RU2485305C1 - Stimulation method of formation fluid influx from well - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: stimulation method of formation fluid influx from the well consists in lowering to the well of a tubing string. Counter pressure on the productive formation is decreased owing to replacing the liquid column with liquid-gas mixture (LGM) at observance of the required value of depression on the productive formation. Before the tubing string is lowered, its lower end is equipped with a remote subsurface pressure gauge and a filter. The tubing string is lowered to the well so that the filter is located opposite the formation perforation interval; after that, treatment of the bottom-hole zone of the formation is performed using a chemical method with process exposure for reaction. Then, the tubing string is lowered further so that the filter is located below the formation bottom, and into the inter-string space there lowered is a string of flexible tubes (FT) 100 m below the liquid level in the well. The liquid column is replaced in the inter-string space of the well with LGW and lowering of the FT string is continued. When lower end of the filter of the tubing string is reached, lowering of the FT string is stopped; then, stimulation of the formation fluid influx is started by gradual reduction of density of pumped LGM till the required depression on the productive formation, which is controlled as per readings of the remote subsurface pressure gauge, is achieved. After completion of stimulation of the influx from the well there removed is FT string from the inter-string space of the well, and operating equipment is lowered to the well and the well is put into operation.EFFECT: improving efficiency and quality of stimulation of formation fluid influx from productive formation.2 dwg

Description

The invention relates to the oil industry and can be used in the development of production wells.

A known method of well development by creating a depression on the formation (patent RU No. 2272897, IPC ЕВВ 43/18; В 43/27, publ. 03/27/2006 in bull. No. 9), which includes replacing the fluid filling the well with a surface-active solution substances (surfactants) followed by aerating it by feeding a blowing agent in the form of ammonium carbonate into the well, while before feeding the blowing agents, the bottomhole zone is subjected to acid treatment with the acid being pushed into the formation, and aqueous solutions of sodium nitrate NaNO are additionally used as blowing agents ₂ and hydrochloric acid HCl; aqueous solutions of blowing agent reagents are injected in doses of 0.5-2.0 m ³ in the following sequence: ammonium carbonate, hydrochloric acid, sodium nitrite, with each subsequent solution having a density higher than the previous one, the volume of injected reagents is 0.3- 1.0 volume of the well, but not less than 1.1 of the internal volume of the pressure column, and is determined by the useful volume of the well, and the surfactant solution additionally contains hollow glass microspheres.

The disadvantage of this method is that the aeration of the surfactant solution occurs directly in the well by supplying gas-forming substances to the bottomhole zone of the well, while the sequence of chemical reactions and the temperature regime can change, which can lead to a change in the physical and chemical properties of the replacement fluid, including and decomposition of carbonated liquid into gas and water, which generally reduces the quality of well development.

Also known is a method of inducing formation fluid inflow from a well (N. A. Sidorov. Drilling and operation of oil and gas wells. - M .: Nedra, 1982, pp. 270-271), which includes reducing pressure on the producing formation by supplying it with the surface of the gas or gas-liquid mixture and replacing the column of liquid in the well with a gas-liquid mixture, while the gas is supplied by a compressor.

The disadvantages of this method are:

- firstly, the need for a compressor - a source of neutral fire and explosion-proof high pressure gas in a well;

- secondly, the compressor cannot push the entire column of fluid in the well, so you have to master it in stages, which delays the process of causing the flow of formation fluid from the well.

The closest in technical essence is the method of inducing the influx of formation fluid from the well (patent RU No. 2263206, IPC ЕВВ 43/25, publ. 10/27/2005 in bull. No. 30), which includes reducing the pressure on the reservoir by replacing the liquid column in the well gas-liquid mixture by feeding the mixture with a booster unit with the selection of the components of the mixture from a working well or from the collector of production, while the required ratio of the components of the mixture to achieve a given value of pressure reduction on the reservoir provide selection nent mixture through the separator, the outputs of which are communicated to the collector of product collection.

The disadvantages of this method are:

- firstly, the low quality of the inflow from the reservoir, due to the unstable state of the gas-liquid mixture due to its premature destruction;

- secondly, the absorption of the gas-liquid mixture or its constituents by the reservoir during the replacement of the liquid in the well with a gas-liquid mixture and, as a result, a decrease in the natural permeability (reservoir properties) of the formation;

- thirdly, it is practically impossible to select the required ratio of the components of the gas-liquid mixture to achieve a given depression on the reservoir, not owning the readings of the change in the bottomhole pressure in the process of causing fluid inflow from the reservoir;

- fourthly, the low efficiency of the inflow call, due to the rapid decrease in the flow rate or the failure to achieve the specified flow rate of the well when calling the influx of formation fluid from the well.

The objectives of the invention are to increase the efficiency and quality of the flow of formation fluid from the reservoir, as well as to prevent premature destruction of the gas-liquid mixture during operation and to reduce the rate of absorption of the gas-liquid mixture by the reservoir while controlling the bottomhole pressure in the process of causing formation fluid flow from the well.

The problem is solved by the method of inducing formation fluid inflow from the well, including the descent of the tubing string into the well — tubing, reducing the back pressure on the reservoir by replacing the column of liquid in the well with a gas-liquid mixture while observing the required amount of depression on the reservoir.

What is new is that before lowering the tubing string, its lower end is equipped with a remote depth gauge and filter, the tubing string is lowered into the well so that the filter is opposite the formation perforation interval, after which the bottom-hole zone of the formation is treated by a chemical method with technological exposure to reaction, then they allow the tubing string to be lowered so that the filter is below the bottom of the formation, and the string of flexible pipes — GT — is lowered into the annular space of the well — 100 m below the fluid level in the well; the column of liquid in the annulus of the well onto the gas-liquid mixture, the GT column continues to be lowered, when the lower end of the tubing string filter reaches the lowering of the GT column, the GT column is lowered, then the flow of the formation fluid is called up by a gradual decrease in the density of the injected gas-liquid mixture until the required depression is reached on the reservoir, controlled by indications remote depth gauge, at the end of the inflow call from the well, the GT string is removed from the annulus of the well, lowered into the well We’ll run production equipment and put the well into operation.

In figures 1 and 2 sequentially depicted diagrams of a method of causing the influx of reservoir fluid from the well.

The proposed method is as follows.

It is known that during well operation, there is a decrease in the flow of formation fluid to the bottom of the producing well due to a deterioration in the permeability of the bottom-hole formation zone (BHP), and therefore there is a need to restore the flow of formation fluid to the bottom of the producing well. To do this, stop the production well 1 (see Fig. 1), remove production equipment (for example, a pipe string with an electric centrifugal pump) (not shown in Figs. 1 and 2). Before lowering the tubing string 2, a remote depth gauge 3 is installed sequentially from bottom to top at its lower end, for example, in a plugged container to prevent damage during operation (not shown in Fig. 1), and then filter 4 (see Fig. 1) . After that, the tubing string 2 is lowered into the well 1, the tubing string 2 is lowered so that the filter 4 is in the interval between the roof 5 'and the sole 5' ', i.e. placed opposite the perforation interval of the formation 6. For example, if the perforation interval of the formation 6 is 3 m, then the height of the filter 4 should not be less than 3 m.

Then, the bottom-hole zone 7 of formation 6 is treated by a chemical method. Filter 4 allows the injection of a chemical agent (for example, acid, hydrocarbon solvent) during the treatment of the bottom-hole zone 7 of formation 6 by a chemical method. In addition, the presence of filter 4 allows you to place at the lower end of the tubing string 2 remote depth gauge 3, with which the pressure is monitored in the process of causing formation fluid flow from the well.

To do this, at the wellhead 1 (see FIG. 1), the injection line 8 of the pump unit 9 (for example, CA-320) is connected to the inner space 10 of the tubing string 2. Next, using the pump unit 9 through the inner space 10 of the tubing string 2 and a filter 4, injection into the bottom-hole zone 7 of formation 6, for example, a hydrocarbon solvent (i.e., a bath of hydrocarbon solvent is installed). As a hydrocarbon solvent, for example, Nefras-S 150/200 according to TU 38.40125-82 or Nefras-Ar 120/200 according to TU 38.101809-80 is used. The estimated amount of hydrocarbon solvent is determined empirically individually for each well, depending on the permeability, porosity, degree of contamination, but not less than the volume of the well from the bottom to the top 5 'of formation 6 and is calculated by the formula:

where P = 3.14;

V _p - estimated volume of hydrocarbon solvent, m ³ ;

D is the inner diameter of the well casing, m;

h is the distance from the bottom to the roof 5 'layer 6, m

For example, when the distance h = 50 m and the inner diameter of the casing string D = 168 mm - (9 mm · 2) = 150 mm = 0.15 m, the necessary volume of hydrocarbon solvent (V _p ) for installing the bath is determined:

V _p = 3,14 · (0,15 m) ^2/4 · 50 m 0.9 m = ³

Produce technological exposure for, for example, 12 hours to the reaction of a hydrocarbon solvent to dissolve paraffin-tar deposits in the bottom-hole zone 7 of formation 6, while discharging the discharge line 8 and the pump unit 9.

The ground equipment is strapped as shown in figure 2. Then, the tubing string 2 is lowered (see Fig. 2) so that the filter 4 is below the bottom of the formation 6, after which the inner space 10 of the tubing string 2 is tied with a groove capacity 11 at the mouth wells 1 by means of an annular valve 12 and flow line 13, while the readings of the remote depth gauge 3 are, for example, 9 MPa.

At the end of the technological exposure (reaction time, for example, 12 hours), a string of flexible pipes (HT) 15, for example, 38 mm in diameter, placed on a drum (not shown) of the coiled tubing unit 15 'is lowered into the annular space 14 of well 1 (see FIG. 2). The GT column is lowered 100 m below the fluid level (static level) in well 1. The static level depends on the bottomhole pressure of the well and is individual for each well and is determined by geophysical studies (level beating) and is provided in advance before the implementation of the proposed method for planning process parameters.

Next, at the wellhead 1, the GT 15 column is connected through the discharge valve 16 to the injection line 17 of the booster unit 18, for which, for example, a gas booster system of the UNG 8/15 brand is used. Additionally, the inner space 10 of the tubing string 2 is tied with a central valve 19 with a flow line 20 into a groove tank 11.

At the wellhead 1, a gas-liquid mixture is prepared, which is an aqueous solution with a surfactant, which is used as a foaming agent.

The required volume of an aqueous surfactant solution to cause the formation fluid inflow from the well is determined based on the multiplicity of the gas-liquid mixture, which is 3.5-5 in the process of invoking the formation fluid inflow from the well, as well as from the required volume of the gas-liquid mixture V _g , consisting of the volume V ₁ of annular space 14 of well 1 for replacing fluid in a borehole in the gas-liquid mixture before the start of the call and the inflow volume V ₂ of annular space 14 for circulation of wellbore 1 liquid mixture during a call influx Lastovo fluid from the well. These volumes are equal, i.e. of two equal volumes of one well, namely: V ₁ = V ₂ , then V _g = 2 · V ₁ , we take the foam multiplicity equal to 4, then the volume of the aqueous surfactant solution is determined by the formula:

where V _in - the volume of an aqueous solution of a surfactant, m ³ ;

V ₁ - the volume of the annulus of the well, m ³ .

For example, when the height of the liquid column from the formation to the mouth N = 1600 m and the casing string diameter is 168 × 9 mm, the volume of gas-liquid mixture for the entire process of inflow call is determined by the formula:

where P = 3.14;

V ₁ - the volume of the annulus of the well, m ³ ;

D is the inner diameter of the casing of the well, m:

D = 168 mm - (9 mm2) = 150 mm = 0.15 m.

d is the outer diameter of the tubing string, for example, 73 mm = 0.073 m;

N is the height of the liquid column from the mouth to the bottom, m, for example, N = 1600 m

Then, substituting into formula (3): V ₁ = (3.14 + (0.15 m) of ² - (0.073) ^2/4) · 1600 m 21.6 m = ^3, and the required amount of liquid mixture: V _g = 2V ₁ = 2 · 21.6 m ³ = 43.2 m ³ .

Then the required volume of an aqueous surfactant solution is determined by the formula (2):

Substituting numerical values, we obtain: V _in = V _r / 4 = 43.2 m ^3/4 = 10.8 m ^3, assume v aqueous solution of surfactant equal to 10.8 m ^3.

To increase the stability of the gas-liquid mixture, a stabilizer is added to the aqueous surfactant solution - 1% CMC-700 solution with the addition of 2% KC1 according to GOST 4234-77.

CMC-700 - sodium salt of cellulose ether and glycolic acid is a polymer company MI Drilling Fluids (USA). Practical experiments have shown that the stability of a gas-liquid mixture with the addition of a stabilizer increases by 5–9 times. The stabilizer is prepared as follows.

In fresh water ρ = 1000 kg / m ³ (heated to 40-45 ° С), CMC-700 is added with constant stirring, the process of its complete dissolution is 2.0-2.5 hours, then 2% KCl is added to the prepared solution in dry form, mix until completely dissolved. The stabilizer obtained is added to the calculated volume of an aqueous surfactant solution, and stirred for another 20-30 minutes.

As surfactants used, for example, sulfanol (according to TU 6-01-862-73) in a concentration of 0.1-0.3% of the volume of fresh water or other surfactants, for example OP-7; OP-10 (according to TU 8433-81) in a concentration of 0.3-0.6% of the volume of fresh water.

Fill the tank 21 of the booster unit 18 with an aqueous solution of a surfactant (see figure 2).

An aqueous surfactant solution eliminates the premature destruction of the gas-liquid mixture during operation until it reaches the surface of the well 1, i.e. becomes more sustainable. As a gas that is safe under ignition conditions of a hydrocarbon medium, gas (for example, nitrogen) generated by the gas generator 22 of the booster unit 18 is used, as a result of combustion of fuel (gasoline, diesel fuel) in compressed air, i.e. burnout of oxygen.

Gas from the gas generator 22 is supplied to the booster (mixing) device 23, where the gas is continuously mixed with the process fluid in the form of an aqueous surfactant solution (with the formation of a gas-liquid mixture), while the aqueous surfactant solution is supplied with a constant flow rate, for example 3 l / s, by a pump 24 from the tank 21 of the booster unit 18. The annular 12, discharge 16 and central 19 valves are opened and through the discharge line 17 the booster unit 18 serves a gas-liquid mixture (of higher density) into the GT 9 column, the density of which is Eg 850-900 kg / m ^3.

By HT column 15 in annular space 14 of the well 1 in order to replace the fluid column in the borehole is pumped gas-liquid mixture density of 850-900 kg / m ^3, which is provided with a minimum degree of aeration of an aqueous surfactant solution, e.g., 5-10 m ³ / m ^3. The descent of the GT 15 column continues, the lower end of which is submerged beneath the fluid level in well 1 at 100 m at a speed of 0.5-1 m / s (not shown in Figs. 1 and 2), while not exceeding the maximum allowable pressure developed by the booster aggregate 18 (see figure 2), for example 15 MPa. At the moment when the liquid displaced by the gas-liquid mixture in the well reaches the wellhead 1, from the annulus 14 through the annular valve 12 and the discharge line 13 into the groove tank 11, the outflow of the well liquid displaced by the gas-liquid mixture begins.

As the GT 15 column is lowered into the well 1 and the gas-liquid mixture is injected into the annular space 14, the fluid is replaced in the annular space 14 and in the inner space 10 of the tubing string 2 of well 1, i.e. gas-liquid mixture of higher density in the volume of the well 1 (V ₁ = 21.6 m ³ ), while monitoring the readings of the remote depth gauge 3, the value of which is gradually decreasing. When the lower end of the GT 15 column reaches the lower end of the filter 4 of the tubing string 2, the lowering of the GT 15 column is stopped. Since the filter 4 of the tubing string 2 is located below the bottom of the formation 6, under such conditions a minimum amount of gas-liquid mixture penetrates into the bottomhole zone of the formation, and its component composition allows to reduce the absorption rate of the gas-liquid mixture by the reservoir or completely prevent its absorption by the reservoir, thereby achieving preservation of its natural permeability (reservoir properties).

Thus, by using a string of flexible pipes to induce formation fluid from the well, the rate of foam absorption by the reservoir is reduced or foam is prevented by the reservoir, thereby maintaining its natural permeability (reservoir properties) of the reservoir.

Then cause the influx of formation fluid from the well by supplying a gas-liquid mixture into the annulus 14 of well 1, gradually reducing the density of the gas-liquid mixture from 850-900 kg / m ³ to, for example, 150-250 kg / m ³ by gradually increasing the degree of aeration from 5-10 m ³ / m ³ to 120-160 m ³ / m ³ , i.e. increase the supply of gas produced by the gas generator 22 to the booster device 23 of the booster unit 18, at a constant flow rate of an aqueous surfactant solution, for example 3 l / s, supplied by the pump 24 from the tank 21 of the booster unit 18. In this case, the circulation of the gas-liquid mixture is continued by pumping the booster unit 18 through discharge line 17, GT column 15, annular space 14 and its exit from there through flow line 13 (with open gate valves 12 and 16 and 19) into the groove tank 11 until the desired depression value is reached (pressure reduction on reservoir 6) by increasing the degree of aeration and, accordingly, reducing the density of the gas-liquid mixture. Thus, the gas-liquid mixture is circulated until the volume V _{2 is used up} , while the changes in the readings of the deep remote pressure gauge 3 are monitored.

For example, the initial bottomhole pressure was 9 MPa, as indicated above, and the value of the required depression (pressure reduction) on the reservoir is P = 4 MPa (the set value for pressure reduction is determined by the geological service of the oil and gas company individually for each well, depending on the strength of the cement ring for casing string and other factors (see Bulatov A.I. Well development [Text]: reference manual / A.I. Bulatov, Yu.D. Kagmar, P.P. Makarenko: edited by R. Yaremiichuk - M.: Nedra-Business LLC, 1999. - 473 p.).

Then the readings of the remote depth gauge 3 should not be lower than 9 MPa-4 MPa = 5 MPa. Thus, gradually increasing the degree of aeration of the aqueous surfactant solution (by increasing the volume of gas supplied by the gas generator 22 of the booster unit 18), depending on the change in the reservoir pressure, we achieve an acceptable depression on the reservoir 6. The presence of inflow from the reservoir 6 is visually determined by the volumetric output of the reservoir fluid from the well into the trough 11 together with the gas-liquid mixture. If there is a sufficient amount of formation fluid inflow from the well (determined by the geological service of the oil and gas company individually for each well, depending on the previous production rate during the operation of the well), the formation fluid inflow is stopped.

GT 15 columns are lifted from the annulus 14 of well 1. The operational equipment is lowered into well 1 and put into operation.

In the process of calling the formation fluid inflow from the well, the change in the bottomhole pressure in the well is monitored by installing a bottomhole pressure gauge 3 at the end of the tubing string 2.

The proposed method allows to increase the efficiency of calling the influx of reservoir fluid from the reservoir. Also, the proposed method allows to improve the quality of the inflow of formation fluid from the reservoir by giving the gas-liquid mixture a stable state during its circulation in the well, to reduce the rate of absorption by the reservoir, as a result of which the reservoir maintains its natural permeability (reservoir properties).

Claims (1)

A method of inducing formation fluid inflow from a well, including descent of a tubing string into a well — tubing, reducing backpressure to a producing formation by replacing a column of liquid in the well with a gas-liquid mixture — while maintaining the required amount of depression by the producing formation, characterized in that before the descent the tubing string its lower end is equipped with a remote depth gauge and filter, the tubing string is lowered into the well so that the filter is opposite the formation perforation interval, after which production They treat the bottom-hole zone of the formation by a chemical method with technological exposure to the reaction, then the tubing string is lowered so that the filter is below the bottom of the formation, and the string of flexible pipes is lowered into the annulus of the well - GT 100 m below the fluid level in the well, the column of fluid is replaced in the annulus of the well to the gas-liquid mixture, the GT column is continued to be lowered; when the lower end of the tubing string filter reaches the lower end of the GT column, the GT column is stopped and then the formation fluid inflow is initiated ennym decrease the density of the injected liquid mixture up to the desired depressions on the producing formation, according to indications of remote controlled depth gauge at the end of a call from a well inflow recovered from column HT of annular space of the borehole, is lowered into the well and start production equipment in the wellbore operation.

Images