Ternary anti-scaling method for continuously and stably adding medicament into well

Abstract

Aiming at the problems of discontinuous anti-scaling effect and poor stability of the existing dosing method, the invention provides a ternary anti-scaling method for continuously and stably adding a medicament into a well. The method is characterized by comprising the following steps: S1, determining a matching relationship between different submergence degrees and different medicament diluent amounts for stabilizing the medicament concentration of the produced liquid in an effective concentration range through a field test; s2, according to the submergence degree of the rod-pumped well, determining the design concentration after the underground medicament is continuously and stably added and diluted; and S3, adding the diluted medicament into the well according to the designed concentration by applying a dosing process. According to the ternary anti-scaling method for continuously and stably adding the medicament into the well, the matching relation between different submergence degrees and different medicament diluent amounts is quantified, and the defects that an original medicament adding method is continuous in anti-scaling effect and poor in stability are fundamentally overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of scale prevention and removal in the polymer flooding of oil fields, and particularly relates to a scale prevention method for polymer flooding that continuously and stably adds chemicals downhole. Background Art

[0002] When the polymer flooding production wells enter different production stages, scaling will occur in the production wells. As the scaling intensifies, the production wells are prone to pump jamming and production suspension, which not only affects the production time rate but also increases the operation construction cost. Therefore, a method of adding chemical agents downhole is adopted for scale prevention in polymer flooding production wells. The previously used "method of adding pure agents" has problems such as unstable effective concentration downhole and failure to meet the design requirements in the application of polymer flooding. For this reason, a new method for adding agents to prevent scale in polymer flooding production wells has been studied and has achieved good application effects. Summary of the Invention

[0003] The present invention aims at the problems of discontinuous scale prevention effect and poor stability in the existing agent addition methods in the background art, and provides a scale prevention method for polymer flooding that continuously and stably adds chemicals downhole. This scale prevention method for polymer flooding that continuously and stably adds chemicals downhole quantitatively obtains the matching relationship between different submergence depths and different amounts of chemical agent dilution solutions, fundamentally solving the disadvantages of the original agent addition method such as discontinuous scale prevention effect and poor stability.

[0004] The present invention can achieve the following technical solutions to solve its problems: This scale prevention method for polymer flooding that continuously and stably adds chemicals downhole includes the following steps: S1. Through on-site tests, determine the matching relationship between different submergence depths and different amounts of chemical agent dilution solutions to keep the chemical agent concentration in the produced fluid stable within the effective concentration range: S2. According to the submergence depth of the pumping well, determine the designed concentration of the diluted chemical agent continuously and stably added downhole; S3. Apply the agent addition process to add the diluted chemical agent downhole according to the designed concentration.

[0005] Further, the matching relationship between different submergence depths and different amounts of chemical agent dilution solutions in step S1: 1). When the submergence depth is 600 m or less, a chemical agent dilution solution volume of more than 0.125 m 3 / d can keep the chemical agent concentration in the produced fluid stable within the effective concentration range; 2). When the submergence depth is greater than 600 m to the wellhead, a chemical agent dilution solution volume of 1.5 m 3 / d can keep the chemical agent concentration in the produced fluid stable within the effective concentration range.

[0006] Further, the effective concentration range after the chemical agent concentration in the produced fluid is stabilized is 100 mg / L - 150 mg / L.

[0007] Further, the chemical addition process applied in step S3 is the centralized chemical addition process at the transfer station or the chemical addition process with a double plunger pump at the wellhead.

[0008] Further, the centralized chemical addition process at the transfer station is specifically as follows: at the transfer station, the scale inhibitor is added to the ground water mixing system according to the designed concentration through the chemical addition pump at the transfer station. The chemical solution is transported to the wellhead through the inter-station water mixing pipeline of the ground water mixing system, the water mixing filter in the metering station, and the single-well water mixing pipeline. On the premise of ensuring normal ground water mixing and gathering and transportation, 3 - 20 m 3 / d of the water containing chemical is continuously and quantitatively added into the wellbore, and it is ensured that the chemical concentration is continuously and stably above the effective scale inhibition concentration. The remaining water containing chemical flows back to the return oil pipeline through the wellhead water mixing valve and is transported back to the transfer station system.

[0009] Further, the chemical addition process with a double plunger pump at the wellhead is specifically as follows: a chemical storage cylinder is installed at the wellhead, and the chemical storage cylinder is connected to the chemical pipeline; the wellhead water mixing pipeline and the chemical pipeline connected to the chemical storage cylinder are respectively connected to the double plunger pump, and the double plunger pump is connected to the chemical and water mixing device; the scale inhibitor and the wellhead water are pumped into the chemical and water mixing device by the double plunger pump and mixed in different proportions, and then added into the oil-casing annulus of the casing through the mixing pipeline; the continuous chemical addition requirements of wells with different liquid production volumes are met, and at the same time, continuous and uninterrupted chemical addition of the double plunger pump for 24 hours is achieved.

[0010] Further, a wellhead water mixing valve is connected to the upper part of the wellhead water mixing pipeline; a mixed chemical outlet valve is connected to the mixing pipeline.

[0011] Further, the double plunger pump is connected to an electric control box, and the double plunger pump is frequency modulated and controlled through the electric control box.

[0012] Under the condition of not increasing the chemical dosage, the method of the present invention increases the amount of chemical diluent, and uses the chemical addition device or improves the wellhead pipeline process to continuously add the chemical and the water mixing solution from the casing into the wellbore. According to the method of the present invention, the continuity, stability and effectiveness of downhole chemical addition for scale inhibition can be greatly improved.

[0013] After the test was successful, on-site application was carried out on 876 tertiary wells in 6 tertiary blocks in the Sazhong Development Area. Among them, in the second type of strong base tertiary blocks in the west and east areas of the North First District, the centralized chemical addition process at the transfer station was applied. At the transfer station, the scale inhibitor was added to the ground water mixing system according to the designed concentration, and the chemical solution was transported to the wellhead through the oil well water mixing pipeline. On the premise of ensuring normal ground water mixing and gathering and transportation, 3 - 20 m 3 / d of the water containing chemical is continuously and quantitatively added into the wellbore, and it is ensured that the chemical concentration is continuously and stably above the effective scale inhibition concentration. After applying this process, the number of pump inspection wells stuck due to scale in oil wells has decreased significantly, and the number of pump inspections has decreased from 8 times per month to 4 times per month.

[0014] In addition, in the ternary blocks such as the east of the first and second rows in the north, the weak alkali in the east-west direction of the first block in the north, and the strong alkali in the first block in the south, the wellhead double-plunger pump chemical injection process is applied. A chemical injection device is installed at the wellhead, and the scale inhibitor and the wellhead blending water are mixed in different proportions and then added to the annulus between the tubing and the casing to meet the continuous chemical injection requirements of wells with different liquid production volumes. At the same time, the double-plunger pump can continuously inject chemicals for 24 hours without interruption. After applying this process, the number of pump inspection wells blocked by scale in oil wells has decreased significantly. The annual scale-related pump inspection rate has decreased from 12% to 3.6%. The annual savings in operation costs are about 6 million yuan, and the reduction in crude oil loss is about 0.2 million tons.

[0015] Through the above applications, the purposes of significantly reducing the number of pump inspection wells, extending the pump inspection cycle, reducing the costs of scale prevention and removal, and reducing the impact on production are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the chemical agent concentration change curve of the produced fluid of Well 361-23 in the embodiment of the present invention (0.5 m 3 / d); Figure 2 It is the chemical agent concentration change curve of the produced fluid of Well 6-Xie 113 in the embodiment of the present invention (0.25 m 3 / d); Figure 3 It is the chemical agent concentration change curve of the produced fluid of Well 6-Xie 113 in the embodiment of the present invention (0.125 m 3 / d); Figure 4 It is the chemical agent concentration change curve of the produced fluid of Well 63-Xie 12 in the embodiment of the present invention (2 m 3 / d--1.5 m 3 / d); Figure 5 It is the flow chart of the centralized chemical injection process in the embodiment of the present invention; Figure 6 It is the flow chart of the double-plunger pump wellhead chemical injection process in the embodiment of the present invention; Figure 7 It is the flow chart of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0018] A ternary scale prevention method for continuously and stably injecting chemicals into the wellbore in the present invention increases the amount of chemical diluent without increasing the chemical dosage, and uses a chemical injection device or improves the wellhead pipeline process to continuously inject the chemical and the blending aqueous solution into the wellbore from the casing.

[0019] Such as Figure 7As shown in the figure, a ternary scale prevention method for continuously and stably adding medicament into the wellbore includes the following steps: S1. To keep the medicament concentration in the produced fluid stable within the effective concentration range; through on-site tests, the matching relationship between different submergence depths and different amounts of medicament dilution solution is obtained; During on-site application, a dosing pump is used to directly inject the medicament solution into the annular space between the tubing and the casing, and samples are taken for testing every 2 hours. The test results are as follows ( Figures 1-4 ).

[0020] 1.1). Well Zhong 361-23 has a daily liquid production of 64 t, an oil production of 9 t, a water cut of 85.6%, a submergence depth of 428.29 m, a pump diameter of φ56 mm, an oil pressure of 0.34 MPa, and a casing pressure of 0.66 MPa. The amount of medicament dilution solution is 0.5 m 3 / d. The change curve of the medicament concentration in the produced fluid of Well Zhong 361-23 (0.5 m 3 / d) is as Figure 1 shown.

[0021] 1.2). Well Zhong 6-Xie 113 has a daily liquid production of 55 t, an oil production of 9 t, a water cut of 83.6%, a submergence depth of 621.76 m, a pump diameter of φ70 mm, an oil pressure of 0.60 MPa, and a casing pressure of 0.75 MPa. The amounts of medicament dilution solution are 0.25 m 3 / d and 0.125 m 3 / d. The change curve of the medicament concentration in the produced fluid of Well Zhong 6-Xie 113 (0.25 m 3 / d) is as Figure 2 shown. The change curve of the medicament concentration in the produced fluid of Well Zhong 6-Xie 113 (0.125 m 3 / d) is as Figure 3 shown.

[0022] 1.3). Well Zhong 63-Xie 12 has a daily liquid production of 60 t, an oil production of 5 t, a water cut of 91.6%, a submergence depth of 758.58 m (the liquid level is at the wellhead), an oil pressure of 0.22 MPa, and a casing pressure of 0.56 MPa. Initially, a high-concentration batch addition of 300 mg / l was adopted, and after 4 hours, it was restored to 150 mg / l. The amount of medicament dilution solution was 2 m 3 / d, and after 180 hours, the amount of medicament dilution solution dropped to 1.5 m 3 / d. The change curve of the medicament concentration in the produced fluid of Well Zhong 63-Xie 12 (2 m 3 / d--1.5 m 3 / d) is as Figure 4 shown.

[0023] Through the above on-site tests, the matching relationship between different submergence depths and different amounts of medicament dilution solution can be obtained: First, when the submergence depth is below 600 m, 0.125 m 3A chemical agent dilution liquid volume of 1.5 m³ / d or more can keep the chemical agent concentration in the produced fluid stable between 100 mg / L and 150 mg / L.

[0024] Second, when the submergence depth is greater than 600 m to the wellhead, a chemical agent dilution liquid volume of 1.5 m³ / d can keep the chemical agent concentration in the produced fluid stable between 100 mg / L and 150 mg / L. 3 A chemical agent dilution liquid volume of 1.5 m³ / d or more can keep the chemical agent concentration in the produced fluid stable between 100 mg / L and 150 mg / L.

[0025] S2. Determine the concentration of the diluted chemical agent continuously and stably added downhole according to the submergence depth of the pumping well; S3. Apply a chemical agent adding process to add the diluted chemical agent into the well according to the designed concentration.

[0026] The applied chemical agent adding process is a centralized chemical agent adding process at the transfer station or a chemical agent adding process with a double plunger pump at the wellhead.

[0027] As Figure 5 shown, the centralized chemical agent adding process at the transfer station is specifically as follows: At the transfer station, the scale inhibitor is added into the ground water mixing system according to the designed concentration through the chemical agent adding pump at the transfer station. The chemical agent solution is transported to the wellhead through the inter-station water mixing pipeline of the ground water mixing system, the water mixing filter at the metering station, and the single-well water mixing pipeline. On the premise of ensuring normal ground water mixing and gathering and transportation, 3 - 20 m³ / d of chemical agent-containing water mixing is continuously and quantitatively added into the well through a flow control nozzle, and it is ensured that the chemical agent concentration is continuously and stably above the effective scale inhibition concentration. The remaining chemical agent-containing water mixing flows back to the return oil pipeline through the wellhead water mixing valve and is transported back to the transfer station system. 3 A chemical agent dilution liquid volume of 1.5 m³ / d or more can keep the chemical agent concentration in the produced fluid stable between 100 mg / L and 150 mg / L.

[0028] As Figure 6 shown, the chemical agent adding process with a double plunger pump at the wellhead is specifically as follows: A chemical agent storage cylinder is installed at the wellhead, and the chemical agent storage cylinder is connected to the chemical agent pipeline; the wellhead water mixing pipeline and the chemical agent pipeline connected to the chemical agent storage cylinder are respectively connected to the double plunger pump, and the double plunger pump is connected to the chemical agent and water mixing device; the scale inhibitor and the wellhead water are pumped into the chemical agent and water mixing device by the double plunger pump and mixed in different proportions, and then added into the oil-casing annulus of the casing through the mixing pipeline; the continuous chemical agent adding requirements of wells with different liquid production volumes are met, and at the same time, continuous and uninterrupted chemical agent adding for 24 hours by the double plunger pump is achieved. The upper part of the wellhead water mixing pipeline is connected to the wellhead water mixing valve; the mixing pipeline is connected to the mixed chemical agent outlet valve; the double plunger pump is connected to the electric control box, and the double plunger pump is frequency-controlled through the electric control box. Example

[0029] As Figure 5 shown, the flow chart of the centralized chemical agent adding process. The scale inhibitor is added through the transfer station (the scale inhibitor zh-01 polyepoxysuccinic acid for water injection treatment can be used), the mixing of the chemical agent and water is realized by using the water mixing pipeline. On the premise of retaining normal ground water mixing, the wellhead uses a flow control nozzle to divert the chemical agent-containing water mixing and continuously add it into the well, and it is ensured that the chemical agent concentration is continuously and stably above the effective scale inhibition concentration.

[0030] According to this method, the centralized chemical addition process at the transfer station has been applied in the San Yuan blocks in the western part of the cut-off area in the first northern district and the eastern area. By adding scale inhibitors at the transfer station and using the water mixing pipeline to mix the chemicals and the water for mixing, on the premise of maintaining normal surface water mixing, the flow control nozzles are used at the wellhead to divert the chemical-containing water for continuous injection into the wellbore. After application, the average monthly number of scale-stuck wells has decreased from 18 wells during the peak scaling period to 6 wells; the number of pump inspection operations has decreased from 8 times per month to 4 times per month. Embodiment

[0031] As Figure 6 shown, the process flow diagram of chemical addition at the wellhead with a double plunger pump: A chemical addition device is installed at the wellhead. The chemical addition device includes a chemical storage cylinder, and the chemical storage cylinder is connected to a chemical pipeline; the water mixed at the wellhead and the chemical pipeline connected to the chemical storage cylinder are respectively connected to a double plunger pump. The scale inhibitor and the wellhead water for mixing are pumped into the chemical and water mixer by the double plunger pump and mixed in different proportions and then added to the annulus between the casing and the tubing; it meets the continuous chemical addition requirements of wells with different liquid production volumes, and at the same time realizes continuous and uninterrupted chemical addition by the double plunger pump for 24 hours.

[0032] Relying on the method of the present invention, the wellhead chemical addition device has been improved to a continuous double plunger pump device. The wellhead double plunger pump chemical addition process has been applied in the San Yuan blocks such as the east of the first and second rows in the north, the western part of the cut-off area in the first northern district with weak alkali, and the strong alkali in the first southern district. A chemical addition device is installed at the wellhead. The scale inhibitor and the wellhead water for mixing are mixed in different proportions and then added to the annulus between the casing and the tubing, meeting the continuous chemical addition requirements of wells with different liquid production volumes, and at the same time realizing continuous and uninterrupted chemical addition by the double plunger pump for 24 hours. After applying this process, the number of pump inspection operations due to scale sticking in oil wells has decreased significantly. The annual pump inspection rate due to scale has decreased from 12% to 3.6%. The annual savings in operation costs are approximately 6 million yuan, and the reduction in crude oil loss is approximately 0.2 million tons.

[0033] Those of ordinary skill in the art will realize that the embodiments described here are to help readers understand the implementation methods of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not depart from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A ternary scale prevention method for continuously and stably adding a chemical agent into a well Characterized in that: It includes the following steps: S1. Through on-site tests, determine the matching relationship between different submergence depths and different amounts of chemical agent dilution solution to keep the chemical agent concentration in the produced fluid stable within the effective concentration range; S2. According to the submergence depth of the pumping well, determine the designed concentration of the diluted chemical agent continuously and stably added into the well; S3. Apply the chemical agent adding process to add the diluted chemical agent into the well according to the designed concentration.

2. The ternary scale prevention method for continuously and stably adding a chemical agent into a well according to claim 1, Characterized in that: The matching relationship between different submergence depths and different amounts of chemical agent dilution solution in step S1: 1) When the immersion depth is 600 m or less, the dilution liquid volume of the agent above 0.125 m 3 / d or more can keep the agent concentration in the produced fluid stable within the effective concentration range; 2) When the submergence depth is greater than 600 m to the wellhead, the amount of the chemical dilution solution of 1.5 m³ / d can keep the chemical concentration of the produced fluid stable within the effective concentration range. 3 / d of the chemical dilution solution can keep the chemical concentration of the produced fluid stable within the effective concentration range.

3. The ternary scale prevention method for continuously and stably adding a chemical agent into a well according to claim 1 or 2, Characterized in that: The effective concentration range after the chemical agent concentration in the produced fluid is stabilized is 100mg / L - 150mg / L.

4. The ternary scale prevention method for continuously and stably adding a chemical agent into a well according to claim 1, Characterized in that: The chemical agent adding process applied in step S3 is the centralized chemical agent adding process at the transfer station or the chemical agent adding process with a double plunger pump at the wellhead.

5. The ternary scale prevention method for continuously and stably adding a chemical agent into a well according to claim 4, Characterized in that: The described process of centralized chemical addition at the transfer station is specifically as follows: At the transfer station, the chemical agent is added to the surface water mixing system according to the designed concentration through the chemical addition pump at the transfer station. The chemical agent solution is transported to the wellhead through the inter-station water mixing pipeline of the surface water mixing system and the single-well water mixing pipeline. On the premise of ensuring normal surface water mixing and gathering and transportation, 3 - 20 m 3 / d of the chemical-containing water mixture is continuously and quantitatively added to the wellbore through the flow control nozzle, and it is ensured that the chemical agent concentration remains continuously stable above the effective scale inhibition concentration.

6. The ternary scale prevention method for continuously and stably adding a chemical agent into a well according to claim 5, Characterized in that: Divert and flow out 3 - 20 m 3 After continuously and quantitatively adding the medicated water with a flow rate of / d underground, the remaining medicated water returns to the return oil pipeline through the wellhead water mixing valve and is transported to the rotary oil station system.

7. The ternary scale prevention method for continuously and stably adding a chemical agent into a well according to claim 5, Characterized in that: Before the chemical agent solution is transported to the wellhead through the single-well water injection pipeline via the inter-station water injection pipeline of the ground water injection system, the chemical agent solution is filtered through the water injection filter in the metering station.

8. The ternary scale prevention method for continuously and stably adding a chemical agent into a well according to claim 4, Characterized in that: The chemical agent adding process with a double plunger pump at the wellhead is specifically as follows: Install a chemical agent storage cylinder at the wellhead, and the chemical agent storage cylinder is connected to the chemical agent pipeline; the water injection pipeline at the wellhead and the chemical agent pipeline connected to the chemical agent storage cylinder are respectively connected to the double plunger pump, and the double plunger pump is connected to the chemical agent and water mixing device; The scale prevention chemical agent and the wellhead water injection pump are pumped into the chemical agent and water mixing device through the double plunger pump and mixed in different proportions, and then added into the oil-casing annulus of the casing through the mixing pipeline; it meets the continuous chemical agent adding requirements of wells with different liquid production volumes, and at the same time realizes continuous and uninterrupted chemical agent adding by the double plunger pump for 24 hours.

9. The ternary scale prevention method for continuously and stably adding a chemical agent into a well according to claim 8, Characterized in that: The upper part of the water injection pipeline at the wellhead is connected to the water injection valve at the wellhead; the mixing pipeline is connected to the mixed chemical agent outlet valve.

10. The ternary scale prevention method for continuously and stably adding a chemical agent into a well according to claim 8, Characterized in that: The double plunger pump is connected to the electric control box, and the double plunger pump is frequency-controlled through the electric control box.

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