CN112761623B

CN112761623B - Method for selecting marker for oilfield logging

Info

Publication number: CN112761623B
Application number: CN202110105554.8A
Authority: CN
Inventors: 刘建; 赵燕梅; 梅坚; 任丽容
Original assignee: Sichuan Songyun Technology Co ltd
Current assignee: Sichuan Songyun Technology Co ltd
Filing date: 2021-01-26
Publication date: 2024-06-25
Anticipated expiration: 2041-01-26

Abstract

The application discloses a method for selecting a marker for oilfield logging, which comprises the following steps: (a) Selecting elements capable of participating in neutron activation treatment, and calculating element factors S of the selected elements according to the following formula (1): s=θ.σ.β.γ/M (1); (b) According to the measurement result of the step a, sorting the elements from big to small according to the S factor, and initially selecting the element with the front sorting; then, gamma-ray interference is removed from the initially selected elements, namely, only the elements with large S factors are reserved in the elements with the characteristic gamma-ray signal interference; the last element left is the marking element. The application provides a totally new marker selection method, which can accurately restore the flow of production fluid at each target position in the well and the proportion of water and crude oil in the production fluid through matching with trace analysis. Meanwhile, the application does not damage the normal running state of the horizontal well, can effectively reduce the system error and improve the accuracy and reliability of the measurement result.

Description

Method for selecting marker for oilfield logging

Technical Field

The application relates to the field of oilfield exploitation, in particular to the field of underground measurement of oilfield exploitation, and specifically relates to a marker selection method for oilfield logging. The application provides a novel method for selecting a marker for oil field logging, which provides a novel idea for selecting the marker. The oil field logging marker obtained based on the selection method and the trace analysis can accurately restore the proportion of water and crude oil in the production liquid at each target position in the well.

Background

The horizontal well production profile test is a difficult problem in the field of petroleum logging, and relates to the following aspects:

1) Accessibility problems

The traditional instrument descends into the well by self gravity, and after the instrument string reaches the vicinity of the deflecting, the instrument string is difficult to continue to travel; for this purpose, the schlenz company specially designs MaxTRAC crawlers which drag the signal cable and the power cable and bring the instrument string into the horizontal section; however, once the horizontal section is longer, or the track of the well is bent and fluctuated, or the sleeve is deformed, the crawler is easy to block, and even is blocked in the horizontal section, so that accidents are caused;

2) Problem of production test

The traditional instrument is driven underground by a cable, and because of the existence of the instrument and the cable, the production fluid is lifted to the ground by adopting an unconventional mode such as gas lift and the like, so that the fluid flows, and the parameters are measured; the measures objectively change the flowing environment of the whole horizontal section, so that deviation between test data and real data in normal production is easy to occur, and a test conclusion is inaccurate;

3) Problem of adaptation to severe conditions downhole

The traditional instrument is mainly composed of electronic devices, and the electronic devices are most suitable for working in a normal temperature environment; when the instrument is operated in a high temperature downhole environment for a long period of time, problems of instrument operating point drift may occur, and even instrument failure may be caused.

In order to solve the well logging problem of the horizontal well, the industry also has the function of carrying out test work by using a layered sampling method. The oil pipe is used for carrying the separator to the horizontal section, the oil pipe is separated section by section, the oil pipe is mined and sampled in a layered mode, and independent flow parameters of each section are respectively obtained. During normal production, the flow field of the underground horizontal section is in a complex dynamic balance process, the parameter of a certain layer section is obtained in isolation, and the real state of the layer section is hard to characterize during normal production.

Currently, markers for oilfield logging typically employ water-soluble or oil-soluble markers that are released at a particular profile and sampled at the wellhead to obtain the water or oil content of the corresponding fluid profile. However, when a horizontal well is marked with a normal marker, the normal marker must reach a certain release rate in order to reach the measurement standard. Since the diameter of the oil pipe is a certain value, the diameter of the common marker must be smaller than that of the oil pipe, and since the common marker must reach a certain release speed, the release time of the common marker is in a certain range, basically less than three months, and even shorter. This presents a problem in that common markers can only be measured over a certain time frame (e.g., three months) during horizontal well operation. When full cycle measurements are required for horizontal wells, the common markers need to be replaced repeatedly. When the common marker is replaced, the oil pipe connected with the release device is required to be taken out, the common marker is replaced, and then the oil pipe connected with the replaced common marker is replaced in the well. By adopting the mode, when the common marker is replaced, well stopping operation is needed, normal operation of an oil well is affected, and labor and replacement cost are high.

For this reason, a new method and/or apparatus is urgently needed to solve the above-mentioned problems.

Disclosure of Invention

The application aims to provide a method for selecting a marker for oilfield logging. The application provides a totally new marker selection method, which can accurately restore the flow of production fluid at each target position in the well and the proportion of water and crude oil in the production fluid through matching with trace analysis. Meanwhile, the application does not damage the normal running state of the horizontal well, can effectively reduce the system error and improve the accuracy and reliability of the measurement result.

When the application is used, the release device is distributed along with the oil pipe at each target position under the horizontal oil well (namely, the release device is directly connected with the oil pipe). After the laying is completed, the oil well performs normal production operation. When the product flows through the releasing device, the releasing device releases water-soluble substances (inert when contacting oil) and oil-soluble substances (inert when contacting water), and the release amount of the water-soluble substances is related to the product flow and the oil and water contents. The production fluid is sampled by a worker at regular intervals on the well. And through post-treatment and data analysis of the produced liquid sample, the flow of the produced liquid at each target position in the well and the proportion of water and crude oil in the produced liquid can be accurately reduced, so that the purpose of production logging is realized. Based on the totally new marker selection method, the application of the selected marker in oilfield logging and the adoption of trace analysis, the method can be used for short-term test of a problem well for 5-10 days and also can be used for long-term monitoring of a production well for 3-5 years. For production well monitoring, the test period is effectively prolonged, the times of taking and placing operations of oil pipes and the labor intensity of workers are reduced, the test efficiency and the continuous operation time of the oil well are improved, which cannot be realized by the existing markers, and the method has obvious progress significance.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

The method for selecting the marker for the oilfield logging comprises the following steps:

(a) Selecting elements capable of participating in neutron activation treatment, and calculating element factors S of the selected elements according to the following formula (1):

S＝θ·σ·β·γ/M (1)，

in the formula (1), theta is element abundance (percentage), sigma is neutron action section (unit is bar), beta is decay branch ratio (percentage), gamma is absolute intensity (percentage) of rays, and M is atomic weight;

(b) According to the measurement result of the step a, sorting the elements from big to small according to the S factor, and initially selecting the element with the front sorting; then, gamma-ray interference is removed from the initially selected elements, namely, only the elements with large S factors are reserved in the elements with the characteristic gamma-ray signal interference; the last element left is the marking element.

In the step b, the selected marking elements are used for manufacturing water-based markers and oil-based markers, and the content of the corresponding elements can be determined by measuring the intensity of the characteristic gamma signals of the corresponding elements after neutron activation.

The prepared water-based marker is oxalic acid compound, and the prepared oil-based marker is stearic acid compound.

The water-based markers were made as follows: oxalic acid compound for water-based marking element is selected, and the molding is carried out under high temperature and high pressure, wherein the molding temperature is controlled between 20 ℃ below the melting point temperature of the corresponding oxalic acid compound and the melting point temperature, and the pressure is 8-20 MPa.

The oil-based markers were made as follows: stearic acid compound used for the oil-based marking element is selected, and is formed under high temperature and high pressure, wherein the forming temperature is controlled between 20 ℃ below the melting point temperature of the corresponding stearic acid compound and the melting point temperature, and the pressure is 8-20 MPa.

In the step b, selecting N elements with the largest S factors, and performing gamma-ray interference rejection in the selected elements, namely, only preserving the elements with the large S factors for the elements with gamma-ray interference; the remaining elements are marker elements.

The number of N is 10-40; preferably, N is 20.

In the step b, the selected series of marking elements comprises ：¹⁵¹Eu、¹⁹¹Ir、¹⁰⁹Ag、¹³³Cs、¹¹⁵In、¹⁵²Sm、⁵⁹Co、¹⁸⁷Re、¹³⁹La、¹⁵⁹Tb、¹⁷⁶Lu、¹⁸¹Ta、⁴⁵Sc、⁵⁵Mn、¹⁸⁰Hf、¹⁸⁶W、¹⁶⁹Tm、¹⁶⁴Dy、¹⁰³Rh、¹²¹Sb;

The prepared water-based marker is oxalic acid compound of a marking element, wherein the oxalic acid compound is soluble in water and insoluble in oil; the oil-based markers prepared are stearic acid compounds of the marker element, which are oil-soluble and water-insoluble.

The selected marking element is an element for measuring the liquid production profile of the horizontal oil well.

The method for measuring the section of the oilfield logging fluid by using the marker comprises the following steps:

(1) Making the series of marking elements into water-based markers and oil-based markers respectively;

(2) Placing one of the water-based markers and one of the oil-based markers in the step (1) together in a release device to form a marker test assembly, wherein different combinations of the water-based markers and the oil-based markers form different marker test assemblies;

(3) Determining the number and the installation positions of the marking test assemblies according to the determination requirement of the liquid production profile, and connecting the marking test assemblies with the oil pipe to form an oil pipe working unit;

(4) The oil pipe working unit is lowered to the underground to be measured, and the marking test assembly reaches a preset position; then, the oil well works normally and starts to produce;

(5) Sampling from the wellhead of the oil well according to the set time to obtain an oil well detection sample;

(6) And measuring and analyzing the oil well detection sample to obtain the produced liquid flow and the oil-water ratio data in the produced liquid corresponding to the industrial profile.

In the step 3, a hollow short section is adopted as a release device, and two ends of the release device are used for being connected with an oil pipe; two ends of the release device are provided with runner holes which are communicated with the inner cavity of the release device and the annular space of the sleeve; the marker testing assembly is located in the interior cavity of the release device.

The two ends of the release device are provided with runner holes along the circumference, and the runner holes at the two ends of the release device are respectively communicated with the inner cavity of the release device and the annular space of the sleeve.

The method is used for testing production wells;

or the method is used for problem finding of production wells which are out of production.

The method is used for searching the high water-bearing layer of the production well which is stopped.

In the step 6, the oil well detection sample is measured and analyzed, and the operation is as follows:

(c) Removing solid impurities, na ions and K ions in the oil well detection sample, and concentrating and enriching to obtain an irradiation sample;

(d) C, carrying out irradiation treatment on the irradiation sample prepared in the step c, and activating the marker element into an isotope with the atomic weight increased by 1 unit to obtain a sample to be detected;

(e) And (3) gamma-ray measurement is carried out on the sample to be detected, so that the content of the corresponding marker in the oil well detection sample before irradiation can be obtained.

In the step d, the irradiation treatment time is 10-60 h.

Preferably, the irradiation treatment time is 24 hours.

The application is used for measuring the flow rate and the oil-water ratio of different sections in the oil well production fluid.

The application is used for measuring the flow and the oil-water ratio of different sections in the horizontal oil well production liquid.

The method is used for measuring the flow rate of the produced liquid and the oil-water ratio of the fracturing layer section so as to evaluate the fracturing effect.

In the step 6, based on the measured irradiation intensity, the following formula (2) is adopted for calculation:

f(q,t)＝a₀+a₁·q²+a₂·q·t+a₃·t²+a₄·q+a₅·t (2);

In the formula (2): f is the marker content of the unit volume of the production fluid, and enough data samples can be obtained through periodic sampling and measurement; t is the working time (t is the time from the start of label release to the time of sampling); q is the flow rate of the marked liquid; a ₀、a₁、a₂、a₃、a₄、a₅ is a coefficient of each item.

Through calculation, the flow values of oil and water at the corresponding liquid production section can be obtained, and then the total flow and the oil-water ratio of the corresponding liquid production section can be calculated.

The application provides a method for selecting a marker for oilfield logging. Here, the working principle of the present application is explained as follows: according to the application, different oil-soluble substances (namely oil-based markers) and water-soluble substances (namely water-based markers) are arranged in each release device similar to a short joint of an oil pipe, and the release devices are directly connected with the oil pipe and then are put into a designated position along with the oil pipe; during normal production, the product flows through the release device, the oil-based marker in the release device can be dissolved and released when meeting oil, the water-based marker can be dissolved and released when meeting water, and the respective release quantity is related to the flow of the oil or water flowing through and the working time of the marker in the pit; sampling the produced liquid on the well in time intervals, and sending the sample to an analysis chamber for measurement; in the analysis chamber, the sample is activated by neutrons, so that the released substances in the sample have radioactivity, the gamma-ray measuring instrument is used for gamma-ray spectrometry of the activated sample, the content of different released substances in the sample is read through gamma-ray spectrometry, the contribution of oil and water in each layer section is calculated, the flow of the production fluid at each target position in the well and the proportion of water and crude oil in the production fluid are accurately reduced, and the purpose of production logging is achieved.

In earlier studies, the inventors found that when a horizontal well is marked with a normal marker, the normal marker must reach a certain release rate in order to reach a measurement standard. Since the diameter of the oil pipe is a certain value, the diameter of the common marker must be smaller than that of the oil pipe, and since the common marker must reach a certain release speed, the release time of the common marker is in a certain range, basically less than three months, and even shorter. This presents a problem in that common markers can only be measured over a certain time frame (e.g., three months) during horizontal well operation. When full life cycle measurements are required for horizontal wells, the common markers need to be replaced repeatedly. When the common marker is replaced, the oil pipe connected with the release device is required to be taken out, the common marker is replaced, and then the oil pipe connected with the replaced common marker is replaced in the well. By adopting the mode, when the common marker is replaced, well stopping operation is needed, normal operation of an oil well is affected, and labor and replacement cost are high.

As described above, the existing markers have defects in selection, and therefore, the application provides brand-new improvement on the selection of the markers for oilfield logging. According to the application, through the selection of the markers and the use of trace measurement, the flow of the liquid production sections of the oil wells with different levels and the accurate measurement of the oil-water ratio in the liquid production sections can be realized on the premise of greatly reducing the release rate of the markers. The application can be used for short-term test of a problem well for 5-10 days and long-term monitoring of a production well for 3-5 years by selecting the markers and adopting trace analysis. The application can meet the requirement of long-period and continuous measurement; the release period is greatly prolonged based on the release rate, the change of the marker object, on the premise of adopting the marker with the same quality as the common marker. Through practical measurement, the application can ensure that the release period of the marker can reach more than five years, even longer, and can completely meet the measurement requirement of the whole life cycle of the oil well. In short, the application can be fully realized, and the oil pipe is connected with the marker, and the operation of logging in the well once and the measurement of the whole period are carried out, which is a breakthrough innovation relative to the prior art. The application has breakthrough significance for measuring the liquid production profile of the oil well, and the existing oil well measuring mode is changed after the application is applied on a large scale.

In the application, the calculation of the flow rate of the liquid production profile not only depends on the content of the measured marker, but also increases the factors of the working time of the marker in the well. The common method for calculating the release of the marker is to pay attention to the content of the marker in the current production fluid only, and calculate the flow rate by using the content of the marker. The dissolution rate of the solid marker in the liquid in the method of the application is related not only to the movement speed of the liquid itself, but also to the surface area of the solid marker and the diffusion path of the marker molecules; in the dissolution process, the surface area of the marker and the diffusion path of the marker molecules change along with the deep development of dissolution behavior; in the application, the change of the surface area of the marker and the diffusion path of the marker molecules are integrated into the expression of the marker in the working time of the well. The calculation of the production profile of the whole life cycle of the well will become more accurate by the present application, taking into account the release process that the markers have taken place.

Drawings

The invention will now be described by way of example and with reference to the accompanying drawings in which:

Fig. 1 is a schematic view showing the installation of the release device in embodiment 1.

FIG. 2 is a schematic diagram of the installation of a plurality of marking test assemblies in an embodiment.

The marks in the figure: 1. the device comprises an oil pipe joint, 2, a runner, 3, an oil-based marker, 4, a water-based marker, 5, a device shell, 6, a diversion sleeve, 7, a runner hole, 8, a sleeve, 9, an oil pipe, 10 and an oil inlet nipple.

Detailed Description

All of the features disclosed in this specification, or all of the steps in a method or process disclosed, may be combined in any combination, except for mutually exclusive features and/or steps.

Any feature disclosed in this specification may be replaced by alternative features serving the same or equivalent purpose, unless expressly stated otherwise. That is, each feature is one example only of a generic series of equivalent or similar features, unless expressly stated otherwise.

In this embodiment, the specific operation of the horizontal well production profile test is as follows.

1. Marking element selection

In the application, the measurement of the marking element is to measure the radioactive gamma rays after neutron activation, and the content of the element is determined by the intensity of the characteristic gamma signal of each element. Therefore, the selected elements should comprehensively consider the following elements: element abundance θ, neutron action cross section σ, decay branch ratio β, absolute intensity of radiation γ, and atomic weight M. Based on these factors, an element selection factor S is set as shown in the following formula (1):

S＝θ·σ·β·γ/M (1)，

In formula (1), σ is in bar.

According to the formula (1) (namely an S factor calculation formula), calculating all elements capable of participating in neutron activation analysis, selecting a plurality of elements with larger S factors, and performing gamma-ray interference rejection in the selected elements, namely, reserving only the elements with large S factors in the elements with mutual interference of characteristic gamma-ray signals; the last element left is the marking element.

In this embodiment, 30 elements with the largest S factor are selected, and gamma-ray interference rejection is performed among the 30 elements. The following elements were finally determined as the relevant data for the markup element ：¹⁵¹Eu、¹⁹¹Ir、¹⁰⁹Ag、¹³³Cs、¹¹⁵In、¹⁵²Sm、⁵⁹Co、¹⁸⁷Re、¹³⁹La、¹⁵⁹Tb、¹⁷⁶Lu、¹⁸¹Ta、⁴⁵Sc、⁵⁵Mn、¹⁸⁰Hf、¹⁸⁶W、¹⁶⁹Tm、¹⁶⁴Dy、¹⁰³Rh、¹²¹Sb. by calculation and investigation one by one as shown in table 1 below.

TABLE 1 calculation of S factor

2. Marker preparation

The water-based markers were made as follows: oxalic acid compound for water-based marking element is selected, and the molding is carried out under high temperature and high pressure, wherein the molding temperature is controlled between 20 ℃ below the melting point temperature of the corresponding oxalic acid compound and the melting point temperature (for example, if the melting point temperature is T ℃, the corresponding molding temperature range is T-20 ℃ to T ℃), and the pressure is 8-20 MPa.

In this example, to simplify the subsequent data calculations, the water-based markers are the same shape and size as the oil-based markers. Specifically, the water-based marker prepared in the embodiment is of a columnar structure, the length of the water-based marker is 50cm, and the diameter of the water-based marker is determined according to different borehole sizes; the prepared oil-based marker is of a columnar structure, the length of the oil-based marker is 50cm, and the diameter of the oil-based marker is determined according to different borehole sizes.

3. Release device design

In this embodiment, as shown in fig. 1, the release device is designed as a hollow short section, and two ends of the short section are connected with the oil pipe joint. Meanwhile, the two ends of the short joint are circumferentially provided with runner holes, the runner holes are communicated with the inner cavity of the releasing device and the annular space of the casing, and the marker to be released is centrally placed in the inner cavity of the short joint. Meanwhile, the inlet end of the release device is provided with a horn-shaped flexible guide sleeve for guiding the liquid in the sleeve to flow into the runner hole. In fig. 1, two ends of the release device are respectively connected with the oil pipe joint; the releasing device is a hollow short section, the oil-based marker and the water-based marker are respectively positioned in the device shell of the short section, a runner is formed between the oil-based marker and the water-based marker and between the oil-based marker and the device shell, and runner holes are respectively arranged at two ends of the releasing device; meanwhile, a runner hole at one side of the nipple towards the bottom end of the well is matched with the diversion sleeve; the produced liquid at the bottom of the well can flow out from the flow passage hole at one side of the well mouth end through the nipple after passing through the flow guide sleeve, the flow passage hole at one side of the nipple and the flow passage in the release device in sequence.

During normal production, liquid flows from the bottom end to the wellhead end in the sleeve annulus and flows through the release device, and part of the liquid enters the release device and flows through the surface of the marker to be released due to the blocking and guiding of the guide sleeve; and then flows out from the runner hole at the downstream of the release device and returns to the casing annulus. When the liquid flows on the surface of the marker in the releasing device, the oil-based marker contacts with the oil and can be automatically released into the oil; the water-based markers will automatically release into the water when in contact with the water.

4. Logging process

Here, a production profile test procedure of one oil well will be described.

1) Carrying out device layout scheme design: i.e. determining which horizons of production profile need to be of particular interest, placing a release device at the location of interest, the test content comprising the flow rate of the profile and the proportion of oil and water. More specifically, as shown in FIG. 2, A, B, C, D, E are each five release devices, each of which can monitor the production profile parameters of the fluid arriving at the device location from the downhole direction.

2) At the logging site, the tubing is run downhole with all the release devices and all to the predetermined location.

3) And (5) starting production according to normal operation.

4) Fluid samples are taken from the wellhead at regular intervals.

5) And (5) conveying the sample liquid to an analysis chamber for measurement and analysis.

6) And calculating the profile data of each point according to the measured data.

5. Sample measurement

In the analysis chamber, processing and preparing the liquid sample, including filtering to remove solid impurities, removing Na and K ions in the liquid sample, concentrating and enriching the marker, and preparing the sample to obtain the irradiation sample. Then, the irradiated sample was irradiated with a neutron source for 24 hours, and the marker element was activated to an isotope whose atomic weight was increased by 1 unit. And (3) moving the irradiated sample into a lead shielding chamber, and measuring gamma rays by using a high-purity germanium detector.

Since each isotope of the marker elements emits gamma rays of specific energy when decaying, the respective contents of the various markers in the sample before irradiation can be calculated based on the intensity of the gamma rays.

6. Liquid production profile calculation

The surface release rate of the marker is mainly related to the flow rate and the accumulated release time on the premise that the flow channel structure of the release device is fixed, the downhole environment (temperature, pressure and casing size) is consistent, and the oil and water components are unchanged. The inventors have verified this understanding by ground simulation means and can be expressed as a second order mathematical approximation as follows:

f(q,t)＝a₀+a₁·q²+a₂·q·t+a₃·t²+a₄·q+a₅·t (2);

In the formula (2): f is the content of the marker in the unit volume of the production fluid (g/L), and enough data samples can be obtained through periodic sampling and measurement; t is the working time (t is the time from the start of label release to the time of sampling); q is the flow rate (in square/day) of the liquid being marked; a ₀、a₁、a₂、a₃、a₄、a₅ is a coefficient of each item.

Finally, the flow q value is given by a set of at least 10 f-value data samples, fitting calculation. The flow values of the oil and the water at each position can be obtained through calculation, and then the total flow and the oil-water ratio of the section at each position can be calculated.

Example 1

The general flow of the horizontal well production profile test is as follows.

1) The layout scheme of the underground release device is designed: determining which intervals under the well are concerned according to the well conditions, and counting the number of the intervals and the specific positions of the front end and the rear end of each interval (the position close to the well bottom is the front end and the position far from the well bottom is the rear end). A release device is to be arranged at the rear end of each concerned layer section, and the quantity of concerned layer sections is the quantity of release devices to be arranged. As shown in fig. 2, for example, 5 intervals are required, and 5 release devices are required to be placed at the rear end of each interval.

2) Factory production: according to the above, the liquid production condition of 5 intervals is needed to be measured, firstly, 5 solid oil-based markers and 5 solid water-based markers are formed, then, the solid oil-based markers and the solid water-based markers are arranged in a release cavity of a release device in a matching way, namely, one oil-based marker and one water-based marker are arranged in each release device, 5 complete release devices are assembled together, and A, B, C, D, E complete release devices are marked respectively.

3) Uphole preparation: 1, carrying out necessary well flushing and well dredging operation before the releasing device is in the well, so as to ensure that the releasing device can smoothly pass through when the releasing device is in the well next; 2, a manual sampling valve and a sampling port are arranged on the wellhead production tree, so that the on-site liquid sample collection is convenient to implement after the production logging begins; 3, other preparation works are the same as the conventional well operation.

4) And (3) well setting: and 5 release devices are connected with the oil pipe one by one, and the release devices are sequentially lowered from A to E to reach the designated position. And after the last release device E, an oil inlet nipple is installed. And after the oil inlet nipple, installing equipment according to conventional well descending operation between wellhead christmas trees. As shown in fig. 2, the tubing is disposed within the casing.

5) And (3) production: and (5) producing liquid according to conventional operation, and keeping the flow stable.

6) Sampling: sampling at fixed time intervals, wherein 100ml of the sample is sampled each time; over 10 cycles, 10 samples were taken, giving 10 samples.

7) Sample preparation: in order to reduce interference of irrelevant elements on a marking signal in later measurement, a chemical method is adopted to separate main irrelevant elements Na and K in each liquid sample, and then the liquid sample from which the Na and K elements are removed is prepared into a solid sample.

8) Neutron activation: the solid samples are placed in a thermal neutron field one by one for irradiation, and the marking elements are activated into radioactive isotopes through irradiation.

9) Gamma measurement: and (3) placing the activated sample into a lead shielding chamber, and carrying out gamma ray measurement and spectrum decomposition by using a high-purity germanium detector and a multichannel spectrometer. And calculating the content of each marking element in the sample by utilizing neutron activation analysis technology according to the measured gamma count of each marking element in unit time.

10 Data normalization processing: and normalizing the content of each marker element in each standard obtained by neutron activation analysis to obtain the normalized value of each marker element in the sample. Each marker element yields 1 set of 10 normalized values.

11 Profile calculation: substituting normalized values of the oil-based marking element and the water-based marking element of the same release device into a formula (2), and respectively calculating respective flow rates of the oil and the water of the interval by fitting to obtain the oil-water ratio. And calculating other intervals according to the same method, and finally obtaining the production profile of all the concerned intervals.

Example 2 high water level oil well Water test

For high water wells, if there is also a small amount of production, not only the dominant water production interval is found, but also the production interval is needed. In the traditional water finding test method, the main force water outlet interval is mainly focused, but in reality, if the main force water outlet interval is accompanied by a small amount of oil production, the main force water outlet interval is plugged according to a test conclusion, and the result is that water is blocked and a small amount of oil is blocked. Therefore, if the main water outlet interval can be given, the main oil producing position of the well can be given, and more comprehensive basic data can be provided for subsequent comprehensive treatment.

As shown in fig. 2, for a high water horizontal well with 5 intervals, 5 release devices are planned to be deployed, wherein the release device a focuses on the production situation of the bottom hole part, and the water-based marker a _W and the oil-based marker a _O are arranged in the device; the release device B pays attention to the liquid production condition between the A and the B, and the water-based marker B _W and the oil-based marker B _O are arranged in the release device B; the release device C pays attention to the liquid production condition between the B and the C, and the water-based marker C _W and the oil-based marker C _O are arranged in the release device; the release device D pays attention to the liquid production condition between C and D, and the water-based marker D _W and the oil-based marker D _O are arranged in the release device D; the release device E is concerned with the fluid production between D and E, and is filled with a water-based marker E _W and an oil-based marker E _O.

An oil inlet nipple is arranged behind the last release device E. And installing conventional underground production equipment between the oil inlet nipple and the wellhead production tree.

The data is normalized by down-hole, production, sampling, neutron activation analysis, to obtain an oil-based marker data signal set (Ao, bo, co, do, eo) and a water-based marker signal set (Aw, bw, cw, dw, ew). The water finding test is mainly to judge the water outlet layer section of the main force, so the water outlet layer section of the main force can be determined through the abrupt change of signals. First, the signal differences between adjacent markers were determined, Δ ABo =bo-Ao, Δ BCo =co-Bo, Δcdo=do-Co, Δdeo=eo-Do, Δ ABw =bw-Aw, Δ BCw =cw-Bw, Δcdw=dw-Cw, and Δ DEw =ew-Dw.

If the dominant water outlet interval occurs at the bottom hole site, the signal will appear: aw is much greater than Δ ABw and the four signal values Δ ABw, Δ BCw, ΔCDw, Δ DEw are not much different. If a dominant water outlet interval were to occur between the AB delivery devices, the signal would appear: Δ ABw is much larger than Aw, and the four signal values Aw, Δ BCw, Δcdw, Δ DEw are not much different. The same method can determine whether a dominant water outlet interval exists between BC, CD, or DE.

The data signals (Ao, Δ ABo, Δ BCo, Δcdo, Δdeo) are used to determine the main pay zone, and the method is the same as the determination of the main pay zone.

Example 3 horizontal well full lifecycle production monitoring

For a horizontal oil well, the technology of the application can be used for implementing production monitoring of the whole life cycle, namely monitoring the liquid production condition of each layer section of the horizontal well, including the flow rate and the oil-water ratio of each layer section and the change trend of the production layer along with the production. The information is mastered at any time, and complete basic data is provided for scientific decisions of production management and maintenance schemes of the horizontal well.

As shown in fig. 2, a horizontal well which has just been completed or a horizontal well which has been produced for many years has 5 intervals, the production of each interval needs to be monitored for a long period of time, a release device is arranged at the rear end of each interval (the layer is far away from the bottom end of the well and is the rear end of the interval), and the total horizontal interval is provided with A, B, C, D, E release devices. After the last release device E, an oil inlet nipple is installed. And installing conventional underground production equipment between the oil inlet nipple and the wellhead production tree. Wherein, the release device A pays attention to the liquid production condition of the well bottom part, and the water-based marker A _W and the oil-based marker A _O are arranged in the device; the release device B pays attention to the liquid production condition between the A and the B, and the water-based marker B _W and the oil-based marker B _O are arranged in the release device B; the release device C pays attention to the liquid production condition between the B and the C, and the water-based marker C _W and the oil-based marker C _O are arranged in the release device; the release device D pays attention to the liquid production condition between C and D, and the water-based marker D _W and the oil-based marker D _O are arranged in the release device D; the release device E is concerned with the fluid production between D and E, and is filled with a water-based marker E _W and an oil-based marker E _O.

And (5) completing the well-descending operation, adjusting the well production state, and starting the oil extraction production operation. Because of full life cycle monitoring, the normal sampling time can be sampled monthly or quarterly according to the operation habit; the liquid samples from each sampling were subjected to sample preparation, neutron activation analysis, and normalized to yield 5 oil-based marker signals Ao, bo, co, do, eo, and 5 water-based marker signals Aw, bw, cw, dw, ew. And (3) the 10 data are placed in the same rectangular coordinate system together with the historical data by taking time as the abscissa, and a trend graph is drawn.

The development condition of the downhole production state change of the well can be observed through the trend chart, and the development condition comprises the relative change of the oil-water ratio of the same interval and the relative change of the liquid production amount between different intervals. In general, the trend of the marking signal is almost unchanged or shows a slow gradual change of a large time scale, so when an oil-based marking signal of a certain interval appears or the signal value of the water-based marking signal deviates from the trend, for example, the increase amplitude of the water-based marking signal Cw is larger, and Dw and Ew are also obviously increased, while Aw and Bw are not obviously changed, which indicates that the water yield of BC is obviously increased.

Aiming at the full life cycle monitoring of a horizontal well, if abnormal conditions such as operation system change, obvious water content change and the like occur between two sampling intervals, the underground production state needs to be known in time, or the next change process is observed and tracked, dense sampling can be adopted, namely, the sampling interval is shortened, the sampling interval can be determined according to the development process of an event and the requirement of data analysis, and the minimum sampling interval is 1 minute. Thus, the change process of the downhole state is restored from the change of the series of continuous data by densely sampling in a short time.

Specific examples are as follows.

1) Well condition assumptions

The well production rate is 1000t/day at maximum and works continuously for 5 years.

2) Element selection and release requirements

The detection limit of neutron activation analysis elements can reach 10 ^-14 g, the content of the marking elements in the oil-water liquid is 10 ^-12 g/ml, the marking elements can be obtained by measuring the original liquid sample of the stratum, and the marking elements with the background content meeting the requirement are selected. In order to be able to efficiently label the liquid production situation, the amount of label element released needs to be one order of magnitude above background, i.e. 10 ^-11 g/ml, in order to make a more conservative calculation, the maximum release is required to be calculated as 10 ^-10 g/ml.

3) Calculation of

In order to be able to effectively mark and measure, the minimum charge of the single marking element of this well is: 1000t/day 365day/a 5a 1000000ml/t 10 ^-10 g/ml = 1825g.

In order for the release to be relatively stable over the 5 years, i.e. the released amount has as little effect as possible on the release law of the remaining marking elements, it is required that the maximum released amount over the 5 years only accounts for 40% of the total charge amount, the initial total charge amount is: 1825 g/40% = 4562g.

By assuming and conservatively calculating, for a high-production well requiring full life cycle monitoring, an initial charge of 5Kg of each marker element is required, and production monitoring for at least 5 years can be achieved, which is not possible with the prior art.

The invention is not limited to the specific embodiments described above. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification, as well as to any novel one, or any novel combination, of the steps of the method or process disclosed.

Claims

1. The method for selecting the marker for the oilfield logging is characterized by comprising the following steps of:

S=θ•σ•β•γ/M （1），

in the formula (1), theta is the abundance of elements, sigma is the neutron action section, beta is the decay branch ratio, gamma is the absolute intensity of rays, and M is the atomic weight;

2. The method for selecting the marker for oilfield logging according to claim 1, wherein the selected marker element is used for manufacturing a water-based marker and an oil-based marker, and the content of the corresponding element can be determined by measuring the intensity of the characteristic gamma signal of the corresponding element after neutron activation.

3. The method of selecting a marker for oilfield logging of claim 2, wherein the water-based marker is an oxalic acid compound and the oil-based marker is a stearic acid compound.

4. A method of selecting a marker for oilfield logging as defined in claim 3, wherein the water-based marker is produced by the following steps: oxalic acid compounds used for water-based marking elements are selected, and are formed under high temperature and high pressure conditions, wherein the forming temperature is controlled to be 20 ℃ below the melting point temperature of the corresponding oxalic acid compounds to be 8-20 mpa;

The oil-based markers were made as follows: and (3) selecting a stearic acid compound for the oil-based marking element, and forming under high temperature and high pressure conditions, wherein the forming temperature is controlled to be 20 ℃ below the melting point temperature of the corresponding stearic acid compound to be 8-20 MPa.

5. The method for selecting markers for oilfield logging according to any one of claims 1 to 4, wherein in the step b, N elements with the largest S factors are selected, and gamma-ray interference rejection is performed among the selected elements, i.e., only elements with large S factors are reserved for the elements with gamma-ray interference; the remaining elements are marker elements.

6. The method for selecting a marker for oilfield logging of claim 5, wherein the number of N is 10-40.

7. The method according to any one of claims 1 to 4, wherein in the step b, the selected series of marking elements includes ：¹⁵¹Eu、¹⁹¹Ir、¹⁰⁹Ag、¹³³Cs、¹¹⁵In、¹⁵²Sm、⁵⁹Co、¹⁸⁷Re、¹³⁹La、¹⁵⁹Tb、¹⁷⁶Lu、¹⁸¹Ta、⁴⁵Sc、⁵⁵Mn、¹⁸⁰Hf、¹⁸⁶W、¹⁶⁹Tm、¹⁶⁴Dy、¹⁰³Rh、¹²¹Sb.

8. The method according to claim 5, wherein in the step b, the selected series of marking elements includes ：¹⁵¹Eu、¹⁹¹Ir、¹⁰⁹Ag、¹³³Cs、¹¹⁵In、¹⁵²Sm、⁵⁹Co、¹⁸⁷Re、¹³⁹La、¹⁵⁹Tb、¹⁷⁶Lu、¹⁸¹Ta、⁴⁵Sc、⁵⁵Mn、¹⁸⁰Hf、¹⁸⁶W、¹⁶⁹Tm、¹⁶⁴Dy、¹⁰³Rh、¹²¹Sb.

9. The method according to claim 6, wherein in the step b, the selected series of marking elements includes ：¹⁵¹Eu、¹⁹¹Ir、¹⁰⁹Ag、¹³³Cs、¹¹⁵In、¹⁵²Sm、⁵⁹Co、¹⁸⁷Re、¹³⁹La、¹⁵⁹Tb、¹⁷⁶Lu、¹⁸¹Ta、⁴⁵Sc、⁵⁵Mn、¹⁸⁰Hf、¹⁸⁶W、¹⁶⁹Tm、¹⁶⁴Dy、¹⁰³Rh、¹²¹Sb.