RU2470150C1 - Method of causing fluid intrusion from well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention may be used in development of wells with bed pressure of 0.8-1.0 of water column hydrostatic pressure in well. Proposed method comprises running-in of tubing into well, decreasing pressure on productive bed by replacing water column with gas-fluid mix by forcing it with the help of booster unit, and providing required ratio of mix components to reach required pressure on productive bed. Note here that at bed pressure of 0.8-1.0 of water column hydrostatic pressure in well, remote-control depth gage is fitted on tubing bottom end prior to running in. Tubing run-in in well, water column is replaced with gas-fluid mix be injecting it by booster unit, said mix representing higher-density foam including surfactant with minor aeration of 5 to 7 m³/m³. Then, fluid intrusion is initiated by injecting gas-fluid mix in well annular space while higher-density foam is replaced with lower-density foam. Aeration is gradually increased control pressure on production bed to preset magnitude to be controlled by said depth gage. Reached pressure is maintained by varying injection pressure of booster unit to circular foam in volume equal to that of the well. If fluid intrusion occurs, foam in well is replaced by process fluid with density that allows maintaining bed collecting properties. Note here that in case fluid intrusion does occur, foam circulation is terminated to define acidity of well fluid by sampling bed fluid for pH-factor. Thereafter, acid composition is injected and forced into bed via tubing. Then, pause is made for 2-3 h to open tubing gate valve to repeat abode described jobs.

EFFECT: higher quality and efficiency.

2 dwg

Description

The invention relates to the oil and gas industry and can be used in the development of wells with reservoir pressure in the range from 0.8 to 1 from the hydrostatic pressure of the liquid column in the well.

There is a method of well development by creating a depression on the formation (patent RU No. 2272897, IPC ⁸ ЕВВ 43/18; В 43/27, publ. 03/27/2006 in bull. No. 9), which includes replacing the fluid filling the well with a solution of surface active substance (surfactant) with its subsequent aeration 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 are additionally used as blowing agents NO 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 disadvantages of this method are:

- firstly, the surfactant solution is aerated 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 decomposition carbonated liquid for gas and water, which generally reduces the success of well development;

- secondly, the magnitude of the depression created on the bed is not regulated.

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 reservoir 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 magnitude of the depression created on the formation is not controlled from the wellhead.

The closest in technical essence is the method of causing the flow of formation fluid from the well (patent RU No. 2263206, IPC ⁸ ЕВВ 43/25, publ. 10/27/2005 in bull. No. 30), including the descent of the tubing string (tubing) into the well, reducing the pressure on the reservoir by replacing the column of liquid in it with a gas-oil mixture by supplying the mixture with a booster unit with the selection of the components of the mixture from a working well or from a production collector, while the required ratio of the components of the mixture to achieve a given pressure reduction Pouring to the reservoir provide the selection of the components of the mixture through a separator, the outputs of which are communicated with the collector of product collection.

The disadvantages of this method are:

- firstly, to select the components of the mixture (gas and liquid) necessary for the operation of the booster installation, you need a source in the form of a working well or collector of production;

- secondly, to obtain a stable density of the gas-liquid mixture (foam), the addition of surfactants as a foaming agent is necessary, otherwise premature decomposition of the foam into components, loss of its calculated density and, as a consequence, a decrease in the quality and efficiency of causing formation fluid inflow from wells;

- thirdly, it is almost impossible to select the required ratio of the components of the gas-liquid mixture to achieve a given depression on the reservoir, without controlling the change in the bottomhole pressure during the process of causing fluid inflow from the reservoir;

- fourthly, when the inflow of formation fluid from the well is called by applying a gas-liquid mixture (foam) by a booster unit to the annular (annular) space, the liquid is forced to the surface through the tubing string, repression to the formation is created, therefore, when developing wells, in which the reservoir pressure in the range from 0.8 to 1 hydrostatic pressure of the borehole fluid column, as the foam column in the annular space approaches the lower end of the tubing string, a significant amount of borehole penetrates into the formation Liquids, which negatively affects the efficiency of the call process fluid inflow from the well and significantly reduces the productivity of the formation. On the contrary, if the call of formation fluid inflow from the well, the reservoir pressure in which is in the range from 0.8 to 1 hydrostatic pressure of the wellbore column, is carried out only by pumping the gas-liquid mixture into the tubing string, then at the initial moment of the inflow call, this requires higher pressures, developed by the booster unit to displace well fluid from the annular space to the surface, due to the large difference in the cross sections of the annular and pipe spaces, therefore the process of reducing the density of foams , Ie the degree of its aeration is delayed, which in turn increases the duration of the process of causing formation fluid inflow from the well.

The objective of the invention is to improve the quality and efficiency of the call inflow of reservoir fluid from the reservoir, the reservoir pressure of which is in the range from 0.8 to 1 from the hydrostatic pressure of the liquid column in the well by eliminating premature inflow of the reservoir fluid from the well and making the gas-liquid mixture (foam) stable conditions with the possibility of changing the degree of its aeration, minimizing the flow of borehole fluid into the formation in the process of causing the influx of formation fluid from the well, as well as monitoring the change in bottom hole pressure during the call flows.

The problem is solved by the method of inducing formation fluid inflow from the well, including lowering the tubing string into the well, reducing the pressure on the reservoir by replacing the column of liquid in the well with a gas-liquid mixture by feeding it with a booster unit, ensuring the required ratio of the components of the mixture to achieve the desired pressure drop on the reservoir .

New is that at reservoir pressure in the range from 0.8 to 1 from the hydrostatic pressure of the liquid column in the well, before the descent into the well, a remote depth gauge is installed on the lower end of the tubing string, after the tubing string is lowered into the well, the fluid column in the well is replaced by injection a booster tubing aggregate liquid mixture - high density foam comprising, a low degree of aeration surfactant from 5 to 7 m ³ / m ^3, whereupon the call formation fluid influx from skva otherwise, by supplying a gas-liquid mixture to the annulus of the well with the replacement of high-density foam with a foam of lower density and by gradually increasing the degree of aeration, the pressure on the reservoir is reduced to a predetermined value, which is controlled by the readings of the remote depth gauge, further maintaining the achieved pressure value by changing injection pressure of the booster unit, foam is circulated in a volume equal to the volume of the well, in the presence of an influx of reservoir fluid from the well the fluids replace the foam in the well with a technological fluid with a density that ensures the reservoir properties of the formation, and if there is no influx of formation fluid from the well, foam circulation is stopped, the acidity of the formation fluid from the well is determined by sampling for pH, after which injection is performed through the tubing string and the injection of the acid composition into the formation, withstand a technological pause for 2-3 hours, after which the annular valve is opened and the operations described above are repeated, while after the process replacing high density foam with a lower density foam determines the acidity of the formation fluid from the well by sampling for pH.

Figure 1 shows a diagram of the replacement of fluid in the well by pumping a gas-liquid mixture (foam) into the tubing string.

Figure 2 shows a diagram of the call flow formation fluid from the well by pumping a gas-liquid mixture (foam) into the annulus of the well.

The proposed method is as follows.

When reservoir pressure in the well is in the range from 0.8 to 1 from the hydrostatic pressure of the liquid column in the well, the condition

where P _PL - reservoir pressure in the well, MPa;

P _g - hydrostatic pressure of the liquid column in the well, MPa.

For example, at a reservoir pressure of 14 MPa and hydrostatic pressure of a liquid column in a well with a height of H = 1680 m

where ρ is the density of the fluid in the well, kg / m ³ , for example, the density of water is 1000 kg / m ³ ;

g - the acceleration of gravity is 9.8 m / s ² ;

N - the height of the liquid column in the well from the reservoir to the mouth, m

Then, substituting into formula (2), we obtain

P _g = 1000 kg / m ³ × 9.8 m / s ² × 1680 m = 16.8 MPa.

Substituting in the formula (1), we obtain:

14 MPa = (0.8-1) × 16.8 MPa = 13.4-16.8 MPa, which satisfies condition (1).

Next, the assembly and strapping of equipment. To do this, before lowering the tubing string 1 (see Fig. 1) into the well 2, a remote depth gauge 3 (conventionally shown in Fig. 1) is installed on the lower end of the tubing string, while its readings are transmitted to the control station (Fig. 1 and 2), which makes it possible to track the change in the bottomhole pressure during the process of inducing fluid inflow from the formation 4. A tubing string 1 is lowered into the well 2, while its lower end should be at a depth h 2-3 meters above the bottom of the formation 4.

A faceplate 5 is installed at the wellhead 2 with a central valve 6 on the discharge line 7. The annular valve 8 is tied up by a flow line 9 with a trough capacity 10. The central valve 6 is connected with the pressure line 7 of the booster unit 11, for example, a gas booster plant of the type UNG 8/15. Open the central 6 and annular 8 gate valves. For example, according to the testimony at the control station of the remote depth gauge 3, the value of the reservoir pressure of the formation 4 is 9 MPa. At the wellhead 2, a gas-liquid mixture (foam) is prepared, which is an aqueous solution with a surface-active substance (surfactant), while the surfactant 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 foam multiplicity, 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 the} well to replace the fluid in the well with a gas-liquid mixture before starting the inflow and volume V _{2 of the} well, for circulating the gas-liquid mixture (foam) in the process of invoking the formation fluid inflow from the well, i.e. of two equal volumes of one well, namely: V ₁ = V ₂ , then V _g = 2V ₁ , and when the foam multiplicity is 3.5-5, the volume of an aqueous surfactant solution is determined by the formula

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

V _g - the required volume of the gas-liquid mixture, m ³ .

3,5-5 - the multiplicity of the foam.

For example, with a well depth of L = 1700 m and a casing string diameter of 168 × 9 mm, the volume of the gas-liquid mixture for the entire inflow call process is determined by the formula

where V ₁ - well volume, m;

P = 3.14;

d is the inner diameter of the well casing, m, i.e.

d = 168 mm - (9 mm × 2) == 150 mm = 0.15 m;

L is the depth of the well from the mouth to the bottom, m

Then substituting the formula (4): V ₁ = (3,14 × (0,15 m) ^2/4) × 30 = 1700 m ³ m, while the required amount of liquid mixture: V _d = 2V ₁ = 2 × 30 m ³ = 60 m ³ .

With a multiplicity of foam from 3.5 to 5, we take the multiplicity of foam equal to 4.

Then the required volume of an aqueous surfactant solution is determined by the formula (3)

V _in = 2V ₁ / (3,5-5) = 60 m ^3/4 = 15 m ^3, assume aqueous surfactant solution volume of 15 ^m3. An aqueous surfactant solution is prepared. For this, surfactants are added to fresh water with a density ρ = 1000 kg / m ³ , for example, sulfanol (according to TU 6-01-862-73) at 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 12 of the booster unit 11 with an aqueous solution of a surfactant (see figure 1). As a gas that is safe under ignition conditions of a hydrocarbon medium, gas (for example, nitrogen) generated by the gas generator 13 of the booster unit 11 is used, as a result of the combustion of fuel (gasoline, diesel fuel) in compressed air, i.e. burnout of oxygen.

Gas from the gas generator 13 is supplied to the booster (mixing) device 14, where gas is continuously mixed with the process fluid in the form of an aqueous surfactant solution (with the formation of a gas-liquid mixture) supplied by the booster pump 15 from the tank 12 of the booster unit 11. The central valve 6 is opened and through the injection line 7 by the booster unit 11 serves a gas-liquid mixture (foam) into the tubing string 1, i.e. into the pipe space 16 of well 2 in order to replace the entire column of fluid in the well (well fluid), while the foam is injected with a low degree of aeration from 5 to 7 m ³ / m ³ , i.e. 5-7 m ^{3 of} air per 1 m ^{3 of an} aqueous surfactant solution, while the flow rate of an aqueous surfactant solution is taken to be 6-8 l / s. Injection of foam with a low degree of aeration (from 5 to 7 m ³ / m ³ ) allows foam to be present in the wellbore during the subsequent call of formation fluid instead of water, without causing a premature flow of formation fluid from the formation, and also prevents the formation of air traffic jams in the well, since the presence of the latter sharply increases the pressure, as a result of which the normal pricing process is disrupted. At the moment the column reaches the foam of the lower end of the tubing 1 from the annulus 17 of the tubing 1 through the annular valve 8 and the flow line 9 into the trough 10, the outflow of the well fluid displaced by the foam begins. The injection of foam into the tube space 16 is continued until the well fluid is completely replaced with a volume of V ₁ , i.e. before the appearance of foam in the gutter container 10 (determined by the appearance of the circulation of the foam).

The meaning of this technological operation is to have foam instead of water in the wellbore during its development without causing a premature inflow of formation fluid. After this, the flow of formation fluid from the well is called by supplying a gas-liquid mixture (foam) to the annulus 17 (see FIG. 2) of well 2. For this, a faceplate 5 with a central valve 6 is installed at the wellhead 2 (see FIG. 2), flow line 9 is tied with a gutter capacity 10.

The annular valve 8 of the well 2 is connected with the injection line 7 of the booster unit 11, for which, for example, a gas booster plant of the UNG 8/15 brand is used. Open the central 6 and annular 8 gate valves. For example, according to the testimony at the control station of the remote depth gauge 3, the value of the reservoir pressure of the formation 4 is 9 MPa.

Foam is injected into the annulus 17 through the injection line 7 and the open annular gate valve 8, then in the well 2, foam of a large (initial) density (5-7 m ³ / m ³ ) is replaced by a foam of lower density (up to 120-150 m ³ / m ³ ) by gradually increasing the degree of aeration from 5-7 m ³ / m ³ and above, i.e. increase the supply of gas produced by the gas generator 13 to the booster device 14 of the booster unit 11, with a constant flow of an aqueous solution of surfactant equal to 6-8 l / s, while the circulation of the foam is continued by pumping the booster unit 11 through the discharge line 7 into the annulus 17 and exit into the trough 10 through the flow line 9 and the pipe space 16 of the tubing string 1 until a predetermined pressure reduction is achieved by increasing the degree of aeration, for example, up to 150 m ³ / m ³ on the reservoir, while the distant readings are monitored station depth gauge 3, the value of which is gradually decreasing.

For example, the value of the set value (allowable depression) of the pressure drop on the reservoir is 4 MPa (the set value of the pressure drop is determined by the geological service of the oil and gas company individually for each well, depending on the strength of the cement ring behind the casing, the stability conditions of the bottomhole formation zone, etc. ( see Bulatov A.I. Well development [Text]: reference, allowance / A.I. Bulatov, Yu.D. Kagmar, P.P. Makarenko: edited by R. Yaremiychuk - M .: Nedra OOO Business, 1999. - 473 p.). Then the testimony depth gauge 3 must not be lower than 9 MPa - 4 MPa = 5 MPa. Thus, gradually increasing the degree of aeration of the foam (by increasing the volume of gas supplied by the gas generator 13 of the booster unit 11), depending on the change in reservoir pressure, we achieve an acceptable depression by formation 4. Upon reaching the set value of the bottomhole pressure of 4 MPa, the circulation of the foam is continued, but the increase in the degree of aeration of the foam is stopped. Further, maintaining the achieved pressure by changing the injection pressure of the booster unit (back pressure at the wellhead), foam is circulated in a volume equal to the volume of the well (V ₂ ), while the pressure is monitored according to the readings of the remote depth gauge 3.

The presence of inflow from the formation 4 is determined visually by the volumetric output of the formation fluid from the well into the trough 10 together with the foam. With 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 and the well fluid is replaced with the technological fluid with a density that preserves reservoir reservoir properties 4. for example, the process fluid is oil-based with a specific gravity of 900-930 kg / m ^3, which is the most appropriate in terms of physical and chemical parameters, the specific gravity of the products extracted from the formation 4, while ensuring the reservoir properties of the formation 4 are maintained. The tubing string 1 is lifted, production equipment is lowered into the well 2 (not shown in FIGS. 1 and 2) and put into operation .

In the absence of formation fluid inflow from the well (determined by the presence of the formation fluid output together with the foam at the wellhead into the trough 10), when the specified acceptable depression on the formation is reached, as described above, the circulation of the foam is stopped.

The acidity of the formation fluid from the well (production) is determined using litmus paper lowered into the groove capacity 10 (by sampling) and the pH value is determined by changing its color.

An acid composition is injected through the tubing string 1 (for example, HCI-12% + HF-5% + 1%, the rest is an aqueous solution of ML-81B), the annular valve 8 is closed, and the acid composition is pressed with a squeezing liquid, for example, fresh water with a density of 1000 kg / m ³ in the reservoir 4, after which they withstand a technological pause for 2-3 hours. Then, the annular valve 8 is opened and the operations described above for triggering the inflow of formation fluid from the well are repeated, with the squeezing fluid being replaced with high-density foam in a volume of V ₁ and replacing high-density foam with a foam of lower density in a volume of V ₂ .

After replacing the foam of high density with foam of lower density during the circulation of the foam in the well volume (V ₂ ), the acidity of the product is determined by sampling for pH. The pH factor allows you to determine the acidity of the product that was obtained during the inflow call and is necessary to reduce the acidity of the product resulting from the stimulation of formation fluid from the well causing corrosion of the oilfield equipment. The pH is determined by sampling using litmus paper dipped in the groove capacity 10 and the value (pH) is determined by changing its color.

Measure the acidity of the product (pH ₁ ) before injecting and selling the acid composition into the formation, for example, pH ₁ is 5. Next, the influx of formation fluid from the formation is called up and after replacing the high density foam with a foam of lower density after the circulation of the foam in the well volume V _{2, the} injection is stopped .

Then measure the acidity of pH ₂ , if this value is approximately 5, then the circulation of the foam is stopped. If pH _{2 is} less than pH ₁ , then additional foam is circulated, for example in the volume of the well (V ₂ ), until the required pH is 5.

Dismantle the equipment used to induce the inflow of formation fluid from the well, lower production equipment into the well 2 (not shown in the figure) and run it into operation with the selection of formation fluid from the well.

Implementation of the proposed method will improve the quality and efficiency of the call of formation fluid inflow from the well, the reservoir pressure in which is in the range from 0.8 to 1 from the hydrostatic pressure of the liquid column in the well due to the use of surfactants as foaming agents to impart gas-liquid a mixture (foam) of a stable state, which allows it to maintain a predetermined density during the entire process of calling the inflow from the well, and also because of the possibility of changing the degree of foam aeration their limits with simultaneous monitoring of the change in bottomhole pressure during the inflow call by means of a remote depth gauge. The initial injection of foam to replace the column of well fluid along the tubing string, followed by an inflow by pumping foam into the annulus, minimizes the flow of well fluid into the formation, reduces the negative impact of the well fluid on the formation, reduces the pressure created by the booster unit during the inflow call, and improves efficiency calling the influx of reservoir fluid from the reservoir.

Claims (1)

A method of inducing formation fluid inflow from a well, including lowering a tubing string into a well, reducing the pressure on the producing formation by replacing a column of liquid in the well with a gas-liquid mixture by feeding it with a booster unit, providing the required ratio of the components of the mixture to achieve a given pressure drop on the reservoir, characterized in that at reservoir pressure in the range from 0.8 to 1 hydrostatic pressure of the liquid column in the well before lowering into the well at the bottom end of the tubing set remote depth gauge, after lowering the tubing string into the well produce the liquid column replacement downhole injection into the tubing booster unit liquid mixture - foam of high density, consisting, with low aeration level of surfactant is from 5 to 7 m ³ / m ³ , after which they make a call to inflow formation fluid from the well by supplying a gas-liquid mixture to the annulus of the well with the replacement of high density foam with a foam of lower density and gradually increased The degree of aeration reduces the pressure on the reservoir to a predetermined value, which is controlled by the readings of a remote depth gauge, then, maintaining the achieved pressure, by changing the injection pressure of the booster unit, foam is circulated in a volume equal to the volume of the well, in the presence of an influx of reservoir fluid from the well, replace the foam in the well with a technological fluid with a density that ensures the reservoir properties of the formation, and in the absence of inflow and the formation fluid from the well is stopped, the foam circulation is stopped, the acidity of the formation fluid from the well is determined by sampling for pH, after which the acid composition is pumped and pumped into the formation through the tubing string, the technological pause is maintained for 2-3 hours, after which it is opened the gate valve and repeat the operations described above, while after the process of replacing high-density foam with a foam of lower density, the acidity of the formation fluid from the well is determined by sampling for pH.

Images