Method and system for improving recovery factor of unconventional reservoirs

Abstract

The present invention discloses a method and system for improving the recovery rate of unconventional reservoirs, belonging to the technical field of oil and gas exploitation. The method includes the following steps: collecting seismic exploration data of the unconventional reservoir area based on seismic exploration technology; constructing a three-dimensional geological model of the unconventional reservoir based on the seismic exploration data; determining the layout positions of injection wells and production wells based on the three-dimensional geological model; and carrying out the exploitation of the unconventional reservoir through CO2 flooding technology based on the injection wells and production wells. The present invention can accelerate the oil and gas exploitation speed and shorten the investment return period by reasonably arranging the well positions in combination with CO2 flooding technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas exploitation, and particularly relates to a method and system for improving the recovery rate of unconventional reservoirs. Background Art

[0002] Unconventional reservoirs such as shale oil, tight oil, oil sands, and coalbed methane have significant differences in their reservoir characteristics compared to conventional reservoirs. Conventional oil and gas exploitation technologies are difficult to effectively exploit these resources. These reservoirs usually have characteristics such as low permeability, porosity, well-developed fractures, and strong reservoir heterogeneity, resulting in difficult oil and gas flow and low recovery rates.

[0003] Traditionally, the exploitation of unconventional reservoirs mainly relies on horizontal drilling technology and hydraulic fracturing technology, but these technologies have limited effects on improving the recovery rate. In recent years, CO 2 flooding technology has received attention due to its dual advantages in improving the recovery rate and achieving underground storage of greenhouse gases. CO 2 flooding technology improves the recovery rate by injecting carbon dioxide into the oil reservoir to reduce the viscosity of crude oil, expand the volume of crude oil, and improve the oil-water mobility ratio.

[0004] However, the successful implementation of CO 2 flooding technology requires an accurate geological model to guide the layout of well positions to ensure that CO 2 can effectively displace crude oil. Currently, there is a lack of a method for quickly arranging well positions, resulting in low exploitation efficiency of unconventional reservoirs. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a method and system for improving the recovery rate of unconventional reservoirs to solve the problems existing in the above prior art.

[0006] To achieve the above object, the present invention provides a method for improving the recovery rate of unconventional reservoirs, including the following steps:

[0007] Collect seismic exploration data of the unconventional reservoir area based on seismic exploration technology;

[0008] Construct a three-dimensional geological model of the unconventional reservoir based on the seismic exploration data;

[0009] Determine the layout positions of injection wells and production wells based on the three-dimensional geological model;

[0010] Carry out the exploitation of the unconventional reservoir by CO 2 flooding technology based on the injection wells and production wells.

[0011] Preferably, the method for collecting seismic exploration data of the unconventional reservoir area includes:

[0012] Collect observation system parameters and construct an initial observation system. The observation system parameters include the exploration survey area range, caprock and reservoir properties, depth of the target layer, and two-way travel time range of seismic waves.

[0013] Iteratively optimize the initial observation parameters of the initial observation system to obtain optimized observation parameters.

[0014] Construct a target observation system based on the optimized observation parameters to obtain seismic data of unconventional reservoirs.

[0015] Preferably, the method for obtaining optimized observation parameters includes:

[0016] Construct a forward model of the observation system based on the observation system and the initial observation parameters, analyze the observation parameters through the forward model, and obtain a forward simulation result.

[0017] Iteratively optimize the initial observation parameters based on the forward simulation result to obtain optimized observation parameters.

[0018] Preferably, the observation system is an integral composed of geophones and a seismic source. The geophones are arranged at intervals of a trace interval, and adjacent seismic source points of the seismic source are excited at intervals of a shot interval. The observation system obtains seismic exploration data of the unconventional reservoir area through the acquisition method of fixing the geophone detection points and moving the seismic source.

[0019] Preferably, the method for constructing a three-dimensional geological model of an unconventional reservoir includes:

[0020] Identify the seismic exploration data to obtain the geological structure.

[0021] Determine the top and bottom boundaries of the formation, fault information, fracture information, and reservoir distribution based on the geological structure.

[0022] Create a three-dimensional grid model, and assign the top and bottom boundaries of the formation, fault information, fracture information, and reservoir distribution to the three-dimensional grid model to obtain a three-dimensional geological model of the unconventional reservoir.

[0023] Preferably, the method for determining the layout positions of injection wells and production wells includes:

[0024] Perform numerical simulation on the three-dimensional geological model, obtain the flow path of the reservoir based on the fault information, fracture information, and reservoir distribution, judge the positions of the injection wells and production wells based on the flow path, and judge the depths of the injection wells and production wells based on the top and bottom boundaries of the formation.

[0025] The present invention also proposes an unconventional reservoir recovery rate improvement system, including:

[0026] A data acquisition module, configured to acquire seismic exploration data of unconventional reservoir areas based on seismic exploration technology;

[0027] A model construction module, connected to the data acquisition module, configured to construct a three-dimensional geological model of an unconventional reservoir based on the seismic exploration data;

[0028] A layout module, connected to the model construction module, configured to determine the layout positions of injection wells and production wells based on the three-dimensional geological model;

[0029] An oil displacement module, connected to the model construction module, configured to perform exploitation of an unconventional reservoir by means of CO 2 oil displacement technology through injection wells and production wells.

[0030] Preferably, the data acquisition module includes an observation system construction unit, an optimization unit, and a data acquisition unit;

[0031] The observation system construction unit is configured to acquire observation system parameters and construct an initial observation system based on the observation system parameters, where the observation system parameters include the surveyed area range of exploration, the properties of the caprock and reservoir, the depth of the target layer, and the two-way travel time range of seismic waves;

[0032] The optimization unit is configured to perform iterative optimization on the initial observation parameters of the initial observation system to obtain optimized observation parameters;

[0033] The data acquisition unit is configured to construct a target observation system based on the optimized observation parameters to obtain seismic data of the unconventional reservoir.

[0034] Preferably, the optimization unit includes a simulation subunit and an iterative optimization subunit;

[0035] The simulation subunit is configured to construct a forward model of the observation system based on the observation system and the initial observation parameters, analyze the observation parameters through the forward model, and obtain a forward simulation result;

[0036] Iteratively optimize the initial observation parameters based on the forward simulation result to obtain optimized observation parameters.

[0037] Preferably, the model construction module includes an identification unit, a feature extraction unit, and a construction unit;

[0038] The identification unit is configured to identify seismic exploration data to obtain a geological structure;

[0039] The feature extraction unit is configured to determine the top and bottom boundaries of the formation, fault information, fracture information, and reservoir distribution based on the geological structure;

[0040] The building block is used to create a three-dimensional grid model, and the top and bottom boundaries of the formation, fault information, fracture information, and reservoir distribution are assigned to the three-dimensional grid model to obtain a three-dimensional geological model of the unconventional reservoir.

[0041] Compared with the prior art, the present invention has the following advantages and technical effects:

[0042] The present invention discloses a method and system for improving the recovery rate of unconventional reservoirs. The method includes the following steps: collecting seismic exploration data of the unconventional reservoir area based on seismic exploration technology; constructing a three-dimensional geological model of the unconventional reservoir based on the seismic exploration data; determining the layout positions of injection wells and production wells based on the three-dimensional geological model; and performing exploitation of the unconventional reservoir through CO 2 flooding technology. The three-dimensional geological model constructed based on the seismic exploration data by the present invention can provide a more accurate underground structure, which helps to better understand the reservoir characteristics and fluid distribution. The positions of the injection wells and production wells determined by the geological model can maximize the flow efficiency and production of oil and gas and reduce ineffective or inefficient drilling. Therefore, through reasonable well placement combined with CO 2 flooding technology, the exploitation speed of oil and gas can be accelerated and the investment return period can be shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments and descriptions thereof of this application are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0044] Figure 1 is a flow chart of the method for improving the recovery rate of the unconventional reservoir according to an embodiment of the present invention;

[0045] Figure 2 is a structural diagram of the system for improving the recovery rate of the unconventional reservoir according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments may be combined with each other. The following will refer to the drawings and combine the embodiments to detail this application.

[0047] It should be noted that the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0048] Embodiment 1

[0049] As Figure 1As shown in the figure, in this embodiment, a method for improving the recovery rate of unconventional reservoirs is provided, including the following steps:

[0050] Collect seismic exploration data of the unconventional reservoir area based on seismic exploration technology;

[0051] Construct a three-dimensional geological model of the unconventional reservoir based on the seismic exploration data;

[0052] Determine the layout positions of injection wells and production wells based on the three-dimensional geological model;

[0053] Based on the injection wells and production wells, carry out the exploitation of the unconventional reservoir through CO 2 oil displacement technology.

[0054] Furthermore, the above method is described in detail as follows:

[0055] S1. Seismic exploration data acquisition: Adopt multi-wave multi-component seismic exploration technology to collect seismic reflection wave data of the unconventional reservoir area, ensuring the sensitivity and resolution of the data in different strata and lithologies.

[0056] S2. Geological structure analysis: Conduct in-depth analysis on the collected seismic exploration data, and use seismic waveform inversion technology to identify the lithology, thickness, continuity and fault development characteristics of the strata.

[0057] S3. Three-dimensional geological model construction: 1. Use geological interpretation software to establish a stratigraphic framework model according to the results of geological structure analysis. 2. Refine the fracture system and pore structure inside the strata through seismic attribute analysis. 3. Combine the principles of geostatistics to perform three-dimensional spatial interpolation and extrapolation on reservoir properties such as porosity and permeability of the strata. 4. Assign fracture information, fault information, lithology distribution and reservoir properties to the three-dimensional grid model to form a high-precision three-dimensional geological model of the unconventional reservoir.

[0058] S4. Optimal well placement: 1. Apply numerical simulation technology to simulate the flow path and oil displacement efficiency of CO 2 in the three-dimensional geological model to determine the optimal positions of injection wells and production wells. 2. Considering the heterogeneity and fracture distribution of the reservoir, optimize the well pattern layout to improve the CO 2 swept volume and oil displacement efficiency.

[0059] S5. CO 2 oil displacement scheme design: 1. According to the three-dimensional geological model and well placement, design the CO 2 injection strategy, including injection rate, injection volume and injection cycle. 2. Adopt the water alternating gas (WAG) injection technology, and control the flow rate of CO 2 by alternating the injection of water and CO 2 to improve the CO 2Sweep efficiency in the reservoir.

[0060] S6, Real-time monitoring and dynamic adjustment: 1. During the CO 2 oil displacement process, production well real-time monitoring technologies such as pressure monitoring, gas-oil ratio monitoring, and isotope monitoring are adopted to grasp the reservoir dynamics in real time. 2. According to the monitoring data, dynamically adjust the CO 2 injection strategy and well layout to optimize the oil displacement effect.

[0061] S7, Comprehensive evaluation of enhanced oil recovery: 1. Combine numerical simulation and actual production data to evaluate the enhanced oil recovery effect of the CO 2 oil displacement plan. 2. Analyze the possible problems during the CO 2 oil displacement process, such as gas channeling, premature breakthrough, and asphaltene precipitation, and propose corresponding solutions.

[0062] Furthermore, the method for collecting seismic exploration data in the unconventional reservoir area includes:

[0063] Collect observation system parameters and construct an initial observation system. The observation system parameters include the surveyed area range for exploration, the caprock and reservoir properties, the depth of the target layer, and the two-way travel time range of seismic waves;

[0064] Iteratively optimize the initial observation parameters of the initial observation system to obtain optimized observation parameters;

[0065] Construct a target observation system based on the optimized observation parameters to obtain seismic data of the unconventional reservoir.

[0066] Furthermore, the method for obtaining optimized observation parameters includes:

[0067] Construct a forward model of the observation system based on the observation system and the initial observation parameters, analyze the observation parameters through the forward model, and obtain forward simulation results;

[0068] Iteratively optimize the initial observation parameters based on the forward simulation results to obtain optimized observation parameters.

[0069] Furthermore, the initial observation parameters include trace interval, maximum offset, and shot interval;

[0070] Among them, the trace interval is the distance between geophones, the maximum offset is the distance between the shot point and the farthest geophone, and the shot interval is the distance between the source points.

[0071] The formula for the trace interval is:

[0072]

[0073] where r is the trace interval, s is the target body size, v is the overlying formation velocity, F h is the maximum aliasing-free frequency, θ is the target body dip angle, F m is the main frequency of the target formation.

[0074] The formula for the maximum source-receiver offset is:

[0075]

[0076] where t is the two-way travel time of the reflected wave, F p is the main frequency of the reflected wave, V rms is the root-mean-square velocity of the formation, A is the accuracy parameter, L is the length of the survey area, and N is the number of receiver channels.

[0077] The formula for the shot interval is: S p = N*r / (2C), where C is the fold.

[0078] Furthermore, the observation system is an integral composed of geophones and a seismic source. The geophones are arranged at intervals of the trace interval, and the adjacent source points of the seismic source are excited at intervals of the shot interval. The observation system obtains the seismic exploration data of the unconventional reservoir area through the acquisition method of fixing the geophone detection points and moving the seismic source.

[0079] Furthermore, the method for constructing the three-dimensional geological model of the unconventional reservoir includes:

[0080] Identifying the seismic exploration data to obtain the geological structure;

[0081] Determining the top and bottom boundaries of the formation, fault information, fracture information, and reservoir distribution based on the geological structure;

[0082] Creating a three-dimensional grid model and assigning the top and bottom boundaries of the formation, fault information, fracture information, and reservoir distribution to the three-dimensional grid model to obtain the three-dimensional geological model of the unconventional reservoir.

[0083] The specific steps include:

[0084] Seismic exploration data processing: First, preprocess the collected seismic exploration data, including denoising, normalization, and time / depth conversion, to improve the data quality and prepare for subsequent analysis.

[0085] Geological structure identification: Using seismic interpretation software, identify the main characteristics of the geological structure through the analysis of the characteristics of seismic waveforms, including but not limited to the continuity of the formation, the presence of faults, folds, and other geological phenomena.

[0086] Stratigraphic top and bottom definition: Through seismic reflection characteristics, accurately determine the top and bottom interfaces of each formation. This step is crucial for understanding the vertical distribution range of the oil reservoir.

[0087] Fault and fracture identification: Apply advanced seismic interpretation techniques, such as three-dimensional seismic attribute analysis, to identify the distribution of faults and fractures. These fractures and faults have a significant impact on the flow path and reservoir characteristics of oil and gas.

[0088] Mapping of oil reservoir distribution: Combine seismic attributes such as amplitude and frequency to map the distribution of oil and gas in the reservoir, including the identification of oil and gas enrichment areas and non-enrichment areas.

[0089] Creation of a three-dimensional grid model: Based on the identified geological structure information, construct a three-dimensional grid model. This model is based on the top and bottom boundaries of the formation, faults, fractures, and oil reservoir distribution, and generates a three-dimensional grid system with geological significance through geostatistical methods and numerical simulation techniques.

[0090] Parameterization of the geological model: In the three-dimensional grid model, assign parameters such as lithology, porosity, and permeability of the formation to each grid cell. These parameters are obtained through interpolation and extrapolation techniques based on seismic interpretation results and geological prior knowledge.

[0091] Model verification and iteration: Verify the accuracy of the model by comparing it with actual drilling, logging, and production data. According to the verification results, iterate and optimize the model to improve its prediction ability.

[0092] Modeling of the fracture system: Pay special attention to the modeling of the fracture system because they play a key role in unconventional oil reservoirs. Use fracture network simulation technology to integrate the distribution, density, and orientation of fractures into the three-dimensional geological model.

[0093] Geological risk assessment: Integrate a geological risk assessment module into the model to assess geological risk factors that may affect oil and gas production, such as fault connectivity, fracture development degree, and formation pressure anomaly.

[0094] Furthermore, the method for determining the layout positions of injection wells and production wells includes:

[0095] Perform numerical simulation on the three-dimensional geological model, obtain the flow path of the oil reservoir based on fault information, fracture information, and oil reservoir distribution, determine the positions of injection wells and production wells based on the flow path, and determine the depths of injection wells and production wells based on the top and bottom boundaries of the formation.

[0096] As Figure 2 shown, this embodiment also provides a system for improving the recovery rate of unconventional oil reservoirs, including:

[0097] A data acquisition module, configured to acquire seismic exploration data of unconventional reservoir areas based on seismic exploration technology;

[0098] A model construction module, connected to the data acquisition module, configured to construct a three-dimensional geological model of an unconventional reservoir based on the seismic exploration data;

[0099] A layout module, connected to the model construction module, configured to determine the layout positions of injection wells and production wells based on the three-dimensional geological model;

[0100] An oil displacement module, connected to the model construction module, configured to perform exploitation of unconventional reservoirs through CO 2 oil displacement technology based on injection wells and production wells.

[0101] Furthermore, the data acquisition module includes an observation system construction unit, an optimization unit, and a data acquisition unit;

[0102] The observation system construction unit is configured to acquire observation system parameters and construct an initial observation system based on the observation system parameters. The observation system parameters include the surveyed area range of exploration, the properties of the caprock and reservoir, the depth of the target layer, and the two-way travel time range of seismic waves;

[0103] The optimization unit is configured to iteratively optimize the initial observation parameters of the initial observation system to obtain optimized observation parameters;

[0104] The data acquisition unit is configured to construct a target observation system based on the optimized observation parameters to obtain seismic data of unconventional reservoirs.

[0105] Furthermore, the optimization unit includes a simulation subunit and an iterative optimization subunit;

[0106] The simulation subunit is configured to construct a forward model of the observation system based on the observation system and the initial observation parameters, analyze the observation parameters through the forward model, and obtain a forward simulation result;

[0107] Iteratively optimize the initial observation parameters based on the forward simulation result to obtain optimized observation parameters.

[0108] Furthermore, the model construction module includes an identification unit, a feature extraction unit, and a construction unit;

[0109] The identification unit is configured to identify seismic exploration data to obtain a geological structure;

[0110] The feature extraction unit is configured to determine the top and bottom boundaries of the formation, fault information, fracture information, and reservoir distribution based on the geological structure;

[0111] The building unit is used to create a three-dimensional grid model, and assign the top and bottom boundaries of the formation, fault information, fracture information, and reservoir distribution to the three-dimensional grid model to obtain a three-dimensional geological model of the unconventional reservoir.

[0112] The above are only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for improving the recovery rate of unconventional oil reservoirs, characterized in that: The following steps are involved: Collect seismic exploration data in unconventional oil reservoir areas based on seismic exploration technology; constructing a three-dimensional geological model of an unconventional oil reservoir based on the seismic exploration data; Determining the locations of injection wells and production wells based on the three-dimensional geological model; Unconventional oil reservoir exploitation based on injection wells and production wells through CO2 flooding technology; The method for collecting seismic exploration data in an unconventional oil reservoir area comprises: Collect observation system parameters and construct an initial observation system, wherein the observation system parameters include the survey area range, cap rock and reservoir properties, target layer depth, and two-way travel time range of seismic waves; Iteratively optimize the initial observation parameters of the initial observation system to obtain optimized observation parameters; Building a target observation system based on the optimized observation parameters to obtain unconventional reservoir seismic data; The method for obtaining the optimized observation parameters comprises: Building a forward model of the observation system based on the observation system and the initial observation parameters, analyzing the observation parameters through the forward model to obtain forward simulation results; Iteratively optimizing the initial observation parameters based on the forward simulation results to obtain optimized observation parameters; The observation system is a whole composed of a detector and a seismic source. The detector is arranged at every channel spacing. Adjacent seismic source points of the seismic source are separated by a shot spacing to excite the seismic source. The observation system obtains seismic exploration data of the unconventional oil reservoir area by fixing the detection points of the detector and moving the seismic source; Methods for determining the locations of injection and production wells include: The three-dimensional geological model is numerically simulated, and the flow path of the reservoir is obtained based on fault information, fracture information and reservoir distribution. The positions of injection wells and production wells are determined based on the flow path, and the depths of injection wells and production wells are determined based on the top and bottom boundaries of the formation.

2. The method for improving the recovery rate of unconventional oil reservoirs according to claim 1, characterized in that: The method for constructing a three-dimensional geological model of an unconventional oil reservoir comprises: Identify seismic exploration data to obtain geological structures; Determine the top and bottom boundaries of the strata, fault information, fracture information and reservoir distribution based on the geological structure; A three-dimensional grid model is created, and the top and bottom boundaries of the strata, fault information, fracture information and reservoir distribution are assigned to the three-dimensional grid model to obtain a three-dimensional geological model of the unconventional oil reservoir.

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