A method for testing shale organic carbon content and oil content based on nuclear magnetic resonance

Abstract

The application discloses a kind of shale organic carbon content and oil content test method based on nuclear magnetic resonance, belong to petroleum exploration technical field, it is characterized in that, including the following steps: a, hydrogen-containing substance in shale standard sample is excited by SMC pulse sequence, and the feedback nuclear magnetic resonance signal is obtained;B, the calculation model of shale kerogen and oil content standard sample is constructed;C, the nuclear magnetic signal amount and relaxation parameter of content material in the shale sample to be measured;D, according to nuclear magnetic signal, the organic carbon content and oil content in the shale sample to be measured are calculated.The application can conveniently and effectively test the organic carbon content and oil content in shale sample simultaneously, the test process is simple, time-consuming is short, and the model built selects real reservoir mineral and crude oil, has good applicability and authenticity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil exploration, and particularly relates to a shale organic carbon content and oil content testing method based on nuclear magnetic resonance. BACKGROUND

[0002] As a technology that can directly detect the state of hydrogen protons, nuclear magnetic resonance has been widely applied in the fields of biology, chemistry, agriculture and conventional reservoir evaluation of oil and energy, such as obtaining rock porosity by combining saturation with nuclear magnetic resonance, and obtaining oil content in conventional sandstone samples by combining manganese immersion method with nuclear magnetic resonance.

[0003] For shale oil reservoirs, the content of the substances therein is relatively complex, including not only liquid oil, gas and water, but also solid organic carbon components such as kerogen. These problems affect the accuracy of the conventional nuclear magnetic resonance method for testing and interpretation.

[0004] The existing shale hydrogen-containing fluid evaluation mainly obtains the liquid oil content therein by extraction, and obtains the solid organic carbon content therein by high-temperature combustion. These two methods not only destroy the shale sample, but also take a long time and pollute the environment with the solvent used for extraction.

[0005] Chinese patent document with publication number CN111912958A and publication date November 10, 2020 discloses a method for detecting the adsorbed oil content in oil hosted by inorganic minerals in shale, which is characterized by comprising the following steps: obtaining a shale sample and shale oil compound components, and loading the shale oil compound components into kaolinite pores to obtain a kaolinite pore-shale oil model; performing molecular dynamics simulation on the kaolinite pore-shale oil model to obtain a shale oil density curve in the kaolinite pores; determining the adsorbed oil capacity per unit area of the kaolinite surface according to the shale oil density curve in the kaolinite pores and the surface area of the kaolinite pore-shale oil model; determining the specific surface area of inorganic minerals in the shale sample according to the number of inorganic pores in the shale sample and the surface area of the inorganic pores in the shale sample; and determining the adsorbed oil content in the oil hosted by inorganic minerals in the shale as the product of the adsorbed oil capacity per unit area of the kaolinite surface and the specific surface area of inorganic minerals in the shale sample.

[0006] The method for detecting the adsorbed oil content in oil hosted by inorganic minerals in shale disclosed in the patent document can improve the accuracy of the detection results of adsorbed and free oil content. However, the model uses a single type of clay mineral for simulation, which is inconsistent with the characteristics of the real reservoir rock, that is, the diversity of mineral types and the diversity of pore structure types, and cannot truly reflect the pore structure characteristics and the adsorbed oil content in the pores of the reservoir. The process is complex, time-consuming and has poor applicability. SUMMARY

[0007] The present application can conveniently and effectively test the organic carbon content and oil content in shale samples at the same time, the test process is simple, time-consuming is short, and the built model selects real reservoir minerals and crude oil, and has good applicability and authenticity.

[0008] The present application is realized by the following technical solutions:

[0009] A shale organic carbon content and oil content test method based on nuclear magnetic resonance, characterized in that it comprises the following steps:

[0010] a. Excite hydrogen-containing substances in shale samples by SMC pulse sequence to obtain feedback nuclear magnetic resonance signals;

[0011] b. Construct a calculation model of shale kerogen and oil content samples;

[0012] c. Nuclear magnetic signal amount and relaxation parameters of content substances in the shale sample to be tested;

[0013] d. Calculate the organic carbon content and oil content in the shale sample to be tested according to the nuclear magnetic signals.

[0014] In the step a, the obtained feedback nuclear magnetic resonance signals refer to the nuclear magnetic resonance spectra of the corresponding kerogen samples and oil samples of the shale samples, and specifically include screening different types of kerogen samples and constructing a recognition model based on nuclear magnetic resonance.

[0015] It also includes obtaining corresponding sample components in the shale sample calibration process, and establishing a quantitative model of simulating kerogen and oil in shale.

[0016] The sample components are obtained by processing the components in the shale sample, specifically by crushing shale and identifying different types of kerogen through microscopic components, and by obtaining shale oil samples from nearby wells and obtaining a quantitative model of shale oil through nuclear magnetic resonance.

[0017] The screening of different types of kerogen samples and the construction of the recognition model based on nuclear magnetic resonance refer to determining the type through principal component analysis before quantitative calculation of the kerogen samples, and selecting the transverse relaxation peak average time T 2g , the longitudinal relaxation peak average time T 1g , the relaxation peak ratio T 1g / T 2g , and the hydrogen nuclear signal intensity of unit mass kerogen.

[0018] The step c is specifically to perform nuclear magnetic resonance spectrum on the shale sample to be measured, to obtain the signal amount of hydrogen-containing substances, the transverse relaxation distribution and the longitudinal relaxation distribution related distribution map (T1, T2) by processing the nuclear magnetic resonance signal through two-dimensional inverse lasso change, and to identify the kerogen and shale oil through the map and respectively bring into a calculation model.

[0019] The pre-treatment before the hydrogen-containing substances in the shale sample are excited by the SMC pulse sequence is low-temperature drying treatment of the shale sample.

[0020] The temperature of the low-temperature drying treatment is 55-60 DEG C.

[0021] The time of the low-temperature drying treatment is 6-8 h.

[0022] In the step a, the shale sample is simulated by using the kerogen extracted from the shale by mixing clay minerals and quartz sand as a skeleton mineral, and then quantitatively injecting shale oil.

[0023] The beneficial effects of the present application mainly include the following aspects:

[0024] 1. In the present application, a, the hydrogen-containing substances in the shale sample are excited by the SMC pulse sequence, and the feedback nuclear magnetic resonance signal is obtained; b, the calculation model of the shale kerogen and oil content sample is constructed; c, the nuclear magnetic signal amount and relaxation parameters of the content substances in the shale sample to be measured; d, the organic carbon content and oil content in the shale sample to be measured are calculated according to the nuclear magnetic signal, compared with the prior art, the organic carbon content and oil content in the shale sample can be conveniently and effectively tested at the same time, the test process is simple, the time is short, and the model selected has good applicability and authenticity.

[0025] 2. In the present application, the hydrogen-containing substances in the shale sample are excited by the SMC pulse sequence, which can better make up for the loss of signal collection of solid substances caused by the echo time of the pure echo sequence, and ensure the reliability of signal collection.

[0026] 3. In the present application, the hydrogen-containing substances in the shale sample are excited by the SMC pulse sequence, which can discard the interference of free water in the shale sample, reduce the loss of retained shale oil signal, and improve the test accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0027] The present application will be further specifically described below in combination with the drawings and specific embodiments of the present application:

[0028] Fig. 1 The flow chart of the present application;

[0029] Fig. 2To simulate the relationship between the organic carbon content of shale samples and the organic carbon signal amount of nuclear magnetic test;

[0030] Fig. 3 To simulate the relationship between the oil content of shale samples and the oil signal amount of nuclear magnetic test. DETAILED DESCRIPTION

[0031] Embodiment 1

[0032] Reference Figs. 1-3 A shale organic carbon content and oil content test method based on nuclear magnetic resonance, comprising the following steps:

[0033] a. Excite hydrogen-containing substances in shale samples by SMC pulse sequence to obtain feedback nuclear magnetic resonance signals;

[0034] b. Construct a calculation model of shale kerogen and oil content samples;

[0035] c. Nuclear magnetic signal amount and relaxation parameters of content substances in the shale samples to be tested;

[0036] d. Calculate the organic carbon content and oil content in the shale samples to be tested according to the nuclear magnetic signals.

[0037] This embodiment is the most basic implementation. a. Excite hydrogen-containing substances in shale samples by SMC pulse sequence to obtain feedback nuclear magnetic resonance signals; b. Construct a calculation model of shale kerogen and oil content samples; c. Nuclear magnetic signal amount and relaxation parameters of content substances in the shale samples to be tested; d. Calculate the organic carbon content and oil content in the shale samples to be tested according to the nuclear magnetic signals. Compared with the prior art, the organic carbon content and oil content in shale samples can be tested simultaneously conveniently and effectively, the test process is simple, the time consumption is short, and the model constructed selects real reservoir minerals and crude oil, and has good applicability and authenticity.

[0038] Embodiment 2

[0039] Reference Figs. 1-3 A shale organic carbon content and oil content test method based on nuclear magnetic resonance, comprising the following steps:

[0040] a. Excite hydrogen-containing substances in shale samples by SMC pulse sequence to obtain feedback nuclear magnetic resonance signals;

[0041] b. Construct a calculation model of shale kerogen and oil content samples;

[0042] c. Nuclear magnetic signal amount and relaxation parameters of content substances in the shale samples to be tested;

[0043] d. Calculate the organic carbon content and oil content in the shale samples to be tested according to the nuclear magnetic signals.

[0044] In step a, the obtained feedback nuclear magnetic resonance signal refers to obtaining the nuclear magnetic resonance spectrum of the shale standard sample corresponding to the kerogen sample and oil sample, specifically including screening different types of kerogen samples and constructing a recognition model based on nuclear magnetic resonance.

[0045] It also includes obtaining the corresponding sample components in the shale standard sample calibration process, and establishing a quantitative model of simulating kerogen and oil in shale.

[0046] The sample components are obtained by processing shale samples to obtain components in shale, specifically by crushing shale and identifying different types of kerogen through microscopic components, and by obtaining shale oil samples from nearby wells and obtaining a quantitative model of shale oil through nuclear magnetic resonance.

[0047] Further, the screening of different types of kerogen samples and the construction of a recognition model based on nuclear magnetic resonance refers to determining the type through principal component analysis before quantitative calculation of the kerogen sample, and selecting the transverse relaxation peak average time T 2g , the longitudinal relaxation peak average time T 1g , the relaxation peak ratio T 1g / T 2g , and the hydrogen nuclear signal intensity per unit mass of kerogen, and selecting different masses of the three types of kerogen to establish a quantitative model of different types of kerogen through nuclear magnetic resonance.

[0048] Further, step c specifically refers to performing nuclear magnetic resonance spectrum on the shale standard sample to be tested, processing the nuclear magnetic resonance signal through two-dimensional inverse Laplace transformation to obtain a signal amount of hydrogen-containing substances and a transverse relaxation distribution and longitudinal relaxation distribution correlation distribution spectrum (T1, T2), and identifying kerogen and shale oil through the spectrum and respectively inputting into the calculation model.

[0049] The pre-treatment before exciting the hydrogen-containing substances in the shale standard sample through the SMC pulse sequence refers to low-temperature drying treatment of the shale standard sample.

[0050] The temperature of the low-temperature drying treatment is 55°C.

[0051] The time of the low-temperature drying treatment is 6h.

[0052] This embodiment is a preferred implementation, which can better compensate for the loss of signal acquisition of solid substances affected by the echo time of pure echo sequence, and ensure the reliability of signal acquisition.

[0053] Example 3

[0054] Referring to Figs. 1-3 A shale organic carbon content and oil content testing method based on nuclear magnetic resonance, comprising the following steps:

[0055] a. Exciting hydrogen-containing substances in shale samples by SMC pulse sequence to obtain feedback nuclear magnetic resonance signals;

[0056] b. Constructing a calculation model of shale kerogen and oil content samples;

[0057] c. Nuclear magnetic signals and relaxation parameters of hydrogen-containing substances in the shale samples to be measured;

[0058] d. Calculating the organic carbon content and oil content in the shale samples to be measured according to the nuclear magnetic signals.

[0059] In step a, the nuclear magnetic resonance signals obtained are the nuclear magnetic resonance spectra of the corresponding kerogen samples and oil samples of the shale samples, specifically including screening different types of kerogen samples and constructing a recognition model based on nuclear magnetic resonance.

[0060] It also includes obtaining sample components corresponding to the shale sample calibration process, and establishing a quantitative model of kerogen and oil in shale.

[0061] The sample components are obtained by processing the shale samples to obtain the components in the shale, specifically by crushing the shale and identifying the different types of kerogen through microscopic components, and by obtaining shale oil samples from nearby wells and obtaining a quantitative model of shale oil through nuclear magnetic resonance.

[0062] The screening of different types of kerogen samples and the construction of a recognition model based on nuclear magnetic resonance refer to determining the type through principal component analysis before quantitative calculation of the kerogen samples, and selecting the transverse relaxation peak average time T 2g , the longitudinal relaxation peak average time T 1g , the relaxation peak ratio T 1g / T 2g , and the hydrogen nuclear signal intensity per unit mass of kerogen.

[0063] Step c specifically refers to performing nuclear magnetic resonance spectroscopy on the shale samples to be measured, processing the nuclear magnetic resonance signals through two-dimensional inverse Laplace transformation to obtain signal quantity and transverse relaxation distribution and longitudinal relaxation distribution correlation distribution maps (T1, T2), identifying kerogen and shale oil through the maps, and respectively inputting into the calculation model.

[0064] The hydrogen-containing substances in the shale samples are excited by the SMC pulse sequence before pretreatment.

[0065] The temperature of the low-temperature drying treatment is 60°C.

[0066] The low-temperature drying treatment time is 8h.

[0067] In step a, the shale standard sample is prepared by using clay minerals and quartz sand mixed with kerogen extracted from shale as a skeleton mineral, and then quantitatively injecting shale oil.

[0068] The present embodiment is the best mode, which pre-treats hydrogen-containing substances in the shale standard sample by SMC pulse sequence, and the pre-treatment refers to low-temperature drying treatment of the shale standard sample, which can eliminate the interference of free water in the shale standard sample, reduce the loss of retained shale oil signals, and improve the test accuracy.

[0069] The present application is described below by using specific examples:

[0070] 10 kg of organic-rich shale samples with TOC greater than 1.0% in different sedimentary environments in the research block are selected, the samples are crushed to 1.0-0.5 mm, and the shale samples are separated by kerogen according to the SY / T 5123 standard requirements to obtain kerogen standard samples.

[0071] The extracted kerogen is identified by maceral, and the types of organic matter in each sample are determined, and type I, type II and type III kerogen samples are selected as sample 1, sample 2 and sample 3 respectively;

[0072] Three portions of sample 1, sample 2 and sample 3 are selected, each portion is 3g, and nuclear magnetic experiment test is carried out respectively to obtain the nuclear magnetic resonance spectrum characteristics of kerogen with different types of organic matter, and the recognition method of nuclear magnetic resonance spectrum and kerogen type is established by the principal component analysis method of SPSS software, and each type of kerogen is established.

[0073] The principal component factors of the principal component analysis method described above are T 2g , T 1g , T 2g / T 1g , and Amp.

[0074] T 2g : T2 geometric mean value;

[0075]

[0076] Wherein: T 2i is the i-th T2 distribution on the T2 spectrum, A i is the signal amplitude corresponding to the i-th T2 distribution on the T2 spectrum.

[0077] T 1g : T1 geometric mean value;

[0078]

[0079] Wherein: T li is the i-th T1 distribution on the T1 spectrum, A i is the signal amplitude corresponding to the i-th T1 distribution on the T1 spectrum;

[0080] Amp: is the signal amount of per unit mass of kerogen;

[0081] 0.5g, 1.0g, 2.0g, 3.0g and 5.0g of sample 1 are respectively mixed with 49.5g, 49.0g, 48.0g, 47.0g and 45.0g of dry clay minerals and dry quartz sand, and are put into a 2.5cm cylindrical mold for compaction to obtain cylindrical samples sample 1-1, sample 1-2, sample 1-3, sample 1-4 and sample 1-5 with a diameter of 2.5cm and a height of 5cm, and the organic carbon content is 1.0%, 2.0%, 4.0%, 6.0% and 10.0% respectively;

[0082] The mass of sample 1-1, sample 1-2, sample 1-3, sample 1-4 and sample 1-5 is weighed to obtain m1-1, m1-2, m1-2, m1-3, m1-4 and m1-5, unit g;

[0083] The density of the crude oil produced by the adjacent well is tested to obtain p1, unit g / cm 3 ;

[0084] The volume of crude oil required to reach 5mg / g, 10mg / g, 15mg / g, 20mg / g and 30mg / g oil content samples is calculated according to the mass of sample 1-1, sample 1-2, sample 1-3, sample 1-4 and sample 1-5 and the density of the crude oil, V1-1, V1-2, V1-3, V1-4 and V1-5, unit μL;

[0085] The corresponding volume of crude oil is taken with a micro-sampler and injected into sample 1-1, sample 1-2, sample 1-3, sample 1-4 and sample 1-5 respectively;

[0086] The sample 1-1, sample 1-2, sample 1-3, sample 1-4 and sample 1-5 are subjected to SMC nuclear magnetic resonance experiment.

[0087] According to the range of kerogen and hydrocarbon signal samples, the two-dimensional nuclear magnetic signal of sample 1-1, sample 1-2, sample 1-3, sample 1-4 and sample 1-5 is segmented;

[0088] According to the signal strength of the kerogen region of sample 1-1, sample 1-2, sample 1-3, sample 1-4 and sample 1-5 and the organic carbon content, a correlation formula is established.

[0089] AK1=AM1 / K1;

[0090] AK1=AM1 / K1; wherein, AK1 is the content of type I kerogen in unit mass sample, AM1 is the signal of type I kerogen in unit mass sample tested by nuclear magnetic resonance, and K1 is the coefficient of type I kerogen calibration;

[0091] The formula is established as follows:

[0092] AK2=AM2 / K2;

[0093] AK2=AM2 / K2; wherein, AK2 is the content of type II kerogen in unit mass sample, AM2 is the signal of type II kerogen in unit mass sample tested by nuclear magnetic resonance, and K3 is the coefficient of type II kerogen calibration;

[0094] AK3=AM3 / K3;

[0095] AK3=AM3 / K3; wherein, AK3 is the content of type III kerogen in unit mass sample, AM3 is the signal of type III kerogen in unit mass sample tested by nuclear magnetic resonance, and K3 is the coefficient of type III kerogen calibration;

[0096] The correlation formula is established according to the signal strength of the hydrocarbon region of the three series of samples and the oil content;

[0097] AO=AM4 / K4;

[0098] AO=AM4 / K4; wherein, AO is the shale oil content in unit mass sample, AM4 is the signal of shale oil in unit mass sample tested by nuclear magnetic resonance, and K4 is the coefficient of shale oil calibration;

[0099] The two-dimensional nuclear magnetic signals of other mud shale plug samples are tested, and the organic matter types of the samples are obtained by comparison with different two-dimensional nuclear magnetic chart boards.

[0100] According to the organic matter type of the sample, the corresponding formula is selected, and the organic carbon content is calculated according to the signal strength.

[0101] The oil content is calculated according to the signal strength of the hydrocarbon of the sample.

[0102] The SMC sequence in the application refers to:

[0103] The S section is a saturation band pulse, and the nuclear magnetic resonance signal is saturated on the Z axis by a series of 90 DEG C radio frequency pulses in the X+ direction, so that the magnetic vector in the Z direction is 0;

[0104] The M section is a dipole coupling effect, and the effective excitation and collection of the kerogen signal are realized by pulse arrangement;

[0105] The C section sequence is a CPMG sequence, which mainly collects the measurement of the T2 relaxation of the shale oil component in the shale sample;

[0106] The purpose of the recovery time is to realize the test of the T1 relaxation of each hydrogen-containing component by setting different recovery times.

Claims

1. A method for testing the kerogen content and oil content of shale mudstone based on nuclear magnetic resonance, characterized in that, Includes the following steps: a. Obtain feedback nuclear magnetic resonance signals by exciting hydrogen-containing substances in shale standards using SMC pulse sequences; b. Construct a calculation model for shale kerogen and oil content standard samples; c. Obtain the nuclear magnetic resonance signal and relaxation parameters of the substances contained in the shale sample to be tested; d. Calculate the kerogen content and oil content in the shale sample to be tested based on the nuclear magnetic resonance signal; In step a, obtaining the feedback nuclear magnetic resonance signal refers to acquiring the nuclear magnetic resonance spectra of the kerogen sample and oil sample corresponding to the shale standard sample, specifically including screening different types of kerogen samples and constructing a nuclear magnetic resonance-based identification model. The process of screening different types of kerogen samples and constructing a nuclear magnetic resonance-based identification model refers to determining the type of kerogen sample through principal component analysis before quantitative calculation. The principal component factor is the average time T of the transverse relaxation peak. 2g Longitudinal relaxation peak mean time T 1g relaxation peak ratio T 1g / T 2g By analyzing the hydrogen nucleus signal intensity per unit mass of kerogen, and selecting different masses of three types of kerogen, quantitative models of different types of kerogen were established using nuclear magnetic resonance. The SMC pulse sequence refers to: The S-segment consists of saturated band pulses, which use a series of 90-degree radio frequency pulses in the X+ direction to achieve a saturation magnetic vector of 0 in the Z-axis direction of the nuclear magnetic resonance signal; the M-segment consists of dipole coupling, which uses pulse adjustment to effectively excite and acquire kerogen signals; the C-segment sequence is a CPMG sequence, which mainly acquires the T2 relaxation of shale oil components in shale samples; and the T1 relaxation of each hydrogen-containing component is tested by setting different recovery times. Step c specifically refers to performing nuclear magnetic resonance on the shale sample to be tested, processing the nuclear magnetic resonance signal through two-dimensional inverse Labras transformation, obtaining the correlation distribution spectrum of the signal quantity of hydrogen-containing substances with the transverse relaxation distribution and the longitudinal relaxation distribution, identifying kerogen and shale oil through the spectrum, and inputting them into the calculation model respectively.

2. The method for testing kerogen content and oil content in shale mudstone based on nuclear magnetic resonance according to claim 1, characterized in that: It also includes obtaining the sample components corresponding to the calibration process of shale standard samples and establishing a quantitative model to simulate kerogen and oil in shale.

3. The method for testing kerogen content and oil content in shale mudstone based on nuclear magnetic resonance according to claim 2, characterized in that: The sample components were obtained by processing shale standard samples to separate the components in the shale. Specifically, different types of kerogen were obtained by crushing shale and identifying microscopic components. Shale oil samples were obtained from the well site, and a quantitative model of shale oil was obtained by nuclear magnetic resonance.

4. The method for testing kerogen content and oil content in shale mudstone based on nuclear magnetic resonance according to claim 1, characterized in that: The pretreatment of the shale standard sample before stimulating hydrogen-containing substances with SMC pulse sequence refers to the low-temperature drying treatment of the shale standard sample.

5. The method for testing kerogen content and oil content in shale mudstone based on nuclear magnetic resonance according to claim 4, characterized in that: The temperature for the low-temperature drying process is 55-60℃.

6. The method for testing kerogen content and oil content in shale mudstone based on nuclear magnetic resonance according to claim 4, characterized in that: The low-temperature drying process takes 6-8 hours.

7. The method for testing kerogen content and oil content in shale mudstone based on nuclear magnetic resonance according to claim 1, characterized in that: In step a, the shale standard sample is prepared by using kerogen extracted from shale as the framework mineral, which is a mixture of clay minerals and quartz sand, and then quantitatively injecting shale oil to simulate the framework.

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