Method for evaluating mobility of continental facies shale oil

Abstract

The invention relates to a continental facies shale oil mobility evaluation method, and belongs to the technical field of shale oil development. Comprising the following steps: step 1, carrying out a two-dimensional nuclear magnetic resonance experiment to obtain the content of free hydrocarbon SF; 2, carrying out a total organic carbon determination experiment to obtain a total organic carbon TOC value of the sample; 3, carrying out a low-temperature nitrogen adsorption experiment, and calculating the fractal dimension D of the sample; and 4, establishing a correlation between the fractal dimension D and the shale oil mobility evaluation factor SF / TOC so as to evaluate the mobility of the shale oil. According to the shale oil mobility evaluation method provided by the invention, only one experiment of low-temperature nitrogen adsorption needs to be carried out, so that the cost is saved. The shale oil mobility is evaluated by calculating the fractal dimension D of the shale sample, and the method has the advantages of being scientific in experimental principle, simple and convenient to operate, excellent in application effect, green, safe and environmentally friendly.

Description

Technical Field

[0001] The invention relates to a method for evaluating the mobility of continental shale oil, and belongs to the technical field of shale oil development. Background Art

[0002] The study of shale oil mobility is of great significance for the optimization and efficient development of favorable areas, and is a key indicator for evaluating the commercial value of shale oil resources. Continental shale formations have rapid sedimentary phase changes and strong heterogeneity, as well as complex lithology and low thermal maturity. Shale oil has characteristics such as high viscosity and high wax content, which leads to large differences in the mobility of shale oil in different lithofacies of continental shale formations.

[0003] Geologists have conducted a lot of research on the evaluation methods of shale oil mobility. Zhang Linye et al. published a paper on October 13, 2014 in the Journal of Petroleum Exploration and Development titled "Lake-phase shale oil mobility - taking the Dongying sag in the Jiyang Depression of the Bohai Bay Basin as an example". Specifically, the terrestrial shale of the Paleogene Shahejie Formation in the Dongying Depression of the Bohai Bay Basin was used as the research object. Through systematic analysis of shale porosity, compression coefficient, rock mechanical properties, oil saturation, gas-oil ratio and crude oil saturation pressure, the shale oil mobility was studied from the perspective of formation energy.

[0004] On September 26, 2022, Chang Jiaqi et al. publicly published the oil content and mobility characteristics of shales in different lithofacies of the Fengcheng Formation in the Mahu Sag in the Journal of Central South University (Natural Science Edition). Specifically, the oil content and mobility of shales in different lithofacies of the Fengcheng Formation in the Mahu Sag were studied through experimental analysis methods such as organic geochemistry, low-temperature N2 adsorption and multi-temperature stage pyrolysis. The experimental results showed that the siltstone phase has the best oil content and mobility, followed by the felsic shale phase. Shale oil is mainly stored in pores with pore diameters >10nm.

[0005] The invention patent with patent number CN109991123B provides a geochemical evaluation method for the mobility of shale oil resources. By conducting geochemical analysis on typical oil-producing and non-oil-producing layer samples in the study area, a geochemical parameter identification chart for shale oil mobility is established, and finally the shale oil mobility evaluation is achieved. This method requires geochemical experiments on a large number of samples when establishing the shale oil mobility identification chart, and there are doubts about the applicability of the chart to shale samples in different regions.

[0006] To date, there is no method in the prior art that can evaluate the mobility of shale oil with only a single experiment. Summary of the invention

[0007] In order to solve the above problems existing in the prior art, the present invention discloses a method for evaluating the mobility of continental shale oil, thereby solving the problem that the existing method is complex and does not meet the safety and environmental protection requirements when evaluating the mobility of shale oil.

[0008] The technical solution adopted by the present invention is: a method for evaluating the mobility of continental shale oil, comprising the following steps:

[0009] Step 1: Perform 2D NMR experiments to obtain free hydrocarbon S F content;

[0010] Step 2: Conduct a total organic carbon determination experiment to obtain the total organic carbon TOC value of the sample;

[0011] Step 3: Conduct low-temperature nitrogen adsorption experiments and calculate the fractal dimension D of the sample;

[0012] Step 4: Establish fractal dimension D and shale oil mobility evaluation factor S F / TOC to evaluate the mobility of shale oil.

[0013] Furthermore, before performing the two-dimensional nuclear magnetic resonance experiment in step 1, the sample surface needs to be cleaned.

[0014] Furthermore, the two-dimensional nuclear magnetic resonance experimental sample is cylindrical, with a diameter of 2.5 cm and a length of 2 cm.

[0015] Furthermore, the two-dimensional nuclear magnetic resonance experiment is used to calculate the shale free hydrocarbon S F When free hydrocarbon S F The criteria for determining the region are T2>1ms, T1 / T2>10; T1 is the longitudinal relaxation time, which refers to the relaxation time taken for the longitudinal magnetization vector to recover to 63% of the equilibrium state; T2 is the transverse relaxation time, which refers to the time taken for the transverse magnetization vector to decay to 37% of its maximum value.

[0016] Furthermore, before performing the TOC and low-temperature nitrogen adsorption experiments in step 2, the sample needs to be ground into powder.

[0017] Furthermore, the shale sample is ground into powder using an agate mortar, and the powder is 200 mesh.

[0018] Furthermore, before the low-temperature nitrogen adsorption experiment in step 3, the shale powder sample needs to be subjected to organic matter extraction, the organic solvent is chloroform, and the extraction time is not less than 72 hours.

[0019] Furthermore, in step 3, the extracted shale powder sample needs to be pretreated before the low-temperature nitrogen adsorption experiment.

[0020] Furthermore, the pretreatment process is to heat the shale powder sample at 105° C. under vacuum conditions to remove impurity gases and water in the powder sample, and the pretreatment process lasts for no less than 12 hours.

[0021] Furthermore, in step 3, the fractal dimension D is calculated using the FHH model, and the FHH model is:

[0022] LnV=KLn(Ln(P0 / P))+C(1)

[0023] In formula (1), P0 is the saturated vapor pressure, MPa; P is the equilibrium pressure, MPa; V is the adsorption volume, cm3 / g; K is the linear correlation coefficient; C is a constant; and the fractal dimension D=K+3.

[0024] Furthermore, in step 4, the average value of the fractal dimension D is calculated and recorded as D avg , D avg Evaluate shale oil mobilization.

[0025] The present invention discloses a method for evaluating the mobility of continental shale oil, which has the beneficial effect that when the conventional method is used to evaluate the mobility of shale oil, the free hydrocarbon S F The experimental equipment for TOC determination is expensive, the experimental operation method is complicated, and it does not meet the requirements of safety and environmental protection. The shale oil mobility evaluation method provided by the present invention only needs to carry out one experiment of low-temperature nitrogen adsorption, which saves costs. The shale oil mobility is evaluated by calculating the fractal dimension D of the shale sample, which has the characteristics of scientific experimental principle, simple operation method, excellent application effect, green, safe and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0027] Figure 1 :Calculation diagram of fractal dimension D of low temperature nitrogen adsorption experiment;

[0028] Figure 2 : S measured in the embodiment of the present invention F / TOC and D avg Relationship diagram.

[0029] Specific implementation methods

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In order to further understand the content of the present invention, the present invention is further described below in conjunction with specific implementation methods.

[0032] The well logging methods used in the following embodiments are conventional methods unless otherwise specified. The present invention is described in detail with reference to the accompanying drawings as follows:

[0033] Embodiment 1:

[0034] like Figures 1-2 As shown, a method for evaluating the mobility of continental shale oil comprises the following steps:

[0035] First, clean the surface of the shale sample with a wet towel and allow it to air dry naturally before conducting subsequent experiments.

[0036] Step 1: Conduct a two-dimensional nuclear magnetic resonance experiment to obtain the free hydrocarbon SF content;

[0037] The 2D NMR experimental instrument is the American MRCores-XX high-precision desktop NMR unconventional core analyzer;

[0038] The experimental operation methods and procedures are carried out in accordance with the standard of "SYT6490-2007- Laboratory Measurement Specifications for Nuclear Magnetic Resonance Parameters of Rock Samples";

[0039] The 2D NMR experimental sample is cylindrical with a diameter of 2.5 cm and a length of 2 cm.

[0040] When calculating shale free hydrocarbon SF using two-dimensional nuclear magnetic resonance experiments, the criteria for determining the region to which the free hydrocarbon SF belongs are T2>1ms and T1 / T2>10.

[0041] Step 2: Conduct a total organic carbon determination experiment to obtain the sample TOC value;

[0042] Before conducting TOC and low-temperature nitrogen adsorption experiments, the sample needs to be ground into powder. Specifically, the shale sample is ground into powder using an agate mortar, and the powder is 200 mesh.

[0043] The TOC experimental instrument is a CS-230 carbon and sulfur analyzer;

[0044] The experimental operation methods and processes were carried out in accordance with the standard "GB / T19145-2003 Determination of total organic carbon in sedimentary rocks".

[0045] Step 3: Conduct low-temperature nitrogen adsorption experiments and calculate the fractal dimension D of the sample;

[0046] The shale powder sample is subjected to organic matter extraction, the organic solvent is chloroform, and the extraction time is not less than 72 hours. The extracted shale powder sample is then pretreated before the experiment. The pretreatment process is to heat the shale powder sample under vacuum conditions at 105°C to remove impurity gases and water in the powder sample, and the pretreatment process lasts for not less than 12 hours.

[0047] The low-temperature nitrogen adsorption experiment instrument is the American Michael ASAP2460 specific surface and pore size analyzer;

[0048] The experimental operation methods and processes are carried out in accordance with the standard "ISO-9277 / GB / T19587-2004, Determination of specific surface area of ​​solid materials by gas adsorption BET method".

[0049] Calculate the fractal dimension using the FHH model:

[0050] LnV=KLn(Ln(P0 / P))+C(1)

[0051] In formula (1), P0 is the saturated vapor pressure, MPa; P is the equilibrium pressure, MPa; V is the adsorption volume, cm3 / g; K is the linear correlation coefficient; C is a constant. Fractal dimension D = K+3.

[0052] like Figure 1 As shown: LnV and Ln (Ln (P0 / P)) have a two-stage linear relationship, indicating that there are two types of fractal dimensions, denoted as D1 and D2;

[0053] Step 4: Calculate the average value of D1 and D2, denoted as D avg . Build D avg The correlation between the mobility evaluation factor S and the shale oil mobility evaluation factor S F / TOC indicates the mobility of shale oil;

[0054] like Figure 2 As shown, the mobility evaluation factor S F / TOC and D avg The correlation coefficient R 2 is 0.8622, indicating that the mobility evaluation factor S F / TOC and D avg There is a good correlation between the two. avg Evaluate shale oil mobilization.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the mobility of continental shale oil, characterized in that: The following steps are involved: Step 1: Perform 2D NMR experiments to obtain free hydrocarbon S F content; Step 2: Conduct a total organic carbon determination experiment to obtain the total organic carbon TOC value of the sample; Step 3: Conduct low-temperature nitrogen adsorption experiments and calculate the fractal dimension D of the sample; Step 4: Establish fractal dimension D and shale oil mobility evaluation factor S F / TOC to evaluate the mobility of shale oil.

2. A method for evaluating the mobility of continental shale oil according to claim 1, characterized in that: Step 1 Before conducting a two-dimensional NMR experiment, the sample surface needs to be cleaned.

3. A method for evaluating the mobility of continental shale oil according to claim 1, characterized in that: In step 1, the 2D NMR experimental sample is cylindrical, with a diameter of 2.5 cm and a length of 2 cm.

4. A method for evaluating the mobility of continental shale oil according to claim 1, characterized in that: In step 1, the shale free hydrocarbon S is calculated using the two-dimensional nuclear magnetic resonance experiment. F When free hydrocarbon S F The criteria for determining the region are T2>1ms, T1 / T2>10; T1 is the longitudinal relaxation time, which refers to the relaxation time taken for the longitudinal magnetization vector to recover to 63% of the equilibrium state; T2 is the transverse relaxation time, which refers to the time taken for the transverse magnetization vector to decay to 37% of its maximum value.

5. The method for evaluating the mobility of continental shale oil according to claim 1, characterized in that: Step 2 Before conducting the TOC and low-temperature nitrogen adsorption experiments, the sample needs to be ground into powder; the shale sample is ground into powder using an agate mortar, and the powder is 200 mesh.

6. A method for evaluating the mobility of continental shale oil according to claim 1, characterized in that: Before the low-temperature nitrogen adsorption experiment in step 3, the shale powder sample needs to be subjected to organic matter extraction, the organic solvent is chloroform, and the extraction time is not less than 72 hours.

7. A method for evaluating the mobility of continental shale oil according to claim 6, characterized in that: In step 3, the extracted shale powder sample needs to be pretreated before the low-temperature nitrogen adsorption experiment.

8. A method for evaluating the mobility of continental shale oil according to claim 7, characterized in that: The pretreatment process is to heat the shale powder sample at 105° C. under vacuum conditions to remove impurity gases and water in the powder sample. The pretreatment process lasts for no less than 12 hours.

9. A method for evaluating the mobility of continental shale oil according to claim 1, characterized in that: In step 3, the fractal dimension D is calculated using the FHH model, which is: LnV=KLn(Ln(P0 / P))+C(1) In formula (1), P0 is the saturated vapor pressure, MPa; P is the equilibrium pressure, MPa; V is the adsorption volume, cm3 / g; K is the linear correlation coefficient; C is a constant; and the fractal dimension D=K+3.

10. A method for evaluating the mobility of continental shale oil according to claim 9, characterized in that: In step 4, the average value of the fractal dimension D is calculated and recorded as D avg , D avg Evaluate shale oil mobilization.

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