The way to prevent hydrate formation in the wells (options)

 

(57) Abstract:

The invention relates to the oil and gas industry and is intended to prevent hydrate formation in wells, predominantly oil drilled in permafrost (MMP). In the first embodiment previously well identify local zone temperature drop of the annulus. The inhibitor before serving in these local areas are heated with the vapor phase. The heating process of the inhibitor to the vapor phase is carried out at the wellhead or in identified local areas, or directly under the lower boundaries of the identified local areas. The inhibitor serves continuously or gradually in amount which provides the desired concentration of the inhibitor by condensation in the volume of the annulus given gas composition, flow rate and temperature conditions. In preferred variants of the method after transfer inhibitor in the vapor phase at the wellhead, it is mixed with gas, e.g. natural gas from the annulus, and is heated to a temperature to prevent premature condensation of the inhibitor reaches the selected knowledge in the area of local temperature decrease, feeding it from the wellhead to the tank with a heating element placed in the mentioned area. The flow inhibitor from the wellhead are performed simultaneously or sequentially in a series of tanks with heating elements, placed sequentially on the well depth. The second option previously well identify local zone temperature drop of the annulus and the flow inhibitor is carried out in the interval from the wellhead to the upper boundary of the identified local zone temperature reduction. The inhibitor serves continuously or dosed in a quantity which provides the desired concentration of inhibitor in the volume of the annulus given gas composition, flow rate and temperature conditions. It is advisable as in the first embodiment, and second, to adjust the quantity of the injected inhibitor depending on the magnitude of the pressure in the annulus to use as an inhibitor of methanol or diethylene glycol. The implementation of the method according to both versions allows you to virtually eliminate the formation of hydrates in the annular space of wells. 2 S. and 3 C. p. F.-ly, 4 Il.

The group of inventions relates to the field of Neftegazodobycha the divine oil, drilled in permafrost (MMP).

It should be noted that in the annulus of oil wells these are the most dangerous zone for hydrate formation:

zone of permafrost rocks, where there is a local decrease in temperature, and therefore, increase the risk of hydrate formation;

in the winter the first tens of meters, when large negative temperature metal surfaces extend down.

There are various ways of elimination of crystalline deposits in oil wells, consisting in the injection of the fluid (in particular, hot water and oil), electric or thermo-chemical methods, in the destruction of hydrates by means of chemical agents, including inhibitors, either by direct mechanical impact (see Malyshev, A. G., Cheremisin N. A., Shevchenko, C. the choice of the optimal ways of dealing with parageneratorov, Oil industry, 1997, 9, S. 62-69).

The disadvantage of these methods is that they are mainly aimed not at preventing hydrate formation, and the struggle with the already formed deposits. Thus, to perform technological measures well the ptx2">

Closest to the proposed method to the technical essence and the achieved result is a way to prevent hydrates in oil wells, providing the download on the mouth in the well annulus with an interval of 10 days, a large amount mutanolysin oil and subsequent daily injection of methanol (see Isangulov A. K. the dissertation on competition of a scientific degree of candidate of technical Sciences, "Development of methods of control of complications during the operation of producing wells in Western Siberia (on the example of JSC "Chernogorneft")", M, 2000, 22 C. ).

However, this method also does not provide effective protection against the formation of hydrates in the annulus of an oil well as the insertion of large portions of the inhibitor falls down, quickly reaching the dynamic oil level. There it is mixed with water and oil fluid, losing its inhibiting properties and convective flows together with the oil goes through the tubing from the well. Daily subsequent input also does not solve the problem of preventing hydrate formation, as he suffers the same defects. In the end, there are greater loss of inhibitor, and not by its calenar is aktivnosti prevent hydrate formation in the annulus of the borehole due to supply optimal amounts of inhibitor in hydrotopes zone annulus and uniform processing inhibitor indicated hydracoach zones, having a complex geometric shape.

The problem is solved by the proposed method for preventing hydrate formation in wells, predominantly oil drilled in permafrost, including the filing of hydrate inhibitor into the well, which, according to the invention, previously well identify local zone temperature drop of the annulus, the inhibitor before serving in these local areas are heated with the vapor phase, and the heating process of the inhibitor to the vapor phase is carried out at the wellhead, or identified in local areas, or directly under the lower boundaries of the identified local areas, while the inhibitor serves continuously or dosed in a quantity which provides the desired concentration of inhibitor in the volume of the annulus given gas composition, flow rate and temperature conditions.

And also that:

after a transfer inhibitor in the vapor phase at the wellhead it is mixed with gas, e.g. natural gas from the annulus, and is heated to a temperature to prevent premature condensation of the inhibitor to achieve them in the state in the area of local temperature drop produced by its filing with the wellhead in a container with a heating element, posted in the mentioned area;

- supply of the inhibitor from the wellhead are performed simultaneously or sequentially in a series of tanks with heating elements, placed sequentially on the well depth.

According to the second variant of the invention the problem is solved by the proposed method for preventing hydrate formation in wells, predominantly oil drilled in permafrost, including the filing of hydrate inhibitor into the well, which, according to the invention, previously well identify local zone temperature drop of the annulus and the flow inhibitor is carried out in the interval from the wellhead to the upper boundary of the identified local zone temperature decrease, and the inhibitor serves continuously or dosed in a quantity which provides the desired concentration of inhibitor in the volume of the annulus given gas composition, flow rate and temperature conditions.

It is expedient in the method according to the first and second variant the number of input processing inhibitor to adjust depending on the magnitude of the pressure in the annulus.

Galtelli diethylene glycol.

The claimed group of inventions to meet the requirement of unity of invention, since the group single object of the invention form a single inventive concept, the invention relates to the objects of the invention one type, the same purpose - to prevent hydrate formation in wells that provide the same result - increasing the effectiveness of the prevention of hydrate formation in the annulus of the borehole due to the supply of the specified rated amount of hydrate inhibitor in the most hydropenia zone annulus and uniform processing inhibitor.

The method according to the first embodiment is as follows.

In the casing-formation annulus identify local zone temperature reduction. These zones are identified either by thermal images of production data, or thermobaric curve in the turns, obtained by calculation.

Next, determine the amount of inhibitor applied in hydrotopes zone. To do this, first on a deep reservoir oil samples by calculation, determine the composition of the gas at the temperature and pressure at the line of the dynamic level at which emalina temperature - annulus pressure is built hydrate formation curve, parallel system hydrate formation curves given inhibitor. The position of this curve determines the estimated concentration of inhibitor that given the production rate of oil and gas factor can be calculated on the content of the inhibitor in the volume of the annular space.

The estimated amount of the inhibitor in the form of steam is supplied into the annulus, and the translation inhibitor named in the vapour phase can occur both at the wellhead and in the annulus. In the annulus inhibitor is mixed with an ascending stream of gas is cooled and evenly condenses on the walls of the columns where it mixes with the existing film of water. Achieving the desired concentration of inhibitor, at least 5 wt.% After condensing on the pipe walls, photometadata mixture flows down, where at higher temperatures inhibitor evaporates, rises (due to convection or gas flow), where the cooling and re-condensation, i.e. recirculation inhibitor, which enhances the inhibitory effect. With the aim of one-time processing of large area annular space may smashin the public before entering into the borehole, moreover, to prevent premature condensation inhibitor natural gas is heated.

The method according to the second variant is as follows. First define the local zone temperature decrease, and calculate the optimal number of inhibitor, as in the first embodiment. Enter the estimated amount of the inhibitor is, for example, injection pump that does not require a graphical illustration.

Under the action of gravity inhibitor on the borehole wall flows down, passing all of the area of MLM. This provides the primary passage on hydrotopes zone and the manifestation of antihydrate properties. Due to the low temperatures in this zone inhibitor practically does not pass into the gas phase and not swept up from the well.

The result of the first pass is that the inhibitor, flowing in a thin stream, wets only a limited part of the surface of the pipe annulus. Antihydrate processing narrow segment of the pipe is due to the inclination of the borehole that there is almost always, and not only in the case of inclined wells.

After passing zone MMP, the inhibitor enters the lower zone wells, reaching relatively more and flows of natural gas.

Further, the hydrate formation inhibitor together with a flow of gas goes up, falls in the interval MMP, cools and condenses, thus providing antihydrate protection of the entire surface of the pipes of this area of the annular space (secondary hit inhibitor in zone MMP well).

Then the inhibitor together with a film of water flows down, gets in the heated zone of the well, where it passes into the vapour phase and is mixed with the ascending flow of natural gas. Then he comes to zone MMP, where once again demonstrates its protivovirusnye properties. When this happens multiple recycling inhibitor.

In Fig.1 to 3 is a schematic of a device implementing the method according to the first embodiment, and Fig.1 shows a diagram of the device for transfer inhibitor in the vapor phase on the surface, and Fig.2 and 3 are diagrams of devices for translation inhibitor in the vapor phase in the annulus of the well-fed inhibitor in identified areas, and directly below the lower boundary of the identified zones of local temperature decrease, respectively; Fig.4. presents characteristics of hydrate formation in the annulus of the well.

In Fig. 1 until the

The device shown in Fig.1, contains an insulated box 1 on a truck chassis, which is a cumulative capacity of 2, connected by a tube with a valve 3 with the capacity of the translation inhibitor in steam phase 4, provided with a heater 5, a tank mixture with 6 heating element 7, the compressor 8. The compressor through the tubes 9, 10 and the gate 11 is connected with made of material with low heat conductivity of the tube 12, which by means of clamps 13 is attached to the string of tubing 14. In the interval MMP 15 in the tube 12 with holes 16 to output the supplied gas mixture in the annulus 17. The tank 6 through the tube 18 with the valve 19 is connected with the annular space of the well. Using threaded fasteners tube 9 and 18 can be disconnected from the annulus, the valves 11 and 19 overlap with the gas. Transition element 20 serves for the connection of the tube 12 to the system after the operation of the descent of tubing. Tanks 4 and 6 have a heat insulating shell. All connecting pipes are enclosed in a heat insulating casing.

In addition to placing the installation on a truck chassis, a possible variant storedvalue in automatic mode.

In Fig. 2 and 3 shows a schematic diagram of a device for transfer inhibitor in the vapor phase directly in the annulus of the well. The device in Fig.2 provides a pulsed flow of this portion of the inhibitor in the form of steam in the identified area sink temperature, and the device of Fig. 3 provides a flow inhibitor in the vapor phase directly under the lower border of the identified zones of local temperature decrease.

The implementation of the method using the steam generator shown in Fig.2, is as follows. The inhibitor through the open valve 21 to the tube 12 enters the tank 22. When pressure equalization in the receiver 12 and the vessel 22, the valve 21 with the spring 24 is closed. The heater 5 to be included in the automatic mode, provides the supply voltage. Inhibitor in the tank 22 is heated and becomes steam. When the threshold pressure, the valve 23 is opened, the inhibitor in the form of steam is served in the well annulus, where it is mixed with an ascending stream of gas and condenses on the cold surfaces of the downhole pipe. The tube 12 and the cable 25 is fixed to tubing clamps 13 which serve simultaneously with the portion of the inhibitor and the termination of heating, the pressure in the tank 22 falls. The valve 23 is closed and valve 21 is opened and passes into the container 22 a new dose of the inhibitor. Turns on the power supply and the process repeats.

The difference between the implementation of the method using the device shown in Fig.3, is that the inhibitor of the tube 12 is served in an open tank 22 where it is heated using the heater 5, which is located in the lower part of the vessel 22 or even in her bottom. The heater operates continuously, providing the intensity of heating is sufficient for all the incoming inhibitor passed in pairs, and not over capacity and not dripping down on struby. To save power capacity 22 has a narrow outlet opening 26 and are surrounded by the insulating sheath 27. To protect from overheating, the introduction of the control of the regulatory element 28, interrupting the power supply circuit of the heater. The other designations are the same as in Fig.2.

The device is placed directly under hydrotopes area. The produced steam with a stream of gas goes up, comes in the area of MLM and condenses on the cooled surfaces of the pipes.

The following is a specific example of calculating the number of inhibitorslipitor the following steps:

Based on the data of the images T(h) idle wells for pressure Pzin turns builds curve changes thermobaric conditions (T(h) Pzfrom the depth h in the wall of the production string (EC) wells. More accurate temperature curve in the turns, can also be obtained through calculations on a computer (see Ivan R., Vakhitov, and Battles O., vagina H., Without hydrates: optimal control technology with hydroperiodide sediments. Oil of Russia, 2000, 3, S. 96 - 99). In the case of operating wells is entered, the corresponding adjusting for the difference between the temperature measurement and temperature at the pipe wall, which can amount to several degrees.

In Fig. 4 shows an example curve thermobaric conditions for wells within the area of MSE (case of relict permafrost), which is conditional. On the constructed curve is determined by the minimum temperature Tminat this depth interval. Next, determine the composition of gas in the annulus of an oil well. The definition of two ways: payment (preferred) and experimental.

In the calculation method source is sadang equations of state calculated the composition of natural gas xjlocated in phase equilibrium with the oil at the temperature and pressure conditions (Tu, Ruon the depth of the dynamic oil level hu.

The experimental method is significantly more time-consuming. In its composition of natural gas is obtained in the bomb, PVT, by separating the oil reservoir for the liquid and gas phases at given temperature and pressure (Tu, Ru).

Obtained by the composition of the gas xiby calculation is determined by the curve of hydrate formation conditions. In Fig.4 shows characteristics of hydrate formation in the annulus of the well.

Using the methods (see Vyatchanin M G, Battaglia, O. Y., vagina N. G, N. Shchepkin. E. Determining modes and zones of hydrate formation in oil wells". Oil industry, 7, 2000, S. 38-44), are determined by the curves of hydrate formation conditions for a given mass concentration of the selected inhibitor (e.g., methanol) in water. In the coordinates T-R built calculated curves are shifted relative to the original curve towards lower temperatures (Fig.4).

For the found values of temperature Tminand the setpoint pressure in the casing-formation annulus Pz marked the point with the coordinates is obrazovaniya. The position of this curve is the concentration of inhibitor required to prevent hydrate formation. In Fig.4 is 12 wt.% methanol in water. Taking into account the flow rate of oil and gas factor this concentration is recalculated on the content of the inhibitor by condensation in the volume of the annulus. An important value held in the above calculations is the pressure Pzthat may change during operation. Depending on this pressure varies as the position of the curves hydrate formation, and the position of the temperature curve in the turns. In this regard, to determine the technically required amount of inhibitor necessary to perform the above calculations for the entire range of possible pressure Pzand take the maximum value of the quantity of the inhibitor of the received values. In addition, be aware of potential inaccuracies in defining the source values and errors in the conduct of operations.

Depending on the device inhibitor is fed continuously or dosed. In the second case, the interval between treatments should not be large: it is necessary that in the annulus was always a sufficient number of the ora V (kg/min) when dosed feed is determined by the formula V = MwithTc/(1440T1), where Mwith- daily feeding inhibitor (kg), Tcthe time of a single cycle, T1- the duration of a single feed (min.)

Thus, the proposed method, the first and the second option allows effective prevention of hydrate formation in the annulus of an oil well.

1. The way to prevent hydrate formation in wells, predominantly oil drilled in permafrost, including the filing of hydrate inhibitor into the well, wherein the pre-well identify local zone temperature drop of the annulus, the inhibitor before serving in these zones sink temperature is heated by the vapor phase, and the heating process of the inhibitor to the vapor phase is carried out at the wellhead, or directly in the identified zones of local temperature decrease, or directly under the lower boundaries of the identified areas, while the inhibitor serves continuously or gradually in number, which provides the desired concentration of the inhibitor by condensation in the volume of the annular space is given with the translation inhibitor in the vapor phase at the wellhead it is mixed with gas, for example, with natural gas coming from Struble, and heated to a temperature to prevent premature condensation of the inhibitor reaches identified local zone temperature decrease.

3. The method according to p. 1, characterized in that the heating process of the inhibitor to the vapor phase is produced directly in the area of local temperature decrease by filing with the wellhead in a container with a heating element placed in the mentioned area.

4. The method according to p. 1, characterized in that the supply of the inhibitor from the wellhead are performed simultaneously or sequentially in a series of tanks with heating elements, placed sequentially on the well depth in identified areas of the sink temperature and below the lower boundaries of the identified zones.

5. The way to prevent hydrate formation in wells, predominantly oil drilled in permafrost, including the filing of hydrate inhibitor into the well, wherein the pre-well identify local zone temperature drop of the annulus and the flow of hydrate inhibitor is carried out in the interval from the wellhead dozirovanno in number, which provides the desired concentration of the inhibitor by condensation in the volume of the annulus given gas composition, flow rate and temperature conditions.

6. The method according to p. 1 or 5, characterized in that as a hydrate formation inhibitor use methanol or diethylene glycol.

 

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