RU2139425C1 - Method for treating bottom-hole zone of low-productive reservoirs in bed - Google Patents

Abstract

FIELD: oil producing industry. SUBSTANCE: method is aimed at increasing output capacity of low-productive beds. According to method, injected into bed is acidic solution and organic solvent. Before injection of acidic solution, well is cleaned by muriatic acid bath. After injection of acidic solution, injected is organic solvent. Then, well undergoes technological pause, and after that, well is put in operation. Used in function of acidic solution is mixture of muriatic acid and hydrofluoric acid, and used in function of organic solvent are low-grade spirits, glycols, acetone or light fractions of oil-processing. EFFECT: high efficiency. 2 cl, 1 tbl

Description

 The invention relates to the oil industry, in particular to methods for increasing oil recovery of low-productive formations stacked with terrigenous reservoirs, and can be used to restore the permeability of the bottom-hole formation zone of production and injection wells.

 Known methods for treating the bottom of the formation with acid and clay acid solutions containing various additives in the form of surfactants, hydrocarbon liquids and alcohols [1].

 The disadvantage of the described methods is the low efficiency as a result of the lack of technological methods that enhance the effect of acidic solutions.

 Closest to the proposed technical essence is a method comprising sequential treatment of the bottomhole formation zone with methyl or ethyl alcohol or a mixture thereof, and then with an acid solution [2].

 The disadvantage of this method is that the effect of stabilization of clays with methyl or ethyl alcohol is achieved before acid treatment and is temporary in relation to water-sensitive clays.

 The objective of the invention is to increase the productivity of low-productivity formations composed of reservoirs with a high content of clay minerals by restoring reservoir properties of the formation by cleaning and expanding existing and creating new fluid-conducting channels, stabilizing clays in remote areas of the bottomhole zone and throughout the perforated thickness of the formation.

 The problem is solved in that in the method for treating the bottom-hole zone of low-productivity reservoir reservoirs, which includes injecting an acid solution and an organic solvent into the reservoir, the well is cleaned with a salt-acid bath before the acid solution is injected, and after the acid solution is injected, the organic solvent is pumped, then the technological exposure of the well is carried out after which it is put into operation.

 Clinic acid (a mixture of hydrochloric and hydrofluoric acids) is pumped as an acid solution.

 As an organic solvent, lower alcohols, glycols, acetone, or light refined fractions are used.

 After injecting the organic solvent, the well is preserved for a calculated period of time, determined by the filtration-capacity characteristic of the formation.

 The essence of the proposed method lies in the processing technology of the PPP, which includes a certain sequence of injection of stimulating solutions and the estimated exposure time between subsequent injections.

 For primary cleaning of the bottom-hole zone (BHP) of the well from metal hydroxides, cement, metal carbonates, a solution of hydrochloric acid is pumped and held for 24 to 48 hours, after which the well is washed from the reaction products. After the well is cleaned of carbonates and metal hydroxides capable of forming insoluble salts with hydrofluoric acid, the maximum possible (technologically) volume of clay acid is pumped and held for 12-24 hours for the dissolution of the clay forming the reservoir to occur. As a result, the permeability of the formation is restored by cleaning and expanding existing and creating new fluid-conducting channels in remote areas of the bottom-hole zone of the formation and throughout the perforated thickness of the formation. The final operation is the stabilization and dehydration of clay minerals by injection of solvent into the formation.

 After the estimated time after the injection of stimulating solutions, the well is put into operation.

The proposed method of influencing the bottomhole zone was carried out after conducting geophysical and field-hydrodynamic studies. The work was carried out at facilities with a low productivity collector. Plast AB $\genfrac{}{}{0ex}{}{\text{(1-2)}}{\text{1}}$ Samotlor field is characterized by a random layered-lens alternation of clay and sand-aleuralite rocks. According to the facies affiliation, the reservoir rocks are divided into groups. As a criterion for the separation of hazel grouse into lithological differences, the relative content of clay interlayers in the rock (Cgl) and the amplitude amplitude a _{nc are used} .

“Hazel grouse” is divided into clay “hazel grouse” (Kgl = 0.5-0.8, a _nc = 0.25-0.35), actually “hazel grouse” (Kgl = 0.25-0.5, a _nc = 0.35-0.5) and sandy "hazel grouse" (Cgl = 0.05-0.25, a _nc = 0.5-0.65).

Porosity varies in a wide range from 17.8 - 29.8%, the amplitude of the change in permeability estimates is also large 0.14 - 1.547 μm ² .

 The technological process of the proposed method includes three consecutive stages.

1. Preliminary cleaning of the bottomhole zone of the well with a hydrochloric acid solution (hydrochloric acid bath). A solution of 12% HCl + 0.1 - 0.3% surfactant is pumped into the well in a volume of 10-20 m ³ and incubated for 24 to 48 hours, after which the well is washed from the reaction products.

2. Processing of PZP with a clay acid containing 15% HCl + HF 4% in a volume of 20-30 m ³ , depending on the thickness of the formation. The well is aged for reaction for 12-24 hours.

 3. The last stage is the treatment of the well with solvent, the sale of oil and the preservation of the well for a period of time, determined by the filtration and capacity properties of a particular well.

The technology according to the proposed method is implemented in 15 production and one injection wells of the Samotlor field operating the AB layer $\genfrac{}{}{0ex}{}{\text{(1-2)}}{\text{1}}$ "grouse".

At least one meter of the formation thickness is injected with at least 2.4 m ^{3 of a} clay-acid solution and 2.1 m ^{3 of} solvent. The results of the work are presented in the table, from which it can be seen that the average increase in oil production per well amounted to 6.7 t / s, which is 3 times higher than the growth in production when using standard technology. The average fluid flow rate of one well after treatment by the proposed method is 19.2 t / s, which is 2.6 times higher than the average flow rate before treatment (7.3 t / s).

 The proposed method allows to increase productivity and speed up the development of low-productivity reservoirs of the Samotlor field without involving expensive teams of cattle and gas processing stations, which significantly reduces the cost of well operations and increases the efficiency of production activities.

Sources of information
1. Issues of increasing the efficiency of acid compositions for well treatment. V.N. Glushko, O.V. Pozdeev. -M .: VNIIU and ENP. 1998, p. 28 - 40.

 2. US patent N 3738425, class. E 21 B 33/13, 1973 - prototype.

Claims (3)

 1. The method of processing the bottom-hole zone of low-productivity reservoir reservoirs, which includes injecting an acid solution and an organic solvent into the reservoir, characterized in that the well is cleaned with a salt-water bath before the acid solution is injected, and after the acid solution is injected, the organic solvent is pumped, then the technological exposure of the well is carried out, after which it is commissioned.  2. The method according to claim 1, characterized in that as the acid solution is injected clay acid - a mixture of hydrochloric and hydrofluoric acids.  3. The method according to claim 1, characterized in that as the organic solvent using lower alcohols, glycols, acetone or light fractions of oil refining.

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