RU2433250C1 - Method of oil development by using periodic operation of producer wells with operation portions varying with oil well fluid density variation - Google Patents

Abstract

FIELD: oil and gas production. ^ SUBSTANCE: according to the method, producer wells are operated in a periodic mode. According to the invention, at first a boundary water cut value is specified. A suction running depth below a dynamic well head providing operational changes if observing the dynamic well head to the suction is measured. If the water cut value exceeds the specified boundary value, and the oil well fluid density increases, with underlying decreased dynamic head and operating efficiency of pump, the well is shut down in an accumulation mode for a period of oil crossflow from low-permeability to high-permeability sections of the collector. The production collection time after well start-up is accepted depending on a production water cut value - the oil well fluid density varying with an amount of produced water supplied to the well. ^ EFFECT: reduced amount of produced water and increased oil recovery from watery collectors. ^ 3 dwg

Description

The invention relates to the oil industry and can be used in the development of oil deposits with reservoir pressure, varying within ± 4% during the life of the well, in particular, relates to a method of increasing oil recovery.

The known non-stationary method of periodic operation of horizontal wells (Vasiliev V.I., Zakirov S.N., Krylov V.A. Features of the development of oil-water zones during the periodic operation of horizontal wells. // Oil industry, 2004, No. 5, p. 58-61 ), based on the periodic shutdown of the pumping equipment. When a well is shut down, oil moves to the zones of the reservoir that were occupied by water during well operation, i.e. there is a decrease in the cone of flooding in height. Ultimately, this leads to "a change in the content of the pore medium, and consequently, to a change in the phase permeabilities for reservoir fluids." The method allows to increase the accumulated oil production while reducing the total associated production of produced water.

The disadvantage of this method is the need for prolonged periodic shutdown of deep pumps. The duration of the shutdown is from two weeks to one month. Moreover, according to the authors, the effectiveness of the method decreases with each next cycle, and after the tenth cycle, oil production is markedly reduced with any production method, both stationary and non-stationary. Thus, using the known method, it is impossible to achieve high values of the coefficient of oil recovery from the reservoir.

Closest to the proposed invention is a method of unsteady extraction of oil from the reservoir, in which the exploitation of production wells is performed in a periodic mode, periodic depression is carried out without stopping the submersible downhole pumping equipment. The mode of operation of the latter is selected in the range from the maximum to the minimum flow rates. The maximum flow rate is determined by the consumed electrical power of the pumping equipment at a frequency not exceeding 60 Hz. The minimum flow rate is determined by a decrease in the power consumption of the pumping equipment by 30-40%, but not leading to a stall of fluid extraction at the wellhead. At the same time, the equilibrium filtration mode is periodically restored to reduce the water cut of the produced products to values less than 30%. Ensure the entry of trapped oil into highly permeable pore channels and an increase in average oil production (see ed. St. RF No. 2288352, MKI E21B 43/12, publ. 11/27/2006).

In this case, the time scale of the process of pressure change in the considered area of the reservoir is set by the period of change in the state of the dynamic system, which is not an internal characteristic of the reservoir. It is obvious that the periodic mode of operation of the well does not take into account the effect of changes in the water cut of the production of the well on the operating mode. A well operation mode is possible when, with a decrease from the maximum fluid flow rate to the minimum values, the water cut of the product has not changed and has not reached the minimum values. The well operating mode does not take into account the effect of changes in the water cut of the product, but is determined by the periodic operation of pumping equipment, without taking into account the constantly changing fluid filtration in the reservoir, which in turn requires a daily change in the well operating mode, depending on the processes occurring in the reservoir.

The objective of the invention is to reduce the volume of produced water along the way and to increase the oil recovery factor from flooded reservoirs.

The problem is solved in that the oil production is carried out in a mode in which the duration of the selection periods depends on changes in the density of the wellbore fluid, depends on the volumes of produced water supplied to the well, while for the well, the pump descent depth is determined by calculating the well operating mode change with increasing waterlogging of extracted products.

In the presence of plantar, circulating or injected water during the operation of the well, the near-borehole part of the reservoir is flooded. Well production is flooded, and at some point, the flooding process becomes irreversible. This process is associated with the phase permeability of the fluids. Figure 1 shows that when watering part of the oil-saturated formation above 55%, the phase permeability of the oil is zero. When considering this physical process as a water cut of a well’s production, the boundary water cut of a product for the considered reservoir, in which the water cut process becomes irreversible, is a water cut of more than 60%. With this watering, the near-wellbore zone of the formation becomes hydrophilic, obstructing the movement of oil to the perforation intervals.

The shutdown and periodic operation of the well do not give the desired results due to the untimely adoption of measures to reduce the rate of watering. In this regard, a technology is proposed for the periodic operation of production wells, the period of operation of which varies depending on changes in the density of the wellbore fluid, which allows the well to shut down in time at the moment of increased water cut to reduce water cut of the produced product.

1. For this purpose, in wells with reservoir pressure varying within ± 4% during the period of well operation, the dynamic level of the well (N _dyne ) is determined by calculation with a water cut of 5% lower than the boundary water cut of the considered deposit% _в =% _{in the boundary} - 5 % Then, the pump intake is lowered to the calculated depth N _dyne . A fluid flow rate is established at the well, in which the well works in a constant mode with a water cut of% _in =% _{at the boundary} - 8%. This mode of operation allows the well at lower water cut _in% =% _frontier - 5% operate in a constant mode, wherein the dynamic fluid level above the pump intake is, therefore, a complete filling of a deep well pump. With an increase in water cut in well production up to% _b =% _{at the boundary} - 5%, the density of the produced fluid increases, inflow into the well decreases, therefore, the dynamic level decreases, the pump filling factor changes, a section reflecting the pump filling level appears in the dynamogram the effect of free gas, the well stops in accumulation mode. If necessary, a stationary echo sounder is installed on the well, stopping the well at critical dynamic levels. After a certain interval, which is determined by the recovery curve of the level of the HLE (Khisamov R.S., Khamidullin M.M., Nechval S.V., Galimov I.F., Fazlyev R.T. Processing of the results of hydrodynamic studies of wells draining fractured porous reservoir. // Oilfield business. - M .: VNIIOENG, 2006. - No. 1. - P.21-24), as the time at which the matrix and fracture system and oil flows into the macrocracks of the reservoir interact, the well is put into operation . A production well is operated as long as the water cut is below the boundary water cut of the reservoir in question, but as soon as the well production density increases due to water cut, the inflow decreases, the pump again pumps out the fluid and the well stops. This continues the N number of periods until the density and water cut of the wellbore fluid decreases due to constantly changing periods of well operation, during which oil flows from low-permeable reservoir sections to highly permeable ones. Periodic well operation is graphically as follows (figure 2).

The method is carried out by the following sequence of operations.

1. Using the curve of relative phase permeabilities for oil and water, the boundary water cut of the product for the reservoir under consideration is determined, at which the water flooding process becomes irreversible. In the absence of a curve of relative phase permeabilities, boundary water cut is selected based on field experience of watering wells.

2. In the stationary mode of operation of the well, the oil content of the product and the dynamic level are estimated.

3. Stop the well and record the pressure recovery curve, determine the reservoir pressure and the magnitude of the depression on the reservoir. The formation productivity coefficient is determined, the reservoir pressure is specified.

4. The depth of the descent of the reception of the deep pump is determined.

Where

N _CR - the preliminary depth of the descent of the pump intake, m;

N _SP - the depth of the descent of the pump intake, m;

P _s - annular pressure with a working deep pump, MPa;

P _PL - reservoir pressure, MPa;

Q _W - flow rate, m ³ / s;

k _p - productivity coefficient, m ³ / (c · MPa);

N _cr - the depth of the roof of the reservoir, m;

- удлинение на кровлю пласта, м;

- elongation on the roof of the reservoir, m;

ρ _W - the density of the borehole fluid in reservoir conditions, kg / m ³ ;

- удлинение на глубине Н_пр, м;

- elongation at a depth of H _ol , m;

ρ _n - oil density in reservoir conditions, kg / m ³ ;

ρ _in - density of produced water, kg / m ³ ;

% _{in p} is the boundary water cut, at which the watering process becomes irreversible, the near-well zone of the formation becomes hydrophilic, preventing the movement of oil to the perforation intervals.

5. An underground repair of the producing well is being carried out to lower the downhole pumping equipment to a predetermined depth.

6. Launch a production well and monitor the dynamic level in the development process. When the water production of the well below the calculated dynamic level is higher than the intake of the pump, therefore, with a full filling of the pump. When the water cut of the well’s production is higher than the calculated one, the dynamic level is at the pump intake - the pump filling factor decreases, according to the dynamogram determining the degree of pump filling, a section appears reflecting the effect of free gas, the well is stopped by a stationary dynamograph using the gas factor in accumulation mode. After the estimated time (defined as the time of interaction between the matrix and fracture systems according to the HLF), the controller starts the well into operation, but since the product has an increased density due to flooding, the pump again pumps out the fluid and the well stops. This goes on for N periods, until the density and water cut of the well fluid decrease due to periodic operation (for example, the flow of oil from matrix blocks into the fracture system).

Let us give an example of the implementation of this technology in an oil reservoir with the following characteristics: reservoir type - pore-cavernous-fractured, reservoir mode - water-pressure, porosity - 14.1%, average permeability - 0.145 μm ² , oil saturation - 78.8%, absolute oil-water mark contact - 543 m, average oil-saturated thickness - 8.8 m, reservoir pressure - 7.2 MPa per hl - 543 m, reservoir temperature - 23 ° C, oil density in reservoir conditions - 883.8 kg / m ³ , reservoir density water - 1020 kg / m ^3, viscosity of the oil under reservoir conditions - 52.87 mPa.s pressur e gas saturation oil - 1.3 Mpa, gas content - 4.72 m ³ / t, the sulfur content in oil - 2.6%, content of paraffin oil - 5%. There are no injection wells on the site. The value of the border water cut on the considered deposit is not more than 65%.

; плотность скважинной жидкости при обводненности 65%

, глубина кровли пласта Н_кр=790 м, удлинение на кровлю пласта l_кр=63,7 м. Определяют по кривой восстановления уровня коэффициент продуктивности пласта

и время взаимодействия матричной и трещинной системы Т=9000 с.The necessary data for the well to calculate the depth of the descent of the pump intake: reservoir pressure P _PL = 6.7 MPa; expected annular pressure P _s = 0.2 MPa; continuous pump performance

; well fluid density at a water cut of 65%

, the depth of the formation roof N _cr = 790 m, the elongation on the formation roof l _cr = 63.7 m. The formation productivity coefficient is determined from the level recovery curve

and the interaction time of the matrix and fracture system T = 9000 s.

The preliminary descent depth of the pump is calculated:

=0,1 м на глубине Н_пр=139,9 м.The wellbore inclinometry determines elongation

= 0.1 m at a depth of H _ol = 139.9 m

The production well is equipped with a pump 25-175-RHAM-22-10-2-2, lowered to a depth of 130 m, pump intake at a depth of 140 m, i.e. at a depth with an “optimal depression” on the formation and water cut of the product is 5% lower than the boundary water cut of the considered deposit.

In order to constantly determine the pump fill factor during operation, the well is equipped with a stationary dynamograph for taking dynamograms.

The results of the well are shown in figure 3. When the water content of the well’s production is below 65%, the well works in a constant mode. With an increase in water cut in well production above 65%, the dynamic level decreases due to an increase in the density of the borehole fluid, the pump filling factor decreases, a sticking occurs on the dynamogram determining the pump’s performance, and the well stops in accumulation mode T = 9000 s. After T = 9000 s, at which the matrix and fracture system and oil flow into the macrocrack of the reservoir interact, the well is put into operation. This continues the N number of periods until the density, respectively, of the water cut in the well fluid decreases due to the ever-changing periodic operation of the well, during which oil flows from microcracks to macrocracks in the formation.

Claims (1)

A method for developing an oil reservoir with unsteady extraction of oil from the reservoir, in which the production wells are operated in a batch mode, characterized in that the boundary value of the water cut is initially set at the boundary, the depth of the pump intake is lower than the dynamic level in the well, which ensures a change in the operating mode with a decrease in the dynamic level before receiving the pump, when the water cut of the product changes above the established boundary water cut and the well density increases fluid, from decreasing the dynamic level and decreasing the pump filling factor, the well is stopped in the accumulation mode for the period of oil flow from low-permeability sections of the reservoir to highly permeable ones, while the duration of the production sampling after the start-up of the well is taken depending on the amount of water cut in the product-density of the well fluid, varying from the volume of produced water entering the well.

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