RU2068080C1 - Compound for well killing - Google Patents

Abstract

FIELD: drilling and operation of wells, particular compounds for well killing, mainly, for killing the troubled wells. SUBSTANCE: compound for well killing contains polyacrylamide, salt of multivalent metal, lignosulfonate, wood flour of spruce species and water. Multivalent metal, preferably, is used in form of potassium or sodium bichromate. EFFECT: increased polymerization time of solution, its adhesion properties and provision of solution with yield stress of 2000-3500 dyne/sq cm. 2 cl, 1 tbl

Description

 The invention relates to the drilling and operation of wells, in particular, to compositions for killing wells, mainly emergency wells.

 Wells are considered emergency, to shut off which is not possible with traditional methods of jamming.

The traditional methods of killing wells include injecting aqueous solutions of NaCl, CaCl ₂ , bischofite, clay mud into the well, the density of these solutions being chosen such that when the full volume of the well is injected, the hydrostatic pressure of the liquid column is equal to or greater than the reservoir pressure. In this case, the injection of solutions into the well is carried out either for circulation (direct or reverse) or for absorption (forcing the formation fluid located in the wellbore into the channels of the producing formation).

 Another way of killing wells is to inject large volumes of industrial water into the well for absorption (in some cases, such wells will be connected to the reservoir pressure maintenance line (PPM) and then an aqueous salt solution or clay solution of the required density will be pumped to balance the known reservoir pressure.

 Known composition for killing wells, including polyacrylamide, hexoresorcin resin, formaldehyde and water (see source) prototype.

 A disadvantage of the known compositions is the inability to dissolve free gas in large volumes, evenly distribute it throughout the wellbore and reliably hold it in its volume, for example, during forced pressure fluctuations in the wellbore during circulation, i.e. prevent the release of gas plugs. In addition, in the known compositions, the polymerization process almost ends immediately when the components are mixed, i.e. before the composition enters the wellbore, as a result, the free gas in the composition will be in the form of plugs or rods, which violates the control of the technology for killing emergency wells. The formation of plugs or gas rods in the wellbore is also facilitated by the lack of adhesion of known compositions to the surface of casing pipes and tubing.

 In this regard, a number of specific requirements are imposed on the composition for killing emergency wells.

The aim of the invention is to create a composition that meets the following requirements: the polymerization time must be at least 8 hours, so that free gas has time to evenly distribute throughout the volume of the composition located in the well; temperature should not lead to a sharp increase in the rate of structure formation; after complete polymerization of the composition, its ultimate shear stress should be not less than 2000 dyne / cm ² in order to reliably hold gas bubbles in its composition, and not more than 3500 dyne / cm ² so that the composition does not lose mobility; the composition must have an adjustable density, because the lower the density, the more evenly distributed in the composition of the gas bubbles, the higher the density, the smaller the volume of the composition must be replaced by a solution that balances the reservoir pressure; the composition must have adhesion that prevents slipping of gas bubbles between the walls of the casing and the composition.

 This is achieved by the fact that the composition for killing wells, including polyacrylamide and water, additionally contains a multivalent metal salt, lignosulfonate and spruce wood flour, and the use of potassium dichromate or sodium dichromate as salts of the multivalent metal in the following ratio of components, wt. polyacrylamide 0.50-0.75; polyvalent metal salt 0.05-0.19; lignosulfonate 0.10-2.00; wood flour 3.00-10.00; water the rest.

 Characteristics of the components used.

 Polyacrylamide Domestic PAA are available in the form of a 6-8% gel (TU 6-01-1040-76) and dry powder (TU 6-16-157-78). Import brands: RDA-1020, RDA-1041, RDZ-1030, DK Drill A-1, DSK-ORP-F4-ONT, Accotrol S-622, etc.

Potassium or sodium dichromate (K ₂ Cr ₂ O ₇ or Na ₂ Cr ₂ O ₇ • 2H ₂ O) GOST 2651-78. The powder is orange in color, soluble in water, toxic.

 Lignosulfonate TU 81-04-225-79.

 Wood flour GOST 16361-79.

 To effectively shut down emergency wells, it is first necessary to evenly distribute free gas in the volume of the composition pumped into the wellbore and to reliably hold it in the composition with significant pressure fluctuations at various depths of the wellbore. This is achieved by the fact that the polymerization time of the composition is at least 8 hours. During this time, due to the Archimedean force, gas bubbles can rise from the bottom to the wellhead, and the structural and mechanical properties of the composition at the end of the polymerization process (ultimate shear stress) allow reliable gas retention in the composition after depressurization. In addition, in the initial stage of polymerization, the presence of wood flour in the composition ensures the free passage of gas bubbles under the influence of the Archimedean force and its better distribution in the entire volume of the composition. When the process of separation of resinous compounds from wood flour begins and a sharp crosslinking of the polymer chains occurs, the free gas will be evenly distributed throughout the entire proposed composition and will create a homogeneous system. Due to the presence of spruce wood flour in the proposed composition, it was possible to significantly reduce the consumption of polyacrylamide and to use sodium or potassium dichromate in minimal quantities. The adhesive properties of the composition prevent additional portions of fluid from flowing into the wellbore.

 The composition is prepared as follows. Sodium or potassium dichromate is dissolved in water, and then a powder mixture of polyacrylamide and lignosulfonate is introduced into the solution through the ejector in the required ratio. After the ejector, a solution of polyacrylamide, lignosulfonate and bichromate enters a container into which wood flour is added with constant mechanical stirring. After obtaining a homogeneous mass, the composition is pumped into the wellbore.

 To identify the advantages of the proposed composition in comparison with the known we define the properties in the following ratios of ingredients, wt.

 Composition 1. Polyacrylamide 0.50; potassium dichromate 0.05; lignosulfonate 0.10; wood flour 3.00; process water 96.35.

 Composition 2. Polyacrylamide 0.60; potassium dichromate 0.10; lignosulfonate 1.00; wood flour 5.00; process water 93.30.

 Composition 3. Polyacrylamide 0.75; potassium dichromate 0.19; lignosulfonate 2.00; wood flour 10.00; process water 87.06.

 Composition 4. According to the prototype.

 Compositions 1,2,3 correspond to the invention, composition 4 composition of the prototype.

The change in the structural and mechanical properties of the compositions over time was determined on a re-test at 20 and 60 ^o C.

 The adhesive properties of the composition were determined as follows. A metal tube 0.5 m high and 25 mm in diameter was filled with compounds and left for the duration of complete polymerization. Then pressure was created to squeeze the composition from the tube. Adhesion properties were determined by the straining pressure of the composition.

 The density of the composition was determined by a pycnometer.

 Data on the results of the test formulations are shown in the table.

 An example of the use of killing wells.

 At the well N 2151 (bush 11) of the Samotlor field of the Nizhnevartovskneft DAOOT for overhaul, it was jammed by the composition of the invention.

The well with an artificial bottom of 1884 m, a casing string of 168 mm, with 73 mm tubing pipes lowered into it to a depth of 1780 m and a funnel of 1780 m was operated by the gas-lift method. Perforation interval 1840-1844 (reservoir 3A-1), reservoir pressure 19.5 MPa. Before killing the well, it was gushing with gas, oil and water (the gas factor was more than 100 m ³ / m ³ ). An attempt to plug the well for 3 months with known formulations failed. Over 300 m ^{3 of an} aqueous NaCl solution with a density of 1,180 kg / m ³ and 12 m ^{3 of} known viscoelastic composition were consumed. The proposed composition of the well was plugged for 3 days. 300 kg of polyacrylamide, 500 kg of lignosulfonate were consumed. 60 kg of potassium dichromate and 1000 kg of wood flour. As a result, a major overhaul was successfully carried out in the well, and it is currently in operation. TTT1

Claims (1)

 1. The composition for killing wells, including polyacrylamide, and water, characterized in that it further comprises a multivalent metal salt, lignosulfonate and spruce wood flour in the following ratio, wt. Polyacrylamide 0.50 0.75
Polyvalent Metal Salt 0.05 0.19
Lignosulfonate 0.10 2.00
Spruce wood flour 3.00 10.00
Water Else
2. The composition according to p. 1, characterized in that as the salt of the multivalent metal, it contains potassium or sodium dichromate.

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