RU2445338C1 - Sealing composition for insulation work in well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to sealing compositions for insulation works carried out in production wells of minefields and underground storage of gas, which can be used for insulation of between-casing and after-casing space, repeated sealing of threaded connections of casing strings. Sealing composition for insulation work in the well includes the following, wt %: synthetic camphor 1-49, polyvinylbutyral film 1-6, isopropyl alcohol is the rest.

EFFECT: increasing efficiency of insulation works carried out in wells owing to using sealing composition with improved process properties determined with increased plasticising properties, adhesion of composition to surfaces of protective and production strings, and increasing the time of the well operation between overhauls.

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Description

The invention relates to the gas industry, in particular to sealing compositions for insulation work in producing wells of fields and underground storage of underground gas, which can be used to isolate annular and annular space, re-sealing threaded joints of casing strings.

The analysis of the prior art showed the following:

- known polymer composition, which can be used for temporary isolation of the annular space of the well, the formulation of which has the following ratio of ingredients, wt.%:

Polyvinyl chloride resin (PVC resin) 36.5-55.5 Dibutyl phthalate 44.5-63.5

(see USSR AS No. 1186785 dated 11/23/1983 according to class E21B 33/138, published in Bul. No. 39, 1985).

The disadvantage of this polymer composition is the lack of effectiveness of insulation work. This is due to the following reasons: with the indicated content of ingredients, this composition has high initial viscosity values of 2150-2630 cPs (see description table). High viscosity will make it difficult to perform insulating work, from the moment the composition is pumped. When pumping, the composition will not penetrate to a sufficient depth in the leakage zone, which in turn can cause gas contamination of the near-wellbore space. According to the description, the cured composition is an elastic mass that does not deteriorate for a long time at t = 45-120 ° C for a long time. However, in this case, the values of the ultimate shear stress (discharge) characterize the composition as a highly viscous liquid. Therefore, this composition cannot be used with high efficiency for isolation of annular, annular space, repeated sealing of threaded joints of casing strings. The boiling point of the dibutyl phthalate used in the formulation is 340 ° C, which does not allow its molecules to evaporate, thereby contributing to the isolation of the polymer - PVC resin in solid form. In this regard, the composition has low strength properties. This composition has pronounced hydrophobic properties, which leads to its low adhesion to the surfaces of the columns of technical and production pipes;

- known working fluid is a solution of urea in methanol (a complexing agent), described in the method for restoring the tightness of the annulus of a well (see RF patent No. 2234591 of January 3, 2002 according to CL E21B 33/138, publ. in Bull. No. No. 23, 2004).

The disadvantage of this working fluid is the lack of effectiveness of insulation work. This is due to the following reasons: the use of a working fluid - a solution of urea in methanol to eliminate intercolumn pressures is effective only if oil is used as the intercolumn fluid. Column fluid may be water (brine), while the use of this working fluid is ineffective due to the high solubility of methanol and urea in it. If gas acts as a cross-column fluid, then the sealing efficiency of the specified composition is reduced due to the low content in the working fluid of a plugging agent - urea, the concentration of which is about 15 wt.%.

When interacting with oil, the working fluid forms a clogging mass, which has low adhesive properties due to the oil content in it, which has good lubricating properties. Oil can act as a plasticizer, however, the clogging mass is easily destroyed by mechanical stress.

The above will not provide effective sealing of the inter- or annular space, repeated sealing of threaded joints of casing strings.

- As a prototype taken sealing composition for insulation work in the well, the formulation of which has the following ratio of ingredients, wt.%:

Pine Rosin 20-40 Castor oil 0.5-1.0 Acetone rest

(see patent of the Russian Federation No. 2387691 dated December 25, 2008 according to class C09K 8/502, published in Bul. No. 11, 2010).

The disadvantage of this polymer composition is the lack of effectiveness of insulation work.

When operating wells in underground gas storages, a leak in the cement ring occurs. Cracks in the cement ring occur due to temperature stresses that occur during the injection and selection of hot or cold gas, as well as dynamic loads on the column and cement stone from pressure fluctuations in the wellbore and in the reservoir when changing injection-selection cycles and vertical alternating rock mass movements.

In the cycle of gas injection, its temperature, as a rule, differs significantly from the reservoir and within 5-6 months there is a change in the thermal field of the well walls. When taking gas from underground gas storage, gas rising to the surface changes the temperature of the near-wellbore zone. The temperature stresses arising here will be compressive or tensile in the UGS operation cycles.

As for the fields, the reasons for the annular manifestations that cause the destruction of cement stone are various technological operations carried out in the well: crimping and perforating casing, drilling a cement cup, deepening the wellbore, etc.

Pine rosin is a fragile material. When sealing the cement ring with rosin, even with the addition of a plasticizer - castor oil, cracking of the sealing mass can occur, which in turn causes intercolumn pressure. Therefore, the plasticization of pine rosin is insufficient, the sealing effect will be short-lived.

The occurrence of cracks in the cement ring will also contribute to a decrease in adhesion between pine rosin and the borehole walls.

The technical result that can be obtained by implementing the present invention is as follows: the efficiency of the insulating work in wells is improved by using a sealing composition with improved technological properties due to increased plasticizing properties, adhesion of the composition to the surfaces of technical and production columns; and, as a result, the overhaul period of the well increases.

The technical result is achieved by the well-known sealing composition for insulating work in a well, consisting of a clogging agent, a plasticizer and an organic solvent, which contains synthetic camphor as a clogging agent, a polyvinyl butyral film as a plasticizer, and isopropyl alcohol as an organic solvent, in the following ratio ingredients, wt.%:

Camphor synthetic 1-49 Polyvinyl Butyral Film 1-6 Isopropyl alcohol rest

The inventive sealing composition meets the condition of "novelty."

To prepare the sealing composition, synthetic camphor is used, grade A according to TU 13-0281078-28-70-78, a polyvinyl butyral adhesive film according to GOST 9438-85, isopropyl alcohol according to GOST 9805-84.

The combined use in the recipe of the proposed sealing composition of the ingredients in the specified content ensures the effectiveness of the insulating work in the well.

Synthetic camphor is a hydrophobic substance, however, the presence of a polar ketone group in the camphor molecule (= C = O) allows it to dissolve in aliphatic alcohols, and its solubility is very high, for example, 1 g of camphor dissolves in 1 ml of 90% ethyl alcohol. The high solubility of synthetic camphor allows it to be used as a colmatizing agent to eliminate annular pressure when isolating annular and annular spaces, and re-sealing threaded joints of casing strings.

Isopropyl alcohol is a volatile solvent, the size of the molecule is much smaller than the diameter of the capillaries and pores in the cement stone. Molecules of isopropyl alcohol can be removed through this porous medium due to their adsorption by cement stone. The camphor solution is highly concentrated, close to saturation, the removal of isopropyl alcohol also leads to an increase in the concentration of synthetic camphor in the solution. Synthetic camphor is adsorbed on the surface of pores (chemisorption); nuclei of the crystalline phase of camphor are formed due to the adsorption process. Germ growth occurs to crystal growth. The latter provides the composition with a long crystallization time. The crystalline mass first clogs the small pores and capillaries, and then the leakage zone. This is because the ratio of the diameter of the channels of the leakage zone to the diameter of the capillaries is of the order of hundreds and thousands. Another factor causing the precipitation of the camphor synthetic camphor crystals is the presence of water. Adsorbed water is always present in cement stone. Isopropyl alcohol is a hygroscopic substance, i.e. easily absorbs moisture, which has a salting effect on camphor. Use as a plasticizer - polyvinyl butyral film helps to reduce the fragility of synthetic camphor. This is due to the following: high molecular weight polyvinyl butyral is adsorbed on the faces of growing camphor crystals, crystal growth is interrupted, new nuclei of the crystalline phase of camphor are formed. In turn, camphor can act as a plasticizer for polyvinyl butyral. The mechanism of plasticizing action is as follows. Camphor molecules penetrate into the interstructural spaces of the polymer, while an insignificant amount of camphor truly dissolves in the polymer, the molecules of which are adsorbed on the interstructural interface, forming the thinnest monomolecular layers of the so-called boundary lubrication, which facilitates the mobility of supramolecular structures.

The presence of a large number of small-sized crystals of camphor and polybutyral component between the crystals increases the plasticity of the polycrystalline mixture, which increases the efficiency of insulation work. As a result, a uniform sealing composition with the necessary low viscosity properties is formed, which ensures its deep penetration into the leakage zone.

The sealing composition is characterized by increased adhesion to cement stone, which is due to the following: a solution of camphor and polyvinyl butyral in isopropyl alcohol moistens the metal surface of technical and production columns well, as a result of which close contact between the molecules and functional groups of polyvinyl butyral, camphor and metal molecules is ensured. Then there is a direct interaction of the colmatants and the metal surface, which is caused by various forces - from Van der Waals to chemical. Such intermolecular interaction of the contacting phases leads to increased adhesion, which corresponds to the minimum interfacial energy. The course of the described processes leads to the formation of a durable fluid-tight sealing frame, reliably adhered to the surface of the pipes, eliminating the annular gas manifestations. The above leads to an increase in the efficiency of the ongoing insulation work and the overhaul period of the well increases.

The content of the polyvinyl butyral film in the sealant composition of less than 1 wt.% And synthetic camphor of more than 49 wt.% Is impractical, since synthetic camphor will not completely dissolve, which will not allow the composition to fill the leakage zone and does not ensure the effectiveness of insulation work.

The content of the polyvinyl butyral film in the sealing composition of the film is more than 6 wt.% And synthetic camphor less than 1.0 wt.% Is impractical, since the polyvinyl butyral film does not completely dissolve, which complicates the insulation work.

Thus, according to the above, the proposed combination of essential features ensures the achievement of the claimed technical result.

Not identified by available sources of fame, technical solutions having features that match the distinctive features of the invention according to the claimed technical result.

The inventive sealing composition meets the condition of "inventive step".

In more detail, the essence of the claimed invention is described by the following examples.

Example (fishing)

Work is underway to eliminate gas in the annulus between the production and technical columns of the UGS well.

Initial data

Column Column Diameter mm Departure Depth, m Cement rise behind the column, m Direction 630 23 mouth Conductor 426 274 mouth Technical 324 390.84 to the mouth Technical 245 979.58 to the mouth Operational 168 1144.11 to the mouth

Fountain fittings AFC 3-65 × 210.

Column head OKK-1-210 - 168 × 245.

The reservoir pressure is 11.6 MPa.

The pressure in the annular space P _{mkp168 × 245} = 136 MPa.

The cause of the intercolumnar gas manifestations is the leakage of the cement ring between production and technical columns. Carrying out insulation work involves filling the gas-conducting channels in the annular space with a sealing composition. The main parameters characterizing the annular space of the well (flow rate of constant gas inflow - q _pp and its void volume - V _{microprocessor} ) are set at the stage of production of the annular fluid. The fluid is released until the cessation of its output or the establishment of a constant flow rate. Based on the results of gas-dynamic studies, the total capacity of the fluid-conducting channels in the annular space is determined by the formula

,

,

where V _MCP is the void volume of the annular space, m ³ ;

V _G - the volume of gas released, m ³ ;

ρ ₁ - gas density at the installation site of the gas meter, kg / m ³ ;

q _PP - flow rate of constant gas flow, m ³ / h;

ρ ₂ - the average density of the gas in the annular space, kg / m ³ ;

t is the total time of gas release, h

Prepare 0.1 m ³ sealing composition with a ratio of ingredients, wt.%:

Camphor synthetic 25 Polyvinyl Butyral Film 3 Isopropyl alcohol 72

91.7 l (72 wt.%) Of isopropyl alcohol is poured into a 0.2 m container. In small portions, thoroughly mixing, add 3 kg (3 wt.%) Of the crushed polyvinyl butyral film. After complete dissolution of the polyvinyl butyral film, thoroughly mixing, add 25 kg (25 wt.%) Synthetic camphor.

Work procedure:

1. Bleed the gas from the annular space 168 × 245 mm

2. Mount the injection line from the CA-320 unit to the annular space of the well 168 × 245 mm. The pressure line is tested at 5.0 MPa.

3. The operation of the unit CA-320 is pumped into the annular space sealing composition in a volume of 0.1 m ³ .

4. Mount the discharge line from the SDA 101/10 compressor into the annular space of 168 × 245 mm and inject gas (nitrogen) up to 4.0 MPa. Close the annulus and leave for 48 hours to wait for the composition to solidify. Dismantle the discharge line.

Example (fishing)

Work is underway to re-seal the threaded joints of the production string at the UGS well.

Initial data

Column The diameter of the column, d _e mm Departure Depth, m Cement rise behind the column, m Direction 630 twenty to the mouth Conductor 426 243.4 to the mouth Technical 324 383.0 to the mouth Technical 245 895.0 to the mouth Operational 168 1142.39 to the mouth

The reservoir pressure P _PL = 11.57 MPa.

The pressure in the _annulus P _{MK168 × 245} = 0.7 MPa.

The UGS well was investigated by the GIS complex. According to the results of studies in the well, the following was established:

1. According to thermometry, the place of leakage of the threaded connection of the production string at a depth of 38.5 m is noted.

2. According to acoustic cementometry, a change in the wave pattern before and after pumping gas into the annular space indicates the movement of gas through the annular space.

3. The head of the cement bridge is at a depth of 41 m.

The volume of the sealing composition for work V is determined by the formula

,

,

where h is the insulated interval of the production casing, m (taking into account the safety factor is taken equal to 4.5 m).

V = 0.785 · 0.168 ² · 4.5 = 0.1 m ³ .

Prepare 0.1 m of the sealing composition at a ratio of ingredients, wt.%:

Camphor synthetic one Polyvinyl Butyral Film 6 Isopropyl alcohol 93

118.5 l (93.0 wt.%) Of isopropyl alcohol are poured into the measuring unit of the cementing unit CA-320. In small portions, thoroughly mixing, add 6 kg (6 wt.%) Of the crushed polyvinyl butyral film. After complete dissolution of the polyvinyl butyral film, thoroughly mixing, add 1 kg (1 wt.%) Synthetic camphor.

Work procedure:

1. Free pouring onto a suspended cement bridge installed at a depth of 41 m (tubing raised) pour 0.1 m of the sealing composition.

2. Bind the space of the well with a compressor, with the help of which a pressure of 9.5 MPa was created.

3. The well is left under pressure to wait for the composition to solidify. After 72 hours, the pressure in the pipe space is vented.

4. Drill a cement bridge.

After insulation work, the pressure in the annulus

P _{mkp168 × 245} = 0. Consequently, the use of a sealing composition made it possible to eliminate leaks in threaded joints.

Examples No. 1 (laboratory)

To prepare 1000 g of the sealing composition in 637 ml of isopropyl alcohol with a density of 0.785 g / cm ³ (50.0 wt.%), Thoroughly mixing, add 10 g (1 wt.%) Of the crushed polyvinyl butyral film. After complete dissolution of the polyvinyl butyral film, thoroughly mixing, add 490 g (49 wt.%), Synthetic camphor. The technological properties of the sealing composition are determined: kinematic viscosity τ = 3.12 cSt, crystallization time t = 8 h, adhesion to metal P _m = 0.50 MPa, gas permeability:

before processing K = 6.87 μm ² , after processing K ₁ = 0.04 μm ² , K _g = 99.4%.

Example No. 2

Prepare 1000 g of the sealing composition, g / wt.%:

Camphor synthetic 250/25 Polyvinyl Butyral Film 30/3 Isopropyl alcohol 720/72 (which is   917 ml, ρ = 785 kg / m ³ )

All operations are carried out, as in example No. 1.

The sealing composition has the following technological properties: τ = 5.83 cSt, t = 17 h, P _m = 0.73 MPa, K = 6.63 μm ² , after K ₁ = 0.03 μm ² , K _g = 99, 5%.

Example No. 3

Camphor synthetic 10/1 Polyvinyl Butyral Film 60/6 Isopropyl alcohol 930/93 (which is   1185 ml, ρ = 785 kg / m ³ )

All operations are carried out, as in example No. 1.

The sealing composition has the following technological properties: τ = 8.70 cSt, t = 26 h, P _m = 0.94 MPa, K = 6.03 μm ² , K ₁ = 0.07 μm ² , K _g = 98.8 %

Thus, the claimed technical solution meets the condition of "novelty, inventive step, industrial applicability", that is, is patentable.

Claims (1)

A sealing composition for insulating work in a well, consisting of a clogging agent, a plasticizer and an organic solvent, characterized in that it contains synthetic camphor as a clogging agent, a polyvinyl butyral film as a plasticizer, and isopropyl alcohol as an organic solvent in the following ratio of ingredients , wt.%:
Camphor synthetic 1-49 Polyvinyl Butyral Film 1-6 Isopropyl alcohol rest