RU2419718C1 - Procedure for well operation - Google Patents

Abstract

FIELD: oil and gas production. ^ SUBSTANCE: procedure consists in lifting downhole equipment, in well flushing-out, in borehole gauging, in assembly and lowering underground sand-proof equipment with a valve, in bringing well into service and in assembly and de-colmatage of a filter. According to the invention the filter is made in form of filter elements out of porous silicon carbide. During well operation a bottomhole zone of the well, bottomhole zone of reservoir and withdrawn fluid are effected with heat by transmission of voltage through porous silicon carbide under continuous or periodic mode. ^ EFFECT: raised efficiency of procedure due to treatment of bottomhole zone of reservoir with its de-colmatage; raised output of well and simultaneously purification of produced fluid from mechanical impurities during operation; increased reliability and duration of well operation due to raised erosion resistance of equipment. ^ 1 tbl, 7 cl

Description

The invention relates to the mining industry, in particular to gas and oil production, and can be used in the operation of wells for liquid and gaseous minerals and in the repair of wells to combat the removal of sand during operation.

A technical solution is known (Pat. RU 2338871 C1 BI No. 32 of 11/20/2008) a self-cleaning well filter, where, when assembling the casing string, the filter elements with an insulated heating electric coil are included in the assembly, connecting elastic rings to the contacts in the electrical circuit of the filters included in the layout sequentially. During operation, the cells in the winding and the grid are clogged with sediment deposits (asphalt resin and paraffin hydrate). To clean the ARPD, an electric cable is lowered into the casing, connected to the contact, the second contact is the mass. Electricity is fed through the cable to the winding. The winding is made of wire with high resistivity, heat oil, water, salt and gas. Heated to a temperature above the melting point of paraffin, the paraffin wax melts and flows down. The cable is lifted and the well is put back into operation.

The disadvantages of the solution are: low efficiency associated with the descent of a wire electric heater; in case of failure of the electric heater, the device cannot be repaired, it is necessary to lift the production casing, which is practically impossible; every time when cleaning from paraffin, it is necessary to stop the well and carry out the cable descent; if an electric generator is installed, then it is impossible to produce.

A well-known well filter with a cleaning function (US Pat. RU 2332560 C1. BI No. 24 of 08.28.2008), where a filter element is lowered into the well, made in the form of two electrodes isolated from each other by a grid of non-conductive material, made in the form of a metal grid, mounted concentrically on the pipe, connected to a source of electricity placed on the surface by cable. During operation, the cells in the grids are clogged with paraffin. For cleaning, a cable is lowered into the casing, electricity is supplied through the cable. In the gap between the grids, oil containing salts, water and gas is heated to a temperature above the melting point of paraffin. Paraffin is melted and flows down, the filter is cleaned, the cable is lifted and the well is put into operation.

The disadvantages of the technical solution are:

- the filter is lowered in the layout of the production string, which limits its use in wells where the string is not equipped with this device;

- cannot be repaired in case of failure of one of the elements, as it is necessary to remove the production casing;

- low efficiency, because mainly the volume between the grids is heated, and the temperature depends on the composition of the solution located between the grids; at a low salt concentration, the heating process practically does not proceed;

- it is impossible to maintain constant heating during operation due to design features and low efficiency of the device;

- It is impossible to use to clean acid, alkali, because the destruction of a device made of ordinary metal (pipes, threads, nets, casing) occurs;

- it is impossible to clean the filter from clay and siliceous compounds;

- the method requires a large number of technological operations.

The closest technical solution is the method of operating wells using tubular filters made of pressed titanium powder (II Maslov, “Methods for controlling sand removal from oil wells.” M., VNIIOENG. 1980, pp. 33-39). Well operation technology includes raising downhole equipment, flushing wells, patterning a wellbore, assembling and launching underground sand control equipment, putting a well into operation, and washing filters during their mudding. The filter was a steel pipe with windows. Two filter elements with a length of 600 mm are inserted into the housing based on pressed titanium powder. The tensile strength when tested by hydraulic pressure of 15 kgf / cm ² , the main pore diameter of 510-200 microns, porosity of 30-40%, permeability of at least 3 Darcy. The bottom of the filter assembly is equipped with a valve to ensure circulation during the descent of the filter into the well. After installing the filter, the valve closes with pressure from above and the liquid is filtered through the filters. Before the descent, the filter was covered with a layer of paraffin to protect the filter from clogging during descent. Upon reaching the bottom, paraffin melts and dissolves in oil. After descent, the solution was replaced by oil backwash.

The disadvantages of the method are:

Low efficiency of the well, caused by the limited ability to use the methods of stimulation - temperature effect, hydroimpulse.

This method is ineffective to use in the operation of gas wells, due to the low mechanical parameters of the equipment (low filter hardness and hydraulic strength), which will lead to erosion destruction of the filter and, accordingly, ground equipment as a result of exposure to the sand and gas stream entering the lift column

It is impossible to decolmate the equipment using acids, alkalis, since the destruction of the elements of the equipment of the housing, filter, thread, cement ring will occur.

It is not possible to clean the filter from clay and siliceous compounds.

The method requires a large number of technological operations.

The basis of the present invention is the task of the equipment anti-sand layout of the bottom-hole zone of the well, which allows to treat the bottom-hole zone of the formation, to increase the productivity of the well, the elimination of CCD and at the same time cleaning the produced fluid from mechanical impurities during operation, increasing the efficiency of the well through the use of thermal methods of influence and increase reliability and duration of the well due to the increased erosion resistance of the equipment.

Why in the method of operating the well, including raising the downhole equipment, flushing the well, patterning the well, assembling and lowering the underground filter with a valve, putting the well into operation, decolming the filter, characterized in that the filter is made in the form of filter elements made of porous silicon carbide, they heat the produced fluid and the bottomhole zone of the well in a constant or periodic mode during the selection of formation fluid, in addition, the descent column is equipped with an electric cable, in addition, the filter elements in the lower and upper parts are equipped with contacts, in addition, the decolmation of the filter is carried out by heating the filter elements by applying voltage to them or with solutions of acids, solvents or under the combined influence of thermal effects and solutions of acids and solvents, in addition, with an open bottom, the filter is sprinkled with gravel sprinkling consisting of alkaline earth metal carbonates and quartz sand in a ratio of 70-90 quartz sand, 30-10 alkaline earth metal carbonates, respectively, except for t second, DECOLMATATION filter and bottom zone is carried out in the course of operation of the well.

The essence of the proposed method is as follows. The main reasons for the decommissioning of wells during rock formation is the filter clogging, or its destruction, leading to the removal of sand. In the absence of gravel sprinkling, which is not always possible in connection with the design of the well, geological and field data, the filter must withstand the direct impact of the gas-sand mixture without breaking, for which it must have the corresponding hardness and strength higher than sand. The hardness of sandstone with quartz cement is 25000 kg / cm ² , the Mohs hardness category is -7, and the hardness is 3800-15000 kg / cm ² , the Mohs hardness category 3-6 for sandstones with carbonate and clay cement (O.Yu. Bergstein , M.A. Velikoselsky et al. “Improving the methods and means of coring in deep drilling.” M: NEDRA, 1977, pp. 7-35). Those. the filter material must have mechanical indicators higher than those given, otherwise, in the absence of gravel packing around the downhole filter, it will erosively erode by the abrasive gas-sand jet coming from the perforation channels.

The filter, made of a material based on silicon carbide, has significantly higher performance: hardness of more than 150,000 kg / cm ² , Mohs hardness category> 9 (OST 2-114-71). In the table. physical and mechanical indicators are given.

Phase composition, wt.% SiC 90-95, S _icв <10 Density, g / cm ³ 2.6-3.10 ± 0.05 Structure polycrystalline, fine-grained Bending strength at 20 ° С, MPa 280-320 Corrosion resistance, mg / cm ² days: - weight loss when boiling in water - weight loss by boiling in 1N HF solution <0.01 - mass loss upon boiling in a 1N NaOH solution <0.01 Thermal conductivity, W / m * K ^-1 180 Hardness kg / mm ² > 1500 Palmquist fracture toughness (W) KN / mm > 0.12 open porosity 18-38%

The advantage of the proposed solution is that the well, equipped with filter elements based on silicon carbide, has a number of technological capabilities that allow it to work reliably and efficiently. Due to the physical and mechanical properties of filter elements with a hardness of more than 150,000 kg / cm ² (Mohs hardness> 9), several times higher, the metal filter is able to withstand the erosive effect of the gas-sand mixture during operation without the formation of fistulas. The formation of fistulas leads to the fact that the filter becomes unable to perform its basic functions of retaining rock particles, causing the destruction of wellhead and ground equipment and the decommissioning of the well in overhaul.

The equipment has high corrosion properties, which allows their multiple decolmation in acidic and alkaline solutions, with obtaining high permeability.

During production, mechanical impurities are separated on the filter. When the filter and PZP are clogged, and the well productivity is significantly reduced, if the reason for the clogging is the deposition of paraffin deposits, the operation of oil wells, it is enough to create a high temperature by applying voltage to the silicon carbide filter elements, melt the paraffin deposits, put the well into operation and remove the paraffin deposits along with the produced fluid to the surface . The specific electrical resistance of silicon carbide varies 300-1400 Ohm · mm ² / m, which allows it to be powered using standard sources of electricity (direct or alternating voltage). The filter has both filtering properties and it works as a heater in one design, while in known solutions the filter is a separate device and an electric heater separately, either inserted into the filter or separately fed into the filter zone in the form of a heating element (heat element) on the cable.

In the case of filter mudding, the bottom-hole zone of the formation rock (clay particles - siltstone, argelite, etc., carbonate, sand), heating will not give significant results. The filter and PZP are treated with appropriate solutions (hydrochloric, hydrofluoric acids), solvents or alkalis that dissolve sand, clay, carbonates, and since the filter is made of porous silicon carbide, which is resistant to acids, alkalis, solvents, this can be done. And in combination with temperature, the effect increases many times. When the temperature rises for every 10 ° С, according to the Vant-Hoff rule, the rate of chemical reactions increases by 2-4 times, which will lead to more efficient removal of colmatant due to an increase in the reaction rate of the acid-solvent with the rock. In addition, at a temperature of 300-400 ° C or more created in the CCD, it is possible to heat up and drain the bottom-hole zone up to 10-15 m thick to a depth of more than 1-2 m in 10-20 hours of operation. This will eliminate the formation zone , will increase the phase permeability of the bottom-hole formation zone (BHP) due to its drying, removal of water, hydrocarbons, paraffin deposits will increase the filtering ability of the BHP, and when oil is extracted when the bottom-hole zone warms up well to 90-100 ° C, the oil viscosity decreases by an order of magnitude (Gubanov B.F., Zhuyko P.V., Cherepanov F.I.Ne which matured especially the rheological properties of light Usinsk oil and the conditions for its transport. Sat geology and development of oil deposits of the Komi Republic, VNIIOENG 1974, s.132-143). Liquefied oil moves much better along the formation towards the bottom and along the elevator string; at the mouth, the flow rate of the well increases by 2 or more times. When the temperature in the bottomhole zone increases to 300-400 ° С, the clay material dehydrates the terrigenous layer, which increases its permeability, which subsequently leads to a decrease in sand removal during operation.

To prevent destruction from the hydrostatic pressure of the filters, the lower part of the filters is equipped with a check valve. When the well stops, fluid from the elevator string flows through the valve into the annulus. During production, the valve closes, and the fluid enters the in-tube space through the filter over the entire surface, and not through the shoe.

When operating open-hole wells to prevent rock filling the open hole, the paraffin filter is sprinkled with gravel. As gravel sprinkling, a mixture is used consisting of quartz sand and alkaline earth metal carbonates in the ratio, in% 70-90 of quartz sand, 30-10 alkaline earth metal carbonates, respectively. The introduction of carbonates subsequently will allow to impose additional permeability in the sprinkling when processing the well with hydrochloric, hydrofluoric acids.

We have not found sources of patent documentation and scientific and technical literature that describe the claimed method of operating wells. The invention does not explicitly follow from the prior art, i.e. meets the condition of inventive step. Thus, the achieved technical result is due to the unknown operations of the method in question and their sequence.

The proposed technical solution has the criterion of "industrial applicability", because can be used in the operation of wells.

The essence of the proposed method is given in the example of a specific implementation.

The production string with a diameter of 168 mm was lowered to a depth of 1200 m. The daily production rate of the well at the nozzle 5 mm 60-70 tm ³ / day. The productive horizon lies at a depth of 1171-1190 m and is represented by sandstones prone to destruction. When installing a nozzle with a diameter of more than 6 mm, the well begins to carry the rock with the formation fluid.

Jamming borehole bottom and purification carried washing liquid density 1120 kg / ^m3, viscosity of 46 sec, SNA - 15/34 mg / cm ^2, the fluid loss of 4-6 cm ^3/30 min. Washing was carried out for 6 hours until the absence of sand in the sump. Then they lowered a column equipped with a cable for supplying electricity to silicon carbide filters, and downhole equipment with a valve system. Filters were placed in the range of 1170-1192 mm. After the descent of the underground equipment, the wellhead is sealed with a preventer providing operation at a pressure of 15.0 MPa.

Gravel washing on the basis of alkaline earth metal carbonates and quartz sand in the ratio, in% 70 quartz sand, 30 alkaline earth metal carbonates was carried out using industrial water. 5200 kg of washed gravel of 0.15-3 mm fraction are loaded into the ZPA mixer, which is tied with a cementing unit CA-320 and the annulus of the well. Water is fed into hopper pipes, from there with transported gravel in the annulus with a flow rate of 4-6 l / s. The circulation pressure was 3.0-4.0 MPa. Water, passing through the slots in the filter, entered the tubing and came to the surface. The end of the deposition was recorded by increasing the pressure on the annulus to 6.5-7.2 MPa, which indicated that gravel filled the space between the filter, pipe and the wall of the well, as well as between the shutter and the column.

To remove carrier fluid from gravel sprinkling, the well is allowed to take gas at a rate of 240-260 tm ³ / day. After the expiration of this period, the well is transferred to gas and examined.

The research results showed:

- the application of the method ensured a flow rate of about 180-240 tm ³ / day;

- well operation is conducted with a depression of 0.2-1.0 MPa;

- sand occurrence during well operation at elevated depressions was not observed due to increased erosion resistance of the equipment.

With a decrease in well productivity as a result of mudding, production was stopped without removing the elevator column, hydrochloric acid was pumped into the CCD while heating the CCD and CCD in the amount of 1.5 m ³ . Silicon carbide filter elements can be used at high temperatures (up to 1450-1600 ° C on the surface of the heaters), they do not oxidize during operation, they undergo little deformation, do not corrode, and are easily installed.

Acid reacted with the formation rock and carbonate sprinkling material, having cleaned the filter and the bottomhole formation zone from the introduced formation rock and paraffin deposits. The temperature in the CCD reached 250 ° C. The well was put into operation.

As a result of the application of the proposed method, it was possible to increase the magnitude of depression and well productivity.

The method is especially effective when conducting work in wells with abnormally low reservoir pressures (ANP), when work on killing wells, stimulation leads to a loss in productivity, and the well reaches its design mode for several months, and often does not reach it.

Claims (7)

1. A method of operating a well, including raising the downhole equipment, flushing the well, patterning the well, assembling and lowering the underground sand control equipment with a valve, putting the well into operation, decolming the filter, characterized in that the filter is made in the form of filter elements made of porous silicon carbide, in the process of the operation of the well, they carry out the temperature effect on the bottom-hole zone of the well, the bottom-hole zone of the formation and produced fluid by passing through porous silicon carbide e.g. zheniya in continuous or batch mode. 2. The method according to claim 1, characterized in that the descent column is equipped with an electric cable. 3. The method according to claim 1, characterized in that the filter elements in the lower and upper parts are equipped with contacts. 4. The method according to claim 1, characterized in that the decolmation of the filter is carried out by heating the filter elements by applying voltage to them or with solutions of acids, solvents or under the combined action of thermal effects and solutions of acids and solvents. 5. The method according to claim 1, characterized in that when the face is open, the filter is sprinkled with gravel sprinkling, consisting of alkaline earth metal carbonates and silica sand in the following ratio,%: 70-90 silica sand, 30-10 alkaline earth metal carbonates, respectively. 6. The method according to claim 1, characterized in that the decolmatization of the filter and the bottom-hole zone is carried out during the operation of the well. 7. The method according to claim 1, characterized in that during the operation of the well, an electric cable is lowered into the lower part of the column and voltage is applied to the silicon carbide filter elements.