RU2525244C1 - Method of decreasing oil producing well watering - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: in compliance with this method, well is shut in to open casing and linear gate valves for pumping highly mineralised water into annular space. Casing valve is closed to release excess pressure for pumping of highly mineralised water into seam in preset amount at 7.5-10.0 MPa. Pumping is stopped to close the well and to level the pressure for uniform distribution of highly mineralised water in the seam water-flooded zone. Well is started to run it to constant duty for up to 5 days. Well is operated at seam depression of 0.5-1.5 MPa. Volume of injected highly mineralised water is defined by analytical expression.

EFFECT: higher efficiency.

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Description

The invention relates to the oil industry and may find application in works to reduce water cut in oil production wells.

There is a method of preventing sand removal and reducing water inflow in producing oil wells, including heating the bottom-hole zone of the well to a temperature of at least 30 ° C, injecting an anhydrous oil rim, injecting an aqueous solution of calcium chloride (calcium chloride) with a density of at least 1500 kg / m ³ , pushing this solution into the reservoir with fresh water, forming a filter by pumping 25-30% suspension in the hydrocarbon phase of powdered calcium chloride with the addition of 5-25% weight. reagent (RDN) for oil production (RF patent No. 2164589, IPC E21B 43/08, publ. 03/27/2001).

The disadvantage of this method is that the reduction in water gain is achieved by plugging the water supply paths with crystals of calcium chloride, precipitating from an aqueous solution of calcium chloride due to a decrease in solubility with a decrease in temperature. These crystals are subject to dissolution by the water contained in the reservoir, and the effect of such work is usually short-lived.

Closest to the proposed invention in technical essence is a method of isolating water inflow zones in a well, including pumping an aqueous solution of calcium chloride, heated to a temperature of 70-90 ° C, with a density of at least 1500 kg / m ³ , carrying out technological exposure for 8-12 h, injection of a rim of hydrocarbon liquid and glass of liquid sodium heated to a temperature of 70-90 ° C and holding for 24-48 hours to form a gel in the entire volume of liquid sodium glass (RF patent No. 2494229, class E21B 33/138, publ. 09/27/2013 - prototype).

The disadvantage of the prototype is the complexity of the process, and in most cases the impossibility of its reproduction, due to the fact that at the slightest drop in temperature below 70 ° C, the solutions become supersaturated and precipitation of calcium chloride or liquid glass. It is impossible to avoid lowering the temperature at the bottom of the well, therefore it is impossible to avoid the mudding of the perforations and the near-wellbore zone near the perforations. Well production is inevitably reduced.

The proposed invention solves the problem of increasing the efficiency of waterproofing works.

The problem is solved by a method of reducing the water cut of oil production, which consists in stopping the production well, opening the annular and linear valves, pumping highly mineralized water through the annular space in the volume of the annular space, closing the annular valve, venting the overpressure, and pumping the calculated high volume into the reservoir. water in a constant mode at a pressure of 7.5-10.0 MPa, stop the injection, close the well and withstand pressure before pressure equalization and uniform distribution of highly saline water in the flooded zone of the formation, the well is put into operation, the well is put into constant operation for up to 5 days with constant monitoring of bottomhole pressure and water cut of the product, the well is operated with a depression value of from 0.5 up to 1.5 MPa, while the volume of highly mineralized water injected into the reservoir is determined by the formula:

V _W ≈3.14 × m × h × R ² ,

where V _Z - injection volume, m ³ ;

m - coefficient of porosity, fraction of units;

h is the effective thickness of the reservoir, m;

R is the radius of the treated zone, equal to 2-4 m, depending on the injectivity of the formation, m

SUMMARY OF THE INVENTION

Deposits 302-303 of the Romashkinskoye oil field, stratigraphically confined to middle carbon, have a complex geological structure and are of a massive type. Productive deposits of deposits No. 302-303 are represented by complex heterogeneous carbonate reservoirs, interbedded with clay carbonate deposits, gypsum and mudstones. Collectors have a significant dissection, from 2 to 5 layers. Oil-saturated interlayers have different thicknesses and reach 23 m in some wells. These deposits are characterized by highly developed vertical fracturing of the host rocks, an increased oil viscosity (122-131 mPa · s) and a water-pressure regime, which contributes to the accelerated advancement of bottom water along the vertical axis of the well.

As a result, an unstable section of the oil-water contact is formed, which, depending on the flow rate of the well and the shielding properties of the overlapping rocks, breaks through to the bottom of the producing wells, which leads to premature watering of the produced products and transfer of the wells to an unprofitable fund.

To date, more than 360 producing wells of deposits 302-303 belong to the categories of low-profitable and unprofitable wells. In order to transfer these wells into the category of profitable in the presence of undeveloped oil reserves, geological and technical measures are required, i.e. waterproofing works involving teams of underground or overhaul wells. Waterproofing works are expensive and do not always lead to the expected results. In addition, the strength properties of insulating compositions in reservoir conditions deteriorate over time, which determines the need for repeated waterproofing operations in wells.

To reduce material costs and transfer unprofitable wells into the category of profitable, to improve the efficiency of water insulation works, a method of water insulation works in production wells that exploit carbonate deposits of deposits 302-303 is proposed. The essence of this method is to carry out waterproofing work in production wells by pumping highly mineralized water through the annulus to irrigated highly permeable zones of the carbonate reservoir using standard commercially available special equipment such as a pumping unit, tanker truck. The result of applying this method of waterproofing works is to reduce the water content of the produced products and transfer the wells to the profitable category without expensive geological and technical measures and without involving underground or overhaul crews.

Conducting water-tightening operations in the well contributes to a decrease in water cut in the produced products of wells by pumping highly mineralized water with a specific gravity of 1.175-1.185 g / cm ³ , incidentally produced from wells that exploit terrigenous deposits of the Pasha horizon of the Upper Devonian. The effect is achieved due to the penetration of highly mineralized water through a system of vertical cracks into highly permeable flooded “native” formation water with a specific gravity of 1.012-1.020 g / cm ^{3 of} the carbonate reservoir zone. Injected highly mineralized water has been in the flooded zone of the reservoir for a long time from 3 to 6 months due to the relatively low reservoir pressure of about 6.5-7.5 MPa and the lack of a system for maintaining reservoir pressure in reservoirs 302-303. As a result, the “light” plantar water is blocked by the injected “heavy” highly mineralized water in the most permeable fractures and flooded zones of the formation. As a result of blocking highly permeable fractures and flooded zones, less permeable oil zones of the formation are connected to active drainage, which leads to a decrease in the water content of the produced well products.

The method is as follows

Water insulation works are carried out along the annulus of the well (an annular gap between the inner wall of the production string with a diameter of 146 mm or 168 mm and the outer wall of the string of tubing with a diameter of 73 mm).

Stop the production well. Install a flange with a quick coupling on the annular valve. The pump unit is connected with the wellhead and a tank truck with highly saline water. The injection line is being tested for one and a half times the injection pressure provided for by the work plan. An annular valve is opened with an open linear valve on the tubing string. The pump unit pumps the calculated volume (annulus) of highly mineralized water into the annulus to the depth of the pump suspension, without exceeding the pressure specified in the work plan. Stop the pump unit. Close the annular valve, vent excess pressure. The calculated volume (formula 1) of highly mineralized water is pumped into the reservoir in a constant mode of operation of the pump unit at a pressure of 7.5 to 10.0 MPa for water to penetrate into the highly permeable aquifers of the reservoir. At the same time, the pressure should not exceed the maximum allowable pressure on the production casing (according to the work plan) and hydraulic fracturing pressure (from practical experience for deposits 302-303 about 12 MPa). Stop the pump unit. Close the gate valves. Disassemble the piping of the pump unit. They close the well under pressure for approximately 24-48 hours until the pressure is equalized and the mineralized water is evenly distributed in the flooded zone of the formation. The well is put into operation with the conclusion to a constant mode of operation for up to 5 days with constant monitoring of bottomhole pressure and water cut of the product. The well is operated with minimal values of depression per formation of the order of 0.5-1.5 MPa.

The volume of injected highly mineralized water is determined by calculation by the formula:

V _W ≈3.14 × m × h × R ² ,

where V _Z - injection volume, m ³ ;

m - coefficient of porosity, fraction of units;

h is the effective thickness of the reservoir, m;

R is the radius of the treated zone, 2-4 m, depending on the injectivity of the formation, m. Compared to other methods used in 302-303 deposits, the injection of highly saline water does not require the involvement of underground and overhaul crews, which positively affects the efficiency and payback period this method compared to others. The injection of highly saline water does not require additional costs. The average cost of one downhole treatment is 43,700 rubles, which is an order of magnitude lower than the cost of the applied methods for increasing oil recovery.

Concrete example

Measures are being taken to reduce the water cut of oil production wells. The well is equipped with a production casing with a diameter of 168 mm, lowered to a depth of 832 m with artificial bottom at a depth of 827 m. Operated object: coal system, Namurian layer, Protvinsky horizon. Perforation intervals: 794-798 m. Downhole pumping equipment: sucker rod pump - 25-125RHAM-12-4-2-3, descent depth 760 m; tubing pipes (smooth) with a diameter of 73 mm with a 40-meter shank with a depth dispenser filled with a corrosion inhibitor SNPCH-1004); rods with a diameter of 19 mm. Current slaughter: 827 m. Technological mode: fluid flow rate - 6 m ³ / day., Oil production rate - 0.1 t / day., Water cut - 98%, reservoir pressure - 6.6 MPa, bottomhole pressure 6.3 MPa.

The production well is stopped, the annular and linear valves are opened, highly mineralized water with a density of 1.18 g / cm ³ in a volume of 8 m ^{3 is} pumped through the annular space, i.e. in the volume of the annulus, close the annular valve, vent excess pressure.

The volume of highly mineralized water pumped into the reservoir is determined by the formula:

V _W = 3.14 × m × h × R ² = 3.14 · 0.29 · 13.5 · 2 = 24.58 m ³

where V _Z - injection volume, m ³ ;

m - coefficient of porosity, fraction of units;

h is the effective thickness of the reservoir, m;

R is the radius of the treated zone, equal to 2-4 m, depending on the injectivity of the formation, m

A certain volume of highly saline water is pumped into the formation in a constant mode at a pressure of 7.5 to 10.0 MPa. The injection is stopped, the well is shut and kept under pressure until the pressure is equalized and the mineralized water is evenly distributed in the flooded zone of the formation for 48 hours. The well is put into operation with a conclusion to a constant mode of operation for 5 days with constant monitoring of bottomhole pressure and water cut of the product. The well is operated with values of depression per formation in the range from 0.5 to 1.5 MPa.

As a result of the work, the flow rate of the well remained the same and amounted to 6 m ³ / day, oil production rate increased from 0.1 to 3.8 tons / day, water cut decreased from 98 to 36%.

The application of the proposed method will improve the effectiveness of waterproofing works.

Claims (1)

A method of reducing the water cut in oil production, which consists in stopping the production well, opening the annular and linear valves, pumping highly mineralized water through the annulus in the volume of the annulus, closing the annular valve, venting excess pressure, and injecting the calculated volume of highly mineralized water into the formation. continuous operation at a pressure of 7.5-10.0 MPa, stop the injection, close the well and withstand pressure until equalization yes the occurrence and uniform distribution of highly mineralized water in the flooded zone of the formation, put the well into operation, put the well into constant operation for up to 5 days with constant monitoring of bottomhole pressure and water cut of the product, operate the well with depression values from 0.5 to 1 , 5 MPa, while the volume of highly mineralized water injected into the reservoir is determined by the formula:
V _W ≈3.14 × m × h × R ² ,
where V _Z - injection volume, m ³ ;
m - coefficient of porosity, fraction of units;
h is the effective thickness of the reservoir, m;
R is the radius of the treated zone, equal to 2-4 m, depending on the injectivity of the formation, m