diameter of 89 mm. Information and recording complexes (IRC) "KrioLab" are used as measuring equipment. The error limits of these devices are ± 0.1 ° C at temperatures of +20 ° C ...-50 ° C. Data on wells are read twice a year (in winter and summer) in manual mode. Entering data into a personal computer is also carried out manually. The choice of IRCs is due to their high reliability, ease of operation and accuracy of measurements in difficult weather conditions. The data array is accumulated in a special software "Permafrost Laboratory" developed by Gazprom Dobycha Yamburg LLC. Processing of materials, plotting is carried out in Microsoft Excel software.

Climate impact

Currently, both within the region and in the cryolithozone as a whole, degradation of frozen rocks is observed in the conditions of climate warming [15, 16, 17, 18]. According to the observations of the Yamburg Permafrost Laboratory, as well as on the basis of survey data, the MMP temperature in natural conditions on the territory of the Yamburg deposit is growing at a rate of 0.056 ? per year (1979-2020) (Fig. 2). Over the period of continuous observations (2006-2020), the growth rate is 0.054 ? per year. The increase in MMP temperatures is observed in all the most widespread landscapes on the territory of the deposit under the influence of an increase in average annual air temperatures and an increase in the thickness of the snow cover.

Fig. 2. Dynamics of air temperature and MMP by background wells

The temperature regime of the frozen bases of bush sites differs from the MMP in natural landscapes due to the following main factors:

- the impact of production wells on the soils of the KGF bases;

- snow removal works on the surface of the KGF;

- lack of vegetation on the surface;

- the presence of fine sand filling with a thickness of up to 1 m;

- excess of the KGF surface above the surrounding surface by 1 m .

According to the data of the conducted studies, the growth rates of soil temperatures of the KGF bases are on average 0.039 °C per year – for the entire period of observations since 1992 and 0.017 ° C per year – for the period of observations since 2006. Thus, the temperature growth rates of the frozen bases of the KGF are lower than in the MMP in the natural landscapes of the Yamburgskoye field.

Impact of production wells

During the period of operation of gas well bushes, the temperatures of the extracted gas have changed significantly. Within the considered bushes of Cenomanian wells, the gas temperature at the mouth of gas wells at the initial stage of operation in 1988-1989 was 12-15 ?, and in the last 10 years it ranges from -8.9 ? to +6.0?. Within the studied bushes of Valanginsky wells, the gas temperature at the mouth of gas wells in 1988-1989 was 34-39 ?, and in the last 10 years it ranges from +14.8 ? to +25.7 ?. The temperature of the MMP at the research site before the arrangement of the KGF was -2.5 ... -4.0 ?.

The dynamics of the soil temperature of the bases of the observed Cenomanian bushes of gas wells is shown in Figures 3, 4. Within the bush of gas wells No. 506, the temperatures of frozen bases at a depth of zero annual amplitudes differ slightly – for thermometric wells located at a distance of 5 to 47 m from the production well, temperatures range from -0.7? to -1.2? by 2020 d. These values are very close to the background – -1.1? for 2020.

 

Fig. 3. Dynamics of soil temperature at the base of the bush of gas wells No. 506

Within the bush of gas wells No. 611, the ground temperatures of the bases at a depth of zero annual amplitudes also differ slightly, with the exception of data on a thermometric well located 40 m from the production well in a depression adjacent to the slope of the bush site. Here the temperature is significantly higher than on the surface of the KGF – - 0.4? vs. -2.3?.

Fig. 4. The dynamics of the MMP temperature at the base of the bush of gas wells No. 611

From the consideration of the ground temperature of the bases for two bushes of Cenomanian gas wells, there is no significant warming effect of production wells on adjacent frozen bases. Temperatures remain unchanged over a long distance from the production well, and the detected changes are associated with changes in the micro–landscape of the surface - in the depressions adjacent to the slopes of bush sites, where snow accumulates in winter, temperatures are significantly higher than on the surface of bush sites.  

The dynamics of the soil temperature at the base of the observed Valanginsky bushes of gas wells is shown in Figures 5, 6. The temperature of frozen bases at a depth of zero annual amplitudes within the bush of gas wells No. 106B 5 m from the production well is positive, in 2020 it reaches +1?, while for more distant wells (30-40 m) it reaches from -0.3? to -0.2?. Temperatures within KGF are higher than in the background well.

Fig. 5. The dynamics of the MMP temperature at the base of the bush of gas wells No. 106B

Similarly, on the bush of gas wells No. 110B, a talik with a radius of up to 10 m was formed around the production well. The temperature in 5 m from the production well reaches +1.1?, in 10 m from it the temperature is -0.1?...-0.4 ?.

Fig. 6. The dynamics of the MMP temperature at the base of the bush of gas wells No. 110V

From the consideration of the base temperatures for two bushes of Valanginsky gas wells, the warming effect of producing wells on the soils of the bases is obviously traced. A talik zone with a radius of 5-10 m is formed around the wells. The formation of sinkholes around production wells is not observed.

The effect of snow cover

The temperature regime of the soils of the bases is influenced by the thickness of the snow [19]. Taking into account regular snow-clearing operations on the territory of the KGS, snow accumulates in certain areas along the pipeline overpasses, where access for snow-clearing equipment is difficult, as well as in the marginal parts of the KGS and on the slopes. A small accumulation of snow contributes to a significant dependence of the temperature regime of KGF on air temperatures in winter. Thus, the minimum average annual MMP temperatures for most vehicles were recorded in 1999 and 2001, when the minimum temperatures of the cold period (October-May) were observed for the entire time of observations of air temperatures at the Yamburgskoye field (-20.9? in 1999 and -21.1? for the observation period from 1986 to the present)

The influence of snow is vividly illustrated by the temperature data for KGF No. 110V. Thermometric wells located to the south of the production well are adjacent to the highway, which is regularly cleared of snow. The vehicles to the north of the production well are located in an area inaccessible to snow removal equipment. As a result, the temperatures for TC 12, 13, 14, located 15-67 m south of the production well, are significantly lower before their failure than for the rest of the wells. According to TS 10 and 1127b, located 5 and 10 m south of the production well, temperatures due to the warming effect of production wells are significantly higher than for other wells south of the production well. At the same time, with respect to vehicles located at the same distance north of the production well, their temperatures are lower (for vehicles in 5 m – by 1.3 ? in 2012, for vehicles in 10 m – by 0.3? in 2020).

Also, in the context of the impact of snow cover on the temperature regime of the soils of the bases, attention should be paid to the data on KGF 506. Here, snowplowing equipment has access to all vehicles in the profile, and therefore, taking into account the absence of a significant warming effect of the production well, temperatures across the entire profile differ slightly – the difference between the maximum and minimum values is in 2020. 0.5 ?. 

Dangerous cryogenic processes

The thawing of frozen rocks on the slopes of the KGS and in depressions next to them leads to the erosion of the dumping soils against the background of the absence of ground covers on their surface (Fig. 7). Under certain conditions, these processes can lead to the formation of large erosion systems, the development of which is very characteristic of the territory of the deposit and threatens the integrity of the soils of the bases of the KGS. The processes take place against the background of a general increase in the activity of thermal erosion processes in the cryolithozone under conditions of climate warming [20].

Fig. 7. The washout on the slope of KGF No. 965(Photo by Makshantseva D.V., 15.08.2020)

Within the Yamburgsky NGCM, the KGS located along the banks of rivers are under threat from the development of ravine formation. The predominance of easily eroded fine and powdery sands in the upper part of the section and low differences between local and regional erosion bases (rivers of the Taz Peninsula relative to the Gulf of Ob), leads to intensive meandering of the riverbeds of the deposit. At some KGS, the development of riverbank retreat processes in the immediate vicinity of mining sites require the development of protective and compensating measures. As an example, let's consider KGS No. 513 (Fig. 8). The site was organized in 1992, 30 m from the right washed bank of the Ngarka-Poilovoyakha river. Due to the active retreat of the shore and intensive ravine formation along it, in 2015, a project was implemented to shift the section of the gas pipeline route-the plume from KGS No. 513 to 16.5 m from the river bank. The measures taken turned out to be insufficient, since 2018, additional work has been carried out to fill the forming ravines in the immediate vicinity of the KGS. In 2021, design solutions for the engineering protection of this site were developed, involving the layout of the slope surface and the construction of hydraulic structures.

Fig. 8. The section of the shore retreat in the area of the gas pipeline-plume route from KGS No. 513 (Photo by B.V. Petrov, 06.08.2021)

In other cases, when the KGS are located at a more distant distance from the washed shores, the integrity of the bases is threatened by the ravines forming along them. Thawed, rainwater, as well as the above-frozen waters of the STS are actively discharged into the river at the sections of the CGS, which leads to the formation of primary erosive forms on the surface of slopes and gently sloping areas of the tundra. The situation is sharply aggravated by the wide spread of polygonal-vein ice over the territory of the deposit. The development of thermal erosion processes in the areas of the distribution of polygonal-vein ice often leads to the formation of large gully systems.

In such areas, on the tundra areas adjacent to the washed-out shores, surface water is discharged along inter-polygonal depressions, along the roof of polygonal-vein ice. The gradual erosion of the ground roof, the increase in the power of the STS leads to thermokarst subsidence as a result of the extraction of underground ice, the rapid growth of the erosive form and the formation of a large gully system developing along a polygonal grid.

As an example, let's consider KGS No. 514 (Fig. 9). The site is located 260 m south of the right washed-out bank of the Ngarka-Poilovoyakha river. The KGS area is characterized by the development of polygonal-vein ice, along which a large gully system is being developed. The length of the ravine along the main channel for 2021 is 230 m . Since 2014 , the top of the ravine has moved from the river bank towards the KGF by 40 m . The filling of the upper part of the ravine, the arrangement of a culvert in its bottom, as of 2021, stopped the development of the ravine in the direction of the KGF.

Fig. 9. Ravine in the area of KGS No. 514 (Photo by B.V. Petrov, 15.08.2021)

Conclusion

The study shows that following the warming of the MMP in natural landscapes, there is also an increase in the temperatures of the soil bases of the KGF. The rate of temperature growth is lower than the background and averages 0.039 °C per year for the period of observations since 1992. The stabilization of the base soil temperatures occurs against the background of a decrease in the temperature of the extracted gas, and was especially evident from 2007-2010, when the temperature growth rates became noticeably lower than during the previous observation period.

According to the results of the study, the temperature effect of wells producing Cenomanian gas (from -8.9 ? to +6.0? at the wellhead) on the host frozen rocks is practically not observed. A thawing areole with a radius of 5-10 m is formed around wells producing warm Valanginsky gas (from +14.8 ? to +25.7 ? at the wellhead). The formation of subsidence craters around production wells has not been noted.

An important factor influencing the temperature regime of the soils of the KGF bases is the thickness of the snow cover. Regular snow-clearing operations in open areas make the temperature regime of the soils of the KGF bases very sensitive to air temperatures in winter.

There is a significant increase in the temperatures of frozen rocks in the depressions adjacent to the slopes of the bush filling of gas wells, which may contribute to the erosion of these slopes. In cases where the CGS is located next to the washed river banks in the areas of the distribution of polygonal vein ice, the thawing of the frozen soils of the CGS bases, the slopes of the sites and adjacent areas of depressions contributes to the intensive development of thermal erosion processes and threatens the integrity of the soils of the CGS bases.

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Subject of research: according to the author of the article, the study of the peculiarities of the lithogenic base change under the influence of the temperature of the frozen bases of the cluster sites of gas wells in a changing climate on the territory of the Yamburgskoye field. Research methodology: The authors have been positioning the analysis of the temperature regime of the soil bases of the bushes of the Yamburg field gas wells by the Yamburg Permafrost Laboratory of the branch "Engineering and Technical Center" of Gazprom Dobycha Yamburg LLC for more than 40 years. The relevance of the problem consists in identifying the tendency of increasing temperatures of the upper layers of the MMP and the risks associated with the development of cryogenic processes from the perspective of environmental management efficiency. The author of the study attempted a retrospective analysis of the temperature range over a fairly long period of time, which made it possible to make a short-term forecast of temperature changes until 2025. The scientific novelty of the author of the article is positioned in identifying trends in the temperature of the soils of the KGF bases, the influence of production wells on the temperature regime of the soils of the bases and the development of dangerous thermal erosion processes in the KGF area. The scientific novelty and sufficient value is the conclusion that there is no influence of the extracted gas with elevated temperature on the basis of man-made devices for the extraction and transportation of liquefied gas. Cancelled technogenic changes in cryogenic processes, according to the authors, are lower in intensity than the results of background processes. This conclusion indicates the absence of a negative anthropogenic impact on the background of natural processes. Style, structure, content the style of presentation of the results is scientific, the structure of the construction and presentation of the material is built quite logically. However, there are a number of issues, in particular: the author of the article should avoid unnecessarily quoting banal provisions that load the article (for example: "The temperature regime of the soils of the bases is influenced by the thickness of the snow [19]."). At the same time, there is no decoding of the abbreviation familiar to the authors, but which is not commonly used "... the upper layers of the MMP ...", "... the threat to the KGF is caused by thermal erosion"). It should also be noted the incorrect use of terminology, in particular, it is not about soil degradation, but rather soils during the formation of erosive and genetic landforms. The authors provide interesting photographs, but the interpretation of the illustration is not given. The authors of the article present in the article graphs of the course of temperatures containing digital information obtained during the study. However, it would be necessary to interpret the trends and compare the results. The bibliography is extensive and contains mostly relevant sources. An appeal to opponents in identifying the problem at the level of available information obtained by the author as a result of analyzing a large number of literary sources. Conclusions, the interest of the readership The conclusion given by the author summarizes the content of the article, the conclusions of the article are ascertaining, there are explanations of the reasons and the designation of prospects for environmental management, but the consumer of the information provided in the article is not defined by the authors.