RU2792859C1 - Method for sealing annular spaces of well casing strings in conditions of distribution of low-temperature rocks - Google Patents

Abstract

FIELD: geological exploration and subsequent development of mineral deposits.

SUBSTANCE: invention is intended for oil and gas deposits in the conditions of distribution of low-temperature rocks. To implement the method of sealing the annular spaces of casing strings in the conditions of the distribution of low-temperature rocks (LP), geophysical work is carried out, including seismic, electrical exploration, thermometry, the interpretation of which determines the structure of the section of the LP, including the position of the roof and bottom of gas hydrate rocks (GHP). Wells are drilled with the installation of casing and lift strings to the design depth. Drilling under the conductor is carried out to a depth that provides overlapping of the OP thickness by at least 20-40 m with the deepening of the conductor's shoe into stable rocks. A heat-insulated direction is installed in the near-mouth zone of the well overlapping the interval of permafrost rocks (PFR). Seasonal cooling devices (SCA) are installed around the wellhead; the well is equipped with a thermometric fibre-optic cable, which is lowered behind the casing strings and behind the production string. In the annular space behind the direction, conductor and production cemented casing in the intervals of OP, thermobaric conditions are first created in the cement ring for its setting, and then freezing and hydration in the wellhead zone and at depth.

EFFECT: increased tightness of the rocks surrounding the well by providing the conditions for hydration of the channels with potential gas filtration to the mouth in the annulus.

7 cl, 1 dwg

Description

The invention relates to the field of geological exploration and subsequent development of mineral deposits, in particular oil and gas deposits in the conditions of the distribution of low-temperature rocks (NP), which include permafrost - permafrost, gas hydrate - GGP and thawed rocks - TP. NPs are distinguished by such dangerous phenomena as gas shows through rocks in the annulus due to their thawing and decomposition of gas hydrates with the release of hydrocarbon gases, as well as hydrocarbon gases from the annulus of the lower sections of the wells.

There are various ways to seal the annular cemented spaces of wells from gas penetration to the wellhead, including the installation of an annular packer, cement bridges over gas-producing rocks. However, these methods are not always effective.

In northern conditions, in the zones of permafrost, production wells use passive and active thermal insulation, including the use of heat-insulated lift and casing strings to ensure reliable and efficient operation of oil and gas production wells.

Closest to the proposed is a method for assessing the quality of well casing in the intervals of MMP-NP RF patent No. 2085727. Cl. E21B 47/00. Published on 07/27/1997, including temperature measurement in the well during cement hardening. The method also makes it possible to determine the limiting total amount of heat of hydration, which is released by 1 kg of cement slurry when filling the annular space behind the heat-insulated casing (TIC) at different times during cement hardening. The disadvantage of this method is the lack of necessary control when measuring temperatures both directly inside the TOC and in its cement ring, which also does not allow controlling the penetration of gas hydrate gas into the cemented annulus.

The proposed method for sealing the annular spaces of casing strings in the conditions of the distribution of low-temperature rocks (LP) includes geophysical work (seismic, electrical, thermometry), the results of the interpretation of which determine the structure of the LP section, incl. the position of the roof and bottom of the GTP, and drilling of wells with the installation of casing and lift strings to the design depth. The reduction of heat transfer from the gas (fluid) produced at the well to the annular sealed space of the production well is ensured by its thermal insulation with a thermally insulated lift pipe (LTT) and a thermally insulated guide (TN), maintaining the appropriate flow rate (calculated taking into account possible heat transfer) of the well and maintaining or / and creating temperatures in the annular spaces of casing strings close to the temperatures of the surrounding frozen and low-temperature rocks, both due to the choice of thermal insulation of the lift string, as well as the outer casing string and, at the same time, reducing the heat transfer from the gas flow to the well support and due to the intensification of cooling of these spaces by the surrounding Permafrost, as well as seasonally operating cooling devices (SDA) installed in the surrounding oilfields, for example, in the estuarine zone.

In the interval of occurrence of gas hydrate formations, gas hydrate gas during thawing of the GTP can penetrate into the annular space, for example, behind the casing conductor, as well as behind the cemented production casing, and this, when it passes into the gas hydrate state (hydration), leads to sealing of the lining as a result of filling non-hemetic areas with gas hydrates in cement rings behind casing strings, including surface casing and production string being cemented.

Hydration when creating conditions for the formation of gas hydrates in the annular spaces, makes it possible to prevent the flow of gas through the cemented spaces from gas producing formations, for example, those occurring in the permafrost zone of the KLZ (in thawed rocks of the TP) below the bottom of the permafrost, as well as from the rocks - gas reservoirs that lie deeper than the bottom of the oil reservoir, in which temperatures, for example, are slightly higher than 0°C and in them gas hydrates can also stably exist in the annular spaces under certain thermobaric conditions. Methods for identifying such zones, with possible stable conditions for the existence of gas hydrates, are presented, for example, in [1, 2, etc.].

Low-temperature rocks include rocks that contain ice (icy permafrost) and gas hydrate rocks - GGP and thawed rocks - TP that do not contain ice, but in which thermobaric conditions provide the possibility of a stable existence of gas hydrates.

The technical result, which the proposed method of sealing is aimed at, is to increase the efficiency of combating behind-the-casing gas shows and ensuring sealing of well lining in the intervals of occurrence of OP, including OP in the annular cemented spaces by providing them with thermobaric conditions of hydrate formation, including . through the use of seasonal cooling devices (SDA) installed in these areas, for example, behind the direction, as well as near the bottom of the permafrost. Also, maintaining the conditions of hydrate formation and ice formation is facilitated by thermal insulation in the design of production wells, the use of which helps to maintain negative temperatures of the rocks surrounding the well, which makes it possible to prevent gas flow through the annulus to the wellhead.

The essence of the invention is illustrated in the drawing, which shows the design of a production well in NP conditions and the results of sealing poor-quality cemented annular spaces behind casing strings with gas hydrates formed under certain thermal conditions of well operation.

In FIG. 1 indicates the following positions:

1 - non-thermal insulated lift column; 2 - heat-insulated in the upper zone section of the lift column, overlapping the OP; 3 - production cemented column; 4 - conductor blocking the NP; 5 - column head of the well; 6 - wellhead direction; 7 - thermal insulation of the wellhead direction; 8 - fiber-optic thermometric cable, lowered behind the direction and the conductor (they can also be equipped with a cemented production string); 9 - SDA installed behind the direction; 10 - SOU radiator on the surface; 11 - manometers; 12 - wedges of ice formed near the surface during freezing; 13 - formation ice near the surface in the mouth zone; 14 - bottom of icy permafrost adjacent to the surface; 15 - HGP at depth; 16 - zero isotherm at depth - NP bottom; 17 - gas hydrate layer in thawed rocks at depth; 18 - productive gas reservoir at depth; 19 - produced gas in the lift column; 20-23 - behind-the-casing gas shows; 24 - cement rings behind the casing, sealing the lining, in which gas hydrate annular plugs are formed.

In the method, the technical result is achieved due to the fact that before drilling, electrical and seismic surveys are performed, as well as thermometry, the structure of low-temperature rocks, the position of the bottom of icy rocks 14, the roof and bottom of gas hydrate rocks 15, 17 are determined, and drilling under the conductor 4 is carried out up to depth, providing overlapping of the NP thickness by at least 20-40 m with the deepening of the conductor shoe 4 into stable rocks, for example, clayey ones. Further, in the wellhead zone, a wellhead direction 6 is installed, overlapping the interval of permafrost, seasonal cooling devices (SDA) 9 are installed around the wellhead, and the thermal insulation of the well is selected so that in the annular spaces at fixed behind-the-casing pressures of the gas penetrating through the cement rings 24 to the mouth, at certain depths to maintain the thermobaric conditions of hydrate formation, taking into account the temperature of the produced gas 19 and, thus, to provide at these depths "additional" reliable sealing of the annular cemented spaces with the formed gas hydrates, sealing the filtration channels with annular gas shows 20, 21, 22, 23 , and behind the wellhead direction 6 with thermal insulation 7 also formed by ice 12, 13, which prevents gas from escaping through the annular spaces of the well and adjacent thawed rocks to its mouth. In addition, the well is equipped with thermometric fiber-optic devices, for example, a descending fiber-optic thermometric cable 8 behind the casing strings and behind the heat-insulated section of the production string 2, while in the annular space behind the direction 6, the conductor 4 and the production cemented string 3 in the OP intervals, first, thermobaric conditions are created setting, and then freezing and hydration in the wellhead zone and at depth, which provides conditions for hydration of the channels with possible gas filtration to the wellhead in the annulus and, accordingly, the tightness of the rocks surrounding the well in the OP intervals during well testing and development, including their subsequent operation.

To control the pressure behind the production cemented string 3, pressure gauges 11 are installed on the column head 5.

During the construction process, a lift string is installed on the well, which has a thermally insulated section in the upper part 2 and reduces the heat flow to the surrounding oil pipelines, then the thermal resistance of the thermal insulation of this section and the outer columns (direction 6, conductor 4) is determined that overlap the upper section , also determine the temperature of the rocks surrounding the well, the flow rates of the well and the temperature of the produced fluid (gas, oil) 19, taken from the heat-insulated section of the lift string 2 from the productive gas reservoir 18 at a depth, and ensure that thermobaric conditions of hydrate formation are maintained in the well annulus to seal the lining wells both at depth and in the wellhead zone.

In the future, control over the maintenance of temperatures in the annular spaces at appropriate depths, not higher than the equilibrium temperatures of hydrate formation, is carried out by maintaining the thermal mode of the well, effective thermobaric operating conditions of the well, taking into account the flow rate and temperature of the gas 19, including the thermal insulation of the wellhead direction 7 and the thermally insulated sections of the tubing string 2, and the process of sealing the annular space is provided for the control of pressures in the annular spaces, which should not be excessive and should not exceed the allowable values, including during long downtime of wells in oil conditions.

In addition, to reduce the thermal impact on the oil pipeline during drilling, gas hydrate formations 15, 17 are opened and covered with cement rings 24 at a drilling fluid temperature not higher than -1.0...-2.0°C. Similar requirements apply to cement slurries.

Also, when sinking - drilling a wellbore in the presence of GTP 15, 17 in the section and the ongoing loss of drilling fluid, it is not possible to crush it with warm drilling fluid (above the temperature of hydrate formation in these reservoir conditions).

Seasonal cooling devices (SDA) 9 cool the surrounding MMPs 12, 13 to certain temperatures, taking into account the thermal insulation of the wells, which prevents them from thawing in the summer.

The operation of the COA is seasonal and they operate in winter due to the temperature of the ambient winter air, which cools the coolant inside the COA through the COA heat exchanger, and the coolant located inside the COA flows down the wall of the COA tube and transfers cold into the rocks surrounding the COA. SDA do not work during the summer period and the rocks during this period are heated by the heat coming from the production well.

The design of a heat-insulated production well includes a lifting string, in the upper part consisting of a heat-insulated double-walled section 2 with thermal insulation placed in it, as well as casing strings: production string 3, conductor 4 and direction 6. All casing strings are rigidly connected into a single system by a string head 5.

Gas 19 is withdrawn through the lift string 1. The upper unstable rocks in this example are covered by a non-heat-insulated conductor, and permafrost rocks (PFR) adjacent to the surface are overlapped by the wellhead direction 6, including thermal insulation 7. Productive gas reservoir 18, from which gas 19 is produced through the lift string 1 is covered by a cemented production string 3.

The casing strings in the well are cemented. Behind the conductor 4 and the wellhead direction 6 in their upper part, special Arctic cement is used, including heat-insulating additives to increase the heat-insulating ability of the well design. In the wellhead zone, pressure gauges 11 are installed on the casing head to measure the pressure of gas penetrating through the cemented annular spaces of the casing strings to the wellhead, and wellhead thermometers that record the temperature of the produced gas at the wellhead.

In the annular spaces behind the heat-insulated direction 6, which overlaps the MMP and behind the conductor 4, a fiber-optic thermometric cable 8 is installed, and data on the temperatures measured using the cable in the well are recorded at the wellhead by a thermometric measuring device (TIU) recorder (not shown in the figure).

Gas in the leaky cement ring of the annular space can come from both the productive formation 18 and from the upper gas hydrate formations 15, 17 or from formations containing free gas that are not developed at this well (gas is not produced from them at this well).

If the annular spaces are leaky, gas from the upper gas hydrate formations 15, 17 and the productive formation 18 can enter these spaces and be filtered to the wellhead through the leaky annular spaces.

Cement rings 24 behind casing strings in some cases, in case of violations of the technology of string fastening and cementing of these strings, may be leaky, including with intense uncontrolled gas manifestations from gas reservoirs, and gas can penetrate to the wellhead through leaky annular spaces, which is fixed by pressure gauges 11 At the same time, at the wellhead, gas shows are recorded in the form of a pressure increase that significantly exceeds atmospheric or allowable pressures in the annular spaces established by regulatory documents for well operation.

In the annular spaces, for technological reasons, it is often noted that the annular space is not completely filled with cement, and cracks (filtration channels permeable to gas) and gaps behind it at the contact with the surrounding rocks are formed in the cement ring, through which behind-the-casing gas shows occur 20, 21, 22, 23 with the advance of the gas to the surface.

When using thermal insulation and taking into account the maintained thermobaric conditions in the wells in the annular spaces, gas hydrate plugs are formed behind the conductor, the production cemented casing and behind the wellhead direction, which make it possible to seal the annulus forming gas hydrates and prevent complications associated with the penetration of gas to the wellhead.

In the calculation examples of sealing cemented annular spaces in wells during the formation of gas hydrates in them, we will consider the formation of gas hydrate sealing plugs in these spaces, namely, cases of plug formation as behind heat-insulated internal columns, for example, in the case of the presence of only one internal heat-insulated column, namely, the lift (interval A), as well as in the case when the plug is formed behind the outer heat-insulated column (interval B), namely, behind the direction, and in this case, there is also an internal heat-insulated lift column in the structure.

Ensuring the tightness of the annular spaces in case of intensive annular gas shows is achieved in wells due to the thermal insulation of their structures in the zones of permafrost and low-temperature rocks and the formation of gas hydrates in the annular spaces, isolating channels permeable to gas in these poorly cemented spaces, which is achieved by monitoring the maintenance in the annulus spaces of thermobaric conditions for the occurrence and long-term existence of hydrates throughout the entire life of the wells.

Identification of conditions that ensure the stable existence of gas hydrates in the annular spaces is carried out through the use of deep thermometric devices in wells and control of the values of behind-the-casing pressures at the wellhead.

Determination by the method of the necessary thermobaric conditions in wells for sealing annular spaces during the operation of thermally insulated wells is carried out both as a result of measurements of temperatures and pressures in the well at the wellhead and at depth, and as a result of calculations of thermal conditions (annular temperatures) maintained in thermally insulated wells during their operation.

An increase in the sealing of the annular spaces is carried out both due to the formation of sealing gas hydrate plugs in the annular spaces, and due to the freezing of the annulus and adjacent rocks in the wellhead zone behind the heat-insulated direction.

Example 1 (interval A). The interval of the leaky annular space is blocked in this case only by a heat-insulated tubing string, for example, with diameters of the inner and outer pipes of the tubing string, respectively, 114 mm by 168 mm and with thermal insulation placed between these pipes. The heat-insulating capacity of such heat-insulated double-walled tubing, namely their thermal resistance U _T is 3.2 m⋅h⋅°C/kcal, and the thermal resistance of the cement sheath behind the production string is determined according to expression (1):

where R'e, R _u - outer radii of the production string and the cement ring behind it, m;

λ _c - coefficient of thermal conductivity of the cement ring, W / m⋅°С;

The total thermal resistance of the well structure in the lower studied interval will be:

where U _t , U _c; U _c - thermal resistance of heat-insulated lift pipes, cement ring and total thermal resistance behind the production string with a diameter of 245 mm, m⋅h⋅°С/kcal.

At the level of the resulting sealing gas hydrate plug (interval A) at a temperature of low-temperature rocks surrounding the well equal to t _p =2.0°C for the duration of the well operation τ _e =1.0 year=8760 hours, the temperature on the outer wall of the cement ring will be:

where K _t is the heat transfer coefficient through a heat-insulated lift pipe, kcal/m⋅h⋅°С;

U _t - thermal resistance of the heat-insulated lifting column, m⋅h⋅°С/kcal;

t _g , t _p - the temperature of the produced gas inside the heat-insulated tubing and the initial temperature of the surrounding rocks, °C;

λ _p - coefficient of thermal conductivity of rocks surrounding the well, kcal/m⋅h⋅°С;

r _vl , r _c - the radius of the thermal influence of the well and the outer radius of the cement ring behind the production string, m;

At a filtered gas pressure of 4.6 MPa or more and a steady-state temperature in the cement ring of 5.0°C, a stable gas hydrate plug is formed in the annular space at a depth of about 500 m (zone A) and the annular space behind the production casing will be reliably sealed from gas penetration to surfaces.

This temperature is controlled by measurements carried out by TIU.

At a gas pressure equal to, for example, 2.6 MPa, in the annular space at a depth of 270 m (interval A ₁ ) behind the production string, during the decomposition of gas hydrates in the reservoir and the temperature of the surrounding rocks t _p = 0 ° C and below, a gas hydrate plug will form.

At the temperature of the surrounding rocks t _p =0°C, and in the cement ring t _c =5.0°C at a depth of 270 m and annular gas pressure of 2.6 MPa, which is higher than the temperature t _p =0°C, the stability of gas hydrates, respectively , at t _p =5.0°C, cannot be provided and, accordingly, sealing of the annular space with hydrates will not be achieved. In this case, the gas will be filtered upward through the leaky space.

When gas is filtered in the annular space, a gas hydrate plug is formed in the interval at a depth where the temperature t _c = -1.0 ... 0 ° C in the annulus during operation (fixed by TIM) and at a pressure in the annular space of at least 2.5÷2, 6 MPa.

Let us consider the possibility of formation of a gas hydrate plug behind the production string t _p =-1.0°C at a depth of 330-370 m and a pressure in the cement ring of at least 3.3 MPa with a duration of well operation τ _e =1.0 year=8760 hours.

t _c \u003d 3.3 ° C.

At a temperature of t _c =3.3°C in the annular space at a depth of 370 m, a gas hydrate plug will also form at a gas pressure of 3.3 MPa and above, and the annular space will be sealed from gas penetration to the mouth.

Thus, it can be seen that gas hydrate plugs sealing the annulus during well operation are formed at depths of 250-370 m at gas pressures, respectively, in the annulus of 2.5-4.5 MPa and higher and temperatures, respectively, not higher than t _c \u003d -1.0 ... 5.0 ° С.

As the gas moves to the surface, the temperature in the annular space decreases due to lower temperatures of the surrounding rocks, including those in permafrost adjacent to the surface, which are in a frozen state.

Example 2 (interval B). At a depth of 60 m from the mouth, the rock interval is overlapped by two heat-insulated columns: the lift and the direction. So, for example, the control of thermobaric conditions over the direction (interval B) shows that at a temperature of the surrounding permafrost equal to -3.0°C and a gas temperature of +25.0°C, the temperature t _c during the entire life of the well does not rise above the temperature that is achieved in the warm period of the year in the summer period, with the duration of this period not more than τ _e =5.0 months = 3600 hours and taking into account the total thermal resistance U of the well design.

To calculate this parameter, we first determine the total thermal resistance of the well at the investigated depth (U).

U=5.32 m⋅°C/Wh

Taking into account the thermal resistance of the well structure equal to 5.32 m⋅°С/W, we determine the heat transfer coefficient of the structure equal to К=1/U=1/5.32=0.188 W/m⋅°С and the temperature in the cement ring t _c behind the direction according to (4).

We first determine the radius of the thermal influence of the well in the surrounding rocks (r _vl ) for the summer period τ _e =5.0 months = 3600 hours and, taking it into account, the temperature in the cement ring (t _u ):

t„=-1.38°C.

In winter, the SOU works for freezing and on the outer wall of the pipe at a depth near the bottom of the permafrost, the temperature _tcoy of the surrounding rocks is maintained, equal to -3.0°C. The distance at which the SDA is located from the axis of the production well is 1.5 m, therefore, in (5) we substitute instead of r _vl , respectively, the radius of the location of the SDA equal to r _cw = 1.5 m.

Using expression (4), we determine t _c in the winter period of the JCS operation:

Taking into account the obtained temperatures t _c , maintained in the well behind the heat-insulated direction in summer and winter, respectively, - 1.38 ÷ -2.14 ° C, when gas penetrates into the space behind the direction into the zone (interval B), it will hydrate with the formation of cement ring and in the gaps behind the cement ring of the gas hydrate plug at pressures of 2.40 MPa, the gas will not penetrate through the annulus to the wellhead.

When using thermal insulation of the well and SDA behind the cement ring, the direction of temperature in the frozen rocks at the well will be maintained for the entire life of the well no higher than -1.38÷-3.0°C and gas will not penetrate to the surface through the frozen rocks adjacent to the well .

Behind the conductor and behind the direction in the interval C in the summer, we determine the temperature t _ck , given that t _p \u003d -1.5 ° C and r _vl \u003d 5.61 m.

r _ow = 5.61 m.

Taking into account K=0.307 according to (4) we obtain in the summer period:

t _ck =1.92°C.

In winter, at t _coy \u003d -3.0 ° С: t _ck \u003d -0.60 ° С.

at t _sow = -4.0°C: t _ck = -1.51°C.

at t _coy \u003d -5.0 ° С we have: t _ck \u003d -2.43 ° С.

The average temperature t _ck at t _coy \u003d -3.0 ° С for the year will be t _ck \u003d (3600⋅1.92-5160⋅0.60) / 8760 \u003d (6912-3096) / 8760 \u003d 1.14 ° С, while at t _coy =-4.0 and -5.0°C it will be negative and will be, respectively: - 0.10°C and - 0.64°C.

At these average temperatures in the interval C, the annular spaces will freeze and their tightness will be ensured for the entire life of the wells.

In winter, in the zone C t _cn is equal to at t _sow \u003d -3.0 ° C:

Behind the conductor with a diameter of 324 mm, we also determine the thermal conditions according to (4) in the interval C, assuming the average temperature t _cn equal to -2.2 ° C, we obtain:

K=0.303 kcal/m⋅h⋅°С; t _cn \u003d -2.14 ° C.

As can be seen from the examples, at temperatures t _ce =t _ck =5.0°C and below (in the annulus of the production string and conductor) in a heat-insulated well with a heat-insulated lift string at a temperature of produced gas equal to 25.0°C and heat-insulating capacity U =3.35 m⋅h⋅°С/kcal of the well structure gas hydrate sealing plug in the annulus of the production casing and conductor, if it is lowered to this depth, is formed at the temperature of the surrounding rocks t _p =2.0°С at a gas pressure of 4, 6 MPa and above. In this case, the filtration of gas penetrating from the depth to the mouth is prevented.

At a gas temperature of 25.0°C and a temperature of the surrounding rocks t _p =-1.0°C at U=3.35 m⋅°C/W in the cement ring behind the production string and surface conductor, a reliable sealing annular gas hydrate plug is formed at a depth of 330 m at temperatures t _ce -t _ck =3.3°C and the pressure of the gas coming from the depth in the annular spaces equal to 3.3 MPa or more.

At a depth of 50 m, when the interval in the permafrost is covered by a heat-insulated lift string and a direction and, accordingly, at U=5.32 m⋅°C/W and t _p = -3.0°C, during well operation, gas hydrates are formed in the annular space, sealing annular space behind the direction at t _cn = -1.38°C and gas pressure in the annular space of 2.4 MPa or more, and at an average annual temperature t _cn = 1.14°C at a pressure of 3.0 MPa or more.

The sealing of the annular space behind the direction is also facilitated by its freezing and freezing of the rocks adjacent to it, for example, when the SDA is installed at a distance of 1.5 m from the axis of the production well and the temperature on the outer wall of the SDA pipe is maintained not higher than -4.0 ÷ -5, 0°C in the installation area of the upper heat-insulated section of the direction.

Behind the cement ring of the casing strings, the average annual temperature is maintained t _tsk =t _tsn = -0.21°С, taking into account the operation of the JCS in the winter period with a temperature t _coy not lower than -3.0°С, and freezing of the annular spaces will be provided, including providing conditions for the formation of a gas hydrate plug at a gas pressure of 2.6 MPa and above.

The use of this technical solution makes it possible to ensure the tightness of the annulus during long-term operation of thermally insulated wells in the zones of distribution of OP.

The effectiveness of this method lies in the possibility of carrying out on wells with their thermal insulation and control of thermobaric conditions in the annulus cemented spaces of their tightness and exclusion of gas penetration to the surface with its release into the atmosphere.

Information sources

1. Istomin V.A., Kwon V.G. Prevention and elimination of gas hydrates in gas production systems. - M.: IRTs Gazprom LLC, 2004.

2. Makogon Yu.F. Gas hydrates, prevention of their formation and use. - M.: Nedra. 1985. 232 p.

3. RF patent No. 2085727. Cl. E21B 47/00. Pub. 07/27/1997 (prototype).

Claims (7)

1. A method for sealing the annular spaces of well casing strings in the conditions of the distribution of low-temperature rocks (LP), including geophysical work, including seismic, electrical exploration, thermometry, the interpretation of which determines the structure of the LP section, including the position of the roof and bottom of gas hydrate rocks (GGP), and drilling wells with the installation of casing and lift strings to the design depth, while drilling under the conductor is carried out to a depth that provides overlapping of the OP thickness by at least 20-40 m with the deepening of the conductor shoe into stable rocks, also in the wellhead zone wells are installed with a thermally insulated direction, overlapping the interval of permafrost (PFR), seasonally operating cooling devices (SDU) are installed around the wellhead, the well is equipped with a thermometric fiber-optic cable, which is lowered behind the casing strings and behind the production string, and in the annular space behind the direction, conductor and production cemented string in the intervals of OP, first, thermobaric conditions for its setting are created in the cement ring, and then freezing and hydration in the wellhead zone and at depth, which provides conditions for hydration of the channels with possible gas filtration to the wellhead in the annulus and, accordingly, the tightness of the rocks surrounding the well in NP intervals (PMF, GGP, TP - thawed rocks) during testing and development of wells, including during their subsequent operation. 2. The method according to claim 1, characterized in that pressure gauges are installed at the wellhead to control the pressure behind the cemented production string. 3. The method according to p. 1, also characterized in that a heat-insulated section of the production string is installed on the well. 4. The method according to claim 1, characterized in that the thermal resistance of the thermal insulation of the tubing string and outer columns is determined, namely the direction and the conductor blocking the upper section of the permafrost, GGP and TP, the temperature of the rocks surrounding the well, the flow rates of the well and the temperature of the produced fluid, taken along the lift string, as well as the temperature of frozen rocks in the interval of permafrost-GHP and provide thermobaric conditions for hydrate formation for sealing the lining of the well both at depth and in the wellhead zone. 5. The method according to claim 1, characterized in that the provision at appropriate depths of temperatures in the annulus, not exceeding the equilibrium temperatures of hydrate formation, is carried out by maintaining the thermal mode of the well, using a heat-insulated lift string, heat-insulated direction and conductor, the use of SDA, and the process of sealing the annular space is controlled by measuring pressures and temperatures in it. 6. The method according to p. 1, characterized in that gas hydrate formations are opened and blocked with a gas hydrate plug at negative temperatures not higher than -1.0 ... -2.0 ° C, and also, respectively, using cooled cement slurries. 7. The method according to p. 1, characterized in that when sinking - drilling a wellbore in the presence of a GHF in the section and occurring losses, a drilling fluid with a temperature not higher than -1.0 ... -2.0 ° C is used.

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