Control method for reducing wax removal water consumption of oil well

Abstract

The invention relates to the technical field of oil exploitation, in particular to a control method for reducing oil well wax removal water consumption. The method comprises the steps that a target oil well is determined, the melting temperature of well wax is measured through experiments, the temperature distribution of the target oil well during normal production is measured, the position of a wax precipitation section is obtained, the wax precipitation section serves as an experimental object, the shaft distribution temperature under different hot washing displacements and water temperatures is calculated, the temperature of the wax precipitation section is made to exceed the wax melting temperature, and the wax removal quality is guaranteed. The melting speed of paraffin in the well under different thermal washing parameters continues to be measured, a basis is provided for calculating the paraffin removal time, the paraffin removal time under the different thermal washing parameters is obtained according to the paraffin precipitation amount of the oil well on site and the paraffin melting speed, and a water quantity chart required by paraffin removal under the different thermal washing parameters is obtained according to the paraffin removal time and the displacement during thermal washing; and the hot washing water amount of the target oil well is accurately controlled according to the obtained plate of the water amount required for wax removal. According to the method provided by the invention, the wax removal effect can be ensured, the hot washing water amount can be reduced, and the oil well can be washed as required.

Description

Technical Field

[0001] The present invention relates to the technical field of oil extraction, and particularly to a control method for reducing the water consumption of wax removal from oil wells. Background Art

[0002] Wax deposition in oil wells is one of the common problems in oilfield production. After wax deposition in oil wells, on the one hand, it will cause the inner diameter of the oil delivery channel of the production tubing string to shrink, and even lead to wax blockage or wax sticking in the oil well, seriously affecting the production; on the other hand, it will also cause an increase in the load of the pumping unit and an increase in energy consumption.

[0003] Generally speaking, hot washing of oil wells is the main measure for wax removal. Hot washing of oil wells is to inject hot water into the annulus between the casing and the tubing to increase the temperature of the tubing string in the well, heat and melt the wax in the well, and achieve the purpose of removing the wax deposited on the tubing string. At present, the water consumption of hot washing of oil wells in the industry is mainly determined based on on-site experience, and it is impossible to wash the wells as needed; the research on hot washing parameters mainly focuses on hot washing temperature and displacement, while the water consumption required for oil wells with different well depths and different wax deposition degrees should be different. If the hot washing water consumption is not considered, it will cause incomplete wax removal or waste of water resources. Therefore, in view of the above deficiencies, a control method for reducing the water consumption of wax removal from oil wells is proposed. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] The present invention provides a control method for reducing the water consumption of wax removal from oil wells to overcome the problems in the existing hot washing technology of oil wells, such as the water consumption of hot washing of oil wells is mainly determined based on on-site experience, resulting in the inability to wash the wells as needed, leading to incomplete wax removal or waste of water resources.

[0006] (II) Technical Solutions

[0007] To solve the above problems, the present invention provides a control method for reducing the water consumption of wax removal from oil wells, including:

[0008] Step S1: Determine the target oil well, measure the wax melting temperature of the well wax of the target oil well and the temperature distribution during normal production of the target oil well, and obtain the initial wax deposition point and the wax deposition section of the target oil well;

[0009] Step S2: Take the wax deposition section determined in Step S1 as the experimental object, and take the wax melting temperature determined in Step S1 as the temperature base point to obtain the relationship between the wellbore distribution temperature of the target oil well at different temperatures and different hot washing displacements;

[0010] Step S3: According to the relationship between the wellbore distribution temperatures obtained in Step S2, through indoor simulated hot washing experiments of oil wells, obtain the relationship between the wax removal speeds of the target oil well at different temperatures and different hot washing displacements;

[0011] Step S4: Based on the paraffin wax deposition section of the target oil well obtained in Step S1, combined with the paraffin wax deposition thickness obtained from on-site investigation, obtain the paraffin wax deposition amount per unit area in the tubing. Then, in cooperation with the paraffin wax melting speed relationship obtained in Step S3, obtain the relationship between the wax removal time of the target oil well at different temperatures and different hot washing discharge rates.

[0012] Step S5: Based on the wax removal time relationship obtained in Step S4, calculate the total hot washing time of the target oil well, and obtain the water volume chart for wax removal of the target oil well at different temperatures and different hot washing discharge rates. Then, accurately control the hot washing water volume of the target oil well according to the obtained water volume chart for wax removal.

[0013] Preferably, in Step S1, the temperature distribution during normal production of the target oil well is obtained by the corrected formation temperature calculation method. The paraffin wax deposition section is the well section between the paraffin wax deposition starting point and the wellhead, and the temperature at the paraffin wax deposition starting point is lower than the wax melting temperature.

[0014] Preferably, in Step S2, the influencing factors of the wellbore distribution temperature relationship include formation temperature, temperature in the wellbore, temperature of the injected hot washing fluid, and hot washing fluid discharge rate. The wellbore distribution temperature includes the annulus temperature between the casing and the tubing and the temperature in the tubing.

[0015] Preferably, the calculation formula for the annulus temperature between the casing and the tubing is:

[0016]

[0017] In the formula: T an —Outlet temperature of the hot washing microelement in the annulus between the casing and the tubing, °C; T a(n-1) —Inlet temperature of the hot washing microelement in the annulus between the casing and the tubing, °C; T t(n-1) —Outlet temperature of the hot washing microelement in the tubing, °C; T s(n-1) —Temperature in the cement sheath, °C; m a —Mass of the microelement, kg; K t —Thermal conductivity of the tubing, W / (m·K); K w —Thermal conductivity of the cement sheath, W / (m·K); r ti —Inner diameter of the tubing, m; r t0 —Outer diameter of the tubing, m; r s —Outer diameter of the cement sheath, m; r ci —Inner diameter of the cement sheath, m; V i —Flow velocity of the hot washing fluid in the annulus between the casing and the tubing, m / s.

[0018] Preferably, the calculation formula for the temperature in the tubing is:

[0019]

[0020] In the formula: T t(n-1)—Outlet temperature of the micro-element for hot washing inside the tubing, °C; m t —Mass of the micro-element inside the tubing, kg; T tn —Inlet temperature of the micro-element for hot washing inside the tubing, °C; T an —Outlet temperature of the micro-element for hot washing in the annulus between tubing and casing, °C; V e —Flow rate of the hot washing fluid inside the tubing, m / s.

[0021] Preferably, in the step S3, the calculation relation of the wax removal rate is:

[0022]

[0023] In the formula: V1—Wax removal rate, g / (m 2 ·h); m1—Mass before wax removal, g; m2—Mass after wax removal, g; s—Wax deposition area, m 2 ; t—Wax removal time, h; V1—Wax removal rate, g / (m 2 ·h).

[0024] Preferably, in the step S4, the calculation relation of the wax deposition amount within the wax deposition section is:

[0025]

[0026] M 蜡 =v 蜡 ·ρ (5)

[0027] In the formula: v 蜡 —Well wax volume of the wax deposition section, m 3 ; r1—Inner diameter of the wax-deposited tubing, m; r2—Outer diameter of the wax-deposited sucker rod, m; d1—Wax deposition thickness inside the tubing, m; d2—Wax deposition thickness on the surface of the sucker rod, m; h—Length of the wax deposition section, m; ρ—Paraffin density, kg / m 3 ; M 蜡 —Well wax mass of the wax deposition section, kg.

[0028] Preferably, in the step S4, the calculation formula of the wax removal time is:

[0029]

[0030] In the formula: t—Wax removal time, h; s—Area of the wax in the wax deposition section, m 2 ; η—Correction coefficient; M 蜡 —Well wax mass of the wax deposition section, kg.

[0031] Preferably, in the step S5, the water volume required for wax removal is the product of the total hot washing time and the hot washing displacement.

[0032] (III) Beneficial effects

[0033] The control method for reducing the water consumption of wax removal in oil wells provided by the present invention first obtains the initial wax formation point and the wax formation section of the target oil well, and then sequentially obtains the wellbore distribution temperature relationship, wax removal speed relationship, and wax removal time relationship of the target oil well at different hot washing discharge rates and different temperatures. Finally, a water consumption chart for wax removal is obtained through calculation, and the hot washing water volume is accurately controlled through the water consumption chart for wax removal, so as to ensure both the wax removal effect and reduce the hot washing water volume, achieving the purpose of washing the oil well as needed. Description of the Drawings

[0034] Figure 1 It is a flowchart of the control method for reducing the water consumption of wax removal in oil wells according to an embodiment of the present invention;

[0035] Figure 2 It is a temperature curve graph before measurement and correction when the target oil well in an embodiment of the present invention is in normal production;

[0036] Figure 3 It is a temperature curve graph after measurement and correction when the target oil well in an embodiment of the present invention is in normal production;

[0037] Figure 4 It is a temperature distribution graph of the oil-casing annulus when the target oil well in an embodiment of the present invention is being hot washed;

[0038] Figure 5 It is a temperature distribution graph inside the tubing when the target oil well in an embodiment of the present invention is being hot washed;

[0039] Figure 6 It is a wax removal speed graph when the hot washing temperature of the waxed pipe in an embodiment of the present invention is 40°C;

[0040] Figure 7 It is a wax removal speed graph when the hot washing temperature of the waxed pipe in an embodiment of the present invention is 70°C. Detailed Embodiments

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0042] Figure 1 It is a flowchart of the control method for reducing the water consumption of wax removal in oil wells according to an embodiment of the present invention. As Figure 1 shown, the present invention proposes a control method for reducing the water consumption of wax removal in oil wells, which specifically includes:

[0043] Step S1: Determine the target oil well, measure the wax melting temperature of the paraffin wax in the target oil well and the temperature distribution during the normal production of the target oil well, and obtain the initial wax deposition point and the wax deposition section of the target oil well;

[0044] Step S2: Take the wax deposition section determined in Step S1 as the experimental object, and take the wax melting temperature determined in Step S1 as the temperature base point to obtain the relationship between the wellbore distribution temperature of the target oil well at different temperatures and different hot washing discharge rates;

[0045] Step S3: According to the relationship between the wellbore distribution temperatures obtained in Step S2, through indoor simulation of oil well hot washing experiments, obtain the relationship between the wax removal rates of the target oil well at different temperatures and different hot washing discharge rates;

[0046] Step S4: According to the wax deposition section of the target oil well obtained in Step S1, combined with the wax deposition thickness obtained from on-site investigations, obtain the wax deposition amount per unit area in the tubing. Combining with the relationship between the paraffin wax melting rates obtained in Step S3, obtain the relationship between the wax removal times of the target oil well at different temperatures and different hot washing discharge rates;

[0047] Step S5: According to the relationship between the wax removal times obtained in Step S4, calculate the total hot washing time of the target oil well, and obtain the chart of the water volume required for wax removal of the target oil well at different temperatures and different hot washing discharge rates. Accurately control the hot washing water volume of the target oil well according to the obtained chart of the water volume required for wax removal.

[0048] In this control method, in Step S1, the temperature distribution during the normal production of the target oil well is obtained by the corrected formation temperature calculation method. The wax deposition section is the well section between the initial wax deposition point and the wellhead, and the temperature of the initial wax deposition point is less than the wax melting temperature.

[0049] Specifically, first, obtain the wax melting temperature by adopting an indoor experimental method. The specific steps are as follows: put the paraffin wax in the well into a constant temperature water bath, and record the melting state of the wax at different temperatures respectively; the temperature when the wax sample dissolves and becomes loose is the wax melting temperature. Secondly, obtain the accurate temperature distribution during the normal production of the oil well by the corrected formation temperature calculation method. Combining with the wax precipitation temperature, find the starting point of wax deposition in the oil well; the well section between the wax deposition point and the wellhead has a temperature lower than the wax precipitation temperature, so this well section is the wax deposition section.

[0050] It should be noted that during the testing process, it was first discovered in the industry that the formation temperature distribution does not increase linearly according to the geothermal gradient, but there is a constant temperature layer in the well section 15 - 80m below the surface. This constant temperature layer is close to the local annual average temperature. Therefore, the starting point for calculating the well temperature should be 80m below the wellhead, and then increase linearly according to the geothermal gradient.

[0051] Formula for calculating the temperature during the normal production of oil wells in the industry before correction:

[0052] te = t0 + m L (7);

[0053] Formula for calculating the temperature during normal production of the oil well after correction:

[0054] t e = t1 + m(L - 80) (8)

[0055] In the formula: t e — Temperature at L m below the wellbore, °C; t0 — Surface temperature, °C; m — Geothermal gradient, °C / 100m; L — A certain depth below the wellbore, m; t1 — Annual average temperature, °C.

[0056] In practical applications, in step S2, the influencing factors of the temperature relationship in the wellbore distribution include formation temperature, temperature in the wellbore, temperature of the hot washing fluid entering the well and the displacement of the hot washing fluid. The wellbore distribution temperature includes the annulus temperature between the casing and tubing and the temperature in the tubing.

[0057] Specifically, first, based on the on-site hot washing process, a physical model is established: The hot washing fluid enters from the annulus between the casing and tubing, and the heat it carries is transferred in three directions: respectively, radially to the formation and the tubing, and axially downward; thus, the temperature gradually decreases axially downward. After the hot washing fluid enters the tubing, on the one hand, it receives the heat from the annulus between the casing and tubing; on the other hand, it transfers upward, and the temperature gradually increases axially upward.

[0058] Secondly, with the initial condition that the formation temperature is equal to the temperature in the wellbore, the heat exchange relationship between the hot washing fluid, the produced fluid and the formation is established, and based on the energy conservation theory, the wellbore temperature during hot washing is calculated.

[0059] In this control method, for calculating the annulus temperature between the casing and tubing, the wellhead is taken as the origin, and the vertical downward direction is positive. At a depth of (n - 1)dl from the wellhead in the annulus between the casing and tubing, a hot washing fluid microelement with a length of dl is taken. According to the energy conservation and heat conduction theories, the heat entering the microelement axially is equal to the heat exiting the microelement axially plus the heat dissipated by the microelement in the inner diameter and outer diameter directions.

[0060] Among them, the formula for calculating the annulus temperature between the casing and tubing is:

[0061]

[0062] In the formula: T an — Outlet temperature of the hot washing fluid microelement in the annulus between the casing and tubing, °C; T a(n-1) — Inlet temperature of the hot washing fluid microelement in the annulus between the casing and tubing, °C; T t(n-1) — Outlet temperature of the hot washing fluid microelement in the tubing, °C; T s(n-1) — Temperature in the cement sheath, °C; m a — Mass of the microelement, kg; K t — Thermal conductivity of the tubing, W / (m.k); K w—Thermal conductivity of cement sheath, W / (m·K); r ti —Inner diameter of tubing, m; r t0 —Outer diameter of tubing, m; r s —Outer diameter of cement sheath, m; r ci —Inner diameter of cement sheath, m; V i —Flow velocity of hot washing fluid in the annulus between tubing and casing, m / s.

[0063] In practical applications, since wax generally exists on the inner wall of the tubing, it is necessary to further calculate the temperature distribution inside the tubing. Taking the wellhead as the origin and the vertical downward direction as positive. At a depth of (n - 1)dl from the wellhead inside the tubing, a micro-element of hot washing fluid with a length of dl is taken. According to the theory of energy conservation and heat conduction, the heat conducted axially into the micro-element plus the heat conducted radially into the micro-element is equal to the heat conducted axially out of the micro-element.

[0064] Therefore, the calculation formula for the temperature inside the tubing is:

[0065]

[0066] In the formula: T t(n-1) —Outlet temperature of the hot washing micro-element inside the tubing, °C; m t —Mass of the micro-element inside the tubing, kg; T tn —Inlet temperature of the hot washing micro-element inside the tubing, °C; T an —Outlet temperature of the hot washing micro-element in the annulus between tubing and casing, °C; V e —Flow velocity of the hot washing fluid inside the tubing, m / s.

[0067] In this control method, in step S3, in practical applications, through indoor experiments, the hot washing process of the oil well is simulated. Among them, the calculation relationship of the wax removal rate is:

[0068]

[0069] In the formula: V1—Wax removal rate, g / (m 2 ·h); m1—Mass before wax removal, g; m2—Mass after wax removal, g; s—Wax deposition area, m 2 ; t—Wax removal time, h; V1—Wax removal rate, g / (m 2 ·h).

[0070] In practical applications, in step S4, first, through on-site investigation methods, the wax deposition thickness inside the tubing of a general oil well, such as 5 mm, is obtained, and thus the wax deposition amount per unit area, such as 4500 g / ㎡, is obtained. Therefore, the calculation relationship of the wax deposition amount within the wax deposition section is:

[0071]

[0072] M 蜡 =v蜡 ·ρ(5)

[0073] Where: v 蜡 —The volume of well wax in the wax deposition section, m 3 ; r1—The inner diameter of the wax-deposited tubing, m; r2—The outer diameter of the wax-deposited sucker rod, m; d1—The thickness of wax deposition inside the tubing, m; d2—The thickness of wax deposition on the surface of the sucker rod, m; h—The length of the wax deposition section, m; ρ—The density of paraffin wax, kg / m 3 ; M 蜡 —The mass of well wax in the wax deposition section, kg.

[0074] In this control method, in step S4, the wax removal time can be obtained through the wax deposition amount per unit area obtained. Among them, the calculation formula for the wax removal time is:

[0075]

[0076] Where: t—The wax removal time, h; s—The area of wax in the wax deposition section, m 2 ; η—The correction coefficient; M 蜡 —The mass of well wax in the wax deposition section, kg.

[0077] In practical applications, in step S5, the total hot washing time of the target oil well can be calculated according to the obtained wax removal time, and the water volume required for wax removal can be further calculated according to the obtained total hot washing time. Specifically, the water volume required for wax removal is the product of the total hot washing time and the hot washing displacement.

[0078] The control method for reducing the water consumption of wax removal in oil wells provided by the present invention has been tried and applied in multiple oil fields. Currently, the hot washing water volume of dozens of oil wells has been successfully optimized. By increasing the hot washing temperature and displacement, not only the average hot washing water volume per well is reduced, but also the hot washing cost can be reduced; at the same time, the time of the water cut recovery period of the oil well is reduced by more than half, and the oil production affected by each hot washing of a single well is nearly 2.5 tons less, which can create an economic benefit of nearly 10,000 yuan. In addition, this control method can also reduce the electricity consumption by nearly kilowatt-hours during heating, further reducing CO2 emissions, and has considerable social benefits. The following specifically describes the practical application of this control method for reducing the water consumption of wax removal in oil wells:

[0079] Step 1: Determine the target oil well, measure the melting wax temperature of the well wax of the target oil well and the temperature distribution during the normal production of the target oil well, and obtain the initial wax deposition point and the wax deposition section of the target oil well.

[0080] In this embodiment, taking Block A as an example, a 1200m deep well with a pump is selected, and the wax separation temperature is obtained by referring to the development data, so as to determine the melting wax temperature.

[0081] In practical applications, the wax samples from the oil wells in Block A of the oilfield are placed in a constant temperature water bath, and the melting states of the wax samples at temperatures of 30°C, 35°C, 40°C, 45°C, 50°C, and 55°C are examined respectively. It is found that at 45°C, the wax samples melt and become loose. Therefore, 45°C is the wax melting temperature of this oilfield. At the same time, by comparing with the wax precipitation temperature of 45.4°C in this oilfield, it is found that they are approximately equal. Thus, it is concluded that the wax precipitation temperature of each oilfield is the wax melting temperature.

[0082] Figure 2 This is the temperature curve graph before measurement and correction during the normal production of the target oil well in the embodiment of the present invention. Figure 3 This is the temperature curve graph after measurement and correction during the normal production of the target oil well in the embodiment of the present invention. As Figure 2 and Figure 3 shown, by adopting the corrected formation temperature calculation method, the temperature measuring instrument is lowered into the well to measure the temperature at different well depths, and the temperature distribution of the test well is obtained. By comparing the measured temperature, the downhole temperature error before and after correction is reduced from 18.6°C to 0.9°C, and the starting point of the wax precipitation well section extends from 470 m underground to 870 m, achieving consistency with the actual wax deposition section on site.

[0083] Step 2: Taking the determined wax deposition section as the experimental object and the determined wax melting temperature as the temperature base point, obtain the temperature distribution relationship in the wellbore of the target oil well at different temperatures and different hot washing discharge rates.

[0084] In this embodiment, Figure 4 This is the temperature distribution graph of the oil casing annulus during hot washing of the target oil well in the embodiment of the present invention. As Figure 4 shown, by using iterative calculation, the temperature distribution from the wellhead to the pump depth in the oil casing annulus can be obtained. In the figure, the abscissa is the temperature, the ordinate is the well depth, and the curve is the temperature distribution of the 1st, 2nd, 3rd, and 4th hot washing cycles at the oil casing annulus; Figure 5 This is the temperature distribution graph inside the tubing during hot washing of the target oil well in the embodiment of the present invention. As Figure 5 shown, by using iterative calculation, the temperature distribution from the wellhead to the pump depth inside the tubing can be obtained. In the figure, the abscissa is the temperature, the ordinate is the well depth, and the curve is the temperature distribution of the 1st, 2nd, 3rd, and 4th hot washing cycles inside the tubing.

[0085] Table 1 Wax precipitation point temperature chart (°C) for a pump depth of 1400 m

[0086]

[0087]

[0088] In this embodiment, taking a 1400m deep pumping well as an example, Table 1 shows the wax deposition point temperature chart (℃) for a 1400m deep pumping well. As shown in Table 1, the temperature of the wax deposition section of the oil well reaching the wax melting temperature of 45℃ is the lowest limit, and the temperature chart reached by the wax deposition section under different hot washing parameters is theoretically calculated. Taking the wax deposition section reaching the wax melting temperature as the boundary, the temperature chart of the wax deposition section corresponding to different hot washing parameters at a certain depth of the sucker rod pump is calculated.

[0089] Step 3: According to the relationship of the wellbore distribution temperature obtained, through indoor simulation of oil well hot washing experiments, obtain the wax removal rate relationship of the target oil well at different temperatures and different hot washing displacements.

[0090] In this embodiment, Figure 6 is the wax removal rate diagram when the hot washing temperature of the wax deposition pipe in the embodiment of the present invention is 40℃. Figure 7 is the wax removal rate diagram when the hot washing temperature of the wax deposition pipe in the embodiment of the present invention is 70℃. As Figure 6 and Figure 7 shown, the test object of the indoor experiment is the wax deposition pipe. The simulated wax deposition oil pipe is placed in a constant temperature water pool, and the hot water temperature entering the wax deposition oil pipe is changed to 20, 40, 60, 70, 80, and 90℃ respectively, and the hot water displacement is 5m 3 / h, 10m 3 / h, and 15m 3 / h respectively to simulate hot washing, and the relationship of the wax removal rate under different hot washing temperatures and hot washing displacements is obtained through the experiment.

[0091] In practical applications, Table 2 shows the wax removal rate chart (g / ㎡ / h) at the wax deposition point of a 1400m deep pumping well. As shown in Table 2, according to the influence rules of different hot washing displacements and hot washing temperatures on the wax removal rate, the wax removal rate chart under different hot washing parameters can be obtained.

[0092] Table 2 Wax removal rate chart (g / ㎡ / h) at the wax deposition point of a 1400m deep pumping well in a certain oilfield

[0093]

[0094]

[0095] Step 4: According to the wax deposition section of the target oil well obtained, combined with the wax deposition thickness investigated on site, obtain the wax deposition amount per unit area, and cooperate with the obtained paraffin melting speed relationship to obtain the relationship of the wax removal time of the target oil well at different temperatures and different hot washing displacements.

[0096] In this embodiment, Table 3 shows the wax removal time (min) at a pump depth of 1400 m. As shown in Table 3, by combining the wax removal speed with the relationship between the hot washing temperature and displacement, a wax removal time chart under different hot washing parameters is obtained. It should be noted that in practical applications, the correction coefficient η is taken as 15. According to the wax thickness of the oil well investigated on site and combined with the wax removal time formula, a wax removal time chart under different hot washing parameters is obtained.

[0097] Table 3 Wax removal time (min) at a pump depth of 1400 m in a certain oilfield

[0098]

[0099] Step Five: According to the obtained wax removal time relationship, calculate the total hot washing time of the target oil well, and obtain the chart of water volume required for wax removal of the target oil well at different temperatures and different hot washing displacements. Accurately control the hot washing water volume of the target oil well according to the obtained chart of water volume required for wax removal.

[0100] In this embodiment, the total hot washing time of the target oil well can be calculated according to the obtained wax removal time. Table 4 shows the total hot washing time (min) under different hot washing parameters at a pump depth of 1400 m. As shown in Table 4, in practical applications, considering the time for hot water circulation to heat the waxed section and the wax removal time, taking the point where the annulus between the casing and tubing or the tubing first reaches the wax melting temperature as the starting point for wax removal and the point where all the wax is discharged from the wellhead as the end point, the total hot washing time is finally obtained.

[0101] Table 4 Total hot washing time (min) under different hot washing parameters at a pump depth of 1400 m

[0102]

[0103] In this embodiment, according to the relationship between the total hot washing time, displacement and required water volume, a hot washing water volume chart under different hot washing parameters is calculated. Finally, according to the hot washing water volume chart, high-temperature and large-displacement parameters are selected to finally achieve the purpose of reducing the hot washing water volume while ensuring the quality of hot washing wax removal.

[0104] Table 5 Hot washing water volume (m 3 )

[0105]

[0106]

[0107] In practical applications, Table 5 shows the hot washing water volume (m 3 ) at a pump depth of 1400 m under different hot washing parameters. As shown in Table 5, according to the equivalent relationship of hot washing water volume = hot washing displacement × time, combined with the above total hot washing time, a hot washing water volume chart under different hot washing parameters is calculated.

[0108] The control method for reducing the water consumption of wax removal in oil wells provided by the present invention first obtains the initial wax deposition point and the wax deposition section of the target oil well, and then sequentially obtains the wellbore distribution temperature relationship, wax removal speed relationship, and wax removal time relationship of the target oil well at different hot washing discharge rates and different temperatures. Finally, a water volume chart for wax removal is obtained through calculation, and the hot washing water volume is accurately controlled through the water volume chart for wax removal, so as to ensure both the wax removal effect and reduce the hot washing water volume, and realize on-demand well washing of oil wells.

[0109] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those of ordinary skill in the relevant technical fields can also make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the patent protection scope of the present invention shall be defined by the claims.

Claims

1. A control method for reducing the water consumption of wax removal in oil wells, characterized in that Including: Step S1: Determine the target oil well, measure the wax melting temperature of the wax in the target oil well and the temperature distribution during normal production of the target oil well, and obtain the initial wax deposition point and the wax deposition section of the target oil well; Step S2: Take the wax deposition section determined in Step S1 as the experimental object, and take the wax melting temperature determined in Step S1 as the temperature base point to obtain the relationship between the wellbore distribution temperature of the target oil well at different temperatures and different hot washing discharge rates; Step S3: According to the relationship between the wellbore distribution temperatures obtained in Step S2, through indoor simulation of oil well hot washing experiments, obtain the relationship between the wax removal rates of the target oil well at different temperatures and different hot washing discharge rates; Step S4: According to the wax deposition section of the target oil well obtained in Step S1, combined with the on-site investigated wax deposition thickness, obtain the wax deposition amount per unit area in the tubing. In cooperation with the relationship between the paraffin melting rates obtained in Step S3, obtain the relationship between the wax removal times of the target oil well at different temperatures and different hot washing discharge rates; Step S5: According to the relationship between the wax removal times obtained in Step S4, calculate the total hot washing time of the target oil well, and obtain the chart of the water volume required for wax removal of the target oil well at different temperatures and different hot washing discharge rates. Accurately control the hot washing water volume of the target oil well according to the obtained chart of the water volume required for wax removal; 2. The control method for reducing the water consumption of wax removal in oil wells according to claim 1, characterized in that, In Step S1, the temperature distribution during normal production of the target oil well is obtained by the corrected formation temperature calculation method. The wax deposition section is the well section between the initial wax deposition point and the wellhead, and the temperature of the initial wax deposition point is less than the wax melting temperature; 3. The control method for reducing the water consumption of wax removal in oil wells according to claim 1, characterized in that In Step S2, the influencing factors of the wellbore distribution temperature relationship include formation temperature, temperature in the wellbore, temperature of the injected hot washing fluid, and hot washing fluid discharge rate. The wellbore distribution temperature includes the annulus temperature between the casing and the tubing and the temperature in the tubing; 4. The control method for reducing the water consumption of wax removal in oil wells according to claim 3, characterized in that The calculation formula for the annulus temperature between the casing and the tubing is: where: T an — the outlet temperature of the annulus hot washing microelement between tubing and casing, °C; T a(n-1) — the inlet temperature of the annulus hot washing microelement between tubing and casing, °C; T t(n-1) —Outlet temperature of the infinitesimal element for hot washing inside the tubing, °C; T s(n-1) —Temperature inside the cement sheath, °C; m a —Mass of the infinitesimal element, kg; K t —Thermal conductivity of the tubing, W / (m·K); K w —Thermal conductivity of the cement sheath, W / (m·K); r ti —Inner diameter of the tubing, m; r t0 —Outer diameter of the tubing, m; r s —Outer diameter of the cement sheath, m; r ci —Inner diameter of the cement sheath, m; V i —Flow velocity of the hot washing fluid in the annulus between the tubing and the casing, m / s.

5. The control method for reducing the water consumption of paraffin removal in oil wells according to claim 3, characterized in that, The calculation formula for the temperature in the tubing is: Where: T t(n-1) — Outlet temperature of the hot washing micro - element in the tubing, °C; m t — Mass of the micro - element in the tubing, kg; T tn — Inlet temperature of the hot washing micro - element in the tubing, °C; T an —Outlet temperature of the micro - element for hot washing in the annulus between tubing and casing, °C; V e —Flow velocity of the hot washing fluid in the tubing, m / s.

6. The control method for reducing the water consumption of wax removal in oil wells according to claim 1, characterized in that In Step S3, the calculation relationship formula for the wax removal rate is: Where: V1—the wax removal rate, g / (m 2 ·h); m1—the mass before wax removal, g; m2—Mass after dewaxing, g; s—Wax deposition area, m 2 ; t—Dewaxing time, h; V1—Dewaxing speed, g / (m 2 ·h).

7. The control method for reducing the water consumption of paraffin removal in oil wells according to claim 1, characterized in that In Step S4, the calculation relationship formula for the wax deposition amount within the wax deposition section is: M 蜡 = v 蜡 · ρ (5) Where: v 蜡 — The volume of well wax in the wax deposition section, m 3 ; r1 — The inner diameter of the wax-deposited tubing, m; r2 — The outer diameter of the wax-deposited sucker rod, m; d1 — The thickness of wax deposition inside the tubing, m; d2 — The thickness of wax deposition on the surface of the sucker rod, m; h — The length of the wax deposition section, m; ρ — The density of paraffin wax, kg / m 3 ; M 蜡 — The mass of well wax in the wax deposition section, kg.

8. The control method for reducing the water consumption of wax removal in oil wells according to claim 1, characterized in that, Preferably, in Step S4, the calculation formula for the wax removal time is: Where: t—the dewaxing time, h; s—the area of wax in the wax deposition section, m 2 ; η—the correction coefficient; M 蜡 —the mass of well wax in the wax deposition section, kg.

9. The control method for reducing the water consumption of wax removal in oil wells according to claim 1, characterized in that In Step S5, the water volume required for wax removal is the product of the total hot washing time and the hot washing discharge rate.

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