RU2277626C1 - Insulation composition and method of well tubing-casing annulus plugging - Google Patents

Abstract

FIELD: oil production industry, particularly methods and devices to prevent showings of oil and gas in cemented tubing-case annulus.

SUBSTANCE: insulation composition includes solution comprising urethane pre-polymer, solvent and hardener - water. The solvent is polar solvent chosen from aromatic series or from chlorinated hydrocarbon series. The water is mineralized water containing surfactant additive. All above components are taken in the following amounts: urethane pre-polymer - 20-75 parts by weight, solvent - 25-80 parts by weight, hardener - 1.5 parts by weight per 100 parts by weight of the solution. Tubing-casing annulus plugging method involves filling fluid channels of cemented tubing-casing annulus with above insulation composition in four stages. At the first stage gaseous agent is injected in the tubing-casing annulus up to full liquid phase displacement from fluid channels. At the second stage the channels are filled with hydrocarbon waterless liquid having low viscosity and increased penetrability. At the third stage above urethane pre-polymer composition is injected in tubing-casing annulus. At the forth stage tubing-casing annulus is filled with hardener.

EFFECT: possibility of tubing-casing annulus plugging by injection method without well operation stoppage, increased plugging quality due to increased composition penetration depth and increased fullness of fluid channel filling.

2 cl, 4 tbl

Description

The invention relates to the oil and gas industry, in particular, to compositions and methods for eliminating oil and gas occurrences along a cemented annular space of wells by isolating (sealing) fluid-conducting channels and cracks connecting pressure beds with a day surface.

A known method of isolating absorption zones, according to which an increase in insulation efficiency can be achieved by eliminating contact of the plugging material with water when it is delivered to the formation (RU 95106388 A1, 01/27/97). To do this, before injecting a urethane prepolymer into the well, polyhydric alcohols, for example diethylene glycol, are injected. However, as was noted, when mixing the urethane prepolymer and alcohol, the viscosity of the grouting material quickly increases and its access to micropores and channels of low opening is limited. Therefore, this method also does not provide reliable sealing of fluid-conducting channels in the annulus of the wells.

There is a known method of repair and insulation work, according to which an anhydrous liquid is preliminarily supplied to the area to be repaired, then a mixture of a urethane prepolymer (for example, "URENAT-5449") with diesel fuel, anhydrous liquid again and a hardener - an aqueous solution with a thickener (for example, CMC) (RU 2231625 C1, 06.27.2004).

Process fluids are forced into the repaired area with a productivity of 2.5-3.5 l / s.

The disadvantages of the method include:

1) a mixture of urethane prepolymer and diesel fuel due to poor solubility and difference in density of liquids quickly stratifies. As a result of partial delamination (uneven distribution) of the mixture components, uneven filling of the channels to be insulated occurs, the risk of breakthrough of gaseous fluids increases;

2) the presence of a thickener of the CMC type in the hardener (water) increases the viscosity of the latter, which will limit its access to long-distance microchannels.

Due to the above reasons, a poor-quality mixture enters the insulated channels, which may not solidify at all and therefore cannot serve as reliable protection against gas breakthrough.

In addition, the practical implementation of this method of injecting an insulating composition involves shutting down the well, killing it and transferring it to overhaul.

The closest technical solution is the grouting composition for local sealing of the annulus and annulus and protection of wells from annular and annular flow of liquids and gases (RU 2132448 C1, 06.27.99). The composition contains glue brand VILAD-17 (urethane prepolymer), hydrocarbon solvent (C ₃ -C ₁₆ ), monohydroxy primary alcohol, amino alcohol, neutral fine powder and water. Modifying additives (solid phase, alcohols) are introduced to increase the adhesion and strength of the grouting material, as well as to accelerate the curing process.

A disadvantage of the known composition is that in the presence of potential hardeners (OH components), even before the injection, the polycondensation reaction begins, which is accompanied by an increase in the viscosity of the initial composition. It quickly loses mobility, its transportation time is reduced, which complicates the use of the composition for isolating microchannels in the annulus of the wells, especially when pumping from the wellhead. In addition, the penetration depth of the composition is limited by the size of the solid phase in it. As a result, reliable protection is created only against liquid fluids, and the gas gradually finds unfilled finely porous areas and forms a breakthrough channel, i.e. long-lasting sealing effect is not achieved.

The objective of the invention is to develop an insulating composition and method of sealing the annulus of the well by wellhead injection without stopping the operation of the well, providing high quality insulation by increasing the depth of penetration of the composition and more complete filling of the fluid-conducting channels.

The essence of the invention lies in the fact that the insulating composition for the fluid channels in the cemented annular space of the wells, including a solution containing a urethane prepolymer, a solvent and a hardener - water, contains as a solvent a polar solvent of an aromatic series or a series of chlorine derivatives of hydrocarbons, and as a mineralized water water with the addition of a surfactant surfactant, in the following ratio of components, parts by weight:

urethane prepolymer 20-75,

the specified solvent 25-80,

the specified hardener 1-5 per 100 wt.h. solution.

The proposed method of sealing fluid-conducting channels in a cemented annular space of wells, including filling these channels with the above-mentioned insulating composition containing a urethane prepolymer, is carried out in four stages:

- at the first stage, a gaseous agent is injected into the annular space until the liquid phase is completely displaced from the fluid-conducting channels;

- at the second stage, these channels are filled with anhydrous hydrocarbon liquid with a low viscosity and high penetrating power;

- at the third stage, the specified solution of the urethane prepolymer is pumped;

- at the fourth stage, the specified hardener is injected.

As a hydrocarbon liquid with a low viscosity and high penetrating ability, for example, kerosene and gasoline fractions of oil are used.

To prepare a urethane prepolymer solution, polar aromatic solvents (toluene, xylene, nefras-A) are used, as well as chlorinated hydrocarbons (dichloromethylene, dichloroethane and mixtures thereof, the composition of the APC), which, due to their good dissolving ability and inertness to residual isocyanate groups, allow stable in time, the initial solutions of urethane prepolymers with low viscosity indices (2-11 MPa · s). This improves transport capabilities and provides a greater penetration depth of the solution.

The transportation of the polar solution of the urethane prepolymer through channels filled with kerosene occurs by the mechanism of gravitational substitution, i.e. due to the difference in density of the displaced (kerosene) and displacing (urethane prepolymer solution) liquids.

After delivery of the urethane prepolymer solution to the required depth, hardener is introduced. Mineralized (i.e., fresh with the addition of water-soluble salts, sea or formation) water with a surfactant (neonol, oxanol, OP-7, etc.) is used as a hardener. Its salts provide an increase in the density of the hardener relative to previously introduced liquids and reduce the cure rate of the urethane prepolymer. The addition of surfactants in working concentrations reduces the magnitude of interfacial tension, which increases the speed of delivery of the hardener due to gravitational substitution to a given depth.

In field conditions, the calculation of the required depth of entry of the insulating composition into the annular space and the required volumes of components is carried out according to the results of preliminary diagnostic tests of the well.

To prepare the compositions, the ADV product was used as a polyurethane prepolymer, which is a polyisocyanate-based urethane oligomer manufactured according to TU 2226-023-22736960-96, and foreign products, for example, the Japanese company Toho Chemical Ind. Highsel brand with a mass fraction of free isocyanate groups of 2-10%. As a polar organic solvent, toluene, xylene, and the APC composition, which is a technical mixture of ethane and methane chlorocarbons, were used (TU 2122-232-057634-5897). As hardener - fresh water with additives of neonol, oxanol and CaCl ₂ and sea water with additives of neonol and OP-7.

The proposed composition and method for isolating fluid-conducting channels is tested in laboratory and bench conditions in comparison with the selected prototype prepared in accordance with the description.

The formulations of insulating compositions and dynamic viscosity values (η, MPa · s) of prepolymer solutions are shown in table 1.

Table 1. Component Name Dynamic viscosity, MPa · s Amount, parts by weight,% Composition 1. ADV 2 twenty Toluene
Hardener (fresh water + 0.3% neonol + 2% CaCl ₂ ) 80
one Composition 2. ADV 5 40 m-xylene 60 Hardener (sea water + 0.3% neonol) 2 Composition 3. ADV 6.5 fifty m-xylene fifty Hardener (fresh water + 0.5% oxanol + 3% CaCl ₂ ) 5 Composition 4.
Heisel OH-822
Agribusiness
Hardener (sea water + 1.0% OD-7)
9
75
25
four Composition 5 - prototype
Vilad-17
Petrol
Propylene
DEA
Graphite
Hardener (water)
57
45
35
3,5
4,5
8
four

The penetrating power of insulating compounds was evaluated by the following method. Kerosene was poured into a capillary polyethylene tube with an inner diameter of 1 mm and a length of 1 m, the lower part was closed with a clamp, a measuring device was installed on top. The prepared urethane prepolymer solution was poured into a measuring device. In laboratory tests, the process of gravitational substitution was observed visually along a clear interface between immiscible liquids of various densities, as well as by measuring the volume of displaced kerosene.

After a certain period of time (after the urethane prepolymer solution settles to the bottom of the tube), a hardener is introduced through the meter, which, due to its higher density and surfactant, quickly settles to the bottom of the model channel.

At the end of the aging period, the tubes were cut and the quality of the cured insulating compositions was evaluated.

Similarly, experiments were carried out on model samples of cement stone 100 cm long with artificial channels 1 mm in diameter. To fix the moment of solution settling to the bottom of the channel, a transparent capillary was attached to the bottom of the model sample.

The test results are shown in table 2.

table 2 Composition number Channel view The settling time of the solution, min Hardener settling time, min. The exposure time, days. Type of end product at the bottom of the channel Composition 1 plastic capillary 2 17 3 solid Composition 2 plastic capillary 3 fourteen 3 solid Composition 3 plastic capillary four 17 3 solid Composition 4 plastic capillary four fifteen 3 solid Composition 5-prototype plastic capillary 8 does not enter the bottom of the channel 3 liquid Composition 1 cement 3 17 2 solid Composition 2 cement 5 fifteen 2 solid Composition 3 cement 5 eighteen 2 solid Composition 4 cement 6 16 2 solid Composition 5- prototype cement fourteen does not enter the bottom of the channel 2 liquid

When using the proposed compositions in all cases, the penetration depth was maximum. All hardened compositions were an elastic, impermeable homogeneous mass, completely filling the cross section of the channel.

Technological efficiency (sealing effect, durability, gas permeability) of the proposed composition and method in comparison with the prototype was evaluated on a bench installation, which is a metal pipe with a diameter of 73 mm and a length of 60 cm with flange connections on both sides. A grouting mortar with increased insulating properties based on Portland cement was poured into the pipe to form an impermeable cement stone. During the formation of cement stone, a wall channel with a diameter of 1 mm was artificially formed in its structure. All samples were checked for the passage of the template (1 mm wire) through the formed channel.

During the experiments, the artificial fluid-conducting channel was filled with kerosene, and then a solution of a urethane prepolymer was successively introduced from above and, after the estimated time, a hardener.

After holding for 48 hours, the samples were pressed under a pressure of 5.0 MPa, which was provided by air supply through a pressure reducer from a cylinder.

The results of pressure testing of cement stone, including with an insulated fluid-conducting channel, are shown in table 3.

Table 3. Type of experience Pressure test, MPa Crimping time, min The final pressure of the crimping, MPa Output Original cement stone without channel 5,0 thirty 5,0 hermetically Original cement stone with channel 5,0 thirty 0 leaking Channel filled with composition 1 5,0 thirty 5,0 hermetically Channel 2 filled 5,0 thirty 5,0 hermetically Channel filled with composition 3 5,0 thirty fifty hermetically Channel filled with composition 4 5,0 thirty 5,0 hermetically The channel is filled with composition 5 (prototype) 5,0 thirty 0 leaking

Table 4 provides information on the fact of gas breakthrough through the test sample and the size of the breakthrough pressure (pressure during the tests gradually increased from 0 to 5.0 MPa).

As can be seen from table 4, the gas breakthrough pressure, when testing a sample sealed by the prototype method, was 0.63 MPa. In all other cases, gas breakthrough did not occur, including for samples aged for 28 days in a water bath at a temperature of 75 ° C.

The test results show that when using the proposed compositions and the method of isolation of the fluid-conducting channels in the cement stone, their reliable and long-term sealing is ensured.

Table 4. Type of experience Gas breakthrough pressure, MPa After 48 hours under normal conditions After 28 days at 75 ° C Original cement stone without channel no gas breakthrough no gas breakthrough Original cement stone with channel 0.01 - Channel filled with composition 1 no gas breakthrough no gas breakthrough Channel 2 filled no gas breakthrough no gas breakthrough Channel filled with composition 3 no gas breakthrough no gas breakthrough Channel filled with composition 4 no gas breakthrough no gas breakthrough The channel is filled with composition 5 (prototype) 0.63 -

The application of the proposed composition and method of its implementation will solve the problem of eliminating intercolumn pressures without stopping the operation of existing wells (oil, gas, injection) and provide high-quality and long-lasting sealing of fluid-conducting channels in the annulus of the wells.

Claims (2)

1. An insulating composition for fluid-conducting channels in a cemented annular space of wells, including a solution containing a urethane prepolymer, a solvent and a hardener — water, characterized in that it contains a polar solvent of an aromatic series or a series of chlorine derivatives of hydrocarbons, and a mineralized one as water water with the addition of a surfactant in the following ratio of components, wt. hours: Urethane prepolymer  20-75 Specified Solvent  25-80 Specified Hardener  1-5 per 100 parts by weight solution 2. A method of sealing fluid-conducting channels in a cemented annulus of wells, comprising filling these channels with an insulating composition containing a urethane prepolymer, characterized in that when using the composition according to claim 1, it is carried out in four stages: at the first stage, a gaseous agent is injected into the annular space until the liquid phase is completely displaced from the fluid-conducting channels; at the second stage, these channels are filled with anhydrous hydrocarbon liquid with a low viscosity and high penetrating power; at the third stage, the indicated urethane prepolymer solution is pumped; at the fourth stage, the specified hardener is injected.