A method for evaluating the oil-bearing property of shale oil based on mud logging data

Abstract

The present invention relates to the technical field of reservoir oil-bearing property evaluation methods, and is a method for evaluating the oil-bearing property of shale oil based on mud logging data. The method includes using low-cost rock pyrolysis chromatography mud logging data and rock mineral data to propose a calculation formula for evaluating the oil-bearing property of shale oil reservoirs, and then intersecting with the effective porosity of nuclear magnetic logging. According to the intersection diagram, an evaluation interval is divided to form an evaluation chart for the oil-bearing property of shale oil reservoirs. The evaluation result of the reservoir oil-bearing property is obtained by combining the oil-bearing property index LI value of the shale oil reservoir. The present invention provides a technical solution for obtaining the oil-bearing property of a reservoir without nuclear magnetic logging. When it is actually applied in the Jimusaer shale oil block of the Xinjiang Oilfield, the goodness of fit can reach more than 0.85, the accuracy of the calculated oil-bearing property parameters can meet the requirements of reservoir evaluation, and at the same time, the cost of obtaining the oil-bearing property parameters is significantly reduced, thus providing a new way for the evaluation of the oil-bearing property of shale oil reservoirs.

Description

Technical Field

[0001] The present invention relates to the technical field of reservoir oil-bearing evaluation methods, and is a shale oil oil-bearing evaluation method based on logging data. Background Art

[0002] Shale oil reservoirs have the characteristics of source-reservoir integration, high organic carbon content, and the need for optimization of horizontal well section clusters. In the exploration and development process of shale oil, multiple technologies such as gas logging, nuclear magnetic resonance, and geochemical pyrolysis logging are commonly used in the prior art to carry out shale oil oil-bearing evaluation.

[0003] Gas logging directly calculates and intersects the gas logging component values (C 1 , C 2 , C 3 , iC 4 , nC 4 , iC 5 , nC 5 ), and different calculation methods form different interpretation and evaluation charts. Commonly used gas logging chart methods include: double logarithm method, light hydrocarbon ratio method, triangle method, PIXLER method, etc.

[0004] The nuclear magnetic resonance evaluation method only statistically analyzes the ranges and means of nuclear magnetic parameters such as nuclear magnetic porosity, permeability, oil saturation, and water saturation, and then makes reservoir classification and qualitative judgment of reservoir fluid properties based on the statistics.

[0005] At present, there are the following defects in using nuclear magnetic logging for reservoir evaluation in shale oil blocks: (1) The cost of single-well nuclear magnetic logging is expensive, resulting in not every horizontal well being arranged for nuclear magnetic logging projects; (2) There are multiple solutions in the interpretation and evaluation of the oil-bearing property of the reservoir by nuclear magnetic logging, and sometimes the interpretation and evaluation results deviate greatly from the actual situation. Therefore, it is very necessary to form a set of horizontal well reservoir oil-bearing evaluation technologies based on logging data to provide targeted geological evaluation basis for the segmented fracturing design of the horizontal section reservoir.

[0006] The geochemical pyrolysis chart method directly calculates and intersects the geochemical pyrolysis component values (gas content S 0 , gasoline content S 11 , kerosene and diesel content S 21 , wax and heavy oil content S 22 , gum and asphaltene content S 23 ) of reservoir rocks. Existing common calculation methods include S 1 = S 11 + S 21 × 0.67, S 2 = S 21 × 0.33 + S 22 + S 23 , ST = S 0+S 11 +S 21 +S 22 +S 23 , the common charts obtained according to these calculation methods are: S 2 *100 / ST - S 2 / S 1 Geochemical chart, S 1 / S 2 -S 1 / ST geochemical chart, (S 1 +S 0 ) / S 2 -ST geochemical chart.

[0007] The prior art has the following disadvantages:

[0008] (1) The existing evaluation methods lack strong regional pertinence, and the coincidence rate of mud logging evaluation is low. The gas logging method and the geochemical pyrolysis chart method currently used are mainly applicable to conventional sandstone reservoirs. They are no longer applicable to shale oil reservoirs, which are unconventional oil and gas reservoirs. Because shale oil has the characteristics of source-reservoir integration, high organic carbon content, and the need for horizontal well section cluster optimization, the oil-bearing property of the reservoir is affected not only by the physical properties of the reservoir but also by the mineral composition of the reservoir. These influencing factors need to be considered during evaluation.

[0009] (2) In the drilling construction of tight oil reservoirs, an oil-based mud drilling fluid system is widely used. A large amount of diesel, drilling fluid additives, etc. are added to these oil-based drilling fluids. Under the action of high temperature and high pressure at the bottom of the well, these diesel and additives invade the microfractures and pore spaces of the cuttings, causing cutting contamination. Therefore, when performing pyrolysis analysis on these cuttings, it will be found that the soluble hydrocarbon peaks S 11 、S 21 show abnormally high values (see attachment Figure 1 ).

[0010] (3) The cost of single-well nuclear magnetic logging is expensive, resulting in not every horizontal well being arranged for nuclear magnetic logging projects, and there are multiple interpretations for the oil-bearing property of the reservoir during interpretation and evaluation. Summary of the Invention

[0011] The present invention provides a method for evaluating the oil-bearing property of shale oil based on mud logging data, which overcomes the above-mentioned deficiencies of the prior art and can effectively solve the problem that the existing conventional mud logging parameter evaluation method is not applicable to shale oil reservoirs.

[0012] The technical solution of the present invention is achieved through the following measures: A method for evaluating the oil-bearing property of shale oil based on mud logging data, comprising the following steps:

[0013] First step, collect the evaluation parameters of the oil-bearing property of the shale oil reservoir: the evaluation parameters include the rock pyrolysis chromatography analysis parameters, the reservoir mineral analysis data, and the nuclear magnetic logging effective porosity data. The rock pyrolysis chromatography analysis parameters include the gas content S 0 , gasoline content S 11 , kerosene and diesel content S 21 , wax and heavy oil content S 22 , gum and asphaltene content S 23 ;

[0014] Rock pyrolysis analysis (Rock-Eva1) performs a programmed temperature rise on the analyzed sample to "evaporate" or "crack" the hydrocarbons in the sample at different temperatures. Then, carried by the carrier gas, the "evaporated" and "cracked" hydrocarbon gases in the sample are detected by a hydrogen flame ionization detector, thereby converting the gases with different mass fractions into corresponding current signals. After computer processing, the content of each component is recorded to generate a chromatogram. The parameters generated by pyrolysis are the gas content S 0 (mg / g), gasoline content S 11 (mg / g), kerosene and diesel content S 21 (mg / g), wax and heavy oil content S 22 (mg / g), gum and asphaltene content S 23 (mg / g);

[0015] Second step, screen sensitive minerals: Through the correlation analysis of the reservoir mineral analysis data of the shale oil block, combined with its logging nuclear magnetic porosity and mineral content, find out the sensitive mineral types and combinations that affect the nuclear magnetic porosity of the shale oil reservoir to obtain the physical property factor;

[0016] Third step, calculate the oil-bearing index of the shale oil reservoir. The calculation formula of the oil-bearing index of the shale oil reservoir is as follows:

[0017] LI = Ln(Ps×Pd)

[0018] where, LI represents the oil-bearing index of the shale oil reservoir, Ps represents the light and heavy component index of crude oil, Ps=(S 11 +S 21 ) / (S 22 +S 23 ); Pd represents the physical property factor;

[0019] Fourth step: Take Ln(Ps×Pd) as the abscissa and the nuclear magnetic logging effective porosity (CMRP) as the ordinate, and cross the two to obtain a cross plot. Divide the evaluation interval according to the nuclear magnetic logging comparison results of the sample points in the cross plot, that is, form the oil-bearing evaluation chart of the shale oil reservoir. The oil-bearing evaluation chart of the shale oil reservoir divides the oil-bearing property of the reservoir according to the oil-bearing index LI value of the shale oil reservoir.

[0020] The following is a further optimization and / or improvement of the above-mentioned inventive technical solution:

[0021] In the above first step, the gasoline content S 11 , the kerosene and diesel oil content S 21 are respectively the amounts of liquid hydrocarbons measured at a constant temperature when the program rises from 90°C to 350°C in pyrolysis chromatography analysis.

[0022] Among the detected hydrocarbon compositions, the proportion of liquid saturated hydrocarbons is relatively high. Especially under the condition of white oil-based drilling fluid, the S 21 value is extremely high. Therefore, S 11 and S 21 are preferably used as important parameters for evaluating the oil-bearing property of shale oil reservoirs in rock pyrolysis geochemical logging.

[0023] For the Jimusa'er shale oil block in the Xinjiang Oilfield mentioned above, the sensitive minerals affecting the nuclear magnetic porosity of the shale oil reservoir are the plagioclase and dolomite mineral combinations. According to the mineral contents of plagioclase and dolomite, the plagioclase-dolomite ratio is calculated, and the plagioclase-dolomite ratio is the physical property factor, Pd = the content of plagioclase / the content of dolomite.

[0024] The mineral contents of plagioclase and dolomite can be obtained by X-ray diffraction technology; both the plagioclase content and the dolomite content can be in percentage content (%).

[0025] For the Jimusa'er shale oil block in the Xinjiang Oilfield mentioned above, when the LI > value is 3.0, the reservoir is a Class I reservoir; when 1.5 < LI value < 3.0, the reservoir is a Class II reservoir; when the LI value < 1.5, the reservoir is a Class III reservoir.

[0026] The above-mentioned method for evaluating the oil-bearing property of shale oil based on logging data is especially applicable to the condition of oil-based mud drilling fluid, and the cuttings samples used for evaluation and analysis have been contaminated.

[0027] The present invention establishes evaluation indexes in an intuitive form, and avoids the huge gap caused by data distortion through the introduction of ratio methods and mineral combinations, thereby forming effective oil-bearing property evaluation indexes. In addition, through parameter extraction, mathematical statistics, combined calculation, and fitting the nuclear magnetic porosity to obtain a calculation formula, the comprehensive parameters calculated can identify the oil-bearing property of shale oil reservoirs. The core method of data processing is reflected by the calculation formula. Using the comprehensive parameters obtained from the calculation formula, data intersection is carried out in the horizontal and vertical coordinates, and finally evaluation indexes are established. The evaluation indexes visually display the oil-bearing property of shale oil reservoirs, have good practical value, and effectively improve work efficiency.

[0028] The present invention provides a technical solution for obtaining the oil-bearing property of a reservoir without nuclear magnetic logging. By using low-cost rock pyrolysis chromatography logging data and rock mineral data, an evaluation formula for calculating the oil-bearing property of a shale oil reservoir is proposed, and then it is cross-plotted with the effective porosity of nuclear magnetic logging. When it is actually applied in the Jimusar shale oil block of Xinjiang Oilfield, the goodness of fit R 2 can reach above 0.85, and the accuracy of the calculated oil-bearing property parameters can meet the requirements of reservoir evaluation. At the same time, the cost of obtaining the oil-bearing property parameters is reduced by more than 40%. Thus, a new way is provided for the evaluation of the oil-bearing property of shale oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Attached Figure 1 is a pyrolysis analysis diagram of oil-based drilling fluid cuttings.

[0030] Attached Figure 2 is a flow chart of the method of the present invention.

[0031] Attached Figure 3 is a formula cross-plot of the present invention.

[0032] Attached Figure 4 is a schematic diagram of the evaluation chart result obtained according to the evaluation method of the present invention.

[0033] Attached Figure 5 is a schematic diagram of the evaluation result obtained according to the evaluation methods described in Examples 2 and 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The present invention is not limited by the following embodiments, and the specific implementation manners can be determined according to the technical solution of the present invention and the actual situation.

[0035] The present invention will be further described below in conjunction with the embodiments:

[0036] Example 1: As shown in the attached Figure 2 , the method for evaluating the oil-bearing property of shale oil based on logging data includes the following steps:

[0037] First step, collect the evaluation parameters of the oil-bearing property of the shale oil reservoir: the evaluation parameters include rock pyrolysis chromatography analysis parameters (rock pyrolysis parameters), reservoir mineral analysis data, and nuclear magnetic logging effective porosity data. The rock pyrolysis chromatography analysis parameters include gas content S 0 , gasoline content S 11 , kerosene and diesel content S 21 , wax and heavy oil content S 22 , gum and asphaltene content S 23 ;

[0038] Step 2: Screen sensitive minerals: Analyze the reservoir mineral data of the shale oil block, and through the correlation analysis of its logging nuclear magnetic porosity and mineral content, find out the types and combinations of sensitive minerals that affect the nuclear magnetic porosity of the shale oil reservoir, and obtain the physical property factors;

[0039] Step 3: Calculate the oil-bearing index of the shale oil reservoir. The calculation formula of the oil-bearing index of the shale oil reservoir is as follows:

[0040] LI = Ln(Ps×Pd)

[0041] Where, LI represents the oil-bearing index of the shale oil reservoir, Ps represents the light and heavy component index of crude oil, Ps=(S 11 +S 21 ) / (S 22 +S 23 ); Pd represents the physical property factor;

[0042] Step 4: Take Ln(Ps×Pd) as the abscissa and the effective nuclear magnetic logging porosity as the ordinate, and cross the two to obtain a cross plot. Divide the evaluation interval according to the comparison result of the nuclear magnetic logging of the sample points in the cross plot, that is, form an oil-bearing evaluation chart of the shale oil reservoir. The oil-bearing evaluation chart of the shale oil reservoir divides the oil-bearing property of the reservoir according to the oil-bearing index LI value of the shale oil reservoir.

[0043] For the Jimusa'er shale oil block of Xinjiang Oilfield, the sensitive minerals that affect the nuclear magnetic porosity of the shale oil reservoir are the plagioclase and dolomite mineral combinations. According to the mineral contents of plagioclase and dolomite, calculate the plagioclase-dolomite ratio, and the plagioclase-dolomite ratio is the physical property factor, Pd = content of plagioclase / content of dolomite. The cross plot drawn according to Step 4 is as Figure 3 shown, and the oil-bearing evaluation chart of the shale oil reservoir drawn is as Figure 4 shown.

[0044] Example 2: For the well section at 4867m of Well J2 in the Jimusa'er shale oil block of Xinjiang Oilfield, this method for evaluating the oil-bearing property of shale oil based on logging data includes the following steps:

[0045] (1) Prepare geochemical pyrolysis parameter data (rock pyrolysis parameters) and sensitive mineral parameters:

[0046] Take the geochemical pyrolysis parameters at the well depth of 4867m of this well as the geochemical pyrolysis data of the oil and gas shows in this section. Among them, the pyrolysis geochemical component S 0 =0.004mg / g, S 11 =2.590mg / g, S 21 =5.790mg / g, S 22 =2.535mg / g, S 23= 0.595 mg / g; Take the X-ray diffraction mineral content data at a well depth of 4867 m. Among them, the plagioclase content is 20.68% and the dolomite content is 18.70%;

[0047] (2) Calculate Ps = (S 11 + S 21 ) / (S 22 + S 23 ) = 2.68, the plagioclase-dolomite ratio Pd = 1.105, LI = ln(Ps * Pd) = 1.08;

[0048] (3) The calculated LI value < 1.5, and the obtained evaluation and interpretation result is Class III reservoir; the nuclear magnetic logging porosity is 5.9%.

[0049] Example 3: For the well section at 4475 m of Well J2 in the Jimusa'er shale oil block of Xinjiang Oilfield, the method for evaluating the oil-bearing property of shale oil based on logging data includes the following steps:

[0050] (1) Prepare geochemical pyrolysis parameter data and sensitive mineral parameters:

[0051] Take the geochemical pyrolysis parameters at a well depth of 4475 m as the geochemical pyrolysis data of oil and gas shows in this section. Among them, the pyrolysis geochemical component S 0 = 0.007 mg / g, S 11 = 1.680 mg / g, S 21 = 11.232 mg / g, S 22 = 0.682 mg / g, S 23 = 0.267 mg / g; Take the X-ray diffraction mineral content data at a well depth of 4475 m. Among them, the plagioclase content is 42.63% and the dolomite content is 7.40%;

[0052] (2) Calculate Ps = (S 11 + S 21 ) / (S 22 + S 23 ) = 13.70, the plagioclase-dolomite ratio Pd = 5.76, LI = ln(Ps * Pd) = 4.37;

[0053] (3) The calculated LI value > 3, and the obtained evaluation and interpretation result is Class I reservoir; the nuclear magnetic logging porosity is 18.8%.

[0054] As shown in the Figure 5 appendix, comparing the evaluation results of Examples 2 and 3 with the nuclear magnetic logging porosity verifies the correctness of the evaluation results.

[0055] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effects. Non-essential technical features can be added or subtracted according to actual needs to meet the requirements of different situations.

Claims

1. A method for evaluating the oil-bearing property of shale oil based on mud logging data, characterized in that it includes the following steps: Step 1: Collect evaluation parameters for the oil-bearing property of the shale oil reservoir: The evaluation parameters include rock pyrolysis chromatography analysis parameters, reservoir mineral analysis data, and nuclear magnetic logging effective porosity data. The rock pyrolysis chromatography analysis parameters include gas content S 0 , gasoline content S 11 , kerosene and diesel content S 21 , wax and heavy oil content S 22 , gum and asphaltene content S 23 ; Second step, screening sensitive minerals: Analyze the reservoir mineral data of the shale oil block, and through the correlation analysis of its logging nuclear magnetic porosity and mineral content, find out the sensitive mineral types and combinations that affect the nuclear magnetic porosity of the shale oil reservoir, and obtain the physical property factor; Third step, calculate the oil-bearing index of the shale oil reservoir. The calculation formula of the oil-bearing index of the shale oil reservoir is as follows: LI = Ln(Ps×Pd) Among them, LI represents the oil-bearing index of shale oil reservoirs, Ps represents the light and heavy component index of crude oil, and Ps = (S 11 + S 21 ) / (S 22 + S 23 ); Pd represents the physical property factor; Fourth step: Take Ln(Ps×Pd) as the abscissa and the nuclear magnetic logging effective porosity as the ordinate, and cross the two to obtain a cross plot. Divide the evaluation interval according to the comparison result of the nuclear magnetic logging of the sample points in the cross plot, that is, form an oil-bearing evaluation chart of the shale oil reservoir. The oil-bearing evaluation chart of the shale oil reservoir divides the oil-bearing property of the reservoir according to the oil-bearing index LI value of the shale oil reservoir; It is applicable to the condition of oil-based mud drilling fluid, and the cuttings samples used for evaluation and analysis have been contaminated.

2. The method for evaluating the oil-bearing property of shale oil based on mud logging data according to claim 1, characterized in that In the first step, the gasoline content S 11 , the kerosene and diesel oil content S 21 are respectively the amounts of liquid hydrocarbons measured at a constant temperature when the program rises from 90°C to 350°C in pyrolysis chromatographic analysis.

3. The method for evaluating the oil-bearing property of shale oil based on mud logging data according to claim 1 or 2, characterized in that For the Jimusaer shale oil block of Xinjiang Oilfield, the sensitive minerals that affect the nuclear magnetic porosity of the shale oil reservoir are the plagioclase and dolomite mineral combination. According to the mineral content of plagioclase and dolomite, calculate the plagioclase-dolomite ratio, and the plagioclase-dolomite ratio is the physical property factor, Pd = content of plagioclase / content of dolomite.

4. The method for evaluating the oil-bearing property of shale oil based on mud logging data according to claim 1 or 2, characterized in that For the Jimusaer shale oil block of Xinjiang Oilfield, when LI > 3.0, the reservoir is a Class I reservoir; when 1.5 < LI < 3.0, the reservoir is a Class II reservoir; when LI < 1.5, the reservoir is a Class III reservoir.

5. The method for evaluating the oil-bearing property of shale oil based on mud logging data according to claim 3, characterized in that For the Jimusaer shale oil block of Xinjiang Oilfield, when LI > 3.0, the reservoir is a Class I reservoir; when 1.5 < LI < 3.0, the reservoir is a Class II reservoir; when LI < 1.5, the reservoir is a Class III reservoir.

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