RU2558558C1 - Well repair compound for oil and gas wells - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: well repair compound for oil and gas wells including urethane pre-polymer, hydrocarbon solvent and hardener comprises water-repelling urethane prepolymer as urethane pre-polymer, oxidised vegetable oil as hardener, acetone-soluble organic solvent, acetone or their mix as hydrocarbon solvent with the following mass ratio, wt %: water-repelling urethane pre-polymer 3-30, oxidised vegetable oil 5-50, the above organic solvent - remaining share at initial viscosity of the compound less than 200 cP and gel formation time within limits of 120-1500 minutes.

EFFECT: simplified repair works and improvement of repair quality.

2 ex, 1 tbl

Description

The present invention relates to the field of hydrocarbon production and can be used in underground repairs of oil and gas production wells.

A common method of repair work in the well is to extract the downhole equipment and inject into the well the composition or reagents with various additives prepared on the surface.

Analysis of existing compositions and technologies showed the following options [1-7]. The disadvantage of existing compositions is low penetration into the pores and cracks of the rock, premature polymerization, the complexity and complexity of the preparation due to the presence of many components, the poor adhesive properties of some compositions, the toxicity of the components used (environmentally unsafe), low tensile strength, as a result of which the data formulations have low efficiency.

The closest analogue in composition and effect achieved is a composition containing a polyurethane prepolymer and water, where the composition additionally contains a hydrocarbon solvent from the C3-C16 series, a monohydric primary alcohol from the C1-C5 series, an amino alcohol from the C2-C4 series, a neutral fine powder, and as a polyurethane prepolymer - polyurethane adhesive brand VILAD-17 and water. [8]

A disadvantage of the known composition is the short gel formation time due to the presence of water, which leads to premature polymerization of the composition. The multicomponent composition complicates the process of preparing the composition on the surface before injection into the well. Also, additional costly and time-consuming work is required to extract the downhole equipment for chemical treatment of the downhole interval.

These shortcomings reduce the technological efficiency of the composition for local sealing of the annulus and annulus, significantly limit the scope for use for the stated purpose.

The aim of the present invention is to simplify the work and improve the quality of repair work in oil and gas wells.

This goal is achieved in that the composition for repairing oil and gas wells, including a urethane prepolymer, a hydrocarbon solvent and a hardener, contains a hydrophobic urethane prepolymer as an urethane prepolymer, an oxidized vegetable oil as a hardener, and an organic solvent soluble in a hydrocarbon solvent. acetone, or acetone, or a mixture thereof in the following ratio of components, wt. %:

Urethane hydrophobic prepolymer 3-30 Oxidized vegetable oil 5-50 Specified Organic Solvent rest

with an initial viscosity of the composition of not more than 200 cP and gel time in the range of 120-1500 minutes

The essence of the claimed invention, providing that the proposed composition for repairing wells contains a urethane hydrophobic prepolymer and the indicated organic solvent and hardener at their indicated ratio, initial viscosity and gel time, is that these components at the claimed concentrations have mutual solubility, which allows get a homogeneous and low viscosity system. Oxidized vegetable oil contains in the composition of the oil molecules reaction groups that react with the isocyanate groups of the prepolymer. The consequence of this process is the formation of a polymer product, the strength of which depends on the initial concentration of the specified prepolymer and oxidized oil. The organic solvent used is acetone, a light hydrocarbon solvent soluble in acetone, or a mixture thereof. In this case, the requirement for the solvent is the complete mutual solubility in acetone. White spirit, gas condensate or solvents called “nefras” are used as a light hydrocarbon solvent. Oxidized oil - hardener can be obtained by thermal oxidation of vegetable oil at a temperature of 150-250 ^o C with atmospheric oxygen. It is advisable to use linseed, sunflower or any other vegetable oil containing polyunsaturated fatty acids as the starting oil. As a component of the repair composition, you can use a ready-made solution of oxidized vegetable oil in a hydrocarbon solvent under the trade name "drying oil." As a cross-linking agent, a urethane hydrophobic prepolymer of the Jowat trademark was selected. The specified hydrophobic prepolymer is obtained by the interaction of isocyanate and polyhydric alcohols [-OROCONHR′NHCO-] n. The initial viscosity of the composition should not exceed 200 cP and can vary up to 200 cP, and the gelation time should be in the range of 120-1500 min to enable the composition to be pumped into the well and completed within one day. The low viscosity provides favorable conditions for the pumpability of the composition into the zones and channels of leakage, as well as into the depth of the reservoir, if necessary. The claimed composition provides, when implementing the invention, an increase in the efficiency of repair and insulation works on isolating the leakage channels of the cement ring, eliminating leaks in the casing string, and can also be used to completely isolate the formation from liquid and gas entering the well.

Example 1

In this example, the results of determining the gelation time of the urethane hydrophobic prepolymer - oxidized oil - hydrocarbon solvent system are presented. The gelation time must be adjustable and be in the range from 30 minutes to several hours in order to be able to introduce the composition into the formation through downhole equipment. In laboratory conditions, the gelation time of the compositions of the urethane prepolymer, oxidized vegetable oil (oil "Oxol") and solvent was determined. The solvent used was a mixture of acetone and white spirit (experiments 1-10 in table 1), as well as a mixture of gas condensate with acetone (experiments 12-18). The gel duration of the urethane prepolymer - vegetable (oxidized) oil - solvent compositions is presented in Table 1. The results show that in a wide range of ratios between the urethane prepolymer, vegetable oxidized oil and solvent, the gel time corresponds to the conditions for pumping the composition into the well. From the presented data it can be seen that the composition within the claimed limits ensures compliance with the initial viscosity of not more than 200 cP and gel time within 120-1500 min to the declared limits, which ensures successful repair work at the well. From the results of experiment No. 11, in which the oxidized is not vegetable, but mineral oil, it is seen that in this case the gel does not form.

To confirm the possibility of using the claimed composition for sealing off-casing flows, experiments 12-18 were conducted, and the strength properties of the composition were studied in reservoir conditions. For this, non-cemented quartz sand was placed in a container and the pore volume was filled with a liquid solution of the urethane - oxidized vegetable oil - organic solvent system. A mixture of gas condensate with acetone and a mixture of white spirit and acetone were used as an organic solvent. After curing, a cylindrical core sample with a diameter of 30 mm and a height of 35-36 mm was cut. The uniaxial compression strength was determined by loading with a hydraulic press. Strength was evaluated by the pressure that destroys the sample. The results presented in the experiments in table 1 show that according to the strength properties of the samples of the repair material are in the range of 1.4-3.9 MPa, which corresponds to the strength of sandstones.

Example 2

To confirm the properties of the repair composition, the process of reagent injection into the reservoir was simulated to block leakage channels. For this purpose, a composition was prepared on the basis of 1.5 g of a urethane prepolymer, 14 g of a hydrocarbon solvent and 14 g of oxidized linseed oil in a mass ratio, wt.%: 5 - urethane prepolymer, 47.5 - oxidized vegetable oil and 47.5 - hydrocarbon white spirit solvent with an initial viscosity of 98 cP and a gelation time of 130 minutes Next, the composition was pumped into a tubular reservoir model D = 500 mm, L = 30 mm and kept for 24 hours. From one end of the tubular model of the reservoir, pressure was applied by a hydraulic pump with a supply of water, and on the other, a shut-off ball valve was installed to the base to regulate pressure relief and seal the lower base of the reservoir model.

After the reaction of the composition, water was injected into the reservoir model with a hydraulic pump at a constant volumetric water flow rate and a given pressure of 40 atm, close to the reservoir pressure.

After injection of pressure to 40 atm, the lower ball valve was opened to determine the tightness of the channel.

The differential pressure was measured on a standard pressure gauge. Within 24 hours, the pressure did not change. As a result of the experiment, it was found that the manometer readings after 10, 50 and 1440 minutes of testing remain at the same level equal to 40 atm, which confirms the insulating and viscoelastic adhesive properties of the repair composition.

Information sources

1. RU 2351629, 08/10/2007.

2. RU 2365613, 01/09/2008.

3. RU 2304160, 01.27.2006.

4. RU 2326922, 09.25.2006.

5. RU 2032068, 07.27.1992.

6. RU 2259469, 04/30/2004.

7. RU 2493189, December 16, 2011.

8. RU 2132448, 07.30.1997.

Claims (1)

Composition for repairing oil and gas wells, including a urethane prepolymer, a hydrocarbon solvent and a hardener, characterized in that it contains a hydrophobic urethane prepolymer as an urethane prepolymer, an oxidized vegetable oil as a hardener, an organic solvent soluble in acetone as a hydrocarbon solvent, or acetone, or a mixture thereof in the following ratio of components, wt.%:
Urethane hydrophobic prepolymer 3-30 Oxidized vegetable oil 5-50 Specified Organic Solvent rest
with an initial viscosity of the composition of not more than 200 cP and gel time in the range of 120-1500 minutes