RU2494245C1 - Treatment method of bottom-hole formation zone - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: acid treatment method of a bottom-hole formation zone involves pumping to the formation of emulsion and water solution of an acid; at that, first, water solution of acid is pumped, and pumping of water solution of acid and emulsion is performed in a series-and-alternating mode, and emulsion containing the following components, wt %, is used as emulsion: acid 5.0-40.0; emulsifier - anionic or nonionic, or cationic surface-active substance, or their mixture 1.0-10.0; hydrocarbon solvent 5.0-40.0; decomposer - primary or secondary alcohol or their mixture 0.1-5.0; corrosion inhibitor 0.01-0.05 and water is the rest. Emulsion can contain viscosity regulator in the quantity of 0.01-6.0 wt %. Water solution of acid with concentration of 3.0-24.0% is used.

EFFECT: deceleration of a reaction of acid with rock of the formation, enlarging the treatment coverage range as to thickness and depth of the formation using an emulsion, preserving stability, reducing intensity of acid corrosion and having washing effectiveness in relation to asphaltene-resin-wax-bearing deposits.

3 cl, 3 tbl, 29 ex

Description

The invention relates to the oil industry and can be used for acid treatment of the bottomhole formation zone, represented by heterogeneous permeability carbonate or terrigenous reservoirs.

There is a method of processing the bottom-hole zone of a well in a multilayer oil reservoir, which includes pumping an oil emulsion into all formations, then a material that dissolves the oil component of the oil emulsion, and an acid solution, which is pumped intervalwise into oil formations (see RF Patent No. 2092686, MKI E21B 43 / 27, publ. 1997).

This method is not effective enough due to the complex interval processing with three different compositions, which does not provide selective penetration of acid into the oil-saturated interlayer and blocking by emulsion of a highly permeable water-saturated interlayer. Moreover, the injected emulsion remains in the oil reservoir and impairs its filtration performance.

A known method of acid treatment of the bottomhole formation zone, including sequential injection of an emulsion of the following composition, wt.%: Hydrochloric acid of 15-20% concentration - 44.1-51.1, carboxymethyl cellulose 1.5-2.5, and water - 46.4-54.4 and the acid composition containing, wt.%: Hydrochloric acid of 15-20% concentration, benzoic acid of 0.25-0.5 concentration and water - 42.9-62.25 ( see RF Patent No. 2269648, MKI E21B 43/27, publ. 2006).

However, the known method according to the technical result is aimed at increasing the depth of penetration of the emulsion into the formation by changing the wettability of the rock. In this case, there is no effective redistribution of filtration flows, the acid emulsion penetrates the water-saturated part of the reservoir and does not cover oil-saturated interlayers.

The closest to the proposed invention in technical essence and the achieved result is a method of processing the bottom-hole zone of the formation, which includes injecting into the formation a reverse oil emulsion and an aqueous solution of acid, where an emulsion containing the following components, vol.%, Is used as a reverse emulsion: hydrocarbon liquid 26- 40, an oil-soluble nitrogen-containing emulsifier Sonkor-9601 or Sonkor 9701-0.4-5.0, an aqueous solution of inhibited 10% hydrochloric acid or clay acid or an aqueous solution of 1-10% calcium chloride and whether sodium chloride - the rest (see RF Patent No. 2255215, MKI E21B 43/27, publ. 2005).

However, the application of this method is limited, since the decay time of the emulsion cannot be controlled depending on temperature, viscosity and the technological task to be solved, the result may be a deterioration in the filtration properties of the reservoir due to contamination with the emulsion used, which does not collapse after treatment of the well. Also, with a high iron content in the near-wellbore zone, an oil-acid emulsion tends to be tarred, which leads to colmatization of the oil layer by resins, products of the reaction of oil with acid in the presence of iron ions, especially these processes are significant at elevated temperatures.

The aim of the invention is to provide a method for processing the bottom-hole formation zone, which is highly effective by slowing down the rate of acid reaction with the formation rock, increasing the degree of treatment coverage by thickness and depth of the formation, using an emulsion that remains stable up to 120 hours at temperatures up to 60 ° C, reducing the intensity of acid corrosion and having detergent effectiveness in relation to asphalt resins and paraffin deposits.

This goal is achieved by creating a method for treating the bottom-hole zone of the formation, which includes emulsion and an aqueous acid solution being injected into the formation, whereby an aqueous acid solution is first injected, and the aqueous acid and emulsion solution are injected in a successively alternating mode and an emulsion of the following composition is used as an emulsion, mass%:

Acid - 5.0-40.0

Anionic or nonionic

or cationic surfactant

or their mixture - 1.0-10.0 Hydrocarbon solvent - 5.0-40.0

Primary or secondary alcohol

or their mixture - 0.1-5.0 Corrosion inhibitor - 0.01-0.05 Water - the rest.

In embodiments of the method, the emulsion may contain a viscosity regulator in an amount of 0.01-6.0 wt.%, And an aqueous solution of acid using 3.0-24.0% concentration.

As an aqueous acid solution, aqueous solutions of hydrochloric acid or a mixture of hydrochloric and hydrofluoric acids are used depending on the formation rock.

To prepare the emulsion as an acid use:

- hydrochloric acid according to GOST 857-95;

- hydrofluoric acid according to GOST 10484-78;

- sulfamic acid according to TU 2121-083-05800142-2001;

- acetic acid according to GOST 19814-74;

- formic acid according to GOST 1706-78;

- mixtures thereof.

Use anionic surfactants or nonionic surfactants or cationic surfactants or mixtures thereof, such as: decanol according to TU 6-09-1514-75; syntamide - 5K according to TU 2483-064-0580977-2003; emulsifier of cationic bitumen emulsions (ECBE) according to TU 0257-007-35475596-98; ITPS-04E according to TU 2458-003-27913102-2003; Cocoamine - a monoamine of fatty acids of coconut oil, made in China. - amdor according to TU 0257-003-35475596-96.

As a hydrocarbon solvent use:

- diesel fuel (DT) according to GOST 305-82;

- xylene according to GOST 9410-78;

- MIA-prom according to TU 4852-01127913102-2001;

- toluene according to GOST 14710-78;

- gasoline according to TU 0251-009-057-66801-93;

- fraction of aromatic hydrocarbons (FAA) according to TU 2414-00352927048-2005;

- mixtures thereof.

Primary or secondary alcohols are introduced into the composition to control the decay rate of the emulsion with the formation of mobile inorganic and hydrocarbon phases. As primary or secondary alcohols use for example: - methanol according to GOST 2222-95; - isopropanol according to TU 6-09-50-2655-94;

- secondary butanol according to GOST 6006-78;

- butyl cellosolve according to TU 6-01-646-84;

- ethyl cellosolve according to GOST 8313-88; or mixtures thereof.

As a corrosion inhibitor use:

- Dodicor -2575 - a product of the company "Clariant", USA;

- Prod Ci-300 - a product of the company "Chevron Fillips", USA:

- urotropin according to GOST 1381-73;

- formaldehyde according to GOST 1625-89;

- fatty ammonium salts.

As a viscosity regulator can be used:

- syntanol ES-3 according to TU 38-5901268-90;

- xanthan biopolymer according to TU 2458-002-50635131-2003;

- polyacrylamide according to TU 6-01-1049-92;

The emulsion used in the proposed invention can be prepared both under industrial production conditions and immediately before use by sequentially dissolving the components in the claimed amounts.

We give examples of the preparation of the emulsion.

Example 1 (the claimed emulsion).

While stirring with a mechanical stirrer, 2.0 g of decanol are added to 15.0 g of hydrochloric acid, then 40.0 g of a hydrocarbon solvent, a mixture of diesel fuel and xylene, are added to the resulting mixture at a ratio of 85:15, 0.1 g of methanol, 0.01 g of corrosion inhibitor - Dodikor and 42.89 g of water (see table 1, example 1).

Example 2, 4, 9, 13, 18, 27 are prepared analogously to example 1 without the addition of primary or secondary alcohols.

Example 3. While stirring with a mechanical stirrer, 1.0 g of ITPS-04E is added to 12.9 g of hydrochloric acid, then 12.94 g of a hydrocarbon solvent, MIA-prom, 4.0 g of methanol, 0.01 g, are added to the resulting mixture. corrosion inhibitor - Dodikor, 0.01 g viscosity regulator - syntanol ES-3 and 69.14 g of water (see table 1 example 3).

Examples 5-8, 10-12, 14-17, 19-26, 28 are prepared in a similar manner, changing the types of components and their content in the composition in the claimed quantities.

Example 29 (prototype).

0.2 g of the emulsifier - Soncor-9601 is dissolved in 26.0 g of diesel fuel with vigorous stirring, then 7.38 g of hydrochloric acid is added in 3 doses and mixed for 5 minutes (see table 1, example 25).

According to the claimed method, the treatment of the bottom-hole zone of the oil reservoir is as follows.

When the first rim of the aqueous acid solution is injected into the formation, the technological equipment and the bottom-hole zone of the formation are flushed from inorganic salts and iron compounds. Such treatment allows avoiding the mudding of the oil reservoir by resins, reaction products of oil with acid in the presence of iron ions. Next, the rim of the emulsion is pumped, which, due to the increased viscosity, blocks the washed zones and slows down the reaction rate with the formation rock. The newly injected aqueous acid solution enters the zones with low permeability, due to the interaction with the formation rock it increases their permeability. With further injection of the emulsion, again the newly formed highly permeable zones are blocked, due to the delayed reaction with the rock, the emulsion penetrates deep into the formation and, thus, the formation coverage increases.

The total volume of the emulsion for treating the formation is determined based on the power of the treated formation, the radius of treatment, porosity and the coefficient of oil saturation of the formation according to the following formula: Q = π * R ² * H * m * Kн,

where: Q is the volume of the prepared emulsion, m ³ ;

π = 3.14;

R is the radius of processing, m;

N - power of the treated formation, m;

m is the porosity,%;

Kн - the coefficient of oil saturation of the reservoir. Sequentially-alternating processing is carried out in 1-5 cycles.

Evaluation of the effectiveness of emulsions is checked in laboratory conditions to determine the viscosity, dissolution rate of marble, clay, and to check the stability of emulsions over time at a temperature of 60 ° C. The research results are shown in table 1.

To determine the stability of the emulsion over time, 100 ml of the emulsion is poured into a graduated tube with a stopper, placed in a thermostat at

temperature 60 ° C and note the time of complete separation of the organic and acid phases.

The viscosity of the emulsion is determined on a Fann-35 rotational viscometer. Measurements are carried out at different spindle speeds. A change in viscosity of 15-20% within 6 hours is allowed. The measurement results are recorded indicating the brand of the device, the type of spindle used, rotation speed and temperature. Table 1 shows the viscosity values obtained on the Fann-35 device at room temperature and a spindle speed of 300 rpm, which corresponds to a shear rate of 511 s ^-1 .

The dissolution rate of carbonates (marble) is evaluated by the following method. A square cube of marble is weighed up to the second sign using linear dimensions to calculate the cube volume and density. The average density of marble used is 2.5 g / cm ³ . A marble cube suspended on a thread is lowered into the test composition and, at regular intervals (10-30 seconds), is removed, washed with water, dried and weighed. A table with the parameters of the relative time of dissolution of the cube and the absolute mass values is drawn up. Using the least squares method, the dissolution rate (g / s) in this experiment is found from the angle of inclination of a straight line on a linear interval. The absolute value of the dissolution rate (g / m ² * sec) is found as the slope of the straight line, calculated in coordinates (m / S) versus time, where m is the mass of the cube at certain time intervals, S is the area calculated by the equation:

S = 6 (m / p) 2/3.

The dissolution rate of clay is evaluated by the following method. A weighed portion of bentonite clay weighing 2 g is mixed with 20 g of the proposed acid composition and incubated for 18 hours. Next, the solution is filtered through a filter with a known mass, washed with water and dried at room temperature to constant mass and weighed on the filter. The dissolution efficiency is calculated by the formula:

E = 100 * (M-m) / Mo, where:

M is the mass of the original clay with a filter after processing, g;

Mo is the initial clay mass, g;

m is the mass of the filter, g

According to the results shown in table 1 it is seen that used in the inventive method, the emulsion has a high viscosity, is more stable. A decrease in the rate of dissolution of the formation rock increases the penetrating ability of the composition deep into the formation.

To determine the effectiveness of the emulsion when it is used to treat the formation, the corrosion rate and washing efficiency are determined. The test results are shown in table 2.

table 2 №№ p.p The composition number from table 1 The corrosion rate, g / m ² * h Washing efficiency,% one No. 1 0.29 83 2 Number 12 0.22 76 3 prototype HCl - 7.38 0.35 45 Soncor-9601 - 0.2 DT - 26.0

Corrosion activity is checked by standard methods on metal plates (steel 3) at room temperature.

A plate of size 10 * 15 * 3 is cleaned, washed in warm water, degreased with acetone or alcohol, and dried to constant weight. The plate is suspended on a nylon filament in a glass so that when the glass is filled with an acid solution, the end face of the plate is approximately 10 mm below the liquid level. The glass is filled with an acidic composition and left for a fixed time. After a predetermined time, the plate is removed from the acid, washed thoroughly in running water and rinsed repeatedly with hot distilled water. Moisture is removed from the surface of the plate with filter paper and the plate is dried to constant weight.

The corrosion rate is calculated by the formula:

V = g / 10 ^-4 * S * t,

where: V is the corrosion rate, g / m ² * hour;

g is the mass loss of the plate as a result of corrosion, g;

S - plate surface, m2;

t is the duration of the test, hours.

Determination of washing efficiency is carried out under dynamic conditions, for which samples of asphalt-resin-paraffin deposits (ASPO) weighing 2 g are placed in stainless steel baskets and suspended on a wire in an emulsion prepared in advance in a 250 ml plastic bottle. Mix the contents of the bottles on a magnetic stirrer at a speed of 400 rpm for 2 hours at room temperature. At the lapse of time, the samples are taken out, rinsed with water, dried in air and weighed. Washing efficiency is defined as the ratio of the loss in mass of the sample to its initial weight in percent.

When comparing the results obtained, it is seen that the proposed emulsion has a higher detergent efficiency of ARPD compared with the prototype, has a low corrosion activity

To study the influence of the proposed method on changing the filtration characteristics of a porous medium, reservoir models are used, which are paired metal tubes 50 cm long and 3 cm in diameter with different permeabilities. Ground quartz sand in pure water and with the addition of% calcium carbonate is used as the starting material for creating a porous medium. Mineralized water with a salt content of 19 g / l degassed oil diluted with kerosene to 4 mPa.s is used as saturating fluids. The reservoir model is saturated with water in an amount of 2 pore volumes, then it is displaced with oil, after which an aqueous acid solution is pumped, and then an emulsion is then displaced with oil. In another embodiment, after pumping the oil, it is displaced by water, then an aqueous acid solution and the inventive emulsion are pumped, which are also displaced by water. The change in filtration resistance is calculated by the formula:

, где $$Q=\frac{\left(K_{\mathrm{one}}\left(\mathrm{at},n\right)-K_2\left(\mathrm{at},n\right)\right)}{{\mathrm{TO}}_{\mathrm{one}}\left(\mathrm{at},n\right)}*\mathrm{one\; hundred}\%$$

where

K ₁ (c, n) and K ₂ (c, n) - oil and water permeability of the model before and after injection of an aqueous solution of acid and emulsion, μm ² .

Table 3 №№ p.p Reagents Injected Processing cycles
current Reagent volume Permeability, μm ² Change in filtration resistance,% Initial After processing one 1.10% HCl one 0.5 bp Runway 1.5 Runway 0.9 -40 0.2 bp NPP 0.6 NPP 0.63 + -5 2. Emulsion No. 10 from table 1 2 1.10% HCl + 2% HF 3 0.05 bp Runway 1.5 Runway 0.37 -75.3 NPP 0.6  NPP 0.7 +16.6 2. Emulsion No. 10 from table 1 3 prototype Clay acid - 6.9 one 0.3 bp Runway 1.5 Runway 1.65 +10 NPP 0.6 NPP 0.62 +33.3 Soncor -9601 - 5.0 DT - 26.0

Thus, the proposed method for treating the bottom-hole formation zone allows to efficiently develop heterogeneous permeability oil reservoirs by increasing the permeability of oil-saturated and temporarily blocking highly permeable water-saturated interlayers, leading to an increase in the coverage of the formation by exposure.

Claims (3)

1. The method of processing the bottom-hole zone of the formation, which includes injecting an emulsion and an aqueous acid solution into the formation, characterized in that the aqueous acid solution is first pumped, and the aqueous acid solution and the emulsion are injected in a sequentially alternating mode, and an emulsion of the following composition is used as an emulsion, wt.%:
Acid 5.0-40.0 Anionic, or nonionic, or cationic surfactant or their mixture 1.0-10.0 Hydrocarbon solvent 5.0-40.0 Primary or secondary alcohol or their mixture 0.1-5.0 Corrosion inhibitor 0.01-0.05 Water Rest 2. The method according to claim 1, characterized in that the emulsion further comprises a viscosity regulator in an amount of 0.01-6.0 wt.%. 3. The method according to claim 1, characterized in that the aqueous acid solution is used in a 3.0-24.0% concentration.