SU1074990A1 - Method of acid treatment of well - Google Patents

Abstract

THE METHOD FOR ACID TREATMENT OF A WELL, including injection into the reservoir of a hydrochloric acid solution, is due to the fact that in order to increase the penetration depth of the acid by lowering the temperature of the acid solution, a substance with a positive heat of dissolution in an aqueous medium. (L 4 CO WITH

Description

The invention relates to the operation of groundwater intakes, vertical drainage systems, and more specifically to methods for treating wells that contain carbonate water. The known method of acid treatment of wells that capture carbonate water-containing rocks by cyclic injection of acid into the formation 1. The disadvantage of this method is the low treatment efficiency due to the shallow penetration of acid into the formation. Closest to the invention is a method of acidizing a well, which involves injecting a solution of hydrochloric acid into the formation. The method assumes that, after each acid treatment cycle, a solution of the reagent forming poorly soluble or acid-insoluble compounds with carbonate rocks is pumped into the formation, the concentration of the reagent and its volume are selected so that the film of passivated carbonate rocks occupies most of the treated zone. acid in the previous cycle, as a passivating reagent, depending on the structure and lithologic composition of carbonate rocks, use 3–5% solution of К ZOlclc 10% solution. When they interact with carbonate rocks, poorly soluble and insoluble compounds are formed in the form of CaSQ and CaSiOgUl. A disadvantage of the known well treatment method is the relatively small penetration distance of the hydrochloric acid solution. Lots into the reservoir, due to the formation of a fine gelatinous amorphous-crystalline sediment of calcium salts (calcium silicate, calcium sulfate), clogging carbonate fractures, which makes it difficult for the solvent to penetrate into the reservoir. The purpose of the invention is to increase the penetration depth of the acid by lowering the temperature of the acid solution. The goal is achieved by the method of acid treatment of the well, including the injection of hydrochloric acid solution into the formation, before the injection of the acid solution into the formation, a substance is introduced with a positive heat of solution in an aqueous medium. As substances with a positive heat of dissolution, a number of substances can be used, for example, (NH4) C204-H O, KNOg,,, NaNOj, etc. Their dissolution in hydrochloric acid solution is accompanied by lowering the temperature of the hydrochloric acid solution, which ensures a decrease in the dissolution rate of carbonate rocks and, as a result, an increase in the range of penetration of the hydrochloric acid solution into carbonate rocks. Data on the dependence of the decrease in the rate of dissolution of calcium carbonate in a solution of hydrochloric acid on the introduction of substances with a positive heat of solution in an aqueous medium are presented in Table 1. Table 1

20 20, 20 0

0,017

2.5

4.6 10 0.014 0.012

6.3 15 0.010

U, 5 20 As can be seen from the table. 1, the introduction into the solution of hydrochloric acid substances with a positive heat of dissolution within concentrations from 20 to 30% provides a decrease in the rate of dissolution of calcium carbonate in the pact hydrochloric acid from 120 to 440% by decreasing the temperature of the hydrochloric acid solution by 11.5- 26 ,. The drawing shows the scheme of the implementation of the proposed method of treatment of wells, kaptiruyuschih carbonate water-containing rocks. In the well 1, the dripping carbonate rocks 2, a reagent line 3 is installed, equipped with a hydraulic packer 4 in the lower part. The reagent line 3 is kept in the well 1 by means of a support 5. In the hydraulic packer 4 on

10749904

Continued table. 1, the pipeline 6 is pumped out of the liquid and the valve 7 is closed. To the upper part of the reactant pipe 3, a tip 8 is installed, equipped with a pipeline 9 to discharge reaction products with the valve 10, a pressure gauge 11 and a pipeline 12 with a valve 13. The pipeline 12 is connected to a pump 14 connected to the tank 15 with hydrochloric acid solution. Into the tank 15, the estimated amount of injection with positive heat of dissolution is mixed, the solution of hydrochloric acid is stirred in any known manner and with the valve 10 closed and valve 13 open, the solution is pumped into the well 1. It is also possible to introduce a powder with positive heat dissolution into the formation directly along the conductor line 3 by any known method, for example by ejection. After ordering the solution, the valve 13 is closed. The end time of the treatment is controlled by any known method. After the end of the treatment, the equipment is dismantled, the water-lifting equipment is mounted and the well is pumped until the reaction products are completely removed from the formation. Example. A well with a diameter of 300 mm absorbs water limestones up to 250 m in depth. The static water level in the well is located at a depth of 72 m. The length of the water receiving part of the well is 12 m. The flow rate of the well has decreased from 160 to 45 in 14 years. equipped in the lower part with a packer isolating the water intake part of the well. The reagent line through the tip is connected to a pump connected to its bridges with a total volume of 25% concentration of saline acid, equal to 6 m. The temperature of underground JBOn lO-c, hydrochloric acid solution is 20 C. In a tank with a saline solution Acids with a concentration of 25% and a total volume of 6 m are recorded with 1, .8 tons of powdered potassium nitrate and mixed with compressed air. After reducing the temperature of the solution to 2 ° C, it is pumped into the reservoir. The temperature of the solution in the water intake part of the well and in the bottomhole zone decreased to 4.8 C. The total time of treatment of the well, controlled by the gas injection process, is 4 hours. The range of penetration of the hydrochloric acid solution into the reservoir was determined to be not less than 2.9 m, which is confirmed by the release of gases from an observation well located in the cluster. observation wells at this distance. After the well treatment, the equipment is dismantled, the water-lifting equipment is mounted, and the well is pumped through until the reaction products are completely removed. The flow rate after treatment increased to 200 MV-4. I Example2. The process is carried out similarly to example 1. The well treatment is carried out using ammonium chloride as a substance with a positive heat of solution. The volume of hydrochloric acid solution is 6 m, the amount of ammonium chloride injected is 1.2 tons. The solution temperature after the introduction of ammonium chloride decreased, and after injection of the solution into the reservoir, it is about 6 ° C in the downhole part of the well and in the bottom hole zone. The penetration distance of the hydrochloric acid solution into the reservoir is 2.2 m. The treatment time for the well is 3.5 hours. The flow rate of the well as a result of the treatment has increased from 45 to 200 m / h. Example 3. The process is carried out analogously to example 1. The well is treated using potassium chlorate as a substance with positive heat of dissolution. The volume of the hydrochloric acid solution of 6 m, the amount of potassium chlorate injected is 0.9 tons. The solution temperature after the introduction of potassium chlorate decreased to 3.8 ° C and after injection of the solution into the formation it is in the water intake part of the well and in the bottom hole zone 5.8 ° s The penetration distance of the hydrochloric acid solution into the reservoir is 2.15 m. The well treatment time is 4 hours. The flow rate from the treatment increased from 45 to 205. Example 4. The process is carried out analogously to example 1. The well is processed using potassium chlorate as a substance with positive heat of dissolution. The volume of the solution of hydrochloric acid 6 m, the amount of potassium chlorate injected is 1.5 tons. The temperature of the solution after the introduction of potassium chlorate decreased to -2 ° C and after injection of the solution into the formation it is 4 ° C in the well receiving part of the well. The penetration distance of the hydrochloric acid solution into the reservoir is not less than 3.2 m. The well treatment time is 4.5 hours. The flow rate of the well is increased from 45 to 235 m3 / h. Comparative data indicating the advantage of the proposed method in comparison with the known, are given in table. 2. Table 2 Well flow rate, when commissioned 160 160 before processing 45 45 after treatment 110 220 The range of penetration of the solution with | N acid into the reservoir, m1.0 2.9

Long table 2

Processing time, h

Additional amount of water taken due to treatment, m3 / h

The proposed method, in comparison with the known, provided that the known base object coincides, provides an increase in the penetration rate of the hydrochloric acid solution into the formation from 1.0 to 2.9 m by reducing the rate of dissolution of carbonate rocks by lowering the temperature of the hydrochloric acid solution. This allows an additional amount of water withdrawn due to treatment to be increased from 65 to 175, with a reduction in treatment time of more than 2 times.

Claims (1)

METHOD FOR ACID TREATMENT OF A WELL, which includes injecting a solution of hydrochloric acid into the formation, which is characterized in that, in order to increase the depth of acid penetration by lowering the temperature of the acid solution, a substance with positive heat of dissolution in the aqueous medium is introduced into the formation before injecting the acid solution into the formation. 10749 .1074990