A method for calculating the quantitative evolution of pores in a tight sandstone reservoir with no fracture development

Abstract

The application discloses a kind of tight sandstone reservoir pore quantitative evolution calculation method of crack not development, including obtaining the relevant data of the quantitative evolution calculation of pore in research area;The quantitative parameter related to pore evolution is counted by the relevant data;According to the relevant data, the reservoir diagenetic stage analysis, main diagenesis type and diagenetic evolution sequence of different diagenesis are determined;According to quantitative parameter, initial porosity is calculated;The total porosity lost by compaction is calculated;The total porosity lost by calcareous, siliceous and clay cementation is calculated;The total porosity increased by dissolution is calculated;The total amount of transformation of kaolinite late transformation is calculated;With reservoir diagenetic evolution sequence, burial history and oil and gas charging period as constraint, the size of reservoir porosity at different depths is calculated.The method of the application can better analyze the pore evolution process of deep tight sandstone reservoir with large burial depth, poor physical property and complex diagenesis.

Description

Technical Field

[0001] This invention relates to a method for calculating the quantitative evolution of porosity in tight sandstone reservoirs with undeveloped fractures. Background Technology

[0002] In recent years, with the increasing demand for natural gas energy in my country, tight gas has gradually attracted attention. However, due to the long diagenetic processes (compaction, cementation, and dissolution) that have occurred in deep tight reservoirs, the rock fragments are in close contact, and the pores are mostly filled with cement, resulting in reduced porosity and a generally poor pore structure, making research extremely difficult. Since pores serve as the space for reservoir oil and gas storage, their development level determines the reservoir's oil and gas storage potential and greatly influences the development characteristics of tight sandstone "sweet spots," making it a key focus of oil and gas exploration and development both domestically and internationally in recent years.

[0003] Current exploration and development research suggests that tight reservoirs generally have well-developed fractures, which significantly improve the reservoir's pore structure and are of great importance for its exploration and development. However, in the deep stratigraphic exploration and development of basins along the eastern coast of China, tight sandstone reservoirs contain relatively abundant natural gas reserves. These reservoirs are dominated by intergranular and intragranular pores with relatively poor connectivity, and fractures are not well-developed, making research more challenging. Therefore, strengthening the quantitative evolution study of porosity in tight reservoirs is a key focus for the exploration and development of this type of reservoir, and it has important guiding significance for predicting the "sweet spots" of such tight reservoirs.

[0004] Existing methods for studying pore evolution mainly rely on the "inversion stripping method" to establish a quantitative calculation method for pore depth based on the diagenetic evolution sequence of reservoirs. The main problems are: (1) Most scholars still rely on simple qualitative calculations when using this method, resulting in relatively vague calculation results; (2) This calculation method treats all cement-filled pores as dissolution pores or primary pores, leading to errors in the inversion of reservoir dissolution intensity; (3) The quantitative influence of different cements at different diagenetic stages on reservoir pores is relatively weak. Therefore, this patent, based on the improved "inversion stripping method," systematically studies the quantitative evolution of pores in deep tight sandstone reservoirs, taking into account the diagenetic evolution sequence, burial history, hydrocarbon charging history, and late-stage kaolinite transformation. The overall effect is better. Summary of the Invention

[0005] To overcome the shortcomings of the "inversion stripping method" in porosity evolution research, this invention aims to provide a quantitative calculation method for the porosity evolution of tight sandstone reservoirs with underdeveloped fractures. This method primarily utilizes experimental techniques such as reservoir powder particle size analysis, X-ray diffraction, physical property testing, ordinary thin sections of rocks, thin sections of rock castings, and scanning electron microscopy, combined with reservoir diagenesis studies, burial history, and hydrocarbon charging studies, to obtain a quantitative calculation model for the porosity evolution of deep tight reservoirs, thereby reducing the porosity evolution errors caused by the calculation method.

[0006] The technical solution provided by this invention to solve the above-mentioned technical problems is: a method for calculating the quantitative evolution of porosity in tight sandstone reservoirs with underdeveloped fractures, comprising the following steps:

[0007] Step S10: Obtain relevant data for quantitative porosity evolution calculation in the study area;

[0008] Step S20: Calculate the quantitative parameters related to pore evolution based on the above-mentioned relevant data;

[0009] Step S30: Based on the above relevant data, clarify the reservoir diagenetic stage analysis, the main diagenetic types, and the diagenetic evolution sequence of different diagenetic processes;

[0010] Step S40: Calculate the initial porosity based on the quantitative parameters;

[0011] Step S50: Calculate the total porosity lost due to compaction.

[0012] Step S60: Calculate the total porosity loss due to cementation by calcareous, siliceous, and clay substances;

[0013] Step S70: Calculate the total porosity increase caused by dissolution.

[0014] Step S80: Calculate the total amount of kaolinite transformation in the later stages;

[0015] Step S90: Using the reservoir diagenetic evolution sequence, burial history, and hydrocarbon charging period as constraints, calculate the porosity of reservoirs at different depths.

[0016] A further technical solution is that the relevant data includes: reservoir powder particle size, X-ray diffraction, physical property testing, ordinary thin sections of rock, thin sections of rock castings, and scanning electron microscopy.

[0017] A further technical solution is that the quantitative parameters include the Φ value corresponding to the cumulative particle content at 84%, 16%, 95%, and 5% on the cumulative particle size curve, porosity, calcareous cement content, siliceous cement content, clay matrix content, total porosity, mold porosity, intragranular dissolved porosity, primary intergranular porosity, intergranular dissolved porosity, total clay content, relative chlorite content, relative illite content, relative illite-montmorillonite mixed layer content, and relative kaolinite content.

[0018] A further technical solution is that the calculation formula in step S50 is:

[0019]

[0020] In the formula: This refers to the residual porosity after reservoir compaction. denoted as initial porosity; C as compaction factor; and Z as burial depth.

[0021] A further technical solution is that the calculation formula in step S60 is:

[0022] W1 = W x -W n

[0023] W (c) =W1×c

[0024] W (I) =W1×I

[0025] W (IS) =W1×I S

[0026] W (K) =W1×K

[0027]

[0028] In the formula: W1 represents the porosity reduction of the clay cement from diagenetic origin; W x W represents the total amount of clay as determined by X-ray diffraction. n c represents the clay matrix content identified in the thin section; c represents the relative chlorite content in the X-ray diffraction; I represents the relative illite content in the X-ray diffraction; I S W represents the relative content of illite-montmorillonite mixed layers in X-ray diffraction; K represents the relative content of kaolinite in X-ray diffraction; W represents the relative content of kaolinite in X-ray diffraction. (c) Chlorite reduces porosity; W (I) The reduced porosity of illite; Reduced porosity of the monazite-saturated mixed layer; W (K) The reduced porosity of kaolinite; Reduced porosity for all cementing materials.

[0029] A further technical solution is that the calculation formula in step S70 is:

[0030]

[0031]

[0032]

[0033] In the formula: k represents the relative content of dissolution porosity; The porosity of the etched pores; Total face rate; For the hole ratio of the mold cavity; The porosity of intragranular dissolved pores; The porosity of the primary intergranular pores; The porosity of intergranular dissolved pores; Increased porosity for dissolution; Porosity was used for physical property testing.

[0034] A further technical solution is that the calculation formula in step S80 is:

[0035] W (K，转) =(W (c) -W (c，转) +W (I) +W (I，转) )+W (K)

[0036] W (c，转) =W2×Z ( ' c，转) / Z (c)

[0037] W (I，转) =W2×Z ( ' I，转) / Z (I)

[0038] In the formula: W (K，转) This represents the kaolinite content at the point where kaolinite begins to transform into other clay minerals; W (c，转) W represents the amount of chlorite cementation after kaolinite begins to transform into other clay minerals. (I，转) Z represents the amount of illite cementation after kaolinite begins to transform into other clay minerals; ( ' c，转) Z represents the total thickness of the depth segment corresponding to the period of chlorite cementation when kaolinite begins to transform into other clay minerals; (c) Z represents the total thickness of the depth segment corresponding to the cementation period of chlorite throughout the entire evolutionary stage; ( ' I，转) Z represents the total thickness of the depth segment corresponding to the illite cementation period when kaolinite begins to transform into other clay minerals; (I) The total thickness of the depth segment corresponding to the illite cementation period throughout the entire evolutionary stage.

[0039] A further technical solution is that the calculation formula in step S80 is:

[0040]

[0041] In the formula: Z is the burial depth; Z ( ' Ca) Z represents the total thickness of the depth segment corresponding to the period of calcareous cementation when the reservoir is buried to depth Z; (Ca) Z represents the total thickness of the depth segment corresponding to the period of calcareous cementation throughout the entire evolutionary stage; ( ' Si)Z represents the total thickness of the depth segment corresponding to the period of siliceous cementation when the reservoir is buried to depth Z; (Si) Z represents the total thickness of the depth segment corresponding to the period of siliceous cementation during the entire evolutionary stage. ( ' c) Z represents the total thickness of the depth corresponding to the period of chlorite cementation when the reservoir is buried to Z; (c) Z represents the total thickness of the depth segment corresponding to the cementation period of chlorite throughout the entire evolutionary stage; ( ' I) Z represents the total thickness of the depth corresponding to the illite cementation period when the reservoir is buried to depth Z; (I) Z represents the total thickness of the depth segment corresponding to the illite cementation period throughout the entire evolutionary stage; ( ' IS) Z represents the total thickness of the depth corresponding to the period of cementation of the illite-montmorillonite mixed-layer formation when the reservoir is buried to Z; (IS) Z represents the total thickness of the depth segment corresponding to the period of Iso-Montene mixed-layer cementation during the entire evolutionary stage; ( ' K) Z represents the total thickness of the depth corresponding to the period of kaolinite cementation when the reservoir is buried to Z; (K) Z represents the total thickness of the depth segment corresponding to the kaolinite cementation period throughout the entire evolutionary stage; ( ' K，转) The total thickness of the depth segment corresponding to the period when kaolinite transforms into other clay minerals at depth Z; Z (K，转) Z represents the total depth of the periods during which kaolinite transformed into other clay minerals throughout the entire evolutionary process. (r) The total thickness of the depth segment corresponding to the dissolution period when the reservoir is buried to depth Z; Z (r) Z represents the total thickness of the depth segment corresponding to the dissolution period throughout the entire evolutionary stage; ( ' r，弱溶) The total thickness of the depth segment corresponding to the period of weak dissolution when the reservoir is buried to depth Z; Z (r，弱溶) This represents the total thickness of the depth segment corresponding to the weak dissolution period during the entire evolutionary stage.

[0042] This invention offers the following advantages: It combines existing data (X-ray diffraction, thin section analysis, scanning electron microscopy, etc.) to determine reservoir petrological characteristics, reservoir space development, diagenetic characteristics, and diagenetic evolution sequences; it clarifies the reservoir burial process and hydrocarbon charging period; and it calculates the porosity of reservoirs at different depths, constrained by the reservoir diagenetic evolution sequence, burial history, and hydrocarbon charging period. The method of this invention can effectively analyze the porosity evolution process of deep, tight sandstone reservoirs with large burial depths, poor physical properties, and complex diagenetic processes. Attached Figure Description

[0043] Figure 1A flowchart illustrating the quantitative evolution of pore size;

[0044] Figure 2 This is a porosity distribution characteristic diagram;

[0045] Figure 3 A characteristic map of porosity distribution for different pore types;

[0046] Figure 4 A graph showing the relative content of different pore types;

[0047] Figure 5 Diagram showing the composition and porosity of different rock components;

[0048] Figure 6 This is a sequence diagram of reservoir diagenesis and pore evolution.

[0049] Figure 7 A historical map of reservoir burial;

[0050] Figure 8 This is a diagram showing the evolution of reservoir porosity.

[0051] Figure 9 This diagram shows the evolution of reservoir pores and the influence of different diagenetic processes on porosity. Detailed Implementation

[0052] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] like Figure 1 As shown, the present invention provides a method for calculating the quantitative evolution of porosity in tight sandstone reservoirs with underdeveloped fractures, comprising the following steps:

[0054] Step S10: Obtain relevant data for quantitative porosity evolution calculation in the study area (reservoir powder particle size, X-ray diffraction, physical property testing, ordinary thin sections of rocks, thin sections of rock castings, and scanning electron microscopy);

[0055] Step S20: Based on the above-mentioned relevant data, statistically analyze the quantitative parameters related to pore evolution (Φ value, porosity, calcareous cement content, siliceous cement content, clay matrix content, total porosity, casting mold porosity, intragranular dissolution porosity, primary intergranular porosity, intergranular dissolution porosity, total clay content, relative chlorite content, relative illite content, relative illite-montmorillonite mixed layer content, and relative kaolinite content).

[0056] Step S30: Based on the above relevant data, clarify the reservoir diagenetic stage analysis, the main diagenetic types, and the diagenetic evolution sequence of different diagenetic processes;

[0057] Step S40: Calculate the initial porosity based on the quantitative parameters;

[0058] Step S50: Calculate the total porosity lost due to compaction.

[0059]

[0060] In the formula: This refers to the residual porosity after reservoir compaction. C is the initial porosity; C is the compaction factor; Z is the burial depth.

[0061] Step S60: Calculate the total porosity loss due to cementation by calcareous, siliceous, and clay substances;

[0062] W1 = W x -W n

[0063] W (c) =W1×c

[0064] W (I) =W1×I

[0065] W (IS) =W1×I S

[0066] W (K) =W1×K

[0067]

[0068] In the formula: W1 represents the porosity reduction of the clay cement from diagenetic origin; W x W represents the total amount of clay as determined by X-ray diffraction. n c represents the clay matrix content identified in the thin section; c represents the relative chlorite content in the X-ray diffraction; I represents the relative illite content in the X-ray diffraction; I S W represents the relative content of illite-montmorillonite mixed layers in X-ray diffraction; K represents the relative content of kaolinite in X-ray diffraction; W represents the relative content of kaolinite in X-ray diffraction. (c) Chlorite reduces porosity; W (I) Reduced porosity due to illite; W (IS) Reduced porosity of the monazite-saturated mixed layer; W (K) The reduced porosity of kaolinite; Reduced porosity for all cementitious materials;

[0069] Step S70: Calculate the total porosity increase caused by dissolution.

[0070]

[0071]

[0072]

[0073] In the formula: k represents the relative content of dissolution porosity; The porosity of the etched pores; Total face rate; For the hole ratio of the mold cavity; The porosity of intragranular dissolved pores; The porosity of the primary intergranular pores; The porosity of intergranular dissolved pores; Increased porosity for dissolution; For physical property testing, porosity is tested.

[0074] Step S80: Calculate the total amount of kaolinite transformation in the later stages;

[0075] W (K，转) =(W (c) -W (c，转) +W (I) +W (I，转) )+W (K)

[0076] W (c，转) =W2×Z ( ' c，转) / Z (c)

[0077] W (I，转) =W2×Z ( ' I，转) / Z (I)

[0078] In the formula: W (K，转) This represents the kaolinite content at the point where kaolinite begins to transform into other clay minerals; W (c，转) W represents the amount of chlorite cementation after kaolinite begins to transform into other clay minerals. (I，转) Z represents the amount of illite cementation after kaolinite begins to transform into other clay minerals; ( ' c，转) Z represents the total thickness of the depth segment corresponding to the period of chlorite cementation when kaolinite begins to transform into other clay minerals; (c) Z represents the total thickness of the depth segment corresponding to the cementation period of chlorite throughout the entire evolutionary stage; ( ' I，转) Z represents the total thickness of the depth segment corresponding to the illite cementation period when kaolinite begins to transform into other clay minerals; (I) The total thickness of the depth segment corresponding to the illite cementation period throughout the entire evolutionary stage;

[0079] Step S90: Using the reservoir diagenetic evolution sequence, burial history, and hydrocarbon charging period as constraints, calculate the porosity of reservoirs at different depths;

[0080]

[0081] In the formula: Z is the burial depth; Z ( ' Ca) Z represents the total thickness of the depth segment corresponding to the period of calcareous cementation when the reservoir is buried to depth Z; (Ca) Z represents the total thickness of the depth segment corresponding to the period of calcareous cementation throughout the entire evolutionary stage; ( ' Si) Z represents the total thickness of the depth segment corresponding to the period of siliceous cementation when the reservoir is buried to depth Z; (Si) Z represents the total thickness of the depth segment corresponding to the period of siliceous cementation during the entire evolutionary stage. ( ' c) Z represents the total thickness of the depth corresponding to the period of chlorite cementation when the reservoir is buried to Z; (c) Z represents the total thickness of the depth segment corresponding to the cementation period of chlorite throughout the entire evolutionary stage; ( ' I) Z represents the total thickness of the depth corresponding to the illite cementation period when the reservoir is buried to depth Z; (I) Z represents the total thickness of the depth segment corresponding to the illite cementation period throughout the entire evolutionary stage; ( ' IS) Z represents the total thickness of the depth corresponding to the period of cementation of the illite-montmorillonite mixed-layer formation when the reservoir is buried to Z; (IS) Z represents the total thickness of the depth segment corresponding to the period of Iso-Montene mixed-layer cementation during the entire evolutionary stage; ( ' K) Z represents the total thickness of the depth corresponding to the period of kaolinite cementation when the reservoir is buried to Z; (K) Z represents the total thickness of the depth segment corresponding to the kaolinite cementation period throughout the entire evolutionary stage; ( ' K，转) The total thickness of the depth segment corresponding to the period when kaolinite transforms into other clay minerals at depth Z; Z (K，转) Z represents the total depth of the periods during which kaolinite transformed into other clay minerals throughout the entire evolutionary process. (r) The total thickness of the depth segment corresponding to the dissolution period when the reservoir is buried to depth Z; Z (r) Z represents the total thickness of the depth segment corresponding to the dissolution period throughout the entire evolutionary stage; ( ' r，弱溶) The total thickness of the depth segment corresponding to the period of weak dissolution when the reservoir is buried to depth Z; Z (r，弱溶) This represents the total thickness of the depth segment corresponding to the weak dissolution period during the entire evolutionary stage.

[0082] Example

[0083] Step 1: Data Collection

[0084] First, a literature review was conducted to clarify the regional geological background, tectonic setting, stratigraphic and sedimentary characteristics, reservoir diagenetic characteristics, and burial history of the study area. Second, relevant data for quantitative porosity evolution calculations were collected, including [data missing]. Based on the above data, quantitative parameters related to porosity evolution were statistically analyzed, including the Φ values ​​corresponding to cumulative particle content of 84%, 16%, 95%, and 5% on the cumulative particle size curve (Φ...). 84 Φ 16 Φ 95 And Φ5 value, powder particle size); porosity ( Physical property tests); calcareous cement content (W2, ordinary thin section of rock); siliceous cement content (W3, ordinary thin section of rock); clay matrix content (W n (Ordinary thin sections of rock); Total porosity ( Rock casting thin sections; mold porosity ( Rock casting thin sections); intragranular porosity ( Rock casting thin sections); primary intergranular porosity ( Rock casting thin sections); intergranular dissolution porosity ( Rock casting thin sections); Total clay content (W) x X-ray diffraction (C, X-ray diffraction); relative chlorite content c (C, X-ray diffraction); relative illite content (I, X-ray diffraction); relative illite-montmorillonite mixed-layer content (I, X-ray diffraction) S (X diffraction); relative kaolinite content K (K, X diffraction).

[0085] Step 2: Reservoir diagenetic evolution stages, types of diagenesis, and the relationship between different diagenetic stages;

[0086] Based on reservoir X-ray diffraction, scanning electron microscopy, ordinary thin sections of rocks, thin sections of rock castings, Ro (vitrinite reflectance), and other data, combined with the mineral composition, grain contact relationships, cement occurrence and mutual filling relationships, replacement relationships between authigenic minerals, and dissolution characteristics of clastic reservoirs, this study clarifies the current diagenetic stage of the reservoir, the main types of diagenetic processes it has undergone, and the chronological order of different diagenetic processes. Combined with burial history simulation results and analysis of hydrocarbon charging periods, the study determines the approximate depth range corresponding to different diagenetic periods, providing a basis for the quantitative evolution of reservoir porosity at different stages.

[0087] Step 3: Initial porosity calculation;

[0088] Based on particle size analysis data, the initial porosity was calculated using the empirical formula for initial porosity established by Beard and Weyl, and the Folk sorting coefficient was used.

[0089]

[0090] S o =(Φ 84 +Φ 16 ) / 4+(Φ 95 +Φ5) / 6.6=1.45

[0091] In the formula, S represents the initial porosity. o Φ is the sorting coefficient (1.45); 84 (3.875), Φ 16 (1.387), Φ 95 (6.5) and Φ5(1.02) are the Φ values ​​corresponding to the cumulative particle content at 84%, 16%, 95% and 5% on the cumulative particle size curve, respectively;

[0092] The sorting coefficient S is obtained through the above calculations. o =1.45, the calculated initial porosity is 36.7%. When the reservoir has well-developed intercrystalline calcite, the compaction effect is extremely weak, which can better reflect the original porosity content of the reservoir. Statistical analysis of such thin sections using ImageJ software suggests that the initial porosity of the reservoir is approximately 36.15%.

[0093] Calculation error = abs(calculation result - thin section identification result) / thin section identification result × 100% = 1.52%;

[0094] Step 4: Calculate the total porosity loss due to compaction;

[0095] At a certain burial depth, the porosity remaining after compaction exhibits an exponential relationship with depth. The remaining primary porosity after compaction is:

[0096]

[0097] Step 5: Calculation of total porosity loss due to cementation by calcareous, siliceous, and clay elements;

[0098] Based on ordinary thin sections and X-ray diffraction, quantitative statistics were performed on different interstitial materials (calcareous, siliceous, argillaceous matrix, and different clays, etc.). The statistical contents of calcareous and siliceous cement components were approximated as the volume of cement porosity reduction, and denoted as W2 and W3, respectively. The statistical contents of argillaceous matrix identified in thin sections and the total clay content tested by X-ray diffraction were approximated as the argillaceous content and the current total clay content during the reservoir deposition period, respectively. The porosity reduction of different clay cements of different diagenetic origins was calculated.

[0099]

[0100] In the formula, W1 represents the porosity reduction of the diagenetic clay cement (8.15%); W xThe total clay content (all clay minerals, including diagenetic and sedimentary matrix, 11.13%) is determined by X-ray diffraction; W n c represents the content of argillaceous matrix identified in the thin section (sedimentary origin, 2.98%); c represents the relative content of chlorite in the X-ray diffraction (24.8%); I represents the relative content of illite in the X-ray diffraction (37%); I S λ represents the relative content of illite-montmorillonite mixed layers in X-ray diffraction (34%); K represents the relative content of kaolinite in X-ray diffraction (4.2%); W represents the relative content of kaolinite in X-ray diffraction (4.2%). (C) Chlorite reduces porosity; W (I) The reduced porosity of illite; Reduced porosity of the monazite-saturated mixed layer; W (K) The reduced porosity of kaolinite; Reduced porosity for all cementitious materials;

[0101] Step 6: Calculation of the total porosity increase due to dissolution;

[0102] Based on the statistical analysis of thin sections of rock castings, the porosity of different pore types was calculated, and combined with physical property test data, the porosity of different pore types was determined. Simultaneously, K (relative content of dissolution porosity) was introduced, and based on K, primary and secondary pores (dissolution pores) in intergranular dissolution pores, as well as primary and secondary pores occupied by cement, were distinguished to obtain the porosity increased by dissolution.

[0103]

[0104] In the formula, k represents the relative content of dissolution porosity; The porosity of the etched pores; The overall face rate was 3.9%. The porosity of the mold holes is 0.48%. The intragranular porosity was 1.42%. The porosity of the primary intergranular pores is 0.85%. The intergranular dissolved pore porosity (including primary and secondary pores, 1.15%); Increased porosity for dissolution; The porosity was measured as 8.43% for physical property testing.

[0105] Step 7: Pore reduction adjustment in the later stage of kaolinite transformation;

[0106] Based on a clear understanding of the current diagenetic stage of the reservoir, when the current diagenetic stage is before the end of the intermediate diagenetic A stage, the transformation of kaolinite into other clay minerals is not considered; when it is after the end of the intermediate diagenetic A stage, due to the change of the diagenetic environment from acidic to alkaline, the transformation of kaolinite into other clay minerals results in a lower content. Using the current kaolinite content as a constraint (W1), the chlorite and illite formed after the transformation of kaolinite into other clay minerals are taken as the total amount of kaolinite transformation.

[0107]

[0108]

[0109] W (K，转) This represents the kaolinite content at the point where kaolinite begins to transform into other clay minerals; W (c，转) W represents the amount of chlorite cementation after kaolinite begins to transform into other clay minerals. (I，转) Z′ represents the amount of illite cementation after kaolinite begins to transform into other clay minerals. (c，转) Z represents the total thickness of the depth segment corresponding to the period of chlorite cementation when kaolinite begins to transform into other clay minerals; (c) Z′ represents the total thickness of the depth segment corresponding to the chlorite cementation period throughout the entire evolutionary stage. (I，转) Z represents the total thickness of the depth segment corresponding to the illite cementation period when kaolinite begins to transform into other clay minerals; (I) The total thickness of the depth segment corresponding to the illite cementation period throughout the entire evolutionary stage.

[0110] Step 8: Quantitative calculation of porosity evolution based on the sequence of different diagenetic periods

[0111] Based on the above research, since the dissolution of cement is relatively small after its formation, the later-stage dissolution of cement is not considered. Because oil and gas charging provides a large amount of organic acidic fluids for the dissolution of reservoir clastic components, the reservoir dissolution period is divided into weak dissolution and strong dissolution periods according to the oil and gas charging time. The porosity increase during the weak dissolution period is calculated by dissolving and allocating 0.5 times the average porosity increase based on depth. Finally, constrained by the depth range corresponding to different diagenetic stages, a quantitative calculation method for reservoir porosity evolution is established based on the idea of ​​allocating porosity increase / decrease based on depth.

[0112]

[0113]

[0114] The calculation result is:

[0115]

[0116] Porosity calculation error

[0117] =abs(Current porosity - Physical property porosity) / Physical property porosity × 100%

[0118] =abs(8.47%-8.43%) / 8.43%=0.5%;

[0119] Original hole calculation error

[0120] =abs(Current primary porosity - Primary porosity of physical property porosity) / Primary porosity of physical property porosity × 100%

[0121] =abs[(initial porosity - compaction porosity reduction - (1-K) × current total cement content) - (physical property porosity × (1-K))] / (physical property porosity × (1-K)) × 100%

[0122] =abs[(36.7%-29.82%-(1-0.69)×13.53%)-(8.43%×(1-0.69))] / (8.43%×(1-0.69))×100%

[0123] =2.74%;

[0124] Error in calculation of dissolution holes

[0125] =abs(calculated current dissolution porosity - dissolution porosity of physical property porosity) / dissolution porosity of physical property porosity × 100%

[0126] =abs[(Total porosity from dissolution - K × Total amount of current cement) - Porosity of physical properties × K] / (Porosity of physical properties × K) × 100%

[0127] =abs[(15.14%-0.69×13.53%)-8.43%×0.69] / (8.43%×0.69)×100%=0.55%;

[0128] The above description is not intended to limit the present invention in any way. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention shall still fall within the scope of the present invention.

Claims

1. A method of calculating the quantitative evolution of the porosity of tight sandstone reservoirs with little fracture development, characterized in that, The method comprises the following steps: Step S10, obtaining relevant data for calculating the quantitative evolution of pores in a research area; Step S20, calculating quantitative parameters related to the evolution of pores according to the relevant data; Step S30, determining the analysis of the diagenetic stage of a reservoir, the main diagenetic types and the diagenetic evolution sequence of different diagenetic processes according to the relevant data; Step S40, calculating the initial porosity according to the quantitative parameters; Step S50, calculating the total porosity lost due to compaction; wherein: is the residual porosity after compaction of the reservoir; is the initial porosity; C is the compaction factor; Z is the burial depth; Step S60, calculating the total porosity lost due to calcareous, siliceous and clay cementation; where: W1is the clay cementation porosity reduction due to detrital origin; W x is the total clay content by X-ray diffraction; W n is the argillaceous matrix content identified by thin sections; c is the relative content of chlorite by X-ray diffraction; I is the relative content of illite by X-ray diffraction; I S is the relative content of illite-smectite mixed layer by X-ray diffraction; K is the relative content of kaolinite by X-ray diffraction; W (c) is the porosity reduction due to chlorite; W (I) is the porosity reduction due to illite; is the porosity reduction due to illite-smectite mixed layer; W (K) is the porosity reduction due to kaolinite; is the porosity reduction due to all cements; Step S70, calculating the total porosity increased due to dissolution; where: k is the relative amount of dissolution porosity; φ r k is the relative amount of dissolution porosity; φ t k is the relative amount of dissolution porosity; φ z k is the relative amount of dissolution porosity; φ n k is the relative amount of dissolution porosity; φ y k is the relative amount of dissolution porosity; φ j k is the relative amount of dissolution porosity; φ 4 is the relative amount of dissolution porosity; Step S80, calculating the total amount of transformation of kaolinite in the later stage; wherein: is the kaolinite content at the beginning of the transformation of kaolinite into other clay minerals; is the chlorite cementation after the beginning of the transformation of kaolinite into other clay minerals; is the illite cementation after the beginning of the transformation of kaolinite into other clay minerals; is the total thickness of the depth interval corresponding to the period of chlorite cementation until the beginning of the transformation of kaolinite into other clay minerals; is the total thickness of the depth interval corresponding to the period of chlorite cementation throughout the evolution stage; is the total thickness of the depth interval corresponding to the period of illite cementation until the beginning of the transformation of kaolinite into other clay minerals; is the total thickness of the depth interval corresponding to the period of illite cementation throughout the evolution stage; Step S90, calculating the porosity of the reservoir at different depths by taking the diagenetic evolution sequence of the reservoir, the burial history and the oil and gas charging period as constraints.

2. The method of claim 1, wherein the method is used to quantify the evolution of porosity in tight sandstone reservoirs with little fracture development. The relevant data include the powder particle size of the reservoir, X-ray diffraction, physical property testing, ordinary rock thin sections, rock cast thin sections and scanning electron microscopy.

3. The method of claim 2, wherein the method further comprises: The quantitative parameters include the Φ values corresponding to the cumulative particle content at 84%, 16%, 95% and 5% on the cumulative particle size curve, the porosity, the content of calcareous cement, the content of siliceous cement, the content of argillaceous matrix, the total pore area, the pore area of the cast mold, the intragranular dissolved pore area, the primary intergranular pore area, the intergranular dissolved pore area, the total clay content, the relative content of chlorite, the relative content of illite, the relative content of illite-smectite mixed layer and the relative content of kaolinite.

4. The method of claim 1, wherein, The calculation formula in step S90 is: wherein: Z is the burial depth; is the total thickness of the depth interval corresponding to the calcitic cementation period when the reservoir was buried to Z; is the total thickness of the depth interval corresponding to the calcitic cementation period throughout the entire evolutionary stage; is the total thickness of the depth interval corresponding to the silicic cementation period when the reservoir was buried to Z; is the total thickness of the depth interval corresponding to the silicic cementation period throughout the entire evolutionary stage; is the total thickness of the depth interval corresponding to the chlorite cementation period when the reservoir was buried to Z; is the total thickness of the depth interval corresponding to the chlorite cementation period throughout the entire evolutionary stage; is the total thickness of the depth interval corresponding to the illite cementation period when the reservoir was buried to Z; is the total thickness of the depth interval corresponding to the illite cementation period throughout the entire evolutionary stage; is the total thickness of the depth interval corresponding to the illite-smectite mixed-layer cementation period when the reservoir was buried to Z; is the total thickness of the depth interval corresponding to the illite-smectite mixed-layer cementation period throughout the entire evolutionary stage; is the total thickness of the depth interval corresponding to the kaolinite cementation period when the reservoir was buried to Z; is the total thickness of the depth interval corresponding to the kaolinite cementation period throughout the entire evolutionary stage; is the total thickness of the depth interval corresponding to the period of kaolinite conversion to other clay minerals when the reservoir was buried to Z; is the total thickness of the depth interval corresponding to the period of kaolinite conversion to other clay minerals throughout the entire evolutionary stage; is the total thickness of the depth interval corresponding to the dissolution period when the reservoir was buried to Z; is the total thickness of the depth interval corresponding to the dissolution period throughout the entire evolutionary stage; is the total thickness of the depth interval corresponding to the weak dissolution period when the reservoir was buried to Z; is the total thickness of the depth interval corresponding to the weak dissolution period throughout the entire evolutionary stage.

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