RU1319660C - Method for treatment of bottom-hole zone of formations nonuniform in permeability - Google Patents

Abstract

FIELD: oil producing industry. SUBSTANCE: after arrangement of wellhead equipment ensuring injection of working reagent, injected into formation through tubing is emulsifier in the amount of 0.1-0.2% of working agent volume. Then, working agent is injected in form of aqueous solution of acid or solvent of resin-wax deposits based on hydrocarbon. In case of application of the solvent as working agent, emulsifier is injected simultaneously with it. After injection of working agent into formation, it is left there for reaction. At this period, cyclic depression is created by reducing in each successive cycle the lower and upper levels of pressure by 2-25% Pressure variation conditions are selected depending on reservoir properties and formation pressure. EFFECT: higher efficiency of treatment due to provision of conditions preventing formation of screening layer, and promotion of withdrawal of reaction products from formation. 3 cl, 2 dwg, 2 tbl

Description

 The invention relates to the oil industry, in particular to methods for processing bottom-hole formation zone.

 The aim of the invention is to increase processing efficiency by creating conditions that prevent the formation of a shielding rock layer and contribute to the removal of reaction products from the reservoir.

 Before the acid, a portion of an emulsifier is pumped, for example ES-2 (emulsifier-stabilizer); in the event that the working fluid is a hydrocarbon-based solvent used to remove resin-paraffin deposits from the formation, an emulsifier is added to the first portion of the solvent; preliminary injection of a portion of the emulsifier its introduction into the first portion of the solvent in the formation conditions form an emulsion with a high viscosity, which increases the hydraulic resistance of highly permeable layers, i.e., creates the conditions for directed processing of low-permeability sections of the formation.

 The treatment of the bottom-hole zone of the formation is carried out in a dynamic mode due to a systematic change in pressure at the bottom of the well, which increases the dissolution rate and the completeness of the reaction (dissolution) due to the prevention of the formation of a shielding layer on the surface of the pore space. This also contributes to the formation of an emulsion in well-drained sections of the formation, thereby increasing their resistance to solvent penetration.

 The dynamic treatment mode is achieved by stepwise changing the pressure at the bottom of the well with a general tendency to decrease in time, which ensures the movement of the acid solution and reaction products towards the bottom of the well during acid treatment. This eliminates the possibility of fixing the reaction products in the formation and contributes to a more complete cleaning of the formation. Moreover, as laboratory and pilot tests have shown, the best processing results are achieved when the pressure changes of the upper and lower levels in the cycles are in the range of 2-25%. This is explained by the fact that when the pressure changes in the range from 2% and lower there is no destruction of the shielding layer on the rock surface, since the momentum of fluid movement in the reservoir from such a change in pressure is very weak. Changing the pressure in cycles above 25% is also ineffective due to the reduction in the number of cycles, which reduces the efficiency of emulsion formation. In addition, with significant changes in bottomhole pressure, formation rock destruction is possible.

 The pressure change mode is selected depending on the reservoir properties of the formation and reservoir pressure.

 In FIG. 1 shows the nature of pressure changes during the implementation of the method for conditions of low or low permeability of the formation and high reservoir pressure; figure 2 for conditions of low permeability of the reservoir and low pressure.

 Bottom zone treatment is carried out in the following sequence. Bind the wellhead with one or two pumping units, as well as with a compressor (if necessary, use the treatment regime, see figure 2) according to the scheme, which ensures the pumping of working fluid (acid or solvent) through the tubing, as well as the possibility of creating at the bottom of the well repressions and depressions in a wide range of pressure changes.

 For carbonate reservoirs, before feeding hydrochloric acid to the formation, a portion of the emulsifier of the inverse emulsion of the ES-2 type is completed in an amount of 0.1-0.2% of the acid volume. The acid solution is injected at the highest possible speed, which makes it possible to reduce the time of acid delivery to remote areas, while maintaining its activity. The injected acid in the formation under pressure is maintained for 10-15 minutes, then the pressure in the formation is reduced by a certain amount within 2-25% of the initial one. After a period of 10-15 minutes, the pressure is increased by an amount at which the total repression on the formation should not exceed the initial one. It should be less than this value. The cyclic treatment is repeated until the pressure on the face decreases to the pressure of the hydrostatic column of liquid (according to option 1, Fig. 1). When processing the processing according to option 2, upon reaching the pressure in the next cycle equal to the hydrostatic, a compressor is connected to continue the cyclic change in pressure in the reservoir and the process is carried out until the well is developed (see figure 2).

 Table 1 shows the data of laboratory studies on the dissolution of carbonate reservoirs (limestone) in static and dynamic modes.

 According to the results of laboratory studies, the reaction rate under dynamic conditions is much higher even at low acid concentrations.

 For testing, wells were selected located in the boundary zones of the structure of the side of the folds with a very low characteristic of reservoir properties (porosity and permeability). Conducting conventional methods of hydrochloric acid treatment did not give positive results. No increase in production was also obtained in wells 1825, 2042, which were subjected to hydro-jet slit perforation with subsequent hydrochloric acid treatment.

 At all wells before and after the implementation of the method, a series of studies was carried out.

 The results of pilot tests are given in table.2.

 According to the results of studies, wells 750, 754, 1785, 1825, 1852 showed an increase in the working interval of the formation, which is associated with the selective action of acid as a result of blocking of highly permeable sections of the formation by the emulsion.

Claims (2)

1. METHOD FOR PROCESSING BOTTOM ZONE OF DIFFERENT RESISTANT STREDS, which includes injecting a working reagent solution into the formation and creating a cyclic depressive pressure in the formation during the reaction of the reagent, characterized in that, for the purpose of processing efficiency, by creating conditions that prevent the formation of a shielding rock layer and facilitate removal the reaction products from the reservoir, before the injection of the reagent, an emulsifier is fed into the reservoir, and in each subsequent cycle the lower and upper pressure levels are reduced by 2 25%
2. The method according to claim 1, characterized in that an aqueous acid solution or a hydrocarbon-based resin-paraffin deposit is pumped as a working reagent.  3. The method according to PP. 1 and 2, characterized in that the emulsifier is administered simultaneously with a hydrocarbon-based solvent.

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