RU2307798C1 - Composition to inhibit salt deposition in oil production (variations) - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention relates to compositions aimed to prevent deposition of inorganic salts in wells and on well equipment, oil collection and transportation system, as well as in oil strata developed involving watering systems. Salt deposition inhibiting composition contains, wt %: oxyethylenediphosphonic acid 16.0-18.03, sodium hydroxide 5.83-7.0, zinc oxide 5.42-7.12, ethylene glycol 25.0-40.0, sodium lignosulfate 4.17-5.0, and water - the balance. In another embodiment, inhibiting composition oxyethylenediphosphonic acid 5.0-8.0, sodium hydroxide 5.83-7.0, zinc oxide 5.42-7.12, ethylene glycol 25.0-40.0, sodium lignosulfate 4.17-5.0, nitrilotrimethylphosphonic acid 6.67-9.0, and water - the balance.

EFFECT: achieved high-efficiency versatile protection effect, lack of corrosion activity, and lowered freezing temperature enabling us of composition cold climatic regions.

2 cl, 6 tbl

Description

The invention relates to the field of oil production, in particular to compositions designed to prevent the deposition of inorganic salts in wells and downhole equipment, a system for collecting and transporting oil, as well as in oil reservoirs developed using water flooding systems.

The oil production process is accompanied by the deposition of solid sediments of inorganic substances that accumulate in the bottom-hole zone of the reservoir of production wells, on the walls of the production casing and elevator pipes, in pumping equipment and on-ground communications of oil collection and treatment systems. The main source of salt release is water produced in conjunction with oil. Well deposition is affected by wells and ground equipment operating in conditions of flooding of produced products.

The precipitation of a chemical substance from a solution occurs if the concentration of this substance or ion in the solution exceeds the equilibrium. The main causes of insoluble precipitation are: mixing of water of various compositions that are not compatible with each other, water supersaturation as a result of changes in thermobaric conditions in a well or pump, water evaporation, etc.

Inhibitory methods for protecting wells and equipment have received priority distribution to prevent scaling in oilfield practice.

Known composition for the prevention of carbonate, sulfate, iron oxide deposits, as well as the destruction of deposits of carbonate salts on heat and mass transfer surfaces (RU 2146232, C02F 5/14, publ. 2000.03.10). The composition contains, wt.%: Oxyethylene diphosphonic acid (HEDP) 15-40, zinc compound 0.1-7.0, sodium lignosulfonate 10-30 and water. In addition to effectively preventing the formation of salt deposits and inhibiting corrosion, the composition prevents the ion exchange of iron with the acid part of the reagent. The disadvantage of this known composition is the high freezing temperature, and therefore, the complexity of its use in regions of cold climate, as well as insufficiently high heat resistance.

The closest to the proposed technical solution for the totality of features is the composition (RU 2205157, С02F 5/14, publ. 2003.05.27 - prototype) containing hydroxyethylidene diphosphonic acid (OEDP), sodium hydroxide, zinc oxide and water in the following ratio of components, wt. %: HEDP 16.4-20.4, sodium hydroxide 6.5-8.3, zinc oxide 5.9-7.32, water - the rest. The disadvantage of this composition is also the high freezing temperature and the complexity of its use in regions of cold climate.

The problem to which the invention is directed is to create a composition that prevents the formation of insoluble salt deposits, which has a highly effective complex protective effect; synthesized based on raw materials available in industrial volume; non-corrosive and characterized by low freezing point for the possibility of its use in regions with a cold climate.

The problem is solved in that the proposed composition for inhibiting scaling during oil production (hereinafter the composition), containing hydroxyethylene diphosphonic acid (HEDP), sodium hydroxide, zinc oxide and water, additionally contains sodium lignosulfonate and ethylene glycol (EG) in the following ratio of components, wt. %:

OEDF 16.0-18.03

Sodium hydroxide 5.83 - 7.0

Zinc oxide 5.42-7.12

EG 25.0-40.0

Sodium lignosulfonate 4.17-5.0

water the rest.

In another embodiment, the task is solved in that the composition for inhibiting scaling contains hydroxyethylene diphosphonic acid (HEDP), sodium hydroxide, zinc oxide and water, ethylene glycol (EG), sodium lignosulfonate, nitrilotrimethylphosphonic acid (NTP) in the following ratio of components, wt.%:

OEDF 5.0-8.0

Sodium hydroxide 5.83-7.0

Zinc oxide 5.42-7.12

EG 25.0-40.0

Sodium lignosulfonate 4.17-5.0

NTF 6.67-9.0

Water is the rest.

The introduction of sodium lignosulfonate 4.17-5.0 wt.% And ethylene glycol 25.0-40.0 wt.% Allows you to get a composition that not only has a highly effective complex inhibitory effect of scaling, but also does not exhibit corrosive activity and is characterized by low temperature freezing for the possibility of its use in regions with a cold climate.

In addition, a variant of the composition for inhibition containing nitrilotrimethylphosphonic acid (NTP) in the amount of 6.67-9.0 wt.%, And HEDP in the amount of 5.0-8.0 wt.%. allows not only to reduce the content of expensive components (OEDF), but also to increase efficiency in relation to sulfate salts.

The following components were used to prepare the composition:

OEDF MA-TU 6-09-5372-87 - light beige powder, readily soluble in water; NTF - TU 6-09-5283-86 - white powder, readily soluble in water; zinc oxide - GOST 202-84 - a crystalline substance of white color; sodium hydroxide - TU 6-01-1306-85 - a crystalline substance in the form of white plates; EG-GOST 10164-75 - transparent liquid; Na lignosulfonate - TU 113-03-616-87 - fine brown powder and water.

The drawing shows a graph.

The inventive composition is prepared as follows: (all prescription quantities of the components are taken by weight). Two separate solutions are prepared.

Solution 1: The calculated amount of water and sodium hydroxide 5.83 - 7.0 wt.% Are fed into a heat-resistant vessel. Stir until the alkali is completely dissolved. Zinc oxide 5.42 - 7.12 wt.% Is fed into the resulting solution in small portions with constant stirring (stirring speed 300-450 rpm). Stirring is continued with heating at 60-70 ° C for 55-60 minutes. The result is a homogeneous suspension. Then, without stopping mixing and heating, OEDP 16.0-18.03 wt.% Is gradually fed in very small portions, and after 10-15 minutes of mixing, a light-brown solution close to transparent is obtained. As soon as such a solution is obtained, heating is stopped.

Solution 2: Ethylene glycol 25-40 wt.% Is fed into the vessel and then sodium lignosulfonate 4.17-5.0 wt.% Is fed in small portions with constant stirring. The result is a uniform dark brown solution.

Next, to solution 1, in small portions serves solution 2 with vigorous stirring (stirring speed 750-900 rpm ^-1 ). Stirring is continued for 1-1.5 hours. The resulting mixture is ready for use as intended.

In the case of the preparation of a composition containing NTF, the composition is prepared as follows.

Solution 1: The calculated amount of water and sodium hydroxide 5.83-7.0 wt.% Are fed into a heat-resistant vessel. Stir until the alkali is completely dissolved. Zinc oxide 5.42-7.12 wt.% Is fed into the resulting solution in small portions with constant stirring (stirring speed 300-450 rpm). Stirring is continued with heating at 60-70 ° C for 55-60 minutes. The result is a homogeneous suspension. Further, without stopping mixing and heating, OEDP 5.0-8.0 wt.% Is gradually and in very small portions fed, and NTF 6.67-9.0 wt.% Is introduced after 10-15 minutes. Stir until a clear, light brown solution is obtained. As soon as such a solution is obtained, heating is stopped.

Then, solution 2 is fed into solution 1 in small portions with vigorous stirring (stirring speed 750-900 rpm). Stirring is continued for 1-1.5 hours

Compositions with different component ratios are presented in table 1,

Table 1 The ratio of the starting components in the investigated compositions. Structure The content of components in the composition, wt.% OEDF NTF NaOH Zno Sodium Lignosulfonate EG Water BUT 16,0 - 7.0 6.5 5,0 40,0 25.5 AT 18.0 - 6.6 6.1 4.6 39.6 25.1 FROM 20,0 - 6.2 5.7 4.2 39.2 24.7 D 18.03 - 7.0 7.12 5,0 25.0 37.85 E 6.67 6.67 5.83 5.42 4.17 25.00 46.25 F 8.0 8.0 7.0 6.5 5,0 30,0 35.50 G 5,0 9.0 6.5 6.0 5,0 20,0 48.50

During laboratory tests, the following properties of the composition were determined: the effectiveness of the inhibitory effect in model waters of various compositions, the density of solutions, freezing temperature, and the corrosion rate in the presence of the proposed composition.

The effectiveness of inhibition of various types of scaling was determined chemically. For research were taken formulations with different contents of the components. The effectiveness of inhibition was evaluated by the effectiveness of their influence on salt formation in model waters of various compositions.

The composition of the model waters, on which the effectiveness of the inhibitory effect of the compositions was evaluated, is shown in Table 2. Each of the types of water given was prepared by mixing solution I with solution II.

table 2 The composition of model waters. Water The composition of solution I (per 0.5 l) The composition of solution II (0.5 l) salt m _salt , g salt m _salt , g Calcium Chlorine Water CaCl ₂ 3.33 NaHCO ₃ 0.28 MgCl ₂ · 6H ₂ O 0.42 NaCl 21,20 Sodium bicarbonate water CaCl ₂ 0.56 NaHCO ₃ 1.66 MgCl ₂ · 6H ₂ O 0.42 NaCl 22.59 Sulphate water Na ₂ SO ₄ 6.5 CaCl ₂ 13.6 NaCl 9,4 MgCl ₂ · 6H ₂ O 0.62 Barium water Na ₂ SO ₄ 0.4 BaCl ₂ · 2H ₂ O 0.56 NaCl fifteen NaCl fifteen

When using this method, the effectiveness of the action of the reagents is determined by the residual concentration of salt-forming ion in the treated and untreated reagent solution according to the formula:

where C _p , C _to and C ₀ - the concentration of salt-forming ion in solution with an inhibitor, without an inhibitor and in the source water with an initial concentration, respectively.

In this case, the supersaturated solution is heated to a certain temperature (85-90 ° C), followed by exposure for 4 hours.

The results of experiments to determine the effectiveness of the compositions for the four types of model waters are presented in table 3.

Table 3 The effectiveness of the inhibitory effect of the prepared compounds in model waters of various types. Structure C _Inh , mg / L Effectiveness,% Calcium Chlorine Water Sodium bicarbonate water Sulphate water Barium water BUT 10 96.3 92.0 89.8 80.0 twenty 93.8 96.7 94.4 80.0 fifty 93.8 93.3 94.4 81.8 one hundred 87.5 93.3 94.4 58.2 AT 10 95.0 94.7 65.3 69.1 twenty 90.0 97.4 91.4 70.9 fifty 90.0 97.4 79.1 72.7 one hundred 80.0 97.4 76.0 63.6 FROM 10 97.0 92.1 89.8 63.6 twenty 92.0 94.7 91.4 70.9 fifty 90.0 97.4 89.8 70.9 one hundred 75.0 97.4 89.8 70.9 D 10 96.0 90.8 71,4 50,0 twenty 95.4 98.5 78.6 75.0 fifty 86.0 98.5 92.6 85.0 one hundred 84.5 98.5 92.6 85.0 E 10 97.0 83,2 56.4 52.0 twenty 96.4 94.2 90.9 75.0 fifty 88.8 99.6 94.6 85.5 one hundred 87.5 99.6 94.6 85.5 F 10 98.57 96.67 55.20 50,0 twenty 98.57 98.33 93.83 75.00 fifty 92.86 98.33 95.67 87.50 one hundred 85.71 98.33 95.67 87.50 G 10 93.75 97.44 54.55 62.50 twenty 87.50 98.72 81.82 75.00 fifty 75.00 98.72 90.91 81.25 one hundred 68.75 98.72 92.73 81.25

As can be seen from the data in the table, the prepared compositions show a rather high efficiency in the case of all types of water, including against the formation of sulfate salts.

Thus, the proposed composition improves the efficiency of preventing deposits of inorganic salts during oil production due to the possibility of its use for various types of water.

To assess the corrosiveness of the composition associated with the possibility of its aggressive effect on the metal of dosing units, the aggressiveness of concentrated solutions of the proposed composition was tested and the effect of its working dosages was evaluated. A 10% inhibitor solution in distilled water was used.

The experiments were carried out in accordance with the following regulatory documents:

- GOST 9.502-82 - Unified system of protection against corrosion and aging. Metal corrosion inhibitors for water systems. Corrosion test methods;

- GOST 9.514 - 99 - Metal corrosion inhibitors for water systems. Electrochemical method for determining protective ability.

As the studied medium, we used a water model of the ionic composition characteristic of Western Siberia (Table 4). The partial pressure of carbon dioxide was 0.1 MPa, the concentration of dissolved oxygen was not more than 0.05 mg / l.

The corrosion rate of samples made of steel St 3 was determined by the polarization resistance method using a Monicor-2 corrosion meter, according to a two-electrode circuit. Corrosion rates were measured every 30 minutes.

Table 4 The ionic composition of the waters used in the experiments (mg / l) Mineralization is common Cl ^- NSO ₃ ^- Ca ²⁺ Mg ²⁺ Na ⁺ 30293 18066 520 1064 213 10302

The surface preparation of the electrodes of the polarization resistance sensors and the working electrodes of the cells for taking the polarization curves was carried out in accordance with the requirements of GOST 9.506 - 87 and GOST 9.514 - 99. The required amount of water model was placed in the cell, after which carbon dioxide was bubbled through the cells with a flow rate of 15-20 m ³ / h for 30-40 minutes After that, polarization resistance sensors and working electrodes were installed in the cells. The gas flow rate decreased to 2-4 m ³ / h and was maintained throughout the experiment. After 14 hours, the required amount of reagent was added to the cells to stabilize the corrosion rate. The drawing shows a graph of the dependence of the corrosion rate on the concentration of the reagent. It is seen that in the presence of the proposed composition there is a slight decrease in the corrosion rate. This indicates the absence of a negative effect of the reagent on the corrosion resistance of fishing equipment.

The results of the study of the physical properties of the inhibitors are presented in table 5.

Table 5 Some physical properties of the compounds. Structure Appearance pH T is _frozen. ° C ρ, g / cm ³ Solubility BUT Thick dark brown liquid 9.0 -42.5 ° C 1.31 Well soluble in water, insoluble in hydrocarbons AT 9.3 -42.0 ° C 1.32 FROM 9,4 -42.0 ° C 1.32 D 9.0 -42.0 ° C 1.30 E 9.0 -42.0 ° C 1.30 * The freezing temperatures of the samples were determined on a LIN-TECH instrument according to ASTM D 97

Thus, the proposed composition has a highly effective complex inhibitory effect, preventing the formation of insoluble salt sediments, does not exhibit corrosive activity and has a low freezing temperature, which allows it to be used in regions with a cold climate.

The proposed composition can be used to prevent the deposition of inorganic salts in wells and downhole equipment, a system for collecting and transporting oil, as well as in oil reservoirs developed using water flooding systems.

Claims (2)

1. The composition for inhibiting scaling, containing oxyethylene diphosphonic acid (HEDP), sodium hydroxide, zinc oxide and water, characterized in that it additionally contains ethylene glycol (EG) and sodium lignosulfonate in the following ratio, wt.%: OEDF  16,0-18,03 Sodium hydroxide  5.83-7.0 Zinc oxide  5.42-7.12 EG  25.0-40.0 Sodium Lignosulfonate  4.17-5.0 Water  rest 2. Composition for inhibiting scaling containing hydroxyethylene diphosphonic acid (HEDP), sodium hydroxide, zinc oxide and water, characterized in that it additionally contains ethylene glycol (EG), sodium lignosulfonate, nitrilotrimethylphosphonic acid (NTP) in the following ratio, wt.%. : OEDF  5.0-8.0 Sodium hydroxide  5.83-7.0 Zinc oxide  5.42-7.12 EG  25.0-40.0 Sodium Lignosulfonate  4.17-5.0 NTF  6.67-9.0 Water  rest

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