Method for evaluating dense oil and gas reservoir enriched dessert

Abstract

The invention discloses a dense oil and gas reservoir enriched dessert evaluation method which comprises the following steps: S1, collecting physical property data of a target interval oil and gas reservoir in an evaluation area, collecting a closed coring sample, and collecting oil and gas saturation; s2, performing high-pressure mercury injection analysis on the closed coring sample to obtain a mercury injection capillary pressure curve; s3, reading mercury feeding pressure P, and calculating reservoir forming power F; s4, compiling and drawing a reservoir physical property plane contour map and a reservoir forming power F plane contour map, and overlapping the two; and S5, determining classification standards of oil / gas enriched desserts in combination with oil and gas testing or development and production testing conditions, and circling distribution of oil and gas enriched desserts of different levels in the superimposed graph. According to the method for evaluating the enriched desserts of the tight oil and gas reservoir, the problems that in traditional evaluation of the enriched desserts containing oil and gas, reservoir forming power is evaluated only through desserts with single physical properties or on the basis of hydrocarbon generation intensity of hydrocarbon source rocks, and when the reservoir forming power is estimated through the hydrocarbon generation intensity, numerous parameters are involved, and the evaluation precision is low are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas exploration and development, and relates to a method for evaluating enriched sweet spots in tight oil and gas reservoirs. Background Art

[0002] Tight reservoirs have fine pore throats and strong heterogeneity. Tight oil and gas are distributed over a large area, with low abundance and quasi-continuous distribution. The evaluation of enriched sweet spots in tight oil and gas is an important part of the optimization of favorable targets for tight oil and gas exploration and development, and is also the main technical means to reduce costs and increase efficiency. At present, the evaluation of enriched sweet spots in tight oil and gas mainly focuses on single evaluation of physical property sweet spots in relatively high-quality reservoirs or evaluation of hydrocarbon generation intensity of source rocks based on accumulation dynamics. Among them, physical property sweet spots are based on the hydrocarbon-bearing and accumulation model of relatively high-quality reservoirs, that is, under the same accumulation dynamics, large throats in high-quality reservoirs are relatively developed, the throat radius is relatively thick as a whole, the capillary resistance is small during the accumulation process, the proportion of pore throats that can be filled is high, the hydrocarbon saturation is high, and the hydrocarbon saturation is positively correlated with reservoir physical properties; although the evaluation of hydrocarbon generation intensity of source rocks realizes the important role of accumulation dynamics in the accumulation of tight oil and gas, estimating the accumulation dynamics through the hydrocarbon generation intensity of source rocks involves many parameters such as source rock thickness, organic matter content, and thermal evolution degree, the process is complex, and the credibility of the conclusion is relatively low.

[0003] Hydrocarbon accumulation is the result of the interaction between dynamic and resistance forces. The hydrocarbon-bearing enriched sweet spots in tight oil and gas reservoirs are jointly controlled by the accumulation dynamics and the capillary resistance determined by the microscopic pore structure of the reservoir. The seepage capacity of tight reservoirs is mainly controlled by the size of the throat radius, and permeability is the most intuitive reflection of the microscopic pore structure of the reservoir. Reservoirs with high permeability have relatively thick throat radii as a whole. When hydrocarbons are injected and accumulated, the capillary resistance is small, the injection effect is good, and the hydrocarbon saturation is high. Physical simulation experiments on hydrocarbon accumulation in the same tight reservoir under different displacement pressure differences show that before the minimum irreducible water saturation is exceeded, the hydrocarbon saturation in the tight reservoir continuously increases with the increase of accumulation dynamics, indicating that the accumulation dynamics of hydrocarbons has an important impact on the accumulation and enrichment of tight reservoirs. Traditional evaluation methods for enriched sweet spots in tight oil and gas mostly focus on single evaluation and prediction of physical property sweet spots in reservoirs or hydrocarbon generation intensity of source rocks representing accumulation dynamics. The calculation of hydrocarbon generation intensity requires the use of many parameters such as source rock thickness, area, source rock porosity, average organic carbon content, density, average amount of hydrocarbons already generated per unit mass of organic carbon, and hydrocarbon expulsion coefficient, and the process is relatively complex.

[0004] Exploration and development practices have shown that within the basin, due to differences in source rock type, thickness, thermal evolution degree, etc., the hydrocarbon generation intensity of source rocks varies in different regions. Moreover, controlled by the connectivity of transport systems such as faults - fractures, connected sand bodies, and unconformities, the area with high hydrocarbon generation intensity does not necessarily have the strongest charging power and the best charging effect, and reservoir physical properties also often vary within the basin. That is, the non - uniformity of the planar distribution and the complexity of the spatial combination of hydrocarbon generation intensity of source rocks, reservoir physical properties, and transport systems make it so that high - quality reservoirs, areas with high hydrocarbon generation intensity of source rocks, and efficient transport areas do not necessarily form the optimal combination in space. The area where high - quality reservoirs develop does not necessarily overlap with the area of high hydrocarbon generation intensity in space, and the area with high hydrocarbon generation intensity does not necessarily have the strongest oil - gas charging power, making the evaluation of sweet spots for tight oil and gas enrichment extremely difficult and with poor accuracy. Summary of the Invention

[0005] The object of the present invention is to provide a method for evaluating sweet spots for tight oil and gas reservoir enrichment, which solves the problems of traditional methods that mainly focus on evaluating reservoir physical property sweet spots alone or evaluating hydrocarbon accumulation power based on the hydrocarbon generation intensity of source rocks, and when estimating hydrocarbon accumulation power based on hydrocarbon generation intensity, it involves numerous parameters, has a complex process, and low evaluation accuracy.

[0006] The technical solution adopted by the present invention is that the method for evaluating sweet spots for tight oil and gas reservoir enrichment includes the following steps:

[0007] S1: Collect reservoir physical property data of the target interval of the oil - gas layer in the area to be evaluated, and sealed core samples of the target interval of the oil - gas layer from the sealed coring wells in the area to be evaluated, and collect the oil - gas saturation data of the sealed core samples.

[0008] S2: Conduct high - pressure mercury injection analysis on the sealed core samples to obtain the mercury injection capillary pressure curve.

[0009] S3: Read the mercury injection pressure P on the mercury injection capillary pressure curve, and calculate the corresponding critical throat radius r 临界 and the average hydrocarbon accumulation power F of the target interval of the oil - gas layer of this well.

[0010] S4: According to the reservoir physical property data collected in S1 and the average hydrocarbon accumulation power F data calculated in S3, compile the planar isopach maps of reservoir physical properties and the planar isopach maps of hydrocarbon accumulation power F at different well positions in the area to be evaluated, and superimpose the planar isopach map of hydrocarbon accumulation power F on the planar isopach map of reservoir physical properties.

[0011] S5: Combining the oil - gas testing and development test production situations of the existing wells in the area to be evaluated, determine the classification criteria for Class I and Class II oil / gas enrichment sweet spots in the area to be evaluated, and circle the distribution of different - level oil - gas enrichment sweet spots in the superimposed map obtained in S4 according to the classification criteria.

[0012] The characteristics of the present invention also lie in:

[0013] The physical property data of the reservoir in S1 include porosity and permeability.

[0014] The specific operation of S2 is as follows: Select samples from the sealed coring samples of the target interval at 2 - 3 pieces per layer, conduct high-pressure mercury injection analysis, and encrypt and measure 3 pressure points in the section where the mercury injection saturation is ±20% of the oil / gas saturation during the analysis process to obtain the mercury injection capillary pressure curve of this sample.

[0015] The specific steps to read the mercury injection pressure P in S3 are as follows: Find the mercury injection saturation value equal to the oil / gas saturation of the sealed coring sample on the mercury injection capillary pressure curve, and read the mercury injection pressure value P corresponding to this mercury injection saturation value.

[0016] In S3, calculate its corresponding critical throat radius r respectively according to the Laplace equation 临界 For

[0017]

[0018] In Equation 1, P: mercury injection pressure, unit is MPa; r 临界 : throat radius, unit is m; δ 汞 : interfacial tension of mercury, unit is N / m; θ 汞 : wetting angle between mercury and the reservoir, unit is °;

[0019] Calculate the arithmetic mean of the critical throat radii obtained for the same target interval of the same well,

[0020] According to the Laplace equation, the average accumulation dynamic force F of the oil / gas reservoir in the target interval of this well is

[0021]

[0022] In Equation 2, F: capillary pressure, unit is MPa; r: critical throat radius, unit is m; δ 油 / 气水 : oil / gas / water interfacial tension under reservoir conditions, unit is N / m; θ 油 / 气水 : wetting angle between oil / water and the reservoir, unit is °.

[0023] The method to compile the F plane contour map and the physical property plane contour map of the reservoir in S4 is as follows: According to the data at some known points in the area, use the interpolation method to find the contour points and connect the contour points.

[0024] The physical property plane contour map of the reservoir in S4 is the porosity plane contour map, and the accumulation dynamic force F plane contour map is superimposed on the porosity plane contour map.

[0025] The physical property plane contour map of the reservoir in S4 is the permeability plane contour map, and the accumulation dynamic force F plane contour map is superimposed on the permeability plane contour map.

[0026] Analyze the physical property and accumulation dynamic distribution intervals where known high-yield wells and industrial oil and gas flow wells are located in the analysis area, and determine the classification criteria for Class I sweet spots and Class II sweet spots.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. The sweet spot evaluation method provided by the present invention starts from analyzing the dynamic and resistance of hydrocarbon accumulation, and is based on the key core that the accumulation and enrichment of tight oil and gas are jointly controlled by the accumulation dynamic and the accumulation resistance determined by the microscopic pore structure of the reservoir. The evaluated hydrocarbon-bearing and enriched sweet spots are more accurate.

[0029] 2. The sweet spot evaluation method provided by the present invention fully considers the influence of the conduction system on hydrocarbon accumulation. Starting from the hydrocarbon saturation of the reservoir, which is the result of hydrocarbon accumulation, it is more direct and accurate compared with estimating the accumulation dynamic through hydrocarbon generation intensity.

[0030] 3. The sweet spot evaluation method provided by the present invention draws on the principle of high-pressure mercury injection analysis, calculates the hydrocarbon accumulation dynamic based on the mercury injection capillary pressure curve and hydrocarbon saturation of the sealed core rock samples. Compared with calculating the hydrocarbon generation intensity by statistically analyzing the thickness, organic matter content, thermal evolution degree, hydrocarbon expulsion efficiency, etc. of different types of source rocks and then estimating the accumulation dynamic, it is more convenient and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram for obtaining the critical throat radius in Step S3 of the evaluation method of the present invention;

[0032] Figure 2 It is an isopach map of hydrocarbon accumulation dynamic in Example 1 of the evaluation method of the present invention;

[0033] Figure 3 It is an isopach map of reservoir permeability in Example 1 of the evaluation method of the present invention;

[0034] Figure 4 It is a comprehensive sweet spot evaluation map of the superposition of isopach maps of hydrocarbon accumulation dynamic and reservoir permeability in Example 1 of the evaluation method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0036] A method for evaluating sweet spots in tight oil and gas reservoirs, comprising the following steps:

[0037] S1: Collect the reservoir physical property data of the target interval of the oil and gas reservoir in the area to be evaluated, and the sealed core samples of the target interval of the oil and gas reservoir in the sealed coring wells in the area to be evaluated, and collect the oil and gas saturation data of the sealed core samples; among them, the reservoir physical property data includes porosity and permeability. The collected porosity and permeability data are prepared for compiling the physical property isogram. Generally, there are porosity and permeability data of several samples for the oil and gas reservoir in the target interval of each well. Here, the average porosity and average permeability values are used to represent the porosity and permeability of this well location.

[0038] S2: Conduct high-pressure mercury injection analysis on the sealed core samples to obtain the mercury injection capillary pressure curve, as Figure 1 shown. The specific operation steps are as follows: Select samples from the sealed core samples of the target interval at 2 - 3 pieces per layer for high-pressure mercury injection analysis; during the analysis process, encrypt and measure 3 pressure points in the section where the mercury injection saturation is ±20% of the mercury injection saturation equal to the oil / gas saturation to obtain the mercury injection capillary pressure curve of this sample.

[0039] The process of high-pressure mercury injection analysis experiment is similar to the process of oil and gas charging and reservoir formation, both of which are non-wetting phases entering the micro pore throats of the wetting phase reservoir, and preferentially enter the large pore throats under the action of the displacement pressure, and then enter the next-level small pore throats in turn as the pressure increases.

[0040] The mercury injection capillary pressure curve is the relationship curve between the mercury injection pressure and the mercury injection saturation. A certain mercury injection pressure uniquely corresponds to a specific throat radius. At a certain mercury injection pressure, the volume of mercury entering the rock is equal to the sum of the volumes of the pores connected by the throats with a radius greater than or equal to the critical radius corresponding to this pressure. The mercury injection saturation at this pressure is the percentage of the pore volume connected by the throats with a radius greater than or equal to the critical radius in the total pore volume.

[0041] S3: Read the mercury injection pressure P on the mercury injection capillary pressure curve. It should be noted that: find the mercury injection pressure P corresponding to the mercury injection saturation equal to the oil and gas saturation of this sealed core sample on the capillary pressure curve. The oil and gas saturation of the sealed core sample is the true oil and gas saturation of the oil and gas reservoir. The mercury injection saturation corresponding to the oil and gas saturation on the capillary pressure curve of the sealed core sample corresponds to a specific capillary pressure, and this capillary pressure corresponds to a specific critical throat radius through the Laplace equation. The size of this critical throat radius r 临界 reflects the size of the oil and gas reservoir formation power F.

[0042] Calculate its corresponding critical throat radius r 临界 and the average reservoir formation power F of the oil and gas reservoir in the target interval of this well. The specific calculation method is as follows: Calculate its corresponding critical throat radius r 临界 as Equation 1,

[0043]

[0044] Note here: The average critical throat radius r needs to be calculated for the same target layer of the same well. In Equation 1, P is the mercury injection pressure in MPa; r 临界 : The throat radius in m; δ 汞 : The interfacial tension of mercury under experimental conditions in N / m; θ 汞 : The wetting angle between mercury and the reservoir in °.

[0045] According to the Laplace equation, the average hydrocarbon accumulation dynamic force F for the target layer section of the well is

[0046]

[0047] In Equation 2: F is the capillary pressure in MPa; r is the critical throat radius in m; δ 油 / 气水 : The oil / gas-water interfacial tension under hydrocarbon reservoir conditions in N / m; θ 油 / 气水 : The wetting angle between oil / water and the reservoir in °.

[0048] S4: Based on the reservoir physical property data collected in S1 and the average hydrocarbon accumulation dynamic force F data calculated in S3, compile the reservoir physical property plane isopach maps and the hydrocarbon accumulation dynamic force F plane isopach maps for different well positions in the area to be evaluated. Then, overlay the hydrocarbon accumulation dynamic force F plane isopach map with the reservoir physical property plane isopach map. The compilation method is as follows: Based on the data at some points, use interpolation to find the isopoints and connect them. Among them, the reservoir physical property plane isopach map includes the porosity plane isopach map and the permeability plane isopach map. The hydrocarbon accumulation dynamic force F plane isopach map can be overlaid with the porosity plane isopach map or the permeability plane isopach map.

[0049] S5: Combine the oil / gas test production and the development test production situation to determine the classification criteria for Class I and Class II oil / gas-rich sweet spots. Based on the classification criteria, obtain the distribution of oil / gas-rich sweet spots in the overlay map. The specific process is to analyze the physical property and hydrocarbon accumulation dynamic force distribution intervals where the known high-yield wells and industrial oil / gas flow wells are located in the area to be evaluated, and determine the classification criteria for Class I sweet spots (high-yield wells) and Class II sweet spots (industrial oil / gas flow). For example, a well with a single-well gas test open flow potential greater than 100,000 m³ / day is defined as a Class I sweet spot, with a hydrocarbon accumulation dynamic force distribution interval of >0.5 MPa, a porosity distribution interval of >10%, and a permeability distribution interval of >0.7 mD; a well with a single-well gas test open flow potential of 4 - 100,000 m³ / day is defined as a Class II sweet spot, with a hydrocarbon accumulation dynamic force distribution interval of >0.3 MPa, a porosity distribution interval of >7%, and a permeability distribution interval of >0.5 mD.

[0050] The method for evaluating enriched sweet spots in tight oil and gas reservoirs provided by the present invention only requires data such as porosity, permeability of the reservoir in the target interval of existing wells in the evaluation area, and gas saturation of the sealed coring wells, and collecting some sealed coring samples for high-pressure mercury injection analysis. These data and analytical tests are easy to measure / obtain, the method is simple, fast, and has high accuracy.

[0051] Example 1

[0052] The method for evaluating enriched sweet spots in tight gas reservoirs includes the following steps:

[0053] S1: Collect the reservoir physical property data of the gas-bearing layer in the target interval in the selected sweet spot evaluation area, and the sealed coring samples of the gas-bearing layer in the target interval of the sealed coring wells in the evaluation area, and collect the gas saturation data of the collected sealed coring samples;

[0054] S2: Conduct high-pressure mercury injection analysis and testing on the sealed coring samples to obtain the mercury injection capillary pressure curve;

[0055] S3: According to the method for calculating the hydrocarbon accumulation dynamics, as Figure 1 shown, calculate the hydrocarbon accumulation dynamics. For a well with multiple samples, the average value is used. The results are shown in Table 1:

[0056] Table 1 Hydrocarbon accumulation dynamics calculation process table

[0057]

[0058] Under laboratory conditions (one atmosphere, 20 °C), δ 汞 takes the value of 0.48 N / m, θ 汞 takes the value of 146°; under gas reservoir conditions (3000 m, 110 °C), δ 气-水 takes the value of 0.030 N / m, for a strongly water-wet reservoir, θ 储-水 takes the value of 0°.

[0059] S4: According to the reservoir physical property data collected in S1 and the average hydrocarbon accumulation dynamics F data calculated in S3, compile the physical property contour map and hydrocarbon accumulation dynamics contour map of the sweet spot evaluation area, as Figure 2 shown; compile the porosity contour map and permeability contour map of the target interval in the study area. In this example, since the reservoir fractures in the evaluation area are not well developed and it is a single pore type reservoir, and porosity is positively correlated with permeability, only the permeability contour map needs to be compiled, as Figure 3 shown, and superimpose the hydrocarbon accumulation dynamics contour map and the permeability contour map, as Figure 4 shown;

[0060] S5: Combine the single well gas testing conditions in the evaluation area to determine the classification criteria for Class I and Class II gas-bearing enriched sweet spots, as shown in Table 2:

[0061] Table 2 Sweet spot classification criteria for the evaluation area

[0062]

[0063] Calibrate the distribution of gas-bearing enrichment zones and sweet spots in the evaluation area on the overlay map in combination with the classification criteria, such as Figure 4 shown.

[0064] Example 2

[0065] A method for evaluating enriched sweet spots in tight oil and gas reservoirs, comprising the following steps:

[0066] S1: Collect the reservoir physical property data of the oil and gas layers in the target interval in the selected sweet spot evaluation area, and the sealed coring samples of the oil and gas layers in the target interval of the sealed coring wells in the evaluation area, and collect the oil and gas saturation data of the selected sealed coring samples;

[0067] S2: Conduct high-pressure mercury injection analysis on the sealed coring samples to obtain the mercury injection capillary pressure curve;

[0068] S3: Read the mercury injection pressure P on the capillary pressure curve, and calculate its corresponding critical throat radius r 临界 and the average accumulation dynamic force F of the oil and gas layers in the target interval of this well;

[0069] S4: According to the reservoir physical property data collected in S1 and the average accumulation dynamic force F data calculated in S3, compile the reservoir physical property plane contour map and the accumulation dynamic force F plane contour map of different well positions in the evaluation area, and overlay the accumulation dynamic force F plane contour map with the reservoir physical property plane contour map;

[0070] S5: Combine the development and production test situation, determine the classification criteria for Class I and Class II oil / gas enrichment sweet spots, and circle the distribution of oil and gas enrichment sweet spots at different levels in the overlay map obtained in S4 according to the classification criteria.

[0071] Example 3

[0072] A method for evaluating enriched sweet spots in tight oil and gas reservoirs, comprising the following steps:

[0073] S1: Collect the reservoir physical property data of the oil and gas layers in the target interval in the selected sweet spot evaluation area, and the sealed coring samples of the oil and gas layers in the target interval of the sealed coring wells in the evaluation area, and collect the oil and gas saturation data of the selected sealed coring samples.

[0074] S2: Conduct high-pressure mercury injection analysis on the sealed coring samples to obtain the mercury injection capillary pressure curve. The specific operation steps are as follows: Select samples from the sealed coring samples of the target interval at 2-3 pieces / layer for high-pressure mercury injection analysis; During the analysis process, encrypt and measure 3 pressure points in the section of the mercury injection saturation equal to the oil / gas saturation ±20%, and obtain the capillary pressure curve of this sample.

[0075] The process of high-pressure mercury injection analysis is similar to the process of hydrocarbon charging and reservoir formation. In both processes, the non-wetting phase enters the micro-pore throats of the wetting-phase reservoir, and under the action of the displacement pressure, it preferentially enters the large pore throats and then enters the next-level small pore throats in turn as the pressure increases.

[0076] The mercury injection capillary pressure curve is the relationship curve between the mercury injection pressure and the mercury injection saturation. A certain mercury injection pressure uniquely corresponds to a specific throat radius. At a certain mercury injection pressure, the volume of mercury entering the rock is equal to the sum of the volumes of the pores connected by the throats with a radius greater than or equal to the critical radius corresponding to this pressure. The mercury injection saturation at this pressure is the percentage of the pore volume connected by the throats with a radius greater than or equal to the critical radius in the total pore volume.

[0077] S3: Read the mercury injection pressure P on the mercury injection capillary pressure curve and calculate the corresponding critical throat radius r 临界 and the average reservoir formation driving force F of the target interval of the oil and gas reservoir in this well.

[0078] S4: According to the reservoir physical property data collected in S1 and the average reservoir formation driving force F data calculated in S3, compile the plane isopach maps of the reservoir formation driving force F, the reservoir porosity, and the reservoir permeability at different well positions in the evaluation area, and superimpose the plane isopach map of the reservoir formation driving force F with the plane isopach map of the reservoir porosity or the reservoir permeability respectively.

[0079] S5: Combine the oil / gas testing results and the development test production situation to determine the classification criteria for Class I and Class II oil / gas enrichment sweet spots. Combine the classification criteria to obtain the distribution of oil / gas enrichment sweet spots in the superimposed map.

[0080] Example 4

[0081] A method for evaluating the enrichment sweet spots of tight oil and gas reservoirs, comprising the following steps:

[0082] S1: Collect the reservoir physical property data of the target interval of the oil and gas reservoir in the selected sweet spot evaluation area, and the sealed core samples of the target interval of the oil and gas reservoir in the sealed coring wells in the evaluation area, and collect the oil and gas saturation data of the collected sealed core samples.

[0083] S2: Conduct high-pressure mercury injection analysis on the sealed core samples to obtain the mercury injection capillary pressure curve.

[0084] S3: Read the mercury injection pressure P on the mercury injection capillary pressure curve. It should be noted that: find the mercury injection pressure P corresponding to the mercury injection saturation equal to the oil and gas saturation of this sealed core sample on the capillary pressure curve, and calculate the corresponding critical throat radius r 临界 and the average reservoir formation driving force F of the target interval of the oil and gas reservoir in this well. The specific calculation method is:

[0085] Calculate the corresponding critical throat radius r respectively according to the Laplace equation临界 , calculate the arithmetic mean of the critical throat radii obtained for the same target formation in the same well.

[0086]

[0087] In Equation 1, P: mercury injection pressure, unit is MPa; r 临界 : throat radius, unit is m; δ 汞 : interfacial tension of mercury under experimental conditions, unit is N / m; θ 汞 : wetting angle between mercury and reservoir, unit is °.

[0088] Based on Laplace's equation, the average hydrocarbon accumulation dynamic force F of the target formation section of the well is

[0089]

[0090] In Equation 2, F: capillary pressure, unit is MPa; r: critical throat radius, unit is m; δ 油 / 气水 : oil / gas-water interfacial tension under reservoir conditions, unit is N / m; θ 油 / 气水 : wetting angle between oil / water and reservoir, unit is °.

[0091] S4: Based on the reservoir physical property data collected in S1 and the average hydrocarbon accumulation dynamic force F data calculated in S3, compile the plane isopach maps of the hydrocarbon accumulation dynamic force F, reservoir porosity, and reservoir permeability at different well positions in the evaluation area, and superimpose the plane isopach map of the hydrocarbon accumulation dynamic force F with the plane isopach map of reservoir porosity or reservoir permeability respectively.

[0092] S5: Combining the results of well testing / gas testing and the development test production situation, determine the classification criteria for Class I and Class II oil / gas enrichment sweet spots, and obtain the distribution of oil / gas enrichment sweet spots in the superimposed map in combination with the classification criteria.

Claims

1. A method for evaluating sweet spots in tight oil and gas reservoirs, characterized in that: The following steps are involved: S1: Collect reservoir physical property data of the oil and gas layers in the target layer section of the evaluation area, and collect closed coring samples of the oil and gas layers in the target layer section of the closed coring well in the evaluation area, and collect oil and gas saturation data of the closed coring samples; S2: performing high-pressure mercury injection analysis on the sealed core sample to obtain a mercury injection capillary pressure curve; S3: Read the mercury inlet pressure P on the mercury inlet capillary pressure curve and calculate the corresponding critical throat radius r 临界 and the average reservoir-forming power F of the oil and gas layer in the target layer of the well; S4: based on the reservoir physical property data collected by S1 and the average reservoir-forming power F data calculated by S3, compile and draw the reservoir physical property plane contour map and the reservoir-forming power F plane contour map of different well locations in the area to be evaluated, and superimpose the reservoir-forming power F plane contour map with the reservoir physical property plane contour map; S5: Based on the oil and gas test results and development and trial production results of existing wells in the area to be evaluated, determine the classification standards for Class I and Class II oil / gas enrichment sweet spots in the area to be evaluated, and circle the distribution of oil and gas enrichment sweet spots of different levels in the superposition map obtained in S4 according to the classification standards.

2. The method for evaluating the sweet spot of tight oil and gas reservoir enrichment according to claim 1, characterized in that: The reservoir physical property data in S1 include porosity and permeability.

3. The method for evaluating the sweet spot of tight oil and gas reservoir enrichment according to claim 1, characterized in that: The specific operation of S2 is: 2 to 3 pieces / layer of closed core samples of the target layer are selected to carry out high-pressure mercury injection analysis. During the analysis, three pressure points are densely measured in the mercury injection saturation ±20% section equal to the oil / gas saturation to obtain the mercury injection capillary pressure curve of the sample.

4. The method for evaluating the sweet spot of tight oil and gas reservoir enrichment according to claim 1, characterized in that: The specific steps of reading the mercury injection pressure P in S3 are: finding a mercury injection saturation value equal to the oil and gas saturation of the closed coring sample on the mercury injection capillary pressure curve, and reading the mercury injection pressure value P corresponding to the mercury injection saturation value.

5. The method for evaluating the sweet spot of tight oil and gas reservoir enrichment according to claim 1, characterized in that: In S3, the corresponding critical throat radius r is calculated according to the Laplace equation. 临界 for In formula 1, P is the mercury inlet pressure, in MPa; r 临界 : throat radius, in m; δ 汞 :Interfacial tension of mercury, in N / m; θ 汞 : the wetting angle between mercury and the reservoir, in degrees; The arithmetic mean of the critical throat radius obtained for the same target layer in the same well is calculated. According to the Laplace equation, the average reservoir-forming power F of the target layer of the well is obtained as In formula 2, F: capillary pressure, unit is MPa; r: critical throat radius, in m; δ 油 / 气水 : Oil / gas-water interfacial tension under reservoir conditions, in N / m; θ 油 / 气水 : The wetting angle between oil / water and reservoir, in degrees.

6. The method for evaluating the sweet spot of tight oil and gas reservoir enrichment according to claim 1, characterized in that: The method for compiling the F plane contour map and the reservoir physical property plane contour map in S4 is: according to the data at some known points in the area, the equivalent points are obtained by interpolation and connected.

7. The method for evaluating the sweet spot of tight oil and gas reservoir enrichment according to claim 1, characterized in that: The plane contour map of reservoir physical properties in S4 is a plane contour map of porosity, and the plane contour map of reservoir-forming dynamics F is superimposed on the plane contour map of porosity.

8. The method for evaluating the sweet spot of tight oil and gas reservoir enrichment according to claim 1, characterized in that: The plane contour map of reservoir physical properties in S4 is a plane contour map of permeability, and the plane contour map of reservoir-forming dynamics F is superimposed on the plane contour map of permeability.

9. The method for evaluating the sweet spot of tight oil and gas reservoir enrichment according to claim 1, characterized in that: The physical properties and reservoir-forming dynamics distribution ranges of known high-yield wells and industrial oil and gas flow wells in the analysis area are determined to determine the classification standards for Class I and Class II sweet spots.

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