RU2084622C1 - Method for treatment of well bottom-hole zone - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: method can be used in levelling permeability of interlayers in producing wells. Selected in producing reservoir zone is interval to be treated with water encroachment of product not over 60%. Interval to be treated is isolated from above- and below-lying intervals. Injected into interval to be treated are return oil emulsion and additionally initial portion of water, water solution of acid under pressure below injection pressure of return oil emulsion and second portion of water, then technological pause is made. Operations of injection and technological pause are repeated at increasing pressure of injecting water solution of acid up to pressure of injecting return oil emulsion. Then connected are treated zone of reservoir, above- and below-lying intervals. EFFECT: high efficiency.

Description

 The invention relates to the oil industry and may find application in leveling the permeability of interlayers in production wells.

A known method of processing the bottom-hole zone of the well, comprising injecting acid into the formation [1]
The known method leads to an increase in the permeability of the bottomhole zone, however, it does not allow to equalize the permeability of the low permeability and high permeability zones, and therefore does not lead to an increase in oil production from low permeability zones.

Closest to the invention in technical essence is a method of processing bottom-hole zone of an oil reservoir, including the injection into the reservoir of a hydrophobic emulsion and an acid solution [2]
The known method contributes to the alignment of permeabilities, however, its effectiveness is low.

 The aim of the invention is to increase oil production due to the alignment of the permeability of the interlayers of the reservoir.

 This goal is achieved by the fact that in the method for processing the bottom-hole zone of a well, which includes injecting a reverse oil emulsion and an aqueous solution of acid into the formation, according to the invention, a process interval with a water cut of produced products of not more than 60% is isolated from the above- and the underlying intervals, the reverse oil emulsion and, optionally, a portion of water are pumped into the treated interval, while the aqueous acid solution is pumped at a pressure of less m of injection pressure of the reverse oil emulsion, then a second portion of water is pumped, technological exposure is carried out, the cycles of injection of the reverse oil emulsion, portions of water and an aqueous solution of acid are repeated with technological exposure being carried out with increasing the injection pressure of the aqueous acid solution to the injection pressure of the reverse oil emulsion and the processed interval with higher and lower intervals.

 When developing a multilayer oil reservoir in a well, productive formations are disconnected, for example, by setting packers above and below one of the productive formations, setting cement bridges, etc. At the same time, the tubing string with holes is installed in the selected area and through them the inverse oil emulsion, water and an aqueous acid solution are pumped into the processed interval.

The calculation of the required amount of injection of the inverse oil emulsion is performed according to the formula
V = π • R ² • h • m • K • K _{draw oh} (1)
where V is the estimated volume of injection, m ³
R is the radius of depression (repression), m
h interval of the reservoir to be treated, m
m porosity
_{Kot extrusion} coefficient
K _oh coverage ratio.

 For injection into the processed interval, it is desirable to use the volume of the inverse oil emulsion slightly more than the calculated one (up to 5-10%). During the subsequent injection of water, the last portions of the oil emulsion are mixed with water, while the viscosity of the mixture becomes lower than the viscosity of the inverse oil emulsion. The mixture of low viscosity enters not only in the highly permeable interval, but also in the less permeable, creating temporary insulation there. The aqueous acid solution injected after this enters the low-permeability interval of the formation, reacts with the formation rock and clogging compounds, and increases permeability. The decrease in the injection pressure of the aqueous acid solution below the injection pressure of the reverse oil emulsion helps to maintain the position of the reverse oil emulsion in the formation and the entry of the aqueous acid solution into the low permeability layers. The water injected after this helps to flush, dilute the last parts of the acid and promote the diluted acid into the least permeable areas of the formation.

 Gradually, with an increase in the number of cycles, the injection pressure of the aqueous acid solution is increased, bringing it to the injection pressure of the reverse oil emulsion. This ensures equality of treatment conditions for high permeability and low permeability layers.

 After the technological exposure required after each cycle for the reaction of the acid with the formation rock and the clogging elements, the processed interval is reported with the higher and lower intervals, the well is washed and put into operation.

 If necessary, they switch to another interval and carry out processing operations on it.

 As a result of the treatment, the reverse oil emulsion is clogged with a high permeability interlayer and the acid penetrates into the low permeable interlayer. Moreover, since the inverse oil emulsion is inert with respect to the formation rock and is displaced from the treated layer during the development of the reservoir, there is no change in the permeability of the highly permeable layer. When acid is injected, it penetrates into the low-permeability zone (the high-permeability is temporarily filled with reverse oil emulsion). Acid, reacting with the rock of the reservoir and the clogging elements, increases the permeability of the low-permeability zone. As a result of these processes, the overall permeability of the treated interval increases and levels out. The method is particularly effective in the treatment of formations with a water cut of not more than 60%. With a water cut of more than 60%, the effect is reduced.

The volume of the injected first portion of water is prescribed 10-15% of the volume of injection of the reverse oil emulsion. The volume of injection of an aqueous acid solution is prescribed based on the calculation of 1 m of solution per 1 m ^{3 of} treatment of a low permeability layer. Usually requires 2-4 m ³ solution. As an aqueous acid solution, a 12-15% aqueous hydrochloric acid solution is used. It is possible to use a mixture with hydrofluoric acid. The injection volume of the second portion of water is prescribed 15-20% of the injection volume of an aqueous acid solution. The injection pressure of the reverse oil emulsion and the first portion of water is determined based on the injectivity of the well. The injection pressure of the aqueous acid solution is prescribed in the first injection cycle to 30-50% of the injection pressure of the reverse oil emulsion. The injection pressure of the second portion of water may range from the injection pressure of the aqueous acid solution to the injection pressure of the reverse oil emulsion.

 Technological exposure is carried out for the time necessary for the reaction of the acid with the material of the collector, for example carbonate, and colmatizing elements. It can be 1-4 hours.

Обратную нефтяную эмульсию готовят смешением товарной нефти, эмульгатора и пластовой воды в соотношении, мас. 50; 1,5; 48,5 соответственно.Example. In an oil well 1230 m deep, the quantity and depth of oil-containing formations and their water cut are determined. It is determined that at the depths of 1220-1214 and 1210-1205 m oil-containing formations with a water cut of produced products up to 60% are placed. The permeability of the formations varies from 350 mD in the range of 1-2 m to 2 mD in the interval of 1 m. A tubing string is lowered into the well. pipes with perforation at depths of 1220-1214 m. Packers are placed at depths of 1221 and 1213 m. Calculate the injection volume of the inverse oil emulsion according to the formula (1):

Reverse oil emulsion is prepared by mixing commercial oil, emulsifier and produced water in the ratio, wt. fifty; 1.5; 48.5 respectively.

8 m ^{3 of} inverse oil emulsion, 0.8-1.0 m ^{3 of} water, 6 m ^{3 of a} 12% aqueous hydrochloric acid solution, 3 m ^{3 of} water are pumped into the bottomhole zone. The inverse oil emulsion and water are injected at a pressure of 10 MPa at the mouth, and the aqueous acid solution is injected at a pressure of 6-10 MPa. Spend technological exposure for 2 hours

 The cycles of injection and technological aging are repeated, however, in the second cycle, the injection pressure of the aqueous acid solution is set to 6 MPa, in the third 8 MPa, in the fourth 10 MPa.

 After the fourth cycle, the packers are removed, the well is washed with water and the bottom-hole zone is treated in the next interval of 1210-1205 m.

Launch the well into operation. After treatment, the flow rate of the well increased from 20 to 38 m ³ / day, and the water cut of oil decreased from 58 to 40%. The application of the proposed method will increase oil production while reducing the water cut of the produced products.

Claims (1)

 A method of treating a bottomhole zone of a well, including injecting a reverse oil emulsion and an aqueous solution of acid into the formation, characterized in that in the interval of the producing formation, a treatment interval is allocated with a water cut of produced products of not more than 60%; the treatment interval of the formation is isolated from the higher and lower intervals into the processable the interval is injected with a reverse oil emulsion and an additional portion of water, while an aqueous acid solution is pumped at a pressure lower than the injection pressure of the reverse oil emulsion ii, then they pump a second portion of water, carry out technological exposure, repeat the cycles of injecting the reverse oil emulsion, the portions of water and the aqueous acid solution with technological aging while increasing the injection pressure of the aqueous acid solution to the injection pressure of the reverse oil emulsion and report the treatment interval from above to and underlying intervals.