Boron-injected neutron life logging method for negative pressure oil well

Abstract

The invention discloses a service life logging method for injecting boron neutrons into a negative pressure oil well. The method comprises the following steps of: installing a wellhead of the negative pressure oil well; calculating the leakage amount Q1 of liquid in the negative pressure oil well; preparing a boric acid solution; according to the logging method, the formation water of the measured formation is fully replaced with the boric acid solution, the petroleum in the formation is not driven, and the measured value can accurately reflect the remaining oil amount in the formation to the maximum extent.

Description

Technical Field

[0001] This invention relates to the field of logging technology for negative pressure wells, and specifically to a method for logging the boron neutron lifetime of negative pressure oil wells. Background Technology

[0002] Boron-injected neutron logging is a new method widely used in recent years for monitoring residual oil in casing wells of low- and medium-salinity formation water oilfields. In low-salinity formation water areas, because the capture cross-section Σ values ​​of oil and fresh water are not significantly different, conventional neutron lifetime logging cannot distinguish between oil and water. Therefore, boron-injected neutron logging technology was developed to adapt to the dynamic monitoring of oilfields in low-salinity areas.

[0003] The principle is to use boric acid as a tracer because the capture cross-section of boron is more than 100 times that of fresh water, and boric acid is easily soluble in water but insoluble in oil. Boron injection neutron lifetime logging first establishes a baseline. Then, based on parameters such as the formation thickness, pressure, and formation water salinity of the drilling well, the concentration, dosage, and injection pressure differential of the boric acid solution are designed. After the boric acid injection is completed, a neutron lifetime curve is measured. The difference in amplitude between the two curves is used to determine the water flooding status and remaining oil saturation of the formation.

[0004] Boron injection neutron logging is a complex process involving numerous pieces of equipment and many influencing factors. During boron injection neutron logging, improper selection of injection process parameters often leads to inaccurate reflection of the formation's mobile water content by the boric acid solution. This results in the formation capture section measurements failing to accurately reflect the formation's remaining oil saturation, leading to interpretation difficulties and misinterpretations. Especially in wells with low formation energy, resulting in varying degrees of wellbore fluid leakage and backflow into the formation, negative pressure wells often experience boron injection neutron lifetime logging failures.

[0005] Chinese invention patent (authorization announcement number CN1045220C) discloses two methods for finding remaining and residual oil using boron element and neutron lifetime logging tool. The methods involve using boron element solution as a measurement tracking agent, injecting it into oil and water wells with low salinity oil, and performing tracking measurements. At the same time, the distribution of remaining and residual oil in the oil layer is measured using a neutron lifetime logging tool.

[0006] Chinese invention patent application (publication number CN1210261A) discloses a method for measuring the water content of oil well production. Specifically, the method uses a flow meter and a boron neutron lifetime meter to measure the water content of oil well production. First, the flow meter is used to measure the dynamic production oil and water content and ratio of the oil well. Then, the boron neutron lifetime meter is used to measure the static oil and water content and ratio of the oil well.

[0007] U.S. Patent Application (US7134493B2) discloses a logging system for use in a wellbore formed in a formation. The system includes a cylindrical tubing extending from the surface into the wellbore and containing a large volume of wellbore fluid; a logging tool string capable of passing from a location inside the tubing to a location outside the tubing at the lower end of the tubing, and capable of being suspended by the tubing at said location outside the tubing; and a pressure pulse device disposed within the tubing, configured to be in communication with the logging tool strings.

[0008] The paper (Logging Technology, June 2001) describes the application and development of boron injection neutron lifetime logging technology in the North China Oilfield. None of the three patent documents and papers mentioned above describe a boron injection neutron lifetime logging method for negative pressure oil wells. Summary of the Invention

[0009] The purpose of this invention is to solve the above-mentioned technical problems and provide a method for boron neutron lifetime logging in negative pressure oil wells.

[0010] To achieve the above objectives, the present invention provides a method for boron injection neutron lifetime logging in negative pressure oil wells as follows:

[0011] 1) Installation at the head of a negative pressure oil well

[0012] The casing is inserted through all the measuring formations of the negative pressure well until the bottom of the casing is below the bottom of the measuring formation. The tubing is inserted inside the casing until the bottom of the tubing passes through all the measuring formations. Perforations are made in the casing wall at the location of the measuring formation. An annular space is formed between the casing and the tubing. The blowout preventer is connected to the top of the tubing and is in communication with the tubing. The measuring instruments are inserted inside the blowout preventer.

[0013] The top outlet of the annular space is connected to the recovery tank through the annular space pipeline, and the side wall outlet of the blowout preventer is connected to the ground pump truck through the pipeline. The annular space valve is installed on the annular space pipeline, and the pipeline valve is installed on the pipeline.

[0014] 2) Calculate the fluid loss Q1 in the negative pressure oil well.

[0015] Open the annular space gate and tubing gate, and inject formation water from the negative pressure well area into the tubing using a surface pump truck until the formation water flows out from the annular space outlet. Then, close the annular space gate and tubing gate in sequence.

[0016] After waiting time t, the measuring instrument is used to log downwards until the logging value of the measuring instrument jumps. The measuring instrument measures the height L from the top of the casing to the static fluid level in the well. If the logging requirements are met, the formation water loss Q1 in the well is calculated, and then step 3 is executed.

[0017] The formation water loss in the well is Q1 = the cross-sectional area of ​​the casing S × the height L from the top of the casing 6 to the static fluid level inside the wellbore;

[0018] 3) Prepare boric acid solution

[0019] Prepare boric acid solution according to the formation water loss Q1 in the well;

[0020] The total amount of boric acid solution W = wellbore volume A + (5~8) times the formation boron infiltration Q2 + formation water loss Q1 in the well;

[0021] 4) Well logging

[0022] The measuring instrument is lowered to the bottom of the last measuring formation, and then raised to the top of the uppermost measuring formation to perform baseline measurements. After the baseline measurements are completed, the measuring instrument is lowered to the bottom of the last measuring formation, and the oil casing annular space gate and the tubing gate are opened in sequence. The surface pump truck injects boric acid solution into the wellbore.

[0023] When the injection volume is equal to the casing volume, close the annular space gate of the oil and casing; continue injecting boric acid solution until at least one times the formation boron permeation volume Q2 is injected, so that the boric acid solution replaces the formation water; continue injecting boric acid solution and start measuring the formation boric acid content curve until all the prepared boric acid solution is injected and the curve measurement is completed.

[0024] Further, in step 2), if the logging requirements are not met, then based on the geological structure, reservoir thickness and physical property changes, injection-production relationship and basic data of the development unit where the drilling well and adjacent wells are located: if the adjacent well's production layer is the same as the well's production layer, the adjacent well should be shut down and production stopped. The height of the static fluid level in the wellbore from the top of the uppermost measuring formation should be measured again. If the logging requirements are met, it indicates that the production of the adjacent well has caused a decrease in the energy of the entire production formation. The fluid in the well should be reversed into the measuring formation until the height of the static fluid level in the wellbore from the top of the uppermost measuring formation meets the logging requirements, and then step 4) logging should continue. If the height of the static fluid level in the wellbore from the top of the uppermost measuring formation does not meet the logging requirements, then a plugging agent solution should be injected into the well through a surface pump truck until the logging requirements are met, and then step 4) logging should continue.

[0025] Furthermore, in step 2), if the logging requirements are not met, based on the geological structure, reservoir thickness and physical property changes, injection-production relationship and basic data of the development unit where the drilling well and adjacent wells are located, if the mining layer of the adjacent well is different from that of this well, the adjacent well is not shut down, and the adhesive solution is directly injected into the wellbore through the surface pump truck until the logging requirements are met, and then step 4) logging continues.

[0026] Furthermore, in step 2), the logging requirements are: the height of the static fluid level in the wellbore from the top of the uppermost measuring formation is not less than 200 meters; if the height of the static fluid level in the wellbore from the top of the uppermost measuring formation is less than 200 meters, then the logging requirements are not met.

[0027] Furthermore, the unblocking time of the adhesive is that it automatically and completely unblocks within 2 to 4 hours after logging.

[0028] Furthermore, in step 1), the cable of the measuring instrument passes through the sealer, which is mounted on the blowout preventer 15.

[0029] Furthermore, in step 2), the waiting time t = the sum of the depths of all measured formations s ÷ the logging speed v of the measuring instrument 10.

[0030] Furthermore, in step 3), the volume concentration of the boric acid solution is 20 g / L.

[0031] Furthermore, in step 3), the boric acid solution is prepared by using boric acid with a content greater than 99%, using formation water from a negative pressure oil well area, and the temperature of the formation water is 50-80℃.

[0032] Furthermore, in step 3), the wellbore volume A = casing cross-sectional area S × well depth H

[0033] Formation boron permeation rate Q2=[π(r1+r2)] 2 -πr1 2 ]×h

[0034] In the formula, r1 is the casing radius; r2 is the instrument detection length; and h is the total length of all measured strata in meters.

[0035] Furthermore, in step 4), the boric acid solution injection rate is not less than the formation water loss rate v;

[0036] Formation water loss rate v = formation water loss in well Q1 ÷ waiting time t;

[0037] Furthermore, in step 4), the injection pressure of boric acid solution by the ground pump truck 13 is no greater than 0.5 MPa.

[0038] Furthermore, in step 4), boric acid solution is injected at an injection rate not less than the formation water loss rate v.

[0039] Formation water loss rate v = formation water loss in well Q1 ÷ waiting time t.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows: the logging method of the present invention fully replaces the formation water in the measured formation with boric acid solution, and the oil in the formation is not driven, so the measured value can reflect the remaining oil in the formation to the maximum extent. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the negative pressure oil wellhead installation structure of the present invention. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] The specific method for boron neutron lifetime logging in negative pressure oil wells is as follows:

[0044] 1) Installation at the head of a negative pressure oil well

[0045] like Figure 1 As shown, the casing 6 penetrates all the measuring formations 7 of the negative pressure oil well until it is below the bottom of the measuring formation 7. The tubing 5 is installed inside the casing 6 until the bottom of the tubing 5 passes through the bottom of all the measuring formations 7. The casing 6 wall located at the measuring formation 7 has perforation holes. An annular space 12 is formed between the casing 6 and the tubing 5. The blowout preventer 15 is connected to the top of the tubing 5 and communicates with the tubing 5. The measuring instrument 10 is installed inside the blowout preventer 15. The cable 9 is connected to the measuring instrument. The cable 9 of the measuring instrument 10 passes through the sealer 3. The sealer 3 is installed on the blowout preventer 15 to ensure that the cable moves in the sealer and the well is in a sealed state.

[0046] The top outlet 1 of the annular space 12 is connected to the recovery tank 14 through the annular space pipeline. The side wall outlet 11 of the blowout preventer 15 is connected to the ground pump truck 13 through the pipeline. An annular space gate 2 and a pipeline gate 4 are arranged on the annular space pipeline.

[0047] 2) Calculate the fluid loss Q1 in the negative pressure oil well.

[0048] Open the annular space gate 2 and the tubing gate 4, and the surface pump truck 13 injects formation water from the area where the negative pressure well is located into the tubing 5 until the formation water flows out from the annular space outlet 1. Then, close the annular space gate 2 and the tubing gate 4 in sequence.

[0049] After waiting time t, the measuring instrument 10 is moved downwards to log until the logging value of the measuring instrument 10 jumps, that is, the measuring instrument 10 contacts the static fluid surface inside the wellbore inside the tubing 5. The measuring instrument 10 measures the height L from the top of the casing 6 to the static fluid surface inside the wellbore. If the logging requirements are met, the formation water loss Q1 in the wellbore is calculated, and then step 3 is executed.

[0050] The formation water loss in the well is Q1 = the cross-sectional area of ​​the casing S × the height L from the top of the casing 6 to the static fluid level inside the wellbore;

[0051] Waiting time t = total depth of all measured formations s ÷ logging speed v of measuring instrument 10.

[0052] Q1 unit m 3 S unit m 2 L is in meters (m); t is in hours (h); s is in meters (m); v is in meters per hour (m / h)

[0053] The specific requirements for logging compliance are: the height of the static fluid level inside the wellbore from the top of the uppermost formation being measured is not less than 200 meters; if the height of the static fluid level inside the wellbore from the top of the uppermost formation being measured is less than 200 meters, then the logging compliance is not met.

[0054] If the logging requirements are not met, based on the geological structure, reservoir thickness and physical property changes, injection-production relationship and basic data of the development unit where the drilling well and adjacent wells are located: if the adjacent well's production layer is the same as this well's production layer, the adjacent well should be shut down and production stopped. The height of the static fluid level in the wellbore from the top of the uppermost measuring formation should be measured again. If the logging requirements are met, it indicates that the production of the adjacent well has caused a decrease in the energy of the entire production formation. The fluid in this well should be reversed into the measuring formation until the height of the static fluid level in the wellbore from the top of the uppermost measuring formation meets the logging requirements. Then, continue with step 4) logging. If the height of the static fluid level in the wellbore from the top of the uppermost measuring formation still does not meet the logging requirements, inject a plugging agent solution into the wellbore through a surface pump truck until the logging requirements are met. Then, continue with step 4) logging.

[0055] If the logging requirements are not met, based on the geological structure, reservoir thickness and physical property changes, injection-production relationship and basic data of the development unit where the drilling well and adjacent wells are located, if the production layer of the adjacent well is different from that of this well, the adjacent well is not shut down, and the adhesive solution is directly injected into the well through the surface pump truck until the logging requirements are met, and then step 4) logging is continued.

[0056] The plugging agent will automatically and completely unblock within 2 to 4 hours after logging.

[0057] 3) Prepare boric acid solution

[0058] Prepare boric acid solution according to the formation water loss Q1 in the well;

[0059] The total amount of boric acid solution W = wellbore volume A + (5~8) times the formation boron infiltration Q2 + formation water loss Q1 in the well;

[0060] Wellbore volume A = Casing cross-sectional area S × Well depth H

[0061] Formation boron permeation rate Q2=[π(r1+r2)] 2 -πr12 ]×h

[0062] In the formula, r1 is the casing radius; r2 is the instrument detection length; and h is the total length of all measured strata in meters.

[0063] W unit m 3 Unit A: m 3 Q2 unit m 3 H is in meters; r1 is in meters; r2 is in meters; h is in meters.

[0064] The volume concentration of the boric acid solution was 20 g / L. The measured value when the boric acid solution concentration was 20 g / L was more than 1.6 times greater than that when using fresh water (boron solution concentration 0 g / L), indicating that a boron solution concentration of 20 g / L is more suitable for fresh water formations.

[0065] Preparation of boric acid solution: Use boric acid with a content greater than 99%, use formation water from negative pressure oil well areas, and the temperature of the formation water should not be less than 50℃, preferably 50-80℃.

[0066] 4) Well logging

[0067] The measuring instrument 10 is lowered to the bottom of the last measuring stratum, and then the measuring instrument 10 is raised to the top of the uppermost measuring stratum to perform baseline measurement. After the baseline measurement is completed, the measuring instrument is lowered to the bottom of the last measuring stratum, and the oil casing annular space gate 2 and the oil pipe gate 4 are opened in sequence. The ground pump truck 13 injects boric acid solution into the oil pipe 5.

[0068] When the injection volume is the casing 6 volume, close the oil-casing annular space gate 2; continue injecting boric acid solution until at least one time the formation boron permeation volume Q2 is injected, so that the boric acid solution replaces the formation water; in order to ensure that the oil in the formation does not move when injecting boric acid solution, the boric acid solution injection rate is not less than the formation water leakage rate v (always ensure that the casing liquid level does not drop).

[0069] Formation water loss rate v = formation water loss in well Q1 ÷ waiting time t;

[0070] V unit m 3 / h;

[0071] Continue injecting boric acid solution at an injection rate not less than the formation water loss rate v, and begin measuring the formation boric acid content curve until all the prepared boric acid solution has been injected and the curve measurement is completed.

[0072] Since it is a negative pressure oil well, the surface pump truck 13 does not need to apply too much injection pressure when injecting boric acid solution. The boric acid solution can easily enter the annular space of the oil casing and cover the measured formation. Therefore, the boric acid injection pressure of the surface pump truck 13 is not greater than 0.5 MPa.

[0073] This invention, boron injection logging, involves replacing the water in the formation with boric acid. By measuring the formation capture section twice, the water flooding status and remaining oil saturation of the formation are determined. The original formation capture section measurement is related to the concentration of formation water salinity. The replacement capture section measurement is related to the concentration of the boric acid aqueous solution.

[0074] In the indoor simulated well, boron solutions with concentrations of 0, 10, 20, 30, and 40 g / L were injected for testing. The experimental results are shown in Table 1. According to the interpretation requirements of neutron lifetime logging data, the difference between the two measurements of Σ value should be greater than 1.6 times. The results can basically meet the actual formation conditions.

[0075] As shown in Table 1, the measured values ​​when the boron solution concentration is 20 g / L are more than 1.6 times greater than those when using fresh water (boron solution concentration 0 g / L), indicating that a boron solution concentration of 20 g / L is more suitable for fresh water formations. Therefore, a boron solution concentration of 20 g / L is selected for preparing boric acid.

[0076] Table 1

[0077]

Claims

1. A method for boron injection neutron lifetime logging in negative pressure oil wells, characterized in that: The lifetime logging method is as follows: 1) Installation at the head of a negative pressure oil well The casing (6) is passed through all the measuring formations (7) of the negative pressure oil well until the bottom of the casing (6) is lower than the bottom of the measuring formation. The tubing (5) is placed inside the casing (6) until the bottom of the tubing (5) passes through all the measuring formations (7). The casing (6) wall located at the measuring formation (7) has perforation holes. An annular space (12) is formed between the casing (6) and the tubing (5). The blowout preventer (15) is connected to the top of the tubing (5) and communicates with the tubing (5). The measuring instrument (10) is placed inside the blowout preventer (15). The top outlet (1) of the annular space of the oil jacket (12) is connected to the recovery tank (14) through the annular space pipeline of the oil jacket. The outlet (11) of the side wall of the blowout preventer (15) is connected to the ground pump truck (13) through the oil pipeline. An annular space gate (2) is arranged on the annular space pipeline of the oil jacket, and an oil pipeline gate (4) is arranged on the oil pipeline. 2) Calculate the fluid loss Q1 in the negative pressure oil well. Open the annular space gate (2) and the tubing gate (4), and the surface pump truck (13) injects formation water from the area where the negative pressure well is located into the tubing (5) until the formation water flows out from the annular space outlet (1). Then, the annular space gate (2) and the tubing gate (4) are closed in sequence. After waiting time t, the measuring instrument (10) will log downwards until the logging value of the measuring instrument (10) jumps. The measuring instrument (10) will measure the height L from the top of the casing (6) to the static liquid level in the well. If the logging requirements are met, the formation water loss Q1 in the well will be calculated, and then step 3 will be executed. The formation water loss in the well is Q1 = the cross-sectional area of ​​the casing S × the height LL from the top of the casing 6 to the static fluid level inside the wellbore; 3) Prepare boric acid solution Prepare boric acid solution according to the formation water loss Q1 in the well; The total amount of boric acid solution W = wellbore volume A + (5~8) times the amount of boron seepage into the formation Q2 + the amount of formation water loss in the well Q1; 4) Well logging The measuring instrument (10) is lowered to the bottom of the last measuring formation, and then the measuring instrument (10) is raised to the top of the uppermost measuring formation to perform baseline measurement. After the baseline measurement is completed, the measuring instrument is lowered to the bottom of the last measuring formation, and the oil casing annular space gate (2) and the tubing gate (4) are opened in sequence. The surface pump truck (13) injects boric acid solution into the wellbore. When the injection volume is equal to the casing (6) volume, close the annular space gate (2) of the oil casing; continue injecting boric acid solution until at least one time the formation boron permeation volume Q2 is injected, so that the boric acid solution replaces the formation water; continue injecting boric acid solution and start measuring the formation boric acid content curve until all the prepared boric acid solution is injected and the curve measurement is completed.

2. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 2), if the logging requirements are not met, based on the geological structure, reservoir thickness and physical property changes, injection-production relationship and basic data of the development unit where the drilling well and adjacent wells are located: if the adjacent well's production layer is the same as the drilling layer of this well, the adjacent well should be shut down and production stopped. The height of the static fluid level in the wellbore from the top of the uppermost measuring formation should be measured again. If the logging requirements are met, it indicates that the production of the adjacent well has caused a decrease in the energy of the entire production formation. The fluid in the well should be reversed into the measuring formation until the height of the static fluid level in the wellbore from the top of the uppermost measuring formation meets the logging requirements. Then, continue with step 4) logging. If the height of the static fluid level in the wellbore from the top of the uppermost measuring formation does not meet the logging requirements, a plugging agent solution should be injected into the well through a surface pump truck until the logging requirements are met. Then, continue with step 4) logging.

3. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 2), if the logging requirements are not met, based on the geological structure, reservoir thickness and physical property changes, injection-production relationship and basic data of the development unit where the drilling well and adjacent wells are located, if the mining layer of the adjacent well is different from that of this well, the adjacent well is not shut down, and the adhesive solution is directly injected into the wellbore through the surface pump truck until the logging requirements are met, and then step 4) logging continues.

4. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, 2, or 3, characterized in that: In step 2), the logging requirements are: the height of the static fluid level in the wellbore from the top of the uppermost formation being measured is not less than 200 meters; if the height of the static fluid level in the wellbore from the top of the uppermost formation being measured is less than 200 meters, then the logging requirements are not met.

5. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 2 or 3, characterized in that: The adhesive will automatically and completely unblock within 2 to 4 hours after logging.

6. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 1), the cable (9) of the measuring instrument (10) passes through the sealer (3), which is mounted on the blowout preventer (15).

7. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 2), the waiting time t = the sum of the depths of all measured formations s ÷ the logging speed v of the measuring instrument (10).

8. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 3), the volume concentration of the boric acid solution is 20 g / L.

9. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 3), the boric acid solution is prepared by using boric acid with a content greater than 99%, using formation water from a negative pressure oil well area, and the temperature of the formation water is 50-80℃.

10. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 3), the wellbore volume A = casing cross-sectional area S × well depth H Formation boron permeation rate Q2=[π(r1+r2)] 2 -πr1 2 ]×h In the formula, r1 is the casing radius; r2 is the instrument detection length; and h is the total length of all measured strata in meters.

11. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 4), the boric acid solution injection rate is not less than the formation water loss rate v. Formation water loss rate v = formation water loss in well Q1 ÷ waiting time t.

12. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 4), the boric acid solution injection pressure of the ground pump truck (13) shall not exceed 0.5 MPa.

13. The method for boron injection neutron lifetime logging in negative pressure oil wells according to claim 1, characterized in that: In step 4), boric acid solution is injected at an injection rate not less than the formation water loss rate v. Formation water loss rate v = formation water loss in well Q1 ÷ waiting time t.

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