RU2732900C1 - Composition for inhibiting hydrate formation - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: invention relates to oil and gas industry, namely to prevention of formation of solid hydrate deposits in oil and gas wells, specifically to a thermodynamic hydrate inhibitor – THI, varying thermobaric conditions of formation of clathrate compounds of water and natural gas. Composition for inhibiting hydration based on aqueous solution of methanol and additive, as an additive contains ethanol ammonium formate, with the following ratio of components, wt% in terms of pure substance: ethanol ammonium formate 0.25–1.25, methanol 1.13–5.63, water – the rest.EFFECT: low temperature of hydration with simultaneous reduction of corrosion aggressiveness of composition and prevention of loss of salts from associated produced waters.1 cl, 5 ex, 4 tbl

Description

The claimed invention relates to the oil and gas industry, namely, to prevent the formation of solid hydrate deposits in oil and gas wells, specifically, to a thermodynamic inhibitor of hydrate formation (TIG), which changes the thermobaric conditions for the formation of clathrate compounds of water and natural gas.

Known composition for preventing hydrate formation in the form of pure methanol (WFD 39-1.13-051-2001. Instructions for rationing the consumption and calculation of methanol emissions for the facilities of JSC "Gazprom"). However, its use does not ensure the removal of the liquid accumulated at the bottom of a gas well; moreover, the use of methanol often leads to the salting-out of alkali metal chlorides from the produced (formation) water, which complicates the processes of oil and gas production with the formation of solid salt sediments.

, где R1-R5 -углеводородные радикалы, содержащие двойные связи и первичные аминогруппы. Одновременно предотвращается гидратообразование и коррозия при применении 15%-ного раствора комплексного ингибитора в воде. (А.с. СССР №314822 C23F 11/16, опуб. 21.09.1971.) Недостатком известного состава является высокая токсичность пиридиновых соединений, которые растворяясь в водной среде способствуют ее подщелачиванию и риску выпадения малорастворимых солей карбонатов щелочноземельных металлов.A known composition for preventing the formation of hydrates in wellbores in the presence of hydrogen sulfide, including methanol with the addition of up to 4% pyridine homologues

, where R1-R5 are hydrocarbon radicals containing double bonds and primary amino groups. At the same time, hydrate formation and corrosion are prevented when using a 15% solution of a complex inhibitor in water. (USSR Certificate of Authorship No. 314822 C23F 11/16, publ. 09.21.1971.) The disadvantage of the known composition is the high toxicity of pyridine compounds, which dissolve in the aquatic environment contribute to its alkalinization and the risk of precipitation of poorly soluble salts of alkaline earth metal carbonates.

The closest in essence and the achieved effect (prototype) is the composition of complex action for treating the bottomhole zone of a gas well, including a 70% aqueous solution of methanol and a mixture of surfactants - surfactants: nonionic - OP-10 and anionic - sulfonol (RF patent No. 2456326, IPC S09KS8 / 584, publ. 20.07.2012.) The disadvantage of the known composition is its increased corrosiveness due to washing away of the formed film of corrosion products from the metal surface and acceleration of electrochemical corrosion processes.

The task is to create an effective composition that provides a decrease in the temperature of hydrate formation while simultaneously reducing the corrosiveness of the composition and preventing the precipitation of salts from the produced (reservoir) waters due to their salting out.

The problem is solved by a composition for inhibiting hydrate formation based on an aqueous solution of methanol and an additive, which, according to the invention, contains ethanolammonium formate as an additive, with the following ratio of components, wt%. in terms of pure substance:

Ethanolammonium formate 0.25-1.25 Methanol 1.13-5.63 Water rest

It is known that substances that change the crystal structure of ice have an inhibitory effect; as a rule, these substances belong to the group of thermodynamic inhibitors of hydrate formation, i.e. they change the thermobaric conditions for the formation of clathrate compounds of water with natural gases. Among these substances, alcohols and glycols (polyhydric alcohols) have found industrial application. Substances that alter the crystal structure of ice can also include salts of formic acid (formates), which are widely used as a low-temperature additive for the preparation, for example, of technological solutions for well killing and anti-icing agents. At the same time, the use of ethanolammonium formate to inhibit hydrate formation is unknown.

We prepared ethanolammonium formate in one stage in situ without isolating the target product and preparative (commercial) forms of hydrate inhibitors with the addition of ethanolammonium formate.

Description of the synthesis of the reagent.

Synthesis reagents:

Formic acid. GOST 5848-73. Chemical formula CH ₂ O ₂ . Appearance - colorless transparent liquid with a pungent odor. Density - 1219 kg / m ³ . The boiling point is 101 ° C. The content of the basic substance is not less than 85.1% of the mass.

Monoethanolamine technical superior grade according to TU 2423-159-00203335-2004. Appearance - clear, colorless liquid. Density at 20 ° С - 1012 kg / m ³ . Mass fraction of monoethanolamine - not less than 98.8%. Mass fraction of diethanolamine - no more than 0.6%. Mass fraction of water - no more than 0.6%.

The synthesis of ethanolammonium formate was carried out by mixing in an equimolar ratio of monoethanolamine and formic acid:

HOCH ₂ CH ₂ NH ₂ + HOOCH → HOCH ₂ CH ₂ NH ₃ ⁺ ⋅ ^- OOCH

In a 500 ml three-necked flask equipped with a magnetic stirrer, reflux condenser, dropping funnel and thermometer, 1 mol of monoethanolamine (60.4 ml) was placed, then 60 ml of water was added with constant stirring. Fresh water was used as water. To the resulting aqueous solution, 37.7 ml (1 mol) of formic acid was poured dropwise over 40 minutes using a dropping funnel. Received 167 g of a solution with a density of 1061 kg / m ³ . The amount of ethanolammonium formate salt HOCH ₂ CH ₂ NH ₃ ⁺ ⋅ ^- OOCH 107.1 g - theoretical yield.

From the resulting mixture, 5, 10, and 15% solutions of ethanolammonium formate in aqueous methanol (50% by weight solution) were prepared. In view of the identity of the preparation of all the listed solutions, further examples are given for 10% of the concentration of the inhibitor obtained in aqueous methanol.

The method for determining the inhibitory effect consisted in comparing the inhibiting effect of ethanolammonium formate in a water-methanol mixture and methanol.

A mixture of natural gases was used as a gas-hydrate-forming model medium (Table 1). The composition of the model gas mixture was determined using a Kristall 5000.2 gas chromatograph (Chromatek) according to GOST 31371-2008 (ISO 6974).

10 ml of fresh water was placed in a high-pressure cell of the Thermo company for rheological studies with a free volume of 51 ml, and a model mixture of hydrocarbon gases was pumped into the cell using an oil pump to a pressure of 120 ± 1.5 atm at a temperature of 40 ° C. To register temperature and pressure, a temperature sensor and a pressure sensor were additionally installed in the cell. The temperature and pressure sensors were calibrated with a Fluke 1524 reference thermometer and a Fluke 700G30 reference pressure gauge prior to testing. The high pressure cell can be thermostated in the temperature range from minus 15 to plus 90 ° C. All measured parameters were monitored and recorded using a personal computer and LabVIEW software package.

After filling with water and gas, the cell was placed into a MARS rheometer (Naake, Germany). Under conditions of constant shear rate (γ = 34.4 s ^-1 ), the shear stress τ and viscosity with decreasing temperature were recorded.

The initial temperature in all experiments was 40 ° C, then the temperature was reduced to minus 2 ° C. Every 3 degrees, the cell was kept at a given temperature for 60 minutes, then the rheological parameters and pressure were recorded for 300 s. An increase in viscosity or shear stress with decreasing temperature indicated the formation of hydrates or condensation of the gas mixture.

In the presence of an inhibitor of hydrate formation in water under conditions of decreasing temperature, a shift in the conditions for the formation of gas hydrates is observed, namely, a shift in temperature to the region of lower values.

Taking into account the fact that the pressure in the cell will change with decreasing temperature, approximately following the law:

where P _x , P ₀ - initial and current pressure, at;

T ₀ , T _x - initial and current temperature, K,

then, accordingly, it is necessary to fix both the temperature and the pressure of the beginning of hydrate formation.

A preliminary experiment was carried out with methanol as an inhibitor of hydrate formation. Basic comparative experiment conditions:

The inhibitor is methanol, the amount of fresh water is 9 g, the dosage of the methanol inhibitor is 1 g (10% by weight solution). The amount of gas is 4.8 liters at standard conditions. The initial temperature was 40 ° C, the initial pressure was 120 atm, and the temperature of hydrate formation of the system was 12.3 ° C.

Next, an experiment was carried out using the obtained hydrate formation inhibitor containing ethanolammonium formate.

Example 1.

To 9 g of fresh water was added 1 g of the commercial form of the inhibitor containing 10% ethanolammonium formate in 50% water-methanol mixture. Gas of the composition (table 1) was injected into the cell in the amount of 4.8 liters at standard conditions. The initial temperature of the experiment was 40 ° C, the initial pressure was 120 atm. In the process of decreasing the temperature in the cell, an increase in the viscosity of the medium was noted at a temperature of hydrate formation of 10.2 ° C.

Example 2.

To 8.75 g of fresh water was added 1.25 g of the commercial form of the inhibitor, containing 10% ethanolammonium formate in 50% water-methanol mixture. Gas of the composition (table 1) was injected into the cell in the amount of 4.8 liters at standard conditions. The initial temperature of the experiment was 40 ° C, the initial pressure was 120 atm. In the process of decreasing the temperature in the cell, an increase in the viscosity of the medium was noted at a temperature of hydrate formation of 10.1 ° C.

Example 3.

To 9.25 g of fresh water added 0.75 g of the commercial form of the inhibitor containing 10% ethanolammonium formate in 50% water-methanol mixture. Gas of the composition (table 1) was injected into the cell in the amount of 4.8 liters at standard conditions. The initial temperature of the experiment was 40 ° C, the initial pressure was 120 atm. In the process of decreasing the temperature in the cell, an increase in the viscosity of the medium was noted at a temperature of hydrate formation of 10.4 ° C.

Example 4.

To 9.5 g of fresh water added 0.5 g of the commercial form of the inhibitor, containing 10% ethanolammonium formate in 50% water-methanol mixture. Gas of the composition (table 1) was injected into the cell in the amount of 4.8 liters at standard conditions. The initial temperature of the experiment was 40 ° C, the initial pressure was 120 atm. In the process of decreasing the temperature in the cell, an increase in the viscosity of the medium was noted at a temperature of hydrate formation of 10.9 ° C.

Example 5.

To 9.75 g of fresh water added 0.25 g of the commercial form of the inhibitor, containing 10% ethanolammonium formate in 50% water-methanol mixture. Gas of the composition (table 1) was injected into the cell in the amount of 4.8 liters at standard conditions. The initial temperature of the experiment was 40 ° C, the initial pressure was 120 atm. In the process of decreasing the temperature in the cell, an increase in the viscosity of the medium was noted at a temperature of hydrate formation of 11.3 ° C.

The experimental results are summarized in Table 2.

From the data obtained, we see a decrease in the temperature of hydrate formation by 1-2.2 ° C in comparison with methanol, which confirms the presence of a positive effect from the use of the developed composition. It should also be noted that the comparison was carried out with a simultaneous decrease in the total methanol content by 4.3-8.8% relative to the baseline experiment, which indicates a significant contribution of ethanolammonium formate in preventing hydrate formation.

The corrosiveness of the obtained hydrate inhibitor was investigated. Determination of the corrosiveness of the inhibitor was carried out according to the methods according to GOST R 9.905-2007, GOST 9.906-87.

Corrosion aggressiveness was assessed by the gravimetric method by changing the mass of samples made of carbon steel St3. The tests were carried out in cells installed in a water bath at a temperature of 20 ° C. The test duration was assumed to be 24 hours without stirring. Immediately after the tests, the samples were visually inspected: the presence of small corrosion symptoms was determined.

The samples are weighed and the corrosion rate calculated using the equation

where m ₁ is the mass of the sample before testing, g;

m ₂ is the mass of the sample after testing, g;

S is the area of the sample, m ² ;

τ - test time, h.

The corrosion rate of the obtained 10% solution of hydrate inhibitor at 20 ° C was 0.024 g / (m ² ⋅ hour) or 0.026 mm / year, which indicates that the commercial form of the inhibitor is a slightly corrosively corrosive liquid [1].

The salting-out ability of the inhibitor was evaluated by mixing the commercial form of the reagent and saline formation water of the composition shown in Table 3.

The experiments were carried out by mixing the model of formation water and the commercial form of the inhibitor at a temperature of 40 ° C and the content of the inhibitor in the formation water 5, 10, 15, 20, 25% of the mass.

The mixtures were kept for 4 hours with thermostating in a drying oven. The presence of turbidity or sediment, stratification in the resulting solutions was visually recorded. The experimental results are presented in table 4.

The compatibility of the commercial form of the inhibitor of hydrate formation with saline formation water has been established.

Thus, the developed inhibitor of hydrate formation, containing ethanolammonium formate, shows a higher efficiency of inhibition of hydrate formation as compared to methanol. In terms of physical and chemical properties, the developed inhibitor is a single-phase colorless transparent liquid with a low pour point (below minus 55 ° C) and low corrosiveness (0.026 mm / year), which does not salting out salts from saline formation waters. In terms of the inhibition efficiency, in comparison with 100% methanol at the same concentrations in fresh water, a decrease in the temperature of hydrate formation by more than 2 ° C is provided.

1. RD 39-0147103-362-86. Guidelines for the use of anti-corrosion measures in the preparation of projects for the development and reconstruction of oil field facilities. - Ufa: VNIISPTneft, 1987

Claims (2)

A composition for inhibiting hydrate formation, based on an aqueous solution of methanol and an additive, characterized in that it contains ethanolammonium formate as an additive, with the following ratio of components, wt%, based on the pure substance: ethanolammonium formate 0.25-1.25 methanol 1.13-5.63 water rest