RU2245992C1 - Method for operation of object with hydrocarbon product under hydrate mode conditions - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: method includes transporting hydrocarbon product along operation channel. Control of pressure changes along this channel is performed. If such change is present such debit of hydrocarbon product is set, which provides for destruction or decomposition of present natural gas hydrates and/or prevention of their forming. With this debit, to place of hydrates decomposition and/or prevention of their forming, alkali solution is fed with concentration 0.04-4.9% with "pH" greater than 10. Alkali solution is fed during time not less than time of pressure change along operation channel, as well as with flow and during time until achieving mass concentration of alkali in gas phase 10-15% of mass.

EFFECT: higher efficiency.

12 cl, 1 dwg

Description

The present invention relates to the gas and oil industries and, in particular, to the operation of facilities with hydrocarbon products in these industries. Such objects may include, for example, gas and oil wells, gas, gas condensate, gas and oil, gas hydrate, oil and gas and any other types of deposits combining gas, oil and gas condensate, as well as various pipelines (for example, land, above-ground or buried) local values in the field development system and trunk pipelines. A feature of the objects of the invention is their operation under hydrated conditions, i.e. such a regime, which is the initial conditions of operation of the facility with existing gas hydrates or when, without observing special measures at the facility, the formation of gas hydrates is inevitable. Moreover, in accordance with the invention, operation in a mode providing for the destruction (decomposition) of existing natural gas hydrates and / or the prevention of their formation is considered.

In the development of most of the aforementioned hydrocarbon deposits, the problem arises of combating the formation of natural gas hydrates. Of particular importance is the issue in the development of deposits in Western Siberia and the Far North. Low reservoir temperatures and harsh climatic conditions in these areas create favorable conditions for the formation of gas hydrates not only in wells and gas pipelines, but also directly in productive formations.

Gas hydrates (natural gas hydrates) are an unstable physicochemical compound of water with hydrocarbons, which decomposes into gas and water with increasing temperature or lowering pressure. In appearance, it is a white crystalline mass, similar to ice or snow.

There is a method of operating an object with hydrocarbon products in a hydrated regime, according to which, during operation, an antihydrate composition containing metal chlorides is introduced into the flow of produced products [1].

The disadvantages of this method are the low anti-hydration ability of the composition, its high corrosivity, the possibility of precipitation when mixing the composition with formation highly mineralized water.

There is a method of operating an object with hydrocarbon products under hydrated conditions, according to which, during operation, an antihydrate composition is introduced into the flow of produced products in the form of a 70-80% aqueous diethylene glycol solution [2].

The disadvantage of this method is the high cost of the composition used.

A known method of operating an object with hydrocarbon products in a hydrated regime, according to which methanol is introduced into the flow of produced products during operation [3].

The main disadvantage of this method is that methanol has a high saturated vapor pressure, which leads to large losses during the operation of the facility. To further prevent hydrate formation, the introduction of fresh methanol is required, which sharply increases its total consumption and causes a huge expenditure of money. In addition, methanol is a strong poison. When applied, there is a danger of environmental pollution and poisoning of personnel involved in the operation of the facility.

There is a known method of operating an object with hydrocarbon products under hydrated conditions, according to which, during operation, a water-soluble polymer obtained from N-substituted polyacrylamide with the following structural formula is introduced into the flow of produced products:

where R ₁ is a hydrocarbon group from 1 to 10 carbon atoms;

R ₂ is a hydrogen atom or a hydrocarbon group from 1 to 10 carbon atoms;

n is the average number of repeating monomer units ranging from about 1 thousand to about 6 million [4].

A significant disadvantage of this method is the shortage of the above polyacrylamide and its high cost. There is a method of operating an object with hydrocarbon products under hydrated conditions, according to which sodium chloride, water and a solution of polyelectrolyte are introduced into the flow of produced products during operation in the following ratio of components, wt.%:

sodium chloride 22-24

polyelectrolyte 0.1-1.0

water rest

As the polyelectrolyte, hydrolyzed or partially hydrolyzed polyacrylamide is used.

The composition further comprises a corrosion inhibitor in an amount of 0.1-0.5 wt.%. Catapine is used as a corrosion inhibitor. Water can be preheated to a temperature above 35 ° C or to the temperature of the reservoir of an operating well [5].

In almost all of the above methods of operation, the physicochemical mechanism of destruction and prevention of the formation of gas hydrates consists in the donor abilities of the functional group of the inhibitor molecule.

There is a method of operating an object with hydrocarbon products in a hydrated regime, according to which, during operation, bottoms of epoxy resin production containing alkaline components as the most active components according to the Lewis theory are introduced into the flow of produced products [6].

Significant disadvantages of the method of operation using bottoms include:

multicomponent system and inconsistency of composition (a consequence of the type of production - its waste);

significant transportation costs for the reagent with a content of not more than 5.5% of the main substance and the inconvenience of handling it in regions with severe climatic conditions (contains a water base);

low inhibitory ability.

The technical result of the invention is to increase the efficiency of the method of operation by using means with more active properties for the destruction of gas hydrates and / or preventing their formation and the creation of conditions in which this tool provides a decomposition rate of hydrates that is several times higher than the rate of their formation while reducing the consumption of the product.

The required technical result is achieved by the fact that the method of operating an object with hydrocarbon products in a hydrated mode involves transporting hydrocarbon products along the production channel, monitoring pressure drops along the length of this channel and, if there is such a difference, establishing the flow rate of the hydrocarbon product or the regime of the object that ensures destruction ( decomposition) of existing natural gas hydrates and / or prevention of their formation, supply in this state of the object to the place of decomposition of the hyd of solutions and / or prevention of their formation, an aqueous alkali solution with a concentration of 0.04-4.9 wt.% at a pH of more than 10, while the alkali solution is supplied over a period of not less than the time the pressure drop exists along the length of the production channel, as well as flow rate and over time to achieve a mass concentration of alkali in the gas phase of 10-15 wt.%.

Moreover:

as an object with hydrocarbon production, a gas deposit or a gas condensate deposit, or a gas and oil deposit, or a gas hydrate deposit, or an oil and gas deposit, or an oil and gas condensate deposit;

as a production channel, a well channel or a filtration channel in a reservoir of a reservoir, or a channel in a field development system, or a main pipeline channel is adopted;

a filtration channel in the reservoir is created from an injection well of at least one to a producing well of at least one;

the filtration channel in the reservoir is created by fracturing or drilling a directional well with a horizontal wellbore of at least one, or with a horizontal wellbore and a branch from it of at least one;

caustic soda or salts of weak acids and strong bases are used to prepare the alkali solution;

an clay stabilizer is added to the alkali solution;

a coolant is supplied to the hydrate decomposition site and / or to prevent their formation;

steam or hot water or a thermogenerating liquid is supplied as a heat carrier;

the clay stabilizer is added to the alkali in the form of several rims;

reduce the mobility of the gas-water phase;

as an agent that reduces the mobility of the gas-water phase, polyacrylamide or hypane, or carboxymethyl cellulose, or gas-water heterogeneous systems are used.

The essence of the invention lies in the fact that under the hydrated regime of the object and when establishing the fact of the formation of gas hydrates, they ensure the destruction (decomposition) of existing natural gas hydrates and / or prevent their formation by establishing the corresponding flow rate or such pressures, temperature and humidity at which additional (to existing) gas hydrates are formed. In this state of the object, an aqueous alkali solution with the aforementioned concentration and pH values is supplied to the site of hydrate decomposition and / or prevention of their formation for a specified time. It has been experimentally established that it is precisely under such conditions, under such characteristics of the alkali solution and the mode of its supply, that it is possible to cycle the means for decomposing and / or preventing the formation of gas hydrates, which significantly reduces the consumption of this tool. The very cyclic nature of the flow of funds additionally creates the unsteady nature of the operation of the object as a whole. And this nature of the object’s operation leads to a significant decrease in the rate of formation of gas hydrates, which is several times (several times) lower than the rate of their decomposition. Moreover, due to the practical difficulty of maintaining a hydrate-free regime, the formation of gas hydrates still occurs, for example, between cycles. However, unconsolidated gas hydrates are formed and only in suspension (in the form of snow). They do not attach to the operation channel, do not form a dense core and therefore easily decompose during processing.

Caustic soda or salts of weak acids and strong bases, for example, Na ₂ CO ₃ , Na ₃ PO ₄ , whose solutions are hydrolyzed with a pH in the range of 10-14, can be used to prepare an alkali solution under commercial conditions.

As an example, a scheme for the hydrolysis of sodium phosphate is given:

Na ₃ PO ₄ + 3H ₂ О↔ Na ₂ HPO ₄ + Na ⁺ + OH ^- + 2H ₂ O↔ 2Na ⁺ + 2ОН ^- + Н ₂ O + NaH ₂ PO ₄ ↔ Н ₃ PO ₄ + 3Na ⁺ + 3ОН ^-

The hydroxyl group formed during hydrolysis interacts with the resulting gas hydrate and destroys it, as a result of which this hydrate decomposes into gas and water, and also prevents the formation of gas hydrate.

The drawing shows the results of laboratory studies on the change in the temperature of formation of gas hydrates depending on the type of inhibitor and its concentration.

The horizontal axis shows the concentration of inhibitors (x,%), and the vertical axis shows the change in hydrate formation temperature (Δ t, ° C).

The following conventions were used for the curves on the graph:

1 - an aqueous solution of alkali;

2 - calcium chloride;

3 - ammonia solution;

4 - methanol;

5 - diethylene glycol;

6 - glycerin.

From the curves shown in the drawing it can be seen that aqueous alkali solutions are the most effective inhibitors of the formation of gas hydrates from industrially used reagents.

The development of, for example, a gas condensate field with significant depression in the near-wellbore zone will cause hydrate precipitation with a decrease in productivity coefficient (bottom-hole zone, formation) until the fluid stops flowing into the well.

If the object of operation is a well, then its near bottomhole zone contains, as a rule, added clay from drilling fluids.

Clay-containing minerals are swellable. The swelling in fresh water of clays having a layered structure has features. The layers are interconnected by weak van der Waals forces. With an excess of negative charges, protons are introduced into the interlayer space. Due to hydrogen bonds, after the introduction of proton-associated water molecules into the interlayer space, complexes consisting of several associated water molecules penetrate, due to which proppant pressure increases, which contributes to an increase in interplanar distance (clay swells).

At low electrolyte concentrations, protons penetrate predominantly into the interlayer space, since the proton mobility is several orders of magnitude higher than the activity of metal cations.

As the electrolyte concentration increases, a process competing with the introduction of protons arises - the introduction of cations into the interplanar distance with the displacement of associated water molecules, as a result of which the distance between the clay mineral layers decreases, since the size of the cation is much smaller than the size of water associates.

In concentrated electrolyte solutions, only electrolyte cations can enter the interplanar space, and clay does not swell.

Swollen clay can be returned to its original state by increasing the concentration of cations in solution.

The concentration of electrolyte at which clays do not swell or at which swollen clays can be returned to a state as close as possible to their initial level before swelling is called the effective concentration of clay stabilization. It depends on the type of cations and the type of clay.

It follows from the foregoing that the swelling of clays of a certain type depends on the pH of the medium. It was experimentally established that the most noticeable decrease in clay swelling at a pH of more than 10.

The nature of the formation of gas hydrates and the processes of clay swelling are similar.

In the framework of the present invention, the used alkaline aqueous solution with the aforementioned necessary pH and concentration values performs in some cases an additional function, i.e. in addition to preventing the formation of gas hydrates and / or their destruction, this alkali solution also prevents clay swelling.

For other types of clays, for example, not pronounced layered structure, the introduction of special (additional) reagents to prevent their swelling. An alkaline solution of the VPK-402 type clay stabilizer is just an example of a means to prevent swelling of clays of another type and destruction of hydrates in the bottomhole zone of a well. This clay stabilizer solution is prepared in accordance with [7].

Currently, the development of gas hydrate deposits, in which the main resources are concentrated, is not carried out not only because of the lack of effective and reasonably cheap inhibitors, but also because of the lack of technology for delivering the inhibitor to the gas hydrate reservoir.

The practice of developing oil fields involves drilling wells to maintain reservoir pressure (RPM) through which oil-displacing agents are injected.

Similarly, in a gas hydrate field, additional wells must be drilled through which reagent injection into the formation is possible.

It is obvious that hydrodynamic communication should be carried out between the production and production wells by creating filtration channels. To do this, it is necessary to make hydraulic fracturing with the formation of a horizontal crack or by drilling a horizontally directed trunk.

For the destruction of gas hydrates around the filtration channels from the injection to the production wells, for example, a hot heat carrier (water or steam), or a heat-generating solution, or a hydrate formation inhibitor, is fed into the BPD well.

To improve technical and economic indicators, injection of solutions is carried out in the form of several rims.

To increase the coverage factor in the near-wellbore zone of the PPD wellbore, for example, polymer solutions such as polyacrylamide, hypane or carboxymethyl cellulose or water-gas heterogeneous systems are used as rims to reduce the mobility of the gas-water phase with alkali.

The method is as follows.

In the selected facility under hydrated conditions, hydrocarbon products are transported through the production channel. Moreover, due to the increased risk of the formation of gas hydrates in the production channel, continuous monitoring of pressure drops along the length of this channel is carried out. In the presence of this differential, indicating a violation of the normal operating mode, set the channel interval with a differential pressure. After that, the flow rate of hydrocarbon production or the regime of the object (temperature, humidity, pressure) is established, which ensures the destruction (decomposition) of existing natural gas hydrates and / or the prevention of their formation. In this state of the object to the detected interval of the pressure drop in the production channel, i.e. to the place of decomposition of hydrates and / or preventing their formation, an aqueous alkali solution is supplied. This alkali solution is supplied with a concentration of 0.04-4.9 wt.% At a pH of more than 10. In addition, the alkali solution is supplied over a period of not less than the existence of the pressure drop along the length of the production channel, as well as at a rate of achieving a mass concentration of alkali in the gas phase of 10-15 wt.%.

A specific example of the implementation of the method.

A gas well in the conditions of Western Siberia with a depth of 2500 m, characterized by periodic formation of gas hydrates in its trunk during operation at depths of 600-1000 m, is taken as the object of operation. During the operation of the well, gas is transported through the production channel - the wellbore. In this case, control the pressure drops along the length of the wellbore. In the presence of a pressure drop of 0.5-1.5 MPa, a gas production rate is established experimentally that ensures the destruction (decomposition) of existing natural gas hydrates and / or the prevention of their formation, in this case, the production rate is reduced by 10%. The specific depth of formation of gas hydrates is determined. To do this, build a graph of the equilibrium hydrate formation curve for specific parameters of the well, at which it worked until it was switched to a non-hydrate mode, and the actual temperature in the well.

The lower boundary of the gas hydrate formation zone is determined by the intersection point of both temperature curves. In this case, the lower boundary is 900 m. The filling pipes are lowered to a depth of 930 m. If necessary, hot water is supplied into the annular space of the existing well piping to ensure the conditions for the delivery of filling pipes to the required interval of the well. An aqueous solution of sodium phosphate with a concentration of 3.5 wt.% At pH 13 is fed through pouring pipes to the place of hydrate decomposition and prevention of their subsequent formation. This solution is supplied for a period of not less than the existence of a pressure drop in the range of 600-900 m. In this in the case, the alkali solution is supplied for a total time of 12 hours in a cyclic unsteady mode, when after every 2 hours of operation, a supply break for 1 hour is carried out. The flow rate of the alkali solution is selected so that by the end of the treatment the mass concentration of alkali in the gas phase reaches 12 wt.%. After that, they switch to a stable mode of operation of the well. Further, if necessary, the operations are repeated.

Sources of information

1. Andryushenko F.K. et al. Electrolyte solutions as antihydrate inhibitors // Kharkov: Higher School, 1973, p. 38.

2. Degtyarev B.V. and others. The fight against hydrates during the operation of gas wells in the northern regions // M .: Nedra, 1976, p.253.

3. Bekirov T.M. Field and factory processing of natural and petroleum gases // M .: Nedra, 1980, p. 405.

4. RF patent No. 21266513, 08/31/95.

5. RF patent №2135742, 08.27.99.

6. RF patent No. 2146787, 09/05/95.

7. Khavkin A.Ya. Hydrodynamic principles of the development of oil deposits with low permeability reservoirs // M .: MO MANPO, 2000, 525 p.

Claims (12)

1. A method of operating an object with hydrocarbon products in a hydrated regime, including transporting hydrocarbon products along the production channel, monitoring pressure differences along the length of this channel, and, if there is such a difference, establishing the flow rate of the hydrocarbon product or the regime of the object, ensuring the destruction or decomposition of existing natural gas hydrates and / or prevention of their formation, supply in this state of the object to the place of decomposition of hydrates and / or prevention of their formation, solution alkali with a concentration of 0.04 ÷ 4.9 wt.% at a pH of more than 10, while the alkali solution is supplied over a period of not less than the time of the pressure drop along the length of the production channel, as well as at a rate and over time until the mass concentration is reached alkalis in the gas phase 10-15 wt.%. 2. The method according to claim 1, characterized in that as an object with hydrocarbon products take a gas reservoir, or gas condensate reservoir, or gas and oil reservoir, or oil and gas reservoir, or oil and gas condensate reservoir, or gas hydrate reservoir. 3. The method according to claim 1, characterized in that the well channel or the filtration channel in the reservoir of the reservoir, or the channel in the field development system, or the main pipeline channel is adopted as the production channel. 4. The method according to claim 3, characterized in that the filtration channel in the reservoir is created from an injection well of at least one to a producing well of at least one. 5. The method according to claim 4, characterized in that the filtration channel in the reservoir is created by fracturing or drilling a directed well with a horizontal wellbore, at least one, or with a horizontal wellbore and at least one branch from it. 6. The method according to claim 1, characterized in that caustic soda or salts of weak acids and strong bases are used to prepare the alkali solution. 7. The method according to one of claims 1 to 6, characterized in that the clay stabilizer is added to the alkali solution. 8. The method according to one of claims 1 to 7, characterized in that a coolant is supplied to the hydrate decomposition site and / or to prevent their formation. 9. The method according to claim 8, characterized in that steam or hot water or a thermogenerating liquid is supplied as a heat carrier. 10. The method according to one of claims 1 to 9, characterized in that the clay stabilizer is added to the alkali in the form of several rims. 11. The method according to one of claims 1 to 10, characterized in that they reduce the mobility of the gas-water phase with alkali. 12. The method according to claim 11, characterized in that as an agent that reduces the mobility of the gas-water phase with alkali, polyacrylamide, or hypane, or carboxymethyl cellulose, or water-gas heterogeneous systems are used.