A pulsed neutron logging tool calibration system and method

Abstract

The present invention belongs to the technical field of oil exploration and development testing technology, and specifically relates to a pulse neutron logging instrument calibration system and method. The calibration system includes a casing and a simulated core ring; the simulated core ring is a hollow cylinder, which is arranged in layers to simulate rock formations with different physical properties, and the number of layers is at least two; the casing has an inner hole, and the inner hole is used to place the pulse neutron logging instrument to be calibrated; the casing is axially arranged in the simulated core ring. The pulse neutron logging instrument calibration system of the present invention uses a simulated core ring to simulate formations with various physical properties, and the pulse neutron logging instrument can be calibrated in different physical property formation environments by placing the pulse neutron logging instrument in different positions in the casing, so that there is no need to use the calibration well group in the prior art to calibrate the pulse neutron logging instrument, which overcomes the problems of long calibration time and low efficiency, and only one well is needed to complete the calibration of the pulse neutron logging instrument.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum exploration and development testing technology, and in particular relates to a pulse neutron logging instrument calibration system and method. Background Art

[0002] Pulsed neutron logging plays a very important role in determining the distribution of remaining oil and reservoir physical parameters. The logging principle is that high-energy neutrons react with elements in the formation through inelastic scattering, elastic scattering, capture and activation, releasing secondary gamma rays of different energies, such as inelastic scattering gamma rays, captured gamma rays and activated gamma rays. By recording these gamma rays and using different processing methods to obtain the physical parameters of the formation skeleton and fluid, the remaining oil and gas distribution and reservoir production are determined.

[0003] The response of pulsed neutron logging instruments changes with the change of reservoir physical properties. The conversion of pulsed neutron logging instrument responses into geological parameters of the formation must be achieved by initial calibration of calibration wells. Schlumberger and other well-established logging instrument companies abroad have spent huge sums of money to establish calibration well groups in order to ensure the test accuracy and interpretation compliance of pulsed neutron logging instruments. The calibration well group established by the China National Petroleum Corporation Logging Company in China consists of 26 wells in the neutron porosity calibration well group, 7 wells in the carbon-oxygen ratio standard calibration well group, and 10 wells in the neutron lifetime standard calibration well group. These different well groups, one well simulates a formation, and each well is used to simulate various formations, with different porosity, fluid, layer thickness and other well conditions. These wells are constructed using the natural rock block method, accumulation method, slab superposition method, and proportioning method.

[0004] However, in addition to being used to calibrate the pulsed neutron logging instrument, these well groups also have other roles and functions. The calibration cycle of the pulsed neutron logging instrument is 3 months. If the well group is used for calibration every time, it may take a long time to wait until the well group is idle before using it to calibrate the pulsed neutron logging instrument, which is inefficient. Moreover, each calibration work needs to be completed in one well, and then the pulsed neutron logging instrument needs to be taken out and put into another well for calibration. The operation is well by well, and the process is cumbersome, the calibration time is long, and the work efficiency is low. If a new well group is built, the construction process will be complicated, the land area will be large, and the cost will be high. Summary of the invention

[0005] The present invention provides a pulse neutron logging instrument calibration system and method, which are used to solve the problems of low work efficiency caused by using the calibration well group in the prior art to perform pulse neutron logging instrument calibration or high cost caused by building a new well group.

[0006] In order to solve the above technical problems, the technical solution of the present invention includes:

[0007] The present invention provides a pulse neutron logging instrument calibration system, comprising a casing and a simulated core ring;

[0008] The simulated core ring is a hollow cylinder, which is arranged in layers to simulate rock layers with different physical properties, and the number of layers is at least two;

[0009] The casing has an inner hole, and the inner hole is used for placing a pulse neutron logging instrument to be calibrated; the casing is axially arranged in a simulated core ring.

[0010] The beneficial effects of the above technical solution are as follows: the pulse neutron logging instrument calibration system of the present invention uses a simulated core ring to simulate various formations with different physical properties. The pulse neutron logging instrument can be calibrated in different physical property formation environments by placing the pulse neutron logging instrument in different positions in the casing. There is no need to use the calibration well group in the prior art to calibrate the pulse neutron logging instrument, which overcomes the problems of long calibration time and low efficiency. The calibration of the pulse neutron logging instrument can be completed in one well. The system is simple, reliable and low-cost.

[0011] Furthermore, in order to firmly fix the casing, a cement injection cavity is formed between the inner wall of the simulated core ring and the outer wall of the casing for injecting cement for cementing.

[0012] Furthermore, in order to prevent radiation damage to the staff, an annular well is also arranged around the outer wall of the casing, and the annular well includes an inner tube and an outer tube. The inner tube is arranged inside the outer tube, and the cavity formed between the inner tube and the outer tube is used to inject pure water for radiation protection.

[0013] Furthermore, in order to firmly fix the casing, a vertical hole is provided at the bottom of the annular well for fixing the casing, and the inner diameter of the vertical hole is larger than the outer diameter of the casing.

[0014] Furthermore, in order to enable the pulse neutron logging instrument to perform logging calibration at different speeds, the calibration system also includes a connecting cable, one end of which is used to connect the pulse neutron logging instrument to be calibrated, and the other end is connected to the driving mechanism to enable the pulse neutron logging instrument to calibrate different layers.

[0015] The present invention also provides a pulse neutron logging tool calibration method, comprising the following steps:

[0016] Place the pulse neutron logging instrument into the sleeve of the pulse neutron logging instrument, and adjust the parameters of the pulse neutron logging instrument so that the energy values ​​of each characteristic peak and the nominal value of the energy peak are within the set characteristic energy error range; wherein the pulse neutron logging instrument comprises a casing and a simulated core ring; the simulated core ring is a hollow cylinder, which is arranged in layers to simulate rock formations with different physical properties, and the number of layers is at least two; the casing has an inner hole, and the inner hole is used to place the pulse neutron logging instrument to be calibrated; the casing is axially arranged in the simulated core ring;

[0017] The pulse neutron logging instrument is placed in the sleeve and located at different positions so that the pulse neutron logging instrument can measure rock formations with different physical properties, measure and determine the calibration parameter value, compare the obtained calibration parameter value with the corresponding nominal value, and judge whether the deviation between the two is within the set error range. If the deviation between the two is not within the set error range, adjust the parameters of the pulse neutron logging instrument until the deviation between the two is within the set error range to complete the calibration of the pulse neutron logging instrument; wherein the nominal value is the calibration parameter value obtained when the calibrated pulse neutron logging instrument is aimed at the rock formation with corresponding physical properties for measurement.

[0018] The beneficial effects of the above technical solution are as follows: the calibration system adopted by the pulse neutron logging instrument calibration method of the present invention includes a simulated core ring, which is used to simulate various formations with different physical properties. The pulse neutron logging instrument can be calibrated to formations with different physical properties by controlling the pulse neutron logging instrument to move up and down in the casing, and the calibration of the pulse neutron logging instrument can be completed without using a calibration well group. The present invention overcomes the problems of long calibration time and low efficiency, and the calibration of the pulse neutron logging instrument can be completed with only one well. The system is simple, reliable and low-cost.

[0019] Furthermore, when calibrating the pulsed neutron logging tool in different logging modes, the pulsed neutron logging tool is lifted up or lowered down at different speeds so that the pulsed neutron logging tool is located at different positions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a half-section schematic diagram of an annular well of the present invention;

[0021] Figure 2 It is a half-section schematic diagram of the annular well and pipe string structure of the present invention;

[0022] Figure 3 It is a cross-sectional schematic diagram of the pulse neutron logging tool calibration system of the present invention after the simulated core ring is installed;

[0023] Figure 4 It is a cross-sectional schematic diagram of a pulsed neutron logging tool calibration system of the present invention;

[0024] Figure 5 It is a flow chart of the pulse neutron logging tool calibration process and method of the present invention;

[0025] Among them, 1 to 7 are simulated core rings, 8 is a cylindrical space, 9 is an annular cover plate, 10 is an annular well, 11 is an annular space, 12 is a logging cable, 13 is a pulse neutron logging instrument, 14 is a cement ring, 15 is a casing, and 16 is a vertical hole. DETAILED DESCRIPTION

[0026] System Example:

[0027] The present invention provides a pulse neutron logging instrument calibration system, comprising an annular well 10, an annular cover plate 9, a casing 15, simulated core rings 1-7 and a logging cable 12.

[0028] like Figure 1 As shown, an annular well 10 is arranged below the ground surface, the bottom is sealed, and an annular cover plate 9 is arranged on the upper part. The annular well is built with bricks and cement, and includes an inner tube and an outer tube. The inner tube is sleeved in the outer tube. The cavity formed by the inner tube is a cylindrical space 8. The cavity formed between the inner tube and the outer tube is an annular space 11. The annular space 11 is used to be filled with pure water before calibrating the pulse neutron logging instrument, and is used as a radioactive protection layer of the pulse neutron logging instrument to ensure the safety of the workers.

[0029] like Figure 2 , 3 As shown, a casing 15 and simulated core rings 1 to 7 are arranged in the cylindrical space 8. The simulated core rings 1 to 7 are hollow cylinders, which are arranged in layers. Sandstone particles (limestone particles) and mudstone particles simulate the rock skeleton. Chemical industrial raw materials of different proportions are mixed with pure water to simulate the fluid. They are installed using the proportioning method and the stacking compaction method. Among them, the proportioning method is to mix a certain proportion of pure water with different chemical industrial raw materials to simulate the fluid in the casing and the reservoir; the stacking compaction method is to use sand and mudstone particles of a certain particle size mixed with fluid to simulate the reservoir layer in a stacked compacted state. According to the designed porosity and oil (water) saturation, stacking and compaction are performed to form layers, and each layer is used to simulate strata with different physical properties. Figure 3 The simulated core rings in the instrument are divided into seven layers. According to the calibration scheme of the pulsed neutron logging instrument, the simulated core rings can be designed and replaced according to the needs to adjust the physical property parameters of the simulated formation.

[0030] like Figure 2 As shown, the casing 15 has an inner hole, and the inner hole is used to place the pulse neutron logging tool 13 to be calibrated (such as Figure 4As shown). The casing 15 is axially arranged in the simulated core ring 10. A cement ring 14 is arranged in the cement injection cavity between the inner wall of the simulated core ring 10 and the outer wall of the casing 15. The cement ring is fixed outside the casing and is evenly and tightly attached to the outer circle of the casing for injecting cement for cementing. According to the calibration scheme of the pulse neutron logging instrument, the casing (including the casing and the cement ring) can be designed and replaced according to the needs to adjust different pipe string structures.

[0031] A protruding vertical hole 16 is provided at the bottom center of the annular well. The vertical hole 16 is coaxial with the annular well 10. The inner diameter of the vertical hole 16 is larger than the outer diameter of the cement ring 14. It is used to fix the casing 15 so that the bottom of the casing protrudes from the bottom of the simulated core ring to make the casing fixed more securely.

[0032] One end of the logging cable 12 is connected to the pulse neutron logging instrument to be calibrated, and the other end is connected to the power supply equipment through the logging winch. The pulse neutron logging instrument is powered by the power supply equipment, and the cable is retracted and released through the logging winch at the same time, so that the pulse neutron logging instrument can calibrate different layers, and the pulse neutron logging instrument can be lifted up for logging calibration at different speeds.

[0033] Method Example:

[0034] Based on the pulse neutron logging tool calibration system introduced in the above system embodiment, a pulse neutron logging tool calibration method of the present invention can be implemented to calibrate the pulse neutron logging tool. The process is as follows:

[0035] Step 1: According to the calibration scheme of the pulse seed logging instrument, select appropriate casing and corresponding cement ring, lower the casing into the vertical hole of the annular well, and fix the cement ring on the outside.

[0036] Step 2: According to the calibration requirements, simulated core rings are installed using the proportioning method and the stacking and compaction method to simulate the fluid and rock skeleton of the reservoir.

[0037] Step 3: Connect the pulse neutron logging instrument to the cable and power it on. Use the logging winch to lower the cable and lower the pulse neutron logging instrument to the bottom of the casing in the pipe string at a uniform speed.

[0038] Step 4: calibrate the three logging modes of neutron lifetime, carbon-oxygen ratio, and gamma spectrum. According to the calibration data, adjust the parameters of the pulse neutron logging instrument, repeat multiple calibration modes and record the test data for calculation until the various indicators of the pulse neutron logging instrument logging data are within the allowable error range.

[0039] Step 5, repeat steps 1 to 4 to simulate different string structures (casing specifications are different in different regions, and commonly used casing specifications are: 4in, 4 1 / 2in, 5 1 / 2in, 7in, 7 5 / 8in, etc.) and physical parameters, and perform corresponding calibration work.

[0040] Overall, the pulse neutron logging tool calibration system of the present invention does not need to use a calibration well group for calibration, thus overcoming the defects of long calibration time, high cost and complicated process.

[0041] A specific example is given below to illustrate the pulse neutron logging tool calibration system of the present invention.

[0042] like Figure 4 As shown, the annular well 10 in the system is an annular well with a depth of 12m, an outer diameter of 2.2m and an inner diameter of 1.2m. The upper part is an annular cover plate 9, and the middle is an annular space 11 with a diameter of 1.2m. There is a vertical hole 16 with a depth of 3m and a diameter of 0.3m at the bottom center of the annular well 10, which is used to fix the casing 15 and the cement ring 14. The casing is filled with pure water during calibration. The cement ring 14 is fixed on the outer circle of the casing 15, with a thickness of 0.03m and a height of 7.5m.

[0043] It should be noted that the real pulse neutron logging is to go down into the well (the layer depth is below 1000 meters) to test the layer. The test media and objects include oil, gas, water, casing, cement ring and rock layer, which is a complex mixture. In order to accurately calibrate the test accuracy of the instrument, it must be calibrated with a pure medium. The calibration data can be more accurate. Therefore, the casing is filled with pure water during calibration.

[0044] Simulated core rings 1-7 are composed of mudstone particles with a porosity of 0%; sandstone particles (limestone particles) are configured according to porosities of 35%, 20%, and 10%; 1,3-butanediol aqueous solution is used as the simulated pore fluid to simulate the pore fluid with equivalent oil saturation, and the pores are filled with the pores according to Table 1. (When the ratio of 1,3-butanediol to water is 5:2, the equivalent oil saturation of 50% is reached.) The thickness of the simulated core rings is 2m, 1.5m, and 1m (the thickness is adjusted according to the design requirements of the scheme), the outer diameter is 1.2m, and the inner diameter is 0.17m (5 1 / 2in casing is selected) or the inner diameter is 0.21m (7in casing is selected) for stacking and compaction. The simulated core rings are arranged from bottom to top according to the sequence numbers in Table 1. The simulated pore fluid simulates the carbon and oxygen elements in the oil-water mixture in the reservoir, and its composition is required to be stable and safe, and a variety of oil saturation values ​​can be achieved according to the calibration requirements.

[0045] Table 1 Composition of simulated core ring

[0046]

[0047]

[0048] After the above preparations are completed, the annular space 11 can be filled with pure water to serve as a radioactive protection layer for the pulsed neutron instrument to ensure the safety of the staff. The cylindrical space 8 is filled with pure water during calibration. Filling the cylindrical space with pure water is to strengthen radioactive protection and to unify the medium of the space to reduce the impact of other media in the space on the instrument calibration.

[0049] like Figure 5 As shown, first, the pulse neutron logging instrument 13 is connected to the logging cable 12, and the logging cable 12 is lowered by the logging winch, and the pulse neutron logging instrument 13 is lowered to the bottom of the casing 15. The pulse neutron logging instrument 13 is powered and debugged. The logging time and energy spectrum are observed, and the instrument parameters are adjusted. The energy corresponding to each characteristic peak is shown in Table 2.

[0050] Table 2 Characteristic peak energy values ​​of pulsed neutron logging tool

[0051]

[0052] Before calibration in each mode, the logging cable 12 is lowered by the logging winch, and the pulse neutron logging instrument 13 is lowered to the bottom of the casing 15. The pulse neutron logging instrument 13 is pulled up for logging calibration in three modes according to the speed indicated in Table 3, and all the logging time spectrum and energy spectrum curves are recorded.

[0053] Table 3 Logging modes and speeds of pulsed neutron logging tools

[0054]

[0055] Then, the logging data of different modes are read out according to the logging time and energy spectrum curve, recorded in Table 4, Table 5, and Table 6, and the oil saturation and water saturation are calculated.

[0056] The energy spectrum time spectrum interpretation model of the present invention meets the condition that the formation porosity and lithology remain unchanged, and the relationship between the oil saturation S0 and the C / O value is:

[0057]

[0058] Where S0 is the oil saturation of the calibration layer, (C / O) log is the measured carbon-oxygen ratio, (C / O) w is the carbon-oxygen ratio of the water layer, (C / O) o is the carbon-oxygen ratio of the oil layer.

[0059] Water saturation S w The relationship between and ∑ is:

[0060]

[0061] Among them, S w is the water saturation of the calibration layer, ∑ is the thermal neutron macroscopic capture cross section of the calibration layer, and Φ is the porosity of the calibration layer; ∑ ma is the thermal neutron macroscopic capture cross section of the rock skeleton of the calibration layer;∑ sh is the thermal neutron macroscopic capture cross section of the calibration layer mud; ∑ w is the thermal neutron macroscopic capture cross section of the calibration layer water; ∑ o is the thermal neutron macroscopic capture cross section of the oil and gas in the calibration layer; V sh The mud content.

[0062] The method for obtaining the C / O nominal values ​​of the simulated core rings in Tables 4 and 5 is as follows: before calibration, a pulsed neutron instrument with small calibration error and high test accuracy is selected, and in the simulated calibration system and method, the middle of each core ring is measured by point measurement, and each point is measured 3 times, and the average value is obtained as the C / O nominal value of each simulated core layer.

[0063] Table 4 Pulse neutron logging instrument saturated water calibration record

[0064]

[0065] Table 5 Pulse neutron logging tool saturated oil calibration record

[0066]

[0067]

[0068] The nominal value of the thermal neutron capture cross section of the simulated core in Table 6 is obtained by stopping the calibrated pulse neutron instrument at a fixed point in the middle of the calibration layer for 3 measurements before calibration, and taking the average value.

[0069] Table 6 Pulse neutron logging tool life mode calibration record

[0070]

[0071] Next, according to the calibrated data of the pulse neutron logging instrument 13, the instrument parameters of the pulse neutron logging instrument 13 are adjusted. The above steps are repeated until the various logging data indicators of the pulse neutron logging instrument 13 are within the allowable error range, and the calibration work is completed.

Claims

1. A pulsed neutron logging tool calibration system, characterized in that: Includes casing, simulated core ring and connecting cables; The simulated core ring is a hollow cylinder, which is arranged in layers to simulate rock layers with different physical properties, and the number of layers is at least two; The casing has an inner hole, and the inner hole is used to place the pulse neutron logging instrument to be calibrated; the casing is axially arranged in the simulated core ring; a cement injection cavity is formed between the inner wall of the simulated core ring and the outer wall of the casing, and is used to inject cement for cementing; One end of the connecting cable is used to connect the pulse neutron logging instrument to be calibrated, and the other end is connected to the driving mechanism, so that the pulse neutron logging instrument can calibrate different layers.

2. The pulsed neutron logging tool calibration system according to claim 1, characterized in that: An annular well is also arranged around the outer wall of the casing, and the annular well comprises an inner tube and an outer tube. The inner tube is sleeved in the outer tube, and the cavity formed between the inner tube and the outer tube is used to inject pure water for radioactive protection.

3. The pulsed neutron logging tool calibration system according to claim 2, characterized in that: A vertical hole is provided at the bottom of the annular well for fixing the casing, and the inner diameter of the vertical hole is larger than the outer diameter of the casing.

4. A calibration method for a pulsed neutron logging tool calibration system, characterized in that: The steps include: The pulse neutron logging instrument is placed in the casing of the pulse neutron logging instrument calibration system, and the pulse neutron logging instrument parameters are adjusted so that the energy values ​​of each characteristic peak and the nominal value of the energy peak are within the set characteristic energy error range; wherein the pulse neutron logging instrument calibration system comprises a casing and a simulated core ring; the simulated core ring is a hollow cylinder, which is arranged in layers to simulate rock formations with different physical properties, and the number of layers is at least two; the casing has an inner hole, and the inner hole is used to place the pulse neutron logging instrument to be calibrated; the casing is axially arranged in the simulated core ring; The pulse neutron logging instrument is placed in the casing and located at different positions so that the pulse neutron logging instrument can measure rock formations with different physical properties, measure and determine the calibration parameter value, compare the obtained calibration parameter value with the corresponding nominal value, and judge whether the deviation between the two is within the set error range. If the deviation between the two is not within the set error range, adjust the parameters of the pulse neutron logging instrument until the deviation between the two is within the set error range to complete the calibration of the pulse neutron logging instrument; wherein the nominal value is the calibration parameter value obtained when the calibrated pulse neutron logging instrument is aimed at the rock formation with corresponding physical properties for measurement.

5. The calibration method for a pulsed neutron logging tool calibration system according to claim 4, characterized in that: When calibrating the pulse neutron logging tool under different logging modes, the pulse neutron logging tool is lifted up or lowered at different speeds so that the pulse neutron logging tool is located at different positions.

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