RU2021497C1 - Method for increase of intake capacity of injection wells - Google Patents

Abstract

FIELD: oil producing industry. SUBSTANCE: injected through injection well is magnetized water in volume equalling pore space of bottom hole formation zone. Water is magnetized by its passing through lateral magnetic field with intensity of 3,7·10³-4,3·10³A/m A.m. After injection of water, it is left to stand until capillary impregnation of fine pores and pressure in well is increased and decreased many times. Magnetized water reduces swelling of clays and promotes increase of formation permeability. In combination with pressure increase and decrease, magnetized water penetrates into capillary pores of reservoir. EFFECT: higher efficiency. 4 dwg

Description

 The invention relates to the oil industry and can be used for processing bottom-hole formation zone.

 The aim of the invention is to increase the efficiency of the method.

 In a method for increasing the injectivity of injection wells, which consists in the injection of magnetized water, the injection of magnetized water is carried out in the bottomhole zone, technological exposure is performed until capillary impregnation of small pores is made, the pressure in the well is repeatedly increased and decreased each time until the front of the change in the pressure of the injection front is reached, cycles from the injection of magnetized water to the last pressure change is repeated until the increase in injectivity of the well stops.

 The need to improve the filtration properties of the formation based on hydrodynamic studies of pressure recovery in the well is associated with a decrease in the well productivity coefficient, lowered permeability of the formation in the near-wellbore zone, low coverage of the formation by injection along its thickness, etc.

 It is possible to compensate for these shortcomings by treating injection wells with magnetized water during a cyclic change in the injection pressure. Bottom-hole action on the bottom-hole zone is a method of cyclically changing the injection pressure in the well.

It was experimentally established that the magnitude of the magnetic field has an effect on injectivity. With an increase in tension to 2 ˙ 10 ³ A / M, the injectivity increases, after which a slight decrease is observed and, further, with a value of 3.7 ˙ 10 ³ A / M, growth again, and at 4.3 ˙ 10 ² A / M the process is stabilizing.

 In FIG. 1 shows the dependence of injectivity (volumetric filtration rate) on the magnitude of the magnetic field strength; in FIG. 2 - dependence of the change in the volumetric filtration rate; in FIG. 3 - dependencies of the injectivity of the well on the injection pressure during the injection of water; in FIG. 4 is a graph of pressure change until the front of the change in pressure of the injection front is reached.

Water passing through a transverse magnetic field of intensity 3.7 ˙ 10 ³ - 4.3 ˙ 10 ³ A / m is pumped into the bottom-hole zone in a volume
V = π ˙ m ˙ K _b ˙ h _e ˙ R ₂ , m ³ , where V is the minimum required volume of the process fluid, m ³ ;
m is the porosity of the reservoir, in fractions of a unit;
K _b - oil displacement coefficient;
h _e - effective reservoir thickness, m;
R is the radius of the bottomhole formation zone, m

 Magnetized water is injected into the formation at the maximum injection pressure of the well, taking into account the design characteristics of the production string and to prevent violations of the tightness of the separation of the layers of cement.

 When moving in a porous medium, a potential difference (leakage potential) occurs, which prevents the flow of liquid.

 To reduce the leakage potential, it is necessary that a change in the structure of water occurs due to repackaging of charged particles, and this is possible when Lorentz forces act on electrical particles. It is known that Lorentz forces arise when magnetic particles cross magnetic lines, i.e. when water flows through a transverse magnetic field.

м/с, где R =

- радиус поровых каналов, м;
α - коэффициент поверхностного натяжения воды на границе с породой, Н/М;
η - вязкость воды в пластовых условиях, Па ˙ с;
l₁ - характерный размер низкопроницаемых включений, м;
K - проницаемость, м²;
m - пористость, доли единицы.After this, technological endurance is performed, the purpose of which is to impregnate the capillary pores of the bottomhole zone to improve the reservoir properties of the formation — to reduce the swelling of clays and increase the permeability of the reservoir. The technological exposure time is determined by the time of impregnation of the pores and is as follows. According to the Poiseuille formula, the impregnation rate is
V =

m / s, where R =

- radius of pore channels, m;
α is the coefficient of surface tension of water at the boundary with the rock, N / M;
η — viscosity of water in reservoir conditions, Pa ˙ s;
l ₁ - characteristic size of low permeability inclusions, m;
K - permeability, m ² ;
m - porosity, fractions of a unit.

=

с,
По истечении времени проведения технологической выдержки снижают давление нагнетания на 10-20% , снова производят технологическую выдержку и затем увеличивают давление нагнетания до максимально-возможного значения. Количество таких циклов выбирается исходя из времени распространения волны давления в пористой среде. Скорость распространения волны давления в пористой среде определяется пьезопроводностью κ.Тогда время распространения волны, соответственно время проведения циклов баровоздействия определится по формуле
T =

с, где l - расстояние от скважины до фронта заводнения.The technological exposure time - the time of impregnation of the pore space with magnetized water is determined by the formula
τ =

=

with,
After the time of the technological exposure, the discharge pressure is reduced by 10-20%, the technological exposure is again performed and then the injection pressure is increased to the maximum possible value. The number of such cycles is selected based on the propagation time of the pressure wave in the porous medium. The velocity of propagation of a pressure wave in a porous medium is determined by the piezoconductivity κ. Then, the wave propagation time, respectively, the time of the bar exposure cycles is determined by the formula
T =

c, where l is the distance from the well to the waterflooding front.

число циклов.The number of cycles n is defined as
n =

number of cycles.

 After n cycles of bar impact, the injectivity of the well is measured and the entire process described above is repeated. Magnetized water is again pumped, maximum discharge pressure is created, and technological exposure is performed. Relieve pressure by 10-20%, again produce technological endurance, raise the pressure to the maximum possible value, etc. At the end of the bar impact cycles, the injectivity of the well is measured. Magnetized water injection cycles are carried out until the injectivity of the well acquires a constant value. A 10-20% reduction in injection pressure is produced from the maximum injection pressure, moreover, this pressure is selected taking into account the design characteristics of the production casing and to prevent violation of the tightness of the separation of the layers of cement. As a result of laboratory studies on the reservoir model, it was found that the effectiveness of the effect of a cyclic change in the discharge pressure of magnetized water depends on the magnitude of the decrease in the injection pressure during the injection (on the amplitude of the cycle).

When the amplitude of the cycle (0-20) P _max from the maximum discharge pressure Pmax, the impact efficiency increases. A further increase in the amplitude of the cycle does not affect the increase in injection efficiency. In fig. Figure 2 shows the dependence of the change in the volumetric filtration rate, q, of the relative pressure change Δ P / P, (Δ P = P _max -P). The dependence curve shows that the maximum effect of the injection of magnetized water into the reservoir in combination with cyclic changes in pressure is achieved when Δ P / P = (10-20)%.

 Comparative studies of the change in the pressure of the discharge of magnetized water in combination with the bar effect, with continuous injection of magnetized water and injection of water with the addition of surfactants, have been carried out.

In FIG. Figure 3 shows the dependences of the injectivity of the well on the injection pressure when injecting water with a surfactant additive — curve 1, for continuous injection of magnetized water — straight line 2, for cyclic injection of magnetized water with changes in injection pressure, straight line 3. Segments G ₁ , G ₂ , G ₃ on FIG. 3 values of the initial pressure gradient, respectively, for water injection with the addition of surfactants, with continuous injection of magnetized water, with cyclic injection of magnetized water (i.e., water injection combined with bar action). From those shown in FIG. 3 dependencies shows that the injection rate (the tangent of the slope of the lines 1,2, 3 - α ₁ , α ₂ , α ₃ ) for cyclic injection of magnetized water will be higher than α ₃ , α ₂ , α ₁ , the initial pressure gradient, from which depends on the filtration rate will be less than G ₃ <G ₂ <G ₁ . The pick-up during the injection of magnetized water in combination with bar action will be greater than with the continuous injection of magnetized water or water with the addition of surfactants.

=

^p

где

- вектор скорости фильтрации, м/с,
К - проницаемость, м²;
η - вязкость воды, Па ˙ с;
G_o - начальный градиент давления, Па/М.It is known that water filtration in clayed reservoirs occurs with an initial pressure gradient so that the filtration law has the form

=

^p

Where

is the filtration rate vector, m / s,
K - permeability, m ² ;
η is the viscosity of water, Pa ˙ s;
G _o - initial pressure gradient, Pa / M.

Obviously, if the value of G _o is large enough, then the filtration rate is low. With a decrease in G _o , even with constant permeability, the filtration rate and, consequently, the injectivity of the well will increase.

 Magnetized water reduces the swelling of clays and helps to increase the permeability of the formation. The combination of magnetized water injection with bar effect, i.e., cyclic changes in the injection pressure, allows magnetized water to penetrate into the capillary pores of the reservoir, connecting previously unreached by interlayers, thereby increasing the injectivity of the well.

 In FIG. Figure 4 shows a graph of the pressure change until the front of the change in pressure of the injection front is reached. On the graph, the value of τ denotes the time of technological exposure - the time of impregnation of the pores, T - the time of the cycles of bar exposure, corresponding to the time of wave propagation. The injection rate, and, in fact, the filtration rate is determined according to the schedule through the slope of the straight lines 1,2,3, characterizing the throttle response over time. The graph shows the entire process of the method.

To implement the method, well N 9268 was selected. The injectivity of the well was 525 m ³ / day, bottom pressure R _zab = 16.0 MPa, reservoir thickness N = 12 m, distance from the well to the injection front l = 4 m, piezoelectric conductivity κ = 0.001 m ³ / s.

Using a pumping unit, on the flow line of which a magnetic device is installed, water is pumped. For the injection, the AKPP-500 unit was used, on the flow line of which, after the pump, a special device is installed, consisting of a branch pipe (tubing tubing with a diameter of 73 mm). Within manifold mounted rod of a nonmagnetic material disposed thereon permanent magnet tension 3,7 ˙10 ³ -4,3 ˙ March ¹⁰ A / M. The magnets face the poles of the same name; insulators made of non-magnetic material are placed between the magnets. Unit capacity at a pressure of 16.3 MPa is 26.4 m ³ / h.

The amount of magnetized water injected is determined as follows:
V = 2 ˙q ˙H where q is the specific consumption of magnetized water, choose equal to 0.7 m ³ / m;
N - reservoir thickness - 12 m;
V = 2 ˙ 0.7 ˙ 12 = 16.8 m ³ .

=

=0.6 ч
V - объем воды для закачки 16,8 м³;
q_н - производительность насосного агрегата 26,4 м³/ч.Magnetized water injection time will be
t _zak =

=

= 0.6 h
V is the volume of water for injection of 16.8 m ³ ;
q _n - the productivity of the pumping unit 26.4 m ³ / h

=

·

=

·

= 800 с , где l₁ - характерный размер низкопроницаемых включений;
l₁ = 1-10 см;
К - проницаемость коллектора; К = 10^-9;
m - пористость коллектора; m = 0,2;
η - вязкость воды в пластовых условиях, η = 0,1.Magnetized water is pumped at a pressure of 20 MPa, after which technological exposure is carried out. The exposure time is determined by the time of impregnation of pores, a decrease in the swelling of clays and is determined as follows:
τ =

=

·

=

·

= 800 s, where l ₁ is the characteristic size of low permeability inclusions;
l ₁ = 1-10 cm;
K is the permeability of the reservoir; K = 10 ^-9 ;
m is the porosity of the reservoir; m = 0.2;
η is the viscosity of water in reservoir conditions, η = 0.1.

 After the time of technological exposure, the pressure in the well is reduced by 20%, i.e. up to 12.8 MPa and produce technological exposure equal in time to 800 s. Raise the discharge pressure to the maximum possible, i.e. up to 20 MPa and produce a technological exposure of 800 s. Then depressurize by 20% and produce technological exposure.

=

= 4000 с , где l - расстояние от скважины до фронта закачки, l = 4 м;
χ - пьезопроводность, χ = 0,001 м³/с.The creation of the maximum possible discharge pressure, holding technological exposure, depressurization and again holding technological exposure is one cycle of bar exposure of magnetized water to the bottomhole zone. The number of cycles depends on the time the wave travels in the porous medium to the waterflooding front. Define this time
T =

=

= 4000 s, where l is the distance from the well to the injection front, l = 4 m;
χ is the piezoconductivity, χ = 0.001 m ³ / s.

 The time of each cycle includes two technological excerpts, the time of raising the discharge pressure to the maximum possible and the discharge time. Since the time for holding technological exits is much longer than the time for raising the discharge pressure and the discharge time, when determining the number of cycles, the calculation is based on the time for holding the technological excerpts. Thus, in our case, the number of cycles is determined as follows.

= 2.5 ≈ 3
Следовательно по истечении трех циклов волна движения омагниченной воды в пористой среде достигнет фронта заводнения, в связи с чем изменится приемистость скважины. Производится замер приемистости скважины и определяется, что она составляет 538 м³/сут. Далее повторяют процесс закачки омагниченной воды в пласт по вышеописанному способу и вновь замеряют приемистость. После проведения еще трех циклов баровоздействия на пласт приемистость увеличилась до 553 м³/сут. Затем вновь повторяют описанный выше процесс и вновь замеряют приемистость скважины до тех пор, пока значение приемистости увеличивается. Способ прекращается тогда, когда при повторении циклов баровоздействия, значение приемистости не окажется постоянным. В результате баровоздействия омагниченной воды на призабойную зону пласта приемистость нагнетательной скважины N 9268 куст 1137б возросла с 525 м³/сут до 570 м³/сут, увеличение суточной приемистости составило 45 м³/сут. В качестве прототипа выбран способ закачки омагниченной воды в пласт (без баровоздействия), который был осуществлен на скв. N 16416 куст 1101. В результате приемистость скважины увеличилась с 360 м³/сут до 380 м³/сут и увеличение суточной приемистости составило 20 м³/сут.n _cycle =

= 2.5 ≈ 3
Therefore, after three cycles, the wave of magnetized water in the porous medium reaches the waterflooding front, and therefore the injectivity of the well will change. A well injectivity is measured and it is determined that it is 538 m ³ / day. Next, the process of pumping magnetized water into the reservoir is repeated according to the method described above and the injectivity is measured again. After three more cycles of bar impact on the formation, the injectivity increased to 553 m ³ / day. Then, the process described above is repeated and the injectivity of the well is measured again until the injectivity value is increased. The method stops when, when repeating the cycles of bar exposure, the value of injectivity is not constant. As a result of the bar effect of magnetized water on the bottom-hole zone of the formation, the injectivity of the injection well N 9268 bush 1137b increased from 525 m ³ / day to 570 m ³ / day, the increase in daily injectivity was 45 m ³ / day. As a prototype, the selected method of injection of magnetized water into the reservoir (without bar impact), which was carried out at the well. N 16416 bush 1101. As a result, the injectivity of the well increased from 360 m ³ / day to 380 m ³ / day and the increase in daily injectivity was 20 m ³ / day.

Thus, the increase in daily injectivity in the well, where during the injection of magnetized water was performed bar impact on the bottomhole formation zone compared to the prototype was 25 m ³ / day, the flow rate of five neighboring producing wells increased by an average of 8 m ³ / day. For three months after the bar impact on well N 9268, bush 1137b, additional production amounted to 3835 m ^{3 of} oil.

Claims (1)

METHOD FOR INCREASING THE ACCESSIBILITY OF INJECTIVE WELLS by injection of magnetized water, characterized in that, in order to increase the efficiency of the method, water is magnetized by passing water through a transverse magnetic field of intensity 3.7 · 10 ³ - 4.3 · 10 ³ A / m, magnetized water is pumped in a volume equal to the pore volume of the bottomhole zone, after which technological exposure is carried out until capillary impregnation of small pores, repeatedly increase and decrease the pressure in the well until the front of the pressure change reaches the front This injection, until the cessation of the increase in injectivity of the well, after which the cycle is repeated from the moment of injection of magnetized water.

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