Carbonate condensate gas reservoir residual gas distribution pattern analysis method and device

Abstract

The invention relates to the technical field of oil and gas field development, in particular to a carbonate condensate gas reservoir residual gas distribution mode analysis method and device, and the method comprises the steps: S1, dividing different reservoir levels according to reservoir development modes and development structure levels; s2, establishing corresponding models according to different reservoir levels, and fusing the models of different levels to obtain a three-dimensional geologic model; s3, after the three-dimensional geologic model is coarsened, mathematical models of all single wells and well groups are established through digital simulation, and production history fitting is completed; and S4, according to a fitting result, obtaining a distribution mode of residual condensate gas of the fault-control carbonate condensate gas reservoir. By establishing a geologic model and utilizing a numerical simulation method, the distribution rule of the residual condensate gas of the carbonate condensate gas reservoir of the fault-control body is studied, main control factors of the residual condensate gas are defined, and effective theoretical guidance is provided for deeply knowing the characteristics of the type of reservoirs, tapping potential of the residual condensate gas and improving the recovery ratio of the condensate gas.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and particularly relates to a method and device for analyzing the remaining gas distribution pattern of carbonate condensate gas reservoirs. Background Art

[0002] Carbonate oil and gas reservoirs play an important role in the global oil and gas distribution. Their oil and gas reserves account for about 50% of the total global oil and gas reserves, and their oil and gas production reaches more than 60% of the total global oil and gas production. The fractured-vuggy carbonate oil reservoirs (fractured-vuggy oil reservoirs) in China are mainly distributed in the Tarim Basin. The total proven geological oil reserves of Tahe Oilfield, Lungu Oilfield, Halaha Tang Oilfield, Fuman Oilfield, Shunbei Oil and Gas Field, etc. have exceeded 20×10^8 t, which is the most realistic replacement field for oil and gas exploration and development.

[0003] The Shunbei area is mainly dominated by fault-controlled bodies. Research work has been carried out around the No. 4 Shunbei zone, and a strike-slip fault zone core structure and a clustered development mode of fault-controlled reservoirs have been proposed; the interior of the reservoir is divided into a breccia zone and a fracture zone, forming a unique "grid cluster" mode in the Shunbei area. The fault-controlled body is the main reservoir part of the strike-slip fault system. The karstification inside the fault-controlled body is generally weak. The reservoir spaces are mainly the cross-section cavities formed by fault fractures, the pores between breccias, and structural fractures, etc., and the three are interconnected. Their scale is small, and the reservoir heterogeneity is strong. The strike-slip fault zone has experienced multiple tectonic movements, and the stress environment is complex. The fracture patterns formed under different stress conditions vary greatly. Therefore, the fault-controlled reservoir shows a segmented characteristic in the horizontal direction. The tectonic stress in the northern section of the No. 4 Shunbei zone is mainly tensile stress, the tectonic stress in the middle section is mainly tensile stress and tectonic translation, and the tectonic stress in the southern section is mainly compressive stress. The special sieve cluster mode and the horizontally segmented structure make the exploitation of carbonate condensate gas reservoirs in this area more difficult.

[0004] At present, the condensate gas in the No. 4 Shunbei fault zone is mainly exploited by methods such as depletion, natural gas injection, nitrogen injection, etc. Of course, drilling and fracturing are also important means for exploiting condensate gas reservoirs. However, due to the lack of in-depth research on the remaining condensate gas distribution of fault-controlled carbonate condensate gas reservoirs, it is difficult to provide effective theoretical guidance for the development of fault-controlled carbonate condensate gas, resulting in low recovery degree, low recovery rate, fast bottom water advancement in the bottom holes of some production wells, the risk of water flooding, and the problem of rapid decline of formation pressure, which has been affecting the production. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiency that the research on the remaining condensate gas distribution of fault-controlled carbonate condensate gas reservoirs in the prior art has been insufficient and it is difficult to provide effective theoretical guidance for the development of fault-controlled carbonate condensate gas, and to provide a method and device for analyzing the remaining gas distribution pattern of carbonate condensate gas reservoirs.

[0006] To achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0007] A method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir, comprising the following steps:

[0008] S1: Divide different reservoir levels according to the reservoir development pattern and the development structural level;

[0009] S2: Establish corresponding models according to different reservoir levels, and fuse the models of different levels to obtain a three-dimensional geological model;

[0010] S3: After coarsening the three-dimensional geological model, establish mathematical models for each individual well and well group by numerical simulation to complete the production history matching;

[0011] S4: Obtain the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir according to the fitting results.

[0012] By adopting the above technical solutions, through establishing a geological model and using the method of numerical simulation, the distribution law of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir is studied, its main controlling factors are clarified, and effective theoretical guidance is provided for deeply understanding the characteristics of this type of reservoir, tapping the potential of the remaining condensate gas, and improving the condensate gas recovery rate.

[0013] As a preferred solution, step S1 includes: establishing a reservoir development pattern by using seismic data, drilling data, cores, well logs and lost circulation and blowout records, as well as the structural position, reservoir body type and spatial contact relationship.

[0014] As a preferred solution, step S1 further includes: dividing the fault-controlled reservoir into five levels, namely the strike-slip fault zone, the fault-controlled body, the fracture body - karst-like cave - chaotic body, the internal filling of the karst-like cave, and the microfractures, according to the reservoir development pattern and the development structural level, and determining the corresponding threshold truncation for each level by using the deterministic modeling method.

[0015] As a preferred solution, establishing the corresponding models according to different reservoir levels in step S2 includes: the strike-slip fault wave is mainly characterized by the fault-controlled body, and the fault-controlled body is composed of a fracture body, a karst-like cave and a chaotic body. Therefore, the structure tensor, the coherent energy gradient and the variance seismic attribute body are respectively used to characterize it, and the corresponding threshold is determined by the well-seismic combination method to establish the contour models of the fracture body, the karst-like cave and the chaotic body;

[0016] Taking the contour model of the karst-like cave as a constraint, a three-dimensional model of the internal grid cluster structure is established layer by layer by using the object-based modeling method;

[0017] For the microfractures, an improved discrete fracture network simulation method is adopted to establish a microfracture network model that conforms to the actual morphology in the outcrop.

[0018] As a preferred solution, step S3 further includes: establishing mathematical models of individual wells and well groups through reservoir numerical simulation for production history matching.

[0019] As a preferred solution, step S4 includes: generating a pressure change fitting graph based on the pressure fitting before and after production, comparing the pressure change fitting graph, and clarifying the distribution law of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, where the distribution law includes distribution characteristics and distribution types.

[0020] As a preferred solution, based on the distribution characteristics and distribution types of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, clarify the main controlling factors for the distribution of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, and obtain the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir.

[0021] As a preferred solution, the distribution types of the remaining condensate gas in individual wells include isolated type, structure-controlled type, sealing plugging type, and bottom water plugging type.

[0022] As a preferred solution, the distribution types of the remaining condensate gas in well groups include isolated type, retention type near gas drive channels, and injection-production relationship-controlled type.

[0023] On the other hand, a device for analyzing the distribution pattern of remaining condensate gas in fault-controlled carbonate rocks is provided. Program instructions are stored in the device for analyzing the distribution pattern of remaining condensate gas in fault-controlled carbonate rocks. When the program instructions are executed by at least one processor, they are used to implement a method for analyzing the distribution pattern of remaining gas in a carbonate condensate gas reservoir as described in any one of the above.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] Through the established three-dimensional geological model, after reasonable coarsening, using the method of reservoir numerical simulation, mathematical models of individual wells and well groups are established to complete production history matching. The distribution law of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir is clarified through the fitting results, and the main controlling factors for its distribution are clarified. Then, according to the main controlling factors, the distribution pattern of the remaining gas in the fault-controlled carbonate condensate gas reservoir is divided, providing technical support for the subsequent exploitation of such condensate gas, and providing effective theoretical guidance for deeply understanding the characteristics of this type of reservoir and the potential tapping of the remaining condensate gas and improving the condensate gas recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0027] Figure 1 Flow chart of a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 1;

[0028] Figure 2 Tectonic location map of the Shunbei No. 4 zone in the Tarim Basin for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0029] Figure 3 Stratigraphic development characteristics map of the Shunbei oil and gas field for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0030] Figure 4 Screen cluster structure pattern map of the fault-controlled body in the Shunbei oil and gas field for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0031] Figure 5 Lateral segmentation pattern map of the Shunbei No. 4 zone for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0032] Figure 6 Single-well energy coherence map and well location map of the Shunbei 43X well group for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0033] Figure 7 Well location map of the Shunbei No. 4 fault zone for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0034] Figure 8 3D geological model map of the southern section of the Shunbei No. 4 zone for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0035] Figure 9 Mathematical model map of the SHB43X well group for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0036] Figure 10 Single-well remaining gas distribution characteristic map of the Shunbei No. 4 zone for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0037] Figure 11 Well group remaining gas distribution characteristic map of the Shunbei No. 4 zone for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0038] Figure 12 Remaining gas distribution pattern map of the fault-controlled carbonate condensate gas reservoir for a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir described in Example 2;

[0039] Figure 13 This is a structural diagram of an analysis device for the remaining condensate gas distribution pattern in fault-controlled carbonate rocks according to Embodiment 3 of the present invention. Detailed implementation manners

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0041] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used for distinguishing descriptions, and cannot be understood as indicating or implying relative importance, or implying any such actual relationship or order between these entities or operations. In addition, the terms "connected", "connected", etc. can be directly connected between components, or indirectly connected through other components.

[0042] Embodiment 1

[0043] This embodiment discloses a method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir, as Figure 1 shown, including the following steps:

[0044] S1: Divide different reservoir levels according to the reservoir development pattern and the development structural level;

[0045] Specifically, step S1 includes: establishing a reservoir development pattern by using seismic data, drilling data, cores, logging and lost circulation and blowout records, as well as the structural location, reservoir body type and spatial contact relationship.

[0046] Step S1 further includes: dividing the fault-controlled reservoir into five levels: strike-slip fault zone, fault-controlled body, fracture body - cave-like - chaotic body, internal filling of cave-like body, and microfractures according to the reservoir development pattern and the development structural level, and determining the corresponding threshold truncation for each level by using the deterministic modeling method.

[0047] S2: Establish corresponding models according to different reservoir levels, and fuse the models of different levels to obtain a three-dimensional geological model;

[0048] The establishment of corresponding models according to different reservoir levels described in step S2 includes: The strike-slip fault wave is mainly characterized by fault-controlled bodies, which are composed of fractured bodies, pseudo-caves, and chaotic bodies. Therefore, structural tensors, coherent energy gradients, and variance seismic attribute volumes are respectively used to characterize them, and the corresponding thresholds are determined in a well-seismic combination manner to establish contour models of fractured bodies, pseudo-caves, and chaotic bodies;

[0049] Taking the contour model of the pseudo-cave as a constraint, a three-dimensional model of the internal grid cluster structure is established layer by layer using the object-based modeling method;

[0050] For the microfractures, an improved discrete fracture network simulation method is adopted to establish a microfracture network model that conforms to the actual morphology in the field outcrop.

[0051] S3: After coarsening the three-dimensional geological model, a mathematical model of each single well and well group is established using numerical simulation to complete the production history matching;

[0052] Step S3 also includes: Establishing a mathematical model of each single well and well group through reservoir numerical simulation for production history matching.

[0053] S4: Obtain the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir according to the fitting results.

[0054] Step S4 includes: Generating a pressure change fitting diagram according to the pressure fitting before and after production, comparing the pressure change fitting diagram, and clarifying the distribution law of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, where the distribution law includes distribution characteristics and distribution types;

[0055] Specifically, according to the distribution characteristics and distribution types of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, clarify the main controlling factors for the distribution of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir to obtain the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir.

[0056] The distribution types of the remaining condensate gas in the single well include isolated type, structure-controlled type, sealing and plugging type, and bottom water plugging type.

[0057] The distribution types of the remaining condensate gas in the well group include isolated type, retention type near the gas drive channel, and injection-production relationship-controlled type.

[0058] Example 2

[0059] This example is a specific implementation manner of Example 1;

[0060] Taking Shunbei No. 4 as an example: Carbonate rock oil and gas reservoirs play an important role in the global oil and gas distribution. Their oil and gas reserves account for about 50% of the world's total oil and gas reserves, and their oil and gas production reaches more than 60% of the world's total oil and gas production. China's fractured-vuggy carbonate rock oil reservoirs (fractured-vuggy oil reservoirs) are mainly distributed in the Tarim Basin. The total proven geological oil reserves of Tahe Oilfield, Lungu Oilfield, Halaha Tang Oilfield, Fuman Oilfield, Shunbei Oil and Gas Field, etc. have exceeded 2×10^9 t, making it the most realistic replacement area for oil and gas exploration and development.

[0061] The Shunbei area is mainly composed of fault-controlled bodies. By carrying out research work around the Shunbei No. 4 zone, a strike-slip fault zone core structure and a fault-controlled reservoir cluster development model are proposed; the interior of the reservoir is divided into a breccia zone and a fracture zone, forming a unique "grid cluster" model in the Shunbei area. The fault-controlled body is the main reservoir part of the strike-slip fault system. The karstification inside the fault-controlled body is generally weak. The reservoir spaces are mainly the cross-section cavities formed by fault fractures, the pores between breccias, and structural fractures, etc. The three are interconnected. Their scale is small and the reservoir heterogeneity is strong. The strike-slip fault zone has experienced multiple tectonic movements with a complex stress environment, and the fracture styles formed under different stress conditions vary greatly. Therefore, the fault-controlled reservoir shows a segmented characteristic in the horizontal direction. The tectonic stress in the northern section of the Shunbei No. 4 zone is mainly tensile stress, the tectonic stress in the middle section is mainly tensile stress and tectonic translation, and the tectonic stress in the southern section is mainly compressive stress. The special sieve cluster model and the horizontally segmented structure make the exploitation of carbonate rock condensate gas reservoirs in this area more difficult.

[0062] The Shunbei No. 4 zone belongs to a fault-controlled carbonate rock condensate gas reservoir. A condensate gas reservoir is a complex and special gas reservoir between an oil reservoir and a gas reservoir. During the development process, hydrocarbon gases exist in the form of gas underground. When produced to the surface, due to the change of temperature and pressure, the phenomenon of liquid petroleum condensation will occur, and this kind of oil is called condensate oil. According to the state equation of real condensate gas and the recoverable reserves, a functional relationship between the recovery degree of recoverable reserves in the formation and the formation pressure is established. The distribution of the recovery degree of recoverable reserves during the exploitation process is used to replace the distribution of the formation pressure, realizing the quantitative description of the remaining gas distribution; the distribution patterns of remaining oil in fractured-vuggy oil reservoirs are divided, and potential tapping suggestions are given for different distribution patterns; through carrying out condensate gas pressure depletion experiments and collaborating with micro-computer tomography technology, based on the images scanned by micro-computer tomography and a series of calculation and analysis, the quantitative characterization of condensate oil reserves and positions in different stages of the condensate gas reservoir is obtained. By combining core displacement experiments and nuclear magnetic resonance technology, the microscopic distribution law of remaining gas in carbonate rock gas reservoirs is studied, further improving the understanding of the remaining gas distribution and providing a basis for improving the recovery factor of this type of gas reservoir.

[0063] At present, many foreign scholars have proposed numerous new methods and new applications in the research on carbonate condensate gas reservoirs. By analyzing the physical properties of hydrocarbon gases in the condensate gas field in Albania, the types and properties of reservoir fluids are determined, including physical and chemical properties, which play a key role in many decisions made in oil and gas field development in reservoir engineering. Based on mathematical modeling, the separation process of hydrocarbon phases during the depletion of condensate gas reservoirs and the production of retrograde condensate gas reservoirs is studied. An effective method for producing retrograde condensate oil is found to be the water injection method. The saturation-pressure relationship and multiphase pseudo-pressure calculation for the production of retrograde condensate gas reservoirs under boundary-dominated flow are improved, providing technical support for the exploitation of condensate gas reservoirs with retrograde condensation. The software is used to simulate the condensate gas reservoir fluid. Four samples of nitrogen, carbon dioxide, methane, and separator gas are injected into the condensate gas reservoir respectively, and the effects of changing the injection rate, injection pressure, and injection duration on the recovery factor of the condensate gas reservoir are investigated, providing a theoretical basis for the subsequent production of condensate gas. A comprehensive model is established to conduct the production study of the condensate gas reservoir, reproduce the decline rate of reservoir pressure and productivity, and calculate the production level of hydrocarbons considering the existing risks, providing support for the exploitation of the condensate gas reservoir. The hydrodynamic simulation is used to select the development mode of the oil and gas condensate gas reservoir, providing a new method for the selection of the development mode of the condensate gas reservoir. The artificial intelligence technology is used to predict the performance of the constant-volume depletion test of the condensate gas reservoir, improving the accuracy of pressure-volume-temperature (PVT) data in the development process of the condensate gas reservoir. By introducing a modified compressibility parameter into the traditional FMB equation, an accurate estimation of the initial in-place gas and average reservoir pressure of non-volume-type naturally fractured condensate gas reservoirs is achieved, providing a new method for the subsequent research on the dual-porosity model. The grouped data processing method is applied to predict the permeability of heterogeneous carbonate condensate gas reservoirs, providing important support for the research on condensate gas reservoirs. Through the pore-scale analysis of gas injection in the condensate gas reservoir, it is recognized that C2 and CO2 are the most effective gases for removing the accumulated condensate gas and re-establishing gas flow, providing a theoretical basis for re-establishing gas flow in the condensate gas reservoir in the later stage.

[0064] The Shunbei No. 4 fault zone is controlled by large strike-slip faults and developed multiple small strike-slip faults. Affected by multiple tectonic movements, it forms a typical fault-controlled reservoir body. Compared with conventional reservoirs, there are fracture zones in the vertical direction of the fault-controlled reservoir body, resulting in high-permeability channels in the vertical direction. However, there is a dense bedrock barrier in the direction perpendicular to the fault plane, resulting in poor connectivity in the direction perpendicular to the fault plane, which is the proposed sieve cluster structure. Previous studies on the remaining gas distribution in condensate gas reservoirs have ranged from theoretical to quantitative research, from depletion development to water injection for pressure stabilization, and then to gas injection huff and puff, natural gas injection, nitrogen injection and other methods. However, there is still no systematic classification of the remaining condensate gas distribution patterns in carbonate condensate gas reservoirs, leaving a blank in this field. In particular, the research on the remaining gas distribution law of the current popular fault-controlled fracture-cavity carbonate condensate gas reservoirs still lacks a systematic understanding. Therefore, it is particularly important to study the remaining gas distribution law of fault-controlled carbonate condensate gas reservoirs, clarify its main controlling factors, and divide the remaining gas distribution patterns of fault-controlled carbonate condensate gas reservoirs.

[0065] At present, the condensate gas in the Shunbei No. 4 fault zone is mainly produced by depletion, natural gas injection, nitrogen injection and other methods. Of course, drilling and fracturing are also important means for producing condensate gas reservoirs. However, the current production degree is not high and the recovery rate is low. The bottom water of some production wells advances relatively fast, with the risk of water flooding, and the problem of rapid decline in formation pressure has always affected the production progress. However, the research on the remaining condensate gas distribution in fault-controlled carbonate condensate gas reservoirs has been insufficient, making it difficult to provide effective theoretical guidance for the development of fault-controlled carbonate condensate gas. Therefore, the author will take the fault-controlled carbonate condensate gas reservoir in the No. 4 fault zone of the Shunbei Oilfield as an example, establish a geological model, and use the method of reservoir numerical simulation to study the remaining gas distribution law of fault-controlled carbonate condensate gas reservoirs, clarify its main controlling factors, in order to provide guidance for deeply understanding the characteristics of such reservoirs and the potential tapping of remaining condensate gas and improving the recovery rate of condensate gas.

[0066] Geological overview:

[0067] 1. Regional geological characteristics of the Shunbei oil and gas field

[0068] The main body of the Shunbei Oilfield in the Tarim Basin is located in the Shuntuoguole low uplift, extending southeast to the Shunnan slope of the Guchengxu uplift, connecting with the Shaya uplift in the north, contacting with the Kata uplift in the south, adjacent to the Manjiaer depression in the east, and contacting with the Awati depression in the west. The Shuntuoguole low uplift has experienced multiple complex sedimentary tectonic evolutions, providing good geological conditions for the development of multiple fracture-cavity reservoirs and the accumulation of oil and gas. The Shuntuoguole low uplift is located in the center of the Tarim Basin and is less affected by the orogenic activities on the basin margin. It is a first-level tectonic unit with relatively stable tectonic activities in the Tarim Basin (as Figure 2 shown).

[0069] 2. Lithological characteristics of the study area

[0070] In the Shunbei area, the Ordovician strata are well developed. From bottom to top, they are the Lower Ordovician Penglaiba Formation, Yingshan Formation, Yijianfang Formation, Qiaerbake Formation and Que'erquequn Group (as Figure 3 shown).

[0071] The lithology of the Penglaiba Formation is mainly platform facies dolomite and calcareous dolomite. The Yingshan Formation belongs to the Middle-Lower Ordovician strata and is fully developed in the Shuntuogole Low Uplift area. The main lithologies developed in this horizon are yellow-gray micritic limestone, sandy micritic limestone, and dark gray micritic limestone. The Yijianfang Formation belongs to the Middle Ordovician strata and is conformably in contact with the underlying Yingshan Formation. It gradually thins or pinches out southward in the eastern part of the study area, with a thickness of about 160 m. Its lithology is yellow-gray micritic limestone, sandy micritic limestone containing sand debris, and sandy micritic limestone. The Qiaerbake Formation belongs to the Upper Ordovician and is unconformably in contact with the underlying Yijianfang Formation. This formation can be roughly divided into upper and lower parts. The upper part is brownish or reddish-brown calcareous mudstone, and the lower part is yellow-gray micritic limestone. The lithology of the Lianglitage Formation is mainly gray and light gray micritic limestone or sandy micritic limestone. The lithology of the Sangtamu Formation is mainly gray and dark gray mudstone and calcareous mudstone.

[0072] The condensate gas reserves in the No. 4 strike-slip fault zone in Shunbei are relatively high. The condensate gas reservoirs in the entire No. 4 Shunbei zone are distributed along the No. 4 strike-slip fault zone in Shunbei. The Lower Cambrian Yurtus Formation is the main source rock. The fault extends vertically along the condensate gas reservoir in the No. 4 Shunbei zone, so the fault connectivity is strong. At the same time, the formation is broken to form caves, cavity cross-sections, and fractures formed along with the fault, etc., which become good reservoir spaces for oil and gas. It is crucial to clarify the distribution of condensate gas reservoirs in the reservoir space of the entire No. 4 Shunbei zone for the exploitation of the No. 4 Shunbei zone.

[0073] 3. Reservoir characteristics of fault-controlled bodies

[0074] The carbonate rock series of the Middle Ordovician Yijianfang Formation and the Middle-Lower Ordovician Yingshan Formation are the main target layers in the Shunbei oil and gas field. The Shuntuogole Low Uplift has been in a relatively low structural position for a long time. Karstification of the top surfaces of the Yijianfang Formation and the Lianglitage Formation is underdeveloped, and there are no karst fracture-cavity type reservoirs formed by karstification similar to those in the Tahe Oilfield. However, during multiple tectonic movements, various small-scale strike-slip fault zones have developed in the Shunbei oil and gas field. The carbonate rocks of the Yijianfang Formation - Yingshan Formation are fractured, forming a unique type of fault-controlled fracture-cavity type reservoir mainly due to the multi-stage activities of strike-slip faults. Its effective reservoir space is mainly composed of fault cavities, fractures, etc. Research shows that the study area is a fault-controlled fracture-cavity type reservoir body controlled by large strike-slip fault zones. According to the hierarchical classification of fault-controlled fracture-cavity type reservoirs, they are sequentially divided into five levels from the development level: strike-slip fault zone, fault-controlled body, fracture body - pseudo-cave - disordered body, filling inside the pseudo-cave, and micro-fractures. The higher levels have a restrictive and controlling effect on the lower levels, as shown in Table 1:

[0075]

[0076]

[0077] Table 1: Hierarchical Feature Table

[0078] The fault-controlled reservoir in Shunbei Oil and Gas Field develops in the ultra-deep layer with a burial depth greater than 7200m. It is a special type of reservoir formed due to the development of strike-slip faults. The fault-controlled reservoir is distributed in a strip along the strike-slip fault zone. Multiple sets of fracture-cave aggregates - sieve cluster structures are developed in the direction perpendicular to the fault zone, which are composed of the bedrock - fracture zone - cave zone - fracture zone - bedrock zone arranged in an orderly manner, as Figure 4 shown.

[0079] The condensate gas reservoir in the No. 4 zone of Shunbei is mainly distributed along the No. 4 strike-slip fault in Shunbei. The No. 4 strike-slip fault zone in Shunbei has experienced multiple tectonic movements, and the stress environment is complex. The fracture patterns formed under different stress conditions vary greatly. Therefore, the fault-controlled reservoir shows the characteristic of being segmented laterally. The northern section of the No. 4 zone in Shunbei is mainly under tensile stress, the middle section is mainly under tensile stress and tectonic translation, and the southern section is mainly under compressive stress, Figure 5 shown.

[0080] The tectonic stress of the SHB43X well group in the northern section of the No. 4 zone in Shunbei is weak compressive stress. Combining the coherent energy gradient maps of wells SHB43X, SHB4-9H, and SHB4-6H and the well location map of this well group, as Figure 6 shown, it can be known that the condensate gas reservoir in this well group is distributed along the strike-slip fault of the No. 4 fault in Shunbei. Combining the well location distributions of all production wells and injection wells in the condensate gas reservoir of the No. 4 fault zone in Shunbei, it can be known that the condensate gas reservoir in the entire No. 4 fault zone in Shunbei presents a strip shape and is distributed along the No. 4 strike-slip fault zone in Shunbei.

[0081] 4. Development Characteristics

[0082] The No. 4 zone in Shunbei is 60 km long and 1.5 km wide. The daily oil production is 2237 tons, the daily gas production is 4.48 million cubic meters, the comprehensive water cut is 6.5%, the dynamic reserves of condensate gas are 16 billion cubic meters, the dynamic reserves of condensate oil are 7.91 million tons, the cumulative oil production at this stage is 253,000 tons, the cumulative gas production is 469 million cubic meters, the recovery factor of condensate oil is 3.1%, and the recovery factor of condensate gas is 2.9%. The original formation pressure in the No. 4 zone in Shunbei is 88.4 MPa, the current average formation pressure is 61.8 MPa, and the pressure maintenance degree is 70%.

[0083] The unit is divided into 4 multi-well units (9 wells) and 10 single-well units. Among them, the multi-well units include the SHB43X well group (SHB43X and SHB4-6H wells are production wells, and SHB4-9H well is an injection well), the SHB44X well group (both SHB44X and SHB4-14H are production wells), the SHB45X well group (SHB45X and SHB4-11H are production wells), and the SHB46X well group (SHB46X is a production well, and SHB-8H is an injection well); the single-well units include: SHB4-5H, SHB4-4H, SHB4-7H, SHB41X, SHB4-1H, SHB4-2H, SHB4-3H, SHB47X, SHB4-12H, and SHB4-13H, a total of ten single wells, as Figure 7 shown.

[0084] 5. Establishment of three-dimensional geological model

[0085] Make full use of seismic data, drilling data, cores, logging, and lost circulation and blowout records. According to the structural location, reservoir type, and spatial contact relationship, establish a reservoir development model; based on the reservoir development model, divide different reservoir levels according to the structural hierarchy. According to the hierarchical division method, divide the fault-controlled reservoir into five levels: strike-slip fault zone, fault-controlled body, fracture body - pseudo-cave - chaotic body, internal filling of pseudo-cave, and microfractures. For different levels, use the deterministic modeling method to determine their threshold cutoffs; the strike-slip fault has a wide range of influence and it is difficult to determine its boundary. Therefore, mainly focus on the characterization of the fault-controlled body. The fault-controlled body is composed of fracture body, pseudo-cave, and chaotic body. Therefore, use structural tensor, coherent energy gradient, and variance seismic attribute volume to characterize it respectively, and determine the appropriate threshold in the way of well-seismic combination to establish the contour models of fracture body, pseudo-cave, and chaotic body. Taking the pseudo-cave contour model as a constraint, adopt an improved object-based modeling method to establish a three-dimensional model of internal grid cluster structure layer by layer. For microfractures, adopt an improved discrete fracture network simulation method to establish a microfracture network model that includes conjugate fractures, curved fractures, etc., which conforms to the actual morphology in the field outcrop. Integrate the models of different levels according to the priority to obtain the three-dimensional geological model of the Shunbei No. 4 fault zone, as Figure 8 shown, providing a three-dimensional geological model data volume for numerical simulation research. Based on the established physical property model, calculate the reserves of the study area. The condensate gas reserves in the Shunbei No. 4 fault zone of the study area are about 170×10^8 m^3, and the dynamic reserves of the study area are about 160×10^8 m^3. The difference between the condensate gas reserves of the physical property model and the dynamic reserves is 10×10^8 m^3, and the fitting error rate is 6.25%. Therefore, the established geological model can truly represent the actual geological storage situation and can well guide the subsequent numerical simulation work.

[0086] 6. Numerical simulation

[0087] At present, the problems existing in the production of the No. 4 fault zone in the Shunbei Oilfield are as follows: the recovery rate of production wells is not high, the recovery rate is on the low side, the bottom water of some production wells rises relatively fast, there is a risk of water flooding, and the formation pressure drops relatively fast. To solve the above problems, clarify the distribution of the remaining condensate gas in the carbonate condensate gas reservoir, study its distribution law, and summarize and divide the distribution pattern of the remaining condensate gas in such condensate gas reservoirs, so as to provide guidance for the exploitation of the remaining gas in the fault-controlled carbonate condensate gas reservoir in the future. Through the established three-dimensional geological model, after reasonable coarsening, the numerical simulation method is used to establish the mathematical models of each single well and well group, such as Figure 9 shown, complete the production history matching, clarify the distribution law of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir through the matching results, clarify the main controlling factors of its distribution, and then divide the distribution pattern of the remaining gas in the fault-controlled carbonate condensate gas reservoir according to its main controlling factors, so as to provide technical support for the exploitation of such condensate gas in the future.

[0088] The No. 4 fault zone in Shunbei is divided into three regions: the northern section, the middle section and the southern section, with a total of 14 unit blocks divided. For the well group / single well division, the coarse grid size is 4×50×50. As of October 2023, the cumulative fitting degree is greater than 96%, and the average fitting degree is 98.69%, which provides a strong guarantee for the subsequent distribution characteristics of the remaining condensate gas and makes the subsequent research work more realistic and credible, as shown in Table 2

[0089]

[0090]

[0091] Table 2 Fitting situation of each unit in the No. 4 fault zone in Shunbei

[0092] The production degree of production wells is not high, the recovery rate is on the low side, the bottom water of some production wells advances relatively fast, there is a risk of water flooding, and the formation pressure drops fast. To solve the above problems and clarify the distribution position and distribution pattern of the remaining gas in the condensate gas reservoir, this paper uses the method of reservoir numerical simulation to conduct production history matching on all wells (well groups) in the condensate gas reservoir of the No. 4 zone in Shunbei, and clarify the distribution characteristics of the remaining gas in the condensate gas reservoir of the No. 4 zone in Shunbei.

[0093] Distribution characteristics of remaining gas in single well:

[0094] Well SHB4-4H is located in the northern section of the No. 4 fault zone in Shunbei. The well-controlled area belongs to the tensile section. Under the action of tectonic stress, the model moves backward, and the middle of the two fault planes is filled with dense bedrock; According to the production pressure change fitting diagram (such as Figure 10As shown in Figure a), Well SHB4-4H is a horizontal well. The well trajectory of this well passes through a fault plane on one side and contacts the fault plane on the other side. Although this well penetrates one side of the fault, due to the filling of the dense bedrock, the condensate gas reservoir in the fault block reservoir on one side of this well has not been exploited. Only the condensate gas in the fault block reservoir on the other side has been exploited, and the unexploited condensate gas forms residual condensate gas controlled by tectonic stress.

[0095] Well SHB4-5H is located in the northern section of Shunbei No. 4 Zone, and the well-controlled area belongs to the translational section; according to the fitting graph of production pressure changes (as shown in Figure 10 Figure b), most of the model of this well is connected to the main fault plane. Under the action of tectonic stress, there is scattered unexploited condensate gas around the model.

[0096] Well SHB4-7H is located in the middle section of Shunbei No. 4 Zone, and the well-controlled area belongs to the compression section. According to the fitting graph of production pressure changes (as shown in Figure 10 Figure c), most of the model of this well is connected to the main fault plane. Under the action of tectonic stress, there is scattered unexploited condensate gas gathering around the model.

[0097] Well SHB4-2H is located in the middle section of Shunbei No. 4 Zone, and the well-controlled area of this well belongs to the tensile section. According to the fitting graph of production pressure changes (as shown in Figure 10 Figure d), most of the model of this well is connected to the main fault plane. Under the action of tectonic stress, there is scattered unexploited condensate gas around the model.

[0098] Well SHB41X is located in the middle section of Shunbei No. 4 Zone, and the well-controlled area belongs to the tensile section. According to the fitting graph of production pressure changes (as shown in Figure 10 Figure e), the well trajectory of this well passes through two fault planes. Due to the filling of dense bedrock, the well trajectory is not connected to the right fault plane shown in the picture. The pressure of the right fault plane basically does not change in the later stage of fitting, and the condensate gas is not exploited, forming residual gas controlled by tectonic stress. At the same time, due to the tensile stress, part of the reservoir is broken, and there is scattered unexploited condensate gas around the two fault planes.

[0099] Well SHB4-1H is located in the southern section of Shunbei No. 4 Zone, and the well-controlled area belongs to the tensile section. According to the fitting graph of production pressure changes (as shown in Figure 10 Figure f), most of the model of this well is connected to the main fault plane, and there is scattered unexploited condensate gas around the fault plane.

[0100] Well SHB4-3H is located in the southern section of Shunbei No. 4 Zone, and the well-controlled area belongs to the tensile section. According to the fitting graph of production pressure changes (as shown in Figure 10 Figure g), most of the model of this well is connected to the main fault plane, and there is a little scattered unexploited condensate gas at the top of the model.

[0101] Well SHB47X is located in the southern section of Shunbei Block 4. The well control area belongs to the compression uplift section. According to the fitting diagram of production pressure change (as shown in Figure 10 Figure h), the well trajectory of this well contacts the right fault surface and the left fault surface as shown in the picture. However, due to the filling of dense bedrock between the right fault surface and the well trajectory, the well trajectory is not connected to the right fault surface. Condensate gas accumulates in the right fault surface, forming residual condensate gas controlled by tectonic stress.

[0102] Well SHB4-12H is located in the southern section of Shunbei Block 4. The well control area belongs to the extrusion section. Through production history matching with reservoir numerical simulation software, according to the fitting diagram of pressure change before and after production (as shown in Figure 10 Figure j), this well is a horizontal well. The well trajectory passes through the left fault surface. There is bedrock filling between the left fault surface and the right fault surface. Therefore, at present, only the condensate gas in the reservoir body of the left fault surface can be produced from this well, and the condensate gas in the reservoir body of the right fault surface is rich. According to the gas saturation map of this well (as shown in Figure 10 Figure i), the bottom water of this well rises rapidly, forming a water cone at the bottom of the well, blocking the bottom of the production well, and the remaining condensate gas in the formation cannot be produced.

[0103] Well SHB4-13H is located in the southern section of Shunbei Block 4. The well control area belongs to the strike-slip - pull-apart section. The formation is affected by strike-slip stress and pull-apart stress, and the degree of formation fragmentation is relatively high, forming reservoir bodies of different sizes. Moreover, each reservoir body is filled with dense bedrock and is not connected to each other. According to the fitting diagram of production pressure change (as shown in Figure 10 Figure k), within the well control range of this well, due to the filling of dense bedrock, all the reservoir bodies in the whole model are not all connected together. This well can only produce a part of the condensate gas, and most of the condensate gas is not produced, forming residual condensate gas controlled by tight plugging.

[0104] Distribution characteristics of remaining gas in well groups:

[0105] The SHB43X well group is located in the northern section of the Shunbei No. 4 fault zone. The well group includes wells SHB43X, SHB4-6H, and SHB4-9H. Among them, well SHB4-9H is an injection well, and the other two wells are production wells. The regional tectonic stress of the SHB43X well group belongs to weak compressive stress, and the entire cross-section model is basically an integral whole. Through production history matching using reservoir numerical simulation software, according to the pressure change fitting comparison chart before and after production, it can be seen that all three wells in this well group have passed through this cross-section model. There is a partial area with relatively high pressure above well SHB4-6H. The reservoir body in this area is not connected to the main fault surface, and this part of the condensate gas has not been utilized and exists scattered in the formation. In the well group, well SHB4-9H initially injects natural gas to displace condensate gas. After the natural gas enters the formation, it diffuses. Since the density of natural gas is lower than that of condensate gas, the natural gas will migrate upward, and then gradually displace the condensate gas in the upper part towards the production well, and then make the condensate gas accumulate around the production well (as shown in Figure 11 Figure a); if nitrogen is injected to displace condensate gas, the density of nitrogen is greater than that of condensate gas. After nitrogen enters the formation, it will deposit towards the bottom of the formation, and then displace the condensate gas at the bottom of the reservoir body towards the production well, making the condensate gas concentrated around the production well (as shown in Figure 11 Figure b).

[0106] The SHB44X well group is located in the northern section of the Shunbei No. 4 fault zone. The well group includes two wells, SHB44X and SHB4-14H. Both wells in this well group are production wells, and the well group area belongs to the tensile segment. During the actual production process, the production pressure responses of the two wells are obvious, and the connectivity between the two wells is good. According to the production pressure fitting comparison chart at the initial production stage and the current stage (as shown in Figure 11 Figure c), as production progresses, the pressure of the main reservoir body gradually decreases, but in some areas outside the main cross-section, the pressure of some reservoir bodies changes little. It is inferred that the connectivity between this part of the reservoir body and the main cross-section is poor and exists alone in the formation. Although it is within the well control range, it cannot be utilized and is scattered in the formation.

[0107] The SHB45X well group is located in the northern section of the Shunbei No. 4 zone. The well group includes two wells, SHB45X and SHB4-11H. The well group area belongs to the tensile segment; according to the production pressure fitting comparison chart at the initial production stage and the current stage (as shown in Figure 11 Figure d), there are some scattered reservoir bodies with relatively high pressure around the main fault surface in the well group area, scattered around the model. Although it is within the well control range, it cannot be utilized.

[0108] The SHB46X well group is located in the middle section of the Shunbei No. 4 zone. The well group includes two wells, SHB46X and SHB4-8H. The well group area belongs to the translational section. The entire cross-section model is basically a whole, with very little scattered condensate gas. Among them, the SHB46X well is a production well, and the SHB4-8H well is an injection well. According to the production history fitting of the gas saturation streamline map (as shown in Figure 11 as shown in e) and the numerical simulation permeability model (as shown in Figure 11 as shown in f), there is an extremely permeable gas drive channel in this well group. However, the permeability is very small in the upper part of the channel and is blocked, and the internal condensate gas is not utilized, forming a stagnant condensate gas near the gas drive channel.

[0109] Distribution pattern of remaining gas in fault-controlled carbonate condensate gas reservoirs:

[0110] To clarify the distribution law of the remaining gas in the fault-controlled carbonate condensate gas reservoir and make its distribution systematic and accurate, this paper uses reservoir numerical simulation, combined with logging and seismic data, to analyze the remaining gas distribution in the mathematical model, summarizes and analyzes the distribution characteristics of the remaining gas in each single well and well group in the Shunbei No. 4 zone, and divides the distribution pattern of the remaining gas in the fault-controlled carbonate condensate gas reservoir into two major categories, namely single-well remaining gas and well-group remaining gas; specifically subdivided into 7 subcategories, as shown in Table 3:

[0111]

[0112]

[0113] Table 3 Distribution categories of remaining gas in fault-controlled carbonate condensate gas reservoirs

[0114] Distribution pattern of single-well remaining gas:

[0115] 1. Isolated type

[0116] According to the actual geological data and dynamic and static data, the closer to the main fault zone, the more developed the Ordovician carbonate fault-controlled reservoir, and the better the connectivity between the fault-controlled reservoir and the deep major fault, and the more sufficient the oil and gas injection. On the contrary, the farther away from the main fault zone, the weaker the development degree of the fault-controlled carbonate reservoir, the reservoir space is mainly isolated caves, the connectivity between the reservoir and the source fault is poorer, and the oil and gas injection degree is weaker. The remaining gas in this part is isolated and enriched in the reservoir space far from the main fault plane, such as SHB4-2H, SHB4-7H, etc. It can be clearly seen that there are some modules with higher pressure around the main cross-section model and they are not connected to the main cross-section, and the remaining gas is enriched. The reason is that due to the sealing of the dense bedrock, some reservoir bodies are not connected to the main cross-section. This part of the remaining condensate gas is called isolated type remaining gas (as shown in Figure 12 as shown in a).

[0117] 2. Tectonic stress control type

[0118] The strike-slip fault influence zone is segmented under the influence of stress differences and can be subdivided into compression segments, tensile segments, and translational segments. The Shunbei No. 4 fault zone is a large strike-slip fault zone. The strike-slip fault zone has experienced multiple tectonic movements, and the stress environment is complex. The fracture patterns formed under different stress conditions vary greatly, so the fault-controlled reservoir shows lateral segmentation characteristics. When the tectonic stress on the strike-slip fault is tensile stress, it causes the two fracture planes on both sides to move away from the fracture plane, and the two fracture planes gradually move apart, forming a "V" shape. At the same time, the part between the two fracture planes is filled with bedrock, which hinders the migration of oil and gas. Finally, the formed reservoir body is mainly distributed along the two fracture planes, and the reservoir bodies on the two fracture planes are mostly not connected. It is very difficult for condensate gas to move from one side of the fracture plane to the other side. The condensate gas in the reservoir body on one side of the fracture plane is produced, while the condensate gas in the reservoir body on the other side is not utilized (as shown in Figure 12 Figure b), such as SHB41X, SHB47X, etc. The reservoir bodies are distributed on both sides of the fracture plane, and the middle is filled and sealed by bedrock. Only a part of the condensate gas can be utilized during the production of the opened well.

[0119] On the contrary, when the tectonic stress is compressive stress or the stress along the Shunbei No. 4 fault zone is translational stress, the model is relatively compact, the reservoir bodies are connected to each other, and often a large reservoir body is formed. During the production process of the opened well, most of the condensate gas can be utilized. For example, in wells SHB4-3H and SHB4-7H, the reservoir body is basically a whole, and only a small part of the isolated remaining gas around it cannot be utilized.

[0120] 3. Tight-sealing type

[0121] Due to the vertical stratification characteristics of the carbonate fault-controlled reservoir in the fault-controlled body, the remaining gas that is not produced and is tightly blocked in the lower part of the tight section in the fault-controlled body. The reservoir bodies of the carbonate fault-controlled condensate gas reservoir are formed by the superposition of multiple tectonic movements. There are certain differences in the depths of each tectonic movement, so there are multiple sets of fault-controlled bodies vertically. There is a certain thickness of tight sections, that is, bedrock or pore-fracture reservoirs with poor permeability, between each set of fault-controlled bodies. When the reservoir body is subjected to tensile stress, the two fracture planes move away from each other along the direction perpendicular to the fracture plane, and the space between the fracture planes is filled with tight bedrock. Then, under the action of translational stress, the two fracture planes move away from each other along the fracture plane, and the degree of formation fracture increases. The fractured reservoir bodies are blocked by tight bedrock, resulting in some condensate gas not being utilized. The model of well SHB4-13H in the Shunbei No. 4 fault zone is relatively dispersed, mainly because it is affected by both tensile stress and translational stress, which increases the degree of formation fracture. The tight bedrock blocks, resulting in the distribution of each reservoir body around the main fracture plane, and there is no large pore channel connecting between each reservoir body. After the production of well SHB4-13H, only the condensate gas in the reservoir body drilled through is utilized, and the condensate gas in other reservoir bodies forms tight-sealing type remaining gas, as shown inFigure 12 as shown in e.

[0122] 4. Bottom water plugging type

[0123] In the middle and late stages of production in the Shunbei No. 4 fault zone, the bottom water rises relatively fast, so some remaining gas of the bottom water plugging type has been formed; due to the bottom water coning in Well SHB4-12H, formation water enters the wellbore, blocking the channel for the production and migration of condensate gas, forming remaining gas of the bottom water plugging type (as Figure 12 shown in c); due to the relatively fast rise of the bottom water and the relatively high bottom hole position, the condensate gas in some conical reservoirs below the bottom hole position cannot be produced in time, forming a series of residual hill type remaining gas (as Figure 12 shown in d).

[0124] Distribution pattern of remaining gas in well groups:

[0125] 1. Isolated type

[0126] The condensate gas reservoir in the Shunbei No. 4 zone is distributed along the Shunbei No. 4 fault zone. The tectonic stress is tensile stress, and the model is relatively scattered. There are many reservoirs that surround the main fault plane but are not connected to the main fault plane. For example, in the models of Well Groups SHB44X and SHB45X, the condensate gas in the reservoirs of the main fault plane has been exploited, while the condensate gas in the reservoirs surrounding the main fault plane has not been exploited, forming isolated remaining gas. When the tectonic stress is compressive stress, the model is relatively compact and basically a whole. For example, there is a small amount of remaining condensate gas around the models of Well Groups SHB43X and SHB46X that is not connected to the main fault plane (as Figure 12 shown in f).

[0127] 2. Retained type near gas drive channel

[0128] For the development methods of some well groups with gas injection for pressure stabilization and gas injection for oil displacement, there is often an extremely permeable gas drive channel between the gas injection well and the production well. During the gas drive process, due to the blockage of the dense bedrock around the channel, some condensate gas in small pores has not been displaced and exploited, forming retained remaining gas. For example, in Well Group SHB46X, there is a seepage channel with relatively large permeability between two wells. Natural gas is injected into Well SHB4-8H to drive the condensate gas to move towards Well SHB46X. The permeability around the channel is relatively small, and this part of the condensate gas has not been exploited during the displacement process, forming retained remaining gas near the gas drive channel (as Figure 12 shown in g).

[0129] 3. Controlled by injection-production relationship

[0130] For a well group with good connectivity, when a flowing medium is injected into one well, under the displacement of external fluid, the condensate gas around the injection well is driven towards the production well, and then the condensate gas gradually accumulates around the production well. As shown in the SHB43X well group, natural gas (light component) is injected first to displace the condensate gas. The injected natural gas drives the upper condensate gas towards the adjacent well, forming an overriding inclined plane (as shown in Figure 12 i). If nitrogen (heavy component) is injected to displace the condensate gas, since the density of nitrogen is greater than that of the condensate gas, nitrogen sinks towards the bottom of the formation and drives the bottom condensate gas towards the adjacent well (as shown in Figure 12 h).

[0131] Fault-controlled carbonate fracture-vug reservoirs are developed in the Shunbei No. 4 fault zone. Affected by multiple large-scale strike-slip fault tectonic movements, the internal structure of the fault-controlled reservoirs is more complex and the heterogeneity is stronger. Based on the Petrel geological modeling software, the deterministic modeling method is applied to characterize the fault-controlled bodies, and the 3D geological modeling of the Shunbei No. 4 fault zone is completed. The fitting error between the condensate gas reserves in the geological model and the dynamic reserves is only 6.25%. Then, the production history fitting of a total of 14 units is completed, and the fitting error is less than 4%. This shows that the geological model can well characterize the real geological features and lays a foundation for the study of the distribution law of the remaining condensate gas in the carbonate condensate gas reservoir in the Shunbei No. 4 fault zone.

[0132] In the study of the distribution of the remaining gas in the fault-controlled carbonate condensate gas reservoir in the Shunbei No. 4 fault zone, the distribution law of the remaining gas in a single well is closely related to the tectonic movement suffered by the strike-slip fault: Tensile stress makes the model more dispersed, the connectivity between each reservoir body is poor, and the bedrock blocks the area between the two fault planes. When the well is opened for production, only the condensate gas in one fault plane is produced, and the other fault plane forms remaining gas; Compressive stress and translational stress make the model more concentrated, the connectivity between each reservoir body is good, and only more or less isolated remaining gas is formed around the model. Being affected by both tensile stress and translational stress will increase the degree of fragmentation of the fault plane, causing reservoir bodies of different sizes to be blocked by more dense bedrock, forming multiple remaining condensate gas reservoir bodies. The rise of bottom water and the blockage of the well bottom will also prevent the production of condensate gas, forming remaining condensate gas.

[0133] The distribution of remaining gas in a well group is mainly controlled by geological factors and development factors. Whether it is a single well or a well group, affected by tectonic stress, there will be some scattered remaining condensate gas around the fracture surface. When there is a channel with relatively high permeability between two wells in the model, during the injection of natural gas flooding, there will be some condensate gas sealed by dense bedrock above or below the gas flooding channel, forming trapped remaining gas near the unused gas flooding channel. When injecting natural gas for flooding, natural gas is a light component. After entering the formation, it diffuses and displaces the condensate gas in the upper part towards the production well bottom. The condensate gas accumulates around the production well and at the bottom of the formation. When injecting nitrogen, nitrogen diffuses and can displace the condensate gas at the bottom of the formation towards the production well bottom. The condensate gas accumulates around the production well and in the upper part of the formation.

[0134] Based on the study of the distribution characteristics of remaining gas in the fault-controlled carbonate condensate gas reservoir in the Shunbei No. 4 zone, according to the differences between single wells and well groups, the distribution patterns of remaining gas in the fault-controlled carbonate condensate gas reservoir are divided into two major categories: single-well remaining gas and well-group remaining gas. Specifically, according to the main controlling factors of the distribution characteristics of single-well and well-group remaining gas, it is further divided into 7 sub-categories. Among them, single-well remaining gas is divided into: single-well isolated type, tight plugging type, bottom water coning type, bottom water low-floating residual hill type, and tectonic stress control type; unit well-group remaining gas is divided into: well-group isolated type, trapped type near gas flooding channel, and injection-production relationship control type.

[0135] Implement Column 3

[0136] Such as Figure 13 As shown, an analysis device for the distribution pattern of remaining condensate gas in fault-controlled carbonate rocks includes at least one processor and a memory communicatively connected to the at least one processor; the memory stores instructions executable by the at least one processor, and when the instructions are executed by the at least one processor, the at least one processor is enabled to execute an analysis method for the distribution pattern of remaining gas in a carbonate condensate gas reservoir as described in the foregoing embodiments. The input / output interface may include a display, a keyboard, a mouse, and a USB interface for inputting and outputting data; the power supply is used to provide electrical energy for the electronic device.

[0137] Those skilled in the art can understand that all or part of the steps for implementing the foregoing method embodiments can be completed by hardware related to program instructions. The foregoing program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps including the foregoing method embodiments; and the foregoing storage medium includes: mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks and other various media that can store program codes.

[0138] When the above integrated units of the present invention are implemented in the form of software functional units and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on such an understanding, the technical solutions of the embodiments of the present invention essentially or the parts that contribute to the prior art can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the methods described in the embodiments of the present invention. The foregoing storage medium includes: various media such as removable storage devices, ROMs, magnetic disks, or optical discs that can store program codes.

[0139] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir, characterized in that It includes the following steps: S1: Divide different reservoir levels according to the reservoir development pattern and the development tectonic order; S2: Establish corresponding models according to different reservoir levels, and fuse the models of different levels to obtain a three-dimensional geological model; S3: After coarsening the three-dimensional geological model, establish mathematical models of each single well and well group by numerical simulation to complete the production history matching; S4: Obtain the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir according to the fitting results.

2. The analysis method for the remaining gas distribution pattern in a carbonate condensate gas reservoir according to claim 1, wherein Step S1 includes: Establish a reservoir development pattern by using seismic data, drilling data, cores, well logs and lost circulation and blowout records, as well as the tectonic position, reservoir type and spatial contact relationship.

3. The analysis method for the remaining gas distribution pattern in a carbonate condensate gas reservoir according to claim 2, characterized in that Step S1 also includes: Divide the fault-controlled reservoir into five levels: strike-slip fault zone, fault-controlled body, fracture body-cave-like body-disordered body, internal filling of cave-like body, and microfracture according to the reservoir development pattern and the development tectonic order, and determine the corresponding threshold truncation by using the deterministic modeling method according to different levels.

4. A method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir according to claim 3, characterized in that, The establishment of corresponding models according to different reservoir levels in step S2 includes: The strike-slip fault wave is mainly characterized by the fault-controlled body, and the fault-controlled body is composed of fracture body, cave-like body and disordered body. Therefore, the structure tensor, coherent energy gradient and variance seismic attribute body are respectively used to characterize it, and the corresponding threshold is determined by the well-seismic combination method to establish the contour models of the fracture body, cave-like body and disordered body; Taking the contour model of the cave-like body as a constraint, establish a three-dimensional model of the internal grid cluster structure layer by layer by using the object-based modeling method; For the microfractures, adopt an improved discrete fracture network simulation method to establish a microfracture network model that conforms to the actual morphology in the field outcrop.

5. The analysis method for the remaining gas distribution pattern in a carbonate condensate gas reservoir according to claim 1, characterized in that, Step S3 also includes: Establish mathematical models of each single well and well group by reservoir numerical simulation for production history matching.

6. The analysis method for the remaining gas distribution pattern in a carbonate condensate gas reservoir according to claim 1, wherein Step S4 includes: Generate a pressure change fitting diagram according to the pressure fitting before and after production, compare the pressure change fitting diagrams, and clarify the distribution law of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, and the distribution law includes distribution characteristics and distribution types.

7. A method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir according to claim 6, characterized in that, According to the distribution characteristics and distribution types of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, clarify the main controlling factors for the distribution of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, and obtain the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir.

8. A method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir according to claim 7, characterized in that, The distribution types of the remaining condensate gas in the single well include isolated type, tectonic control type, sealing plugging type, and bottom water plugging type.

9. A method for analyzing the remaining gas distribution pattern in a carbonate condensate gas reservoir according to claim 7, characterized in that, The distribution types of the remaining condensate gas in the well group include isolated type, retention type near the gas drive channel, and injection-production relationship control type.

10. An analysis device for the distribution pattern of remaining condensate gas in fractured and controlled carbonate rocks, characterized in that, The fault-controlled carbonate remaining condensate gas distribution pattern analysis device stores program instructions, and when the program instructions are executed by at least one processor, they are used to implement a method for analyzing the distribution pattern of remaining gas in a carbonate condensate gas reservoir according to any one of claims 1 to 9.

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