A method and device for analyzing the distribution pattern of remaining condensate gas in a faulted carbonate rock

Abstract

The present application relates to the technical field of oil and gas field development, and particularly relates to a method and device for analyzing distribution pattern of remaining condensate gas in faulted carbonate rock, comprising the following steps: S1: different reservoir levels are divided according to reservoir development pattern and development structure level; S2: corresponding models are established according to different reservoir levels, and the models of different levels are fused to obtain a three-dimensional geological model; S3: after the three-dimensional geological model is coarsened, a numerical simulation is used to establish mathematical models of each single well and well group, and production history matching is completed; S4: distribution pattern of remaining condensate gas in faulted carbonate rock condensate gas reservoir is obtained according to the matching result. By establishing a geological model and using a numerical simulation method, distribution law of remaining condensate gas in faulted carbonate rock condensate gas reservoir is studied, and main control factors are determined, which provides effective theoretical guidance for deep understanding of characteristics of the reservoir and potential tapping and improvement of condensate gas recovery.

Description

Technical Field

[0001] This invention relates to the technical field of oil and gas field development, and in particular to a method and apparatus for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks. Background Technology

[0002] Carbonate reservoirs hold a significant position in global oil and gas distribution, accounting for approximately 50% of the world's total reserves and over 60% of global oil and gas production. In China, fractured-vuggy carbonate reservoirs are mainly distributed in the Tarim Basin, with the Tahe Oilfield, Lungu Oilfield, Halahatang Oilfield, Fuman Oilfield, and Shunbei Oil and Gas Field having proven total geological reserves exceeding 20 × 10⁻⁶. 8 t is the most realistic successor field for oil and gas exploration and development.

[0003] The Shunbei region is dominated by fault-controlled bodies. Research focused on the Shunbei No. 4 belt, proposing a core-zone structure of strike-slip fault zones and a clustered development model of fault-controlled reservoirs. The reservoirs are internally divided into breccia zones and fracture zones, forming a unique "sieve-cluster" model in the Shunbei region. Fault-controlled bodies are the main reservoir components of the strike-slip fault system. Karstification within these bodies is generally weak, and reservoir spaces mainly consist of fracture cavities, inter-breccia pores, and tectonic fractures, all interconnected. These are relatively small in scale, resulting in strong heterogeneity. The strike-slip fault zones have undergone multiple tectonic movements, creating complex stress environments. The fracture patterns formed under different stress conditions vary significantly, leading to lateral segmentation of the fault-controlled reservoirs. The northern segment of the Shunbei No. 4 belt is dominated by extensional stress, the central segment by a combination of extensional stress and tectonic translation, and the southern segment by compressive stress. This unique sieve-cluster model and lateral segmentation structure make the exploitation of carbonate condensate gas reservoirs in this region more challenging.

[0004] Currently, condensate gas in the Shunbei No. 4 fault zone is mainly extracted through methods such as exhaustion, natural gas injection, and nitrogen injection. Of course, drilling and fracturing are also important means of extracting condensate gas reservoirs. However, due to the insufficient research on the distribution of residual condensate gas in fault-controlled carbonate condensate gas reservoirs, it is difficult to provide effective theoretical guidance for the development of condensate gas in fault-controlled carbonate rocks. This has led to low recovery rates, rapid bottom water advance in some production wells, the risk of water flooding, and rapid decline in formation pressure, which have consistently affected production. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies, such as insufficient research on the distribution of residual condensate gas in fault-controlled carbonate condensate gas reservoirs, which makes it difficult to provide effective theoretical guidance for the development of condensate gas in fault-controlled carbonate rocks. This invention provides a method and apparatus for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks.

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

[0007] A method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks includes the following steps:

[0008] S1: Different reservoir grades are classified according to reservoir development patterns and structural levels.

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

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

[0011] S4: Based on the fitting results, the distribution pattern of residual condensate gas in the fault-controlled carbonate condensate gas reservoir is obtained.

[0012] By adopting the above technical solution, a geological model is established, and numerical simulation is used to study the distribution law of residual condensate gas in fault-controlled carbonate condensate gas reservoirs, identify its main controlling factors, and provide effective theoretical guidance for a deeper understanding of the characteristics of this type of reservoir, the potential tapping of residual condensate gas, and the improvement of condensate gas recovery rate.

[0013] As a preferred option, step S1 includes: establishing a reservoir development model using seismic data, drilling data, core samples, logging and lost circulation records, as well as structural location, reservoir type and spatial contact relationship.

[0014] As a preferred option, step S1 further includes: dividing the fault-controlled reservoir into five levels according to the reservoir development model and development structural level: strike-slip fault zone, fault-controlled body, fault body-cavity-chaotic body, cavity-filling, and microfracture, and determining the corresponding threshold cutoff according to different levels using deterministic modeling methods.

[0015] As a preferred option, step S2, which involves establishing corresponding models based on different reservoir levels, includes: the strike-slip fault zone is mainly characterized by fault-controlled bodies, which are composed of fault bodies, cavern-like bodies, and chaotic bodies. Therefore, structural tensors, coherent energy gradients, and variance seismic attribute bodies are used to characterize them respectively. The corresponding thresholds are determined by combining well and seismic methods, and contour models of fault bodies, cavern-like bodies, and chaotic bodies are established.

[0016] The cave-like contour model is used as a constraint, and a target-based modeling method is used to build a three-dimensional model of the internal lattice structure layer by layer.

[0017] For the microcracks, an improved discrete crack network simulation method was adopted to establish a microcrack network model that conforms to the actual morphology in the field outcrops.

[0018] As a preferred option, step S3 also includes: establishing mathematical models of each individual well and well group through reservoir numerical simulation to fit the production history.

[0019] As a preferred embodiment, step S4 includes: generating a pressure change fitting map based on the pressure fitting before and after production, comparing the pressure change fitting maps, and clarifying the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, wherein the distribution pattern includes distribution characteristics and distribution type.

[0020] As a preferred option, based on the distribution characteristics and distribution type of the residual condensate gas in the fault-controlled carbonate condensate gas reservoir, the main controlling factors of the distribution of the residual condensate gas in the fault-controlled carbonate condensate gas reservoir are identified, and the distribution pattern of the residual condensate gas in the fault-controlled carbonate condensate gas reservoir is obtained.

[0021] As a preferred embodiment, the distribution types of the residual condensate gas in the single well include isolated type, structure-controlled type, tight-sealed type, and bottom water-sealed type.

[0022] As a preferred embodiment, the distribution types of the remaining condensate gas in the well group include isolated type, stagnant type near the gas drive channel, and injection-production relationship controlled type.

[0023] On the other hand, a device for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks is provided. The device stores program instructions, which, when executed by at least one processor, are used to implement the method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks as described above.

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

[0025] By establishing a three-dimensional geological model and coarsening it appropriately, mathematical models of individual wells and well groups are built using reservoir numerical simulation methods. Production history is fitted, and the distribution pattern of residual condensate gas in fault-controlled carbonate condensate gas reservoirs is clarified through the fitting results. The main controlling factors of its distribution are identified, and then the distribution pattern of residual gas in fault-controlled carbonate condensate gas reservoirs is divided according to the main controlling factors. This provides technical support for the subsequent exploitation of such condensate gas and provides effective theoretical guidance for a deeper understanding of the characteristics of this type of reservoir, the potential tapping of residual condensate gas, and the improvement of condensate gas recovery rate. Attached Figure Description

[0026] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0027] Figure 1 This is a flowchart of a method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks as described in Example 1;

[0028] Figure 2 The structural location map of the Shunbei 4 belt in the Tarim Basin is shown in Example 2, which describes a method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks.

[0029] Figure 3 This is a stratigraphic development characteristic map of the Shunbei oil and gas field, based on the analysis method for the distribution pattern of residual condensate gas in fault-controlled carbonate rocks described in Example 2.

[0030] Figure 4 This is a schematic diagram of the fault-controlled body sieve cluster structure in the Shunbei oil and gas field, illustrating the method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks as described in Example 2.

[0031] Figure 5 This is a horizontal segmentation diagram of the Shunbei No. 4 belt, which is a method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks as described in Example 2.

[0032] Figure 6 The energy coherence diagram and well location diagram of the Shunbei 43X well group are provided for the analysis method of residual condensate gas distribution pattern in fault-controlled carbonate rocks as described in Example 2.

[0033] Figure 7 This is a well location map of the Shunbei No. 4 fault zone, which is described in Example 2 as an analysis method for the distribution pattern of residual condensate gas in fault-controlled carbonate rocks.

[0034] Figure 8 This is a three-dimensional geological model of the southern segment of the Shunbei No. 4 belt, as described in Example 2, of a method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks.

[0035] Figure 9 The mathematical model diagram of the SHB43X well group is shown in Example 2, which describes a method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks.

[0036] Figure 10 This is a residual gas distribution characteristic map of a single well in the Shunbei No. 4 belt, based on the residual condensate gas distribution pattern analysis method for fault-controlled carbonate rocks described in Example 2.

[0037] Figure 11This is a residual gas distribution characteristic map of the Shunbei No. 4 well group in the fault-controlled carbonate rock residual condensate gas distribution pattern analysis method described in Example 2.

[0038] Figure 12 This is a diagram showing the residual gas distribution pattern of a fault-controlled carbonate condensate gas reservoir, as described in Example 2, using a method for analyzing the residual condensate gas distribution pattern of a fault-controlled carbonate rock.

[0039] Figure 13 This is a structural diagram of a device for analyzing the distribution pattern of residual condensate gas in fracture-controlled carbonate rocks, as described in Embodiment 3 of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally 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 to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0041] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance, or suggesting any such actual relationship or order between these entities or operations. Additionally, the terms "connected," "linked," etc., can refer to a direct connection between components or an indirect connection via other components.

[0042] Example 1

[0043] This embodiment discloses a method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks, such as... Figure 1 As shown, it includes the following steps:

[0044] S1: Different reservoir grades are classified according to reservoir development patterns and structural levels.

[0045] Specifically, step S1 includes: establishing reservoir development models using seismic data, drilling data, core samples, logging and loss-of-life records, as well as structural locations, reservoir types and spatial contact relationships.

[0046] Step S1 also includes: dividing the fault-controlled reservoir into five levels according to the reservoir development model and development structural level: strike-slip fault zone, fault-controlled body, fault body-cavity-chaotic body, cavity-filling, and microfracture, and determining the corresponding threshold cutoff according to different levels using deterministic modeling methods.

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

[0048] Step S2, which establishes corresponding models according to different reservoir levels, includes: the strike-slip fault zone is mainly characterized by fault-controlled bodies, which are composed of fault bodies, cavern-like bodies, and chaotic bodies. Therefore, structural tensor, coherent energy gradient, and variance seismic attribute volume are used to characterize them respectively. The corresponding thresholds are determined by combining well and seismic methods, and contour models of fault bodies, cavern-like bodies, and chaotic bodies are established.

[0049] The cave-like contour model is used as a constraint, and a target-based modeling method is used to build a three-dimensional model of the internal lattice structure layer by layer.

[0050] For the microcracks, an improved discrete crack network simulation method was adopted to establish a microcrack network model that conforms to the actual morphology in the field outcrops.

[0051] S3: After coarsening the three-dimensional geological model, numerical simulation is used to establish mathematical models for each individual well and well group, and production history fitting is completed;

[0052] Step S3 also includes: establishing mathematical models for each individual well and well group through reservoir numerical simulation to fit the production history.

[0053] S4: Based on the fitting results, the distribution pattern of residual condensate gas in the fault-controlled carbonate condensate gas reservoir is obtained.

[0054] Step S4 includes: generating a pressure change fitting map based on the pressure fitting before and after production, comparing the pressure change fitting maps, and clarifying the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir. The distribution pattern includes distribution characteristics and distribution type.

[0055] Specifically, based on the distribution characteristics and distribution types of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir, the main controlling factors of the distribution of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir are identified, and the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir is obtained.

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

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

[0058] Example 2

[0059] This embodiment is a specific implementation of Embodiment 1;

[0060] Taking Shunbei No. 4 as an example: Carbonate oil and gas reservoirs occupy an important position in the world's oil and gas distribution, with their oil and gas reserves accounting for about 50% of the world's total oil and gas reserves and their oil and gas production accounting for more than 60% of the world's total oil and gas production. China's fractured-vuggy carbonate oil reservoirs (fractured-vuggy reservoirs) are mainly distributed in the Tarim Basin. Among them, the Tahe Oilfield, Lungu Oilfield, Halahatang Oilfield, Fuman Oilfield, and Shunbei Oil and Gas Field have proven total geological reserves of more than 20×108t, making them the most realistic replacement area for oil and gas exploration and development.

[0061] The Shunbei region is dominated by fault-controlled bodies. Research focused on the Shunbei No. 4 belt, proposing a core-zone structure of strike-slip fault zones and a clustered development model of fault-controlled reservoirs. The reservoirs are internally divided into breccia zones and fracture zones, forming a unique "sieve-cluster" model in the Shunbei region. Fault-controlled bodies are the main reservoir components of the strike-slip fault system. Karstification within these bodies is generally weak, and reservoir spaces mainly consist of fracture cavities, inter-breccia pores, and tectonic fractures, all interconnected. These are relatively small in scale, resulting in strong heterogeneity. The strike-slip fault zones have undergone multiple tectonic movements, creating complex stress environments. The fracture patterns formed under different stress conditions vary significantly, leading to lateral segmentation of the fault-controlled reservoirs. The northern segment of the Shunbei No. 4 belt is dominated by extensional stress, the central segment by a combination of extensional stress and tectonic translation, and the southern segment by compressive stress. This unique sieve-cluster model and lateral segmentation structure make the exploitation of carbonate condensate gas reservoirs in this region more challenging.

[0062] The Shunbei No. 4 belt belongs to a fault-controlled carbonate condensate gas reservoir, a complex and special type of gas reservoir that falls between oil and gas reservoirs. During development, hydrocarbon gases exist underground in gaseous form. When extracted to the surface, due to changes in temperature and pressure, liquid petroleum condenses out, resulting in condensate oil. Based on the equation of state and recoverable reserves of actual condensate gas, a functional relationship between the recovery rate of recoverable reserves and formation pressure was established. The distribution of recoverable reserves during extraction replaced the distribution of formation pressure, achieving a quantitative description of the remaining gas distribution. The distribution patterns of remaining oil in fractured-vuggy reservoirs were classified, and potential tapping suggestions were given for different distribution patterns. Through condensate gas pressure decay experiments, combined with micron-sized computed tomography (CT) technology, and based on the CT images, a series of calculations and analyses were performed to obtain a quantitative characterization of the condensate oil reserves and locations at different stages in the condensate gas reservoir. By combining core displacement experiments and nuclear magnetic resonance (NMR) technology, the microscopic distribution law of residual gas in carbonate gas reservoirs was studied, which further improved the understanding of residual gas distribution and provided a basis for improving the recovery rate of this type of gas reservoir.

[0063] Currently, many foreign scholars have proposed numerous new methods and applications in the study of carbonate condensate gas reservoirs. Through the analysis of the physical properties of hydrocarbon gases in Albanian condensate gas fields, the type and properties of reservoir fluids, including physical and chemical properties, are determined, playing a crucial role in many decisions made in oil and gas field development and in reservoir engineering. Based on mathematical modeling, the hydrocarbon phase separation process during the depletion production of exhausted condensate gas reservoirs and the production of anti-condensate gas reservoirs was studied. An effective method for producing anti-condensate oil was found to be water injection. The saturation-pressure relationship and multiphase pseudo-pressure calculation for anti-condensate gas reservoir production under the dominant boundary flow were improved, providing technical support for the production of condensate gas reservoirs experiencing anti-condensation. The fluid in the condensate gas reservoir was simulated using software. Four samples—nitrogen, carbon dioxide, methane, and separator gas—were injected into the reservoir, and the effects of changing the injection rate, injection pressure, and injection duration on the recovery rate of the condensate gas reservoir were investigated, providing a theoretical basis for subsequent condensate gas production. A comprehensive model was established for the production study of condensate gas reservoirs, reproducing the rate of decline in reservoir pressure and productivity, and calculating hydrocarbon production levels while considering existing risks, thus providing support for the exploitation of condensate gas reservoirs. Hydrodynamic simulation was used to select development methods for condensate gas reservoirs, providing a new approach for choosing development methods. Artificial intelligence technology was used to predict the performance of constant-volume depletion tests in condensate gas reservoirs, improving the accuracy of pressure-volume-temperature (PVT) data during the development process. By introducing a modified compressibility parameter into the traditional FMB equation, accurate estimation of initial in-situ gas and mean reservoir pressure in non-volume fractured condensate gas reservoirs was achieved, providing a new method for subsequent research on dual-porosity models. Group data processing methods were applied to predict permeability in heterogeneous carbonate condensate gas reservoirs, providing important support for condensate gas reservoir research. Through pore-scale analysis of condensate gas reservoir injection, it was identified that C2 and CO2 are the most effective gases for removing accumulated condensate gas and re-establishing gas flow, providing a theoretical basis for the subsequent re-establishment of gas flow in condensate gas reservoirs.

[0064] The Shunbei No. 4 fault zone is controlled by a large strike-slip fault and contains multiple smaller strike-slip faults. Influenced by multiple phases of tectonic movement, it has formed a typical fault-controlled reservoir. Compared to conventional reservoirs, fault-controlled reservoirs exhibit fracture zones vertically, creating high-permeability channels. However, dense bedrock obstructs the vertical direction of the fault planes, resulting in poor connectivity – a phenomenon known as the "sieve cluster structure." Previous research on the distribution of residual gas in condensate gas reservoirs has progressed from theoretical to quantitative studies, from depletion development to water injection for pressure stabilization, and finally to methods such as gas injection, natural gas injection, and nitrogen injection. However, a systematic classification of the distribution patterns of residual condensate gas in carbonate condensate gas reservoirs is still lacking, leaving a gap in this field. This is particularly true for the currently popular study of residual gas distribution patterns in fault-controlled fracture-vuggy carbonate condensate gas reservoirs, which still lacks a systematic understanding. Therefore, studying the distribution patterns of residual gas in fault-controlled carbonate condensate gas reservoirs, identifying its main controlling factors, and classifying the distribution patterns of residual gas in fault-controlled carbonate condensate gas reservoirs is of paramount importance.

[0065] Currently, condensate gas in the Shunbei No. 4 fault zone is mainly extracted through methods such as exhaustion, natural gas injection, and nitrogen injection. Drilling and fracturing are also important means of condensate gas extraction. However, current recovery rates are low, with some production wells experiencing rapid bottom water advance, posing a risk of water flooding. Rapid formation pressure decline continues to hinder production. Furthermore, research on the distribution of residual condensate gas in fault-controlled carbonate condensate gas reservoirs is insufficient, making it difficult to provide effective theoretical guidance for their development. Therefore, this paper takes the fault-controlled carbonate condensate gas reservoir in the Shunbei Oilfield No. 4 fault zone as an example. By establishing a geological model and utilizing reservoir numerical simulation, this paper studies the distribution law of residual gas in fault-controlled carbonate condensate gas reservoirs, identifies its main controlling factors, and aims to provide guidance for a deeper understanding of the characteristics of this type of reservoir, the potential tapping of residual condensate gas, and the improvement of condensate gas recovery rates.

[0066] Geological Overview:

[0067] 1. Geological characteristics of the Shunbei oil and gas field region

[0068] The Shunbei Oilfield in the Tarim Basin is mainly located in the Shuntogol Low Uplift, which extends southeast to the southward slope of the Guchengxu Uplift. It connects to the Shaya Uplift to the north, contacts the Katakelong Uplift to the south, borders the Manjiaer Depression to the east, and contacts the Awati Depression to the west. The Shuntogol Low Uplift has undergone multiple phases of complex sedimentary and tectonic evolution, providing favorable geological conditions for the development of multiple fracture-vuggy reservoirs and the enrichment of hydrocarbons. Located in the center of the Tarim Basin, the Shuntogol Low Uplift is less affected by orogenic activities at the basin margins and is a relatively stable first-order tectonic unit in the Tarim Basin (e.g., ...). Figure 2 (As shown).

[0069] 2. Lithological characteristics of the study area

[0070] The Ordovician strata in the Shunbei area are well-developed, consisting of the Lower Ordovician Penglaiba Formation, Yingshan Formation, Yijianfang Formation, Qiaerbake Formation, and Querqueke Group (e.g., ...) from bottom to top. Figure 3 (As shown).

[0071] The Penglaiba Formation is mainly composed of platform-facies dolomite and calcareous dolomite. The Yingshan Formation belongs to the Middle-Lower Ordovician strata and is fully developed in the Shuntuoguole low-uplift area. The main lithologies in this stratum are yellow-gray micritic limestone, sandy micritic limestone, and dark gray micritic limestone. The Yijianfang Formation belongs to the Middle Ordovician strata and is in conformable contact with the overlying Yingshan Formation. It gradually thins or pinches out from the east to the south in the study area, with a thickness of about 160m. The lithology is yellow-gray. The Qiaerbake Formation consists of micritic limestone, sandy micritic limestone, and sandy micritic limestone. It belongs to the Upper Ordovician System and is in unconformable contact with the lower Yijianfang Formation. This formation can be roughly divided into two parts: the upper part is brownish-brown or reddish-brown calcareous mudstone, and the lower part is yellowish-gray micritic limestone. The Lianglitag Formation is mainly composed of gray and light gray micritic limestone or sandy micritic limestone. The Santamu Formation is mainly composed of gray and dark gray mudstone and calcareous mudstone.

[0072] The Shunbei No. 4 strike-slip fault zone has high condensate gas reserves. The condensate gas reservoirs in the entire Shunbei No. 4 zone are distributed along the Shunbei No. 4 strike-slip fault zone. The Lower Cambrian Yuertus Formation is the main source rock. The fault extends vertically along the condensate gas reservoirs in the Shunbei No. 4 zone, so the fault connectivity is strong. At the same time, the strata are fractured to form caves, cross-sectional cavities and fractures formed by the faults, which are good reservoirs for oil and gas. Clarifying the distribution of condensate gas reservoirs in the reservoir space of the entire Shunbei No. 4 zone is crucial for the exploitation of the Shunbei No. 4 zone.

[0073] 3. Fault-controlled reservoir characteristics

[0074] The carbonate strata of the Jianfang Formation and the Yingshan Formation of the Middle-Lower Ordovician are the main target strata of the Shunbei Oil and Gas Field. The Shuntogole Low Uplift has long been located in a low-lying structural position, with underdeveloped karst tops in the Jianfang and Lianglitag Formations, and no karst fracture-vuggy reservoirs similar to those formed by karst processes in the Tarim Oilfield. However, during multiple tectonic movements, various small-scale strike-slip fault zones have developed in the Shunbei Oil and Gas Field. The fracturing of the carbonate rocks in the Jianfang-Yingshan Formation has formed unique fault-controlled fracture-vuggy reservoirs, mainly due to the multi-stage activity of strike-slip faults. The effective reservoir space is primarily composed of fault cavities and fractures. Studies indicate that the study area is a fault-controlled fracture-vuggy reservoir controlled by a large strike-slip fault zone. Based on the hierarchical classification of the fault-controlled fracture-vuggy reservoirs, they are sequentially divided into five levels: strike-slip fault zone, fault-controlled body, fault body-vuggy-chaotic body, vuggy-vuggy interior filling, and microfractures. Higher levels have a constraining effect on lower levels, as shown in Table 1.

[0075] Table 1: Hierarchical Feature Table

[0076]

[0077] The fault-controlled reservoirs in the Shunbei oil and gas field are developed in ultra-deep strata at depths greater than 7200m, and are a special type of reservoir formed due to the development of strike-slip faults. The fault-controlled reservoirs are distributed in strips along the strike-slip fault zones, and perpendicular to the fault zone, they develop multiple sets of fracture-cavity aggregates—sieve-cluster structures—arranged in an orderly manner from bedrock to fracture zone to cave zone to fracture zone to bedrock zone. Figure 4 As shown.

[0078] The Shunbei 4 condensate gas reservoir is mainly distributed along the Shunbei 4 strike-slip fault. This fault zone has undergone multiple tectonic movements, resulting in a complex stress environment and significant differences in fault patterns formed under different stress conditions. This has led to the lateral segmentation of the fault-controlled reservoir. The northern segment of the Shunbei 4 belt is dominated by extensional stress, the middle segment by a combination of extensional stress and tectonic strike-slip, and the southern segment by compressive stress. Figure 5 As shown.

[0079] The tectonic stress of the SHB43X well group in the northern section of Shunbei No. 4 belt is weak compressive stress. This is based on the coherent energy gradient diagrams of wells SHB43X, SHB4-9H, and SHB4-6H, and the well location map of this well group. Figure 6 As shown, the condensate gas reservoir in this well group is distributed along the strike-slip fault zone of the Shunbei No. 4 fault zone. Combined with the well location distribution of all production wells and injection wells in the Shunbei No. 4 fault zone condensate gas reservoir, it can be seen that the entire Shunbei No. 4 fault zone condensate gas reservoir is strip-shaped and distributed along the Shunbei No. 4 strike-slip fault zone.

[0080] 4. Development Features

[0081] The Shunbei No. 4 formation is 60 km long and 1.5 km wide. It produces 2,237 tons of oil and 4.48 million cubic meters of gas per day, with a comprehensive water cut of 6.5%. The dynamic reserves of condensate gas are 16 billion cubic meters, and the dynamic reserves of condensate oil are 7.91 million tons. The cumulative oil production is 253,000 tons, and the cumulative gas production is 469 million cubic meters. The condensate oil recovery rate is 3.1%, and the condensate gas recovery rate is 2.9%. The original formation pressure in the Shunbei No. 4 formation was 88.4 MPa, and the current average formation pressure is 61.8 MPa, maintaining a pressure retention rate of 70%.

[0082] The unit is divided into 4 multi-well units (9 wells) and 10 single-well units. The multi-well units include the SHB43X well group (SHB43X and SHB4-6H are production wells, and SHB4-9H is a gas injection well), the SHB44X well group (SHB44X and SHB4-14H are both 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 a gas injection well). The single-well units include ten single wells: SHB4-5H, SHB4-4H, SHB4-7H, SHB41X, SHB4-1H, SHB4-2H, SHB4-3H, SHB47X, SHB4-12H, and SHB4-13H. Figure 7 As shown.

[0083] 5. Establishment of a three-dimensional geological model

[0084] By fully utilizing seismic data, drilling data, core samples, well logs, and lost-vent records, a reservoir development model was established based on structural location, reservoir type, and spatial contact relationships. According to the reservoir development model, different reservoir levels were defined based on the structural development hierarchy. Based on the hierarchy classification method, the fault-controlled reservoir was divided into five levels: strike-slip fault zone, fault-controlled body, fault-cavity-chaotic body, cavity-filled interior, and microfractures. For different levels, a deterministic modeling method was used to determine their threshold cutoff. Strike-slip fault zones are extensive and their boundaries are difficult to determine; therefore, the focus was on representing the fault-controlled body, which consists of fault bodies, cavity-filled interiors, and chaotic bodies. Therefore, structural tensors, coherent energy gradients, and variance seismic attributes were used to represent them, respectively. A well-seismic combined approach was used to determine appropriate thresholds, and contour models of fault bodies, cavity-filled interiors, and chaotic bodies were established. Using the cavity-filled interior contour model as a constraint, an improved objective-based modeling method was adopted to build a layer-by-layer 3D model of the internal cluster structure. For microfractures, an improved discrete fracture network simulation method was adopted to establish a microfracture network model that conforms to the actual morphology in field outcrops, including conjugate fractures and tortuous fractures. Models of different levels were fused according to priority to obtain a three-dimensional geological model of the Shunbei No. 4 fault zone, such as... Figure 8 As shown, a three-dimensional geological model data volume is provided for numerical simulation studies. Based on the established physical property model, the reserves of the study area are calculated. The condensate gas reserves in the Shunbei No. 4 fault zone of the study area are approximately 170 × 10⁸ m³, and the dynamic reserves of the study area are approximately 160 × 10⁸ m³. The difference between the condensate gas reserves in the physical property model and the dynamic reserves is 10 × 10⁸ m³, with a fitting error rate of 6.25%. Therefore, the established geological model realistically represents the actual geological reserves and can provide good guidance for subsequent numerical simulation work.

[0085] 6. Numerical simulation

[0086] Currently, the problems in production along the No. 4 fault zone of Shunbei Oilfield include: low recovery rates in production wells, rapid rise in bottom water at the bottom of some production wells posing a risk of water flooding, and a rapid decline in formation pressure. To address these issues, this paper aims to clarify the distribution of residual condensate gas in carbonate condensate gas reservoirs, study its distribution patterns, and summarize the distribution models of residual condensate gas in such reservoirs. This will provide guidance for the subsequent exploitation of residual gas in fault-controlled carbonate condensate gas reservoirs. Based on a three-dimensional geological model, and after reasonable coarsening, numerical simulation methods are used to establish mathematical models for individual wells and well groups, such as... Figure 9 As shown, the production history was fitted, and the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir was clarified through the fitting results. The main controlling factors of its distribution were identified, and then the distribution pattern of the remaining gas in the fault-controlled carbonate condensate gas reservoir was divided according to the main controlling factors, so as to provide technical support for the subsequent exploitation of such condensate gas.

[0087] The Shunbei No. 4 fault zone is divided into three regions: the northern section, the central section, and the southern section, comprising 14 unit blocks. Well groups / single wells are used for this division, with a coarse grid size of 4×50×50. As of October 2023, the cumulative fitting degree was greater than 96%, and the average fitting degree was 98.69%, providing strong support for understanding the distribution characteristics of residual condensate gas and making subsequent research more realistic and reliable, as shown in Table 2.

[0088]

[0089] Table 2 Fitting results of each unit of the Shunbei No. 4 fault zone

[0090] The production wells have low recovery rates and low production efficiency. Some production wells have rapid bottom water advance, posing a risk of water flooding. Formation pressure drops rapidly. To address these issues and clarify the distribution location and pattern of residual gas in the condensate gas reservoir, this paper uses reservoir numerical simulation to fit the production history of all wells (well groups) in the Shunbei No. 4 condensate gas reservoir and clarifies the distribution characteristics of residual gas in the Shunbei No. 4 condensate gas reservoir.

[0091] Characteristics of residual gas distribution in a single well:

[0092] Well SHB4-4H is located in the northern segment of the Shunbei No. 4 fault zone. The well-controlled area belongs to the pull-out section. Under tectonic stress, the model moves backward, and the space between the two fault surfaces is filled with dense bedrock. According to the production pressure change fitting diagram (such as...), Figure 10As shown in a), SHB4-4H is a horizontal well. The well trajectory passes through one side of the fault face and comes into contact with the other side of the fault face. Although the well passes through one side of the fault face, the condensate gas reservoir in the fault face reservoir on one side of the well is not activated due to the filling of tight bedrock. Only the condensate gas in the reservoir on the other side of the fault face is activated. The unactivated condensate gas forms residual condensate gas controlled by tectonic stress.

[0093] Well SHB4-5H is located in the northern section of the Shunbei No. 4 belt, and its well-controlled area belongs to the translational section; according to the production pressure change fitting diagram (such as... Figure 10 As shown in b), most of the well model is connected to the main cross section. Under the action of tectonic stress, there is scattered condensate gas around the model that has not been utilized.

[0094] Well SHB4-7H is located in the middle section of the Shunbei No. 4 belt. The well-controlled area belongs to the squeezing zone. According to the production pressure change fitting diagram (e.g.) Figure 10 As shown in c), most of the well model is connected to the main cross section. Under the action of tectonic stress, there is a scattered accumulation of unused condensate gas around the model.

[0095] Well SHB4-2H is located in the middle section of the Shunbei No. 4 belt. The well control area of ​​this well belongs to the pull-out section. According to the production pressure change fitting diagram (e.g.) Figure 10 As shown in d), most of the well model is connected to the main cross section. Under the action of tectonic stress, there is scattered unused condensate gas around the model.

[0096] Well SHB41X is located in the middle section of the Shunbei No. 4 belt, and its well-controlled area belongs to the pull-out section. Based on the production pressure change fitting diagram (e.g....), Figure 10 As shown in e), the well trajectory passes through two sections. Due to the dense bedrock filling, the well trajectory is not connected to the right fracture surface shown in the image. The pressure on the right section did not change much in the later stages of fitting, and the condensate gas was not utilized, forming residual gas controlled by tectonic stress. At the same time, due to tensile stress, part of the reservoir was broken, and there was scattered unutilized condensate gas around the two fracture surfaces.

[0097] Well SHB4-1H is located in the southern section of the Shunbei No. 4 belt, and its well-controlled area belongs to the pull-out section. Based on the production pressure change fitting diagram (e.g., ...), ... Figure 10 (as shown in f), the model of this well is mostly connected to the main cross section, and there are scattered unused condensate gas around the fracture surface.

[0098] Well SHB4-3H is located in the southern section of the Shunbei No. 4 belt. The well-controlled area belongs to the pull-out section. According to the production pressure change fitting diagram (such as...), Figure 10 As shown in g), most of the well model is connected to the main cross section, with a small amount of scattered unused condensate gas at the top of the model.

[0099] Well SHB47X is located in the southern section of the Shunbei No. 4 belt. The well-controlled area belongs to the pressure uplift zone. According to the production pressure change fitting diagram (such as...), Figure 10 As shown in h), the well trajectory comes into contact with the left and right fracture surfaces as shown in the image. However, due to the dense bedrock filling between the right fracture surface and the well trajectory, the well trajectory is not connected to the right fracture surface. Condensate gas accumulates on the right fracture surface, forming residual condensate gas controlled by tectonic stress.

[0100] Well SHB4-12H is located in the southern segment of Shunbei No. 4 Belt, and the well-controlled area belongs to the compression zone. Production history was fitted using reservoir numerical simulation software, and the pressure change fitting diagram before and after production was used (e.g., [image missing]). Figure 10 (As shown in j), this well is a horizontal well. The well trajectory crosses the left fault face. There is bedrock filling between the left and right fault faces. Therefore, this well can currently only utilize the condensate gas in the reservoir of the left fault face, while the reservoir of the right fault face is rich in condensate gas. According to the gas saturation diagram of this well (as shown in j), Figure 10 As shown in i), the water at the bottom of the well rises rapidly, forming a water cone at the bottom of the well, blocking the bottom of the production well, and preventing the remaining condensate gas in the formation from being extracted.

[0101] Well SHB4-13H is located in the southern segment of the Shunbei No. 4 belt. The well-controlled area belongs to the translational-pull-apart section. The formation is affected by pull-apart and translational stresses, resulting in a high degree of formation fragmentation and the formation of reservoirs of varying sizes. Moreover, these reservoirs are filled with tight bedrock and are not interconnected. According to the production pressure change fitting diagram (e.g.) Figure 10 As shown in k), within the well control area of ​​this well, due to the filling of tight bedrock, not all reservoirs in the entire model are connected together. This well can only utilize a portion of the condensate gas, while most of the condensate gas remains unused, forming a residual condensate gas controlled by tight sealing.

[0102] Residual gas distribution characteristics of well groups:

[0103] The SHB43X well group is located in the northern segment of the Shunbei No. 4 fault zone. The group includes wells SHB43X, SHB4-6H, and SHB4-9H, with SHB4-9H being an injection well and the other two being production wells. The tectonic stress in the SHB43X well group region is weak compressive stress, and the entire cross-sectional model is essentially a single unit. Production history fitting using reservoir numerical simulation software, based on the pressure change fitting comparison before and after production, shows that all three wells in this group traverse the cross-sectional model. There is a region of higher pressure above well SHB4-6H, where the reservoir is not connected to the main fault face. This portion of condensate gas is unutilized and exists sporadically in the formation. Initially, well SHB4-9H injected natural gas to displace the condensate gas. After entering the formation, the natural gas diffuses. Due to the lower density of natural gas than condensate gas, it migrates upwards, gradually displacing the upper condensate gas and moving towards the production well. This causes the condensate gas to accumulate around the production well (e.g., ...). Figure 11 (As shown in a); if nitrogen is injected to displace condensate gas, nitrogen, being denser than condensate gas, will deposit towards the bottom of the formation after entering the formation. It will then displace the condensate gas at the bottom of the reservoir and migrate towards the production well, resulting in condensate gas enrichment around the production well (e.g., as shown in a). Figure 11 (as shown in b).

[0104] The SHB44X well group is located in the northern segment of the Shunbei No. 4 fault zone. The group includes two wells, SHB44X and SHB4-14H, both of which are production wells. The well group area belongs to a pull-apart section. During actual production, the two wells showed significant production pressure responses and good connectivity. Based on the comparison chart of production pressure fitting between the initial and current production stages (e.g., ...),... Figure 11 As shown in c), the pressure of the main reservoir gradually decreases as production progresses. However, in some areas outside the main section, the pressure of some reservoirs does not change much. It is inferred that these reservoirs have poor connectivity with the main section and exist alone in the formation. Although they are within the well control range, they cannot be activated and are scattered in the formation.

[0105] The SHB45X well group is located in the northern section of the Shunbei No. 4 belt. The well group includes two wells, SHB45X and SHB4-11H, and the area belongs to a pull-out section. Based on the comparison chart of initial and current production pressure (e.g.), Figure 11 As shown in d), there are some scattered reservoirs with high pressure around the main fracture surface in the well group area. Although they are within the well control range, they cannot be actively used.

[0106] The SHB46X well group is located in the middle section of the Shunbei No. 4 belt. The group includes two wells, SHB46X and SHB4-8H, and the area is a transverse section. The entire cross-sectional model is essentially a single unit with very little scattered condensate gas. SHB46X is the production well, and SHB4-8H is the injection well. Based on the production history, a gas saturation streamline diagram is fitted (e.g., ...). Figure 11 (as shown in e) and numerical simulation permeability models (such as...) Figure 11 As shown in f), this well group has a gas drive channel with excellent permeability, but the permeability in the upper part of the channel is very low and it is blocked by a seal. The condensate gas inside is not utilized, forming stagnant condensate gas near the gas drive channel.

[0107] Distribution pattern of residual gas in fault-controlled carbonate condensate gas reservoirs:

[0108] To clarify the distribution patterns of residual gas in fault-controlled carbonate condensate gas reservoirs and to ensure the systematic and accurate nature of its distribution, this paper employs reservoir numerical simulation, combined with well logging and seismic data, to analyze the residual gas distribution on mathematical models. The distribution characteristics of residual gas in individual wells and well groups within the Shunbei No. 4 belt are summarized and analyzed. The distribution patterns of residual gas in fault-controlled carbonate condensate gas reservoirs are divided into two main categories: residual gas in individual wells and residual gas in well groups; these are further subdivided into seven subcategories, as shown in Table 3.

[0109]

[0110] Table 3. Distribution Categories of Residual Gas in Fault-Controlled Carbonate Condensate Gas Reservoirs

[0111] Single-well residual gas distribution pattern:

[0112] 1. Isolated type

[0113] Based on actual geological data and dynamic and static data, the closer to the main fault zone, the more developed the fault-controlled Ordovician carbonate reservoir, and the better the connectivity between the fault-controlled reservoir and the deep fault, resulting in more abundant hydrocarbon injection. Conversely, the farther away from the main fault zone, the weaker the development of the fault-controlled carbonate reservoir, with reservoir spaces mainly consisting of isolated caverns, poorer connectivity between the reservoir and the source fault, and weaker hydrocarbon injection. This residual gas is isolated and enriched in reservoir spaces far from the main fault surface, such as SHB4-2H and SHB4-7H. It can be clearly seen that some modules around the main fault model have higher pressure and are not connected to the main fault, resulting in residual gas enrichment. The reason for this is the sealing of tight bedrock; some reservoirs are not connected to the main fault. This residual condensate gas is called isolated residual gas (e.g., Figure 12 (as shown in a).

[0114] 2. Structural stress-controlled type

[0115] The strike-slip fault zone, influenced by stress differences, exhibits segmentation, which can be further subdivided into compressional, tensional, and translational segments. The Shunbei No. 4 fault zone is a large strike-slip fault zone that has undergone multiple tectonic movements, resulting in a complex stress environment and significant differences in fracture patterns under different stress conditions. This leads to the lateral segmentation of the fault-controlled reservoir. When the tectonic stress on the strike-slip fault is tensile stress, the two fault surfaces move away from each other, gradually moving apart to form a "V" shape. Simultaneously, the area between the two fault surfaces is filled with bedrock, hindering oil and gas migration. The resulting reservoirs are mainly distributed along the two fault surfaces, and these reservoirs are mostly unconnected. Condensate gas has difficulty moving from one side of the fault surface to the other, resulting in condensate gas being extracted from the reservoir on one side of the fault surface while remaining unused in the reservoir on the other side (e.g., ...). Figure 12 (As shown in b), for example, SHB41X, SHB47X, etc., the reservoirs are distributed on both sides of the fault surface, and the middle is filled and sealed by bedrock. When the well is opened for production, only a part of the condensate gas can be used.

[0116] Conversely, if the structural stress is compressive stress or stress caused by translation along the Shunbei No. 4 fault zone, the model is relatively compact, and the reservoirs are interconnected, often forming a large reservoir. During the well production process, most of the condensate gas can be utilized, such as in wells SHB4-3H and SHB4-7H. The reservoir is basically a whole, with only a small amount of isolated residual gas around it that cannot be utilized.

[0117] 3. Sealing and plugging type

[0118] Due to the vertical stratification of fault-controlled carbonate reservoirs, residual gas remains unexploited within the tight sections of the fault-controlled bodies. Fault-controlled condensate gas reservoirs in carbonate rocks are formed through multiple superimposed tectonic processes, with varying depths in each process. Consequently, multiple fault-controlled bodies exist vertically, with tight sections of a certain thickness—either bedrock or poorly permeable fractured reservoirs—interspersed between them. When the reservoir is subjected to tensile stress, the two fault planes move in opposite directions along the direction perpendicular to the fault plane, filling the space between them with tight bedrock. Subsequently, under translational stress, the two fault planes move in opposite directions along the fault plane, increasing the degree of formation fracturing. The spaces between the fragmented reservoirs are then sealed by tight bedrock, resulting in some condensate gas remaining unexploited. The SHB4-13H well model in the Shunbei 4 fault zone is relatively dispersed, mainly because it is subjected to both tensile and translational stresses, leading to increased formation fracturing. The tight bedrock sealing resulted in the various reservoirs being distributed around the main cross-section, with no large pore channels connecting them. After well SHB4-13H began production, only the condensate gas in the drilled reservoir was utilized; the condensate gas in the other reservoirs formed a sealed, residual gas layer. Figure 12 As shown in e.

[0119] 4. Bottom water sealing type

[0120] The Shunbei No. 4 fault zone is currently in the middle to late production stage, with a rapid rise in bottom water, resulting in some bottom water-sealed residual gas. In the SHB4-12H well, bottom water coning has led to formation water entering the wellbore, blocking the condensate gas production and migration pathways, thus forming bottom water-sealed residual gas (e.g., Figure 12 (As shown in c); due to the rapid rise of the bottom water and the high position of the well bottom, some cone-shaped reservoirs below the well bottom cannot produce condensate gas in time, forming a series of residual mound-shaped gas deposits (such as...). Figure 12 (as shown in d).

[0121] Residual gas distribution pattern in well groups:

[0122] 1. Isolated type

[0123] The condensate gas reservoirs in the Shunbei 4 zone are distributed along the Shunbei 4 fault zone. The tectonic stress is tensile stress, and the models are relatively dispersed. There are many reservoirs surrounding the main fault but not connected to it, such as in the SHB44X and SHB45X well group models. The condensate gas in the main fault reservoir is utilized, while the condensate gas in the reservoirs surrounding the main fault is not utilized, forming isolated residual gas. The tectonic stress is compressive stress, and the models are more compact, essentially forming a single unit, such as in the SHB43X and SHB46X well group models. There are a small amount of residual condensate gas around these reservoirs that are not connected to the main fault surface (e.g., Figure 12 (as shown in f).

[0124] 2. Retention type near the air-driven channel

[0125] For some well groups employing gas injection for pressure stabilization and gas injection for oil displacement development, a highly permeable gas drive channel often exists between the injection well and the production well. During the gas drive process, due to the blockage of dense bedrock around the channel, some condensate gas in small pores remains undisplaced and is thus retained as residual gas. For example, in the SHB46X well group, a highly permeable seepage channel exists between the two wells. When natural gas is injected into the SHB4-8H well, the displaced condensate gas moves towards the SHB46X well. The permeability around the channel is low, and this portion of condensate gas remains unused during the displacement process, forming retained residual gas near the gas drive channel (e.g., condensate gas in the vicinity of the channel). Figure 12 (as shown in g).

[0126] 3. Control over the relationship between injection and production

[0127] For well groups with good connectivity, injecting a flowing medium into one well, driven by the external fluid, pushes the condensate gas around the injection well toward the production well, gradually enriching the condensate gas around the production well. As shown in the SHB43X well group, natural gas (light components) is injected first to displace the condensate gas. The injected natural gas then drives the upper condensate gas toward the adjacent well, forming an overlapping slope (e.g., Figure 12 (As shown in i). If nitrogen (heavy components) is injected to displace condensate gas, then the density of nitrogen is greater than that of condensate gas. The nitrogen sinks below the formation, driving the bottom condensate gas to move towards the wellbore (e.g., ...). Figure 12 (as shown in h).

[0128] The Shunbei No. 4 fault zone contains fault-controlled carbonate fracture-cavity reservoirs. Influenced by multiple phases of large-scale strike-slip fault tectonic movements, the internal structure of these fault-controlled reservoirs is more complex and heterogeneous. Using Petrel geological modeling software, a deterministic modeling approach was applied to characterize the fault-controlled bodies, completing a three-dimensional geological model of the Shunbei No. 4 fault zone. The fitting error between the geological model's condensate gas reserves and dynamic reserves was only 6.25%. Subsequently, production history fitting was completed for 14 units, with a fitting error of less than 4%. This indicates that the geological model can effectively represent the actual geological characteristics, laying the foundation for studying the distribution patterns of remaining condensate gas in the carbonate condensate gas reservoirs of the Shunbei No. 4 fault zone.

[0129] In the study of residual gas distribution in carbonate condensate gas reservoirs controlled by the Shunbei No. 4 fault zone, the distribution pattern of residual gas in single wells is closely related to the tectonic movements experienced by the strike-slip faults: Tensile stress leads to a more dispersed model, resulting in poor connectivity between reservoirs, and bedrock can further impede the flow between two fault surfaces. This means that during well production, only the condensate gas from one fault surface is utilized, while residual gas forms on the other. Conversely, compressive and translational stresses result in a more concentrated model, with better connectivity between reservoirs, leading to isolated residual gas formations around the model. When subjected to both tensile and translational stresses, the fault surfaces become more fragmented, causing reservoirs of varying sizes to be further impeded by dense bedrock, forming multiple residual condensate gas reservoirs. Rising bottom water, clogging the well bottom, also hinders condensate gas extraction, resulting in residual condensate gas.

[0130] The distribution of residual gas in a well group is mainly controlled by geological and development factors. Whether in a single well or a well group, due to tectonic stress, a portion of scattered residual condensate gas will exist around the fault surface. When two wells in the model have a highly permeable channel, during natural gas drive, some condensate gas will be trapped in the upper or lower part of the gas drive channel due to tight bedrock, forming stagnant residual gas near the unused gas drive channel. During natural gas drive, natural gas, being a light component, diffuses after entering the formation, displacing the upper condensate gas and flowing towards the bottom of the production well. The condensate gas accumulates around the production well and at the bottom of the formation. When nitrogen is injected, the nitrogen diffuses, displacing the condensate gas at the bottom of the formation and flowing towards the bottom of the production well. The condensate gas accumulates around the production well and in the upper part of the formation.

[0131] Based on the study of the residual gas distribution characteristics of the fault-controlled carbonate condensate gas reservoir in the Shunbei No. 4 zone, the distribution patterns of residual gas in the fault-controlled carbonate condensate gas reservoir are divided into two main categories according to the differences between single wells and well groups: single-well residual gas and well group residual gas. Based on the main controlling factors of the distribution characteristics of single-well and well group residual gas, they are further subdivided into seven subcategories. Single-well residual gas is classified as: isolated single-well type, tight sealing type, bottom water conical type, bottom water low-floating mound type, and tectonic stress-controlled type. Unit well group residual gas is classified as: isolated well group type, gas drive channel-residual type, and injection-production relationship-controlled type.

[0132] Implement column 3

[0133] like Figure 13 As shown, an analysis device for residual condensate gas distribution patterns 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, which, when executed, enables the at least one processor to perform the method for analyzing residual condensate gas distribution patterns in fault-controlled carbonate rocks as described in the foregoing embodiments. The input / output interface may include a display, keyboard, mouse, and USB interface for inputting and outputting data; a power supply provides electrical power to the electronic devices.

[0134] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0135] When the integrated units of this invention are implemented as software functional units and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this invention, 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 to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0136] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks, characterized in that, Includes the following steps: S1: Different reservoir grades are classified according to reservoir development patterns and structural levels. Step S1 also includes: dividing the fault-controlled reservoir into five levels according to the reservoir development model and development structural level: strike-slip fault zone, fault-controlled body, fault body-cavity-chaotic body, cavity-filling, and microfracture, and determining the corresponding threshold cutoff according to different levels using deterministic modeling methods. S2: Establish corresponding models according to different reservoir levels, and merge the models of different levels to obtain a three-dimensional geological model; S3: After coarsening the three-dimensional geological model, numerical simulation is used to establish mathematical models for each individual well and well group, and production history fitting is completed; S4: Based on the fitting results, the distribution pattern of residual condensate gas in the fault-controlled carbonate condensate gas reservoir is obtained; Step S4 includes: generating a pressure change fitting map based on the pressure fitting before and after production, comparing the pressure change fitting maps, and clarifying the distribution pattern of the remaining condensate gas in the fault-controlled carbonate condensate gas reservoir. The distribution pattern includes distribution characteristics and distribution type.

2. The method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks according to claim 1, characterized in that, Step S1 includes: establishing a reservoir development model using seismic data, drilling data, core samples, logging and loss-of-life records, as well as structural location, reservoir type and spatial contact relationship.

3. The method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks according to claim 1, characterized in that, Step S2, which establishes corresponding models according to different reservoir levels, includes: the strike-slip fault zone is mainly characterized by fault-controlled bodies, which are composed of fault bodies, cavern-like bodies, and chaotic bodies. Therefore, structural tensor, coherent energy gradient, and variance seismic attribute volume are used to characterize them respectively. The corresponding thresholds are determined by combining well and seismic methods, and contour models of fault bodies, cavern-like bodies, and chaotic bodies are established. The cave-like contour model is used as a constraint, and a target-based modeling method is used to build a three-dimensional model of the internal lattice structure layer by layer. For the microcracks, an improved discrete crack network simulation method was adopted to establish a microcrack network model that conforms to the actual morphology in the field outcrops.

4. The method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks according to claim 1, characterized in that, Step S3 also includes: establishing mathematical models for each individual well and well group through reservoir numerical simulation to fit the production history.

5. The method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks according to claim 1, characterized in that, Based on the distribution characteristics and types of residual condensate gas in the fault-controlled carbonate condensate gas reservoir, the main controlling factors of the distribution of residual condensate gas in the fault-controlled carbonate condensate gas reservoir are identified, and the distribution pattern of residual condensate gas in the fault-controlled carbonate condensate gas reservoir is obtained.

6. The method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks according to claim 5, characterized in that, The distribution types of residual condensate gas in the single well include isolated type, structure-controlled type, tight-sealed type, and bottom water-sealed type.

7. The method for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks according to claim 6, characterized in that, The distribution types of residual condensate gas in the well group include isolated type, stagnant type near the gas drive channel, and injection-production relationship controlled type.

8. A device for analyzing the distribution pattern of residual condensate gas in fault-controlled carbonate rocks, characterized in that, The fault-controlled carbonate rock residual condensate gas distribution pattern analysis device stores program instructions, which, when executed by at least one processor, are used to implement the fault-controlled carbonate rock residual condensate gas distribution pattern analysis method as described in any one of claims 1 to 7.

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