RU2778117C1 - Method for vibro-wave action in order to restore the productivity of wells with hydraulic fracturing - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the oil and gas industry, namely to methods of vibro-wave action on the downhole zone of the reservoir by elastic wave vibrations of the working fluid and can be used at injection and production wells with various technological operations. A method for vibro-wave action on a well with hydraulic fracturing, according to which a wave hydraulic monitor located at the end of the tubing is lowered into the perforation interval. The working fluid is pumped into the tubing and a traveling pressure wave with a frequency of 2 Hz is created through the specified wave hydraulic monitor. The hydraulic monitor is moved along the perforation interval with a continuous supply of working fluid and a step-by-step treatment of the perforation interval is carried out with the resulting field of low-frequency traveling waves. In this case, the particles of the destroyed contaminants are transferred by the flow of the injected working fluid through the cleaned fractures of the hydraulic fracturing deep into the formation and dispersed beyond the proppant pack. The remains of particles in the downhole zone are dissolved with chemical compositions in a vibro-pulse mode with the implementation of measures for the development of the well.

EFFECT: increase in the efficiency of cleaning the proppant crack of the oil reservoir from contamination.

1 cl, 6 dwg

Description

The invention relates to the oil and gas industry, and in particular to complex methods of influencing the near-wellbore formation zone with elastic vibro-wave oscillations of a working agent with high amplitudes and low frequencies to restore or increase the productivity of wells located in a formation that is heterogeneous in permeability with fractures formed by hydraulic fracturing (HF). It can be used on injection and production wells with vertical, flat and horizontal wellbore with various technological operations (interval hydro-wave impact, chemical treatments, development with induction of inflow from the reservoir, etc.), in conditions of insufficient or impaired fracture conductivity after hydraulic fracturing, volumetric contamination of cracks with various kinds of sludge, drilling products, destroyed proppant, deposits of resins, paraffins, salts, mechanical impurities during well operation.

There is a known method of treating a near-well formation zone using pressure pulses in the well fluid, which are used to form new cracks in rocks for the development of filtration channels in order to increase oil recovery (Patent for the invention RU 2209960 C2, 10.08.2003. Application No. 2001101664/03 dated 17.01 .2001). The disadvantage of this technical solution is the low efficiency of the transformation of the structure of the rocks of the formation due to the disposability and low controllability of the impact. The main goal of the conversion - cleaning the pore medium in the most contaminated areas of the formation and reducing the concentration of particles that clog it - is not achieved, the intensity of the impact is ensured by an increase in the amplitude of pressure pulses, as a result of which auto-fracturing occurs, and the resulting fracture channels go into unproductive and watered zones , which can lead to premature watering of well production.

Known methods of vibratory treatment of a productive formation for cleaning existing filtration channels, developing existing cracks, flushing them with the removal of contaminants and reaction products to the surface, including periodically recurring hydrodynamic monitoring of the near-well zone, followed by correction of the processing mode [RU 2191896 C2, 27.10.2002, RU 2478778 C2, 04/10/2013]. The effectiveness of the technical solution in the methods is not high enough due to the low coverage factor of the impact both in thickness and along the strike of the formation (deposit area). The removal of contaminants and reaction products is carried out to the surface, the duration of the effect is short-term.

It is also known downhole equipment for treatment near the wellbore formation zone [RU 140463 U1, 05/10/2014], including a wave monitor installed at the end of the tubing at the level of the perforation interval and hydraulically connected to the injection line, converting the uniform movement of the fluid into a pulsating one and moving along perforation interval for the most effective exposure and cleaning of perforations.

The closest analogue in technical essence is the method of treating the near-well zone of an injection well with high-frequency standing waves in order to delay particles of a water-insulating sediment-forming reagent, for example, gel particles, in the near-wellbore zone, their coagulation and swelling during the delay time to create water-insulating barriers and block the washed areas of the oil formation [RU 2447273 C1, 10.04.2012].

As a result of the impact in the method, the water flows are redistributed into small slots in order to equalize the front of the injected water only in injection wells, production wells are not considered.

This technical solution is not effective enough, since it is used to limit the migration of particles in highly permeable areas of the reservoir, including large fractures formed by hydraulic fracturing, to the standing wave attenuation distance, with the exception of their further movement towards the production well. The method is directed to the wellbore zone of the injection well and allows you to control the propagation distance of water-insulating reagent particles, for example, particles of the gel system.

In contrast to the prototype in technical essence, a method is proposed in which elastic waves can control the concentration of fine particles that clog the near-wellbore zone, proppant fractures from hydraulic fracturing in production wells.

The technical objective of the invention is to develop a method of vibro-wave action in order to clean the proppant fracture of the hydraulic fracturing of the oil reservoir from contamination, aimed at reducing the concentration of fine particles-colmatants in the near-wellbore zone of the production well by moving them deep into the reservoir and dispersing through the high-permeability channels of the hydraulic fracture under the action of pressure pulses of low frequencies created by a generator, for example, a hydromonitor, with additional processing in the vibrowave mode by chemical compositions to dissolve the remaining contaminants.

In the implementation of the invention, the problem is solved by restoring the productivity of wells with hydraulic fracturing by creating a pressure gradient of alternating direction in the near-wellbore zone by low-frequency pulses of an elastic wave created by a hydraulic monitor. When this occurs, separation from the rock skeleton and the movement of particles of contaminants along the channels of the crack from the perforations into the depth of the formation with dispersion outside the impact zone.

The specified technical result is achieved by the fact that the method of vibration-wave restoration of the productivity of wells with hydraulic fracturing involves the following operations:

– at the bottom of the well in the perforation interval on the tubing (tubing) a wave hydromonitor is lowered, located at the end of the tubing,

– they inject the working fluid (water, oil, acids, alkalis, etc.) through the swivel into the tubing and through the hydraulic monitor to create elastic oscillations of the jet pressure and obtain a wave field of low-frequency traveling waves in the near-wellbore zone in the porous medium of the hydraulic fracture proppant pack,

– move the hydraulic monitor along the perforation interval with continuous supply of working fluid to the tubing to change the area of vibrowave action,

at the same time, under the action of large fluid velocity and pressure gradients of variable direction in the near-wellbore zone, the solid particles of the bridging agent are transferred from a monolithic to a suspended state,

at the same time, the blockades of contamination of perforations, the near-wellbore zone, and in the proppant pack are destroyed,

at the same time, solid particles of destroyed contaminants in suspension migrate in large cracks in the direction from the treated area into the depth of the formation, disperse along the hydraulic fracture,

at the same time, the concentration of solid particles in the near-wellbore zone and the zone of the adjacent reservoir decreases, its filtration properties are restored, the proppant pack fracture conductivity is restored, and the well productivity is increased.

The method differs in that not a standing, but a traveling pressure wave is used to influence the particles, the migration of particles is directed deep into the formation, the distance of particle migration is controlled with a decrease in their concentration in the near-wellbore zone.

The method can be applied to injection and production wells with a vertical, flat and horizontal wellbore with various technological operations (interval hydrowave impact, chemical treatments, development with a call to inflow from the reservoir, etc.).

After using the vibration wave action with the working fluid over the reservoir with the dispersion of contaminated particles outside the proppant pack, it is recommended to perform a vibration wave action with chemical compositions to dissolve the remaining contaminant particles with subsequent development of the well.

A comparative analysis with the prototype shows that in the claimed method, using low-frequency traveling waves created by a hydraulic monitor in a production well, solid particles of bridging agents are destroyed and move deep into the formation along the hydraulic fracture, which leads to a decrease in the concentration of pore space contaminants and the opening of filtration channels along the entire length impact, accompanied by an increase in well productivity.

Comparison of the claimed technical solution with other technical solutions shows that methods of influencing the near-wellbore zone of producing wells in order to clean them to increase oil recovery are known.

However, it is not known that in order to reduce the concentration of bridging agents in wells with hydraulic fracturing, using vibration wave action, it is possible to change the direction of migration of polluting particles, moving them deep into the formation, dispersing them along the proppant pack, instead of extracting the treatment products in the direction from the formation to the well. The result of the unidirectional movement of particles is a decrease in their concentration in the near-wellbore zone, accompanied by the opening of filtration channels, which will increase their permeability, increase conductivity and restore well productivity.

The invention is illustrated by the following illustrative materials.

In FIG. 1 shows: 1 - perforation interval at the level of the reservoir, 2 - wave hydromonitor, 3 - annulus between the production string of wells and tubing, 4 - tubing, 5 - hydraulic flexible hoses connecting the annulus with topping tank 10, 6 - swivel suspended on hook block 7 of the traveling system, tubing 4 hanging on the swivel, 8 - hydraulic flexible hoses connecting topping tank 10, pumping unit TsA-320 9 and swivel 6. Arrows show the direction of fluid under pressure along tubing 4 to hydro monitor 2.

In FIG. Figure 2 shows pressure pulses of a hydraulic monitor with a frequency of 2 Hz, an amplitude of 8 MPa, and a duration of 0.24 s, obtained to create a vibration wave effect on the perforation area in order to destroy the structure of the bridging agent layer and move particles deep into the formation.

In FIG. Figure 3 shows the nomograms of the involvement of particles with radii of 0.2 - 2 mm in wave motion with different frequencies of exposure to select the optimal frequency of the hydromonitor.

In FIG. 4 shows the change in the coordinates of particles with radii of 0.3 and 0.7 mm as they move from the well during the action of the pressure pulse of the hydromonitor shown in FIG. 2: the particle R = 0.3 mm completely follows the traveling wave, the particle R = 0.7 mm is more inertial, so its motion is smoother.

In FIG. 5 shows the results of pressure and temperature monitoring with a downhole pressure gauge in a production well with hydraulic fracturing during the implementation of the vibrowave method.

In FIG. Figure 6 shows an example of the results of testing the method of vibration exposure in order to increase the productivity of wells with hydraulic fracturing by controlling the concentration of bridging agents in the near-wellbore zone.

To solve the technical problem, it is proposed:

- the presence of low-frequency pressure fluctuations in the form of rectangular pulses ( f = 2 Hz), created by the monitor 2 (figure 1), located at the end of the tubing 4 (figure 1);

- obtaining using hydraulic pulses (figure 2) field of traveling waves in the interval (zone) perforation 1 (figure 1);

- directed action of the field of traveling waves on the fluid inside the reservoir and particles deposited and adsorbed by the surface of the skeleton;

- violation of the structure of the bridging layer under the influence of the shearing action of the traveling wave with the separation of solid particles of bridging agents with the formation of a suspension;

- migration of suspended particles with liquid in the direction of the pressure gradient from the near-well zone into the formation;

- reducing the concentration of polluting particles in the near-wellbore zone, distributing them along the entire length of the reservoir section covered by the impact, increasing the permeability of its pore structures, restoring well productivity.

Let us show the possibility of using the wave field of pulses of a hydromonitor to influence polluting particles with typical radii of 0.3-0.8 mm.

Impact on fine particles in a traveling wave.

Let the fluid move in the field of a plane traveling wave, and the fluid moves at a speed V ( m/s)

V = V ₀ cos ωt,

where: V ₀ – fluid velocity amplitude, m/s;

ω – cyclic frequency, rad/s;

t is time, s.

м/с относительно неподвижного наблюдателя. На частицу в жидкости действует сила вязкого трения или сила Стокса F _СТ (Н):The particle is moving at a speed

m/s relative to a stationary observer. The viscous friction force or the Stokes force acts on a particle in a liquidF _ST (N):

where: η is the dynamic viscosity of the fluid, Pa/s;

R is the particle radius, m.

According to Newton's 2nd law

ma = F _st , (2)

where: m – mass, kg;

a - acceleration, m / s ² .

Solving together (1) and (2), we obtain the formula for the dependence of the particle coordinate on time:

where: X _t is the coordinate of the particle in the studied period of time, m;

X ₀ -the initial coordinate of the particle, m;

X _a is the particle oscillation amplitude, m;

φ – initial phase, rad.

в формуле (3) затухает, остаётся колебательное движение частицы вместе с жидкостью около точки с координатой Х ₀.Expression

in formula (3) decays, the oscillatory motion of the particle remains together with the liquid near the point with coordinate X ₀ .

The oscillation amplitude of the particle X _a (m) is equal to

where R is the particle radius, m;

ω – cyclic frequency, rad/s;

m is the particle mass, kg,

m = 4/3 π ρR ³ ,

where π = 3.14;

ρ is the particle density, kg/m ³ .

The degree of participation of the particle in the wave motion is estimated by the method in accordance with the prototype using the dimensionless coefficient α :

where X _W is the amplitude of the liquid oscillation, m;

f —frequency, Hz;

– безразмерный комплекс.

is a dimensionless complex.

The coefficient of participation of the particle α in the wave motion increases with decreasing particle radius R , decreasing the frequency of the wave action f.

According to formula (5), graphs were plotted showing the degree of impact (coefficient α ) on particles of different sizes by wave fields of different frequencies (Fig. 3) and it was concluded that the most effective is the effect on particles of colmatant 0.3 ... 0.8 mm by a traveling wave frequency 2 Hz.

The dimensions of the vibration zone x (m) according to the formula (Gadiev S.M. The use of vibration in oil production. M., Nedra, 1997, 159 p.)

where χ is the coefficient of piezoconductivity m ² /s;

k – formation permeability, m ² ;

ϕ – porosity, units;

η is the dynamic viscosity of the fluid, Pa s;

β _L – liquid compressibility coefficient, Pa ^-1 ;

β _S – skeleton compressibility coefficient, Pa ^-1 ;

f is the pressure wave frequency, Hz.

According to (6), the impact depth can be controlled by changing the wave frequency depending on the reservoir parameters.

Calculation of the dimensions of the vibration impact zone according to formula (6) for a traveling wave with a frequency of 2 Hz and a formation with parameters φ = 0.15, η = 0.001 Pa⋅s, β _L = 4.28 10 ^-10 Pa ^-1 , β _S = 2, 04⋅10 ^-10 Pa ^-1 , f = 2 Hz, k = 150⋅10 ^-12 m ² (corresponds to a fracture in a hydraulic fracturing proppant pack) shows a treatment depth of 16.7 m.

According to the above provisions of the physical essence, the impact on the particles of bridging agents in the proppant crack of the oil reservoir is achieved in order to disperse them outside the proppant pack and reduce their concentration in the near-wellbore zone.

An example of the implementation of the method

To carry out the operations of the method of vibration-wave impact on the near-wellbore zone of the reservoir, a production well with hydraulic fracturing with a productivity of 12 m ³ /day, an oil production volume of 1.3 m ² /day, a water cut of 90% and a productivity factor of 0.06 was selected. Initial bottomhole pressure is 12.3 MPa.

On the tubing string, a wave jet monitor (which, for example, can be used as a wave jet according to utility model RF No. 139424) was lowered to the bottom of the well in the perforation interval. An ACM-4 deep manometer-thermometer was placed on the side surface of the tubing.

Created a hydraulic circuit, connecting the annulus with hydraulic hoses to the topping tank, the pump unit CA-320 9 and the swivel with the supply of the working fluid through the tubing to the monitor (figure 1).

Measuring devices were connected to register wellhead pressures and flow rates in the injection and discharge lines (ultrasonic flow meter Akron-01).

Created a pressure of the working fluid - water with the addition of surfactants (neonol) at the mouth at the outlet of the pumping unit 15 MPa with a flow rate of the working fluid of 9 l / s with circulation through the hydraulic circuit through the hydraulic monitor.

In the hydraulic monitor, the translational motion of the working fluid was converted into elastic pulse oscillations with a frequency of 2 Hz and an amplitude of 8 MPa (Fig. 2).

Conducted vibro-wave action by moving the hydraulic monitor along the perforation interval through 30-40 cm with continuous supply of working fluid to the tubing with the creation of circulation into the annulus. During the exposure time, no circulation was observed at the wellhead; the working fluid was absorbed into the formation. There are processes of destruction of the structure of bridging agents and migration of particles together with the liquid into the depths of the formation.

4 hours after the start of the cycle, liquid circulation appeared at the wellhead with the manifestation of an oil-gas fountain, the flowing lasted 2 hours, which proves the cleaning and opening of filtration channels in the near-wellbore zone.

After 16 hours, acid treatment was performed by pumping hydrochloric acid through a hydraulic monitor in a volume of 8 m3 at a pressure of 16 MPa to dissolve the remaining contaminants.

To extract the reaction products, the well was completed by swabbing.

We completed the final work on the extraction of downhole equipment and putting the well into operation.

Figure 5 presents the results of pressure and temperature monitoring obtained during the implementation of the method.

The dynamics of operational performance of an unprofitable well with the conducted method of vibro-wave action is shown in Fig.6.

Before the method:

- liquid flow rate Q _W was 12 m ³ /day,

- the volume of oil Q _n not more than 1.3 m ³ / day,

- water cut of products % _vol = 90%,

- productivity coefficient K _prod = 0.06.

After carrying out a set of measures for vibration-wave processing, the performance indicators have changed as follows:

- liquid flow rate Q _w increased to an average level of 50 m ³ / day,

- the volume of oil Q _n increased to 10 m ³ / day,

- water cut of products % _rev decreased to 75%

- productivity coefficient K _prod increased to 0.5

Within six months after the application of the vibration wave method, additional oil production amounted to 630 tons, the profit from the implementation amounted to 3.5 million rubles.

Claims (1)

A method of vibro-wave impact on a well with hydraulic fracturing, characterized in that a wave hydraulic monitor located at the end of the tubing is lowered into the perforation interval, the working fluid is injected into the tubing and a traveling pressure wave with a frequency of 2 Hz is created through the specified wave hydraulic monitor , move the hydraulic monitor along the perforation interval with continuous supply of the working fluid and carry out a stage-by-stage processing of the perforation interval by the obtained field of low-frequency traveling waves, while the particles of destroyed contaminants are transported by the flow of the injected working fluid along the cleaned hydraulic fractures deep into the formation and disperse beyond the proppant pack, and the remains of the particles into in the near-wellbore zone, they are dissolved with chemical compositions in a vibro-pulse mode with well development activities.

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