SU953191A1 - Method of acid treatment of formation - Google Patents

Description

The invention relates to oil and gas production.

The known method is a hydroacid fracturing of a reservoir composed of carbonate rocks, which consists in pumping sulfuric acid or aqueous solutions of sulfuric acid salts into the reservoir as a fracturing fluid and subsequently pushing it with hydrochloric acid solution l.

The disadvantage of this method is that it does not provide an effective chemical attack on the formation in deep wells with high formation temperatures, since sulfuric acid reacts with carbonates very slowly, and solutions of sulfuric acid salts do not react with them at all.

There is also known a method of acid treatment of wells with sulfuric acid, which consists in the sequential injection of sulfuric acid into the formation and development; Bavitel 2.

The disadvantage of this method is the low treatment efficiency of the reservoir due to the low rate of dissolution of lime in acid, which does not provide a significant expansion of the filtration channels in the process.

The purpose of the invention is to increase the efficiency of formation treatment by increasing the rate of the reaction of the acid with carbonates.

The goal is achieved by the fact that according to the method as

10 diluents pump in an aqueous solution of salts of strong acids (hydrochloric, nitric, perchloric, etc.), which form water-soluble compounds with sulfuric acid.

15

among the most characteristic salts of strong acids that form water-soluble compounds with sulfuric acid are; hydrochloric acid salts; NaCl, KCl, MgClj; salts of nitric acid; 20No: NaNO ,, KNOj, NH4.N03, Mg (NO |),

ioi:

The cop

salts of perchloric acid: NaClO

44 NH.CIO ,, Mg (C10,) j.

In the implementation of the proposed method, aqueous solutions of salts of strong

25 acids, reacting with sulfuric acid, forming true solutions, generate a certain amount of corresponding acids (hydrochloric, nitric, perchloric), the presence of which increases the rate of dissolution of carbonate rock, which increases the efficiency of formation treatment. An aqueous solution of a salt of a strong acid is formed, forming water-soluble compounds with sulfuric acid. Mix the resulting solution with sulfuric acid. Processing is carried out in the following sequence. A wellhead with two pumping units is tied according to a scheme that injects acids | software into the well, pumping compressor tubes, and a solution of magnesium chloride is pumped through the annular space through a direct circulation to a 50 m solution of magnesium chloride with a concentration of 500 g / l, p1a separating a plug of light oil in a volume of 0.5 m, 14 m of acid and 0.5 m of light oil. As a result, the entire solution of magnesium chloride is placed in the well annulus. The valve is closed on the discharge line of the annulus and acid is pumped out of the pumping and compression pipes to absorb into the formation while simultaneously displacing the magnesium chloride solution from the annulus to dilute the acid to the well bottom. The pump capacity for pumping and pumping acid is 3 l / s, when pumping water for pushing magnesium chloride solution out of the annular space - b l / s at a pressure of 120140 kgf / cm o After all the acid is pumped into the well, it is forced into the reservoir 50 m with a flow rate of 9-10 l / s. Launch the well into operation. During processing, the injection pressure of the acid gradually decreases from 120-140 to 80 kgf / cm, which indicates an increase in the permeability of the bottomhole formation zone. After treatment, the injectivity of the wells increases to 1500 m / s at the same injection pressure. In-depth studies have shown that the permeability of the formation in a radius of up to 15 m is 320 mD. The method can also be carried out with sequential injection of sulfuric acid and solvent into the formation. Thus, the application of the method allows to increase the success and effectiveness of acid treatments of the formation in deep high-temperature wells due to the formation of filtration channels with high permeability both in the wellbore zone and at a considerable distance from the wellbore. The formation of these channels is due to the fact that when diluted with sulfuric acid with aqueous solutions of salts of strong acids, the latter form true solutions and generate some amount of the corresponding acids (hydrochloric, nitric, perchloric) according to the equations: MgS04 H.2, SO +, + 2NaCiq . ::: i 2CH10d + Na.7S04 I-LSO, z- n The presence in a solution of hydrochloric, nitric, perchloric and other acids formed at the bottom of the well or directly in the reservoir increases. the rate of dissolution of lime in the resulting mixture. The dissolution rate can be easily controlled by changing the concentration of salts in the diluent or the amount of diluent supplied to the bottom of the well to dilute the acid. The table shows the rate of dissolution of lime in solutions obtained by mixing 80% sulfuric acid with composite solutions of magnesium chloride.

Water

Aqueous solution of magnesium chloride

137 31

213

156

569

536

448 316 423 549 815 702 From the table it can be seen that the introduction of a solution of magnesium chloride into sulfuric acid makes it possible to significantly (522 times) increase the reaction rate with carbonates. By introducing various amounts of magnesium chloride into the acid, it is possible to effect the effective dissolution of the fracture walls in both the adjacent and remote zones of the formation while maintaining the high dissolving capacity of sulfuric acid. On the basis of actual processing, it was found that in order to achieve a positive effect, it is necessary to carry out three to four or more usual acid treatments. The actual costs are 45 thousand rubles. The application of the proposed method allows to obtain a positive result of one treatment and to obtain an economic effect of about 3 thousand rubles. per one operation.

Claims (2)

Continuation of the Table The claims of the invention 1. Method of acid treatment of the reservoir, which consists in pumping c. a layer of sulfuric acid and a diluent, characterized in that, in order to increase the efficiency of treatment of the formation by increasing the rate of the reaction of the acid with carbonates, a solution of salts of strong acids, which are water-soluble compounds with sulfuric acid, is pumped as a diluent. 2. A method according to pl, characterized in that magnesium chloride, sodium nitrate or potassium hydrochloride is used as a salt of a strong acid. Sources of information taken into account in the examination 1. US patent number 3428129, cl. 166-292, 1966. 2. Thermo-hydroacid treatment of injection wells with the use of sulfuric acid and water. Prospect VDNH USSR, VNIIOENG, T-12622, 1975 (prototype).