RU2269648C1 - Bottomhole formation area acidizing method - Google Patents

Abstract

FIELD: oil production industry, particularly methods for stimulating production with the use of eroding chemicals, for instance acids.

SUBSTANCE: method involves serially ejecting emulsion and acid solution into bottomhole formation zone. The emulsion comprises hydrochloric acid HCl of 15-20% concentration in amount of 44.1-51.1% by weight, carboxymethyl cellulose of 1.5-2.0% concentration in amount of 1.5-2.5% by weight and 46.4-54.4% by weight of water. The acid solution includes hydrochloric acid HCl of 15-20% concentration in amount of 34.5-56.6% by weight, benzoic acid C₆H₅COOH with 0.25-0.5% concentration in amount of 0.25-0.5 and 42.9-62.25% by weight of water.

EFFECT: increased depth of acid solution penetration into formation.

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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.

A known method of increasing the influx of oil and gas, based on the injection into the reservoir of aqueous solutions of hydrochloric acid or a mixture of hydrochloric acid with hydrofluoric acid, etc. (D.I. Bulatov, Yu.D. Kachmar and others. Development of wells. 1999, p.342 -343).

The disadvantage of this method is the weak penetration of the acid solution into the reservoir. This method can only be used with simple acid treatments.

Closest to the proposed method is a method of acid treatment of an oil reservoir, in which a hydrophobic emulsion is injected into the reservoir before the injection of acid (AS USSR 898047, E 21 B 43/22. Declared 03/14/80. Published 01/15/82. Bull. No. 2. O.F. Martyntsiv, M.Sh. Kendis, etc.).

The disadvantage of this method is the low penetration of acid into the formation. This method is used in hydrophobic reservoirs having predominant wettability with hydrocarbon liquids. In hydrophilic reservoirs, injection of a hydrophobic emulsion does not increase the depth of penetration of the acidic solution due to the predominant wettability of the reservoir by the aqueous phase.

The problem to which the invention is directed, increasing the permeability of the bottomhole zone of the well.

The technical result is an increase in the depth of penetration of the acid solution into the reservoir.

The specified technical result is achieved by the fact that in the known method of acid treatment of the bottomhole formation zone, which includes sequential injection of the emulsion and the acid solution, in contrast to the prototype, an emulsion of the composition, wt.%:

hydrochloric acid HCl 15-20% concentration 44.1 - 51.1 CMC carboxymethyl cellulose 1.5-2.0% concentration 1,5 - 2,5 water 46.4 - 54.4 and an acidic solution of the composition, wt.%: hydrochloric acid HCl 15-20% concentration 34.5 - 56.6 benzoic acid C ₆ H ₅ COOH 0.25-0.5% concentration 0.25 - 0.5 water 42.9 - 62.25

The method is as follows. The tubing is lowered into the well 5-6 m above the perforation interval. Using a cementing unit, an emulsion is prepared for injection into formations based on an aqueous solution of acid and carboxymethyl cellulose. For this, the aggregate hopper is filled with water in a volume of 0.232 m ³ (water density at a temperature of 20-22 ⁰ С - 1000 kg / m ³ ) or 232 kg (46.4 wt.%) Is added to water 12.5 kg (2.5 wt.%) carboxymethyl cellulose, stirred, injected with hydrochloric acid of 20% concentration of 255.5 kg (51.1 wt.%) and mixed emulsion. The volume for injection into the reservoirs is determined by the formula:

V _r = 9.42 (R ² -r ² ) n

where n is the density of cracks in 1 running meter, ¹ / m;

h is the effective thickness, m;

δ — crack opening, m;

r is the radius of the well, m;

R is the radius of processing, m

For calculation, we accept the following parameters:

r = 0.068 m for production casing with a diameter of 0.146;

δ = 0.0005 m; R = 1 m; h = 20 m.

The estimated volume of the emulsion is equal to:

V _r = 9.42 (1 ² - 0.068 ² ) * 4 * 0.0005 * 20 = 0.37 m ³ .

An acid solution is prepared at the same time. For this, the aggregate hopper is filled with water in a volume of 0.312 m ³ (water density at a temperature of 20-22 ⁰ С - 1000 kg / m ³ ) or 312 kg (62.25 wt.%), Benzoic acid of 0.5% concentration is added 2.5 kg (0.5 wt.%), Stirred, injected with hydrochloric acid of 20% concentration of 186.7 kg (37.25 wt.%) And mixed.

The estimated volume of the acid solution is equal to the volume of the emulsion - 0.37 m ³ .

Then the emulsion is pumped into the well to open the cracks and pre-treat the rock cracks with hydrochloric acid. The emulsion is pressed into the reservoir with an acid solution, and the total volume of the emulsion and the acid solution is 0.74 m ³ .

The emulsion is pressed into the reservoir at a pressure (P _k ) below the hydraulic fracturing pressure (P _fracturing ),

those. gradient P _to < _fracture gradient P.

_{hydraulic fracturing} gradient P <Р _{hydraulic fracturing / 0.01 n} .

If P _{fracturing is} unknown, then it is determined by the formula:

gradients P _{hydraulic fracturing} = 100 (P _GTS + 0.008 N) / N,

where R _GTS is the hydrostatic pressure of the liquid column, MPa;

N - well depth, m

P _GTS = ρg · H,

where ρ is the density of the liquid, kg / m ³ ;

g is the acceleration of gravity, m / s ² ;

g = 9.81 m / s ² .

The injection pressure of the acid solution is determined from the bedding conditions of the Achimov deposits.

The reservoir pressure R _pl = 55.0 MPa, the depth of bed N = 3600 m, the pressure of the pressure of the column P = 30.0 MPa, the density of the fluid filling the well, ρ = 1000 kg / m ³ .

In this case, the hydrostatic pressure is equal to:

P _GTS = ρ · g · H = 1000 · 9.81 · 3600 = 35.3 MPa.

Then fracturing pressure gradient of the gradient P _SRC = 100 (P + 0,008N _GTS) / N = 100 (35.3 + 0.008 · 3600) / 3600 = 1.8 MPa / 100 m.

If the reservoir pressure is 55.0 MPa, then the bottomhole pressure during injection of the mixture of acids, representing the sum of the pressures: at the mouth of 22.0 MPa and hydrostatic - 57.3 MPa.

The gradient of the injection of the emulsion and the acid solution is determined by the formula:

gradient P _k = P ₃ / 0.01N ₁ = 57.3 / 35.5 = 1.56 MPa / 100 m,

where H ₁ - the middle of the interval of the reservoir, m;

P ₃ - injection pressure, MPa;

gradient P _to < _fracture gradient P.

The emulsion provides crack opening and primary treatment of crack walls with acid. The injection of an emulsion of the claimed composition overlaps part of the cracks, but the main fluid-conducting cracks remain open. Carboxymethyl cellulose located in the fractures of the formation dissolves in hydrochloric acid and does not violate the filtration characteristics of the formation. The final acid treatment is carried out with a solution of hydrochloric and benzoic acids. An increase in the radius of penetration of this acid solution is provided by benzoic acid. After injection of the acid solution, the well is left to react for one hour, and after the reaction, the well is mastered and put into operation.

Experiments on the injection of an acid solution into core samples are carried out according to the following procedure.

Select core samples taken in a fractured-pore reservoir, in which the initial oil saturation is modeled. The sample is installed in the core holder of the installation, where in reservoir conditions the kerosene flow rate and pressure drop are determined.

In the next step, a weighted drilling fluid containing a clay component and a weighting agent is pumped into the sample. The injection pressure of the drilling fluid is equal to the repression pressure that occurs when opening the fractured-pore reservoir. In order to determine the degree of colmatation of the sample with drilling fluid, kerosene is pumped from the opposite side of the sample and the flow rate and pressure drop are determined.

In the absence of flow or with its insignificant values, an emulsion is pumped into the sample in an amount of 1-2 pore volumes, which is replaced with a solution of hydrochloric and benzoic acids in an amount of 2-3 pore volumes. Leave the sample to respond for one hour.

After completion of the reaction, the acid solution and reaction products are removed from the sample with kerosene at a pressure equal to the depression applied to the formation during well development. The experimental results are given in the table. From the experimental results it follows that after the drilling fluid is injected into the fractured-pore sample, the sample becomes colmatized and the filtration pressure of kerosene increases by a factor of 150 or more.

The phased injection of the emulsion and acid solutions leads to a complete cleaning of the system of conducting cracks from the clogging components and the restoration of the filtration properties of the samples.

Table The results of laboratory experiments to assess the effect of penetration of acidic solutions on core samples of a fractured-pore reservoir Deposit, type of collector Porosity,% Initial Experience Parameters After injection of the weighted drilling fluid The composition of the emulsion After acid treatment Kerosene consumption, m ³ / s Pressure drop, MPa Kerosene consumption, m ³ / s Pressure drop, MPa Kerosene consumption, m ³ / s Pressure drop, MPa Yamburg Stage 1 fissure 10.5 2.3 · 10 ^-6 0.002 2.4 · 10 ^-6 0.47 20% HCl + 2.5% CMC 2.2 · 10 ^-6 0.0027 pore 2 stage 20% HCl + 0.5% C ₆ H ₅ COOH Yamburg Stage 1 fissure 10,4 2.3 · 10 ^-6 0.0025 2.3 · 10 ^-6 0.30 20% HCl + 2.5% CMC 2.4 · 10- ⁶ 0.002 pore 2 stage 20% HCl + 0.5% C ₆ H ₅ COOH

Claims (1)

The method of acid treatment of the bottom-hole zone of the formation, including the sequential injection of the emulsion and the acid solution, characterized in that they use the emulsion composition, wt.%: Hydrochloric acid HCl 15-20% concentration 44.1 - 51.1 CMC carboxymethyl cellulose 1.5-2.0% concentration 1,5 - 2,5 Water 46.4 - 54.4 and an acidic solution of the composition, wt.%: Hydrochloric acid HCl 15-20% concentration 34.5 - 56.6 Benzoic acid C ₆ H ₅ COOH 0.25-0.5% concentration 0.25 - 0.5 Water 42.9 - 62.25