A method for studying the distribution law of tight sandstone sweet spot reservoirs

Abstract

The present invention relates to the field of reservoir evaluation, and specifically to a research method for the distribution law of tight sandstone sweet spot reservoirs, which includes the following steps: Step 1, based on the existing exploration data of the study area, determine the type of tight sandstone sweet spot reservoir, and the reservoir type is used to characterize the formation cause of reservoir pores; Step 2, according to the reservoir type determined in step 1, clarify the main controlling factors of tight sandstone sweet spot reservoir development; Step 3, according to the main controlling factor characteristics of tight sandstone sweet spots, establish a tight sandstone reservoir development model, determine the distribution law of tight sandstone sweet spot reservoirs, and the distribution law of tight sandstone sweet spot reservoirs is used to guide the distribution prediction of tight sandstone sweet spot reservoirs. The above-mentioned research method provided by the present invention is to establish a tight sandstone sweet spot reservoir development model and clarify the distribution law of tight sandstone sweet spot reservoirs under the premise of fully considering the causes of pore formation and development of tight sandstone sweet spot reservoirs, so as to guide the distribution prediction of tight sandstone sweet spot reservoirs.

Description

Technical Field

[0001] The invention relates to the field of reservoir evaluation, in particular to a method for studying the distribution law of tight sandstone sweet spot reservoirs. Background Art

[0002] Tight gas occupies an important position in oil and gas resources. Despite this, the exploration and development of tight gas reservoirs in China and related research are still in the exploratory stage, especially the search for "sweet spot" reservoir evaluation is the key and difficulty of tight gas reservoir exploration and development.

[0003] Previous studies have been conducted on the evaluation of tight sandstone "sweet spots". Yu Li (2014) believed that the key to finding "sweet spot" reservoirs is to find out the cause of low permeability. Based on the understanding of diagenetic phase distribution, reservoir thickness, and physical property distribution, the main controlling factors of low permeability and reservoir thickness and physical property differences were analyzed in detail through conventional physical properties, logging interpretation, and rock thin section analysis. Liu Chunyan (2015) divided "sweet spot" reservoirs into two categories: primary and secondary types according to their genetic types. Among them, the secondary "sweet spots" can be further divided into dissolution type and fracture type. The development of early chlorite film moderately inhibited the later diagenetic transformation, which is one of the important factors for the maintenance of the primary "sweet spots". First, various constructive diagenesis such as dissolution and fracturing are key factors in the formation of secondary "sweet spots". Zhu Xiaomin (2018) believed that the "sweet spots" in tight sandstone reservoirs mainly include two categories: one is a relatively concentrated development zone of abnormally high porosity reservoirs that are ultimately formed or retained after special geological actions and have a porosity higher than the maximum porosity under normal compaction conditions. Some scholars call it an "abnormally high porosity zone"; the other is a (micro) fracture development zone that is ultimately formed after special geological actions. The existence of fractures effectively increases the oil and gas storage space, enhances the reservoir pore communication and seepage capacity, and forms fracture-type effective oil and gas reservoirs.

[0004] Summarizing the previous research results, it can be seen that the previous results are mostly concentrated on the study of single factors affecting the physical properties of tight sandstone reservoirs, while the factors affecting the development of sweet spot reservoirs are relatively complex. Through the research in existing technologies, it is impossible to effectively guide the distribution prediction of tight sandstone sweet spot reservoirs. Summary of the invention

[0005] The purpose of the present invention is to provide a method for studying the distribution law of tight sandstone sweet spot reservoirs in view of the problems existing in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for studying the distribution law of tight sandstone sweet spot reservoirs comprises the following steps:

[0008] Step 1: Based on the existing exploration data of the study area, determine the reservoir type of the tight sandstone sweet spot, and the reservoir type is used to characterize the formation cause of the reservoir pores;

[0009] Step 2: According to the reservoir type determined in step 1, the main controlling factors of the development of tight sandstone sweet spot reservoir are clarified;

[0010] Step 3: According to the main controlling factor characteristics of tight sandstone sweet spots, a tight sandstone reservoir development model is established to determine the distribution law of tight sandstone sweet spot reservoirs, and the distribution law of tight sandstone sweet spot reservoirs is used to guide the distribution prediction of tight sandstone sweet spot reservoirs.

[0011] The above-mentioned research method provided by the present invention is to establish a development model of tight sandstone sweet spot reservoirs and clarify the distribution law of tight sandstone sweet spot reservoirs on the premise of fully considering the pore genesis and development main controlling factors of tight sandstone sweet spot reservoirs, so as to guide the distribution prediction of tight sandstone sweet spot reservoirs.

[0012] Sweet spot reservoirs refer to reservoirs with high mining value. With sufficient exploration data, the location and characteristics of sweet spot reservoirs can be determined. However, if the exploration data is insufficient, the distribution law of sweet spot reservoirs can be summarized based on the research method proposed in this application, and then the distribution location of sweet spot reservoirs can be predicted.

[0013] As an optional solution of the present invention, the reservoir type includes secondary dissolution type or primary type.

[0014] As an optional solution of the present invention, the main controlling factors for the development of the secondary dissolution type tight sandstone sweet spot reservoir include sedimentary environment, diagenesis and fracture development.

[0015] As an optional solution of the present invention, in step three, based on the existing exploration data of the study area, the development pattern of the tight sweet spot reservoir is classified according to the combination characteristics and sedimentary environment of the tight sandstone sweet spot reservoir.

[0016] As an optional solution of the present invention, the development modes of secondary dissolution type dense sweet spot reservoirs include the following five categories:

[0017] A1. The assemblage features that the top and bottom of the sandstone are adjacent to mudstone, and the middle part is thin interbedded sandstone. The sedimentary environment is a distributary channel or estuary bar with gradually weakening hydrodynamic conditions. There are sedimentary transition surfaces at the top and bottom of the sandstone.

[0018] A2. The assemblage features that the top and bottom of the sandstone are adjacent to mudstone, and the middle part is medium-thick or thick sandstone. The sedimentary environment is a distributary channel with strong hydrodynamic conditions, and there are sedimentary transition surfaces at the top and bottom of the sandstone;

[0019] B1. The assemblage features mudstone adjacent to the bottom of the sandstone and fine siltstone adjacent to the top, with medium-thick or thicker sandstone in the middle. The sedimentary environment is a multi-stage channel superposition with strong hydrodynamic conditions or a distributary channel with gradually weakening hydrodynamic conditions.

[0020] B2. The assemblage features sandstone adjacent to mudstone at the top, medium-thick sandstone in the middle, and fine siltstone at the bottom. The depositional environment is a distributary channel with strong hydrodynamic conditions.

[0021] C. The combination is characterized by fine siltstone calcareous layers at the top and bottom of the sandstone, medium-thick sandstone in the middle, and a sedimentary environment of multiple-stage river channel superposition with strong hydrodynamic conditions.

[0022] As an optional solution of the present invention, the sedimentary environment includes rock grain size and composition, the diagenesis includes compaction, cementation and dissolution, and the fracture development includes tectonic fractures and diagenetic pressure fractures.

[0023] As an optional solution of the present invention, in step one, the existing exploration data includes petrological characteristics, physical property characteristics and reservoir space type of the sweet spot reservoir.

[0024] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] The method provided by the present invention determines the main controlling factors for the development of tight sandstone sweet spot reservoirs, establishes a tight sandstone sweet spot reservoir development model, and clarifies the distribution law of tight sandstone sweet spot reservoirs on the basis of fully considering various factors such as tight sandstone sedimentary environment, diagenesis, and fracture development. The research results are of great guiding significance for the prediction of tight sandstone sweet spot reservoir distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of exploration data of the A1 type sweet spot reservoir model in an embodiment of the present invention.

[0027] Figure 2 It is a schematic diagram of exploration data of the A2 type sweet spot reservoir model in an embodiment of the present invention.

[0028] Figure 3 It is a schematic diagram of exploration data of a B1 type sweet spot reservoir model in an embodiment of the present invention.

[0029] Figure 4 It is a schematic diagram of exploration data of a B2 type sweet spot reservoir model in an embodiment of the present invention.

[0030] Figure 5 It is a schematic diagram of exploration data of a C-type sweet spot reservoir model in an embodiment of the present invention.

[0031] Figure 6 It is a schematic diagram of a method for studying the distribution law of tight sandstone sweet spot reservoirs provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Example

[0035] The present invention provides a method for studying the distribution law of tight sandstone sweet spot reservoirs. Figure 6 , which comprises the following steps:

[0036] Step 1: Based on the existing exploration data of the study area, determine the reservoir type of the tight sandstone sweet spot, and the reservoir type is used to characterize the formation cause of the reservoir pores;

[0037] Specifically, reservoir types include secondary dissolution type or primary type.

[0038] Further, in step 1, the sweet spot reservoir type is determined based on the basic characteristics of the tight sandstone reservoir.

[0039] The basic characteristics of a reservoir include its petrological characteristics, physical properties and reservoir space type.

[0040] Step 2: According to the reservoir type determined in step 1, the main controlling factors of the development of tight sandstone sweet spot reservoir are clarified;

[0041] For different types of reservoirs, the reasons for their formation are different, and the main controlling factors that play a leading role in the formation of the reservoirs are also different. It is necessary to analyze the main controlling factors that can affect the formation of the reservoir. Specifically, in this embodiment, the main controlling factors analyzed include sedimentary environment, diagenesis and fracture development.

[0042] Further, sedimentary environmental factors include rock grain size and composition. Diagenetic factors include compaction, cementation and dissolution. Fracture development factors include tectonic fractures and diagenetic pressure fractures.

[0043] Step 3: According to the main controlling factors of tight sandstone sweet spots, establish a tight sandstone reservoir development model and determine the distribution law of tight sandstone sweet spots. The distribution law of tight sandstone sweet spots is used to predict the distribution of tight sandstone sweet spots. That is, for areas with insufficient data, if their sedimentary environment, diagenesis and fracture development are similar to those of proven sweet spots, then the area can be considered as a sweet spot reservoir.

[0044] Based on the existing exploration data in the study area, the sedimentary environment, diagenesis and fracture development of the sweet spot reservoir in the study area are analyzed, so that the distribution law of the tight sandstone sweet spot reservoir in the area can be obtained. According to the obtained distribution law of the tight sandstone sweet spot reservoir, it can be used to predict the distribution of sweet spots in areas with insufficient data, thereby guiding the selection of exploration targets and improving the success rate of drilling targets.

[0045] The technical solution of the embodiment of the present invention is further described below in conjunction with a study example of a tight sandstone sweet spot reservoir in the Xu 3rd Member of the Western Sichuan Depression.

[0046] Some wells in the Xusan section of the western Sichuan Depression have relatively rich exploration data. The following steps are performed:

[0047] Step 1: Based on the existing exploration data of the study area, determine the reservoir type of the tight sandstone sweet spot, and the reservoir type is used to characterize the formation cause of the reservoir;

[0048] Specifically, based on the existing analytical data such as core properties, ordinary thin sections, cast thin sections, scanning electron microscopy, and X-ray diffraction, the petrological characteristics, physical properties and reservoir space types of the study area are determined.

[0049] Petrological characteristics include rock type, rock components and content, cement type and content, sorting and rounding, etc. The clastic components of the tight sandstone of Xusan Member in the western Sichuan Depression are mainly medium-coarse-grained feldspar lithic sandstone, lithic quartz sandstone and lithic sandstone, with a high feldspar content in the sandstone; cements mainly include carbonate minerals, authigenic silica and clay minerals, carbonate cements are mainly calcite, and a small amount of dolomite is seen; authigenic silica includes quartz secondary enlargement and intergranular filling authigenic quartz, which has a low content but is widely distributed; clay minerals are mainly hairy, filamentous illite and illite / montmorillonite mixed layers, and a small amount of chlorite is seen; sandstone is mainly medium-grained and fine-grained, with medium-poor grain rounding and medium-good sorting; the contact between particles is mainly line-concave-convex, followed by line contact, and the degree of compaction is strong.

[0050] The physical properties include porosity and permeability. The porosity of the Xusan sandstone in the western Sichuan Depression is generally less than 6%, mainly distributed in the range of 2-4%, with an average of 3.2%; the permeability is mainly 0.05-0.2mD, with an average of 0.1mD. There is a certain positive correlation between porosity and permeability. Overall, it belongs to the ultra-low porosity, low-ultra-low permeability fracture-pore type, pore-fracture type tight sandstone reservoir, and high permeability reservoirs with developed microcracks can be seen in some parts.

[0051] Reservoir space type: According to the observation results of core, cast thin section and scanning electron microscope, the pore types of sandstone in the Xusan Member of the Western Sichuan Depression are mainly intergranular solution pores, intragranular solution pores, clay mineral intercrystalline micropores, microcracks, etc., among which intergranular solution pores and cracks are dominant.

[0052] After the deposition of the Xusan Formation in the western Sichuan Depression, it experienced a rapid sedimentation process. The strong compaction caused the primary pores to decrease rapidly, and the residual intergranular pores were relatively rare, isolated, and small in diameter. The intergranular (intragranular) solution pores are mainly formed by the dissolution of feldspar, rock fragments, and early carbonate cements. Their formation is generally related to cracks. The pores are often filled with clay minerals such as illite, and intercrystalline micropores are developed. The types of cracks include interlayer cracks, intragranular cracks, grain edge cracks, cleavage cracks, etc., which are related to tectonic compression, differential compaction, and abnormally high pressure. They are widely distributed, and crack dissolution and expansion phenomena are common. Finally, it is determined that the reservoir type of the Xusan Formation in the western Sichuan Depression is mainly secondary dissolution type.

[0053] Step 2: According to the reservoir type determined in step 1, the main controlling factors of the development of tight sandstone sweet spot reservoir are clarified;

[0054] Since the reservoir type of the Xu 3rd Member in the western Sichuan Depression is mainly secondary dissolution type, the development of dissolution is the main mechanism of reservoir formation. The three factors of sedimentary environment, diagenesis, and fracture development will have a significant impact on the development of reservoirs. Therefore, the above three factors are the main controlling factors for the development of tight sandstone sweet spot reservoirs in the Xu 3rd Member of the western Sichuan Depression.

[0055] Specifically, from the perspective of sedimentary environment, the Xusan Section of the Western Sichuan Depression is mainly composed of delta and shallow lake sediments. Among them, the sandstones with strong hydrodynamics such as the delta plain distributary channel, the underwater distributary channel at the delta front and the estuary dam have coarse grain size, good sorting, low matrix content, good initial physical properties, low interstitial content, and relatively developed reservoirs. They are mainly distributed in the middle subsection of Xusan Section in the southern part of the Western Sichuan Depression. In addition, the formation mechanism of the tight sandstone sweet spot reservoir in the Xusan Section of the Western Sichuan Depression is the development of dissolution, and a key factor in the development of dissolution is the high content of soluble minerals. The feldspar content in the sandstone with good physical properties (porosity>3%) in the Xusan Section of the Western Sichuan Depression is generally greater than 10%. The sandstone in the middle subsection of Xusan Section in the southern part of the Western Sichuan Depression has a high feldspar content and a relatively developed reservoir.

[0056] From the perspective of diagenesis, rapid compaction in the early stage is the most important factor in the densification of the Xusan Member reservoir in the western Sichuan Depression. According to the statistics of compaction rate, the porosity loss caused by compaction exceeds 85% in the Xusan Member. Generally speaking, sandstone with coarse grain size, less matrix content, higher rigid mineral content, better particle sorting and moderate early carbonate cement has relatively weak compaction. The strong cementation of carbonate minerals, authigenic silica, etc. is an important reason for the densification of the reservoir. When the content of carbonate cement exceeds 10% and the content of authigenic silica exceeds 4%, the porosity is generally less than 3%. The Xusan Member belongs to the source rock system, which generally shows an acidic sedimentary and diagenetic environment. The content of carbonate cement is generally low, but when the sandstone has a fine grain size and a high content of calcareous rock debris, a calcareous dense layer (carbonate cement content>20%) can still be formed.

[0057] Dissolution can significantly improve the reservoir permeability. The dissolution of feldspar and other framework particles and intergranular carbonate cements in sandstone is relatively common, which has an important positive effect on the improvement of sandstone physical properties. Due to the strong compaction of the reservoir, the densification time is early, the fluidity of the acidic fluid is poor, and the intensity of dissolution is generally weak and uneven.

[0058] From the perspective of fracture development: fractures are crucial to the formation of the "sweet spot" reservoir of the tight sandstone of the Xu 3rd Member in western Sichuan. On the one hand, the fractures formed by fracturing can provide good acidic fluid migration channels for sandstone, which is conducive to the dissolution process. On the other hand, they can greatly improve the seepage capacity of low-porosity tight reservoirs. In areas with a high degree of deformation, tectonic fractures are most developed. At the same time, the combination of sand / mudstone interlayers is prone to dislocation and fracture caused by differential compaction, which is conducive to the formation of diagenetic fractures.

[0059] Therefore, the above three factors all have a significant impact on the development of the reservoir.

[0060] Step 3: According to the main controlling factor characteristics of tight sandstone sweet spots, a tight sandstone reservoir development model is established to determine the distribution law of tight sandstone sweet spot reservoirs, and the distribution law of tight sandstone sweet spot reservoirs is used to guide the distribution prediction of tight sandstone sweet spot reservoirs.

[0061] Based on the analysis of the main controlling factors of the development of the tight sandstone sweet spot reservoir in the Xu 3rd Member of the Western Sichuan Depression in step 2, the development model of the "sweet spot" reservoir in the Xu 3rd Member of the Western Sichuan Depression was established. There are three main types of tight sandstone sweet spot reservoir models in the Xu 3rd Member of the Western Sichuan Depression, which are:

[0062] like Figure 1 and Figure 2 , Type A, sandstone is adjacent to mudstone at both top and bottom;

[0063] like Figure 3 and Figure 4, Type B, the top or bottom of sandstone is adjacent to mudstone or silt-fine sandstone calcareous layer;

[0064] like Figure 5 , Class C, silt-fine sandstone calcareous layers are developed at the top and bottom of the sandstone.

[0065] Figure 1-5 Shown are the logging data corresponding to several different tight sandstone sweet spot reservoir modes.

[0066] In the figure, GR represents the natural gamma logging curve, RD represents the deep dual lateral resistivity logging curve, RS represents the shallow dual lateral resistivity logging curve, AC represents the sonic logging curve, CNL represents the compensated neutron logging curve, and DEN represents the compensated density logging curve.

[0067] Further, combined with sedimentary environmental factors, it can be divided into the following five types:

[0068] like Figure 1 A1. The combination features that the top and bottom of the sandstone are adjacent to mudstone, and the middle part is thin interbedded sandstone. The sedimentary environment is a distributary channel or estuary bar with gradually weakening hydrodynamic conditions. There are sedimentary conversion surfaces at the top and bottom of the sandstone.

[0069] like Figure 2 A2. The combination features that the top and bottom of the sandstone are adjacent to mudstone, and the middle part is medium-thick or thick sandstone. The sedimentary environment is a distributary channel with strong hydrodynamic conditions. There are sedimentary conversion surfaces at the top and bottom of the sandstone.

[0070] like Figure 3 B1. The combination characteristics are that the bottom of the sandstone is adjacent to mudstone, the top is adjacent to fine siltstone, the middle part is medium-thick or thick sandstone, and the sedimentary environment is a multi-stage channel superposition with strong hydrodynamic conditions or a distributary channel with gradually weakening hydrodynamic conditions;

[0071] like Figure 4 , B2. The assemblage features sandstone adjacent to mudstone at the top, medium-thick sandstone in the middle, and fine siltstone at the bottom. The depositional environment is a distributary channel with strong hydrodynamic conditions;

[0072] like Figure 5 , C. The combination is characterized by fine siltstone calcareous layers at the top and bottom of the sandstone, medium-thick sandstone in the middle, and a sedimentary environment of multiple-stage river channel superposition with strong hydrodynamic conditions.

[0073] It should be noted that the above terms such as "medium thickness" and "relatively strong" are relative standards in the geological environment of the same study area, rather than quantitative absolute standards. For example, in category B1, the thickness of sandstone is medium or relatively thick relative to other areas in the study area, and the relative conditions of the depositional environment are relatively strong or gradually weakening.

[0074] According to the development pattern of the tight sandstone sweet spot reservoirs of the Xu 3rd Member in the western Sichuan Depression, it can be seen that the tight sandstone sweet spot reservoirs of the Xu 3rd Member in the western Sichuan Depression are mainly distributed in the high-energy sand body deposition area of ​​the delta plain distributary channel, the delta front underwater distributary channel and the estuary bar in the southern part of the western Sichuan Depression, as well as the relatively high-value area of ​​feldspar and rock debris; vertically, the Xu 3rd Member sweet spot reservoirs are mainly distributed in the high-energy sand body adjacent to the mud shale in the middle sub-member of the Xu 3rd Member. According to the relationship between the logging porosity and the distance of the sandstone from the top and bottom mudstones, it can be seen that with the decrease in the distance from the top and bottom mudstones, the reservoir properties gradually improve, that is, the reservoirs are usually distributed in the high-energy sand body adjacent to the mud shale. On the one hand, the formation of fractures is conducive to the formation of cracks near the sand / mudstone lithology interface, which can provide channels for the migration of acidic fluids; on the other hand, the organic acids formed by the pyrolysis of organic matter in the mud shale enter the adjacent tight sandstone along the fractures formed in the early and middle Yanshan period, forming dissolution pores. At the same time, as the distance from the top calcareous dense layer increases, the reservoir porosity shows a trend of gradually increasing, reflecting that the calcareous interlayers developed at the top of the sandstone are conducive to the preservation of pores inside the sand body.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for studying the distribution law of tight sandstone sweet spot reservoirs, characterized in that: The following steps are involved: Step 1: Based on the existing exploration data of the study area, determine the reservoir type of the tight sandstone sweet spot, and the reservoir type is used to characterize the formation cause of the reservoir pores; The reservoir types include secondary dissolution type; Step 2: According to the reservoir type determined in step 1, the main controlling factors of the development of tight sandstone sweet spot reservoir are clarified; Step 3: According to the main controlling factor characteristics of the tight sandstone sweet spot, a tight sandstone reservoir development model is established to determine the tight sandstone sweet spot reservoir distribution law, and the tight sandstone sweet spot reservoir distribution law is used to guide the tight sandstone sweet spot reservoir distribution prediction; Based on the existing exploration data in the study area, the development patterns of tight sandstone sweet spot reservoirs are classified according to their combination characteristics and sedimentary environment. The development patterns of secondary dissolution-type tight sweet spot reservoirs include the following five categories: A1. The assemblage features that the top and bottom of the sandstone are adjacent to mudstone, and the middle part is thin interbedded sandstone. The sedimentary environment is a distributary channel or estuary bar with gradually weakening hydrodynamic conditions. There are sedimentary transition surfaces at the top and bottom of the sandstone. A2. The assemblage features that the top and bottom of the sandstone are adjacent to mudstone, and the middle part is medium-thick or thick sandstone. The sedimentary environment is a distributary channel with strong hydrodynamic conditions, and there are sedimentary transition surfaces at the top and bottom of the sandstone; B1. The assemblage features mudstone adjacent to the bottom of the sandstone and fine siltstone adjacent to the top, with medium-thick or thicker sandstone in the middle. The sedimentary environment is a multi-stage channel superposition with strong hydrodynamic conditions or a distributary channel with gradually weakening hydrodynamic conditions. B2. The assemblage features sandstone adjacent to mudstone at the top, medium-thick sandstone in the middle, and fine siltstone at the bottom. The depositional environment is a distributary channel with strong hydrodynamic conditions. C. The combination is characterized by fine siltstone calcareous layers at the top and bottom of the sandstone, medium-thick sandstone in the middle, and a sedimentary environment of multiple-stage river channel superposition with strong hydrodynamic conditions.

2. The method for studying the distribution law of tight sandstone sweet spot reservoir according to claim 1, characterized in that: The reservoir type also includes primary type.

3. The method for studying the distribution law of tight sandstone sweet spot reservoir according to claim 2, characterized in that: The main controlling factors for the development of the secondary dissolution type tight sandstone sweet spot reservoir include sedimentary environment, diagenesis and fracture development.

4. The method for studying the distribution law of tight sandstone sweet spot reservoirs according to claim 3 is characterized in that: The sedimentary environment includes rock grain size and composition, the diagenesis includes compaction, cementation and dissolution, and the fracture development includes tectonic fractures and diagenetic pressure fractures.

5. The method for studying the distribution law of tight sandstone sweet spot reservoirs according to claim 1, characterized in that: In step one, the existing exploration data include the petrological characteristics, physical property characteristics and reservoir space type of the sweet spot reservoir.

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