Complex tight sandstone gas reservoir horizontal well effective reservoir determination method and device

Abstract

The invention discloses a method and device for determining an effective reservoir of a complex tight sandstone gas reservoir horizontal well, and the method comprises the steps: judging the lithologic characteristics of a horizontal section of the horizontal well based on a GR curve while drilling of the complex tight sandstone gas reservoir horizontal well and a pre-calibrated natural gamma distinguishing threshold value; the gas content of the horizontal section of the horizontal well is judged based on the gas logging total hydrocarbon curve of the horizontal well, the gas well production dynamic data and pre-calibrated gas logging total hydrocarbon values of different types of stratum sections; and identifying the effective reservoir of the horizontal well of the complex tight sandstone gas reservoir based on the lithologic characteristics of the horizontal section of the horizontal well and the gas bearing property of the horizontal section of the horizontal well. The method fills the blank in the field of effective reservoir identification of the horizontal well, and aims at identifying the effective reservoir of the horizontal well of the pore and crack type complex tight sandstone gas reservoir, the effective reservoir of the horizontal well is identified by analyzing the GR while drilling and the gas logging total hydrocarbon curve of the horizontal section of the horizontal well and combining the production dynamic data of the gas well. The purposes of accurately evaluating the drilling effect of the horizontal well and scientifically guiding production are achieved.

Description

Technical Field

[0001] This invention relates to the field of gas field exploration and development technology, and in particular to a method and apparatus for determining the effective reservoir in a horizontal well of a complex tight sandstone gas reservoir. Background Technology

[0002] Tight sandstone gas reservoirs are an important type of unconventional gas reservoirs. They can be divided into two types according to their reservoir space: one type is where the reservoir space is mainly composed of pores; the other type is where the reservoir was strongly influenced by tectonic activity during its formation, resulting in well-developed fractures. Pores and fractures together constitute the reservoir space. Compared with porous gas reservoirs, the latter type of tight gas reservoirs are more complex.

[0003] Vertical wells are an important well type for the development of tight sandstone gas reservoirs. Taking a certain gas field as an example, vertical wells account for more than 80% of the development wells. Data acquisition from vertical wells is relatively convenient, generally with complete logging series, abundant core data, and sufficient experimental analysis data. Based on the analysis of lithology, electrical properties, physical properties, and gas-bearing properties, reservoir physical properties and gas-bearing properties are interpreted according to logging curves such as acoustic, density, neutron, and resistivity. Based on the interpretation results, core experimental data, and actual production data, the lower limit standards for effective reservoir physical properties and gas-bearing properties are determined. For example, in a certain basin, reservoirs with porosity greater than 5%, permeability greater than 0.1 mD, and gas saturation greater than 50% are generally identified as effective reservoirs.

[0004] Current research mainly focuses on the identification of effective reservoirs in porous tight gas reservoirs, with vertical wells being the primary well type. The gas reservoirs produce little or no water. The effective reservoir identification process is as follows:

[0005] 1) Establishment of the four properties of reservoir

[0006] The four properties of a reservoir are lithology, electrical properties, physical properties, and gas content. Lithology refers to the rock type of the reservoir; electrical properties refer to the response characteristics of the electrical logging curves; physical properties refer to the porosity and permeability characteristics of the reservoir; and gas content refers to the degree of natural gas saturation in the reservoir. The study of the relationship between these four properties involves systematic coring, laboratory experiments, and analysis of logging responses to qualitatively determine or quantitatively characterize the changes in logging curve morphology, physical properties, and the degree of natural gas saturation in a specific lithology.

[0007] 2) Determination of the lower limit of effective reservoirs

[0008] Tight sandstone gas reservoirs can be divided into effective reservoirs and ineffective reservoirs. Effective reservoirs are those where natural gas can both be stored and seep under current technological conditions; conversely, ineffective reservoirs or dry reservoirs are those where natural gas cannot be stored or seeps. The key to classifying effective reservoirs lies in clarifying their four key characteristics. For sandstone with poorly developed fractures, effective reservoir lithology is generally characterized by coarser grains, better physical properties, and higher gas saturation. Through comprehensive research of static geological data and dynamic production data, lower limits for porosity, permeability, and gas saturation are determined for reservoirs with industrial production capacity. Reservoirs exceeding these lower limits are considered effective reservoirs.

[0009] 3) Logging identification of effective reservoirs

[0010] Based on core wells, a study of the relationship between four properties (porosity, permeability, gas saturation, clay content, and logging interpretation data) was conducted to clarify the lower limits of effective reservoir properties and gas content. On this basis, an effective reservoir logging interpretation model was established (a model showing the correspondence between porosity, permeability, gas saturation, clay content, and logging interpretation data). The model was continuously optimized to ensure the logging interpretation accuracy met the required quality control standards. The optimized logging interpretation model was used to interpret the properties and gas content of wells without core wells. The logging interpretation results were then evaluated; those meeting the lower limit criteria for effective reservoirs were considered effective reservoirs, while those not meeting these criteria were considered ineffective reservoirs.

[0011] Based on the above analysis, it is evident that the aforementioned method requires relatively abundant dynamic and static data. Vertical wells have lower overall investment and yield more data, making the above method suitable for effective reservoir identification. This method is applicable to tight gas reservoirs where pores serve as storage spaces, but it does not consider tight gas reservoirs where fractures are a significant storage space. Summary of the Invention

[0012] Due to the limited data available from horizontal wells, identifying effective reservoirs in horizontal wells of complex tight sandstone gas reservoirs based on limited logging data is crucial. This helps to analyze the drilling results of horizontal wells, clarify the spatial distribution of effective reservoirs, and confirm the reliability of reserves, thereby enriching technical approaches and increasing the selection space. This invention provides a method and apparatus for determining effective reservoirs in horizontal wells of complex tight sandstone gas reservoirs.

[0013] In a first aspect, embodiments of the present invention provide a method for determining the effective reservoir in a horizontal well of a complex tight sandstone gas reservoir, which may include:

[0014] Based on the drilling GR curve of a horizontal well in a complex tight sandstone gas reservoir and the pre-calibrated natural gamma ray threshold, the lithological characteristics of the horizontal section of the horizontal well are determined.

[0015] Based on the total hydrocarbon curve of horizontal well gas logging, gas well production dynamic data, and pre-calibrated total hydrocarbon values ​​of different types of formations, the gas content of the horizontal section of the horizontal well is determined.

[0016] Based on the lithological characteristics and gas-bearing properties of the horizontal sections of horizontal wells, effective reservoirs in horizontal wells of complex tight sandstone gas reservoirs are identified.

[0017] In one embodiment, before determining the gas content of the horizontal section of a horizontal well, the method may further include: performing lithological characteristic analysis and gas content analysis on two typical gas wells with high and low production rates included in the complex tight sandstone gas reservoir, in order to calibrate the total hydrocarbon values ​​of gas-bearing sections of different types of formations.

[0018] In another embodiment, the lithological characteristic analysis and gas-bearing analysis of two typical gas wells with high and low production rates included in the complex tight sandstone gas reservoir, in order to calibrate the total hydrocarbon values ​​of gas-bearing sections of different types, may include:

[0019] Based on the mudstone and sandstone lithology of two typical gas wells, the natural gamma-ray logging curves of the two wells were calibrated to determine the natural gamma-ray distinguishing thresholds for different lithological formations. Specifically, the natural gamma-ray logging curves for formations dominated by mudstone and shale were greater than the first natural gamma-ray distinguishing threshold; the natural gamma-ray logging curves for formations dominated by siltstone and fine sandstone were less than the first natural gamma-ray distinguishing threshold but greater than the second natural gamma-ray distinguishing threshold; the natural gamma-ray logging curves for formations dominated by medium sandstone and coarse sandstone were less than the second natural gamma-ray distinguishing threshold; and the first natural gamma-ray distinguishing threshold was greater than the second natural gamma-ray distinguishing threshold.

[0020] The high-yield formation section in a high-yield gas well that is less than the second natural gamma threshold value is designated as a high-gas-content effective reservoir section, and the first gas-content total hydrocarbon value is calibrated based on the gas logging total hydrocarbon curve of the gas well corresponding to the high-gas-content effective reservoir section.

[0021] The formation segment with low production and greater than the first natural gamma ray threshold in the low-production gas well is designated as the low-gas-bearing dry layer segment, and the second gas-bearing total hydrocarbon value is calibrated based on the gas logging total hydrocarbon curve of the gas well corresponding to the low-gas-bearing dry layer segment; wherein, the first gas-bearing total hydrocarbon value is greater than the second gas-bearing total hydrocarbon value.

[0022] In another embodiment, determining the gas content of the horizontal section of a horizontal well based on the horizontal well gas logging total hydrocarbon curve, gas well production dynamic data, and pre-calibrated gas logging total hydrocarbon values ​​for different types of formations may include:

[0023] The gas logging total hydrocarbon curve of the horizontal well is verified based on the gas well production dynamic data, and the curve portion of the gas logging total hydrocarbon curve of the horizontal well corresponding to the gas production in the gas well is taken as the calibrable gas logging total hydrocarbon curve.

[0024] The gas content of the horizontal well section corresponding to the first gas total hydrocarbon value in the calibrable gas total hydrocarbon curve is judged as high gas content.

[0025] The gas content of the horizontal section of the horizontal well corresponding to the calibrable total hydrocarbon curve that is greater than the second total hydrocarbon value and less than the first total hydrocarbon value is judged as medium gas content.

[0026] The gas content of the horizontal well section corresponding to the second total hydrocarbon value in the calibrable gas logging curve is judged as low gas content.

[0027] In another embodiment, determining the lithological characteristics of the horizontal section of the horizontal well based on the drilling GR curve of a horizontal well in a complex tight sandstone gas reservoir and a pre-calibrated natural gamma ray threshold may include:

[0028] The lithological characteristics of the stratigraphic intervals in the drilling GR curve that are higher than the first natural gamma-ray threshold are taken as the stratigraphic intervals dominated by mudstone and shale.

[0029] The lithological characteristics of the strata that are lower than the first natural gamma threshold and higher than the second natural gamma threshold in the drilling GR curve are taken as strata that are mainly composed of siltstone and fine sandstone.

[0030] The lithological characteristics of the strata section corresponding to the second natural gamma threshold value in the drilling GR curve are taken as the strata section mainly composed of medium sandstone and coarse sandstone.

[0031] In another embodiment, identifying effective reservoirs in complex tight sandstone gas reservoirs based on the lithological characteristics and gas-bearing properties of the horizontal section of the horizontal well may include:

[0032] The horizontal well section with lithological characteristics corresponding to medium sandstone, coarse sandstone and / or siltstone, fine sandstone as the main strata, and the corresponding horizontal well section with high gas content and / or medium gas content, is considered as the effective reservoir of the horizontal well in the complex tight sandstone gas reservoir.

[0033] In another embodiment, before determining the lithological characteristics of the horizontal section of a horizontal well, the method may further include: pre-calibrating the natural gamma logging threshold based on the natural gamma logging curves of vertical wells in complex tight sandstone gas reservoirs and the lithology of mudstone and sandstone.

[0034] Secondly, embodiments of the present invention provide an apparatus for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir, which may include:

[0035] The lithological characteristic judgment module is used to judge the lithological characteristics of the horizontal section of the horizontal well based on the drilling GR curve of the horizontal well in the complex tight sandstone gas reservoir and the pre-calibrated natural gamma ray distinction threshold.

[0036] The gas content determination module is used to determine the gas content of the horizontal section of a horizontal well based on the total hydrocarbon curve of the horizontal well, the production dynamic data of the gas well, and the pre-calibrated total hydrocarbon values ​​of different types of formations.

[0037] The identification module is used to identify the effective reservoirs of horizontal wells in complex tight sandstone gas reservoirs based on the lithological characteristics and gas-bearing properties of the horizontal sections of the horizontal wells.

[0038] Thirdly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir as described in the first aspect.

[0039] Fourthly, embodiments of the present invention provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the method for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir as described in the first aspect.

[0040] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0041] This invention provides a method and apparatus for determining the effective reservoir in horizontal wells of complex tight sandstone gas reservoirs. This method fills a gap in the field of effective reservoir identification in horizontal wells. Specifically targeting the identification of effective reservoirs in horizontal wells of porous and fractured complex tight sandstone gas reservoirs, this method analyzes the only drilling GR and total hydrocarbon curves in the horizontal section of the horizontal well, and combines them with the dynamic production data of the gas well to establish a method for identifying effective reservoirs in horizontal wells. This achieves the purpose of accurately evaluating the drilling effect of horizontal wells and scientifically guiding production.

[0042] Furthermore, accurate identification of effective reservoirs in horizontal wells is a crucial geological task for gas field development. The aforementioned method, for identifying effective reservoirs in horizontal wells of complex tight sandstone gas reservoirs, has the following important objectives and significance: it helps to analyze the drilling results of horizontal wells, clarify the spatial distribution patterns of effective reservoirs, and confirm the reliability of reserves. At the same time, it helps to demonstrate the optimal length of the horizontal section and determine the reasonable production capacity of the horizontal well.

[0043] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0044] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0045] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0046] Figure 1 This is a flowchart of the method for determining the effective reservoir in a horizontal well of a complex tight sandstone gas reservoir provided in an embodiment of the present invention;

[0047] Figure 2 This is a flowchart illustrating a specific method for determining the effective reservoir in a horizontal well of a complex tight sandstone gas reservoir, as provided in this embodiment of the invention.

[0048] Figure 3 This is an example of the lithological characteristics of a porous effective reservoir, including drilling GR, gas logging total hydrocarbon curves, and other lithological features.

[0049] Figure 4 This is an example of lithological characteristics, including fractured effective reservoirs, dry layer drilling GR, and gas logging total hydrocarbon curves, provided in the embodiments of the present invention.

[0050] Figure 5 This is a schematic diagram of the structure of the device for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir provided in an embodiment of the present invention. Detailed Implementation

[0051] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0052] In practical work, the inventors discovered that for horizontal wells, due to limitations in investment costs and technical capabilities, the available geological data is very limited. Horizontal well logging curves only include drilling GR and total hydrocarbon logging curves, lacking data from coring and experimental analysis. Therefore, the methods used for vertical wells cannot be applied to interpret reservoir properties and gas content, hindering effective reservoir identification. There is an urgent need for a method to identify effective reservoirs in complex tight sandstone gas reservoirs using limited logging data in horizontal wells. In view of these problems, this invention is proposed to provide a method and apparatus for determining effective reservoirs in complex tight sandstone gas reservoirs in horizontal wells, overcoming or at least partially solving these problems.

[0053] This invention provides a method for determining the effective reservoir in a horizontal well of a complex tight sandstone gas reservoir, referring to... Figure 1 As shown, the determination method may include the following steps:

[0054] Step S11: Based on the drilling GR curve of a horizontal well in a complex tight sandstone gas reservoir and the pre-calibrated natural gamma ray threshold, determine the lithological characteristics of the horizontal section of the horizontal well.

[0055] Natural gamma curves in tight sandstone gas reservoirs have good indicative value for sandstone and mudstone. By establishing the correlation between natural gamma and logging lithology, the natural gamma distinction threshold (GR threshold value) for sandstone and mudstone can be clarified.

[0056] Step S12: Based on the horizontal well gas logging total hydrocarbon curve, gas well production dynamics data, and pre-calibrated gas logging total hydrocarbon values ​​for different types of formations, determine the gas content of the horizontal section of the horizontal well. In this step, the gas logging total hydrocarbon curve is key data for horizontal well gas content analysis. In the absence of conventional logging curves and the inability to interpret gas saturation, this embodiment of the invention comprehensively determines the gas content of the reservoir based on the gas logging total hydrocarbon curve and gas well production dynamics data.

[0057] It should be noted that the execution of steps S11 and S12 is not in any particular order. Step S11 can be executed first and then step S12, or step S12 can be executed first and then step S11, or steps S11 and S12 can be executed simultaneously. This embodiment of the invention does not impose any specific limitations on this.

[0058] Step S13: Based on the lithological characteristics and gas-bearing properties of the horizontal section of the horizontal well, identify the effective reservoirs of the horizontal well in complex tight sandstone gas reservoirs.

[0059] The method for determining the effective reservoir of horizontal wells in complex tight sandstone gas reservoirs provided in this embodiment fills the gap in the field of effective reservoir identification in horizontal wells. This method is aimed at identifying the effective reservoir of horizontal wells in complex tight sandstone gas reservoirs with porosity and fractures. By analyzing the only drilling GR and gas logging total hydrocarbon curves in the horizontal section of the horizontal well, and combining the gas well production dynamic data, a method for identifying the effective reservoir of horizontal wells is established, thereby achieving the purpose of accurately evaluating the drilling effect of horizontal wells and scientifically guiding production.

[0060] Furthermore, accurate identification of effective reservoirs in horizontal wells is a crucial geological task for gas field development. The aforementioned method, for identifying effective reservoirs in horizontal wells of complex tight sandstone gas reservoirs, has the following important objectives and significance: it helps to analyze the drilling results of horizontal wells, clarify the spatial distribution patterns of effective reservoirs, and confirm the reliability of reserves. At the same time, it helps to demonstrate the optimal length of the horizontal section and determine the reasonable production capacity of the horizontal well.

[0061] In one specific embodiment, the present invention also provides a detailed method for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir, referring to... Figure 2 As shown, the method may include the following steps:

[0062] Step S21: Based on the natural gamma logging curves of vertical wells in complex tight sandstone gas reservoirs and the lithology of mudstone and sandstone, pre-calibrate the natural gamma distinguishing boundary value.

[0063] In this embodiment of the invention, drawing on the analysis results of the reservoir property lower limits of vertical wells in the same block, the sandstone encountered in the horizontal section is subdivided to accurately determine the GR value characteristics of sandstones above and below the reservoir property lower limits. In specific implementation, the GR curves during drilling of the block are normalized, and the lithology logging and GR curves of horizontal wells in the study area are compared to determine the GR distinction value between sandstone and mudstone.

[0064] Generally speaking, sandstone with coarser grain size and better physical properties has a lower GR value, and the curve is box-shaped and relatively smooth. This type of sandstone reservoir has well-developed pores, and the reservoir properties are higher than the lower limit standard. If the natural gas saturation in the pores is high, an effective reservoir can be formed, and the gas well has good production capacity. Figure 3 Sandstones with finer grain size and poorer physical properties exhibit higher GR (Gross Retention Rate), with the curve showing strong sawtooth-like fluctuations. These sandstones have poor porosity development, reservoir properties below the lower limit standard, low natural gas storage capacity, and gas wells with no or very low production capacity. Figure 4 However, if the fracture system is well-developed and the fracture network has good storage and seepage capacity, such sandstone can also form effective reservoirs under conditions of high natural gas saturation.

[0065] In a specific example, taking the Shengbei Block of the Turpan-Hami Oilfield as an example, statistical analysis shows that the GR distinction threshold value for mudstone (including silty mudstone, mudstone, shale, etc.) and sandstone (including coarse sandstone, medium sandstone, fine sandstone, silty sand, argillaceous siltstone, etc.) is 115. That is, a GR value greater than 115 is mudstone and a GR value less than 115 is sandstone. The next step is to determine the physical properties of sandstone based on the GR value.

[0066] Step S22: Based on the drilling GR curve of a horizontal well in a complex tight sandstone gas reservoir and the pre-calibrated natural gamma ray threshold, determine the lithological characteristics of the horizontal section of the horizontal well.

[0067] In specific implementation of step S22 of this invention, firstly, the lithological characteristics of the strata corresponding to the first natural gamma ray threshold in the drilling GR curve that is higher than the first natural gamma ray threshold are identified as strata mainly composed of mudstone and shale; then, the lithological characteristics of the strata corresponding to the strata corresponding to the first natural gamma ray threshold but higher than the second natural gamma ray threshold in the drilling GR curve are identified as strata mainly composed of siltstone and fine sandstone; finally, the lithological characteristics of the strata corresponding to the second natural gamma ray threshold in the drilling GR curve are identified as strata mainly composed of medium sandstone and coarse sandstone.

[0068] Taking the above example, analysis revealed that coarser-grained sandstones with good physical properties generally have GR values ​​below 65, primarily consisting of fine-grained, medium-grained, and a small amount of coarse-grained sandstone. These reservoirs exhibit well-developed porosity, and their physical properties exceed the lower limit standard. Conversely, finer-grained sandstones with poor physical properties generally have GR values ​​above 65, primarily consisting of siltstone and fine-grained sandstone. These sandstones have poor porosity, and their reservoir physical properties fall below the lower limit standard. However, if the fracture system of these sandstones is well-developed, the reservoir physical properties can be significantly improved, and they can also become reservoirs. The key to this step is to determine sandstone physical properties based on the drilling GR curve, identifying reservoirs with good porosity and permeability above the lower limit and sand bodies with poor porosity and permeability below the lower limit in the horizontal section.

[0069] Step S23: Conduct lithological characteristic analysis and gas-bearing analysis on two typical gas wells with high and low production in the complex tight sandstone gas reservoir to calibrate the total hydrocarbon values ​​of gas measurements in different types of strata.

[0070] Specifically, in the implementation of step S23 of this embodiment, the natural gamma logging curves of the two typical gas wells are first calibrated based on the mudstone and sandstone lithology of the two wells to determine the natural gamma distinguishing threshold values ​​corresponding to different lithological formations. Specifically, the natural gamma logging curves corresponding to the mudstone and shale-dominated formations are greater than the first natural gamma distinguishing threshold value; the natural gamma logging curves corresponding to the siltstone and fine sandstone-dominated formations are less than the first natural gamma distinguishing threshold value but greater than the second natural gamma distinguishing threshold value; the natural gamma logging curves corresponding to the medium sandstone and coarse sandstone-dominated formations are less than the second natural gamma distinguishing threshold value. The natural gamma ray threshold is defined as follows: the first natural gamma ray threshold is greater than the second natural gamma ray threshold; then, the high-yield formation segment in a high-yield gas well that is less than the second natural gamma ray threshold is designated as a high-gas-bearing effective reservoir segment, and the first total hydrocarbon value is calibrated based on the total hydrocarbon curve of the gas well corresponding to this high-gas-bearing effective reservoir segment; finally, the low-yield formation segment in a low-yield gas well that is greater than the first natural gamma ray threshold is designated as a low-gas-bearing dry layer segment, and the second total hydrocarbon value is calibrated based on the total hydrocarbon curve of the gas well corresponding to this low-gas-bearing dry layer segment; wherein, the first total hydrocarbon value is greater than the second total hydrocarbon value.

[0071] In this embodiment of the invention, for high-yield gas wells, sandstone type analysis is performed based on the aforementioned method to determine the development of reservoirs with good physical properties, and to determine that the high-yield intervals are key to the well's success. Based on this, the characteristics of the total hydrocarbon curve values ​​for this type of interval are determined. Statistical analysis shows that the total hydrocarbon values ​​of reservoirs with good physical properties and high yields are typically greater than 10%. Figure 3 Similarly, for low-yield gas wells, the characteristic value of the total hydrocarbon curve in gas logging is typically less than 5%. Figure 4 Based on the above analysis, the gas content of the reservoir is determined. A total hydrocarbon content greater than 10% indicates high gas content, less than 5% indicates low gas content, and values ​​in between indicate medium gas content. Figure 4 ).

[0072] Step S24: Based on the total hydrocarbon curve of the horizontal well, the gas production dynamic data of the gas well, and the pre-calibrated total hydrocarbon values ​​of different types of formations, determine the gas content of the horizontal section of the horizontal well.

[0073] In its specific implementation, this step may include the following steps: First, verify the total hydrocarbon curve of the horizontal well based on the gas well production dynamic data, and take the part of the total hydrocarbon curve of the horizontal well corresponding to the gas production in the gas well as the calibrable total hydrocarbon curve; Second, determine the gas content of the horizontal section of the horizontal well corresponding to the first total hydrocarbon value in the calibrable total hydrocarbon curve as high gas content; Third, determine the gas content of the horizontal section of the horizontal well corresponding to the second total hydrocarbon value and the first total hydrocarbon value in the calibrable total hydrocarbon curve as medium gas content; Fourth, determine the gas content of the horizontal section of the horizontal well corresponding to the second total hydrocarbon value in the calibrable total hydrocarbon curve as low gas content.

[0074] In the specific implementation of step S24, the first step is to verify the total hydrocarbon curve of the horizontal well using the gas well production dynamic data. Only when natural gas is produced will this part of the total hydrocarbon curve of the corresponding horizontal well be used as the calibrable total hydrocarbon curve. If no natural gas is produced, even if the total hydrocarbon value of the corresponding horizontal well gas curve is high, it cannot be used to determine its gas content.

[0075] Step S25: Based on the lithological characteristics and gas-bearing properties of the horizontal sections of the horizontal well, identify the effective reservoirs of horizontal wells in complex tight sandstone gas reservoirs. Specifically, horizontal sections with medium-grained sandstone and / or siltstone and fine-grained sandstone as the main strata corresponding to the lithological characteristics of the horizontal sections of the horizontal well, and corresponding to horizontal sections with high and / or medium gas-bearing properties, are identified as effective reservoirs of horizontal wells in complex tight sandstone gas reservoirs.

[0076] In the specific implementation of this step, since the reservoir space can be divided into those dominated by pores and those dominated by fractures, there are two ways to identify the effective reservoir in a horizontal well, as detailed below:

[0077] 1) Identification of effective reservoirs where the reservoir space is mainly porosity

[0078] First, reservoirs with good physical properties are identified based on the characteristics of the GR curve. Then, based on the gas logging response, they are categorized into three types: high gas content, medium gas content, and low gas content. High and medium gas content reservoirs are considered effective reservoirs, with a high degree of natural gas filling in the reservoir pores. Gas wells have strong gas production capacity, a certain degree of stable production, and a relatively slow decline in production. They produce little or no water and are typically gas-bearing or water-bearing gas layers. Low gas content reservoirs are considered ineffective reservoirs, with formation water filling the reservoir pores and extremely low gas saturation. They are typically gas-bearing water layers or water layers, where gas wells produce large amounts of water but no gas.

[0079] 2) Identification of effective reservoirs whose storage space is mainly fractured

[0080] Firstly, sand bodies are identified based on GR curve characteristics. The main type is sandstone with poor porosity and relatively poor reservoir properties. Without fractures, these sandstones are essentially dry layers, primarily because natural gas cannot be stored due to the lack of porosity. However, with a well-developed fracture system, the fracture network itself possesses storage and seepage capabilities, making these sandstones potentially effective reservoirs.

[0081] Based on gas logging response, three types of reservoirs are defined: high gas content, medium gas content, and low gas content. High and medium gas content reservoirs are considered effective reservoirs, with a high degree of natural gas saturation in the fracture network system. Due to the favorable physical properties of the fracture system, gas and water exhibit some differentiation, resulting in relatively high water production. These reservoirs show strong initial gas production capacity but poor sustained production, exhibiting characteristics of high initial production followed by rapid decline. Compared to porous effective reservoirs, their water production is relatively high. Low gas content reservoirs are considered dry formations, primarily because fractures and pores are underdeveloped, preventing natural gas storage and resulting in poor gas content and no production capacity.

[0082] Taking the above example again, and referring to Table 1, in this embodiment of the invention, for reservoirs with a GR value less than 65 and good physical properties, the gas content and effective reservoir are determined by combining gas logging curves as follows:

[0083] ① If the total hydrocarbon gas content is >10%, it indicates that the reservoir pores are highly filled with natural gas, making it an effective porous reservoir section. Such reservoirs have high production capacity and low water production, with a water-to-gas ratio typically less than 5 cubic meters per 10,000 cubic meters.

[0084] ② If the total hydrocarbon gas content is between 5% and 10%, it indicates that the reservoir pores are moderately filled with natural gas, and some formation water is present in the pores, making it a water-bearing gas layer and a water-bearing porous type effective reservoir. This type of reservoir has moderate production capacity and relatively large water production, with a water-to-gas ratio typically of 5-10 cubic meters per 10,000 cubic meters.

[0085] ③ If the total hydrocarbon gas content is less than 5%, it indicates that the reservoir pores are poorly filled with natural gas and highly filled with formation water, classifying it as a gas-bearing water layer and an ineffective reservoir. Such reservoirs primarily produce water.

[0086] For reservoirs with GR values ​​greater than 65 and poor physical properties, the following analysis is conducted based on the total hydrocarbon logging curves to determine fracture development, gas content, and effective reservoir characteristics:

[0087] ① If the total hydrocarbon gas content is >10%, it indicates that the natural gas in the reservoir is sufficiently accumulated. Since the pores in this type of reservoir are not well-developed, the natural gas can only be stored in the fracture network system. Therefore, a high gas content in this type of reservoir usually indicates well-developed fractures, making it an effective fractured reservoir. This type of reservoir has high initial natural gas production, but poor stable production capacity and rapid decline. It also has high water production, with a water-to-gas ratio greater than 8 cubic meters per 10,000 cubic meters.

[0088] ② If the total hydrocarbon gas content is between 5% and 10%, it indicates that the reservoir has the capacity to store natural gas, suggesting the presence of fractures, but their development is not high, classifying it as an underdeveloped fractured effective reservoir. Such reservoirs generally have low natural gas production capacity and weak stable production, but also relatively high water production, with a water-to-gas ratio greater than 12 cubic meters per 10,000 cubic meters.

[0089] ③ If the total hydrocarbon gas content is less than 5%, it indicates that the fractures are not well developed. Such reservoirs are dry and have no production capacity; neither natural gas nor water is produced.

[0090] Table 1. Effective Reservoir Identification Table for Horizontal Wells in Complex Tight Gas Reservoirs

[0091]

[0092]

[0093] The method for determining the effective reservoir of horizontal wells in complex tight sandstone gas reservoirs provided in this embodiment of the invention can help analyze the drilling effect of horizontal wells, confirm the reliability of reserves, and, in combination with the effective reservoir length of horizontal wells, determine the reasonable production capacity of horizontal wells and predict the economics of gas well development.

[0094] For example, taking well A, a newly commissioned gas well in a tight sandstone condensate gas reservoir in the Turpan-Hami Basin, as an example, the horizontal section is 1150m long and the sandstone section is 932m long. If the effective reservoir cannot be identified, the drilling effect of the well cannot be judged, and the production capacity and economics cannot be predicted. Based on the above method, the effective reservoir section of the well is determined to be 672m (according to the abundance of reserves in the study area, when the effective horizontal section of a horizontal well exceeds 450m, it has good development effect). Therefore, it can be concluded that the drilling effect of this well is good, and the gas well should have good production capacity. Similarly, another newly commissioned well, well B, has a horizontal section length of 1240m and a sandstone section of 978m. The effective horizontal section of this well is determined to be 324m. Although the sand body is well-developed, the effective horizontal section of the horizontal well is too short, and the gas well production capacity should be low and the development risk is high.

[0095] Based on the same inventive concept, this invention also provides a device for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir, referring to... Figure 5 As shown, the device may include: a lithological characteristic judgment module 51, a gas content judgment module 52, and an identification module 53, and its working principle is as follows:

[0096] The lithological characteristic judgment module 51 is used to judge the lithological characteristics of the horizontal section of the horizontal well based on the drilling GR curve of the horizontal well in the complex tight sandstone gas reservoir and the pre-calibrated natural gamma ray distinction threshold.

[0097] The gas content determination module 52 is used to determine the gas content of the horizontal section of the horizontal well based on the total hydrocarbon curve of the horizontal well, the production dynamic data of the gas well, and the pre-calibrated total hydrocarbon values ​​of different types of formations.

[0098] The identification module 53 is used to identify the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir based on the lithological characteristics and gas content of the horizontal section of the horizontal well.

[0099] In an optional embodiment, refer to Figure 5 As shown, the above-mentioned device may further include: a calibration module 50, which is used to: perform lithological characteristic analysis and gas content analysis on two typical gas wells with high and low production in the complex tight sandstone gas reservoir, so as to calibrate the total hydrocarbon values ​​of gas measurements in different types of formations.

[0100] In another alternative embodiment, the calibration module 50 is specifically used for:

[0101] Based on the mudstone and sandstone lithology of two typical gas wells, the natural gamma-ray logging curves of the two wells were calibrated to determine the natural gamma-ray distinguishing thresholds for different lithological formations. Specifically, the natural gamma-ray logging curves for formations dominated by mudstone and shale were greater than the first natural gamma-ray distinguishing threshold; the natural gamma-ray logging curves for formations dominated by siltstone and fine sandstone were less than the first natural gamma-ray distinguishing threshold but greater than the second natural gamma-ray distinguishing threshold; the natural gamma-ray logging curves for formations dominated by medium sandstone and coarse sandstone were less than the second natural gamma-ray distinguishing threshold; and the first natural gamma-ray distinguishing threshold was greater than the second natural gamma-ray distinguishing threshold.

[0102] The high-yield formation section in a high-yield gas well that is less than the second natural gamma threshold value is designated as a high-gas-content effective reservoir section, and the first gas-content total hydrocarbon value is calibrated based on the gas logging total hydrocarbon curve of the gas well corresponding to the high-gas-content effective reservoir section.

[0103] The formation segment with low production and greater than the first natural gamma ray threshold in the low-production gas well is designated as the low-gas-bearing dry layer segment, and the second gas-bearing total hydrocarbon value is calibrated based on the gas logging total hydrocarbon curve of the gas well corresponding to the low-gas-bearing dry layer segment; wherein, the first gas-bearing total hydrocarbon value is greater than the second gas-bearing total hydrocarbon value.

[0104] In another optional embodiment, the gas content determination module 52 is specifically used for:

[0105] The gas logging total hydrocarbon curve of the horizontal well is verified based on the gas well production dynamic data, and the curve portion of the gas logging total hydrocarbon curve of the horizontal well corresponding to the gas production in the gas well is taken as the calibrable gas logging total hydrocarbon curve.

[0106] The gas content of the horizontal well section corresponding to the first gas total hydrocarbon value in the calibrable gas total hydrocarbon curve is judged as high gas content.

[0107] The gas content of the horizontal section of the horizontal well corresponding to the calibrable total hydrocarbon curve that is greater than the second total hydrocarbon value and less than the first total hydrocarbon value is judged as medium gas content.

[0108] The gas content of the horizontal well section corresponding to the second total hydrocarbon value in the calibrable gas logging curve is judged as low gas content.

[0109] In another optional embodiment, the lithological characteristic determination module 51 is specifically used for:

[0110] The lithological characteristics of the stratigraphic intervals in the drilling GR curve that are higher than the first natural gamma-ray threshold are taken as the stratigraphic intervals dominated by mudstone and shale.

[0111] The lithological characteristics of the strata that are lower than the first natural gamma threshold and higher than the second natural gamma threshold in the drilling GR curve are taken as strata that are mainly composed of siltstone and fine sandstone.

[0112] The lithological characteristics of the strata section corresponding to the second natural gamma threshold value in the drilling GR curve are taken as the strata section mainly composed of medium sandstone and coarse sandstone.

[0113] In another optional embodiment, the identification module 53 is specifically used to: identify the horizontal well section with medium sandstone and coarse sandstone as the main strata and / or siltstone and fine sandstone as the main strata, and the corresponding horizontal well section with high gas content and / or medium gas content as the effective reservoir of the horizontal well in the complex tight sandstone gas reservoir.

[0114] In another optional embodiment, the calibration module 50 is also used to: pre-calibrate the natural gamma logging threshold based on the natural gamma logging curves of vertical wells in complex tight sandstone gas reservoirs and the lithology of mudstone and sandstone.

[0115] Based on the same inventive concept, this embodiment of the invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-mentioned method for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir.

[0116] Based on the same inventive concept, this embodiment of the invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the above-mentioned method for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir.

[0117] The principles by which the above-mentioned devices, media, and related equipment in the embodiments of the present invention solve the problem are similar to those of the aforementioned methods. Therefore, their implementation can refer to the implementation of the aforementioned methods, and repeated details will not be repeated.

[0118] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage and optical storage) containing computer-usable program code.

[0119] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0120] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0121] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0122] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for determining the effective reservoir in a horizontal well of a complex tight sandstone gas reservoir, characterized in that, include: Based on the drilling GR curve of a horizontal well in a complex tight sandstone gas reservoir and the pre-calibrated natural gamma ray threshold, the lithological characteristics of the horizontal section of the horizontal well are determined. Based on the total hydrocarbon curve of horizontal well gas logging, gas well production dynamic data, and pre-calibrated total hydrocarbon values ​​of different types of formations, the gas content of the horizontal section of the horizontal well is determined. Based on the lithological characteristics and gas-bearing properties of the horizontal sections of horizontal wells, effective reservoirs in horizontal wells of complex tight sandstone gas reservoirs are identified.

2. The method according to claim 1, characterized in that, Before determining the gas content of the horizontal section of the horizontal well, the following steps are also taken: lithological characteristic analysis and gas content analysis are performed on two typical gas wells with high and low production rates in the complex tight sandstone gas reservoir to calibrate the total hydrocarbon values ​​of gas-bearing sections of different types of formations.

3. The method according to claim 2, characterized in that, The lithological characteristic analysis and gas-bearing analysis of two typical gas wells with high and low production rates included in the complex tight sandstone gas reservoir are performed to calibrate the total hydrocarbon values ​​of gas-bearing sections for different types of formations, including: Based on the mudstone and sandstone lithology of two typical gas wells, the natural gamma-ray logging curves of the two wells were calibrated to determine the natural gamma-ray distinguishing thresholds for different lithological formations. Specifically, the natural gamma-ray logging curves for formations dominated by mudstone and shale were greater than the first natural gamma-ray distinguishing threshold; the natural gamma-ray logging curves for formations dominated by siltstone and fine sandstone were less than the first natural gamma-ray distinguishing threshold but greater than the second natural gamma-ray distinguishing threshold; the natural gamma-ray logging curves for formations dominated by medium sandstone and coarse sandstone were less than the second natural gamma-ray distinguishing threshold; and the first natural gamma-ray distinguishing threshold was greater than the second natural gamma-ray distinguishing threshold. The high-yield formation section in a high-yield gas well that is less than the second natural gamma threshold value is designated as a high-gas-content effective reservoir section, and the first gas-content total hydrocarbon value is calibrated based on the gas logging total hydrocarbon curve of the gas well corresponding to the high-gas-content effective reservoir section. The formation segment with low production and greater than the first natural gamma ray threshold in the low-production gas well is designated as the low-gas-bearing dry layer segment, and the second gas-bearing total hydrocarbon value is calibrated based on the gas logging total hydrocarbon curve of the gas well corresponding to the low-gas-bearing dry layer segment; wherein, the first gas-bearing total hydrocarbon value is greater than the second gas-bearing total hydrocarbon value.

4. The method according to claim 3, characterized in that, The method of determining the gas content of the horizontal section of a horizontal well based on the horizontal well gas logging total hydrocarbon curve, gas well production dynamic data, and pre-calibrated gas logging total hydrocarbon values ​​of different types of formations includes: The gas logging total hydrocarbon curve of the horizontal well is verified based on the gas well production dynamic data, and the curve portion of the gas logging total hydrocarbon curve of the horizontal well corresponding to the gas production in the gas well is taken as the calibrable gas logging total hydrocarbon curve. The gas content of the horizontal well section corresponding to the first gas total hydrocarbon value in the calibrable gas total hydrocarbon curve is judged as high gas content. The gas content of the horizontal section of the horizontal well corresponding to the calibrable total hydrocarbon curve that is greater than the second total hydrocarbon value and less than the first total hydrocarbon value is judged as medium gas content. The gas content of the horizontal well section corresponding to the second total hydrocarbon value in the calibrable gas logging curve is judged as low gas content.

5. The method according to claim 1, characterized in that, The method of determining the lithological characteristics of the horizontal section of a horizontal well based on the drilling GR curve of a complex tight sandstone gas reservoir and a pre-calibrated natural gamma ray threshold includes: The lithological characteristics of the stratigraphic intervals in the drilling GR curve that are higher than the first natural gamma-ray threshold are taken as the stratigraphic intervals dominated by mudstone and shale. The lithological characteristics of the strata that are lower than the first natural gamma threshold and higher than the second natural gamma threshold in the drilling GR curve are taken as strata that are mainly composed of siltstone and fine sandstone. The lithological characteristics of the strata section corresponding to the second natural gamma threshold value in the drilling GR curve are taken as the strata section mainly composed of medium sandstone and coarse sandstone.

6. The method according to claim 1, characterized in that, The method of identifying effective reservoirs in complex tight sandstone gas reservoirs based on the lithological characteristics and gas-bearing properties of the horizontal sections of horizontal wells includes: The horizontal well section with lithological characteristics corresponding to medium sandstone, coarse sandstone and / or siltstone, fine sandstone as the main strata, and the corresponding horizontal well section with high gas content and / or medium gas content, is considered as the effective reservoir of the horizontal well in the complex tight sandstone gas reservoir.

7. The method according to any one of claims 1 to 6, characterized in that, Before determining the lithological characteristics of the horizontal section of a horizontal well, the following steps are also taken: based on the natural gamma logging curves of vertical wells in complex tight sandstone gas reservoirs and the lithology of mudstone and sandstone, the natural gamma ray threshold value is pre-calibrated.

8. A device for determining the effective reservoir in a horizontal well of a complex tight sandstone gas reservoir, characterized in that, include: The lithological characteristic judgment module is used to judge the lithological characteristics of the horizontal section of the horizontal well based on the drilling GR curve of the horizontal well in the complex tight sandstone gas reservoir and the pre-calibrated natural gamma ray distinction threshold. The gas content determination module is used to determine the gas content of the horizontal section of a horizontal well based on the total hydrocarbon curve of the horizontal well, the production dynamic data of the gas well, and the pre-calibrated total hydrocarbon values ​​of different types of formations. The identification module is used to identify the effective reservoirs of horizontal wells in complex tight sandstone gas reservoirs based on the lithological characteristics and gas-bearing properties of the horizontal sections of the horizontal wells.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the method for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir as described in any one of claims 1 to 7.

10. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the method for determining the effective reservoir of a horizontal well in a complex tight sandstone gas reservoir as described in any one of claims 1 to 7.

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