RU2322569C2 - Method for production well repair - Google Patents

Abstract

FIELD: oil and gas industry, particularly to repair leaking production strings, to eliminate behind-the-casing flows in cased wells.

SUBSTANCE: method involves injecting hydrophobic emulsion solution in production well; supplying viscoelastic foam therein; delivering cement mix via tubing; leaving well as it is for cement mix hardening time. Viscoelastic foam is prepared on ground surface. Viscoelastic foam includes (% by weight) polymer (0.5-5), cross-linking agent (0.1-3), foaming agent (0.2-5) and water phase (87-99.2). Hydrophobic emulsion solution includes (% by weight) oil (30-50), water phase (40-68) and emulsifier (2-10). Polymers, cross-linking agents, foaming agents and water phases of different types are used. To prepare foam with 0.2-5 expansion ratio gaseous agents are injected during foaming operation.

EFFECT: increased plugging solution efficiency, possibility to change flow characteristics and penetration factor of plugging solution in reservoir conditions, decreased cement mix consumption.

7 cl, 2 tbl, 2 ex, 4 dwg

Description

The invention relates to the oil and gas industry and can be used to eliminate leaks in production casing, as well as repair and insulation work on the elimination of annular flows in cased oil and gas wells.

There is a method of repair and insulation work, when a polyurethane prepolymer with a content of isocyanate groups of 2-30% mixed with diesel fuel and with a quantity of diesel fuel of 20-30% is fed into the repaired area. Then anhydrous liquid and an aqueous solution with a thickener are again fed. Bring all these process fluids to the repaired interval and push them into the repaired zone with a productivity of 2.5-3.5 l / s. As a result of curing and foaming of the isocyanate in the presence of produced water, cavities and washed cavities are filled with cured polymer material with the elimination of the absorption zone [RF Patent No. 2231625, cl. MKI E21B 33/138, published 2004.06.27].

The disadvantage of this method is that curing occurs only in the presence of moisture instantly, without ensuring uniform distribution of the material, which does not provide a durable sealed material in the field of repair work. In addition, the high reaction rate with water does not preclude premature curing in the wellbore.

The closest in technical essence and the achieved result is the method of repair work in the production well during the liquidation of casing leakage, selected as the prototype, which provides increased reliability of the insulation of the string and reduced cement consumption, which consists in pumping tubing through the string (tubing) viscoelastic composition and cement slurry. This is done with the annular space of the borehole open, the viscoelastic composition is positioned below the lower boundary of the casing leakage before the cement is pumped into the tubing string [RF Patent No. 2170333, cl. MKI E21B 33/13, published 2001.07.10].

The inefficiency of this method is explained by the following. The viscoelastic composition is located below the casing leakage before the cement pack is injected, while waiting for the cement to solidify, the OZC does not exclude the possibility of plug replacement due to the gravitational pressure of the cement pack due to the difference in the specific gravity of the materials. The specific gravity of the cement and viscoelastic composition is 1.8-1.9 g / cm ³ and 1.0-1.1 g / cm ^3, respectively. In addition, if that part of the column where there is no cement ring is damaged in the interval of occurrence of cavernous absorbing layers, then significant volumes of the plugging mixture have to be pumped through the damage zone into the annulus. However, after drilling a cement cup left in the damage zone, the tightness is not restored, which is explained by intensive dilution of the mixture in the annular space.

As a result, it is not possible to obtain a durable cement stone in the field of eliminating leaks in the production casing.

The task of the invention is to increase the reliability of cementing of the repaired zone of the production string by changing the rheological properties of the plugging material in reservoir conditions.

This object is achieved in that in order to prevent dilution of the cement slurry with formation fluids, a method for repair work in a production well is proposed, which includes sequential injection into the formation of a selective water-insulating composition containing oil - 30-50, the aqueous phase - 40-68, emulsifier 2-10; then a structure-forming material for the cement mortar, namely a viscoelastic foam containing a polymer of 0.5-5, a crosslinker of 0.1-3, a blowing agent of 0.2-5, an aqueous phase of 87-99.2; then cement mortar.

The need for preliminary injection of a selective water-insulating composition is as follows. The water-insulating composition is an inverse emulsion consisting of a hydrocarbon phase (most often oil), an aqueous phase (produced water or saline solution: calcium chloride solution and / or sodium chloride solution) and an emulsifier (emulsion and / or Neftenol NC). The ingredients of the composition are selected taking into account the geological conditions of the reservoir: temperature, injectivity of the reservoir, the composition of the fluids. On the one hand, the emulsion solution absorbs associated water in the well and in the isolated interval, as a result of which the emulsion is structured to form a hydrophobic-emulsion solution with a hydrocarbon external phase with high rheological properties. As a result, a strong waterproofing screen is created in the formation in water layers. The change in dynamic viscosity due to the absorption of produced water by the composition of figure 1.

On the other hand, in the event that the emulsion enters the oil-containing intervals, the oil dissolves in the emulsion solution without violating the permeability to the oil interlayers.

After a technological exposure of 10-30 minutes, a viscoelastic foam is prepared based on a polymer of 0.5-5, a crosslinker of 0.1-3, a blowing agent of 0.2-5, and an aqueous phase of 87-99.2. The polymer used is an aqueous solution of polyacrylamide, and / or a solution of carboxymethyl cellulose - CMC, and / or a solution of sodium styrene maleate. Potassium chrome alum and / or potassium dichromate, and / or sodium dichromate, and / or aluminum-ammonium alum are used as a crosslinker. As a blowing agent, alkyl benzene sulfonic acid and / or sulfanol and / or neftenol are used. VVD is a broad-spectrum technical surfactant, TU 2483-015-17197708-97.

Viscoelastic foam is prepared using a booster unit or cementing unit CA-320 and a compressor by mixing the components. The prepared solution of the polymer, blowing agent and crosslinker is foamed with the help of a dispersant and compressor in the capacity of the unit and pumped through the tubing into the reservoir. Once in the reservoir, viscoelastic foam expands under the influence of temperature, hardens in the presence of a fixative and fills cavities and washed areas, and a water-insulating screen allows you to maintain the ratio of ingredients during the structuring of the composition. Thus, a porous viscoelastic foam with high structural and mechanical properties is formed in the repair zone. The density of the obtained composition varies between 0.4-0.9 g / cm ³ . After technological exposure of 10-30 minutes, a cement mortar with a water-cement ratio of 0.3-0.5 is pumped.

Cement mortar by the nature of the flow is a pseudoplastic fluid, characterized by high values of CHS and plastic viscosity. And this indicates that after the application of voltage above the SSS, the structural network is destroyed and the cement mortar flows like a normal viscous fluid.

In the proposed method, the cement slurry is advanced in the repair zone, filling the viscoelastic foam with attenuation in the radial direction with a stop. As a result, a change in the rheological behavior of cement occurs: in the area of the cement ring near the well wall, pseudoplastic cement is structured, as it moves away from the well, the cement acquires viscoelastic properties with high SSS values, the ultimate dynamic shear stress due to penetration of the viscoelastic foam into the porous structure. These rheological properties do not allow the spreading of the cement mortar. Obtained in voids and caverns, the composition hardens and fixes the formation, redistributing the flows of formation fluids.

Curves of the flow of cement, viscoelastic foam and compositions based on viscoelastic foam and cement are shown in figure 2.

In laboratory conditions, physicochemical studies of the cement mortar and compositions based on viscoelastic foam and cement mortar, as well as the properties of the resulting cement stone and cement stone when mixed with viscoelastic foam (Table 1), and the porosity of the obtained cement stone when mixed with viscoelastic foam according to as you move the plugging composition (cement mortar) in the radial direction (figure 3).

Figure 3 shows that the porosity of the cement stone in the zone of the cement ring without adding viscoelastic foam is absent, that is, a strong cement stone is formed. As you move, the cement mortar is bonded with viscoelastic foam to produce a cement stone of varying porosity with an OZC.

Figure 4 shows a photograph of the obtained porous cement stone with an increase of 90 times.

As can be seen from the data in table 1, the static shear stress characterizing the stress at which shear occurs for the composition of the cement mortar with viscoelastic foam during injection is 450-500 dPa, which is 5 times higher than the cement mortar. The ultimate dynamic shear stress, which characterizes the strength of the structural mesh, which must be destroyed in order to ensure a flow with a certain plastic viscosity, is absent for a cement mortar. This is because the cement mortar does not have a strong structure and elastic properties, while for a viscoelastic foam composition with a cement mortar this value is 1200-1500 dPa, which indicates the formation of a structured viscoelastic cement mortar, the flow of which begins after applying a higher voltage the specified values. During the OZC period, a strong cement stone is formed in the cementing zone; in the fastening zone, the composition is hardened to form a porous cement stone, which has good adhesion to both the cement ring and the formation rock. Cement remains at the WPC with further drilling.

To prove the conformity of the claimed invention to the criterion of industrial applicability, the technology was used in the field conditions for wells No. 1079 and No. 370.

Case Studies

Example 1

In well No. 1079, bush No. 41 of the Vatensky field, insulation work was performed by the proposed method.

According to geophysical data, a leakage section was identified, located in the interval 1318-1319 m, the Senoman layer. Before treatment, the injectivity of the well was 720 m ³ / day at a pressure of 10 atm.

The geological and technical parameters of well No. 1079 are given below.

Plast Senoman

Formation temperature 45 ° C Isolation interval 1318-1290 m Tubing descent depth: When downloading, when selling and cutting 1290 m When OZZ 1200 m.

In order to limit the breakthrough of water in this well, an emulsion composition of 3 m ³ was prepared using a cementing unit CA-320 by mixing the components in a measuring device. The aqueous phase was 50%. The thermal stability at 45 ° C was 100%, and the aggregative stability was 100%. The emulsion was pumped into the reservoir through tubing. As we moved along the wellbore and the formation, the pressure increased: initially 10 atm and the injection was completed at a pressure of 50 atm. The increase in pressure was due to the structuring of the emulsion with the absorption of associated water. To further strengthen the structural grid, the well was left at the OZS for 2 hours.

Viscoelastic foam “Aerogel” was prepared using a dispersant and a compressor in the measuring unit of the CA-320 unit. The density of the composition "Airgel" was 0.7 g / cm ³ . Injection into the formation was carried out through tubing at the lowest unit speed. Injection pressure 10/60 atm. To further uniformly distribute the composition in voids and cavities and structure the composition, the well was left at the OZS for 2 hours.

Cement was poured with cement mortar with a volume of 5 m ³ with a delivery at the end of 130 atm with a Stop stop. After 32 hours, cement stone was drilled. Tightness restored. The well was successfully put into operation - Q fluid - 112 tons / day, Q oil - 30 tons / day.

Example 2

In well No. 370 bush No. 34 of the Agan field, insulation work was performed by the proposed method.

According to geophysical data, a leakage area was identified, located in the interval 1501.5-1502 m, the Senoman formation. Before treatment, the injectivity of the well was 540 m ³ / day at a pressure of 60 atm.

The geological and technical parameters of well No. 370 are given below.

Plast Senoman

Formation temperature 45 ° C Isolation interval 1481-1503 m Tubing descent depth: When downloading, when selling and cutting 1481 m When OZZ  1331 m.

In order to limit the breakthrough of water in this well, an emulsion composition of 3 m ³ was prepared using a cementing unit CA-320 by mixing the components in a measuring device. The aqueous phase was 70%. The thermal stability at 45 ° C was 100%, and the aggregative stability was 100%. The emulsion was pumped into the reservoir through tubing. As we moved along the wellbore and formation, the pressure increased and the injection was completed at a pressure of 130 atm. The increase in pressure was due to the structuring of the emulsion with the absorption of associated water. To further strengthen the structural grid, the well was left at the OZS for 2 hours.

Viscoelastic foam “Aerogel” was prepared using a dispersant and a compressor in the measuring unit of the CA-320 unit. The density of the composition "Airgel" was 0.6 g / cm ³ . Injection into the formation was carried out through tubing at the lowest unit speed. The injection pressure did not exceed 50 atm. To further uniformly distribute the composition in voids and cavities and structure the composition, the well was left at the OZS for 2 hours.

They made cement pouring with a cement mortar with a volume of 4.2 m ³ while selling at the end of 120 atm with a Stop stop. After 32 hours, the cement stone was drilled, the tightness was restored.

The use of the invention allows to reduce the consumption of cement mortar and increase the reliability of isolation while eliminating leaks in the casing in the intervals of the production well, eliminates annulus flows, improves the fastening of washed zones and reservoir cavities, and also eliminates the need for repeated operations for absorbing wells.

Table 1 Physico-chemical and rheological properties of the cement mortar and the composition of viscoelastic foam with cement mortar (structured cement mortar). # №№ The name of indicators Cement mortar with a water-cement ratio of 0.46 Viscoelastic foam containing 60% vol. cement mortar with a water-cement ratio of 0.46 (structured cement mortar) At a temperature of 45 ° C At a temperature of 63 ° C At a temperature of 28 ° C At a temperature of 63 ° C one Start 2 1,5 four 3,5 setting time 2 the end 6 four 8 7 setting time 3 Density, g / cm ³ 1,900 0.850 four Viscosity 215 187 1000 900 plastic MPa · s 5 Limit one hundred 80 1500 1200 dynamic voltage shear, dPa 6 Static one hundred 80 500 450 voltage shear, dPa 7 Water loss, cm ³ 5 0 8 Filtration, cm ³ 5 0 9 Coefficient 0 64,2 porosity,% 10 Coefficient 0 120.5 permeability mld

Claims (7)

1. A method of carrying out repair work in a production well, including injecting viscoelastic material into it, then injecting cement slurry through the tubing string and leaving the well to wait for cement to harden — OZC, characterized in that viscoelastic foam is used as a viscoelastic material, which is prepared on the surface in the following ratio of components, wt.%: Polymer 0.5-5 Stapler 0.1-3 Blowing agent 0.2-5 Water phase 87-99.2 and before the specified viscoelastic foam is injected into the formation, a selective water-insulating composition — a hydrophobic-emulsion solution — is injected in the following ratio of components, wt.%: Oil 30-50 Water phase 40-68 Emulsifier 2-10. 2. The method according to claim 1, characterized in that the polymer used is carboxymethyl cellulose - CMC, and / or sodium styrene maleate, and / or polyacrylamide. 3. The method according to claim 1, characterized in that potassium chrome alum and / or potassium dichromate and / or sodium dichromate and / or aluminum-ammonium alum are used as a crosslinker. 4. The method according to claim 1, characterized in that, as a blowing agent, alkylbenzenesulfonic acid and / or sulfanol and / or neftenol VVD are used. 5. The method according to claim 1, characterized in that the fresh water and / or produced water and / or produced water and / or calcium chloride solution and / or sodium chloride solution are used as the aqueous phase. 6. The method according to claim 1, characterized in that a 10-20% solution of isopropyl alcohol and / or methyl alcohol and / or ethyl alcohol and / or triethylene glycol and / or ethylene glycol is used as the aqueous phase. 7. The method according to claim 1, characterized in that for the preparation of the specified viscoelastic foam with a multiplicity of foam 0.2-5, foaming is performed using a gaseous agent - air, and / or nitrogen, and / or natural gas.

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