A method for evaluating shale oil under oil-based mud

Abstract

The application provides a shale oil evaluation method under oil-based mud, which comprises hydrocarbon source rock grade evaluation and fluid property evaluation. 20 The oil-bearing and water-bearing indication board is established by the late peak area value and the Pr+Ph value of the gas chromatogram, so that the fluid property of the formation under the oil-based mud pollution is evaluated. The application sums and calculates the ratio of the pyrolysis S2 and S4 and the gas chromatogram component peak area which are not polluted by the oil-based mud, establishes the hydrocarbon source rock abundance evaluation standard and the oil-bearing and water-bearing indication board, and then according to the W / S of the pyrolysis chromatogram of the well to be evaluated and the TOC value, the point is cast on the board, so that the hydrocarbon source rock abundance and the fluid property of the formation are evaluated, and the subjective difference of the artificial identification is reduced.

Description

Technical Field

[0001] This invention belongs to the field of petroleum exploration sedimentary reservoir evaluation technology, specifically relating to a method for evaluating shale oil under oil-based mud. Background Technology

[0002] Evaluation logging techniques mainly include geochemical pyrolysis analysis and gas chromatography analysis. Geochemical pyrolysis analysis is an important parameter for evaluating shale oil source rocks. Due to oil-based mud contamination, the S0 and S1 parameters in the source rock evaluation data are distorted, and only solid hydrocarbons S2 and S4 are usable parameters. Gas chromatography analysis focuses on nC9-nC... 40 The analysis focuses on peak shape and carbon number variations to determine formation fluid properties, specifically analyzing the components of the corresponding geochemical pyrolysis fluid S1. Because some components in S1 (nC...)... 20 Previous data has been distorted by contamination from liquid oil-based mud, which in turn affects the evaluation of the fluid properties of shale oil reservoirs.

[0003] Gas chromatography (GC) is advantageous because it can detect a wide range of carbon numbers and obtain numerous parameters, enabling it to reflect changes in formation fluid properties from multiple perspectives. It is particularly effective in assessing the degree of secondary alteration of crude oil, and its peak shape changes significantly evaluate water cut. However, peak shape variations are greatly influenced by oil-based drilling mud (nC). 20 Previous data was distorted due to contamination by oil-based mud, making it impossible to further determine the abundance of oil and gas and the properties of the fluid, thus affecting the accuracy of the assessment.

[0004] CN201910247411.3 describes a geochemical evaluation method for the mobility of shale oil resources, comprising the following steps: Step 1) Selecting typical oil-producing and non-oil-producing layer samples from the study area; Step 2) Performing organic carbon and pyrolysis analysis on typical samples; Step 3) Establishing a geochemical parameter identification chart for shale oil mobility; Step 4) Performing organic carbon and pyrolysis analysis on samples under evaluation; Step 5) Evaluating the mobility of shale oil resources in mudstone and shale samples. This method fully utilizes existing geochemical techniques and data to characterize shale oil content and crude oil properties, and evaluate shale oil mobility. However, this method is only applicable to uncontaminated shale oil resources and is not suitable for shale oil under oil-based mud. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating shale oil under oil-based mud, overcoming the aforementioned technical problems existing in the prior art.

[0006] Therefore, the technical solution provided by the present invention is as follows:

[0007] A method for evaluating shale oil under oil-based mud includes source rock grade evaluation and fluid property evaluation. The source rock grade evaluation establishes a regression equation using pyrolysis data S2 and S4 that are not contaminated by oil-based mud, calculates TOC and S1, and evaluates the source rock grade based on the TOC and S1+S2 values.

[0008] S1 represents the hydrocarbon content per unit mass of rock detected at 300℃, mainly consisting of liquid hydrocarbons (mg / g).

[0009] S2 represents the hydrocarbon content per unit mass of rock detected at 300℃-600℃, mainly in solid form (mg / g).

[0010] S4 represents the residual organic carbon content per unit mass of rock after pyrolysis, mainly consisting of unpyrolyzable residual organic carbon (mg / g); TOC represents total organic carbon.

[0011] The fluid properties were evaluated using gas chromatography (NCC) uncontaminated by oil-based mud. 20 By comparing the peak area with the Pr+Ph values ​​from gas chromatography, an indicator chart for oil and water content was established to evaluate the properties of formation fluids contaminated with oil-based mud.

[0012] Wherein, Pr is pterosaridine; Ph is phytane.

[0013] The specific process for evaluating the grade of source rocks is as follows:

[0014] Step 1) Extract the pyrolysis parameters S2 and S4 of all analytical samples in the region, and establish a summary table of the area of ​​pyrolysis parameters S2+S4 in the region;

[0015] Step 2) Collect measured TOC values ​​of each layer in the region, analyze the correlation between TOC values ​​and S2+S4 values, and establish a correlation regression equation;

[0016] Step 3) Apply the correlation regression equation to obtain the TOC correction data of shale oil reservoir under oil-based drilling fluid conditions, and obtain the value of S1 in shale oil based on the TOC correction data;

[0017] Step 4) Calculate the S2+S1 value to obtain the abundance of source rocks and evaluate the grade of source rocks.

[0018] The specific steps for evaluating fluid properties are as follows:

[0019] Step 1) Extract nC from the gas chromatographic parameters of all analytical samples within the region. 20 Based on the peak areas of each component, a summary table of regional gas chromatographic component peak areas was established.

[0020] Step 2) Collect oil test data for each layer within the region, and calculate the corresponding gas chromatographic group nC based on different fluid properties. 20 Summary table of peak area;

[0021] Step 3) Based on nC 20 The peak area of ​​the uncontaminated component W is calculated, and the peak area S of Pr+Ph, which is less affected by the strata, is also obtained.

[0022] Step 4) Summarize the W and S values ​​for different fluid properties and calculate the W / S value;

[0023] Step 5) Create corresponding charts based on W and W / S values ​​to divide different fluid zones;

[0024] Step 6) Repeat steps 3) and 4) for the well to be evaluated, and plot the obtained W and W / S values ​​on the chart of step 5). Determine the fluid properties based on the area where the plotted points are located.

[0025] The correlation regression equation established in step 2) is TOC=K*(S2+S4)+R.

[0026] Step 3) In shale oil, S1 = (TOC - S4 / 10) / 0.083 - S2).

[0027] When TOC is less than 0.5% and S1+S2 is less than 2, the source rock is classified as a non-source rock; when TOC is 0.5-1 and S1+S2 is 2-6, the source rock is classified as a general source rock; when TOC is 1-2 and S1+S2 is 6-20, the source rock is classified as a good source rock; when TOC is not less than 2 and S1+S2 is not less than 20, the source rock is classified as a high-quality source rock.

[0028] Step 3) The intact peak area W of the uncontaminated component is nC 20 -nC 28 The area and sum of.

[0029] Different fluid zones include oil zone, water zone, and dry zone.

[0030] The beneficial effects of this invention are:

[0031] The shale oil evaluation method under oil-based mud provided by this invention applies pyrolysis technology. Based on the pyrolysis S2 and S4 that are not contaminated by oil-based mud, a regression equation is established, which can accurately calculate the actual TOC and S1 of the formation, thereby evaluating the grade of the source rock.

[0032] Based on the characteristics of stable Pr and Ph structures in gas chromatography and the susceptibility of crude oil to oxidation in oil-water miscible phases, this invention utilizes nC... 20 Subsequently, the relationship between gas chromatographic peak area and Pr+Ph formed a new standard and evaluation method for fluid property identification, which is of great significance for improving the accuracy of oil and gas display interpretation and assisting oilfield exploration and development.

[0033] This invention obtains new parameters by summing and ratioring the peak areas of pyrolysis S2 and S4 components, which are not contaminated by oil-based mud, and gas chromatographic components. Based on these new parameters and regional oil testing data, a standard for evaluating the abundance of source rocks and an indicator chart for oil and water content are established. Then, points are plotted on the chart based on the derived parameters (W / S) of the pyrolysis chromatography of the well to be evaluated and the calculated TOC value, thereby evaluating the abundance of source rocks and fluid properties of the formation and reducing the subjective differences in human judgment. Attached Figure Description

[0034] Figure 1 This is the correlation regression line between (S2+S4) and TOC in the embodiment;

[0035] Figure 2 This is the correlation between the measured TOC values ​​and the TOC correction data in the embodiments;

[0036] Figure 3 This is a diagram of reservoir fluid properties in the embodiments;

[0037] Figure 4 This is the TOC-S1 distribution diagram of well X in the embodiment;

[0038] Figure 5 This is the fluid property projection point for Well X. Detailed Implementation

[0039] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0040] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention.

[0041] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0042] Example 1

[0043] This invention provides a method for evaluating shale oil under oil-based mud, including source rock grade evaluation and fluid property evaluation. The source rock grade evaluation establishes a regression equation using pyrolysis data S2 and S4 that are not contaminated by oil-based mud, calculates TOC and S1, and evaluates the source rock grade based on the TOC and S1+S2 values.

[0044] S1 represents the hydrocarbon content per unit mass of rock detected at 300℃, mainly consisting of liquid hydrocarbons (mg / g).

[0045] S2 represents the hydrocarbon content per unit mass of rock detected at 300℃-600℃, mainly in solid form (mg / g).

[0046] S4 represents the residual organic carbon content per unit mass of rock after pyrolysis, mainly consisting of unpyrolyzable residual organic carbon (mg / g); TOC represents total organic carbon.

[0047] The fluid properties were evaluated using gas chromatography (NCC) uncontaminated by oil-based mud. 20 By comparing the peak area with the Pr+Ph values ​​from gas chromatography, an indicator chart for oil and water content was established to evaluate the properties of formation fluids contaminated with oil-based mud.

[0048] Wherein, Pr is pterosaridine; Ph is phytane.

[0049] This invention applies pyrolysis and gas chromatography analysis techniques to accurately evaluate the characteristics of source rocks and the abundance of oil and gas. Based on relevant parameters and mathematical equations, it enables interpreters to quickly determine the abundance of source rocks and fluid properties in formations, so as to draw correct interpretation conclusions and solve the problem of difficulty in identifying oil and gas abundance or source rock grade and fluid properties caused by oil-based mud contamination.

[0050] Example 2

[0051] Based on Example 1, this example provides a method for evaluating shale oil under oil-based mud, and the specific process for evaluating the source rock grade is as follows:

[0052] Step 1) Extract the pyrolysis parameters S2 and S4 of all analytical samples in the region and establish a summary table of the pyrolysis parameter S2+S4 values ​​in the region;

[0053] Step 2) Collect measured TOC values ​​of each layer in the region, analyze the correlation between TOC values ​​and S2+S4 values, and establish a correlation regression equation; the established correlation regression equation is TOC=K*(S2+S4)+R;

[0054] Step 3) Apply the correlation regression equation to obtain the TOC correction data of shale oil reservoir under oil-based drilling fluid conditions, and obtain the value of S1 in shale oil based on the TOC correction data;

[0055] Step 4) Calculate the S2+S1 value to obtain the abundance of source rocks and evaluate the grade of source rocks.

[0056] Example 3

[0057] Based on Example 1, this example provides a method for evaluating shale oil under oil-based mud. The specific steps for evaluating fluid properties are as follows:

[0058] Step 1) Extract nC from the gas chromatographic parameters of all analytical samples within the region. 20 Based on the peak areas of the components, a summary table of regional gas chromatographic component peak areas was established.

[0059] Step 2) Collect oil test data for each layer within the region, and calculate the corresponding gas chromatographic group nC based on different fluid properties. 20 Summary table of peak area;

[0060] Step 3) Based on nC 20 The peak area of ​​the uncontaminated component W is calculated, and the peak area S of Pr+Ph, which is less affected by the strata, is also obtained.

[0061] Step 4) Summarize the W and S values ​​for different fluid properties and calculate the W / S value;

[0062] Step 5) Create corresponding charts based on W and W / S values ​​to divide different fluid zones;

[0063] Step 6) Repeat steps 3) and 4) for the well to be evaluated, and plot the obtained W and W / S values ​​on the chart of step 5). Determine the fluid properties based on the area where the plotted points are located.

[0064] This invention establishes new parameters to reflect the degree of crude oil alteration and the changes in peak shape after alteration by re-analyzing the component peak parameters. This reduces the subjective differences in human judgment and provides a new method for evaluating formation fluid properties using gas chromatography, improving the interpretation accuracy and enhancing the application level of evaluation logging technology.

[0065] Example 4

[0066] To further illustrate the effects of the present invention, this embodiment takes Well X as an example to evaluate shale oil under oil-based mud.

[0067] The specific process for evaluating the grade of source rocks is as follows:

[0068] Step 1) Extract the pyrolysis parameters S2 and S4 of all analytical samples in the region, and establish a summary table of the area of ​​pyrolysis parameters S2+S4 in the region;

[0069] Step 2) Collect measured TOC values ​​for each stratigraphic level within the region, conduct correlation analysis between TOC and S2+S4 values, and establish a correlation regression equation: TOC=K*(S2+S4)+R, as shown below. Figure 1 As shown, R = 0.0686, K = 0.0928.

[0070] Step 3) Apply the correlation regression equation to obtain the TOC correction data of shale oil reservoirs under oil-based drilling fluid conditions, and obtain the S1 value in shale oil based on the TOC correction data; see Table 1; TOC-S1 distribution map of well X is shown in Table 1. Figure 4 As shown.

[0071] Step 4) Calculate the S2+S1 value to obtain the abundance of source rocks and evaluate the grade of source rocks.

[0072] Table 1. Statistics for calculating TOC and S1

[0073]

[0074] The TOC correction data and measured values ​​correlate well, such as Figure 2 As shown in Table 2, the errors are as follows.

[0075] Table 2 Errors in TOC Measurement and Calculation for Water-Based Slurry

[0076] well deep Calculate TOC (%) Actual TOC (%) deviation(%) 4066 1.14 1.15 1.15 4068 1.53 1.55 1.32 4070 1.67 1.69 1.26 4072 1.60 1.62 1.58 4074 1.45 1.48 1.94 4076 1.72 1.74 1.48 4078 1.85 1.87 1.04 4080 1.64 1.67 1.74 4082 1.88 1.94 3.11 4084 1.74 1.76 0.81 4086 1.68 1.71 1.79 4088 2.09 2.13 2.00 4090 2.07 2.09 1.18 4092 2.14 2.17 1.49 4094 2.22 2.25 1.46 4096 1.59 1.60 0.50 4098 1.63 1.63 0.14 4100 1.95 1.97 1.03

[0077] Based on the oil and gas industry standard (SY / T3735-2019), and using corrected calculated TOC and S1 data, the organic matter abundance of the source rock in Well X under oil-based drilling mud contamination was re-evaluated. Oil-based drilling mud was used in the well from 4300-5200m, causing TOC and S1 contamination. Source rock evaluation was conducted at a random depth of 4335-4354m. Calculated TOC, calculated S1, and S1+S2 were tabulated to obtain the TOC and S1+S2 of Well X. Comparison with the source rock organic matter abundance evaluation standard revealed that the source rock at 4335-4354m is primarily classified as a good source rock.

[0078] The evaluation criteria for the organic matter abundance of source rocks (source rock grade evaluation) are shown in Table 3. The source rock grade evaluation results of Well X are shown in Table 4.

[0079] Table 3 Evaluation Criteria for Organic Matter Abundance in Source Rocks

[0080] Hydrocarbon source rock grade TOC% S1+S2mg / g Non-hydrocarbon source rocks ＜0.5 ＜2 Typical source rocks 0.5～1 2～6 Good source rocks 1～2 6～20 High-quality source rocks ≥2 ≥20

[0081] Table 4 Evaluation of Hydrogen Source Rock Grade in Well X

[0082] well deep TOC% <![CDATA[S1+S2mg / g]]> Hydrocarbon source rock grade 4335 1.82 7.40 Good source rocks 4336 1.24 2.30 Good source rock 4337 1.50 4.87 Good source rock 4338 2.13 7.37 High-quality source rocks 4339 1.59 6.30 Good source rocks 4340 1.84 6.77 Good source rocks 4341 0.99 6.34 Typical source rocks 4342 1.38 6.24 Good source rocks 4343 1.54 8.19 Good source rocks 4344 0.75 4.80 Typical source rocks 4346 1.84 9.34 Good source rocks 4347 1.23 5.81 Good source rocks 4348 0.97 11.66 Typical source rocks 4349 1.79 10.85 Good source rocks 4350 1.17 8.57 Good source rocks 4352 1.77 11.69 Good source rocks 4354 1.80 10.76 Good source rocks

[0083] Fluid property evaluation methods include the following steps:

[0084] Step 1) Extract nC from the gas chromatographic parameters of all analytical samples within the region. 20 Based on the peak areas of the components, a summary table of regional gas chromatographic component peak areas was established.

[0085] Step 2) Collect oil test data from each layer within the region. Based on the principle that changes in component peak area reflect peak shape characteristics, establish a new calculation parameter: the intact peak area of ​​uncontaminated components. Then, calculate the peak area of ​​Pr+Ph, which is less affected by formation. The calculation formula is as follows:

[0086] W = nC 20 +…+nC 28 S = Pr + Ph

[0087] W - Uncontaminated peak area; S - Pr+Ph peak area

[0088] Calculate the corresponding gas chromatography group nC based on different fluid properties. 20 rear peak area;

[0089] (1) Peak areas of components in gas chromatography of oil layer;

[0090] (2) Peak areas of components in aqueous gas chromatography;

[0091] (3) Peak areas of components in dry-layer gas chromatography;

[0092] Step 3) Summarize the W and S values ​​of the oil layer, dry layer, and water layer, and calculate the W / S value: see Table 5 and Table 6;

[0093] Table 5 Summary of W and S Peak Areas

[0094]

[0095] Table 6 W / S Summary Table

[0096]

[0097] Step 4) Create a corresponding chart based on the W and W / S values: W is the horizontal axis, and the vertical axis is the summary table W / S, divided into oil zone, water zone, and dry zone; for example... Figure 3 As shown;

[0098] Step 5) Plot the W values ​​of the wells to be evaluated onto the chart. The data points for the wells to be evaluated are represented by ①...⑩ to determine the formation fluid properties. For example... Figure 5 As shown, the average values ​​of W and W / S in the pyrolysis chromatography of well X at 4349-4354m (layer 2) are projected into the oil layer zone, while the average values ​​of W and W / S in the pyrolysis chromatography of well X at 4335-4338m (layer 5) are projected into the water layer zone.

[0099] Step 6) Interpretation layer verification

[0100] 1. Interpreted layer 1, well interval 4349-4354m, interpreted as an oil layer; oil testing interval 4352-4354m, pumping, daily oil production 5.27t, crude oil density 0.87g / cm³ 3 The viscosity was 26 mPa·s, and the oil test results showed an oil layer, which was consistent with the interpretation results.

[0101] 2. Interpreted as a water-bearing layer, with a well section of 4335-4338m; tested well section 4335-4337m, pumping, daily water production 18.56 m³. 3 The oil test results indicated a water layer, which is consistent with the interpretation results.

[0102] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A method for evaluating shale oil under oil-based drilling mud, characterized in that: The evaluation includes source rock grade assessment and fluid property assessment. The source rock grade assessment establishes a regression equation using pyrolysis data S2 and S4 that are not contaminated by oil-based mud, calculates TOC and S1, and evaluates the source rock grade based on the TOC and S1+S2 values. S1 represents the hydrocarbon content per unit mass of rock detected at 300℃, mainly consisting of liquid hydrocarbon content in mg / g. S2 represents the hydrocarbon content per unit mass of rock detected at 300℃-600℃, mainly in solid form (mg / g). S4 represents the residual organic carbon content per unit mass of rock after pyrolysis, mainly consisting of unpyrolyzable residual organic carbon (mg / g); TOC represents total organic carbon. The fluid properties were evaluated using gas chromatography (NCC) uncontaminated by oil-based mud. 20 By comparing the peak area with the Pr+Ph values ​​from gas chromatography, an indicator chart for oil and water content was established to evaluate the properties of formation fluids contaminated with oil-based mud. Wherein, Pr is pterosaridine; Ph is phytane.

2. The method for evaluating shale oil under oil-based mud according to claim 1, characterized in that: The specific process for evaluating the grade of source rocks is as follows: Step 1) Extract the pyrolysis parameters S2 and S4 of all analytical samples in the region and establish a summary table of the pyrolysis parameter S2+S4 values ​​in the region; Step 2) Collect measured TOC values ​​of each layer in the region, analyze the correlation between TOC values ​​and S2+S4 values, and establish a correlation regression equation; Step 3) Apply the correlation regression equation to obtain the TOC correction data of shale oil reservoir under oil-based drilling fluid conditions, and obtain the value of S1 in shale oil based on the TOC correction data; Step 4) Calculate the S2+S1 value to obtain the abundance of source rocks and evaluate the grade of source rocks.

3. The method for evaluating shale oil under oil-based mud according to claim 1, characterized in that: The specific steps for evaluating fluid properties are as follows: Step 1) Extract uncontaminated nC from the gas chromatographic parameters of all analytical samples within the region. 20 Based on the peak areas of each component, a summary table of regional gas chromatographic component peak areas was established. Step 2) Collect oil test data for each layer within the region, and calculate the corresponding gas chromatographic group nC based on different fluid properties. 20 rear peak area; Step 3) Based on nC 20 The peak area of ​​the uncontaminated component W is calculated, and the peak area S of Pr+Ph, which is less affected by the strata, is also obtained. Step 4) Summarize the W and S values ​​for different fluid properties and calculate the W / S value; Step 5) Create corresponding charts based on W and W / S values ​​to divide different fluid zones; Step 6) Repeat steps 3) and 4) for the well to be evaluated, and plot the obtained W and W / S values ​​on the chart of step 5). Determine the fluid properties based on the area where the plotted points are located.

4. The method for evaluating shale oil under oil-based mud according to claim 2, characterized in that: The correlation regression equation established in step 2) is TOC=K*(S2+S4)+R, where R is the correction value and K is the linear slope.

5. The method for evaluating shale oil under oil-based mud according to claim 2, characterized in that: Step 3) In shale oil, S1 = (TOC - S4 / 10) / 0.083 - S2).

6. The method for evaluating shale oil under oil-based mud according to claim 2, characterized in that: When TOC is less than 0.5% and S1+S2 is less than 2, the source rock is classified as a non-source rock. When TOC is 0.5-1 and S1+S2 is 2-6, the source rock is classified as a general source rock; when TOC is 1-2 and S1+S2 is 6-20, the source rock is classified as a good source rock; when TOC is not less than 2 and S1+S2 is not less than 20, the source rock is classified as a high-quality source rock.

7. The method for evaluating shale oil under oil-based mud according to claim 3, characterized in that: Step 3) The intact peak area W of the uncontaminated component is nC 20 -nC 28 The area and sum of.

8. The method for evaluating shale oil under oil-based mud according to claim 3, characterized in that: Different fluid zones include oil zone, water zone, and dry zone.

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