Volcanic rock matrix-fracture dual medium type reservoir reservoir evaluation method and system

Abstract

The application provides a volcanic rock matrix-fracture double medium type oil reservoir evaluation method and system, and belongs to the technical field of geological engineering, oil reservoir technology and well logging interpretation.The application establishes a matrix porosity calculation chart by core calibration logging, adds a fracture pore as a conductive channel in an Archie sandstone conductive model, deduces fracture porosity, and finally combines the matrix pore, the fracture pore, the oil saturation and the oil test result to form a matrix-fracture type double medium oil and gas reservoir quantitative identification method.The application fills the gap of the research on the matrix and the fracture at the same time, improves the oil reservoir identification precision, and is more strict and reasonable in the identification standard, and is high in reliability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geological engineering, oil reservoir technology and well logging interpretation, and particularly relates to a volcanic rock matrix-fracture double medium type oil reservoir evaluation method and system. BACKGROUND

[0002] The matrix-fracture double medium oil and gas reservoir is widely distributed, has strong heterogeneity, complex pore structure, poor oil reservoir discrimination accuracy, unclear reservoir controlling factors and many other problems which need to be further researched and solved.

[0003] For the matrix-fracture double medium oil and gas reservoir, the matrix oil reservoir and the fracture oil reservoir are currently researched respectively, the conventional well logging interpretation of the existing volcanic rock reservoir matrix oil reservoir adopts the core calibration logging technology to obtain the matrix porosity, and then the matrix oil saturation is calculated based on the Archie formula, and finally the oil reservoir chart is established based on the lithology to form the matrix oil reservoir discrimination method; for the fracture oil reservoir, the fracture porosity is calculated by using the empirical formula, and then the fracture oil reservoir and the fracture saturation are determined based on the empirical formula, and currently there is no method for the unified research of the matrix oil reservoir and the fracture oil reservoir. SUMMARY

[0004] To solve the above technical problems, the application provides a volcanic rock matrix-fracture double medium type oil reservoir evaluation method, which comprises the following steps:

[0005] (1) determining the oil reservoir geological characteristics, reservoir characteristics and oil reservoir distribution characteristics of a to-be-researched area, and clarifying the relationship between the lithology and the oiliness;

[0006] (2) judging the reservoir type of the to-be-researched area through data synthesis, and clarifying the fracture distribution characteristics;

[0007] (3) using the core analysis data, adopting the core calibration logging technology to determine the matrix porosity of the to-be-researched area;

[0008] (4) for the characteristics of the volcanic rock matrix-fracture double medium oil and gas reservoir, adding the fracture pore conductive channel in the pore conductive channel of the Archie sandstone conductive model, considering that the volcanic rock matrix-fracture type oil reservoir is the parallel conductive result of the matrix pore and the fracture pore, and deducing the fracture porosity of the matrix-fracture type oil reservoir;

[0009] (5) using the saturation calculation model of the matrix-fracture type reservoir to interpret the to-be-researched area reservoir, and obtaining the oil saturation of the matrix-fracture type reservoir;

[0010] (6) Take the calculated matrix porosity, fracture porosity and oil saturation of the reaction section of the reservoir as independent variables, take the two groups of test results of the oil layer and dry layer which have been verified by the oil test as dependent variables, through the discriminant analysis of mathematical statistics, the multi-dimensional independent variables are reduced to form new variables, the new variables make the inter-group mean difference of the two groups of dependent variables reach the maximum, and the sum of squares of the points in the group reach the minimum, so as to establish the discriminant equation of the oil layer of the matrix-fracture type reservoir.

[0011] Preferably, in step (4), when it is a volcanic rock matrix-fracture type dual medium oil and gas reservoir, a composite system composed of matrix pores and fracture pores is formed, and the conductive model thereof is:

[0012] (1)

[0013] In the formula,

[0014] Rm is the resistivity of the composite system when saturated with 100% water, Ω•m;

[0015] Rw is the resistivity of the formation water, Ω•m;

[0016] φf is the ratio of the fracture porosity in the fracture part to the total porosity of the composite system;

[0017] φt is the total porosity of the composite system;

[0018] Rm is the resistivity of the matrix system when saturated with 100% water, Ω•m;

[0019] The fracture porosity φf can be obtained as follows: (2)

[0020] In the formula, φm is the matrix porosity.

[0021] Preferably, only the matrix exists, and the matrix part satisfies the following formula:

[0022] (3)

[0023] For the composite system of matrix pores and fracture pores, the following formula is satisfied:

[0024] (4)

[0025] Substitute formula (3) and (4) into formula (1) to obtain:

[0026] (5)

[0027] Substituting equation (5) into equation (2), we obtain the formula for calculating crack porosity as follows:

[0028] (6)

[0029] In the formula,

[0030] For matrix porosity;

[0031] The cementation index of the matrix portion;

[0032] This refers to stratigraphic factors within the matrix.

[0033] The bonding index of the composite system;

[0034] For the stratigraphic factors of the complex system.

[0035] Preferably, the cementation index m of the matrix portion b The value is generally between 1.5 and 3.

[0036] Preferably, the cementation index of the matrix is ​​determined based on the porosity characteristics of the area under study. The value represents the cementation index of the matrix portion. Substituting the value into equation (6), we obtain the cementation index in the current matrix portion. Under different crack porosity conditions, the relationship between matrix porosity and the cementation index of the composite system. A relationship diagram is generated, and the crack porosity is calculated by computer interpolation based on this relationship diagram.

[0037] Preferably, the bonding index of the composite system The following method can be used to obtain it:

[0038] The resistivity measured in the flushed zone is approximated as the resistivity of the composite rock system, and is derived from Archie's formula for the flushed zone:

[0039] (7);

[0040] In the formula,

[0041] The resistivity of the mud filtrate is given in Ω•m.

[0042] 'a' is the lithology coefficient in Archie's formula;

[0043] The resistivity, measured in Ω•m, is for the rinsing belt.

[0044] Preferably, in step (3), the relationship between the total porosity of the experimental matrix and the acoustic travel time Δt is established by core orientation correction of the core sample taken from the area under study. t Preferably, the total porosity of the experimental matrix is corrected by the following relationship: .

[0045] Preferably, the determination of the laboratory porosity is by pyrolysis, and the following relationship between the extraction method and the pyrolysis porosity is used: .

[0046] Preferably, in step (5), the saturation interpretation uses the saturation equation for horizontal fracture-pore type reservoirs:

[0047] (8);

[0048] wherein,

[0049] is the oil saturation of the matrix part, %;

[0050] is the saturation exponent of the matrix part;

[0051] is the measured resistivity, Ω•m;

[0052] is the matrix porosity;

[0053] is the fracture porosity;

[0054] is the water saturation of the matrix part, %;

[0055] a, b are the lithology coefficients in the Archie formula;

[0056] , are the cementation exponent of the fracture part and the cementation exponent of the matrix part, respectively;

[0057] is the formation water resistivity, Ω•m;

[0058] is the mud filtrate resistivity, Ω•m;

[0059] is the fracture correction factor.

[0060] Preferably, step (6) comprises the following steps:

[0061] ​​​Step (61), in the known oil layer, dry layer data of the test, introduce the calculated fracture porosity, matrix porosity and oil saturation;

[0062] Step (62), the weight of fracture porosity, matrix porosity and oil saturation to the response of oil layer and dry layer is obtained by discriminant analysis of mathematical statistics;

[0063] Step (63), according to the weight of fracture porosity, matrix porosity and oil saturation to the response of oil layer and dry layer, the discriminant function composed of fracture porosity, matrix porosity and oil saturation is obtained, and the discriminant value of discriminant function is combined with fracture porosity to form oil layer and dry layer discriminant chart, the horizontal coordinate of oil layer and dry layer discriminant chart is the discriminant value Y of discriminant function, and the vertical coordinate is fracture porosity;

[0064] Step (64), by reading the oil layer and dry layer discriminant chart, when the interpretation section meets , at the same time, the interpretation section is considered as oil layer section, otherwise, the interpretation section is considered as dry layer section, and the final discrimination of matrix-fracture type reservoir in the area to be studied is formed, is fracture porosity.

[0065] Preferably, the discriminant function is wherein, is matrix porosity, is oil saturation of matrix part.

[0066] Preferably, the reservoir geological characteristics include structural and stratigraphic characteristics, lithological and lithofacies characteristics.

[0067] The application also provides a volcanic rock matrix-fracture double medium type reservoir oil layer evaluation system, comprising a processor, the processor can execute a computer program, and the computer program can realize the volcanic rock matrix-fracture double medium type reservoir oil layer evaluation method.

[0068] Compared with the prior art, the application has at least the following beneficial effects:

[0069] (1) Based on the comprehensive utilization of coring, thin section identification, logging cutting lithological indication data and the like to determine the rock type, the matrix porosity calculation chart is established through core calibration logging, the fracture porosity is derived by adding the fracture porosity as the conductive channel in the Archie sandstone conductive model, and finally the matrix porosity, fracture porosity, oil saturation and oil test results are combined to form the matrix-fracture type double medium oil and gas reservoir oil layer quantitative discrimination method.

[0070] (2) Using this invention to evaluate volcanic matrix-fracture dual-medium oil and gas reservoirs can provide a theoretical basis for the analysis of the formation mechanism of Carboniferous matrix-fracture dual-medium oil and gas reservoirs, the selection of perforated well sections during development, and the identification of Carboniferous fluid properties, thereby improving the development effect of volcanic matrix-fracture reservoirs.

[0071] (3) The theoretical derivation system of this invention is complete and highly versatile. It improves the existing evaluation process of volcanic matrix-fracture type oil and gas reservoirs, where the matrix oil layer and fracture oil layer are completely separated and interpreted separately, which may eventually lead to an overestimation of the reservoir's reserves and discrepancies between the oil layer interpretation results and the actual production situation. This invention achieves unified identification of matrix oil layer and fracture oil layer, which is more in line with the reservoir characteristics of volcanic matrix-fracture type dual-medium oil and gas reservoirs. It can promote the exploration, evaluation and development of similar reservoirs and has broad application space and development prospects. Attached Figure Description

[0072] Figure 1 This is a diagram showing the relationship between acoustic time difference and porosity in the area under study, according to an embodiment of the present invention.

[0073] Figure 2 This is a physical model of a matrix-fracture type hydrous pure rock according to an embodiment of the present invention;

[0074] Figure 3 This is an embodiment of the present invention, showing the equivalent resistance model of current passing through matrix-fracture type hydrous pure rock;

[0075] Figure 4 This is one embodiment of the present invention. Chart for calculating crack porosity at 2.25;

[0076] Figure 5 This is a discriminant chart for fractured reservoirs in the study area according to an embodiment of the present invention;

[0077] Figure 6 This is an interpretation result diagram of a single well in a certain well area according to an embodiment of the present invention;

[0078] Figure 7 This is a flowchart of an evaluation method for oil reservoirs in a volcanic matrix-fracture dual-medium type according to an embodiment of the present invention. Detailed Implementation

[0079] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0080] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0081] In order to better understand the objects, structure and functions of the present application, the following will further describe the present application with reference to the drawings.

[0082] As shown in Figure 7 , the present application provides a volcanic rock matrix-fracture double medium type oil reservoir evaluation method, comprising the following steps:

[0083] (1) determining the geological characteristics, reservoir characteristics and oil layer distribution characteristics of the to-be-studied area, and clarifying the relationship between lithology and oiliness;

[0084] (2) judging the reservoir type of the to-be-studied area through data synthesis, and clarifying the fracture distribution characteristics;

[0085] (3) using core analysis data, adopting core calibration logging technology, and determining the matrix porosity of the to-be-studied area;

[0086] (4) according to the characteristics of the volcanic rock matrix-fracture double medium oil and gas reservoir, adding a fracture pore conductive channel in the pore conductive channel of the Archie sandstone conductive model, considering that the volcanic rock matrix-fracture type oil reservoir is the result of parallel conductive of matrix pores and fracture pores, and deducing the fracture porosity of the matrix-fracture type oil layer; as shown in Figures 2-3 ;

[0087] (5) using the saturation calculation model of the matrix-fracture type reservoir to interpret the reservoir of the to-be-studied area, and calculating the oil saturation of the matrix-fracture type reservoir;

[0088] (6) Take the calculated matrix porosity, fracture porosity and oil saturation of the reaction section of the reservoir as independent variables, take the two groups of oil testing results of the oil layer and dry layer which have been verified by oil testing as dependent variables, through discriminant analysis of mathematical statistics, the multi-dimensional independent variables are reduced to form new variables, the new variables make the mean difference between the two groups of dependent variables of oil layer and dry layer reach the maximum, and the sum of squares of variances of each point in the group reaches the minimum, so as to establish the discriminant equation of the oil layer of the matrix-fracture type reservoir.

[0089] According to one specific embodiment of the present application, in step (4), when it is a volcanic rock matrix-fracture type dual medium oil and gas reservoir, a composite system composed of matrix pores and fracture pores is formed, and the conductive model thereof is:

[0090] (1)

[0091] In the formula,

[0092] is the resistivity of the composite system when saturated with 100% water, Ω•m;

[0093] is the resistivity of the formation water, Ω•m;

[0094] is the ratio of the fracture porosity in the fracture part to the total porosity of the composite system;

[0095] is the total porosity of the composite system;

[0096] is the resistivity of the matrix system when saturated with 100% water, Ω•m;

[0097] The fracture porosity can be obtained as (2);

[0098] wherein, is the matrix porosity.

[0099] According to one specific embodiment of the present application, only the matrix exists, and the matrix part satisfies the following formula:

[0100] (3)

[0101] For the composite system of matrix pores and fracture pores, the following formula is satisfied:

[0102] (4)

[0103] Substitute formula (3) and (4) into formula (1) to obtain:

[0104] (5)

[0105] Substituting equation (5) into equation (2), we obtain the formula for calculating crack porosity as follows:

[0106] (6)

[0107] In the formula,

[0108] For matrix porosity;

[0109] The cementation index of the matrix portion;

[0110] This refers to stratigraphic factors within the matrix.

[0111] The bonding index of the composite system;

[0112] For the stratigraphic factors of the complex system.

[0113] According to a specific embodiment of the present invention, the bonding index of the matrix portion The value is generally between 1.5 and 3.

[0114] According to a specific embodiment of the present invention, the cementation index of the matrix portion is determined based on the porosity characteristics of the area under study. The value represents the cementation index of the matrix portion. Substituting the value into equation (6), we obtain the cementation index in the current matrix portion. Under different crack porosity conditions, the relationship between matrix porosity and the cementation index of the composite system. A relationship diagram is generated, and the crack porosity is calculated by computer interpolation based on this relationship diagram.

[0115] According to a specific embodiment of the present invention, the bonding index m of the composite system is obtained by the following method:

[0116] The resistivity measured in the flushed zone is approximated as the resistivity of the composite rock system, and is derived from Archie's formula for the flushed zone:

[0117] (7);

[0118] In the formula,

[0119] The resistivity of the mud filtrate is given in Ω•m.

[0120] 'a' is the lithology coefficient in Archie's formula;

[0121] The resistivity, measured in Ω•m, is for the rinsing belt.

[0122] According to one specific embodiment of the present application, in step (3), the relationship between the total porosity of the experimental matrix and the acoustic travel time Δt of the well logging is established by core homing correction on the core sample of the area to be studied. t

[0123] According to one specific embodiment of the present application, considering that the determination of the laboratory porosity adopts the pyrolysis method, the following relationship between the extraction method and the pyrolysis method porosity is used: The matrix porosity φm is obtained by correcting the total porosity of the experimental matrix φexp. Considering that the determination of the laboratory porosity adopts the pyrolysis method, the porosity of the rock sample is now generally measured by the extraction method, and it is considered that the extraction method is more accurate, so correction is needed.

[0124] According to one specific embodiment of the present application, in step (5), the saturation interpretation adopts the saturation equation of the horizontal fracture-pore type reservoir:

[0125] (8);

[0126] In the formula,

[0127] is the oil saturation of the matrix part, %;

[0128] is the saturation index of the matrix part;

[0129] is the logging measured resistivity, Ω•m;

[0130] is the matrix porosity;

[0131] is the fracture porosity;

[0132] is the water saturation of the matrix part, %;

[0133] a, b are the lithology coefficients in the Archie formula;

[0134] , are the cementation index of the fracture part and the cementation index of the matrix part, respectively;

[0135] is the formation water resistivity, Ω•m;

[0136] is the mud filtrate resistivity, Ω•m;​​​​​

[0137] is the fracture porosity.

[0138] According to one specific embodiment of the present application, step (6) specifically comprises the following steps:

[0139] Step (61), introducing the calculated fracture porosity, matrix porosity and oil saturation in the known oil layer, dry layer data of the test;

[0140] Step (62), obtaining the weight of the fracture porosity, matrix porosity and oil saturation on the response of oil layer and dry layer through discriminant analysis of mathematical statistics;

[0141] Step (63), obtaining a discriminant function composed of fracture porosity, matrix porosity and oil saturation according to the weight of fracture porosity, matrix porosity and oil saturation on the response of oil layer and dry layer, and forming an oil layer and dry layer discrimination chart by combining the discriminant value of the discriminant function with the fracture porosity; the positive rate can be further improved after adding the fracture porosity, and the fracture porosity can also be considered to be removed as a non-reservoir when it does not meet the condition.

[0142] Step (64), reading the oil layer and dry layer discrimination chart, and considering the interpretation section as an oil layer section when the interpretation section simultaneously meets , otherwise considering the interpretation section as a dry layer section to form the final discrimination of the matrix-fracture type reservoir in the area to be studied. is the fracture porosity.

[0143] According to one specific embodiment of the present application, the discriminant function is wherein, is the matrix porosity, is the oil saturation of the matrix part.

[0144] According to one specific embodiment of the present application, in step (62), the fisher discriminant method is specifically used, the fracture porosity, matrix porosity and oil saturation values (oil and dry layer data points of the wells that have been tested in the reservoir) corresponding to each point of the oil layer section and the dry layer section are extracted, mathematical statistical discriminant analysis is performed, multi-dimensional variables are reduced to form a discriminant function, i.e. a new variable Y, and the new variable makes the difference between the group means of the oil and dry layer two groups of variables reach the maximum, and the sum of squares of the variances of each point in the group reaches the minimum.

[0145] According to one specific embodiment of the present application, in step (62), the oil and dry layer data points of 5 wells that have been tested in the reservoir are used, of which 169 data points belong to the oil layer and 137 data points belong to the dry layer.​

[0146] According to a specific embodiment of the present application, the reservoir geological features include structural and stratigraphic features, lithologic and lithofacies features.

[0147] The present application also provides a volcanic rock matrix-fracture double medium type reservoir oil layer evaluation system, comprising a processor, which can execute a computer program, and the computer program can realize the volcanic rock matrix-fracture double medium type reservoir oil layer evaluation method.

[0148] Example 1

[0149] As shown in Figure 7 , the present application provides a volcanic rock matrix-fracture double medium type reservoir oil layer evaluation method, comprising the following steps:

[0150] (1) determining the reservoir geological features, reservoir features and oil layer distribution features of the area to be studied, and clarifying the relationship between lithology and oiliness;

[0151] (2) judging the reservoir type of the area to be studied through data synthesis, and clarifying the fracture distribution features;

[0152] (3) using core analysis data, adopting core calibration logging technology, and determining the matrix porosity of the area to be studied;

[0153] (4) in view of the characteristics of the volcanic rock matrix-fracture double medium oil and gas reservoir, adding a fracture pore conductive channel in the pore conductive channel of the Archie sandstone conductive model, considering that the volcanic rock matrix-fracture type reservoir is the result of parallel conductive of matrix pores and fracture pores, and deducing the fracture porosity of the matrix-fracture type oil layer;

[0154] (5) using the saturation calculation model of the matrix-fracture type reservoir to interpret the reservoir of the area to be studied, and obtaining the oil saturation of the matrix-fracture type reservoir;

[0155] (6) taking the calculated matrix porosity, fracture porosity and oil saturation of the reservoir of the area to be studied as independent variables, taking the two groups of test results of the oil layer and dry layer which have been proved by oil testing as dependent variables, through discriminant analysis of mathematical statistics, reducing the multi-dimensional independent variables to form new variables, the new variables make the inter-group mean difference of the two groups of dependent variables of the oil layer and dry layer reach the maximum, and the sum of squares of variances of each point in the group reaches the minimum, so as to establish the discriminant equation of the matrix-fracture type reservoir oil layer.

[0156] Example 2

[0157] As shown in Figures 1-5 , and Figure 7 , the present application provides a volcanic rock matrix-fracture double medium type reservoir oil layer evaluation method, comprising the following steps:

[0158] 1. Determine the geological characteristics of the reservoir, reservoir characteristics and oil layer distribution characteristics of the area to be studied, including but not limited to structural and stratigraphic characteristics, lithological and lithofacies characteristics, reservoir characteristics, oil layer distribution characteristics, and the relationship between lithology and oiliness;

[0159] The experimental study area develops multiple fault-controlled reservoirs, and the Carboniferous system is a set of terrestrial alluvial fan deposits strongly affected by volcanic activity. The lithology is mainly basalt, andesite, volcanic breccia, sandy conglomerate, argillaceous siltstone and tuff, etc. The lithology of the production layer with commercial oil flow is mostly developed in volcanic rocks (andesite, basalt, volcanic breccia lava), and the development degree of cracks determines the yield.

[0160] 2. Determine the reservoir type and fracture distribution characteristics of the area to be studied through data integration:

[0161] Through analysis of the complex pressure data, production dynamic data, imaging logging data and cast thin section data in the experimental study area, it is found that the reservoir type in this area is a fracture-matrix type reservoir with fractures as the main controlling factor. The fracture system is not only the main channel for oil and gas seepage, but also associated with a large number of secondary pores related to fractures, which constitute the main storage space in the reservoir. It can be said that without the fracture network system, it is impossible to form an effective volcanic reservoir.

[0162] 3. Use core analysis data to determine the matrix porosity of the area to be studied by using core calibration logging technology.

[0163] Through core homing correction of the porosity analysis samples of the coring wells in the experimental study area, the relationship between the logging acoustic time difference and the core analysis porosity is established as shown in the following formula: Figure 1 Considering that the laboratory porosity is measured by pyrolysis method, and the related extraction and pyrolysis parallel experiment analysis has been done in the early stage, it is found that there is the following relationship between the porosity of the extraction method and the pyrolysis method: The calculated porosity can be corrected by using the above formula.

[0164] 4. According to the characteristics of volcanic rock matrix-fracture type dual medium oil and gas reservoir, add the fracture pore conductive channel in the pore conductive channel of the Archie sandstone conductive model, consider that the volcanic rock matrix-fracture type reservoir is the result of parallel conductive of matrix pores and fracture pores, and deduce the fracture porosity of the matrix-fracture type oil layer.

[0165] When the volcanic rock reservoir is a fracture porosity type dual reservoir space type, it is considered that the rock conductive path is the result of parallel conductive of fracture fluid, rock pore fluid and rock skeleton, which constitutes a composite system of matrix pores and fracture pores, and its conductive model is:

[0166] (1) ​

[0167] wherein,

[0168] Rm is the resistivity of the matrix system when 100% saturated with water, Ω•m;

[0169] Rw is the resistivity of the formation water, Ω•m;

[0170] f is the ratio of the fracture porosity to the total porosity of the composite system;

[0171] φt is the total porosity of the composite system;

[0172] Rm is the resistivity of the matrix system when 100% saturated with water, Ω•m;

[0173] The fracture porosity can be obtained by (2);

[0174] wherein, φm is the matrix porosity.

[0175] In the case of only the matrix, the matrix portion satisfies the following formula:

[0176] (3)

[0177] For the composite system of the matrix porosity and the fracture porosity, the following formula is satisfied:

[0178] (4)

[0179] Substituting formula (3) and (4) into formula (1), the following formula is obtained:

[0180] (5)

[0181] Substituting formula (5) into formula (2), the fracture porosity calculation formula is obtained as follows:

[0182] (6)

[0183] wherein,

[0184] φm is the matrix porosity;

[0185] Cm is the cementation exponent of the matrix portion;

[0186] Rm is the resistivity of the matrix system when 100% saturated with water, Ω•m;

[0187] The cementation exponent of the composite system;

[0188] The formation factor of the composite system.

[0189] The formula for calculating the fracture porosity in the above formula is an implicit function and cannot be directly obtained. Theory and experiments have proved that in the medium-high porosity sandstone model The value is generally 1.5-3. Considering the strong pore heterogeneity in the study area, the matrix porosity is small, and in addition to the relevant rock-electricity experiments that have been done, the experimental study area The value is 2.25, which can be substituted into the above formula to obtain The relationship between matrix porosity and cementation exponent under different fracture porosities when = 2.25 is shown in the chart as Figure 4 .

[0190] As can be seen from the formula and chart, the actual fracture porosity is related to the matrix porosity and the cementation exponent of the composite system . The matrix porosity can be obtained from the porosity model in the third step. The total cementation exponent can be obtained by the following method: It is generally believed that the flushing zone resistivity detection distance is relatively short, and the flushing zone is completely filled with mud filtrate. The resistivity measured by the flushing zone can be approximately considered as the resistivity of the composite rock mass system, and the cementation exponent of the composite system can be obtained by the following method:

[0191] The resistivity measured by the flushing zone is approximately considered as the resistivity of the composite rock mass system. The flushing zone Archie formula is derived as follows:

[0192] (7);

[0193] In the formula,

[0194] is the mud filtrate resistivity, Ω•m;

[0195] a is the lithology coefficient in the Archie formula;

[0196] is the resistivity measured by the flushing zone, Ω•m.

[0197] The fracture porosity can be calculated by computer interpolation using Figure 4 the chart.

[0198] 5. The saturation calculation model of the matrix-fracture type reservoir is used to interpret the reservoir in the study area, and the oil saturation of the matrix-fracture type reservoir is obtained:

[0199] Considering that the volcanic reservoir in the experimental study area is mainly a pore-fracture double-porosity medium, the saturation calculation model for fractured reservoirs is more in line with the actual reservoirs. The saturation interpretation in this embodiment uses the saturation equation for horizontal fracture-pore reservoirs:

[0200] (8);

[0201] wherein,

[0202] Sor is the oil saturation of the matrix part, %;

[0203] S is the saturation index of the matrix part;

[0204] Rm is the measured resistivity, Ω•m;

[0205] φm is the matrix porosity;

[0206] φf is the fracture porosity;

[0207] Swm is the water saturation of the matrix part, %;

[0208] a and b are the lithology coefficients in the Archie formula;

[0209] , Cf and Cm are the cementation indices of the fracture part and the matrix part, respectively;

[0210] Rw is the formation water resistivity, Ω•m;

[0211] Rmf is the mud filtrate resistivity, Ω•m;

[0212] Cf is the fracture correction coefficient.

[0213] After substituting the relevant parameters of the study area, the oil saturation of the reservoir in the area can be obtained.

[0214] 6. The matrix porosity, fracture porosity, and oil saturation of the reservoir in the area calculated in the reaction are used as independent variables, and the two groups of test results of the oil layer and dry layer that have been verified by oil testing are used as dependent variables. Through discriminant analysis of mathematical statistics, the multi-dimensional independent variables are reduced to form new variables. The new variables make the inter-group mean difference of the two groups of dependent variables of the oil layer and dry layer reach the maximum, and the sum of squares of the variances of each point in the group reach the minimum. In this way, the discriminant equation of the matrix-fracture type reservoir oil layer is established.

[0215] Step 6 can be divided into the following steps in detail:

[0216] 1) Based on the known oil layer and dry layer data, the three parameters of fracture porosity, matrix porosity and oil saturation are introduced, which can reflect the quality of reservoir space, pore structure, and the degree of fracture development and reservoir quality.

[0217] 2) The "weight" of the three variables of fracture porosity, matrix porosity and oil saturation to the response of oil layer and dry layer is obtained by discriminant analysis of mathematical statistics (fisher discriminant method is used in this embodiment).

[0218] 3) In this embodiment, 306 data points of oil and dry layer of 5 wells (6 oil layers and 3 dry layers) in the tested reservoir are used, including 169 data points of oil layer and 137 data points of dry layer (Table 1), to obtain the discriminant function wherein, is the matrix porosity, is the oil saturation of the matrix part, and the discriminant function Y essentially reflects the comprehensive of logging multi-parameters, which represents the storage and permeability of the reservoir and can be used as a collective value reflecting the storage and permeability conditions. The discriminant value has strong operability and less human factors.

[0219] 4) The oil reservoir in the study area belongs to a heterogeneous fractured reservoir mainly controlled by fractures, so the role of fracture factor in determining the lower limit of effective thickness cannot be ignored. Therefore, it is necessary to further discriminate based on the above multi-parameter discrimination and a certain lower limit of fracture porosity to eliminate the misjudged data points, so as to make the division of effective thickness more reasonable and reliable. , as the final discrimination of the fractured reservoir in this area. Figure 5 .

[0220] Table 1: Data table for establishing the discriminant function of the effective thickness of the oil layer in the study area

[0221]

[0222] Example 3

[0223] The steps not described in detail in this embodiment are the same as those in the above embodiment, which will not be described here.

[0224] Based on the basic geological conditions of a certain well area in an oilfield within a certain jurisdiction, the Carboniferous reservoir in this area is mainly composed of volcanic rocks. Compressed pressure data, production dynamics data, imaging logging data, and cast thin section data all indicate that the reservoir type in this area is a matrix-fracture type, with fractures as the primary controlling factor. Using lithological indicator data such as core sampling, thin section identification, and logging cuttings, the rock type was comprehensively determined. Firstly, the volcanic lithology was classified into basalt, andesite, volcanic breccia, tuffaceous sandstone, and tuff. The lithological types determined by the core sampling points were used to calibrate the logging curves for the corresponding depth ranges. Based on the established cross-sectional charts, the lithology of the target layer in the entire well area was interpreted, and the lithological classification of the target layer in the well area was determined. See the lithological classification section below. Figure 6 The lithological interpretation of a single well in a certain well area is shown in the diagram.

[0225] A porosity parameter interpretation model was obtained by linearly regressing the matrix porosity values ​​measured by the porosity-permeability experiment with the corresponding acoustic transit time values. Using this model, the porosity parameters were interpreted. Then, based on the following relationship between the porosity obtained by the extraction and pyrolysis methods, the matrix porosity was corrected. (See...) Figure 6 The interpretation results of a single well in a certain well area are shown in the matrix porosity channel and the matrix porosity correction channel.

[0226] Based on the preceding analysis, it is believed that the rock's electrical conductivity pathway is the result of parallel conductivity of fracture fluid, rock block pore fluid, and rock block skeleton. The calculation equation for fracture porosity under this conductivity mode has already been derived. However, because this equation is an implicit function equation, an analytical solution cannot be obtained. This embodiment uses the innovative solution method described in Example 2 to calculate the fracture porosity as 0.1% (…). Figure 6 F01), the crack porosity is 0.2% ( Figure 6 F02), the crack porosity is 0.4% ( Figure 6 (F04), the crack porosity is 0.6% ( Figure 6 (F06), the crack porosity is 0.8% ( Figure 6 F08), with a crack porosity of 1% ( Figure 6 F10), with a crack porosity of 2% ( Figure 6 F20), with a crack porosity of 4% ( Figure 6 Under the condition of F40 channels, the relationship between matrix porosity and the composite system m is then considered, and the m value of the composite system calculated based on the resistivity of the flushing belt is then used. Figure 6 The m value is calculated and plotted on a graph showing m under different fracture porosity conditions. Interpolation can then be used to obtain the fracture porosity of this well. Figure 6 (crack porosity channels).

[0227] Based on the preceding analysis, the saturation calculation model for fractured reservoirs is more consistent with the characteristics of actual oil reservoirs. Using this model, the matrix oil saturation of this well is obtained.Figure 6 , the matrix oil saturation channel). Then, the fracture porosity, the matrix porosity and the matrix oil saturation obtained by the foregoing calculation are substituted into the "weight" formula of the oil layer and the dry layer response, so that the Y value of the discrimination function is obtained (Y value channel) Figure 5 , the Y value channel), according to the intersection chart of the Y value and the fracture porosity (Y value channel), the oil layer evaluation method of the fractured reservoir can be obtained. Figure 6

[0228] The evaluation precision of the method is evaluated: four oil layers are interpreted by the method, which are 1688.02~1692.30m, 1751.90~1754.34m, 1810.10~1811.08m and 1839.99~1843.66m, and there are perforations near the four sections, wherein the daily oil production of the combined test of the perforated sections 1810~1816 and 1839.0~1845 is 21.43 tons, and the daily oil production of the combined test of the perforated sections 1689~1696 and 1750.0~1758 is 103.2 tons (test oil pie chart), and the test oil result fully verifies the reliability of the method. ​

[0229] The above merely describes the preferred embodiments of the present application and is not used to limit the present application, and the present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application is included in the protection scope of the present application.​​

Claims

1. A method for evaluating a volcanic rock matrix-fracture double medium type oil reservoir, characterized by, Comprise the following steps: (1) determine the characteristics of the reservoir geological characteristics, reservoir characteristics and oil layer distribution characteristics, clear lithology and oiliness relationship; (2) through the data comprehensive judgment of the reservoir type of the area to be studied, clear fracture distribution characteristics; (3) using core analysis data, using core calibration logging technology, determine the matrix porosity of the area to be studied; (4) for the characteristics of volcanic rock matrix-fracture double medium oil and gas reservoir, in the pore conductive channel of Archie sandstone conductive model, add fracture pore conductive channel, think that the volcanic rock matrix-fracture type oil reservoir is the result of parallel conductive of matrix pore and fracture pore, deduce the fracture porosity of matrix-fracture type oil layer; (5) using the saturation calculation model of matrix-fracture type reservoir to interpret the reservoir of the area to be studied, the oil saturation of matrix-fracture type reservoir is obtained; (6) the calculated matrix porosity, fracture porosity and oil saturation of the reservoir of the area to be studied are taken as independent variables, and the two groups of oil testing results of the oil layer and dry layer which have been proved by oil testing are taken as dependent variables, through mathematical statistical discriminant analysis, the multi-dimensional independent variables are reduced to form new variables, the new variables make the inter-group mean difference of the two groups of dependent variables reach the maximum, and the sum of squares of the variance of each point in the group reaches the minimum, so as to establish the discriminant equation of the oil layer of matrix-fracture type reservoir; In step (4), when it is a volcanic rock matrix-fracture double medium oil and gas reservoir, the composite system composed of matrix pore and fracture pore has the conductive model as follows: （1） In the formula, Rcompl is the resistivity of the composite system when 100% saturated with water, Ω-m; Rw is the formation water resistivity, Ω-m; is the ratio of the fracture porosity in the fracture section to the total porosity of the composite system; Ptotai is the total porosity of the composite system; Rmat 100% water-saturated, Ω-m; and Rmat 0% water-saturated, Ω-m. Available fracture porosity (2); wherein, is the matrix porosity; Step (6) specifically comprises the following steps: Step (61), introduce the calculated fracture porosity, matrix porosity and oil saturation in the tested known oil layer and dry layer data; Step (62), get the weight of fracture porosity, matrix porosity and oil saturation on the response of oil layer and dry layer through mathematical statistical discriminant analysis; Step (63), according to the weight of fracture porosity, matrix porosity and oil saturation on the response of oil layer and dry layer, get the discriminant function composed of fracture porosity, matrix porosity and oil saturation, form the oil layer and dry layer discriminant chart by combining the discriminant value of the discriminant function with the fracture porosity, the horizontal coordinate of the oil layer and dry layer discriminant chart is the discriminant value Y of the discriminant function, and the vertical coordinate is the fracture porosity; Step (64), by reading the oil layer, dry layer discrimination chart, when the interpretation section meets the conditions of , at the same time, the interpretation section is considered as oil layer section, otherwise it is considered as dry layer section, forming the final discrimination of matrix-fracture reservoir in the area to be studied, is the fracture porosity.

2. The volcanic matrix-fracture dual media type reservoir reservoir evaluation method according to claim 1, characterized in that, Only the matrix exists, the matrix part satisfies the following formula: （3） For the composite system of matrix pore and fracture pore, the following formula is satisfied: （4） Substitute formula (3) and (4) into formula (1) to get: （5） Substitute formula (5) into formula (2) to get the fracture porosity calculation formula as follows: （6） In the formula, for the matrix porosity; the cementation index of the matrix portion; formation factors that are matrix portions; the cementation index for the composite system; Formation factors for composite systems.

3. The volcanic matrix-fracture dual media type reservoir reservoir evaluation method according to claim 2, characterized in that, The matrix portion has a cementitious index The value is typically between 1.5 and 3.

4. The volcanic matrix-fracture dual media type reservoir reservoir evaluation method according to claim 3, characterized in that, The cementation exponent of the matrix part is determined according to the pore characteristics of the area to be studied The cementation exponent of the matrix part is determined according to the pore characteristics of the area to be studied The cementation exponent of the matrix part is determined according to the pore characteristics of the area to be studied The cementation exponent of the matrix part is determined according to the pore characteristics of the area to be studied The cementation exponent of the matrix part is determined according to the pore characteristics of the area to be studied 5. The volcanic rock matrix-fracture double medium type reservoir oil layer evaluation method according to claim 4, characterized in that, The cementation index of the composite system is determined by the following method: The resistivity measured by the flushing zone is approximately equal to the resistivity of the composite system, and the following formula is derived from the flushing zone Archie formula: （7）； In the formula, Rm is the mud filtrate resistivity, Ω-m; A is the lithology coefficient in the Arps formula; Resistivity measured for the flush tape, Ω • m.

6. The volcanic matrix-fracture dual media type reservoir reservoir evaluation method according to any one of claims 1 to 5, characterized in that, In step (3), the relationship between the total porosity of the experimental matrix and the acoustic travel time Δt is established by core positioning correction of the coring sample in the area to be studied. t .​​ 7. The volcanic matrix-fracture dual media type reservoir reservoir evaluation method according to claim 6, characterized in that, Considering that the laboratory porosity determination is made by pyrolysis, the following relationship between porosity by extraction and pyrolysis is used: The total porosity of the experimental matrix is corrected to obtain the matrix porosity .

8. The volcanic matrix-fracture dual media type reservoir reservoir evaluation method according to claim 1, characterized in that, In step (5), the saturation interpretation adopts the saturation equation of horizontal fracture-pore type reservoir: （8）； In the formula, Oil saturation for the matrix portion; Saturation index for the matrix portion; for well logging measurements of resistivity, Ω-m; For matrix porosity; is the fracture porosity; water saturation of the matrix portion; a and b are lithology coefficients in the Archie formula; , respectively the cementation index of the fracture part and the cementation index of the matrix part; Rw is the formation water resistivity, Ω-m; Rm is the mud filtrate resistivity, Ω-m; is the fracture correction factor.

9. The volcanic matrix-fracture dual media type reservoir reservoir evaluation method according to claim 1, characterized in that, The discriminant function is wherein, is the matrix porosity, is the matrix fraction oil saturation.

10. The volcanic matrix-fracture dual media type reservoir reservoir evaluation method according to claim 1, characterized in that, The reservoir geological characteristics include structural and stratigraphic characteristics, lithology and lithofacies characteristics.

11. A volcanic matrix-fracture dual media type reservoir reservoir evaluation system, characterized by, A computer program product comprising a computer readable medium having stored thereon the computer program enabling a method of evaluating a volcanic matrix-fracture double porosity type reservoir according to any one of claims 1 to 10 when being executed by a processor.

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