RU2685605C1 - Acid composition for treatment of bottomhole formation zone of heterogeneous carbonate reservoirs - Google Patents

Abstract

FIELD: oil industry.SUBSTANCE: acid composition for treatment of bottomhole formation zone of heterogeneous carbonate reservoirs contains, wt. %: hydrochloric acid 15–25; emulsifier NF-15 0.4–1; Iran light oil 10–20; corrosion inhibitor ICU-118 0.04–0.1; water - balance.EFFECT: technical result is equal efficiency of action on all opened productive horizons with significant difference in filtration-capacitance properties.1 cl, 3 tbl

Description

The invention relates to the oil industry, in particular, compositions for acid treatment of the bottomhole formation zone of heterogeneous carbonate reservoirs.

Known acid composition for the treatment of low-permeable terrigenous reservoirs with high carbonate content and method of acid treatment of the bottomhole formation zone with its use (patent RU №2407769, publ. 12/27/2010) for acid treatment of the bottomhole zone of terrigenous and carbonate reservoirs containing 24% hydrochloric acid solution or ammonium chloride (1–5%), a solution of hydrofluoric acid, 50% concentration or ammonium fluoride or ammonium bifluoride (1–5%), alkyl benzene sulfonic acid (10–30%) and glycol (10–40%).

The disadvantages of this composition are its low efficiency in the processing of carbonate reservoirs at temperatures in the range from 50 ° C to 70 ° C.

Known surfactant acid composition for the treatment of carbonate reservoirs (patent RU No. 2494136, publ. 07.03.2012) for acid treatment of the bottomhole formation zone of carbonate reservoirs to increase the intensification of oil production, containing hydrochloric acid (6-24%), alcohol-containing compound ( 5-30%), indicated by TMS "ZheniLen" (0.5-2%), indicated cationic surfactant (0.2-1%), iron stabilizer (0.5-3%) and water (the rest).

The disadvantage of this composition is the postoperative deterioration of the filtration-capacitive properties of carbonate reservoirs under reservoir conditions.

Known composition for acid treatment of the bottomhole formation zone and method of acid treatment of the bottomhole formation zone (patent RU No. 2545582, publ. 04.04.2015) for acid treatment of the bottomhole formation zone in order to increase the injectivity of injection wells and intensify the flow of fluid from the reservoir with carbonate reservoirs, containing hydrochloric acid (10-20%), anionic surfactants, nonionic surfactants, surfactants or their mixtures (0.4-3%), Athos 300M (0.01-15%), solvent (5-25%) and water (the rest) .

The disadvantage of this composition is the short period of reaction of the acid with the rock due to its rapid neutralization.

Known acid composition for processing low-permeability high-temperature formations with a high content of clays and carbonates (RU patent No. 2616949, publ. 04.04.2017) adopted as a prototype for acid treatment of the bottomhole formation zone with high carbonate content (with carbonate content of 5% or more), complicated by high reservoir temperatures up to 105 ° C, low permeability values, as well as a high content of clays adopted for the prototype, containing hydrochloric acid (4-6%), organic acid (5-8%), corrosion inhibitor (0.1-0.5 %), surfactant in substance (0.1-0.5%), iron stabilizer (09.75-2%) and water (the rest).

The disadvantage of this composition is damage to the reservoir due to the loss of inorganic and organic deposits, high dissolution rate and low amount of dissolved carbonate at low temperatures (50-70 ° C).

The technical result is to obtain a composition for acid treatment in the bottomhole formation zone, which is optimized experimentally by the process of acid deviation in the target interval of the well, which opens several interlayers with a significant difference in reservoir properties, so that the acid treatment equally effectively affects all productive horizons.

The technical result is achieved by the fact that the composition additionally contains an Iranian NF-15 emulsifier and Iranian light oil with the following ratio of components, wt.%:

hydrochloric acid 15-25 emulsifier NF-15 0.4-1 Iran light oil 10-20 corrosion inhibitor "IKU-118" 0.04-0.1 water rest

Acid composition for treatment of the bottomhole formation zone of heterogeneous carbonate reservoirs includes the following reagents and commercial products containing them:

- hydrochloric acid 15-25%, produced according to GOST 857-95

- corrosion inhibitor "IKU-118" 0.1-0.5%, is a glycol solution;

- oil, Iran light 10-20%;

- emulsifier NF-15 0.4-1% (manufactured by Polawax or Sabowax);

- fresh water - the rest.

Emulsified acid with increased viscosity increases the coverage of the treated zones and increases the achievable depth of the resulting wormholes due to the reduced reaction rate with the rock.

The effectiveness of the proposed structure is proved by laboratory tests. For research were used:

- technical synthetic acid, containing 36% of the mass. HCL, produced according to GOST 857-95;

- corrosion inhibitor "IKU-118", is a glycol solution;

- Iran light oil https://atdmco.com/lub/crude-oil.html;

- emulsifier NF-15 is a water-repellent self-emulsifying system of plant origin, obtained from palm oil https://shampunka.ru/emulsionnyy-vosk-polavax-nf-polavaks--emulgator-naturalnyy-rastitelnyy/

- water.

Example 1 (prototype, composition No. 1 in table 1). In a glass with a volume of 250 ml in 87.4 ml of water dissolve 4.0 g of hydrochloric acid, 6.0 g of formic acid, 1.5 g of the HI-IRON iron stabilizer, 1.0 g of the surfactant Neftenol-VVD, 0.1 g of corrosion inhibitor "IKU-118".

After mixing, the composition is obtained with the following content of ingredients, mass. %: hydrochloric acid - 4.0; formic acid - 6.0; corrosion inhibitor "IKU-118" - 0.1; surfactant "Neftenol-VVD" - 1.0; iron stabilizer "HI-IRON" - 1.5; water - 87.4.

Example 2. In a glass with a volume of 250 ml in 73.33 ml of water dissolve 15.0 g of hydrochloric acid, 11.0 g of oil, 0.6 g of emulsifier NF-15, 0.07 g of corrosion inhibitor IKU-118.

After mixing, the composition is obtained with the following content of ingredients, mass. %: hydrochloric acid - 15.0; oil - 11.0; corrosion inhibitor "IKU-118" - 0.07; emulsifier NF-15 - 0.6; water - 73.33.

Example 3. In a glass with a volume of 250 ml in 60.91 ml of water dissolve 23.0 g of hydrochloric acid, 15.0 g of oil, 1.0 g of emulsifier NF-15, 0.09 g of corrosion inhibitor IKU-118.

After mixing, the composition is obtained with the following content of ingredients, mass. %: hydrochloric acid - 23.0; oil - 15.0; corrosion inhibitor "IKU-118" - 0.09; emulsifier NF-15 - 1.0; water - 60.91.

Example 4. In a glass with a volume of 250 ml in 62.16 ml of water dissolve 20.0 g of hydrochloric acid, 17.0 g of oil, 0.8 g of emulsifier NF-15, 0.04 g of corrosion inhibitor IKU-118.

After mixing, the composition is obtained with the following content of ingredients, mass. %: hydrochloric acid - 20.0; oil - 17.0; corrosion inhibitor "IKU-118" - 0.04; emulsifier NF-15 - 0.8; water - 62.16.

The content of components in acidic compositions are presented in table 1.

When conducting tests to determine the rate of dissolution of carbonates used marble disks, the surface area of these disks is calculated by the formula 1.

where, S is the surface area of the marble disk, m ² ;

r is the radius of the disk, m ² ;

h - disk height, m ² .

After measuring the basic geometrical parameters of the disks, they are washed with water and dried in a heating cabinet to constant weight, the last stage of preparation of the disks is their cooling in a desiccator for 2 hours.

At the same time, filters are prepared, which also undergo the drying procedure in a heating cabinet to constant weight, and then cooled in a desiccator for 2 hours.

After preparation, the disks are weighed on laboratory scales with an accuracy of 0.0001 g. Then 6 containers are taken and the acid composition is poured into them in a volume 2.5 times larger than the surface area of the disks, which are used in the research process. Jars with acidic composition are placed in a heating cabinet with a set temperature for 30 minutes, to warm the acidic composition to the temperature of the experiment. Then a marble disk is placed in each of the jars, and the sample with the disk is kept at a given temperature of 5, 15, 30, 60, 120 and 180 minutes, respectively.

The disc, which was kept in a solution of acid composition, is removed from the jar and washed with 0.5 N sodium hydroxide solution and water, dried in a heating cabinet to constant weight, then cooled in a desiccator for 2 hours. The disk is weighed, determining the mass loss of the disk according to the formula 2.

где, Δm - потеря массы диска, г;

where, Δm is the mass loss of the disk, g;

m ₁ is the mass of the disk before the experiment, g;

m ₂ is the mass of the disk after the experiment, g;

Then, the amount of dissolved carbonate and the dissolution rate of carbonate in the acid composition are calculated using formulas 3 and 4. After that, the dependences of the dissolution rate and the amount of dissolved carbonate are plotted on time.

where, P is the amount of dissolved carbonate,%;

m ₁ is the mass of the disk before the experiment, g;

m ₂ is the mass of the disk after the experiment, g;

where, t is the time of the experiment, h;

V is the dissolution rate, g / (m ² ⋅h)

In this work, a corrosion inhibitor, marketed under the brand name "IKU-118", was used for research. The studies were carried out using the conventional gravimetric method, namely, the loss of mass of steel plates after the removal of corrosion products was determined.

Steel plates are cleaned with fine-grained sanding paper, the geometric dimensions are measured and their area is determined, rubbed with alcohol to remove dirt and greasy stains, wrapped with filter paper and dried in a cupboard at 30-40 ° C for 15 minutes. Then the plates are weighed on an analytical balance with an accuracy of 0.0001 g and lowered into the studied acid formulations on special non-corroding suspensions. For each acid composition, two parallel experiments are carried out. The amount of acid composition required for the experiment is taken to be 100 ml. After the steel plates are lowered into the studied acid composition, they are left in it for a period of 8 hours at a reservoir temperature (60 ° C). After a specified time, the plates are removed, washed with water, rubbed with alcohol, filter paper, dried in a drying cabinet for 15 minutes, then weighed the same way to the accuracy of 0.0001 g.

The corrosion rate is determined by the formula:

where: g ₁ is the mass of the plate before the experiment, g;

g ₂ is the mass of the plate after the experiment, g;

A - plate area, m ² ;

t - time, h;

V _cor - corrosion rate, g / m ² ⋅hour.

A rheological test was also carried out, which consists of four stages. Testing the rheological properties of the emulsion under surface conditions; Pumping the emulsion through the collector (tube);

The passage of the emulsion from the reservoir to the carbonate reservoir followed by its dissolution (at this stage calcium carbonate was gradually added to the emulsion);

Pumping the emulsion from the collector system (tube) -plast.

At the third and fourth stages, the acid interacts with the rock, which imitates the behavior of the emulsion during acid treatment, in particular, it is possible to trace the change in its viscosity.

The optimal emulsified acid composition was developed and tested in two steps:

1) Development of the component and chemical composition;

2) Conducting filtration studies on core to check the real properties of the developed acid composition.

The development of the component and chemical composition included:

1) Test more than 20 emulsifiers using the method of determining the interfacial tension to obtain an emulsion with the desired viscosity and stability.

2) Conduct rheological studies of the emulsion under 4 different environmental conditions to simulate the flow from the wellhead to the bottom of the well.

The first step in the development of an emulsified acid composition is the selection of the optimal emulsifier and its working concentration in the composition of the emulsion. To find the optimal emulsifier that allows you to create an emulsion of the required level of viscosity and stability under the conditions of penetration into the pore medium and response with the reservoir rock, more than twenty different samples were tested. To find the most technically and economically effective concentration, interfacial tension tests were conducted. Among the emulsifiers considered, the most effective was an emulsifier with ester compounds, including solutions of oleic, linoleic, linolenic and resin acids.

The acid phase of the emulsion is prepared by mixing concentrated hydrochloric acid with water and a corrosion inhibitor. The oil phase of the emulsion is prepared by mixing the oil and emulsifier at high speeds. Then the acid phase is slowly added to the oil and stirred at high speed for 30 minutes. Further, to assess the quality of the prepared emulsion, its electrical conductivity is measured (should be approximately zero).

As can be seen from table 2, composition No. 3 has the lowest interfacial tension value. The value of the interfacial tension is

2.1 mN / m. When applying compounds 1, 2 and 4, this value is 5.9; 3.4 and 2.8 respectively. Thus, the composition number 3 reduces interfacial tension.

As shown in Table 2, the corrosion rate with compounds 1, 2, 3, and 4 is 0.56; 0.63; 0.56 and 0.71, respectively. Also from the table it can be seen that composition No. 3 has the highest amount of dissolved carbonate and the longest period of impact activity with the rock (for nearly 3 hours, composition No. 3 was active). In addition, among all the formulations considered, composition No. 3 has the lowest dissolution rate at 60 ° C.

For filtration studies, a core of carbonate reservoirs from Iran deposits was used.

Core parameters:

Core length - 4.0 cm

Core diameter - 3.00 cm

Initial porosity of core - 17.2%

The initial permeability of the core oil - 4.6 microns ²

Experimental conditions:

The temperature of the experiment - 60 ° C

Backpressure - 8.27 MPa,

Crimping pressure - 17,24 MPa

The results of filtration experiments are presented in table 3.

As follows from the data presented, composition No. 3 has the highest value of the multiplicity of increase in permeability. At the same time, the multiplicity of permeability increases is almost 102 times.

Claims (2)

Acid composition for treatment of the bottomhole formation zone of heterogeneous carbonate reservoirs containing hydrochloric acid, corrosion inhibitor "IKU-118" and water, characterized in that it additionally contains NF-15 emulsifier and Iran light oil with the following ratio of components, wt.%: hydrochloric acid 15-25 emulsifier NF-15 0.4-1 Oil İran light 10-20 corrosion inhibitor "IKU-118" 0.04-0.1 water rest