RU2547850C2 - Large-volume selective acid treatment (lvsat) for producers in carbonate reservoirs - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to the technology intended for well productivity improvement. Large-volume selective acid treatment (LVSAT) for producers in carbonate reservoirs includes the injection to the well of an acid composite band with the specific volume of 1.5-3m³ per 1 m of an oil-saturated interval and non-linear viscous deflecting fluid before and/or upon the injection of the acid composite band, at that the injection of the acid composite is carried out with an optimal flow rate and an optimal ratio of a deflecting fluid volume to the acid composite volume, which are defined by mathematic modelling of the process considering changes in the wellhead and bottomhole pressure, type of the acid composite, type of the deflecting fluid, porosity and permeability of rock; at that for the purpose of the optimal flow rate optimisation for the acid composite injection dependencies of the optimal flow rate of injection on the specific volume of reagents injection are obtained with different constants of the reaction.

EFFECT: improved efficiency of large-volume selective acid treatment (LVSAT) for carbonate reservoirs.

2 cl, 5 tbl, 1 ex, 11 dwg

Description

The method of large-volume selective acid treatment (BSKO) of production wells in carbonate reservoirs

The invention relates to a technology for increasing well productivity, which provides for selective treatment of heterogeneous permeability of the formation with an acid composition in order to dissolve the carbonate components of the formation to restore or increase the permeability of the bottomhole formation zone.

Acid treatments of carbonate reservoirs are the most common method of chemical exposure to the bottom-hole zone of wells to enhance oil production. Today, there are various technologies for carrying out acid treatments from acid baths with a “zero” processing speed to critical speeds with excess fracture pressure and the formation of acid fracturing. (A reference guide for the design of the development and operation of oil fields. Oil production. Edited by Sh.K. Gimatudinov. M .: Nedra. 1983; Economides MJ, Nolte KG Reservoir Stimulation 3-rd Edition, John Willey & Sons, LTD, New York. - 2000.).

Low-volume hydrochloric acid treatments (RMS) are designed to restore well productivity and overcome shallow (less than 0.5 meters) damage to the bottom-hole formation zone by dissolving carbonate rock. In this case, the intensification of well productivity is insignificant, which is associated with a small depth of impact.

Bottom-hole bulk treatment (BHP) is a technology for increasing well productivity, which involves treating the formation with an acid composition in a volume of more than 1.5 m ³ per 1 m of oil-saturated interval in order to dissolve the carbonate components of the formation to restore or increase the permeability of the bottom-hole formation zone. Unlike large-volume selective acid treatment (BSCO), BOPZ does not provide for selective exposure, i.e. the use of flow rejection technologies.

A known method of acidizing carbonate reservoirs (Paccaloni, G., and Tambini, M .: ″ Advances in Matrix Stimulation Technology, ″ JPT43 (3) (1993) 256-263.) Using a maximum pressure gradient and injection rate (MAPDIR) for direction acid composition in low permeability zones. This technology involves the injection of treatment fluid with the highest possible flow rate with a pressure below the hydraulic fracturing pressure - hydraulic fracturing. The results show that

MAPDIR technology allows you to quickly lower the total skin during the acid treatment of the bottomhole formation zone by injecting large volumes of acid into the more permeable formation. The method is effective for processing short, uniform permeability intervals of the formation, which are extremely rare.

The known method is not effective enough for the following reasons: the method does not allow to process the low permeability layer completely. For successful acid treatment, the optimal placement of the reactive liquid — the acid composition and increase in the coverage area — is essential. This is especially important for long intervals with a high degree of heterogeneity in permeability. Without effective deflection, injected fluids will follow the path of least resistance and will only affect areas with the highest permeability. Targeted delivery of the working fluid to low-permeability sections of the reservoir is required. In practice, the acid composition and diverting fluids are pumped into the formation alternately.

Closest to the claimed one is a method of large-volume selective acid treatment (RF patent No. 2456444, publ. 02/10/2012), which includes injecting the rims of the acid composition at a certain flow rate into the well, pumping a nonlinearly viscous deflecting diverting fluid before and / or after the rim of the acid composition , the acid composition is pumped with a specific volume of 1.5-3 m ³ per 1 m of oil-saturated interval. The known method is not effective enough for carbonate reservoirs; it does not optimize the cost of injecting the acid composition and diverter.

The object of the invention and the expected technical result are to increase the efficiency of large-volume selective acid treatment (BSCF) of carbonate reservoirs by determining the optimal injection rate of the acid composition for each stage of processing, the optimal ratio of the volume of the deflector to the volume of the acid composition used in each subsequent stage. When choosing the direction of technological optimization: the maximum increase in the productivity of the well, the maximum increase in the productivity of the target interlayers or the minimization of dispersion (the maximum alignment of the inflow profile into the well), the volume of each subsequent reagent rim at the optimum injection rate is determined.

Based on the developed mathematical model of the process of acid dissolution of layered inhomogeneous carbonate reservoirs using deflecting nonlinearly viscous fluids, the optimal values of the parameters that influence the improvement are determined during the computational experiment

reservoir properties of the reservoir, to ensure maximum efficiency of acid treatments of carbonate reservoirs. The fundamental difference between the proposed technical solution and the known ones is the design of the acid treatment of heterogeneous reservoirs as a result of mathematical modeling of the acid treatment of carbonate reservoirs.

The problem is solved in that in the method of large-volume selective acid treatment (BSCF) of production wells in carbonate reservoirs, which includes injecting into the well rims of acid composition with a specific volume of 1.5-3 m ³ per 1 m of oil-saturated interval and a nonlinearly viscous deflecting liquid - the deflector before and / or after the rim of the acid composition, according to the invention, the injection of the acid composition is carried out with an optimal flow rate and an optimal ratio of the volume of the deflector to the volume of the acid composition, which are determined mathematical modeling of the process taking into account changes in wellhead and bottomhole pressure, type of acid composition, type of diverter, porosity and permeability of the rock, and to optimize the injection rate of the acid composition, the dependences of the optimal injection rate on the specific volume of injection of reagents with different reaction constants are obtained in order to minimize the error of calculating the optimal flow rate of injection of the acid composition, the volume of each subsequent rim is determined according to the ratio

- общий объем кислотного состава, $$V_{\min }^{KC}$$

- объем первой пачки, n -число стадий,Where $$V_{\max }^{KC}$$

- total volume of acid composition, $$V_{\min }^{KC}$$

- the volume of the first pack, n is the number of stages,

to determine the optimal ratio of the volume of the deflector to the volume of acid use the criterion

where S _d , S _{d max} - pseudo-skins of the diverter and its maximum value, respectively, D, D _max - the dispersion of the flow rate across the interlayers and its maximum value, respectively,

для каждой i-ой стадии определяется соотношениемthe volume of the deflector is determined depending on the heterogeneity of the medium and taking into account the specified specific volume of the acid composition, while the optimal volume of the deflector $$V_i^{div}$$

for each i-th stage is determined by the relation

and the optimal amount of acid providing the greatest economic effect is determined by the calculated dependence of the return on investment ratio on the volume of the acid composition. In addition, the acid composition is pumped in several rims, and the diverter is pumped before, and / or after, and / or between the rims of the acid composition.

Здесь p - давление, v - скорость течения; k - проницаемость, µ - вязкость жидкости.The problem of large-volume hydrochloric acid treatment (BSCO) of carbonate formations is considered in the framework of multicomponent isothermal filtration of a single-phase incompressible fluid. Integral reagent distributions and mass balance as a result of a chemical reaction are predicted by a simplified axisymmetric approach. Diffusion processes in the formation develop over a significantly longer time than the time of injection of reagent solutions into the formation, therefore, the contribution of diffusion processes in modeling the treatment of the bottom-hole zone of wells is neglected. In the case of an averaged description of the filtration processes in the near-wellbore zone of the wells, the movement of fluid through a system of a sufficiently large ensemble of highly permeable channels formed is subsequently considered to obey Darcy

Here p is the pressure, v is the flow velocity; k - permeability, µ - fluid viscosity.

, где V₀ - объем закачиваемой оторочки, Q - расход закачиваемой кислоты, К - константа реакции. Число Дамкелера Da изменяется в зависимости от расхода Q. Эффективность процесса БСКО определяется как отношение дебитов жидкости после воздействия к дебиту жидкости до воздействия, и является безразмерной величиной, которая показывает кратность увеличения дебита жидкости.The model of hydrochloric acid treatment is generalized to the case of a layered heterogeneous formation. Selective acid treatment is simulated using non-linearly viscous deflectors within the framework of a piston model taking into account the basic physicochemical processes occurring in a porous medium. In FIG. Figure 1 shows the calculated dependence of the effectiveness of the effect of hydrochloric acid treatment Q _rel on the dimensionless similarity criterion for the Damkeler number $$Da\frac{K{V}_0}{Q}$$

where V ₀ is the volume of the injected rim, Q is the flow rate of the injected acid, and K is the reaction constant. The Damkeler number Da varies depending on the flow rate Q. The efficiency of the BSKO process is defined as the ratio of the fluid flow rate after exposure to the fluid flow rate before exposure, and is a dimensionless quantity that shows the multiplicity of increase in fluid flow rate.

Multivariate numerical calculations of the task showed that there is an optimal mode of reagent injection into the reservoir, which allows to achieve maximum process efficiency (maximum growth rate), determined by the extremum of this function.

A distinctive feature of mathematical modeling is

the possibility of technological and economic optimization of the design of the BSKO.

Technological design optimization of BSKO includes several stages:

- determination of the optimal injection rate for each acid stage;

- calculation of the optimal volume of the diverter relative to the volume of the acid composition;

- the distribution of the stages of the BSKO relative to the total volume of the acid composition.

Technical and economic optimization is aimed at achieving the following results from acid treatment:

a) Maximum well productivity. When choosing this direction, the optimization goal will be to maximize the productivity of the well or minimize the skin factor of the well, which serves as a criterion for the effectiveness of BSKO. Priority for intensification will be the most conducted interlayers.

The uniformity of the processing of the entire interval does not matter, therefore, the optimization of the diverter volumes will not be available.

b) Maximum intensification of target interlayers. In this case, the optimization will be aimed at maximizing the productivity of the selected group of interlayers. As an optimization criterion, the overall minimization of the skin factors of the selected interlayers is selected.

c) Minimization of variance. Moreover, the goal of optimization is to maximize the alignment of the inflow profile into the well, which is characterized by minimizing the coefficient of mean-square dispersion.

The whole optimization process is divided into stages that correspond to the selected areas. When these steps are performed, the optimal ratios between the volumes of the acid stages and the diverter stages are calculated.

The optimal injection costs of each stage are determined, as well as the most cost-effective volumes. The sequence of stages is fixed, but one or more stages may be excluded from the general sequence. Acid composition injection rate optimization

According to the results of laboratory experiments (Fredd CN, Fogler HS Optimum Conditions for Wormhole Formation in Carbonate Porous Media: Influence of Transport and Reaction // SPE Journal. - September 1999. - V.4. - No. 3. - P. 196-205) by filtering in cores it is known that there is an optimal regime in which acid intensification proceeds most efficiently. This mode corresponds to

the optimal Damkeler number, defined as the ratio of the rate of a chemical reaction to the rate of convective transfer. With optimal values of the Damkeler number, the longest and most numerous dissolution channels (wormholes) are formed, penetrating deep into the reservoir and providing the best hydrodynamic connection between the reservoir and the well. When filtering the acid composition from the well into the formation, with radial flow geometry, in order to optimize the intensification process, it is necessary to ensure the optimal value of the Damkeler number at the front of the formation of dissolution channels. During a computational experiment in the mathematical modeling of BSKO on a simulator, the dependences of the optimal injection rate on the specific injection volume for reagents with different reaction rate constant K were obtained. FIG. Figure 2 shows the change in the optimal acid injection rate depending on the specific volume of acid injection for various types of acid compositions. The data were calculated for various values of the relative change in the reaction constant K with respect to the reaction constant K ₀ for ordinary 12% HCl. The value of K / K ₀ characterizing the type of acid composition varies from K / K ₀ = 0.5 (the lower line with the smallest angular coefficient) to the highest K / K ₀ = 3 value, passing intermediate K / K ₀ = 1; K / K ₀ = 1.5; K / K ₀ = 2.

The calculations showed that the optimal acid injection rate increases with increasing specific acid injection volume. This dependence is described by a linear function. With an increase in the reaction rate constant K, the angular coefficient of the linear function also increases. The straight line is getting steeper. The calculation results are consistent with experimental data (Fredd S.K., Fogler HS Optimum Conditions for Wormhole Formation in Carbonate Porous Media: Influence of Transport and Reaction // SPE Journal. - September 1999. - V. 4. - No. 3. - P. 196-205).

Because the acid treatment process is a sequential injection with a fixed flow rate of the rims of the process fluids; the average optimal flow rate for each acid stage can be calculated. In this case, from stage to stage, the optimal injection rate should increase. In FIG. Figure 3 shows the dependence of the skin factor on the flow rate of acid injection for three successive stages. As can be seen from the figure, for each stage of acid treatment there is an optimal mode in which the skin factor of the well after treatment is minimal (optimum). For each subsequent stage, the skin factor decreases. The dashed line in FIG. Figure 3 shows the trend of decreasing the minimum value of the skin factor of the well in each stage after the conducted BSKO.

It follows from Darcy's law that the optimal skin factor corresponds to the optimal value of the injection flow rate, which increases with decreasing skin factor.

During the computational experiment, an algorithm is implemented to optimize the injection rate of the acid composition to minimize the skin factor in the well in order to obtain the maximum oil increase in the target interlayer.

Optimization of the ratio of volume stages of acid

Using mathematical modeling, the dependences of the optimal acid injection rates for different reaction rates, which are linear functions of the specific injection volume, are obtained. In order to minimize the error in calculating the optimal injection rate of the acid composition, it is advisable to determine the volumes of acid injected at each stage, so that their injection time is the same. From this assumption, it follows that, knowing the volume of the first minimum acid stage, it is possible to determine the volume of each subsequent stage according to the ratio

- общий объем кислотного состава, $$V{}_{\min }{}^{KC}$$

- объем первой пачки, n - число стадий. Данное допущение также ведет к упрощению технологических операций при проведении обработки. На фиг. 4 показана гистограмма распределения объемов закачки кислоты по стадиям. Стадия - часть процесса проведения БСКО, в рамках которого непрерывным образом закачивается определенный тип жидкости в определенном объеме и с определенным расходом.Where $$V_{\max }^{KC}$$

- total volume of acid composition, $$V{}_{\min }{}^{KC}$$

is the volume of the first packet, n is the number of stages. This assumption also leads to the simplification of technological operations during processing. In FIG. 4 shows a histogram of the distribution of acid injection volumes by stages. Stage - part of the process of conducting BSKO, in which a certain type of liquid is pumped continuously in a certain volume and at a certain flow rate.

When the total volume of acid changes, the fluid injection plan is automatically recalculated. BSKO working fluids - all fluids used during BSKO: pre-points, acids and deflecting compounds. Pre-spot - the fluid injected into the formation immediately before the acid composition may be a solvent.

From the calculations it is seen that the volumes of acid (dark staining) and diverter (light staining) in the first stage, respectively, 2.4 m ³ and 3 m ³ . For the second stage, the volumes of acid and deflector increase, respectively, to values of 4 m ³ and 5 m ³ in accordance with formula (1). In the third stage, the volume of acid is already 9 m ³ .

Optimization of the ratio of deflector volume to acid volume for each

stage

An analysis of the results of the BSKO measures confirms the fact that an unreasonable increase in the volume of rejects reduces the effectiveness of the treatments.

When injecting the diverting fluid into a heterogeneous formation, two processes occur. The first is the alignment of the injectivity profile (it can be numerically characterized by the coefficient of quadratic dispersion). The second is a decrease in overall throttle response. With an increase in the deflector volume, the dispersion decreases, and the injectivity worsens, i.e. the pseudo-skin of the diverter grows. A criterion is proposed to determine the ″ optimal ″ ratio — deflector volume / acid volume

where S _d , S _{d max} - pseudo-skins of the deflector and its maximum value, respectively, D, D _max - the dispersion of the flow rate across the interlayers and its maximum value, respectively.

The value of the dispersion coefficient characterizes the degree of deviation of the productivity profile from the average value. The optimal from the point of view of development is a uniform effect on the productive interval, in this idealized case D = 0. High values of the dispersion coefficient indicate uneven development of reserves or uneven coverage of the reservoir by water flooding. The rationale for this criterion is that the maximum possible alignment of the injectivity profile with a viscous diverter increases the connectivity of low-permeability layers of the formation with the well during acid treatment. In FIG. 5 shows the dependence of the coefficient α calculated by the formula (2) on the ratio of the deflector volume V ^div to the acid composition volume V ^KC . This dependence has a nonmonotonic character. The optimal ratio of the volume of the deflector relative to the volume of the acid composition is determined by the value of α _max .

для каждой i-ой стадии определяется соотношениемOptimum deflector volume $$V_i^{div}$$

for each i-th stage is determined by the relation

As a result of numerical simulation of the BSKO procedure on an inhomogeneous formation consisting of two hydrodynamically unconnected interlayers with a conductivity ratio of k ₁ h ₁ / k ₂ h ₂ = 10, the dependence of the efficiency of selective processing of low permeability reservoirs on the ratio of the deflector volume V ^div to

the volume of acid V ^KC shown in FIG. 6. The efficiency of selective treatment is calculated as the ratio of the consumption of acid trapped in the low permeability layer to the total consumption of acid trapped in both layers: η = Q ₂ / (Q ₁ + Q ₂ ), where index 2 refers to the low permeability layer. The calculations were performed for various types of deflectors: a linear gel with a concentration of 4 g / l (guar gel), a crosslinked gel with a concentration of 1.8 and 3.6 g / l (guar gel with a reverse crosslinker).

The calculations showed that the greatest efficiency is achieved when using a crosslinked gel with a concentration of 3.6 g / l, curve 3. Almost the entire volume of the acid solution falls into the low permeability layer. Curve 2 corresponds to a crosslinked gel with a concentration of 1.8 g / L. The least efficiency of a linear gel with a concentration of 4 g / l, curve 1. As can be seen from the graphs in FIG. 6, the growth of the deflection efficiency slows with an increase in the deflector volume. This connection has a character close to the logarithmic law. For such processes, the derivative of the objective function with respect to the argument is usually analyzed as an indicator of the efficiency of the process.

The volume at which the efficiency of the selective treatment of low-permeability reservoirs begins to increase slightly is selected as the effective volume of the rim of the acid composition. In this case, the volume is selected in which the derivative of the efficiency with respect to the specific volume of the rim of the acid composition becomes less than 0.001 m ^-3 .

In the course of mathematical modeling of BSKO, the dependence of the derivative on the efficiency with respect to the specific volume of the rim of the acid composition (CS) was obtained, FIG. 7. The effective value of the specific volume of the acid composition thus established is a range of more than 1.5 m ³ per 1 m, but not more than 3 m ³ per 1 m of the oil-saturated interval. The optimal value of the volume of acid composition is determined during the economic optimization of the design of the BSKO in the process of mathematical modeling of the BSKO.

Economic optimization of design of BSKO

To determine the optimal design, it is advisable to use the criteria of economic efficiency. In the simulator, the evaluation of the cost-effectiveness of the BSKO is carried out for a given volume of acid. For the main economic parameter, on the basis of which the optimal acid volume for the well is selected, the return on investment ratio (ROI), which is defined as

where ROI is the return on investment ratio, P _net is the net profit after taxes, and _KOs are the total costs associated with conducting a BSCO.

This approach allows you to immediately eliminate economically unviable projects, significantly reduce the number of input data and simplify calculations, because in this case it is only necessary to consider conditionally variable costs (costs that depend only on production). To determine the ROI, it is necessary to forecast changes in the increase in oil production over the period of the effect of the event. The forecast in the model is made using trends based on statistical data on the field using analytical functions. The dependency for ROI has a maximum, i.e. there is an optimal amount of acid that provides the greatest economic effect. In FIG. Figure 8 shows the calculated dependence of the return on investment ratio ROI on the volume of the acid composition.

Model Validation

One way to verify the accuracy of model calculations is to compare them with the results of field measurements. The capabilities of the mathematical model were tested according to the data of acid treatments at 10 wells of the Mishkinsky, Esinei, Mikhailovsky, Krasnogorsk, Gremikhinsky, Kotovsky, Kiengopsky, Lozolyuksko-Zurinsky fields. At these wells, special tools were used to record changes in bottomhole and wellhead pressures, and injection rate. Based on the comparison of the dynamics of the face p _w p and wellhead pressure of _mouth conditions minimizing functional

model calibration was carried out. Subsequently, the calibrated model was used for predictive calculations of fluid production (total for water and oil) and the value of the additional increase in oil production in the studied wells.

The results of comparing the simulated and actual flow rates of the fluid and the increase in oil flow rates dQн after BSCO are shown in FIG. 9 and 10, respectively. Correlation analysis was carried out on 10 wells. Coefficient

correlation amounted to more than 90%.

The results of comparing the calculated and actual values of the bottomhole and wellhead pressures at one of the treated wells are presented in FIG. eleven.

Curves 1, 2, 3, and 4 describe the dynamics in time of the measured bottomhole pressure, calculated bottomhole pressure, measured wellhead pressure, and reagent injection flow rate, respectively. The estimated bottomhole pressure (curve 1) gives a satisfactory agreement with the measured bottomhole pressure (curve 2).

An example of the method

As an example, consider the design of a BSKO for one of the wells of the Mishkinsky field of OAO Udmurtneft.

A four-layer formation is considered. Oil saturated formation thickness is 5.6 meters. The current skin factor of the well is 10. Water cut is 25%.

Option 1.

By the method of mathematical modeling, the design of the BSKO is calculated without calculating the optimal injection rate of the acid composition, the optimal ratios of the volumes of the diverter and the acid composition, and the total optimal volume of the acid composition. This design will be called basic. Table 1 contains the initial data for the calculation of the basic design. In the first stage, the acid composition is pumped at a speed of 0.3 m ³ / min - a 12% aqueous solution of hydrochloric acid with modifiers of 5 m ³ .

In the second stage, a deflector (invert emulsion solution - INER) with a volume of 10 m ^{3 is} pumped at a speed of 0.3 m ³ / min. In the third stage, at a speed of 0.3 m ³ / min, a 12% aqueous hydrochloric acid solution with modifiers of 7.5 m ^{3 is} pumped. Optimization of acid volume and injection rate

composition was not carried out.

The calculation results are shown in table 2. The total volume of the acid composition is 12.5 m ³ ; deflector volume -10 m ³ . The fluid flow rate before treatment was 7 m ³ / day, after treatment it increased to a value of 19.4 m ³ / day. The oil production rate before treatment is 4.7 m ³ / day, after processing -13 m ³ / day. The calculated oil growth ratio is more than 2.76 units. The skin factor decreased from s = 10 to s = -0.36. The projected net present value (NPV) amounted to 8896.81 thousand rubles.

Option 2

The method of mathematical modeling is used to calculate the design corresponding to the claimed method. Table 3 contains the initial data for the design. In the first stage, with an optimum speed of 0.4 m ³ / min for this stage, the acid composition is pumped - a 12% aqueous hydrochloric acid solution with modifiers of 5 m ³ . In the second stage, at a speed of 0.4 m ³ / min, an INER brand diverter is pumped with a volume of 15 m ³ . In the third stage, with an optimal speed of 0.9 m ³ / min, a 12% aqueous hydrochloric acid solution with modifiers of 11 m ^{3 is} pumped.

The volume of the acid composition is -17 m ³ ; deflector volume - 15 m ³ . The fluid flow rate before treatment was 7 m ³ / day, after treatment it increased to a value of 21.4 m ³ / day. The oil production rate before treatment is 4.7 m ³ / day, after processing - 14.4 m ³ / day. The calculated rate of increase in oil flow rate is 3.06 units. Skin factor decreased from value

s = 10 to the value s = -1.33. The projected net present value (NPV) amounted to 10772.22 thousand rubles. The calculation results are shown in table 4.

To compare the present invention with the base in table 5 presents the results of the calculations for the above two examples. The table contains the main indicators characterizing the increase in the effectiveness of BSKO.

Comparison of the calculation results for the presented two design options shows an increase in efficiency during the BSKO in accordance with the proposed technical solution. Forecast estimates for the increase in oil production rate exceed the data on the base method by 1.4 tons / day. The skin factor decreased by almost 3.5 times, net present value was increased in comparison with the base by 1865 thousand rubles.

The claimed method allows for more efficient design design of BSKO wells in carbonate reservoirs due to:

- determining the optimal injection rate of the acid composition;

- establishing the optimal ratio of the volume of the diverter to the volume of the acid composition;

- calculation of profitable volumes of acid composition for each stage of processing.

Claims (2)

1. The method of large-volume selective acid treatment (BSCF) of production wells in carbonate reservoirs, including the injection into the well of the rim of the acid composition with a specific volume of 1.5-3 m ³ per 1 m of oil-saturated interval and a nonlinearly viscous deflecting fluid-deflector before and / or after the rim of the acid composition, characterized in that the injection of the acid composition is carried out with an optimal flow rate and an optimal ratio of the volume of the deflector to the volume of the acid composition, which are determined by mathematical modeling of process taking into account changes in wellhead and bottomhole pressure, type of acid composition, type of diverter, porosity and permeability of the rock, and to optimize the injection rate of the acid composition, the dependences of the optimal injection rate on the specific injection volume of reagents with different reaction constants are obtained in order to minimize the error in calculating the optimal flow rate injection of acid composition, the volume of each subsequent rim is determined according to the ratio

Where

- total volume of acid composition,

- the volume of the first pack, n is the number of stages,
to determine the optimal ratio of the volume of the deflector to the volume of acid use the criterion

where S _d , S _{d max} - pseudo-skin of the deflector and its maximum value, respectively, D, D _max - the dispersion of the flow rate across the interlayers and its maximum value, respectively,
the volume of the deflector is determined depending on the heterogeneity of the medium and taking into account the specified specific volume of the acid composition, while the optimal volume of the deflector

for each i-th stage is determined by the relation

and the optimal amount of acid providing the greatest economic effect is determined by the calculated dependence of the return on investment ratio on the volume of the acid composition. 2. The method according to p. 1, characterized in that the acid composition is pumped into several rims, and the diverter is pumped before, and / or after, and / or between the rims of the acid composition.

Images