Shale oil mobility evaluation method based on two-dimensional nuclear magnetic resonance experiment

Abstract

The invention belongs to the technical field of shale oil development and research, and discloses a shale oil mobility evaluation method based on a two-dimensional nuclear magnetic resonance experiment, which comprises the following steps: dividing an oil-containing shale sample harvested by a closed coring well into three parts which are respectively marked as a sample 1, a sample 2 and a sample 3; carrying out a TOC determination experiment on the sample 1 to obtain the TOC content of the sample; carrying out a step-by-step pyrolysis experiment on the sample 2 to obtain the contents of the sample S1-1 and the sample S2-2; calculating to obtain a shale oil mobility evaluation factor which is marked as FMO; carrying out a two-dimensional nuclear magnetic resonance experiment on the sample 3 before and after centrifugation to obtain the movable oil content of the sample before and after centrifugation, calculating to obtain the percentage of two-nuclear magnetic resonance movable oil, and recording the percentage as MO2D-NMR; and shale oil mobility evaluation is realized through analysis of the relationship between MO2D-NMR and FMO. According to the method provided by the invention, nondestructive testing of the sample can be realized in the two-dimensional nuclear magnetic resonance experiment process, the loss of light hydrocarbon can be reduced to the greatest extent, and the mobility evaluation precision of shale oil is effectively improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of shale oil development and research, and discloses a shale oil mobility evaluation method based on two-dimensional nuclear magnetic resonance experiment. BACKGROUND

[0002] China's shale oil is mainly continental, and compared with North American marine shale, continental shale has the characteristics of complex pore structure and strong heterogeneity. In addition, the viscosity of continental shale oil is relatively high, which leads to poor mobility, which is one of the reasons why China's shale oil development has not achieved the expected results.

[0003] Shale oil mobility evaluation has important scientific guiding significance for favorable area optimization and development plan preparation. Geologists have done a lot of work on shale oil mobility evaluation research. Feng Guoqi et al. studied the shale oil mobility of Hetaoyuan Formation in Biyang Sag, and found that the higher the saturated hydrocarbon content, the lower the asphaltene content and the clay mineral content, the better the shale oil mobility(Feng Guoqi, Li Jijun, Liu Jiewen, et al. Shale oil enrichment and mobility in Biyang Sag[J]. Petroleum Geology and Oil and Gas Geology, 2019(6): 11.). Chang Jiaqi et al. studied the shale oil mobility of Fengcheng Formation in Mahu Sag, and found that lithofacies control shale oil mobility, siltstone facies has the best mobility, followed by felsic shale facies, and carbonate rock facies is the worst(Chang Jiaqi, Jiang Zhenxue, Gao Zhiye, et al. Characteristics of oiliness and mobility of different lithofacies shale in Fengcheng Formation of Mahu Sag[J]. Journal of Central South University: Science and Engineering, 2022, 53(9): 14.);

[0004] The invention patent with the authorized publication number CN 109991123 B provides a geochemical evaluation method for shale oil resource mobility, which evaluates shale oil mobility by carrying out TOC and rock pyrolysis experiments on shale samples of oil-producing layers and non-oil-producing layers, and drawing shale oil mobility identification chart; the invention patent with the authorized publication number CN 109164501 B provides a method for evaluating shale oil mobility based on fractal dimension, which evaluates shale oil mobility by establishing the relationship between fractal dimension and shale oil mobility evaluation parameters.

[0005] The common problem of the above shale oil mobility evaluation methods is that shale oil mobility evaluation parameters are all based on rock pyrolysis experiment, and the sample needs to be ground into powder during the pyrolysis experiment, which will inevitably cause a large loss of light hydrocarbon, leading to distortion of the S1 value representing the shale mobile oil content, and the shale oil mobility cannot be accurately evaluated. SUMMARY

[0006] In order to solve the problems existing in the existing technology, improve the accuracy of shale oil mobility evaluation, and scientifically guide the formulation of shale oil development plans, the present invention provides a shale oil mobility evaluation method based on two-dimensional nuclear magnetic resonance experiments to solve the problem of insufficient accuracy of traditional methods.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A shale oil mobility evaluation method based on two-dimensional nuclear magnetic resonance experiments comprises the following steps:

[0009] (1) The oil-bearing shale samples obtained from the sealed coring well were divided into three parts, which were recorded as sample 1, sample 2 and sample 3 respectively;

[0010] (2) Conduct a TOC determination experiment on sample 1 to obtain the TOC content of the sample;

[0011] (3) Carry out step-by-step pyrolysis experiments on sample 2 to obtain sample S 1-1 and content;

[0012] (4) The shale oil mobility evaluation factor is calculated and recorded as F MO ;

[0013] (5) Perform two-dimensional nuclear magnetic resonance experiments on sample 3 before and after centrifugation to obtain the movable oil content of the sample before and after centrifugation, and calculate the two-dimensional nuclear magnetic resonance movable oil percentage, which is recorded as MO 2D-NMR ;

[0014] (6) Through MO 2D-NMR With F MO The relationship between the two is analyzed to realize the evaluation of shale oil mobility.

[0015] Step (1), the closed coring process is carried out in accordance with the industry standard Q / SH 0296-2009 "Geological Design Specifications for Closed Coring Wells in Oilfields";

[0016] Step (2), the TOC determination experimental process is carried out in accordance with the national standard GB / T 19145-2022 "Determination of total organic carbon in sedimentary rocks";

[0017] Step (3), the step-by-step pyrolysis experimental process is carried out in accordance with the national standard GB / T 18602-2012, "Pyrolysis Analysis of Rocks";

[0018] Step (3), S 1-1 is the product obtained from the step-by-step pyrolysis experiment at 200℃, S 1-2 These are the products obtained from the step-by-step pyrolysis experiment at 200°C-350°C.

[0019] Step (4), shale oil mobility evaluation factor F MO =(S1-1 +S 1-2 ) / TOC;

[0020] Step (5), the two-dimensional nuclear magnetic resonance experiment process refers to the industry standard SY / T 6490-2007 'laboratory measurement specification of rock sample nuclear magnetic resonance parameters';

[0021] Step (5), the two nuclear magnetic resonance movable oil percentage MO 2D-NMR =(centrifugal movable oil before centrifugal - centrifugal movable oil after centrifugal) / centrifugal movable oil before centrifugal×100%;

[0022] Compared with the prior art, the beneficial effects of the present application are as follows:

[0023] Compared with the traditional shale oil mobility evaluation method based on rock pyrolysis experiment, the method provided by the present application can realize nondestructive testing of the sample during the two-dimensional nuclear magnetic resonance experiment, can minimize the loss of light hydrocarbon to the greatest extent, and can effectively improve the shale oil mobility evaluation precision. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the T1-T2 graph of the two-dimensional nuclear magnetic resonance experiment of the M8 shale sample before centrifugation;

[0025] Figure 2 is the T1-T2 graph of the two-dimensional nuclear magnetic resonance experiment of the M8 shale sample after centrifugation;

[0026] Figure 3 is the MO 2D-NMR and F MO correlation analysis graph. DETAILED DESCRIPTION

[0027] In order to make the technical means adopted by the present application and the purpose easy to understand, the present application will be further described below in combination with specific embodiments.

[0028] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0029] Example 1

[0030] With reference to Figure 1 and Figure 2 , the present specific embodiment adopts the following technical solution: a shale oil mobility evaluation method based on two-dimensional nuclear magnetic resonance experiment, comprising the following steps:

[0031] (1) divide the oil-bearing shale sample harvested from a sealed coring well into 3 parts, and mark them as sample 1, sample 2 and sample 3 respectively;

[0032] The shale samples in the examples of the present application are taken from the first member of Qingshankou Formation in Changling fault depression in the southern Songliao Basin, and a total of 50 pieces;

[0033] The sealed coring process is carried out in accordance with the industry standard Q / SH 0296-2009 “Oilfield Sealed Coring Well Geological Design Specification”;

[0034] In order to avoid the loss of light hydrocarbons during the process of transporting the sealed coring samples from the field to the laboratory, the samples are stored by freezing with liquid nitrogen.

[0035] (2) TOC determination experiment is carried out on sample 1 to obtain the TOC content of the sample;

[0036] The TOC determination experiment process is carried out in accordance with the national standard GB / T 19145-2022 “Determination of Total Organic Carbon in Sedimentary Rocks”;

[0037] The specific steps of the TOC determination experiment are as follows:

[0038] ① Porcelain crucible pretreatment: heat the porcelain crucible to 1000°C for 2 hours, and then store it in a desiccator after cooling;

[0039] ② Shale sample pretreatment: crush the fresh shale sample to 200 mesh (0.075 mm particle size) with an agate mortar. Weigh 5g of crushed sample into a porcelain crucible, add 2mol / L of dilute hydrochloric acid, and use water bath heating to make the reaction proceed fully, at a temperature of 80°C for 2 hours. After the reaction is completed, wash the crushed sample with distilled water until it is neutral, and then place the porcelain crucible containing the crushed sample in an oven dryer and heat it to dry at a temperature of 80°C for 12 hours.

[0040] ③ Sample testing: the instrument model for the stepwise pyrolysis experiment is CS-230 carbon and sulfur analyzer, and the temperature is 25°C.

[0041] (3) Stepwise pyrolysis experiment is carried out on sample 2 to obtain the contents of S 1-1 , S 1-2 , S 2-1 and S 2-2 ;

[0042] The stepwise pyrolysis experiment process is carried out in accordance with the national standard GB / T 18602-2012 “Rock Pyrolysis Analysis”;

[0043] The fresh shale sample is crushed to 200 mesh (0.075 mm particle size) with an agate mortar;

[0044] The instrument model for the stepwise pyrolysis experiment is Rock-Eval 7 pyrolysis instrument, and the experimental temperature is 25°C;

[0045] S 1-1 is the product of the stepwise pyrolysis experiment at 200°C, S 1-2 is the product of the stepwise pyrolysis experiment at 350°C, and (S 1-1+S 1-2 ) represents the content of movable oil in shale;

[0046] S 2-1 is the product of the step pyrolysis experiment at 450℃, representing the content of adsorbed oil in shale;

[0047] S 2-2 is the product of the step pyrolysis experiment at 600℃, representing the content of kerogen in shale;

[0048] (4) Calculate the shale oil mobility evaluation factor, denoted as F MO ;

[0049] Shale oil mobility evaluation factor F MO = (S 1-1 +S 1-2 ) / TOC

[0050] (5) Two-dimensional nuclear magnetic resonance experiments are carried out on sample 3 before and after centrifugation to obtain the movable oil content of the sample before and after centrifugation, and the two nuclear magnetic resonance movable oil percentage is calculated, denoted as MO 2D-NMR ;

[0051] The two-dimensional nuclear magnetic resonance experiment procedure is carried out according to the industry standard SY / T 6490-2007 "Laboratory Measurement Specification for Rock Sample Nuclear Magnetic Resonance Parameters";

[0052] The two-dimensional nuclear magnetic resonance experiment sample is a cylindrical slug with a length of 3 cm and a diameter of 2.5 cm;

[0053] When the sample is subjected to centrifugal treatment, the number of revolutions is 10000 r / min;

[0054] The experimental instrument model is MesoMR23-060H-I type nuclear magnetic resonance analysis and imaging instrument and centrifuge;

[0055] Different types of fluids in shale pores are at different positions in the two-dimensional nuclear magnetic spectrum, which need to be calibrated according to T1 and T2 values, and the division standard is shown in Table 1:

[0056] Table 1 Division standard of different types of shale pores

[0057] Fluid type [T1] [T2] [T1 / T2] Movable oil ＞1 ＞10 Adsorbed oil >10 0.2-1 Free water [["<10", "t2<1"]] ​ ＞0.2 [1-10, T2 > 1] Structural water ＜10 ＜1 Cheese root ＞10 ＜0.2

[0058] As Figure 1 , Figure 2 shown is the two-dimensional nuclear magnetic spectrum of sample M8 before and after centrifugation, it can be seen that the signals of different types of fluids after centrifugation are changed;

[0059] Two nuclear magnetic resonance movable oil percentage MO 2D-NMR = (movable oil before centrifugation - movable oil after centrifugation) / movable oil before centrifugation x 100%;

[0060] (6) by MO 2D-NMR With F MO Analysis of the relationship, realize shale oil mobility evaluation.

[0061] As Figure 3 MO 2D-NMR With F MO Correlation analysis chart, correlation coefficient R 2 > 0.8, indicating that the two have a good positive correlation, can be used to evaluate shale oil mobility MO 2D-NMR Parameter, prove the effectiveness of the method.

[0062] Although some embodiments of the present application have been described herein, those skilled in the art will understand that changes can be made to the embodiments herein without departing from the spirit of the present application. The above embodiments are only exemplary and should not be used as the limit of the scope of the present application.

Claims

1. A method for shale oil mobility evaluation based on two-dimensional nuclear magnetic resonance experiment, characterized in that, The method comprises the following steps: (1) Divide the oil shale sample harvested from the sealed coring well into three parts, and mark them as sample 1, sample 2 and sample 3 respectively; (2) Perform a TOC determination experiment on the sample 1 to obtain the TOC content of the sample; (3) Step pyrolysis experiment was carried out on sample 2 to obtain sample S 1-1 and S 1-2 content; (4) Calculate the shale oil mobility evaluation factor, denoted as F MO ; (5) Perform 2D NMR experiments on sample 3 before and after centrifugation to obtain the mobile oil content of the sample before and after centrifugation, and calculate the 2D NMR mobile oil percentage, denoted as MO 2D-NMR ; (6) by MO 2D-NMR with F MO Analysis of the relationship, to achieve shale oil mobility evaluation.

2. The method for shale oil mobility evaluation based on two-dimensional nuclear magnetic resonance experiment according to claim 1, characterized in that, In step (1), the sealed coring process is performed according to the industry standard Q / SH 0296-2009 “Oilfield Sealed Coring Well Geological Design Standard”.

3. The method of claim 1, wherein the method is characterized by, In step (2), the TOC determination experiment process is performed according to the national standard GB / T 19145-2022 “Determination of Total Organic Carbon in Sedimentary Rocks”.

4. The method for shale oil mobility evaluation based on two-dimensional nuclear magnetic resonance experiment of claim 1, wherein, In step (3), the step-by-step pyrolysis experiment process is performed according to the national standard GB / T 18602-2012 “Rock Pyrolysis Analysis”.

5. The method for shale oil mobility evaluation based on two-dimensional nuclear magnetic resonance experiment of claim 1, wherein, Step (3), S 1-1 Products obtained at 200 °C for the fractional pyrolysis experiment, S 1-2 Products obtained at 200-350 °C for the fractional pyrolysis experiment.

6. The method for shale oil mobility evaluation based on two-dimensional nuclear magnetic resonance experiment of claim 1, wherein, Step (4), shale oil mobility evaluation factor F MO = (S 1-1 + S 1-2 ) / TOC.

7. The method for shale oil mobility evaluation based on two-dimensional nuclear magnetic resonance experiments according to claim 1, characterized in that, In step (5), the two-dimensional nuclear magnetic resonance experiment process is performed according to the industry standard SY / T 6490-2007 “Laboratory Measurement Standard for Rock Sample Nuclear Magnetic Resonance Parameters”.

8. The method for shale oil mobility evaluation based on two-dimensional nuclear magnetic resonance experiment of claim 1, wherein, Step (5), the binuclear magnetic resonance mobile oil percentage MO 2D-NMR = (mobile oil before centrifugation - mobile oil after centrifugation) / mobile oil before centrifugation x 100%.

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