RU2078910C1 - Method of oil recovery - Google Patents

Abstract

FIELD: oil producing industry; methods of oil recovery from wells with complicated operating conditions. SUBSTANCE: fluid is lifted from the well by pump which is lowered on the tubing with bypass valve. Tubing is lower to under the level of product. Associated petroleum gas is accumulated into the tubing-casing annulus. Gas excessive pressure is released into flow through bypass valve. Bypass valve is installed below the zone of wax deposition and formation of sand plugs. The depth of location of bypass valve is determined by the formula given in the invention description. Gas is supplied monotonically at excessive pressure. It is effected by closing the channel for release and supply of gas into flow line, and its value is controlled by the difference of pressure satisfying the condition Pm-Pb ≥ 0.5 MPa. EFFECT: provision of restoration of optimal operating conditions of unfortunate wells, increased their production rate, reduced specific energy consumption in oil lifting due to maximum utilization of the energy of associated petroleum gas entering the pump from the formation together with oil. 1 dwg, 2 tbl

Description

 The invention relates to methods for producing oil from wells and can be used primarily in the oil industry, in pump wells with complicated operating conditions.

Known methods of oil production by downhole pumps, according to which a sucker rod pump (SHG), an electric centrifugal pump (ESP) and an electro-diaphragm pump (UZDN) are lowered into a well on a tubing string (tubing) and the liquid is pumped upward through pipes [1]
According to known methods, the associated gas accumulated in the annulus under excessive pressure is periodically vented through the bypass valve on the wellhead valve into the flow line of the well.

 A disadvantage of the known production methods is that in case of violations of the optimal operating mode of the pump in the well due to the abnormality of the oil recovery process and the influx of fluid from the reservoir, the recovery of the associated gas energy mode is not provided. In addition, in complicated wells, known production methods do not provide trouble-free operation of pumping units due to abrasive wear of the working elements of the pump sand. Sand is removed from the formation and is received by the pump due to the presence of associated gas in the oil. After the natural separation of gas and sand at the pump inlet, the rest of them, together with the liquid, enter the tubing string through the pump. A significant disadvantage of the known methods is that simultaneously with the saturation of the liquid in the pipes with sand, a decrease in gas energy occurs due to the natural separation at the pump inlet. This leads to a slowdown in the rate of ascent of sand through the pipes up. At the same time, due to the release of free gas from the stream, paraffin precipitation and coagulation of sand-containing paraffin formations occur. Migrating in a stream, they become stronger, as a result of which the column of liquid in the pipes becomes heavier. The process of enlargement of sand-containing paraffin formations is accompanied by their gravitational deposition down the periphery of the flow along the pipe walls, which is why paraffin plugs completely saturated with sand form in the tubing string. At the same time, the productivity of the pump installation decreases, and with the formation of plugs in the pipes, the installation fails (breakage of the rod string of the SHGN units, overheating of the cable entry and loss of insulation of the electric cable of the ESP and EDN units).

 A known method of lifting fluid from a well with a sucker rod pump lowered into the well on a column of hollow rods with radial holes in the bottom of the column [2] Radial holes communicate the cavity of the column of hollow rods with the cavity of the tubing string above the pump plunger. According to the known method, the lifting of the liquid is carried out along the tubing string, and the hollow rods end the compressed gas from an external source and displace the liquid from the boom cavity under gas pressure until the pump is discharged. Using a pump involves reducing the amplitude of the loads at the point of suspension of the rod string.

 The disadvantage of this method is that its application requires an additional source of gas energy, in addition, it does not provide the use of gas energy to combat paraffin deposits and the formation of sand plugs in pipes.

 There is a known method of operating wells with a gas lift, which involves raising the liquid to the surface due to the energy of the gas supplied from an external source through gas lift valves to the tubing string [3] There is also known an uncompressed gas lift using gas from an overlying reservoir [4] However, the known gas lift methods cannot be used effective for extracting fluid from pumping wells due to the high energy intensity and low gas lift efficiency. Significant additional capital costs are also required to equip pumping wells with a gas lift, which makes it economically viable, especially at the late stage of oil field development.

 The closest in technical essence is the method of operating the downhole oil pump [5] (prototype). The method includes the accumulation of associated gas from the reservoir into the annulus to a pressure equal to the hydrodynamic in the tubing of a working well, then, after increasing the pressure, bleeding and dumping it through the upper pipe of the tubing string into the flow line of the well. The method is intended only to facilitate the launch of an idle well at low temperatures.

 The disadvantage of this method is that when placing a bypass valve on the upper pipe of the tubing string, the energy of the associated gas supplied to the pump receiver from the reservoir is not fully used to improve the operating parameters of pumping installations in complicated wells. As a result, pumping wells are operating in a non-optimal mode and, as a result, the flow rate of wells decreases and the specific energy consumption for raising oil increases.

 The objective of the invention is to restore the optimal mode of operation of complicated wells, increase their flow rate and reduce specific energy consumption for raising oil due to the most complete use of the energy of the associated gas supplied to the pump from the reservoir with the oil.

,
где H_кп глубина спуска в скважину перепускного клапана, м;
H_п глубина зоны отложения парафина и образования песчаных пробок в колонне НКТ, м;
P_м и P_в давления соответственно в межтрубном пространстве и выкидной линии на устье скважины, МПа;
ρ_см плотность газожидкостной смеси в межтрубном пространстве выше насоса, т/м³;
g ускорение свободного падения, м/с²;
(g 9,81 м/с²)
D_нкт и D_э диаметры соответственно наружный НКТ и внутренний обсадных труб, мм,
причем подачу газа обеспечивают монотонно под избыточным давлением путем перекрытия устья скважины канала сброса и подачи газа в выкидную линию, а его величину контролируют по разности давлений, отвечающей условию
P_м P_в ≥ 0,5 МПа (2)
Заявляемый способ отличается от прототипа местом подачи газа под избыточным давлением в колонну НКТ, определяемым по формуле (1), обеспечением его монотонной подачи под избыточным давлением путем перекрытия на устье скважины канала сброса и подачи газа в выкидную линию и величиной избыточного давления, контролируемой по разности давлений, отвечающей условию (2).The essential features of the proposed method, providing a solution to this problem, are that in the energy-saving method of Duplihin oil production, which includes raising the fluid from the well with a pump lowered to the level, accumulating associated gas in the annulus and relieving the excess gas pressure by supplying it through the bypass channel valve into the flow line of the well, gas is supplied to the lower pipes of the tubing string through a bypass valve installed below the zone of paraffin deposition and the formation of sand casing in pipes at the depth of descent, determined by the formula

,
where H _kn depth of descent into the well of the bypass valve, m;
H _{p the} depth of the zone of deposition of paraffin and the formation of sand plugs in the tubing string, m;
P _m and P _in pressure, respectively, in the annulus and flow line at the wellhead, MPa;
ρ _{cm the} density of the gas-liquid mixture in the annulus above the pump, t / m ³ ;
g acceleration of gravity, m / s ² ;
(g 9.81 m / s ² )
D _tubing and D _e diameters respectively of the outer tubing and inner casing, mm,
moreover, the gas supply is provided monotonously under excess pressure by blocking the wellhead of the discharge channel and supplying gas to the flow line, and its value is controlled by the pressure difference corresponding to the condition
P _m P _at ≥ 0.5 MPa (2)
The inventive method differs from the prototype in the place of gas supply under excess pressure to the tubing string, determined by the formula (1), ensuring its monotonous supply under excess pressure by blocking the discharge channel at the wellhead and supplying gas to the flow line and the amount of excess pressure controlled by difference pressure corresponding to condition (2).

 These differences allow us to conclude that the claimed technical solution meets the criterion of "novelty."

 From the current level of technology is not known other technical solutions containing these distinctive features of the proposed method. This allows us to conclude that the claimed method has an "inventive step".

 The drawing schematically shows the layout of the equipment lowered into the well, using the proposed method.

 The arrangement includes a pump 1 and a bypass valve 2, lowered into the well on the tubing string 3.

 To control the pressures in the annulus 4 and flow line 5 of the well, pressure gauges 7 and 8, respectively, are installed on the wellhead 6.

 To implement the method, the pump 1 and the bypass valve 2 are lowered on the tubing string 3 into the well to a predetermined depth below the level (in the drawing, as an example, SHGN is shown, for the ESP and ED the layout is similar). A bypass valve 2 is installed on one of the lower pipes of the tubing string 3. The descent depth and installation location of the valve 2 are chosen below the sediment zone in the tubing (paraffin, sand). It is determined by the formula (1) containing three algebraically summed quantities. The first term of formula (1) takes into account the depth of the deposition zone of paraffin and sand plugs in the tubing string 3, the second, and subtracted, takes into account the effect on the level in the well of the pressure difference in the annulus 4 and on the level in the well of the pressure difference in the annulus 4 and the discharge line 5 is proportional to the ratio of the cross-sectional area of the tubing string 3 and casing, and the third term is the abnormality of the depth of deposits in the tubing depending on the level in the annulus 4, the flow rate of the well and gas content oil.

 After the descent of the pump 1 and the bypass valve 2 at the wellhead is completed, the pressure relief and gas supply channel 9 from the annulus 4 to the flow line 5 is closed and the pump 1 is started. With the well running continuously, associated gas enters the pump from the reservoir to receive the pump . Part of the gas volume as a result of natural separation at the intake of pump 1 is released from the oil and accumulates in the gas cavity above the liquid level in the annulus 4. As it accumulates in the annulus, the pressure rises and the liquid level is pushed to the bypass valve 2. After being displaced level to the bypass valve 2, a gas breakthrough occurs through the valve in the fluid flow pumped up the tubing string 3, then during the operation of the pump a monotonous gas flow is established m pressure through the bypass valve 2 from the annular space into the furnace of fluid in the tubing. After the establishment of excess pressure, the well begins to function in steady state. According to the invention, the overpressure is the difference between the pressure in the annulus 4 and the pressure on the flow line 5. The values of these pressures are monitored by pressure gauges 7 and 8 installed on the wellhead equipment 6. Providing a continuous flow of gas into the tubing string through the bypass valve 2 leads to an additional carbonation of the oil flow and thereby reducing its density along the entire length of the column. Bubbles of gas, falling through the bypass valve 2 into the oil stream, expand in the volume of the stream and give it additional energy. This increases the rate of rise of carbonated oil up. An additional supply of associated gas energy to the flow helps to increase the rate of oil rise in the pipes upward, which creates conditions that ensure the equilibrium of moving systems. This eliminates the reasons leading to an increase in sand-containing paraffin formations in the stream, deposition of paraffin and the formation of sand plugs in the pipes.

Experimentally, it was found that at a pressure on the mouth of not less than 0.5 MPa is ensured monotonic gas through the bypass valve 2 to the tubing 3. It is found that when the condition P _m P _a ≥ 0,5 MPa pump device with bypass valve 2 starts to function stably and at the same time the well production rate increases, which allows to bring it to the optimal mode. As can be seen from table 1, with an excess pressure of 0.5 to 3.9 MPa, the increase in well production is 9 11 m ³ / day.

 The experimentally claimed method was tested on wells 292/809, 270/1367 and 301/1200 of the Ermakovskoye oil field in the Nizhnevartovsk region, wells are operated respectively SHGN, ESP and EDN.

Example 1. At well 292/809, complicating factors are paraffin deposits in the tubing string from a depth of 850 m and sand removal in an amount of 12 g / l. The production rate of the well before the implementation of the proposed method is 9 m ³ / day. (table 1). The efficiency of the pump is 0.23, the total efficiency of the pump installation is 0.15, the specific energy consumption is 22.9 kWh / t (table. 2).

 When testing the proposed method, the sucker rod pump type НН-44-30-11 was lowered to a predetermined depth of 1300 m below the liquid level, the bypass valve 2 was installed below the sediment zone in the tubing, determining (1) the depth of its descent 970 m.

After starting the pump installation with a valve 10 on the wellhead 6, the gas supply and pressure relief channels 9 to the flow line 5 were blocked. With the borehole going to a constant mode, pressures of 4.5 and 8 MPa were observed in the annulus 4 and 0.6 MPa at flow line 5. According to these data, the amount of overpressure during the experiment was 3.9 MPa, which corresponds to condition (2). As a result, it was established at well 292/809 that during the experiment a monotonous gas supply from the annulus 4 to the tubing string 3 was provided. The experimental values of the controlled parameters are given in Table 1, which shows that with an overpressure of 3.9 MPa the well production rate increased up to 18 m ³ / day, and according to comparative calculations, the specific energy consumption per 1 ton of oil after the implementation of the proposed method decreased from 22.9 to 9.1 kWh / t.

Example 2. Well 270/1367 is operated by ESP-50-1550. Complicating factors at the well are paraffin deposits in the tubing string at a depth of 700 m and the removal of sand from the formation in an amount of 11 g / l. The well production rate before the implementation of the proposed method was 33 m ³ / day (Table 1), pump efficiency 0.66, total efficiency of the pump installation 0.31, unit electricity consumption 6.52 kW. h / t (table. 2).

 During testing, the ENC-50-1550 was lowered to a depth of 1520 m, the bypass valve was installed below the paraffin deposition zone in the pipes, and its location was determined using formula (1) to a depth of 815 m.

After the pumping unit was turned on, the channel 6 was shut off by the valve 10 of the wellhead reinforcement 6. The well was monitored at the wellhead using pressure gauges 7 and 8: pressure 2.0 MPa in the annulus and 1.6 MPa on the flow line 5 of the well. The pressure difference according to these data was 0.5 MPa, which indicates compliance with condition (2) during the experiment. From the table. 1 it can be seen that the flow rate of the well increased from 33 to 44 m ³ / day. According to comparative calculations, the specific energy consumption per 1 ton of oil decreased from 6.5 to 5.3 kWh / t (Table 2).

Example 3. At well 301/1200, complicating factors are paraffin deposits in the tubing, starting from a depth of 700 m and the removal of interimpurities, sand in the amount of 10.5 g / l from the reservoir with oil. The well production rate before testing was 3 m ³ / day. (table. 1), pump efficiency 0.3, the total efficiency of the pumping unit 0.14, the specific energy consumption of 6.94 kW • h / t (table 2).

 When testing the proposed method, the EDN-10 type electric diaphragm pump was lowered to a depth of 1400 m, the bypass valve 2 was installed below the paraffin deposition zone in the tubing, having determined by its formula (1) its descent depth was 815 m.

After starting up the pumping unit at the wellhead, the gas supply and pressure relief channels 9 were shut off by a valve 10 to the flow line 5. With the well getting to a constant mode, the pressure in the annulus 7 0.6 was observed at the mouth 7 and 8, and on the flow line 5 0.1 MPa. According to these data, the pressure difference was 0.5 MPa, which indicates compliance with condition (2). The results of the experiment at well 301/1200 show that at an overpressure of 0.5 MPa through the bypass valve 2 into the tubing string 3 from the annulus 4, a monotonous gas supply was provided. This is confirmed by an increase in well production by 10 m ³ / day (Table 1). From the table. 2 it is seen that the specific consumption of electricity decreased from 6.94 to 4.64 kWh / t after the implementation of the method. The depth of descent of the bypass valve 2 is determined by the formula (1) and amounted to 815 m

The production rates for all three wells during the experiment were carried out with a TOR-1 counter (accuracy ± 2%) of the Sputnik-A group metering units, the levels in the wells were determined with an SKU-1M wave meter, specific electricity consumption was calculated using experimental data from the wells up to and after using the proposed method. From table 2 it is seen that after the implementation of the proposed method in wells, the specific energy consumption for oil recovery decreased by 1.2 13.8 kWh / t. The main factor influencing this indicator is the improvement of the lift operation, i.e. tubing strings due to aerated oil flow by monotonous supply of associated gas from the annulus to the flow of associated gas. At the same time, the density of the liquid column in the tubing string decreases, which contributes to an increase in oil flow from the reservoir and, accordingly, an increase in the daily production rate of the well. According to the experiment, the increase in the flow rate of wells amounted to 9 11 m ³ / day (table 1).

 Tests of the proposed method showed that its effectiveness is to restore the optimal mode of operation of complicated wells, increase their flow rate and reduce specific energy consumption for oil recovery, and the optimal mode is constantly maintained by overpressure according to (2). These results were obtained on the basis of existing pumping equipment of existing wells. In this case, only additional equipment of each well with an overflow valve and its installation below the zone of deposition of paraffin and the formation of sand plugs in the tubing string at a depth determined by formula (1) were required. This confirms that the claimed method is industrially applicable.

Claims (1)

The method of oil production, including lifting the fluid from the well with a pump lowered on the tubing to a level with a bypass valve, accumulating associated gas in the annulus of the tubing and casing and relieving the excess gas pressure by supplying it to the flow line of the well, characterized in that gas is supplied to the lower pipes of the tubing string through a bypass valve installed below the zone of paraffin deposition and the formation of sand plugs in the tubing n and the depth of descent N _KP , determined by the formula

where N _{p the} depth of the zone of deposition of paraffin and the formation of sand plugs in the tubing string, m;
P _m and P _in pressure, respectively, in the annulus and flow line at the wellhead, MPa;
ρ _cm is the density of the gas-liquid mixture in the annulus above the pump, t / m ³ ;
g acceleration of gravity;
D _nk.t and D _e, respectively, the outer diameter of the tubing and the inner diameter of the casing, mm,
wherein the gas flow monotonically provide pressurized matching P _m P _a ≥ 0,5 MPa.

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