Method for paraffin removal of oil well of pumping unit with medium and high water content

Abstract

The invention provides an oil well paraffin removal method for a medium-high water content pumping unit, which comprises the following steps of: firstly determining the maximum allowable stress of an oil well sucker rod string, then recording the maximum load of a suspension point of the pumping unit during normal production of the oil well, and finally carrying out paraffin removal operation, starting the pumping unit and an oil well production back-pressure valve, and opening the oil well production back-pressure valve when the bouncing pressure reaches 6-8MPa; the produced liquid in the oil pipe is released in a pressure excitation mode, the powerful impact liquid impacts and removes wax on the inner wall of the oil pipe and the outer wall of the sucker rod, and the purpose of paraffin removal is achieved. The paraffin removal device is applied to paraffin removal of more than 100 high-water-content pumping unit oil wells in Datong Oilfields, North China Oilfields, Jilin Oilfields and the like, the success rate is 100%, normal production of the oil wells is guaranteed, and the purpose of prolonging the pump inspection period of the oil wells is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production engineering, and in particular relates to a method for cleaning wax from an oil well with a medium or high water content pumping unit. Background Art

[0002] Pumping oil well wax cleaning is a daily maintenance measure for oil wells. It is one of the measures to ensure the normal production of oil wells and extend the oil well pump inspection cycle. Commonly used wax cleaning methods include thermal wax cleaning, chemical wax cleaning, mechanical wax cleaning, etc.

[0003] Zhang Long's "Research and Application of Thermal Washing Parameter Monitoring Technology for Machine-Drilled Wells" published in "Petroleum and Petrochemical Energy Conservation" in 2021, Vol. 11, No. 2, 2021, records: In order to collect, display and record important data in the whole process of thermal washing of machine-drilled wells, provide important data support to technical management personnel, so as to analyze and judge the quality of thermal washing and effectively improve the thermal washing effect of machine-drilled wells, a certain oil mine has developed a thermal washing parameter analyzer for machine-drilled wells. It mainly consists of a parameter recording device, 2 pressure transmitters and 2 temperature sensors. The instrument is suitable for the analysis of all types of machine-drilled hot washing parameters. It can accurately grasp the control of temperature and pressure during hot washing of a single well, as well as the length of time for well washing. It can effectively eliminate the error of parameter reading, guide the adjustment of the hot washing cycle, and ensure the quality of hot washing of machine-drilled wells. The use of this instrument can reduce the number of well washing by 915 times per year, save an average of 450kWh of electricity and 600m3 of gas for each well not washed, and save an annual cost of 738,900 yuan.

[0004] Zhang Pengju et al. published a comparative study on the application of wax removal technology in Jiudong Oilfield in the journal Drilling and Production Technology, Vol. 43, No. 2, 2020. It states that the crude oil components and chemical composition of Jiudong Oilfield were tested, the relationship between crude oil temperature and viscosity was analyzed, the wax precipitation temperature and the composition of wax samples were determined, and the characteristics of wax deposition in mechanical oil wells in Jiudong Oilfield were summarized. On this basis, according to the production situation, the oil casing backwashing and wax removal process, the solid sucker rod pump positive washing process, and the hollow sucker rod hot medium circulation well washing and wax removal process were compared and studied. Finally, it was believed that the hot washing and wax removal process using hollow sucker rods as channels can effectively solve the wax removal problem in the oilfield. It is recommended to use this process for wax removal and prevention operations in similar wells in Jiudong Oilfield to ensure the normal production of oil wells.

[0005] Lai Nanjun et al. published "Analysis on the Effect of Chemical Wax Removal and Prevention Technology in Ansai Oilfield" in "Drilling and Production Technology", Vol. 39, No. 10, 2020. It is recorded that wax deposition is common in oil wells during the production of waxy crude oil. An effective wax removal and prevention technology is an important factor in ensuring the stable production of oil wells. The application effect of the chemical wax removal and prevention technology is affected by the submergence, liquid production and water content. Under the complex conditions of oil wells, its on-site application effect is difficult to evaluate. In order to study the application effect of the wax removal and prevention technology, based on the principle of wax removal and prevention technology, the high-wax crude oil and sediments before and after the application of the wax removal and prevention technology in Ansai Oilfield were taken as the research objects, and the crude oil group composition, wax composition, wax content, wax precipitation point, viscosity and wax dissolution rate were analyzed; four evaluation indicators were determined by comparison, and a multi-objective evaluation method was introduced to establish a wax removal and prevention technology effect evaluation system. The study shows that after the wax removal and wax prevention process is applied, the viscosity of crude oil decreases; the percentage of wax carbon numbers C16 to C30 decreases, and the percentage of wax above C30 increases; the average wax content change rate of crude oil is 22.99%; the average wax precipitation point change rate of crude oil is 2.86%; the wax dissolution rate of each wax removal and wax prevention agent is greater than 0.0160g / min; the comprehensive scores of CQ-1 process and CQ-2 process are high, and the field application effect is good. The calculation results are consistent with the direction of the application of chemical wax removal and wax prevention process in Ansai Oilfield, and have strong reference value.

[0006] Chinese patent CN 113372892A discloses a chemical wax remover for oil wells, a preparation method and application thereof, and a wax removal method for oil wells. The chemical wax remover for oil wells, based on the total mass of the wax remover as 100%, comprises the following components: 1-10% of C10-C18 hydrocarbon carboxylates, 8-30% of C4-C17 mixed hydrocarbons, 5-25% of alcohol ether mutual solvents, and 35-84% of water. The present invention provides a chemical wax remover for oil wells, a preparation method and application thereof. The wax remover of the present invention is an emulsion type wax remover, which is safe to operate, has good solubility and dispersibility with the wax in the oil well, and has good wax removal and prevention effects.

[0007] Chinese patent CN 112127839A discloses an oil well paraffin removal device using centralized cooling, comprising a body, the body is buried underground, a solidification chamber is arranged in the body, and a material transport pipe penetrating the upper and lower end walls of the body is fixedly connected in the end walls on the upper and lower sides of the solidification chamber, the material transport pipe is provided with a material transport chamber connecting the solidification chamber and the upper and lower ends of the body, and oil can be transported from bottom to top through the material transport chamber during actual operation, and a cooling device for cooling oil is arranged in the material transport chamber. During the oil production process, the oil is cooled when passing through the device, and the oil will be waxed on the inner wall of the device after the temperature drops to the waxing temperature, so that the paraffin component in the oil is greatly reduced in the device, thereby preventing the wax from forming in the well wall when the oil is subsequently transported; after a certain period of waxing, the paraffin on the inner wall can be scraped off, and the paraffin can be used as a by-product of oil production after being recovered in the equipment, thereby improving the utilization rate of resources.

[0008] Chinese patent CN 105464625 A discloses a method for handling gas lock in tight oil and gas wells, including: after determining that gas lock occurs, closing the 250-type Christmas tree special valve connected to the wellhead small four-way and the oil gathering pipeline by the monk head; through the pressure change of the oil pressure gauge and the back pressure gauge during the up and down strokes of the pumping unit, the opening and closing of the 250-type Christmas tree valve is controlled according to the difference between the pressure values ​​shown by the oil pressure gauge and the back pressure gauge, until the pressure of the oil pressure gauge is greater than the back pressure gauge pressure by 2.0MPa to 2.5MPa, the 250-type Christmas tree special valve connected to the wellhead small four-way and the oil gathering pipeline is opened; the oil well is produced normally, and the gas lock phenomenon of the oil well is solved. The technician or operator can solve the gas lock problem at the wellhead, which meets the normal production of tight oil and gas wells, and the effective time rate is increased by more than 50%.

[0009] Many scholars believe that the produced fluid from medium-high water-content oil wells with a water content of more than 75% is a stable water-in-oil emulsion, and the oil wells have slight or almost no wax deposition. In fact, for medium-high water-content oil wells with a water content of more than 75%, some oil wells still have serious wax deposition, and these oil wells often have a high liquid production. Whether hot washing, chemical wax removal, or mechanical wax removal is used, a large amount of investment is required.

[0010] Therefore, how to solve the problem of wax removal in medium and high water-content oil wells with a water content of more than 75% has become a technical problem that needs to be solved urgently by technicians. Summary of the invention

[0011] The invention provides a method for cleaning wax in oil wells with medium and high water content pumping units, which solves the problem of cleaning wax in oil wells with medium and high water content of more than 75%, ensures normal production of the oil wells, and achieves the purpose of extending the pump inspection cycle of the oil wells.

[0012] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0013] A method for cleaning wax from a medium-high water-content pumping unit oil well, comprising:

[0014] Step 1: Determine the maximum allowable stress F1 of the oil well sucker rod string;

[0015] Step 2: Record the maximum load F2 of the pumping unit suspension point during normal production of the oil well;

[0016] Step 3: Perform wax removal.

[0017] The method comprises: step 31, stopping the pumping unit head at the upper dead center and tightening the oil well packing box;

[0018] Step 32, close the oil well production back pressure valve and start the pumping unit;

[0019] Step 33, observe the value of the pressure gauge on the oil well flow line, when the value of the pressure gauge reaches 6-8MPa, open the oil well production back pressure valve;

[0020] Step 34, verifying the maximum allowable stress F1;

[0021] When the pumping depth is greater than 2000m, F1-(F2+60)>40;

[0022] When the pumping depth is less than 1800m, F1-(F2+80)>60;

[0023] When the pump depth is 1800m-2000m, F1-(F2+80)>50;

[0024] Step 35, repeat the wax removal operation;

[0025] After step 33 is performed, according to the maximum allowable stress F1 of the pumping depth, step 34 is satisfied, and steps 32 and 33 are repeated, and each step 33 is performed after an interval of 10 minutes;

[0026] Step 4: After the wax cleaning operation is repeated 6-8 times, the oil well is producing normally. After the oil well is producing for 10-12 days, continue to perform the wax cleaning operation according to step 3.

[0027] Furthermore, the maximum allowable stress F1 is:

[0028] F1=[σ max ]=(0.25T+0.7163σ min )β

[0029] Among them, σ max is the maximum allowable stress of the sucker rod when working, MPa; σ min is the minimum allowable stress of the sucker rod when it is working, MPa; T is the minimum tensile strength of the sucker rod material, MPa; β is the service coefficient considering factors such as corrosion.

[0030] Furthermore, the maximum load F2 of the suspension point of the pumping unit during normal production of the oil well is the maximum load in the manual test dynamometer diagram or the automatic test dynamometer diagram of the oilfield automation system.

[0031] The embodiments of the present invention bring the following beneficial effects:

[0032] The wax removal method for medium-high water-content pumping wells has been applied in more than 200 wells in Huabei, Dagang, Changqing and other oil fields, with a success rate of 100%. The average annual saving of hot washing for a single well is 1.5 times; the saving of wax removal chemicals is 0.75 tons.

[0033] Other features and advantages of the present invention will be described in the following description, and some features will become apparent from the description or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention provides a flowchart of a method for removing paraffin from an oil well with a medium-high water content pumping unit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] like Figure 1 As shown, an embodiment of the present invention provides a method for cleaning wax in a medium-high water-content pumping unit oil well, comprising the following steps:

[0038] Step 1: Determine the maximum allowable stress F1 of the oil well sucker rod string;

[0039] F1=[σ max ]=(0.25T+0.7163σ min )β

[0040] In the formula, σ max is the maximum allowable stress of the sucker rod when working, MPa; σ min is the minimum allowable stress of the sucker rod when it is working, MPa; T is the minimum tensile strength of the sucker rod material, MPa; β is the service coefficient considering factors such as corrosion.

[0041] In this embodiment, the maximum allowable stress of the oil well sucker rod string is determined by the technicians in the pumping scheme of the oil well production project, which is well known to those skilled in the art and will not be described in detail here. It is detailed in "H-class sucker rod allowable stress calculation and fatigue life prediction method" published by Fan Song et al. in "Petroleum Drilling Technology" Vol. 45, No. 6, 2017.

[0042] Step 2: Record the maximum load F2 of the pumping unit suspension point during normal production of the oil well;

[0043] In this embodiment, the maximum load of the pumping unit suspension point when the oil well is in normal production is the maximum load in the manual test dynamometer diagram or the automatic test dynamometer diagram of the oilfield automation system; the method of testing the dynamometer diagram is well known to those skilled in the art and will not be described in detail here. Tan Chaodong et al. published "Prediction of wax deposition in pumping unit wells and evaluation of wax removal effect driven by timing dynamometer diagram" in "Petroleum Drilling and Production Technology" in 2022, Vol. 44, No. 1, has a detailed record.

[0044] Step 3: Perform wax removal.

[0045] The method comprises: step 31, stopping the pumping unit head at the upper dead center and tightening the oil well packing box;

[0046] Step 32, close the oil well production back pressure valve and start the pumping unit;

[0047] Step 33, observe the value of the pressure gauge on the oil well flow line, when the value of the pressure gauge reaches 6-8MPa, open the oil well production back pressure valve;

[0048] Step 34, verifying the maximum allowable stress F1;

[0049] When the pumping depth is greater than 2000m, F1-(F2+60)>40;

[0050] When the pumping depth is less than 1800m, F1-(F2+80)>60;

[0051] When the pump depth is 1800m-2000m, F1-(F2+80)>50;

[0052] Step 35, repeat the wax removal operation;

[0053] After step 33 is performed, according to the maximum allowable stress F1 of the pumping depth, step 34 is satisfied, and steps 32 and 33 are repeated, and each step 33 is performed after an interval of 10 minutes;

[0054] Step 4: After the wax cleaning operation is repeated 6-8 times, the oil well is producing normally. After the oil well is producing for 10-12 days, continue to perform the wax cleaning operation according to step 3.

[0055] The working principle of the embodiment of the present invention is: the oil well starts the pumping unit, the oil well production back pressure valve, when the pressure reaches 6-8MPa, the oil well production back pressure valve is opened; the produced fluid in the oil pipe is released in a "pressure-excited" manner, and the powerful impact fluid impacts and removes the wax on the inner wall of the oil pipe and the outer wall of the sucker rod, thereby achieving the purpose of wax removal.

[0056] Specific embodiments: Example 1: XXX-105 well, downhole pump depth 1900m.

[0057] Step 1: Determine the maximum allowable stress F1, KN of the oil well sucker rod string

[0058] The XXX-105 downhole pump has a depth of 1900m. In the downhole pumping plan for oil well production, the technicians calculated that the maximum allowable stress of the oil well sucker rod string is 210KN.

[0059] Step 2: Record the maximum load F2 (KN) of the pumping unit suspension point during normal production of the oil well

[0060] When the oil well is in normal production, the maximum load of the pumping unit suspension point is the maximum load of 68KN (rounded) in the manual test dynamometer diagram, and the maximum load in the automatic test dynamometer diagram of the oilfield automation system is 68KN;

[0061] Step 3: Wax removal

[0062] (1) Stop the pumping unit at the top dead center

[0063] (2) Tighten the oil well packing box

[0064] (3) Close the oil well production back pressure valve

[0065] (4) Start the oil pump

[0066] (5) Observe the value of the pressure gauge on the oil well outlet pipeline. When the pressure on the pressure gauge reaches 8MPa, open the oil well production back pressure valve;

[0067] (6) Check the maximum allowable stress F1

[0068] When the pump depth is 1800m-2000m, F1-(F2+80)=210-(68+80)=62>50

[0069] (7) Repeat wax removal operation

[0070] After (5), the maximum allowable stress F1 at the pumping depth meets (6), and (3), (4), and (5) are repeated, with an interval of 10 minutes between each operation (5).

[0071] (8) Normal operation of oil wells

[0072] After the wax removal operation was repeated 8 times, the oil well was in normal production. After the oil well was in production for 12 days, the wax removal operation was continued according to step 3.

[0073] XXX-105 well saves 1.8 hot washes per year and 0.65 tons of wax removal chemicals.

[0074] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0075] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for removing paraffin from oil wells with medium or high water content pumping units, characterized in that: The method comprises: Step 1: Determine the maximum allowable stress F1 of the oil well sucker rod string; Step 2: Record the maximum load F2 of the pumping unit suspension point during normal production of the oil well; Step 3: Perform wax removal. The method comprises: step 31, stopping the pumping unit head at the upper dead center and tightening the oil well packing box; Step 32, close the oil well production back pressure valve and start the pumping unit; Step 33, observe the value of the pressure gauge on the oil well flow line, when the value of the pressure gauge reaches 6-8MPa, open the oil well production back pressure valve; Step 34, verifying the maximum allowable stress F1; When the pumping depth is greater than 2000m, F1-(F2+60)>40; When the pumping depth is less than 1800m, F1-(F2+80)>60; When the pump depth is 1800m-2000m, F1-(F2+80)>50; Step 35, repeat the wax removal operation; After step 33 is performed, the maximum allowable stress F1 at the pumping depth satisfies step 34, and steps 32 and 33 are repeated. Each time step 33 is completed, the next operation is performed 10 minutes later; Step 4: After the wax removal operation is repeated 6-8 times, the oil well is producing normally. After the oil well is producing for 10-12 days, continue to perform the wax removal operation according to step 3.

2. The method for removing paraffin from a medium-high water-content pumping unit oil well according to claim 1, wherein in step 1, the maximum allowable stress F1 of the oil well sucker rod string is determined, characterized in that: The maximum allowable stress F1 is: F1=[σ max ]=(0.25T+0.7163σ min )b Among them, σ max is the maximum allowable stress of the sucker rod when working, MPa; σ min is the minimum allowable stress of the sucker rod when it is working, MPa; T is the minimum tensile strength of the sucker rod material, MPa; β is the service coefficient considering factors such as corrosion.

3. The method for removing wax from oil wells with medium and high water content pumping units according to claim 1, wherein in step 2, the maximum load F2 of the suspension point of the pumping unit during normal production of the oil well is recorded, characterized in that: The maximum load F2 of the pumping unit suspension point during normal production of the oil well is the maximum load in the manual test dynamometer diagram or the automatic test dynamometer diagram of the oilfield automation system.

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