Water intrusion early warning method, system, equipment and medium for fractured low-porosity sandstone gas reservoirs

Abstract

The present invention belongs to the field of oil and natural gas development geology and relates to a water intrusion early warning method for fractured low-porosity sandstone gas reservoirs. The method comprises the following steps: obtaining static geological parameters and dynamic parameters that affect water intrusion in fractured gas reservoirs as evaluation indicators; determining a weight coefficient for each evaluation indicator; normalizing the evaluation indicators of different gas wells to obtain evaluation indicator parameters; calculating the water intrusion risk coefficient for each well in the block based on the evaluation indicator parameters and the weight coefficient of each evaluation indicator, using a constructed mathematical model of water intrusion risk coefficient and evaluation indicators; drawing a water intrusion risk planar distribution map based on the water intrusion risk coefficient of each well in the block to determine the water intrusion risk; calculating the adjacent water advance speed based on the water intrusion risk coefficient; and using a prediction model to predict the future water breakthrough time of the gas well based on the spacing between adjacent wells and the adjacent water advance speed. This method achieves quantitative evaluation of the risk of non-uniform water intrusion in fractures and accurate early warning of the water breakthrough time of the gas well.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and natural gas development geology, and relates to a water intrusion early warning method, system, equipment and medium for fractured low-porosity sandstone gas reservoirs. Background Art

[0002] In recent years, as the exploration and development of shallow and medium-layer natural gas resources in my country has matured, new discoveries have become increasingly difficult. Deep and ultra-deep formations have gradually become a key area of ​​natural gas exploration and development in my country. Important breakthroughs have been made in the ultra-deep formations of the Kuqa Depression in the Tarim Basin, with the discovery of deep and ultra-deep gas fields such as the Dabei, Keshen, and Bozi formations. These gas reservoirs are buried at depths of 6,000 to 8,000 meters and feature high temperatures, ultra-high pressures, a dense matrix, and widespread fractures. The gas-water relationship is extremely complex, and the reservoir type and development difficulty are rare worldwide. These reservoirs exhibit a multi-scale "pore-fracture-fault" structure, with a matrix-permeability difference of up to 5 to 6 orders of magnitude. Formation water easily invades along fractures, forming high-speed channels. The risk of heterogeneous water invasion in gas reservoirs is increasing year by year. After water breakthrough, gas wells experience a rapid decline in production capacity, sometimes even leading to flooding and well closure. Heterogeneous water invasion in fractures severely impacts reservoir development and recovery. To promptly develop technical countermeasures for water control and mitigation and reduce the risk of water intrusion in gas reservoirs, it is necessary to accurately predict water breakthrough times in gas wells and quantitatively assess water intrusion risks. This provides a reliable basis for adjusting development strategies and formulating water control measures. Water intrusion early warning and quantitative assessment have become key technical issues for water intrusion control and efficient development in deep / ultra-deep fractured, low-porosity sandstone gas reservoirs with edge water.

[0003] Through investigation, it is found that the current methods for early identification of water invasion in fractured gas reservoirs mainly include the use of wellhead pressure and production changes, analysis of produced water properties, pressure drop curve identification, unstable well test curve identification, material balance method water invasion identification and gas reservoir numerical simulation. These methods require the gas reservoir to have a long production time and recovery degree. However, they have certain limitations in application to ultra-deep fractured low-porosity sandstone gas reservoirs in the early stage of development. At the same time, they do not take into account the static characteristics of the gas reservoir itself, such as multi-scale media, high temperature, and ultra-high pressure.

[0004] Extensive research has been conducted on fracture water stringing and water coning. It is generally believed that large fractures are the primary pathways for water stringing and bottom water coning. A water cone height and shape model for bottom water reservoirs has been developed. Using this coning model, water invasion dynamics in fractured bottom water reservoirs have been simulated. Sensitivity analyses of various parameters, including matrix permeability, fracture size and distribution, bottomhole interlayers, gas production rate, well opening degree, and water body size, have shown that water channeling along fractures is the primary water invasion characteristic of these reservoirs. Water invasion significantly impacts the production performance of gas wells. In the absence of water invasion, the wells experience no pressure replenishment and exhibit the characteristics of a closed gas reservoir. In the early stages of water invasion, the wells receive energy from the water body, and under stable production conditions, the pressure decreases more slowly than in the absence of water invasion. In the middle and late stages of water invasion, especially when edge and bottom water intrude into the gas well perimeter, gas flow is significantly impeded, leading to a significant increase in the production pressure differential at the same production rate.

[0005] In predicting the time of water breakthrough in gas wells and identifying water invasion stages, Yang Furong et al. mathematically derived a formula for calculating the water tongue breakthrough time in high-yield gas wells with edge water, taking into account factors such as the non-Darcy effect, gas-water mobility ratio, initial irreducible water saturation, residual gas saturation, and the distance from the gas well to the edge water. Li Yong et al. proposed a new method for classifying gas well water invasion stages based on three diagnostic curves drawn from actual gas well production and pressure data. All three diagnostic curves can be used to classify gas well production into three stages: pre-water invasion, initial water invasion, and mid-to-late water invasion. This method, applied to actual field wells, accurately identifies the water invasion stage and determines the water breakthrough sequence in gas wells with water. Luo Ruilan et al. used modern gas well production performance analysis methods to analyze the water invasion dynamics of such reservoirs and wells, thereby establishing a water production early warning model. Based on the changing characteristics of the gas production index, they classified the production of water-producing gas wells into four stages: the well clean-up period, the non-water invasion period, the initial water invasion period, and the water production period. In the early stage of water invasion, the gas production index increases significantly due to energy replenishment, becoming a sign of water invasion warning. Once the water invasion breaks through the bottom of the well, the gas production index will decrease rapidly.

[0006] The above methods only analyze water invasion dynamics in gas reservoirs to classify water invasion stages and provide early warnings. They fail to consider the actual geological characteristics of the reservoir and the structural location of the gas wells. Furthermore, they lack effective quantitative assessment methods for water invasion. Furthermore, due to the difficulty in acquiring dynamic monitoring data for ultra-deep, high-pressure gas reservoirs, accurate predictions of water breakthrough timing for gas wells are impossible. Therefore, new technologies and methods are needed to address these deficiencies in water breakthrough prediction, enabling quantitative assessment of water invasion risk in deep / ultra-deep, fractured, low-porosity sandstone gas reservoirs and accurate early warning of water breakthrough timing. Summary of the Invention

[0007] The purpose of the present invention is to provide a water intrusion early warning method, system, equipment and medium for fractured low-porosity sandstone gas reservoirs, which solves the problem that existing methods cannot accurately predict the water breakthrough time of gas wells.

[0008] The present invention is achieved through the following technical solutions:

[0009] The present invention discloses a water intrusion early warning method for fractured low-porosity sandstone gas reservoirs, comprising the following steps:

[0010] Obtain static geological parameters and dynamic parameters that affect water invasion in fractured gas reservoirs as evaluation indicators;

[0011] Determine the weight coefficient of each evaluation indicator;

[0012] Normalize the evaluation indicators of different gas wells to obtain evaluation indicator parameters;

[0013] Based on the evaluation index parameters and the weight coefficient of each evaluation index, the water intrusion risk coefficient of each single well in the block is calculated using the constructed mathematical model of water intrusion risk coefficient and evaluation index;

[0014] Draw a water invasion risk plane distribution map based on the water invasion risk coefficient of each single well in the block. Based on the water invasion risk coefficient plane distribution map and the actual gas well production situation, determine the water invasion risk;

[0015] Calculate the advancing speed of the adjacent water body based on the water intrusion risk coefficient;

[0016] Based on the spacing between adjacent wells and the advancing speed of the adjacent water body, the constructed prediction model is used to predict the future water breakthrough time of the gas well.

[0017] Furthermore, the static geological parameters include the gas well water avoidance height H, the distance between the gas well and the edge water L, the fracture mode F and the reservoir permeability K;

[0018] Dynamic parameters include gas production rate S.

[0019] Furthermore, there is a positive correlation between reservoir permeability K and water invasion, a negative correlation between the distance L between the gas well and the edge water and the size of the gas well water avoidance height H and water invasion; and a positive correlation between gas production rate S and water invasion.

[0020] Furthermore, the mathematical model of the water intrusion risk coefficient and evaluation index is:

[0021] ω=(aK+bF+cS-dH-eL)×100%;

[0022] Where ω is the water invasion risk coefficient; K is the reservoir permeability; H is the water avoidance height of the gas well; L is the distance between the gas well and the edge water; S is the gas production rate of the gas reservoir in that month; F is the fracture pattern; a, b, c, d, and e are the weight coefficients of the five evaluation indicators, respectively.

[0023] Furthermore, the weight coefficients of the evaluation indicators are determined using the priority diagram method.

[0024] Furthermore, the evaluation indicators of different gas wells are normalized, and the normalization formula is:

[0025]

[0026] L′ x is the normalized evaluation index, L x is the actual value of a certain evaluation index, x=1...........i, i is the number of evaluation indicators.

[0027] Furthermore, the calculation expression of the propulsion speed near the water body is:

[0028] Y=Aω(x) 2 -Bω(x)+C;

[0029] Y is the advancing speed of the adjacent water body, ω is the water intrusion risk coefficient, ω(x) represents the x-th ω value; A, B, and C are coefficients obtained based on historical data fitting.

[0030] The present invention also discloses a water intrusion early warning system for fractured low-porosity sandstone gas reservoirs, comprising:

[0031] Parameter acquisition module, used to obtain static geological parameters and dynamic parameters that affect water invasion in fractured gas reservoirs as evaluation indicators;

[0032] A weight coefficient determination module is used to determine the weight coefficient of each evaluation indicator;

[0033] Evaluation index normalization module, used to normalize the evaluation indexes of different gas wells to obtain evaluation index parameters;

[0034] The water intrusion risk coefficient calculation module is used to calculate the water intrusion risk coefficient of each single well in the block based on the evaluation index parameters and the weight coefficient of each evaluation index, using the established mathematical model of water intrusion risk coefficient and evaluation index;

[0035] The chart drawing module is used to draw a water invasion risk plane distribution chart based on the water invasion risk coefficient of each single well in the block. Based on the water invasion risk plane distribution chart and the actual gas well production situation, the water invasion risk is judged;

[0036] The module for calculating the speed of the water body near the well is used to calculate the speed of the water body near the well based on the water invasion risk coefficient;

[0037] The prediction module is used to predict the future water breakthrough time of the gas well based on the well spacing between adjacent wells and the propulsion speed of the adjacent water body using the constructed prediction model.

[0038] The present invention also discloses a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the water intrusion early warning method for fractured low-porosity sandstone gas reservoirs are implemented.

[0039] The present invention also discloses a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the water intrusion early warning method for fractured low-porosity sandstone gas reservoirs are implemented.

[0040] Compared with the prior art, the present invention has the following beneficial technical effects:

[0041] This invention provides a water intrusion early warning method for fractured, low-porosity sandstone gas reservoirs. This method comprehensively considers both the static geological factors and dynamic development factors associated with water intrusion in deep / ultra-deep fractured, low-porosity sandstone gas reservoirs with edge water. By using a planar distribution chart of the water intrusion risk coefficient and a chart showing the relationship between the water intrusion risk coefficient and the velocity of the adjacent water body, it enables quantitative assessment of the risk of non-uniform water intrusion in fractures and accurate early warning of water breakthrough in gas wells. Application results from a typical field show that the use of water intrusion risk assessment and early warning technology enabled the timely formulation of a production control plan, which, upon implementation, effectively curbed the water breakthrough rate in the gas reservoir. By curbing the water breakthrough rate in the gas reservoir, the field's recovery factor is expected to increase by 0.27%, generating an additional 356 million yuan in economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of a method for evaluating and early warning water invasion in fractured gas reservoirs according to an embodiment of the present invention;

[0043] Figure 2 This is a distribution chart of water intrusion risk coefficients of single wells in an actual block according to an embodiment of the present invention;

[0044] Figure 3 This is a top surface structural diagram of an actual block according to an embodiment of the present invention;

[0045] Figure 4 Graph showing the relationship between the water intrusion risk coefficient of a well and the advancing speed of the adjacent water body according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following is a further detailed description with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0047] The components described and illustrated in the drawings and embodiments of the present invention may be arranged and designed in a variety of different configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. All other embodiments derived by those skilled in the art based on the drawings and embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0048] The present invention discloses a water intrusion early warning method for fractured low-porosity sandstone gas reservoirs, comprising the following steps:

[0049] Obtain static geological parameters and dynamic parameters that affect water invasion in fractured gas reservoirs as evaluation indicators;

[0050] Determine the weight coefficient of each evaluation indicator;

[0051] Normalize the evaluation indicators of different gas wells to obtain evaluation indicator parameters;

[0052] Based on the evaluation index parameters and the weight coefficient of each evaluation index, the water intrusion risk coefficient of each single well in the block is calculated using the constructed mathematical model of water intrusion risk coefficient and evaluation index;

[0053] Draw a water invasion risk plane distribution map based on the water invasion risk coefficient of each single well in the block. Based on the water invasion risk coefficient plane distribution map and the actual gas well production situation, determine the water invasion risk;

[0054] Calculate the advancing speed of the adjacent water body based on the water intrusion risk coefficient;

[0055] Based on the spacing between adjacent wells and the advancing speed of the adjacent water body, the constructed prediction model is used to predict the future water breakthrough time of the gas well.

[0056] The production conditions of the gas reservoir targeted by the present invention are as follows:

[0057] The gas reservoir is deep (>4500m), high temperature (formation temperature>100℃), ultra-high pressure (pressure coefficient>1.2), dense matrix (permeability<0.1mD), multi-scale medium of pores-fractures-faults is developed, the permeability difference reaches 5-6 orders of magnitude, and there is edge water.

[0058] Fractures are high-speed channels for water invasion. During gas reservoir development, edge water invades non-uniformly along fractures and high-permeability strips, causing gas wells at the bottom of the structure to see water prematurely. After seeing water, the production of the gas wells drops rapidly, and the wells may even be flooded and shut down. Fracture water invasion seriously affects the stable production and development effect of the gas reservoir.

[0059] The present invention provides a water intrusion early warning method for fractured low-porosity sandstone gas reservoirs, the process steps of which are as follows:

[0060] ① The first step is to screen five evaluation indicators, including static geological parameters (gas well water avoidance height H, distance from gas well to edge water L, fracture pattern F, and reservoir permeability K) and dynamic parameters (gas production rate S) that affect water invasion in fractured gas reservoirs. The indicators are quantitatively evaluated using the priority diagram method to determine the weights of the effects of gas well water avoidance height H, distance from gas well to edge water L, reservoir permeability K, fracture pattern F, and gas production rate S on water invasion.

[0061] Differences from background technology:

[0062] Comprehensively considering the static and dynamic geological parameters that cause water invasion, the overall effect of static geological parameters on gas well water invasion is that the closer the gas well is to the edge water L, the smaller the gas well water avoidance height H, and the higher the reservoir permeability K, the more likely the gas well is to experience water invasion. In other words, there is a positive correlation between reservoir permeability K and water invasion, while there is a negative correlation between the gas well distance to the edge water L and the gas well water avoidance height H and water invasion. The effect of dynamic parameters on gas well water invasion is that the greater the gas production rate S, the more likely the gas well is to experience water invasion. In other words, there is a positive correlation between gas production rate S and water invasion.

[0063] The scientific principle of the precedence diagram method: It is a mathematical and statistical analysis method that uses matrix diagrams to analyze the importance of various factors (conditions) to a goal (project success or failure, service quality), providing a basis for management decision-making. Let n be the number of comparison objects. The precedence diagram is a checkerboard diagram with a total of n×n spaces. When making pairwise comparisons, 1.0, 0.5, and 0 can be used to represent the degree of importance. "1" represents relative "importance" in pairwise comparisons, while "0" represents relative "unimportance." For self-comparisons, the value "0.5" is assigned to the same numbered square. The weight calculation method is to horizontally add the numbers filled in each square in each row of the checkerboard to obtain the individual indicator score Aw, and then divide each by the total indicator score An to obtain the weight of each indicator.

[0064] The weight coefficients are determined based on the precedence diagram method. Of course, there are other methods such as AHP, factor analysis, and entropy method. Each method has its own advantages and disadvantages and adaptability. In comparison, the precedence diagram method is simple and practical, with simple calculations and easier to understand.

[0065] ② The second step: Introduce comprehensive geological parameters (water intrusion risk coefficient), and establish a mathematical expression of the water intrusion risk coefficient and the five evaluation indicators based on the weights of the five indicators determined by the priority diagram method. The larger the value, the more likely the well area is to be water invaded, and vice versa, the less likely the well area is to be water invaded.

[0066] By integrating geological parameters - water intrusion risk coefficient (ω), the mathematical expression of water intrusion risk coefficient was finally established:

[0067] ω=(aK+bF+cS-dH-eL)×100%

[0068] Where: ω is the water invasion risk coefficient, dimensionless; K is the reservoir permeability, mD; H is the water avoidance height of the gas well (i.e., the height difference between the bottom of the perforation section and the original gas-water interface) in m; L is the distance from the gas well to the edge water, i.e., the plane distance between the gas well and the original gas-water interface in m; S is the gas production rate of the gas reservoir in that month; F is the fracture pattern, dimensionless; a, b, c, d, e are weight coefficients.

[0069] Differences from background technology:

[0070] For the first time, a mathematical expression of the water intrusion risk coefficient and five evaluation indicators was established, realizing the quantitative evaluation of water intrusion risk.

[0071] Scientific principles:

[0072] The determining factors for the rate of heterogeneous water invasion and water penetration in fractured, water-edge gas reservoirs are the reservoir's geological factors (water-avoidance height of the gas well, distance from the gas well to the water edge, fracture pattern, and permeability) and the development system (gas production rate), representing the five evaluation indicators influencing water invasion. Geological factors are internal, while development systems are external. Fracture water invasion is the result of the combined effects of multiple factors.

[0073] ③ Step 3: Normalize the five indicators of different gas wells, use the water invasion risk coefficient formula to calculate the water invasion risk coefficient of each well in the block, and draw a water invasion risk plane distribution map; use the well spacing and water breakthrough time of individual wells to calculate the advancement speed of individual wells near the water body.

[0074] Different from the prior art: Based on the water invasion risk coefficient formula and five gas well evaluation indicators, this method quantitatively calculates the water invasion risk coefficients of different gas wells, thereby obtaining the water invasion risk coefficients of gas wells on a plane and plotting a planar distribution map of the water invasion risk coefficients. The water invasion risk assessment map generated by this invention can identify water invasion risk locations in gas reservoirs and provide guidance for water invasion prevention.

[0075] Scientific principle: Same as above.

[0076] ④ Step 4: Establish a relationship between the water intrusion risk coefficient and the advancing speed of the adjacent water body, form a chart, and use this relationship to adjust the gas production speed and control the water intrusion speed.

[0077] The calculation expression of the propulsion speed near the water body is:

[0078] Y=Aω(x) 2 -Bω(x)+C.

[0079] Y is the advancing speed of the adjacent water body, ω is the water intrusion risk coefficient, ω(x) represents the x-th ω value, and A, B, and C are coefficients obtained based on historical data fitting.

[0080] Differences from background technology:

[0081] The correlation formula between the water invasion risk coefficient and the advancing speed of the adjacent water body can be obtained. Then, the water breakthrough time of the gas well can be predicted according to the advancing speed of the adjacent water body and the well spacing of adjacent wells. Therefore, the water invasion speed can be controlled by adjusting the gas production rate. By combining the actual block water invasion data with theoretical research, targeted countermeasures for delaying water invasion are proposed, providing technical support for water invasion early warning and development adjustment of fractured gas reservoirs.

[0082] Scientific principles:

[0083] The water invasion risk coefficient and the velocity of the adjacent water body are key parameters for water breakthrough in gas wells. The greater the water invasion risk coefficient, the more likely the well area is to experience water invasion. Combined with the velocity of the adjacent water body, accurate early warning of water breakthrough can be achieved.

[0084] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0085] A fractured gas reservoir is characterized by deep burial depth, high pressure, dense matrix, and well-developed fractures and edge water. Production began in 2013, and a preliminary development plan was completed. In 2015, the annual gas production capacity reached 3.5 billion cubic meters, with 34 production wells deployed. After 2016, water began to appear in gas wells at lower locations, resulting in a production capacity drop of over 50%. The gas field is characterized by well-developed fractures and cracks, and good reservoir connectivity. By the end of 2017, 12 wells had seen water, and the water-gas ratio was growing rapidly and varying widely (2 to 200 m3 / s). 3 / 10 4 m 3 ), the water invasion situation is serious, and the water breakthrough prediction of other wells has become a key issue facing gas reservoir development. Figure 1 As shown, the specific implementation of the water intrusion early warning method for fractured gas reservoirs of the present invention includes:

[0086] Step S101, screening five evaluation indicators that affect water invasion: ① gas well water avoidance height (H); ② distance between gas well and edge water (L); ③ reservoir permeability (K); ④ fracture mode (F); ⑤ gas production rate (S).

[0087] Step S102: The fault pattern of the block is a fracture network pattern. The index weights are determined using the priority graph method and listed in a checkerboard arrangement table (see Table 1). The weight coefficients corresponding to the five evaluation indicators can be obtained.

[0088] Table 1 Checkerboard arrangement table of indicator weights determined by the priority diagram method

[0089]

[0090]

[0091] Step S103: Based on the weights of each indicator, establish a water intrusion risk coefficient formula:

[0092] ω=(0.04K+0.28F+0.36S-0.16H-0.16L)×100%.

[0093] Step S104: The five evaluation indicators of the 14 wells in the block are calculated according to the formula Normalization processing was performed and the water invasion risk coefficient formula was used to calculate the water invasion risk coefficient of each single well and list it in the data table (see Table 2).

[0094] Step S105: Figure 2 As shown in the figure, a water invasion risk coefficient chart of the block is drawn. The larger the water invasion risk coefficient is, the more likely the well area is to be flooded. Conversely, the less likely the well area is to be flooded.

[0095] Step S106: The single well spacing can be obtained according to the well location coordinates. Figure 3 ) and water breakthrough time, calculate the advancing speed of a single well near the water body (see Table 3).

[0096] Step S107: Analyze and fit the relationship between the water intrusion risk coefficient and the advancing speed of the adjacent water body (see Table 4), and establish the relationship between the two parameters Y = 11454 ω (x) 2 - 470.42ω(x)+12.759(see Figure 4 ).

[0097] Step S108: using the relationship between the water invasion risk coefficient and the advancing speed of the adjacent water body, predict the time when the gas well will see water.

[0098] As shown in Table 2, taking Well A17 as an example, by substituting its relevant parameters, we can obtain the water invasion coefficient ω=(0.04K+0.28F+0.36S-0.16H-0.16L)×100%=

[0099] (0.04*0.0714+0.28*0.203+0.36*0.106-0.16*0.083-0.16*0.09)×100%=0.071, then substitute ω into the formula Y=11454ω(x) 2 -470.42ω(x) +12.759 = 25 (m / day). As shown in Table 4, the propulsion speed Y of the adjacent water body can be calculated based on the water intrusion risk coefficient ω.

[0100] Well A17 is 1380.58 meters away from its neighboring water-breaking well, Well A20. Therefore, it is estimated that Well A17 will break water 55 days after Well A20 breaks water, 1380.58 / 25 days later. The actual water breakthrough times, as shown in Table 3, show that Well A20 broke water on January 1, 2016, and Well A17 on March 2, 2016, a time interval of 61 days. This represents a 10% error, indicating a relatively accurate prediction.

[0101] In step S109, through calculation and analysis, production in this block was controlled, reducing it from 4 million cubic meters per day to 2 million cubic meters per day. This extended the period of water-bearing production at wells A14 and A18 in the high-lying areas, as well as wells A27 and A28 in the eastern region. By curbing the water breakthrough rate in the gas reservoir, it is expected that the cumulative gas production will increase by 422 million cubic meters, improve the recovery factor of the block by 0.27%, and generate an additional economic benefit of 356 million yuan (see Table 5).

[0102] Table 2 Calculation table of single well water invasion risk coefficient

[0103]

[0104] Table 3 Calculation table of propulsion speed near water body

[0105]

[0106]

[0107] Table 4 Correspondence between water intrusion risk coefficient ω and the advancing speed Y of the adjacent water body

[0108] ω Y 0.006 12 0.071 25 0.010 8 0.024 6 0.033 11 0.018 6 0.007 11 0.044 16

[0109] Table 5 Economic benefit evaluation of curbing the increase in water breakthrough rate of gas reservoirs by controlling production in blocks

[0110]

[0111] The present invention also discloses a water intrusion early warning system for fractured low-porosity sandstone gas reservoirs, comprising:

[0112] Parameter acquisition module, used to obtain static geological parameters and dynamic parameters that affect water invasion in fractured gas reservoirs as evaluation indicators;

[0113] A weight coefficient determination module is used to determine the weight coefficient of each evaluation indicator;

[0114] Evaluation index normalization module, used to normalize the evaluation indexes of different gas wells to obtain evaluation index parameters;

[0115] The water intrusion risk coefficient calculation module is used to calculate the water intrusion risk coefficient of each single well in the block based on the evaluation index parameters and the weight coefficient of each evaluation index, using the established mathematical model of water intrusion risk coefficient and evaluation index;

[0116] The chart drawing module is used to draw a water invasion risk plane distribution chart based on the water invasion risk coefficient of each single well in the block. Based on the water invasion risk plane distribution chart and the actual gas well production situation, the water invasion risk is judged;

[0117] The module for calculating the speed of the water body near the well is used to calculate the speed of the water body near the well based on the water invasion risk coefficient;

[0118] The prediction module is used to predict the future water breakthrough time of the gas well based on the well spacing between adjacent wells and the propulsion speed of the adjacent water body using the constructed prediction model.

[0119] The present invention also discloses a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the water intrusion early warning method for fractured, low-porosity sandstone gas reservoirs are implemented. The memory may include internal memory, such as a high-speed random access memory, and may also include non-volatile memory, such as at least one disk drive. The processor, network interface, and memory are interconnected via an internal bus, which may be an industrial standard architecture bus, a peripheral component interconnect standard bus, an extended industrial standard architecture bus, or the like. The bus may be classified as an address bus, a data bus, a control bus, or the like. The memory is used to store programs. Specifically, the programs may include program code, which includes computer operating instructions. The memory may include both internal memory and non-volatile memory, and provides instructions and data to the processor.

[0120] The present invention also discloses a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the steps of the water intrusion early warning method for fractured low-porosity sandstone gas reservoirs. Specifically, the computer-readable storage medium includes, but is not limited to, volatile memory and / or non-volatile memory. The volatile memory may include random access memory (RAM) and / or cache memory. The non-volatile memory may include read-only memory (ROM), a hard disk, a flash memory, an optical disk, a magnetic disk, etc.

[0121] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A water intrusion early warning method for fractured low-porosity sandstone gas reservoirs, characterized by: The following processes are included: Obtain static geological parameters and dynamic parameters that affect water invasion in fractured gas reservoirs as evaluation indicators; Determine the weight coefficient of each evaluation indicator; Normalize the evaluation indicators of different gas wells to obtain evaluation indicator parameters; Based on the evaluation index parameters and the weight coefficient of each evaluation index, the water intrusion risk coefficient of each single well in the block is calculated using the constructed mathematical model of water intrusion risk coefficient and evaluation index; Draw a water invasion risk plane distribution map based on the water invasion risk coefficient of each single well in the block. Based on the water invasion risk coefficient plane distribution map and the actual gas well production situation, determine the water invasion risk; Calculate the advancing speed of the adjacent water body based on the water intrusion risk coefficient; Based on the spacing between adjacent wells and the advancing speed of the adjacent water body, the constructed prediction model is used to predict the future water breakthrough time of the gas well.

2. The water intrusion early warning method for fractured low-porosity sandstone gas reservoirs according to claim 1, characterized in that: The static geological parameters include the gas well water avoidance height H, the distance between the gas well and the edge water L, the fracture mode F and the reservoir permeability K; Dynamic parameters include gas production rate S.

3. The water intrusion early warning method for fractured low-porosity sandstone gas reservoirs according to claim 2, characterized in that: There is a positive correlation between reservoir permeability K and water invasion, a negative correlation between the distance L between the gas well and the edge water and the size of the gas well water avoidance height H and water invasion; there is a positive correlation between gas production rate S and water invasion.

4. The water intrusion early warning method for fractured low-porosity sandstone gas reservoirs according to claim 2, characterized in that: The mathematical model of the water intrusion risk coefficient and evaluation index is: ω=(aK+bF+cS-dH-eL)×100%; Where ω is the water invasion risk coefficient; K is the reservoir permeability; H is the water avoidance height of the gas well; L is the distance between the gas well and the edge water; S is the gas production rate of the gas reservoir in that month; F is the fracture pattern; a, b, c, d, and e are the weight coefficients of the five evaluation indicators, respectively.

5. The water intrusion early warning method for fractured low-porosity sandstone gas reservoirs according to claim 3, characterized in that: The weight coefficients of the evaluation indicators are determined using the priority diagram method.

6. The water intrusion early warning method for fractured low-porosity sandstone gas reservoirs according to claim 1, characterized in that: The evaluation indicators of different gas wells are normalized, and the normalization formula is: L′ x is the normalized evaluation index, L x is the actual value of a certain evaluation index, x=1...........i, i is the number of evaluation indicators.

7. The water intrusion early warning method for fractured low-porosity sandstone gas reservoirs according to claim 1, characterized in that: The calculation expression of the propulsion speed near the water body is: Y=Aω(x) 2 -Bω(x)+C; Y is the advancing speed of the adjacent water body, ω is the water intrusion risk coefficient, ω(x) represents the x-th ω value; A, B, and C are coefficients obtained based on historical data fitting.

8. A water intrusion early warning system for fractured low-porosity sandstone gas reservoirs, characterized by: include: Parameter acquisition module, used to obtain static geological parameters and dynamic parameters that affect water invasion in fractured gas reservoirs as evaluation indicators; A weight coefficient determination module is used to determine the weight coefficient of each evaluation indicator; Evaluation index normalization module, used to normalize the evaluation indexes of different gas wells to obtain evaluation index parameters; The water intrusion risk coefficient calculation module is used to calculate the water intrusion risk coefficient of each single well in the block based on the evaluation index parameters and the weight coefficient of each evaluation index, using the established mathematical model of water intrusion risk coefficient and evaluation index; The chart drawing module is used to draw a water invasion risk plane distribution chart based on the water invasion risk coefficient of each single well in the block. Based on the water invasion risk plane distribution chart and the actual gas well production situation, the water invasion risk is judged; The module for calculating the speed of the water body near the well is used to calculate the speed of the water body near the well based on the water invasion risk coefficient; The prediction module is used to predict the future water breakthrough time of the gas well based on the well spacing between adjacent wells and the propulsion speed of the adjacent water body using the constructed prediction model.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the water intrusion early warning method for fractured low-porosity sandstone gas reservoirs as claimed in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the water intrusion early warning method for fractured low-porosity sandstone gas reservoirs according to any one of claims 1 to 7 are implemented.

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