Gas cap oil reservoir development method and system

Abstract

This application discloses a method and system for developing gas cap reservoirs, comprising: determining sedimentary microfacies information of a target interval based on well logging information and seismic data; dividing the target interval into physical property bands based on the sedimentary microfacies information to obtain high-quality and low-quality physical property bands; setting a first rhombic well pattern for the high-quality physical property bands in the target interval; and setting a second rhombic well pattern for the low-quality physical property bands in the target interval; wherein the minor axis length of the first rhombic well pattern is smaller than the minor axis length of the second rhombic well pattern. This gas cap reservoir development method can cut off the miscibility channel between the oil and gas zones, suppress gas cap expansion upwards to prevent gas channeling, and provide water drive energy downwards, thereby improving the development effect of gas cap reservoirs.

Description

Technical Field

[0001] This application relates to the field of oil reservoir development technology, and in particular to a gas cap reservoir development method and a gas cap reservoir development system. Background Technology

[0002] In the field of oil reservoir development technology, there are areas where gas layers are located at the top of oil layers. These areas are called gas cap reservoirs in oil and gas zones. Currently, the technology only extracts oil from oil layers and gas from gas layers. The current technology mostly treats gas cap reservoirs in oil and gas zones as idle reservoirs, which makes them untapped and results in low oil reservoir development efficiency. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0004] Therefore, a first aspect of the present invention provides a method for developing gas cap reservoirs.

[0005] A second aspect of the present invention provides a gas cap reservoir development system.

[0006] In view of this, a gas cap reservoir development method is proposed according to a first aspect of the embodiments of this application, comprising:

[0007] Based on well logging information and seismic data, the sedimentary microfacies information of the target interval was determined;

[0008] Based on the sedimentary microfacies information, the target layer is divided into physical property bands to obtain high-quality and low-quality physical property bands.

[0009] A first diamond-shaped well pattern is set in the high-quality physical property strips within the target layer;

[0010] A second diamond-shaped well pattern is set in the inferior physical property strips within the target layer;

[0011] The minor axis length of the first rhombic well pattern is smaller than that of the second rhombic well pattern.

[0012] In one feasible implementation, the step of determining the sedimentary microfacies information of the target interval based on well logging information and seismic data includes:

[0013] Based on well logging records and logging data, the core sedimentary characteristics of the target formation were determined;

[0014] Based on the core sedimentary characteristics and regional logging response characteristics, a first correspondence between lithofacies and logging curve characteristics is established.

[0015] Based on well logging curves and seismic data, a second correspondence between waveform attributes and well logging curve characteristics is established;

[0016] Based on the first and second correspondences, the depositional microfacies information of the target layer is determined.

[0017] In one feasible implementation, the step of establishing a first correspondence between lithofacies and logging curve characteristics based on the core sedimentary characteristics and regional logging response characteristics includes:

[0018] Based on well logging records and logging data, natural gamma, photoelectric absorption cross section index, compensated density and compensated neutron porosity were obtained as the original curves for well logging phase analysis.

[0019] Based on the original logging facies analysis curve, a first correspondence between lithofacies and logging curve characteristics is established.

[0020] In one feasible implementation, the step of establishing the first correspondence between lithofacies and well logging curve characteristics based on the original logging facies analysis curve includes:

[0021]

[0022] Among them, S dn This is the first correspondence. To compensate for neutron porosity, ρ c To compensate for density.

[0023] In one feasible implementation, the step of establishing a second correspondence between waveform attributes and well logging curve characteristics based on well logging curves and seismic data includes:

[0024] Seismic facies analysis is performed based on the reflection structure, continuity, amplitude, frequency, and geometric shape of wave groups on seismic profiles to obtain seismic analysis data;

[0025] Based on the aforementioned seismic analysis data and well logging curve characteristics, an initial correspondence is established;

[0026] The initial correspondence is processed by cluster analysis to obtain the second correspondence between waveform attributes and logging curve characteristics.

[0027] In one feasible implementation, the step of determining the depositional microfacies information of the target layer based on the first correspondence and the second correspondence includes:

[0028] The second correspondence in the time domain is converted into a second correspondence in the frequency domain;

[0029] Seismic signal difference is calculated from the second correspondence in the frequency domain, and combined with the first correspondence to generate a seismic phase map;

[0030] Based on the seismic facies map, the sedimentary microfacies information of the target layer is determined.

[0031] In one feasible implementation, the conversion of the second correspondence in the time domain to a second correspondence in the frequency domain is achieved by the following formula:

[0032]

[0033] Where a(f) is the interpolation function value, a n is the frequency domain signal; n is the discrete point number; Δf is the frequency domain sampling interval; f is the frequency value at the point to be interpolated; i is the imaginary unit.

[0034] In one feasible implementation, the step of dividing the target layer into physical property bands based on the sedimentary microfacies information to obtain high-quality and low-quality physical property bands includes:

[0035] The region corresponding to the river channel in the sedimentary microfacies information is taken as a high-quality physical property strip;

[0036] The regions in the sedimentary microfacies information that correspond to the channel direction are designated as inferior physical property bands.

[0037] In one feasible implementation, the major axis of the first rhomboid well pattern is arranged along the direction of the river channel, and the minor axis of the first rhomboid well pattern is perpendicular to the direction of the river channel.

[0038] In one feasible implementation, an oil and gas zone is identified within the target stratigraphic segment;

[0039] Based on the first and second diamond-shaped well patterns, injection wells inject displacement fluid to form an injection barrier and cut off the miscibility channel between the oil and gas zones;

[0040] Based on the production wells of the first and second rhomboid well networks, oil reservoirs in the oil and gas area are collected through intermittent injection and production.

[0041] In one feasible implementation, the step of harvesting oil from the oil and gas reservoir in the oil and gas area through intermittent injection and production using the production wells based on the first and second rhomboid well patterns includes:

[0042] Clearly define the oil and gas boundaries between oil and gas zones and gas zones within the target stratigraphic unit;

[0043] Production wells in the first and second diamond-shaped well networks with a distance greater than a first threshold from the oil and gas boundary are selected to collect oil from the oil and gas reservoir within the oil and gas zone.

[0044] In one feasible implementation, after the oil reservoir in the oil and gas zone has been harvested, the gas reservoir in the oil and gas zone is harvested through the production well.

[0045] In one feasible implementation, the gas cap reservoir development method further includes:

[0046] Adjust the injection rate of the injection well and the production rate of the production well to achieve a balance at the oil and gas interface in the oil and gas zone.

[0047] In one feasible implementation, the step of adjusting the injection rate of the injection well and the production rate of the production well to achieve oil and gas interface balance in the oil and gas zone includes:

[0048] Based on production and test records, a multiphase flow theoretical equilibrium model was established.

[0049] Based on the aforementioned multiphase flow theory equilibrium model, the injection and lift parameters are determined.

[0050] In one feasible implementation, the step of establishing a multiphase flow theoretical equilibrium model based on production records and test records includes:

[0051] The theoretical equilibrium model of the multiphase seepage is established by the following formula:

[0052]

[0053] in, Let be the change in the potential function. γ is the longitudinal displacement change, and γ is the force acting on the flow element point. c The force required to stabilize the unit fluid, where Δγ is the difference in bulk density between oil and gas, k is the permeability, and μ is the viscosity of the oil. Let γ be the potential function, P be the force acting on the element, and γ be the force. g Let Z be the radius of operation, Z be the longitudinal displacement, Q be the limiting oil production, and h be the maximum oil production. e In order to utilize thickness, μ0 represents the degree of perforation opening, and μ0 represents the viscosity of the crude oil under formation conditions.

[0054] In one feasible implementation, the ratio of the major axis distance to the minor axis distance in the first rhomboid well pattern is greater than or equal to 1.5.

[0055] In one feasible implementation, the distance between the minor axes in the first diamond-shaped well pattern is 300m to 400m.

[0056] According to a second aspect of the embodiments of this application, a gas cap reservoir development system is provided, comprising:

[0057] The confirmation unit is used to determine the sedimentary microfacies information of the target layer based on well logging information and seismic data.

[0058] A partitioning unit is used to divide the target layer into physical property bands based on the sedimentary microfacies information, and to obtain high-quality physical property bands and low-quality physical property bands.

[0059] A drawing unit, the drawing unit being used to set a first diamond-shaped well pattern in the high-quality physical property strips within the target layer;

[0060] The drawing unit is also used to set a second diamond-shaped well pattern in the inferior physical property strips within the target layer;

[0061] The minor axis length of the first rhombic well pattern is smaller than that of the second rhombic well pattern.

[0062] Compared with the prior art, the present invention has at least the following beneficial effects: The gas cap reservoir development method provided in this application first drives the sedimentary microfacies information of the target layer based on well logging information and seismic data, and then divides the physical properties of the target layer based on the sedimentary microfacies information, dividing high-quality physical property bands and low-quality physical property bands. A first diamond-shaped well network is set for the area corresponding to the high-quality physical property bands in the target layer, and a second diamond-shaped well network is set for the area corresponding to the low-quality physical property bands in the target layer. This setting allows for the collection of oil in the gas cap reservoir based on the first and second diamond-shaped well networks. By setting the first and second diamond-shaped well networks, the well network can be matched with the sedimentary microfacies information of the target layer, so that the injection wells in the well network can cut off the miscibility channel between the oil and gas areas, suppress gas cap expansion upwards, prevent gas channeling, and provide water drive energy downwards, thereby improving the development effect of the gas cap reservoir. Attached Figure Description

[0063] 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 scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0064] Figure 1 A schematic flowchart illustrating the steps of a gas cap reservoir development method according to an embodiment of this application;

[0065] Figure 2 A schematic diagram of the physical property striping of another embodiment of the gas cap reservoir development method provided in this application;

[0066] Figure 3 A schematic diagram of the working states of the first and second diamond-shaped well patterns in a gas cap reservoir development method according to another embodiment of this application. Detailed Implementation

[0067] To better understand the above technical solutions, the technical solutions of the embodiments of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0068] like Figure 1 As shown in the embodiments of this application, a method for developing gas cap reservoirs is proposed, comprising:

[0069] Step 101: Determine the sedimentary microfacies information of the target interval based on well logging information and seismic data. Well logging settings allow for the determination of sedimentary microfacies information vertically within the target interval, while seismic data allows for the determination of sedimentary microfacies information horizontally. The sedimentary microfacies information determined by combining well logging and seismic data is more accurate.

[0070] Step 102: Based on sedimentary microfacies information, the target layer is divided into physical property bands to obtain high-quality and low-quality physical property bands. Based on sedimentary microfacies information, physical properties can be divided into multiple target layers, thereby identifying high-quality and low-quality physical property bands. It is understood that high-quality physical property bands may include multiple levels of physical property bands, with different properties between these levels; similarly, low-quality physical property bands may also include multiple levels of physical property bands, with different properties between these levels. It is understood that the physical properties of high-quality physical property bands are superior to those of low-quality physical property bands.

[0071] Step 103: Set up a first diamond-shaped well pattern in the high-quality physical property strips within the target layer. It can be understood that the endpoints of the first diamond-shaped well pattern are the production wells, and the wells in the central area of ​​the first diamond-shaped well pattern are the injection wells.

[0072] Step 104: Set up a second diamond-shaped well pattern in the poor physical property strips within the target layer. It can be understood that the endpoints of the second diamond-shaped well pattern are the production wells, and the wells in the central area of ​​the second diamond-shaped well pattern are the injection wells.

[0073] The minor axis length of the first diamond-shaped well pattern is shorter than that of the second diamond-shaped well pattern. The minor axis length of the first diamond-shaped well pattern located in the high-quality physical property zone is shorter than that of the second diamond-shaped well pattern located in the low-quality physical property zone. This is more conducive to the injection well cutting off the miscible channel between the oil and gas zones, suppressing gas cap expansion upwards and preventing gas channeling; and providing water drive energy downwards, thus improving the development effect of gas cap reservoirs.

[0074] The gas cap reservoir development method provided in this application first uses well logging information and seismic data to drive the sedimentary microfacies information of the target layer. Then, based on the sedimentary microfacies information, the physical properties of the target layer are divided into high-quality physical property bands and low-quality physical property bands. A first diamond-shaped well pattern is set for the area corresponding to the high-quality physical property bands in the target layer, and a second diamond-shaped well pattern is set for the area corresponding to the low-quality physical property bands in the target layer. This setup allows for oil collection in the gas cap reservoir based on the first and second diamond-shaped well patterns. By setting the first and second diamond-shaped well patterns, the well pattern can be matched with the sedimentary microfacies information of the target layer, enabling the injection wells in the well pattern to cut off the miscibility channel between the oil and gas areas, suppress gas cap expansion upwards to prevent gas channeling, and provide water drive energy downwards, thereby improving the development effect of the gas cap reservoir.

[0075] In some examples, the steps for determining the sedimentary microfacies information of a target interval based on well logging information and seismic data include: determining the core sedimentary characteristics of the target interval based on well logging records and well logging data; establishing a first correspondence between lithofacies and well logging curve characteristics based on core sedimentary characteristics and regional well logging response characteristics; establishing a second correspondence between waveform attributes and well logging curve characteristics based on well logging curves and seismic data; and determining the sedimentary microfacies information of the target interval based on the first and second correspondences.

[0076] Based on well logging records and logging data, the core sedimentary characteristics of the target interval are determined; based on the core sedimentary characteristics and regional well logging response characteristics, the first correspondence between lithofacies and well logging curve characteristics is established, and the distribution of sedimentary microfacies can be determined vertically based on the well group of the target interval.

[0077] Based on well logging curves and seismic data, a second correspondence between waveform attributes and well logging curve characteristics is established, which can clarify the distribution of sedimentary microfacies between wells and determine the distribution of sedimentary microfacies on the horizontal line of the target layer.

[0078] Based on the first and second correspondences, the sedimentary microfacies information of the target layer can be determined. The sedimentary microfacies information of the target layer can be clearly defined from both the vertical and horizontal lines, making the determination of the sedimentary microfacies distribution of the target layer more accurate.

[0079] In some examples, the steps for establishing the first correspondence between lithofacies and logging curve characteristics based on core sedimentary characteristics and regional logging response characteristics include: obtaining natural gamma, photoelectric absorption cross section index, compensated density and compensated neutron porosity based on logging records and logging data as the original logging facies analysis curves; and establishing the first correspondence between lithofacies and logging curve characteristics based on the original logging facies analysis curves.

[0080] Core data can be collected from the target stratigraphic region to perform lithological descriptions for each logging facies and establish the relationship between logging facies and lithofacies. Based on the characteristics of the logging data, Qapi (natural gamma), Ipae (photoelectric absorption cross section index), ρc (compensated density), and φnc (compensated neutron porosity) can be selected as the original curves for logging facies analysis. These curves are sensitive to lithological information and relatively less affected by fluids in the rock pores, making them suitable for logging facies-lithhofacies analysis by correlating the single-well facies at existing well locations with seismic attribute characteristics. Furthermore, seismic facies analysis can be performed using parameters such as wave group reflection structure, continuity, amplitude, frequency, and geometry on seismic profiles. This establishes the correspondence between waveform attributes and logging curve characteristics, and cluster analysis is performed to develop algorithms. These algorithms focus on identifying and combining channel microfacies that are significant for inter-well connectivity, further studying the configuration and spatial distribution characteristics of various sedimentary systems.

[0081] In some examples, the steps for establishing a primary correspondence between lithofacies and logging curve characteristics based on the original logging facies analysis curves include:

[0082]

[0083] Among them, S dn This is the first correspondence. To compensate for neutron porosity, ρ c To compensate for density.

[0084] Understandably, the first correspondence is a quantitative indication of the difference between density and compensated neutron porosity logging.

[0085] To enhance the effectiveness of lithology identification, a calculation formula for clarifying the first correspondence is provided, making the determination of the first relationship more accurate. Here, Sdn is a quantitative indicator representing the difference between density and compensated neutron porosity logging.

[0086] In some examples, the steps for establishing a second correspondence between waveform attributes and well logging curve characteristics based on well logging curves and seismic data include: performing seismic facies analysis based on the reflection structure, continuity, amplitude, frequency, and geometric shape of wave groups on the seismic profile to obtain seismic analysis data; establishing an initial correspondence based on the seismic analysis data and well logging curve characteristics; and processing the initial correspondence through cluster analysis to obtain a second correspondence between waveform attributes and well logging curve characteristics.

[0087] By correlating existing well locations with single-well facies and seismic attribute characteristics, seismic facies analysis is performed using parameters such as reflection structure, continuity, amplitude, frequency, and geometric shape of wave groups on seismic profiles. A correspondence between waveform attributes and well logging curve characteristics is established, and cluster analysis is conducted to form an algorithm that can obtain a second correspondence. The second correspondence is used to identify and combine channel microfacies that are important for inter-well connectivity, and further study the configuration and spatial distribution characteristics of various sedimentary systems.

[0088] In some examples, the steps of determining the sedimentary microfacies information of the target layer based on the first and second correspondences include: converting the second correspondence in the time domain into a second correspondence in the frequency domain; performing seismic signal difference analysis on the second correspondence in the frequency domain and combining it with the first correspondence to generate a seismic facies map; and determining the sedimentary microfacies information of the target layer based on the seismic facies map.

[0089] Seismic facies analysis based on waveform classification can be used to compare seismic data traces within a specific layer, classifying seismic reflections representing the same sedimentary facies into a single category. This reveals the planar distribution pattern of seismic anomalies and thus exposes the same sedimentary facies zone. The process involves first transforming the time-domain seismic data within the target layer to the frequency domain, then interpolating the frequency-domain unequal-length seismic signals, followed by frequency-domain waveform clustering and clustering based on well logging facies calibration results. Finally, a seismic facies map is generated based on the waveform classification results, and a sedimentary facies map is compiled through comprehensive geological analysis.

[0090] In some examples, the second correspondence in the time domain is converted to the second correspondence in the frequency domain using the following formula:

[0091]

[0092] Where a(f) is the interpolation function value, a n is the frequency domain signal; n is the discrete point number; Δf is the frequency domain sampling interval; f is the frequency value at the point to be interpolated; i is the imaginary unit.

[0093] The function sinc(x) = sin(x) / x is called the sinc function, so the above formula is also called the frequency domain sinc interpolation formula. Accurate sinc interpolation is difficult to achieve in reality because it requires an infinitely long signal, while actual signals are truncated into finite-length discrete signals.

[0094] By further derivation based on the above formula, the discrete sinc interpolation formula in the frequency domain of a finite-length discrete signal can be obtained:

[0095]

[0096] Where N is the signal frequency and d is the signal length.

[0097] As can be seen from the above formula, the discrete sincd interpolation function uses all points in the signal frequency domain, which reduces computational efficiency when N is large. Therefore, in practical applications, the sincd interpolation function can be truncated, and only a few terms can be used for interpolation.

[0098] This application embodiment combines well logging and logging data within the work area to study the sedimentary characteristics of core samples taken from the target layer, and establishes a correspondence between lithofacies and well logging curve characteristics by combining regional well logging response characteristics.

[0099] On the well profile, a seismic response model is established by combining well logging curves and seismic response characteristics. Seismic facies analysis is performed using parameters such as reflection structure, continuity, amplitude, frequency, and geometric shape of wave groups on the seismic profile. The correspondence between waveform attributes and well logging curve characteristics is established, and cluster analysis is performed to form an algorithm. The algorithm focuses on identifying and combining channel microfacies that are important for inter-well connectivity, and further studies the configuration and spatial distribution characteristics of various sedimentary systems.

[0100] Seismic facies analysis based on waveform classification involves comparing seismic traces within a specific layer using waveform characteristics. Seismic reflections representing the same sedimentary facies are grouped together, revealing the planar distribution patterns of seismic anomalies and thus indicating the same sedimentary facies zone. This process first transforms the time-domain seismic data within the target layer to the frequency domain, then performs frequency-domain unequal-length seismic signal interpolation, followed by frequency-domain waveform clustering and clustering based on well logging facies calibration results. Finally, a seismic facies map is generated based on the waveform classification results, and a sedimentary facies map is compiled through comprehensive geological analysis.

[0101] like Figure 2 As shown, in some examples, the steps of dividing the target layer into physical property bands based on sedimentary microfacies information and obtaining high-quality and low-quality physical property bands include: taking the area corresponding to the channel in the sedimentary microfacies information as the high-quality physical property band; and taking the area corresponding to the channel in the sedimentary microfacies information as the low-quality physical property band.

[0102] Based on the various sedimentary microfacies identified through well-seismic analysis, the distribution range of physical properties is statistically analyzed through well logging interpretation and classified into 2-3 categories, such as... Figure 2As shown, the distribution range of the physical property stripes is delineated on the plan view. A matching diamond-shaped well network is designed based on the distribution of these stripes. This network includes: the long axis of the well network is along the river channel, and the short axis is perpendicular to the river channel. In the inter-channel area, the long axis of the well network is slightly shorter, resulting in relatively uniform injection and production. In the initial production phase, intermittent injection and production are implemented near the gas cap area. After achieving the recovery rate, a row of oil wells near the gas cap is converted to injection, forming a row-injection-row-production pattern. This establishes a water injection barrier, cuts off the miscibility channel between the oil and gas areas, inhibits gas cap expansion upwards to prevent gas channeling, and provides water drive energy downwards to improve the development effect of the gas cap reservoir.

[0103] In some examples, the major axis of the first rhombus well pattern is arranged along the direction of the river channel, and the minor axis of the first rhombus well pattern is perpendicular to the direction of the river channel.

[0104] The long axis of the first diamond-shaped well pattern is arranged along the direction of the river channel, and the short axis of the first diamond-shaped well pattern is perpendicular to the direction of the river channel. This allows the displacement fluid injected through the first diamond-shaped well pattern to flow preferentially along the direction of the river channel, which can better establish a water injection barrier, cut off the mixing channel between the oil and gas areas, suppress gas cap expansion upwards, prevent gas channeling, and provide water drive energy downwards, thereby improving the development effect of gas cap reservoirs.

[0105] like Figure 3 As shown, the attached Figure 3 The direction of the middle arrow indicates the flow direction of the displacement fluid injected through the injection well. In some examples, oil and gas zones are identified in the target formation. The displacement fluid is injected through the injection wells based on the first and second diamond well patterns to form an injection barrier and cut off the miscible channel between the oil and gas zones. The production wells based on the first and second diamond well patterns are used to collect oil from the reservoirs in the oil and gas zones through intermittent injection and production.

[0106] After completing the layout of the first and second diamond-shaped well patterns, displacement fluid can be injected through injection wells. This displacement fluid forms an injection barrier, cutting off the miscibility channel between the oil and gas zones. Production wells can then extract the oil reservoir within the oil and gas zone. Figure 3 As shown, as the oil reservoir is produced, the oil level will decrease, and the gas at the top of the oil layer will move downwards, which may cause gas channeling. In this case, continuous injection of displacement fluid through injection wells can achieve oil and gas balance, avoid gas channeling, and facilitate the efficient exploitation of gas cap reservoirs.

[0107] In some examples, the steps of collecting oil reservoirs in the oil and gas zone through intermittent injection and production based on the production wells of the first and second diamond well networks include: identifying the oil and gas boundary between the oil and gas zone and the gas zone in the target interval; and selecting production wells in the first and second diamond well networks whose distance from the oil and gas boundary is greater than a first threshold to collect oil reservoirs in the oil and gas zone.

[0108] This application further clarifies how to determine production wells in the first and second rhomboid well networks. Only production wells in the first and second rhomboid well networks with a distance greater than a first threshold from the oil and gas boundary are selected to collect oil reservoirs within the oil and gas zone. This keeps wells closer to the oil and gas boundary idle, further ensuring the balance of the oil and gas interface and facilitating the efficient exploitation of gas cap reservoirs.

[0109] In some examples, after oil reservoirs in an oil and gas zone have been harvested, gas reservoirs within the zone are harvested through production wells.

[0110] After the oil reservoir in the gas cap reservoir is developed, gas can be extracted from all the production wells in the first and second diamond well networks. If the production wells that were idle during the oil production process can be put into use, it will be beneficial to the extraction of gas from the gas cap reservoir.

[0111] In some examples, gas cap reservoir development methods also include adjusting the injection rate of injection wells and the production rate of production wells to balance the oil and gas interface in the oil and gas zone.

[0112] By adjusting the injection rate of injection wells and the production rate of production wells, the oil and gas interface in the oil and gas zone can be balanced, which can prevent frequent movement of the oil and gas interface and greatly reduce the probability of gas channeling, making the development of gas cap reservoirs safer.

[0113] In some examples, the steps to adjust the injection rate of injection wells and the production rate of production wells to achieve oil and gas interface equilibrium in the oil and gas zone include: establishing a multiphase flow theoretical equilibrium model based on production and test records; and determining injection and lift parameters based on the multiphase flow theoretical equilibrium model.

[0114] A multiphase flow theoretical equilibrium model is established based on actual and test data from the production process. Then, the injection and lifting parameters are determined based on the multiphase flow theoretical equilibrium model, which is conducive to achieving oil-gas interface equilibrium.

[0115] In some examples, the steps for establishing a multiphase flow theoretical equilibrium model based on production and test records include:

[0116] A multiphase flow theoretical equilibrium model is established using the following formula:

[0117]

[0118] in, Let be the change in the potential function. γ is the longitudinal displacement change, and γ is the force acting on the flow element point. c The force required to stabilize the unit fluid, where Δγ is the difference in bulk density between oil and gas, k is the permeability, and μ is the viscosity of the oil. Let γ be the potential function, P be the force acting on the element, and γ be the force.g Let z be the radius of operation, z be the longitudinal displacement, Q be the limiting oil production, and h be the maximum oil production. e In order to utilize thickness, μ0 represents the degree of perforation opening, and μ0 represents the viscosity of the crude oil under formation conditions.

[0119] The aforementioned formulas, combined with field production and testing results, allow for the analysis of changes in the oil-gas interface and the three-phase displacement laws of oil, gas, and water, establishing a multiphase flow theory equilibrium equation. Based on this, the distance between the perforated well section and the gas cap, the optimal non-gas channeling oil production rate, and the reasonable injection rate can be designed. This can form a water injection barrier, cutting off the miscible channel between the oil and gas zones, suppressing gas cap expansion upwards to prevent gas channeling, and providing water drive energy downwards, ultimately improving the development effect of the gas cap reservoir.

[0120] In this embodiment, sedimentary facies are identified through well logging interpretation. Starting from the characteristics of single-well curves, the curve characteristics of the target layer are categorized, and corrected and identified in conjunction with core characteristics to determine the single-well logging facies. Seismic inversion studies the logging response characteristics of the target interval based on well logging and seismic data. On the well profile, a seismic response model is established by combining the logging curves and seismic response characteristics. Finally, seismic facies analysis is performed using parameters such as the reflection structure, continuity, amplitude, frequency, and geometric shape of wave groups on the seismic profile. The correspondence between waveform attributes and logging curves is established, and cluster analysis is performed to form an algorithm. The algorithm focuses on identifying and combining channel microfacies that are important for inter-well connectivity to further study the configuration and spatial distribution characteristics of various sedimentary systems. Well pattern design technology mainly refers to designing personalized well patterns based on the distribution range and shape of different physical property intervals, so that the injection and production mainstream lines are associated with the sedimentary direction to maximize the utilization of remaining oil. Adjusting the injection-production balance through seepage theory mainly involves studying the interaction between the three phases of oil, gas, and water near the oil-gas interface, deriving balance parameters, guiding the regulation of injection and production, and achieving the goal of maintaining the relative stability of the oil-gas interface.

[0121] Example:

[0122] This invention's method for maintaining the stability of the oil-gas interface during the development of a gas-cap reservoir was applied to a gas-cap reservoir in Mangyshtau Region, Kazakhstan. This reservoir is a sandstone reservoir with deltaic plain and frontal subfacies sediments, containing microfacies such as channels, swamps, and estuary bars. It exhibits well-developed positive structures and is a layered sandstone reservoir with a gas cap. The oil-gas transition zone is 200-300 meters wide. In previous development processes, to prevent gas channeling, wells were uniformly distributed 300-500 meters away from the gas cap, resulting in low utilization of the oil-gas transition zone and enrichment of remaining oil. Therefore, rationally controlling injection and production parameters to maintain the stability of the oil-gas interface is fundamental to utilizing the remaining oil.

[0123] Step 1: Using macroscopic core description data from 9 cored wells in the study area and imaging logging data from 2 wells, combined with conventional logging curves, lithological characteristics were observed and identified. Based on the characteristics of the logging data, Qapi (natural gamma), Ipae (photoelectric absorption cross section index), ρc (compensated density), and φnc (compensated neutron porosity) were selected as the original curves for logging facies analysis. These curves are sensitive to lithological information and relatively less affected by fluids in the rock pores, making them suitable for logging facies-lithofacies analysis to establish the relationship between logging facies and lithofacies.

[0124] Step 2: By correlating the existing well locations and single-well facies with seismic attribute characteristics, seismic facies analysis is performed using parameters such as reflection structure, continuity, amplitude, frequency, and geometric shape of wave groups on the seismic profile. The correspondence between waveform attributes and well logging curves is established, and cluster analysis is conducted to form an algorithm. The algorithm focuses on identifying and combining channel microfacies that are important for inter-well connectivity, and further studies the configuration and spatial distribution characteristics of various sedimentary systems.

[0125] Step 3: Applying the results of Step 2, interpret the statistical distribution range of physical properties through well logging and classify them, then delineate the distribution range of physical property strips on the plan view. Based on the distribution of these strips, design a matching diamond-shaped well network, including: the long axis of the well network is along the river channel, and the short axis is perpendicular to the river channel. In the inter-channel area, the long axis of the well network is slightly shorter, resulting in relatively uniform injection and production. In the initial stage of production, intermittent injection and production are implemented near the gas cap area. After achieving the recovery rate, a row of oil wells near the gas cap is converted to injection, forming a row injection and production pattern, establishing a water injection barrier, and cutting off the miscibility channel between the oil and gas areas.

[0126] Step 4: Based on the results of Step 3, adjust the injection and production parameters to maintain a stable seepage balance at the oil-gas interface. This includes: analyzing the changes in the oil-gas interface and the three-phase displacement law of oil, gas, and water, combining field production and testing results, and establishing a multiphase seepage theoretical equilibrium equation. Based on this, design the distance between the perforated well section and the gas cap, the optimal oil production rate without gas channeling, and a reasonable injection rate. Four scenarios are involved in prediction, and the values ​​are input into simulation software to select the optimal scenario.

[0127] This method was initially implemented in the reservoir and achieved practical results in maintaining the oil-gas interface and utilizing remaining oil. Analysis and testing of production wells near the gas cap, using the results of 75 well tests as the basis for verification, showed that the gas content of individual wells matched theoretical calculations, all of which were below the theoretical values. Daily oil production was reasonably controlled, formation pressure was well maintained, and logging interpretation from new drilling wells confirmed that the oil-gas interface remained stable.

[0128] In one feasible implementation, the ratio of the major axis distance to the minor axis distance in the first rhomboid well pattern is greater than or equal to 1.5.

[0129] By ensuring that the ratio of the major axis distance to the minor axis distance is greater than or equal to 1.5, the injection wells in the well network can cut off the mixing channel between the oil and gas areas, suppress gas cap expansion upwards to prevent gas channeling, and provide water drive energy downwards to improve the development effect of gas cap reservoirs.

[0130] In one feasible implementation, the distance between the minor axes in the first rhomboid well pattern is 300m to 400m.

[0131] By using a short axis distance of 300m to 400m in the first diamond-shaped well network, it is ensured that the injection wells in the network can cut off the mixing channel between the oil and gas areas, suppress gas cap expansion upwards to prevent gas channeling, and provide water drive energy downwards to improve the development effect of gas cap reservoirs.

[0132] According to a second aspect of the embodiments of this application, a gas cap reservoir development system is provided, comprising:

[0133] The confirmation unit is used to determine the sedimentary microfacies information of the target interval based on well logging information and seismic data.

[0134] The division unit is used to divide the target layer into physical property bands based on sedimentary microfacies information, and to obtain high-quality physical property bands and low-quality physical property bands.

[0135] The drawing unit is used to set the first diamond-shaped well pattern in the high-quality physical property strips within the target layer;

[0136] The drawing unit is also used to set a second diamond-shaped well pattern in the poor physical property strips within the target layer;

[0137] The minor axis length of the first rhomboid well pattern is smaller than that of the second rhomboid well pattern.

[0138] The gas cap reservoir development system provided in this application first uses well logging information and seismic data to drive the sedimentary microfacies information of the target layer. Then, based on the sedimentary microfacies information, the physical properties of the target layer are divided, identifying high-quality and low-quality property bands. A first diamond-shaped well pattern is set up for the areas corresponding to the high-quality property bands within the target layer, and a second diamond-shaped well pattern is set up for the areas corresponding to the low-quality property bands. This setup allows for oil harvesting in the gas cap reservoir based on the first and second diamond-shaped well patterns. The well pattern is matched to the sedimentary microfacies information of the target layer, enabling the injection wells in the well pattern to cut off the miscibility channel between the oil and gas zones, suppressing gas cap expansion upwards and preventing gas channeling; and providing water drive energy downwards, thus improving the development effect of the gas cap reservoir.

[0139] It is understandable that sedimentary microfacies information can be determined vertically in the target layer by setting well logging information, and sedimentary microfacies information can be determined horizontally by seismic data. The sedimentary microfacies information determined by well logging information and seismic data is more accurate.

[0140] It is understandable that based on sedimentary microfacies information, physical properties can be divided into multiple target layers, thereby distinguishing between high-quality and low-quality physical property bands. It is also understandable that high-quality physical property bands may include multiple layers of physical property bands, with different physical properties between these layers; similarly, low-quality physical property bands may also include multiple layers of physical property bands, with different physical properties between these layers; and it is also understandable that the physical properties of high-quality physical property bands are superior to those of low-quality physical property bands.

[0141] It is understandable that the endpoints of the first diamond-shaped well pattern are the production wells, and the wells in the middle area of ​​the first diamond-shaped well pattern are the injection wells.

[0142] It is understandable that the endpoints of the second diamond-shaped well pattern are the production wells, and the wells in the middle area of ​​the second diamond-shaped well pattern are the injection wells.

[0143] The minor axis length of the first diamond-shaped well pattern is shorter than that of the second diamond-shaped well pattern. The minor axis length of the first diamond-shaped well pattern located in the high-quality physical property zone is shorter than that of the second diamond-shaped well pattern located in the low-quality physical property zone. This is more conducive to the injection well cutting off the miscible channel between the oil and gas zones, suppressing gas cap expansion upwards and preventing gas channeling; and providing water drive energy downwards, thus improving the development effect of gas cap reservoirs.

[0144] In this invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; the term "multiple" refers to two or more unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0145] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or unit referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0146] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0147] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for developing gas cap reservoirs, characterized in that, include: Based on well logging information and seismic data, the sedimentary microfacies information of the target interval was determined; Based on the sedimentary microfacies information, the target layer is divided into physical property bands to obtain high-quality and low-quality physical property bands. A first diamond-shaped well pattern is set in the high-quality physical property strips within the target layer; A second diamond-shaped well pattern is set in the inferior physical property strips within the target layer; Wherein, the minor axis length of the first rhombic well pattern is smaller than the minor axis length of the second rhombic well pattern; Identify oil and gas zones within the target stratigraphic unit; Displacement fluid is injected into injection wells based on the first and second diamond-shaped well patterns; In the area near the gas cap, intermittent injection and production are implemented. After the recovery rate is achieved, a row of oil wells near the gas cap are converted to injection, forming a pattern of injection and production, establishing a water injection barrier, and cutting off the mixing channel between the oil and gas areas.

2. The gas cap reservoir development method according to claim 1, characterized in that, The step of determining the sedimentary microfacies information of the target interval based on well logging information and seismic data includes: Based on well logging records and logging data, the core sedimentary characteristics of the target formation were determined; Based on the core sedimentary characteristics and regional logging response characteristics, a first correspondence between lithofacies and logging curve characteristics is established. Based on well logging curves and seismic data, a second correspondence between waveform attributes and well logging curve characteristics is established; Based on the first and second correspondences, the depositional microfacies information of the target layer is determined.

3. The gas cap reservoir development method according to claim 2, characterized in that, The step of establishing a first correspondence between lithofacies and logging curve characteristics based on the core sedimentary characteristics and regional logging response characteristics includes: Based on well logging records and logging data, natural gamma, photoelectric absorption cross section index, compensated density and compensated neutron porosity were obtained as the original curves for well logging phase analysis. Based on the original logging facies analysis curve, a first correspondence between lithofacies and logging curve characteristics is established.

4. The gas cap reservoir development method according to claim 3, characterized in that, The step of establishing the first correspondence between lithofacies and well logging curve characteristics based on the original well logging facies analysis curve includes: Among them, S dn This is the first correspondence. To compensate for neutron porosity, ρ c To compensate for density.

5. The gas cap reservoir development method according to claim 4, characterized in that, The step of establishing a second correspondence between waveform attributes and well logging curve characteristics based on well logging curves and seismic data includes: Seismic facies analysis is performed based on the reflection structure, continuity, amplitude, frequency, and geometric shape of wave groups on seismic profiles to obtain seismic analysis data; Based on the aforementioned seismic analysis data and well logging curve characteristics, an initial correspondence is established; The initial correspondence is processed by cluster analysis to obtain the second correspondence between waveform attributes and logging curve characteristics.

6. The gas cap reservoir development method according to claim 5, characterized in that, The step of determining the depositional microfacies information of the target layer based on the first correspondence and the second correspondence includes: The second correspondence in the time domain is converted into a second correspondence in the frequency domain; Seismic signal difference is calculated from the second correspondence in the frequency domain, and combined with the first correspondence to generate a seismic phase map; Based on the seismic facies map, the sedimentary microfacies information of the target layer is determined.

7. The gas cap reservoir development method according to claim 6, characterized in that, The conversion of the second correspondence in the time domain to the second correspondence in the frequency domain is achieved through the following formula: Where a(f) is the interpolation function value, a n is the frequency domain signal; n is the discrete point number; Δf is the frequency domain sampling interval; f is the frequency value at the point to be interpolated; i is the imaginary unit.

8. The gas cap reservoir development method according to claim 1, characterized in that, The step of dividing the target layer into physical property bands based on the sedimentary microfacies information to obtain high-quality and low-quality physical property bands includes: The region corresponding to the river channel in the sedimentary microfacies information is taken as a high-quality physical property strip; The regions in the sedimentary microfacies information that correspond to the channel direction are designated as inferior physical property bands.

9. The gas cap reservoir development method according to claim 8, characterized in that, The major axis of the first rhomboid well network is arranged along the direction of the river channel, and the minor axis of the first rhomboid well network is perpendicular to the direction of the river channel.

10. The gas cap reservoir development method according to claim 1, characterized in that, The steps for extracting oil from the oil and gas reservoir in the oil and gas area through intermittent injection and production using the production wells based on the first and second rhomboid well patterns include: Clearly define the oil and gas boundaries between oil and gas zones and gas zones within the target stratigraphic unit; Production wells in the first and second diamond-shaped well networks with a distance greater than a first threshold from the oil and gas boundary are selected to collect oil from the oil and gas reservoir within the oil and gas zone.

11. The gas cap reservoir development method according to claim 10, characterized in that, After the oil reservoir in the oil and gas zone is harvested, the gas reservoir in the oil and gas zone is harvested through the production well.

12. The gas cap reservoir development method according to claim 10, characterized in that, Also includes: Adjust the injection rate of the injection well and the production rate of the production well to achieve a balance at the oil and gas interface in the oil and gas zone.

13. The gas cap reservoir development method according to claim 12, characterized in that, The step of adjusting the injection rate of the injection well and the production rate of the production well to achieve oil and gas interface balance in the oil and gas zone includes: Based on production and test records, a multiphase flow theoretical equilibrium model was established. Based on the aforementioned multiphase flow theory equilibrium model, the injection and lift parameters are determined.

14. The gas cap reservoir development method according to claim 13, characterized in that, The steps for establishing a multiphase flow theoretical equilibrium model based on production records and test records include: The theoretical equilibrium model of the multiphase seepage is established by the following formula: in, Let be the change in the potential function. γ is the longitudinal displacement change, and γ is the force acting on the flow element point. c The force required to stabilize the unit fluid, where Δγ is the difference in bulk density between oil and gas, k is the permeability, and μ is the viscosity of the oil. Let γ be the potential function, P be the force acting on the element, and γ be the force. g Let Z be the radius of operation, Z be the longitudinal displacement, Q be the limiting oil production, and h be the maximum oil production. e In order to utilize thickness, μ0 represents the degree of perforation opening, and μ0 represents the viscosity of the crude oil under formation conditions.

15. The gas cap reservoir development method according to any one of claims 1, characterized in that, In the first rhomboid well pattern, the ratio of the distance between the major axis and the distance between the minor axis is greater than or equal to 1.

5.

16. The gas cap reservoir development method according to claim 15, characterized in that, The distance between the short axes in the first rhomboid well pattern is 300m to 400m.

17. A gas cap reservoir development system for performing the gas cap reservoir development method as described in any one of claims 1-16, characterized in that, include: The confirmation unit is used to determine the sedimentary microfacies information of the target layer based on well logging information and seismic data. A partitioning unit is used to divide the target layer into physical property bands based on the sedimentary microfacies information, and to obtain high-quality physical property bands and low-quality physical property bands. A drawing unit, the drawing unit being used to set a first diamond-shaped well pattern in the high-quality physical property strips within the target layer; The drawing unit is also used to set a second diamond-shaped well pattern in the inferior physical property strips within the target layer; The minor axis length of the first rhombic well pattern is smaller than that of the second rhombic well pattern.

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