RU2502868C1 - Acid treatment method of bottom-hole zone of well in carbonate formation - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: in an acid treatment method of bottom-hole zone of a well in a carbonate formation, which involves pumping of acid solution to the well, forcing-through of acid solution with forcing-through fluid, exposure of the well for reaction of acid solution and well development, prior to pumping of acid solution to the well there determined is porosity and permeability of a productive formation, as well as productive formation temperature. After that, volume pumping rate of acid solution and forcing-through fluid is calculated as per the following formula:, where q - volume pumping rate of axis solution and forcing-through liquid to the well, m/s; h - productive formation thickness, m; T - productive formation temperature, K; K - productive formation permeability, mcm; m - productive formation porosity, unit fractions; q- empirical coefficient equal to 0.05 to 0.20. Acid solution and forcing-through liquid with calculated volume rate is pumped. Acid solution pumping is performed under pressure on the working face below natural mircocrack opening pressure.EFFECT: improving processing efficiency of bottom-hole zone of a well in a carbonate formation due to formation of deeply penetrating passes in the bottom-hole zone; preventing neutralisation of acid solution on well surface with formation of cavities; excluding well drowning.

Description

The invention relates to the oil and gas industry and can be used in the treatment of the bottom-hole formation zone during oil and gas production.

The closest technical solution to the proposed one is the method of acid treatment of the bottom-hole zone of a well in a carbonate formation, which includes injecting an acid solution into a well, forcing an acid solution with a squeezing fluid, and holding the well for the reaction of an acid solution (see Yu.P. Korotaev, A.P. Polyansky , Operation of gas wells, M., 1961, p. 328-341).

The disadvantage of this method is that when carrying out acid treatments, the filtration-capacitive characteristics and the temperature of the formation are not taken into account, which leads in some wells to neutralize the acid solution on the surface of the well wall with the formation of caverns and deep-penetrating channels in the bottom-hole zone are not formed, which reduces the effectiveness of the treatments .

The technical result, the achievement of which the present invention is directed, is to eliminate this drawback, namely, increasing the efficiency of processing the bottom-hole zone of the well in the carbonate formation, by forming deep-penetrating channels in the bottom-hole zone, preventing the neutralization of the acid solution on the surface of the wall of the well and eliminating water flooding of the well.

The technical result of the invention is achieved due to the fact that in the method of acidizing the bottom-hole zone of a well in a carbonate formation, which includes injecting an acidic solution into a well, pushing an acidic solution with a squeezing liquid, keeping the well for reacting the acidic solution and developing the well, before determining the acidic solution into the well, porosity and permeability of the reservoir, as well as the temperature of the reservoir, after which the volumetric acid injection rate is calculated a different solution and squeezing fluid into the well according to the formula:

$$q=q_0\cdot \frac{e^{25.8}-\frac{7550}{T}}{\sqrt[10]{\frac{K}{m}}}\cdot h$$

where q is the volumetric rate of injection of the acid solution and squeezing fluid into the well, m ³ / s;

h is the thickness of the reservoir, m;

T is the temperature of the reservoir, K;

K is the permeability of the reservoir, μm ² ;

m is the porosity of the reservoir, fractions of a unit;

q ₀ is an empirical coefficient equal to from 0.05 to 0.20,

and pumping the acid solution and squeezing liquid with the calculated volumetric rate, while the acid solution is pumped into the well under pressure at the bottom below the opening pressure of natural microcracks.

The method is as follows.

They treat the bottom-hole zone of a gas producing well with a depth of 1800 m. The carbonate reservoir, the thickness of the reservoir is 22 m. The well is equipped with a tubing with an internal diameter of 76 mm. Prepare the estimated volume of the acid solution and squeezing liquid. To treat the bottom-hole zone of the formation, the volume of the hydrochloric acid solution is equal to 25 m ³ and the squeezing liquid is 12 m ³ . Geophysical studies or core studies determine the porosity and permeability of the formation. The average permeability is 0.195 μm ² , the porosity is 0.18. The temperature of the formation is determined, for example, by a depth thermometer or according to the tabular data of the field in question. The temperature measured by the depth thermometer is 308 K.

Then calculate the volumetric rate of injection of the acid solution and squeezing fluid into the well according to the formula

$$q=q_0\cdot \frac{e^{25.8}-\frac{7550}{T}}{\sqrt[10]{\frac{K}{m}}}\cdot h$$

where q is the volumetric rate of injection of the acid solution and squeezing fluid into the well, m ³ / s;

h is the thickness of the reservoir, m;

T is the temperature of the reservoir, K;

K is the permeability of the reservoir, μm ² ;

m is the porosity of the reservoir, fractions of a unit;

q ₀ is an empirical coefficient equal to from 0.05 to 0.20,

$$q=0.1\cdot \frac{e^{25.8}\cdot \frac{7550}{303}}{\sqrt[10]{\frac{0.195}{0.18}}}\cdot 22=0.766{\text{m}}^{\text{3}}\text{/ min}$$

Take the injection rate of 0.8 m ³ / min. The wellhead is tied up with high pressure pumps with tanks for acid solution and squeezing liquid, acid solution and squeezing liquid are pumped with a volumetric velocity of 0.8 m ³ / min. The well is kept for one hour for the reaction of the acid solution and the well is mastered.

To exclude waterlogging as a result of the opening of microcracks, the injection of the acid solution is carried out under a pressure below the opening pressure of natural microcracks.

The dissolution of the carbonate reservoir during the injection of the acid solution and then the squeezing liquid at a rate lower than the calculated space velocity occurs in the mode of cavern formation, i.e. neutralizing acid on the surface of the wall of the well. To obtain deep-penetrating channels, it is necessary that the rate of supply of the acidic solution is greater than the rate of the chemical reaction (rate of neutralization of the acidic solution), which depends on the temperature, porosity, and permeability of the reservoir. The injection of an acid solution and a squeezing fluid with a volume velocity calculated by the above formula (volume velocity greater than the rate of neutralization of the acid solution) leads to the formation of deeply penetrating channels in the bottomhole zone and to prevent the neutralization of the acid solution on the surface of the well wall.

Thus, the use of this invention allows to increase the efficiency of processing the bottom-hole zone of a well in a carbonate formation.

Claims (1)

A method of acidic treatment of a bottomhole zone of a well in a carbonate formation, including injecting an acidic solution into a well, pushing an acidic solution with a squeezing liquid, keeping the well for reacting the acidic solution and mastering the well, characterized in that before the acidic solution is injected into the well, the porosity and permeability of the producing formation are determined, as well as the temperature of the reservoir, after which the volumetric rate of injection of the acid solution and squeezing fluid into the well is calculated formula according to the formula
$$q=q_0\cdot \frac{e^{25.8}-\frac{7550}{T}}{\sqrt[10]{\frac{K}{m}}}\cdot h$$

,
where q is the volumetric rate of injection of the acid solution and squeezing fluid into the well, m ³ / s;
h is the thickness of the reservoir, m;
T is the temperature of the reservoir, K;
K is the permeability of the reservoir, μm ² ;
m is the porosity of the reservoir, fractions of a unit;
q ₀ is an empirical coefficient equal to from 0.05 to 0.20,
and pumping the acid solution and squeezing liquid with the calculated volumetric rate, while the acid solution is pumped into the well under pressure at the bottom below the opening pressure of natural microcracks.