RU2738147C1 - Well inhibiting method from asphaltene-resin-paraffin deposits - Google Patents

Abstract

FIELD: oil, gas and coke-chemical industries.

SUBSTANCE: invention is intended for use in oil producing wells, operation of which is complicated by formation of asphaltene-resin-paraffin deposits - ARPD in a flow column and pump equipment. Prevention of formation of deposit under the invention is carried out by two-stage pumping into productive heterogeneous permeability oil reservoir technical liquids. At the first stage, a gel solution with a paraffin formation inhibitor is pumped into the formation. At the second stage, a gel converter is injected into the formation, having a higher viscosity than the gel solution and the ARPD inhibitor. Owing to high viscosity, the gel converter will mainly penetrate into the high-permeability zone of the formation and for a certain period of time it preserves the gel solution with the ARPD inhibitor in the interlayers. After the well is put into operation, an ARPD polymerisation inhibitor enters the production string from interlayers with low permeability, where the gel solution converter is not available due to its high viscosity. After definite and calculated time under action of pressure drop, gel converter loses its strength properties, breaks down and opens filtration channels for ARPD inhibitor introduction into well from highly permeable interlayers.

EFFECT: technical result is higher efficiency of method due to uniform and longer supply of reagent to well, prevention of paraffin formation in column of lifting pipes and bottom-hole pump.

1 cl, 1 dwg

Description

The invention is intended for use in the oil industry, aimed at increasing the period of trouble-free and efficient operation of downhole pumping equipment for oil wells, the operation of which is complicated by the presence of asphalt-resin-paraffin deposits in the tubing string and in the deep pump.

To prevent wax formation in the wells, inhibitors of a certain purpose are supplied to the pump intake. There are several ways to inhibit wells, most of which are carried out by supplying a liquid ARPD inhibitor to the pump intake along the annular space (MP) of the well.

There is a known method of supplying the inhibitor to the pump intake by pumping it in the form of a solution into the MP and organizing the circular circulation of a part of the produced fluid from the tubing string (tubing) into the annular space of the well (p. 250 source: Ibragimov G.Z., N.I. Khisamutdinov, Handbook on the use of chemical reagents in oil production, Moscow: Nedra, 1983, 312 p.). The method requires periodic involvement of the enterprise personnel to change the well operation mode.

The method of supplying the reagent through a special capillary tube fixed outside the tubing string is widely used in the oil industry (RF patents for inventions No. 2260677 (published on 20.09.2005) and 2302513 (published on 10.07.2007). This technology requires preliminary arrangement of the tubing string with a capillary tube.

The closest to the claimed invention in terms of the technical solution to the problem of optimizing the use of paraffin inhibitors in complicated wells is the method of injecting a reagent into the bottomhole formation zone (BHZ), presented in the thesis by K.Sh. Khaibullina. "Justification of an integrated technology for the removal and prevention of organic deposits in wells at a late stage of oil field development." - SPb .: Mining University, 2018 (pp. 75-76 thesis). According to this thesis, an inhibitor in the required amount is injected into the oil reservoir in the form of a 15-20% solution in oil and then moves into the distant zones of the reservoir with a displacement fluid in a volume 5-10 times greater than the volume of the inhibitor solution. According to the source: Ibragimov G.Z., N.I. Khisamutdinov. A reference manual for the use of chemicals in oil production. - M .: Nedra, 1983 .-- 312 p. - on page 254 it is indicated that the volume of the displacement fluid exceeds the volume of the inhibitor solution by 5-30 times and can reach 100 m ³ .

The well is closed for a period of up to 24 hours to ensure that the formation is saturated with an inhibitor (adsorption process) and then put into operation as usual. In the process of fluid filtration through the bottomhole formation zone, a long-term desorption process occurs, the inhibitor is released and enters the well with the formation fluid, reducing or completely preventing the formation of ARPD. The method requires the organization of supplying a significant amount of displacement fluid into the well, which increases the cost of ensuring the well operation in a trouble-free mode. The second disadvantage of this method is the uneven removal of the inhibitor from the oil reservoir. This is due to the intensive desorption of the reagent on the first day of the process, primarily from highly permeable interlayers of the formation, in which the greatest movement of the formation fluid towards the wellbore is observed.

The technical objective of the claimed invention is to develop a method for pumping an ARPD inhibitor into an oil reservoir, the implementation of which is not associated with the injection into the reservoir of a significant volume of backing fluid. The method should ensure uniform removal of the inhibitor from the oil reservoir over a long period of time and protect the underground equipment from wax formation.

The task is accomplished by the fact that according to the method of inhibiting the well from asphalt-resin-paraffin deposits, which consists in pumping an ARPD inhibitor solution under pressure into the bottomhole formation zone (BHZ), keeping the well idle for adsorption of the inhibitor in the formation and putting the well into operation, for an oil formation with By heterogeneity in permeability, the inhibitor is preliminarily mixed with an aqueous solution of a gel, for example, polyacrylamide, this composition is injected into the oil reservoir, after which a gel transformer (polymer coagulant) is injected into the reservoir, which, in contact with the gel under reservoir conditions, increases its strength and adhesive properties relative to the rock surface formation, and the gel transformer must have a higher viscosity than the solution of the gel and the ARPO inhibitor. Subsequent production of fluids from the formation is carried out with drawdown, in which the destruction and removal of the gel with the inhibitor from the high-permeability layers of the oil formation will occur gradually and for the required time.

Let us consider the implementation of the proposed method on the example of a hypothetical formation with two layers of the same thickness, the permeability of which differs by two times (let the conditional first layer be more permeable than the second). Under the action of the same pressure drop for both interlayers, according to the Dupuis formula, the first layer will receive a gel solution with an inhibitor twice as much by volume as into the second low-permeability layer. The supply of a gel with a higher viscosity to the formation of the transducer will lead to the fact that its main mass will penetrate into the first formation with high permeability and plug it for a certain estimated time. Practically no gel transformer will enter the second layer due to its low permeability.

After 12-24 hours, the well is put into operation. Under the influence of the depression from the second low-permeability interlayer, formation products with an ARPD inhibitor will flow due to its desorption from the rock surface. By the end of the reagent desorption process, the high-strength gel in the first interlayer will begin to lose its properties and gradually degrade, opening filtration channels for the movement of the gel with the ARPD inhibitor and formation products. The process of destruction of the gel is a long and gradual process, due to which all new filtration channels will be opened, along which new portions of formation products with an inhibitor of asphalt-resin-paraffin deposits will move towards the well.

According to the invention, it is proposed to conserve the bulk of the inhibitor in the form of a gel solution in highly permeable interlayers of the formation. For many fields, interlayers with high permeability are flooded in the first place, therefore the proposed technology will contribute to obtaining an additional effect in the form of a decrease in the proportion of water in the produced formation product.

According to the information given on page 179 of the article of the authors: E.N. Baykova, R.Kh. Muslimov. Experience in the application of technologies for limiting water inflow and repair and insulation works in fractured carbonate reservoirs (journal Georesursy. - 2016. - V. 18. - No. 3. - Part 1. - P. 175-185) Table 5 shows the period of the positive effect of repair - isolation works at 6 wells of OJSC “Belkamneft”. To isolate high-watered interlayers, the polymer "REACOM" was used, the duration of the effect for the wells was from 8 to 17 months with an average value of 13.8 months.

FIG. 1 shows the position in the oil reservoir after the injection of the ARPD inhibitor into the bottomhole formation zone according to the claimed invention. Positions indicate: 1 - well casing, 2 - deep pump, 3 - oil reservoir with two isolated interlayers, 4 - first reservoir with higher permeability, 5 - second reservoir with lower permeability, 6 - impermeable interlayer, 7 - gel solution with inhibitor ASPO, 8 - gel transformer (gel hardening zone).

According to the above scheme, after pumping the inhibitor into the well, a downhole pump is lowered on the tubing string and a bottomhole pressure is created that is less than the formation pressure. As a result of this depression from the second - lower one in FIG. 1 interlayer for a certain time, the ARPD inhibitor will enter the well, and without a period of salvo concentration of the reagent in the formation fluid flow carried out into the well. By the end of this time, zone 8 with a gel transformer under the influence of a constantly existing pressure drop will begin to slowly collapse and pass formation fluid together with an ARPD inhibitor into the wellbore zone from zone 7 of the first - upper layer. The period of inhibition of the well space will be extended due to the uniform and extended in time process of the removal of the reagent from the more permeable and previously plugged interlayer.

According to the invention, it is proposed to produce oil after injection of the reagent at such a depression (the difference between the formation and bottomhole pressures in the wellbore), which will ensure the onset of slow destruction of the gel hardening zone. Since almost all oil fields have individual parameters in terms of geological structure, filtration characteristics of interlayers and fluids saturating them, the magnitude of such a depression for each productive oil reservoir is preliminarily determined in laboratory conditions by modeling filtration processes in core samples.

According to the authors, a significant difference and novelty according to the claimed invention is that previously most of the inhibitor injected into the oil reservoir is protected from consumption. Only with the passage of time of destruction of the hardening zone of the gel 8 is the dosage of this most of the inhibitor into the well. Thus, according to the invention, the dosage of the inhibitor is carried out not only due to the known phenomenon of desorption of the reagent from the surface of the formation rocks, but also from the volume of the gel solution injected into the highly permeable formation.

According to the invention, a technical positive result is achieved - there is no need to inject the reagent into remote areas of the bottomhole formation zone to increase the surface area of the rocks for the course of adsorption processes. When pumping equipment is put into operation, peak flow rates and irrational intake of inhibitor into the well will be eliminated.

Claims (1)

A method of inhibiting a well from asphalt-resin-paraffin deposits, which consists in injecting an inhibitor of asphalt-resin-paraffin deposits - ARPD into the well bottom-hole zone of a productive oil formation, keeping the well idle for adsorption of the inhibitor in the formation and putting the well into operation, which is characterized by the fact that for the reservoir heterogeneity the inhibitor is mixed with an aqueous solution of the gel, this composition is injected into the oil reservoir, after which a gel transformer is injected into the reservoir, which, when it contacts the gel in reservoir conditions, increase its strength and adhesion properties relative to the surface of the formation rock, and the gel transformer has a higher viscosity than the gel solution and the ARPD inhibitor, and the subsequent production of fluids from the formation is carried out during drawdown, in which the destruction and removal of the gel with the inhibitor from the high-permeability interlayers of the oil formation occurs gradually and for the required time.

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