Shale gas layered development feasibility evaluation method
By precisely describing the characteristics of small layers and simulating the extension of fracture networks, combined with economic evaluation and stress difference analysis, the problem of insufficient reserve utilization in shale gas development was solved, efficient stratified development of shale gas was achieved, and the recovery rate was improved.
Patent Information
- Application Number
- CN202410324788.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-21
- Publication Date
- 2025-09-23
AI Technical Summary
In domestic shale gas development, the recovery rate after the implementation of the primary well network is low, the reserves are not fully utilized, the remaining reserves are large, and there is a lack of feasibility evaluation methods for stratified development, resulting in the failure to fully utilize resources.
By carefully describing the characteristics of small layers, simulating the extension of the fracture network, evaluating the reserve utilization status, combining economic evaluation and stress difference analysis, the feasibility of stratified development is determined and the fracturing parameters are optimized.
It improves the utilization rate and recovery rate of shale gas reserves, realizes efficient development of gas fields, and provides guidance and adjustment reference for stratified development.
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Figure CN120688200A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of shale gas development, and in particular to a feasibility evaluation method for shale gas layered development. Background Art
[0002] my country boasts abundant shale gas resources, with recoverable reserves of approximately 25 trillion cubic meters, representing enormous development potential. However, due to differences in geological conditions, development technologies, and policies, there is no successful experience to draw upon for domestic shale gas development. Currently, recovery rates after primary well patterns are generally low (7.3-12.6%), resulting in low recovery rates, insufficient reserve utilization, and significant remaining reserves.
[0003] However, after the implementation of a primary well pattern, the feasibility assessment of further stratified development is a key issue to be addressed in implementing stratified development adjustments. Key issues to be addressed in stratified development feasibility assessment include the resource base, production status, remaining gas distribution, and whether the remaining resources can be economically developed within the primary well pattern's vertical strata, as well as the impact of interlayer stress differences on the longitudinal expansion of the fracture network. The feasibility assessment method for shale gas stratified development is fundamental to guiding shale gas development adjustments to increase the production of remaining resources. It is crucial for guiding stratum selection for development adjustments, optimizing fracturing parameters, improving gas field reserve production and recovery rates, and achieving efficient gas field development. Summary of the Invention
[0004] This application provides a feasibility evaluation method for shale gas layered development, which aims to solve the problems of insufficient shale gas reserves and low development efficiency after the implementation of a well pattern.
[0005] The technical solution of the present application is: a method for evaluating the feasibility of shale gas stratified development, characterized by comprising the following steps:
[0006] S1: Conduct detailed description of each sub-layer in the target layer of the work area, further divide each sub-layer vertically, calculate the reserve abundance of each layer, evaluate the reservoir type and whether there is a geological basis for stratified development;
[0007] S2. Conducting a post-fracture network simulation of a single well after the implementation of the primary well pattern based on the microseismic monitoring results of the gas wells in the work area and the changes in the fracturing operation parameters, confirming the extension of the vertical fracture height and clarifying the vertical stimulation scope of the gas wells in the work area after the implementation of the primary well pattern;
[0008] S3, based on the production status of the gas wells in the work area, using numerical simulation software to evaluate the reserve production status of each layer after the implementation of the primary well pattern, determine the distribution of remaining gas in each layer, and calculate the remaining resources in each layer;
[0009] S4. Based on the remaining resources of each sub-layer and the economic evaluation results of the corresponding drilling, gas test and production investment, evaluate whether the corresponding layer resources can meet the requirements for economic and effective development during stratified development. Only when the resources of the divided layer exceed the economic development requirements can stratified development be carried out;
[0010] S5. On the basis of resource compliance, analyze the impact of longitudinal stress and interlayer stress difference on fracture height expansion to further implement the feasibility of layered development.
[0011] According to the above technical solution, in step S1, the detailed description of the sub-layer includes geochemical characteristics, physical characteristics, gas-bearing characteristics, brittle characteristics, etc., and the above description contents are all obtained through well logging interpretation.
[0012] According to the above technical solution, in step S1, the reserve abundance is obtained by dividing the geological reserves calculated by the volumetric method and the volumetric method by the area.
[0013] According to the above technical solution, in step S2, the monitoring statistical data of the gas well fracturing microseismic data include the length, width, height and orientation of the fracturing cracks, and the fracturing construction parameters of the gas well include the fracturing stage, number of clusters, construction pressure, sand addition amount and liquid addition amount.
[0014] According to the above technical solution, in step S2, the fracture network simulation of a single well after fracturing is performed by using the fracture network simulation module of the geological modeling software in combination with the fracturing operation parameters and the microseismic monitoring parameters.
[0015] According to the above technical solution, in step S3, the reserve production status of the layer should include the calculation of the stress maintenance level, pressure maintenance level, produced reserves and remaining resources of the layer.
[0016] According to the above technical solution, in step S3, the remaining resources of each sub-layer are calculated based on the pressure drop level and the original reserve abundance to determine the remaining reserve abundance.
[0017] According to the above technical solution, in step S4, the resource volume of the stratified development is estimated as the economic limit recoverable reserves according to the single well drilling investment assessment, and the limit of the resource volume of the corresponding stratified system under the current gas field recovery conditions is calculated in combination with the well control area. Only when the resource volume of the divided stratified system is greater than the economic development requirements can stratified development be carried out.
[0018] According to the above technical solution, in step S5, the influence of the longitudinal stress magnitude and the interlaminar stress difference on the fracture height expansion is that when the interlaminar stress difference is large, the longitudinal fracture network is difficult to break through the high stress interface and is easy to expand to the low stress layer system, thereby further realizing the feasibility of the layer system combination division.
[0019] According to the above technical solution, in step S5, if the stress difference is large and the fractures are difficult to extend vertically, the current sub-layer division can support stratified development; if the stress difference is not large and the fracture network can easily extend vertically to other layers, the sub-layer division can be further optimized to achieve the purpose of fully utilizing the vertical reservoir.
[0020] Beneficial effects of this application:
[0021] This application provides a feasibility evaluation method for shale gas layered development, which implements the resource basis of the subdivided layers and the reserve utilization status after the implementation of a well network, clarifies the distribution of remaining resources in the subdivided layers, the impact of longitudinal stress differences on layered development, and whether layered development can meet the requirements of economic benefits. It is the basis for guiding the adjustment of shale gas development to improve the utilization of remaining resources. This method can effectively guide the development and adjustment of layer selection, optimize fracturing parameters, improve the reserve utilization rate and recovery rate of gas fields, achieve efficient development of gas fields, and provide a reference for the layered development adjustment of other shale blocks. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the technical solutions of the implementation methods of the present application, the following is a brief introduction to the drawings required for use in the implementation methods. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.
[0023] Figure 1 A schematic diagram of the hierarchical division of work areas provided in an embodiment of the present application.
[0024] Figure 2 A schematic diagram of the relationship between single well investment and recoverable reserves provided in the embodiments of this application.
[0025] Figure 3 A schematic diagram of the relationship between different reserve abundances and recoverable reserves provided in the embodiments of this application.
[0026] Figure 4 This is a chart showing the correlation between gas well recovery rate, well control area and stratified reserve abundance of the test well group in the work area provided in the embodiment of the present application. DETAILED DESCRIPTION
[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.
[0028] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without making any creative efforts shall fall within the scope of protection of the present application.
[0029] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.
[0030] In the description of this application, it should be noted that the terms "upper" and "lower" etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the invented product is usually placed when in use. These are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this application.
[0031] In addition, in this application, unless otherwise expressly specified or limited, the phrase "a first feature is above or below a second feature" may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, the phrases "above, above, and above the second feature" may include the first feature being directly above and obliquely above the second feature, or simply indicate that the first feature is higher in level than the second feature. The phrases "below, below, and below the second feature" may include the first feature being directly below and obliquely below the second feature, or simply indicate that the first feature is lower in level than the second feature.
[0032] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.
[0033] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.
[0034] Example:
[0035] Please refer to Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 The present invention provides a method for evaluating the feasibility of shale gas layered development, including the following steps:
[0036] S1, such as Figure 1 As shown in the figure, a detailed description of each sub-layer in the target layer of the work area is carried out, and the differences in geochemical characteristics, physical properties, gas-bearing characteristics, brittle characteristics, etc. are obtained based on well logging interpretation. The sub-layers are further divided vertically. The geological reserves are calculated based on the volume method (free gas) and volume method (adsorbed gas) combined with the thickness of each sub-layer, and then divided by the area to obtain the layered reserve abundance (resource abundance). The reservoir type and whether there is a geological basis for layered development are evaluated.
[0037] The total shale gas resources are the sum of the geological resources of free gas, adsorbed gas and dissolved gas. Shale gas reserves = adsorbed gas reserves + free gas reserves, that is: G z =G x +G y
[0038] Adsorbed gas geological reserves G x =0.01A g hρ y C x
[0039] Free gas geological reserves G y =0.01A g hФS gi / B gi G x : Geological reserves of adsorbed gas, 10 8 m 3 ;
[0040] G y : Free gas geological reserves, 10 8 m 3 ;
[0041] A g : Gas-bearing area, km 2 ;
[0042] h: effective thickness of the studied layer, m;
[0043] C x : adsorbed gas content, m 3 / t;
[0044] Ф: effective porosity, f;
[0045] S gi : gas saturation, f;
[0046] B gi: original volume coefficient of natural gas;
[0047] G z :Total geological reserves of shale gas10 8 m 3 ;
[0048] ρ y : Shale mass density, t / m 3 .
[0049] S2. Conducting a post-fracture network simulation of a single well after the implementation of the primary well pattern based on the microseismic monitoring results of the gas wells in the work area and the changes in the fracturing operation parameters, confirming the extension of the vertical fracture height and clarifying the vertical stimulation scope of the gas wells in the work area after the implementation of the primary well pattern;
[0050] S3, based on the production status of the gas wells in the work area, using numerical simulation software to evaluate the reserve production status of each layer after the implementation of the primary well pattern, determine the distribution of remaining gas in each layer, and calculate the remaining resources of each layer, wherein the remaining resources are calculated based on the pressure drawdown level and the original reserve abundance;
[0051] S4, based on the remaining resources of each sub-layer, combined with the economic evaluation and estimation results corresponding to the investment in drilling, gas testing and production, the economic limit recoverable reserves (internal rate of return 8%) can be determined, such as Figure 2 As shown. Under the condition of a certain well control area of the gas well, according to the recoverable reserves that can be achieved under certain recovery rate conditions with different reserve abundances, the reserve abundance required to reach the economic limit of recovery is clearly defined, as shown in Figure 3 When the well control area of the gas well is different and the economic limit recoverable reserves are certain, the reserve abundance chart corresponding to different recovery rate conditions can be compiled, as shown in Figure 4 Based on this, we evaluate whether the corresponding stratum resources can meet the requirements of economic and effective development during stratified development. Only when the resources of the divided stratum exceed the requirements of economic development can stratified development be carried out.
[0052] S5. On the basis of resource compliance, the effects of longitudinal stress magnitude and interlayer stress differences on fracture height expansion are analyzed. If there are stress barriers in the vertical direction and the stress difference is large (greater than 3.5 MPa), the fractures are difficult to extend vertically. In this case, the current sub-layer division can support stratified development. If the stress difference is not large, the fracture network can easily extend vertically to other layers. In this case, the sub-layer division can be further optimized to achieve the goal of fully utilizing the vertical reservoir.
[0053] It should be noted that, in step S1, the detailed description of the sub-layer includes geochemical characteristics, physical characteristics, gas-bearing characteristics, brittle characteristics, etc.
[0054] It should be noted that in step S2, the gas well fracturing microseismic monitoring statistics include the length, width, height, and orientation of the fractures. The gas well fracturing operation parameters include the fracturing stage, number of clusters, operation pressure, sand injection rate, and fluid injection rate. Post-fracturing fracture network simulation for a single well is performed using the fracture network simulation module of the PETREL geological modeling software, combining fracturing operation parameters with microseismic monitoring parameters.
[0055] Furthermore, in step S3, the numerical simulation software can fit the gas well's production profile, predict its productivity, evaluate the well's current pressure maintenance level, and clarify the well's surrounding reserve utilization. The layered reserve utilization status should include calculations of the layered stress maintenance level, pressure maintenance level, utilized reserves, and remaining resources. The remaining resources in each sublayer are calculated based on the pressure drawdown level and the original reserve abundance.
[0056] It should be noted that in step S4, the resource estimate for stratified development is calculated based on the economically recoverable reserves based on the single-well drilling investment assessment, combined with the well-controlled area to calculate the resource limits for the corresponding stratified system under the current gas field recovery conditions. Stratified development can only be carried out if the resource reserves of the stratified system exceed the economic development requirements.
[0057] Furthermore, in step S5, the influence of the longitudinal stress magnitude and the interlaminar stress difference on the fracture height expansion is that when the interlaminar stress difference is large, the longitudinal fracture network is difficult to break through the high stress interface and is easy to expand to the low stress layer system, thereby further realizing the feasibility of the layer system combination division.
[0058] In summary, this application provides a feasibility evaluation method for shale gas layered development. It establishes the resource base of the subdivided layers and the reserve utilization status after the implementation of a single well pattern. It also clarifies the distribution of remaining resources in the subdivided layers, the impact of longitudinal stress differences on layered development, and whether layered development can meet economic efficiency requirements. This method serves as a basis for guiding shale gas development adjustments to improve the utilization of remaining resources. This method can effectively guide development adjustments, optimize strata, and fracturing parameters, improve gas field reserve utilization and recovery rates, achieve efficient gas field development, and provide a reference for layered development adjustments in other shale blocks.
[0059] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.
Claims
1. A feasibility evaluation method for shale gas stratified development, characterized in that: The following steps are involved: S1: Conduct detailed description of each sub-layer in the target layer of the work area, further divide each sub-layer vertically, calculate the reserve abundance of each layer, evaluate the reservoir type and whether there is a geological basis for stratified development; S2. Conducting a post-fracture network simulation of a single well after the implementation of the primary well pattern based on the microseismic monitoring results of the gas wells in the work area and the changes in the fracturing operation parameters, confirming the extension of the vertical fracture height and clarifying the vertical stimulation scope of the gas wells in the work area after the implementation of the primary well pattern; S3, based on the production status of the gas wells in the work area, using numerical simulation software to evaluate the reserve production status of each layer after the implementation of the primary well pattern, determine the distribution of remaining gas in each layer, and calculate the remaining resources in each layer; S4. Based on the remaining resources of each sub-layer and the economic evaluation results of the corresponding drilling, gas test and production investment, evaluate whether the corresponding layer resources can meet the requirements for economic and effective development during stratified development. Only when the resources of the divided layer exceed the economic development requirements can stratified development be carried out; S5. On the basis of resource compliance, analyze the impact of longitudinal stress and interlayer stress difference on fracture height expansion to further implement the feasibility of layered development.
2. The feasibility evaluation method for shale gas stratified development according to claim 1, characterized in that: In step S1, the detailed description of the sub-layer includes geochemical characteristics, physical characteristics, gas-bearing characteristics, brittle characteristics, etc., and the above description contents are all obtained through well logging interpretation.
3. A shale gas stratified development feasibility evaluation method according to claim 2, characterized in that: In step S1, the reserve abundance is obtained by dividing the geological reserves calculated by the volumetric method and the volumetric method by the area.
4. The feasibility evaluation method for shale gas stratified development according to claim 1, characterized in that: In step S2, the monitoring statistics of the gas well fracturing microseismic data include the length, width, height and orientation of the fracturing cracks, and the fracturing construction parameters of the gas well include the fracturing stage, number of clusters, construction pressure, sand addition amount and liquid addition amount.
5. A shale gas stratified development feasibility evaluation method according to claim 4, characterized in that: In step S2, the post-fracture network simulation of a single well is performed by using the fracture network simulation module of the geological modeling software in combination with the fracturing operation parameters and the microseismic monitoring parameters.
6. The method for evaluating the feasibility of shale gas stratified development according to claim 1, wherein: In step S3, the reserve production status of each layer should include the calculation of the stress maintenance level, pressure maintenance level, produced reserves and remaining resources of each layer.
7. A shale gas stratified development feasibility evaluation method according to claim 6, characterized in that: In step S3, the remaining resources of each sub-layer are calculated based on the pressure drop level and the original reserve abundance to determine the remaining reserve abundance.
8. The feasibility evaluation method for shale gas stratified development according to claim 1, characterized in that: In step S4, the resource volume of the stratified development is estimated as the economic limit recoverable reserves according to the single well drilling investment assessment, and the limit of the resource volume of the corresponding stratified system under the current gas field recovery conditions is calculated in combination with the well control area. Only when the resource volume of the divided stratified system is greater than the economic development requirements can stratified development be carried out.
9. The method for evaluating the feasibility of shale gas stratified development according to claim 1, wherein: In step S5, the influence of the longitudinal stress magnitude and the interlaminar stress difference on the fracture height expansion is that when the interlaminar stress difference is large, the longitudinal fracture network is difficult to break through the high stress interface and is easy to expand to the low stress layer system, thereby further realizing the feasibility of the layer system combination division.
10. A shale gas stratified development feasibility evaluation method according to claim 9, characterized in that: In step S5, if the stress difference is large and the fracture is difficult to extend in the vertical direction, then the current sub-layer division can support layered development; If the stress difference is not large and the fracture network is easy to extend to other layers vertically, the sub-layer division can be further optimized to achieve the goal of fully utilizing the vertical reservoir.