A method for optimizing the well positions of multi-layer three-dimensional horizontal wells in a marine positive rhythm low-permeability edge water sandstone gas reservoir

Abstract

The present invention relates to a method for optimizing the well location of a multi-layer three-dimensional horizontal well in an offshore positive rhythm low-permeability edge water sandstone gas reservoir, which includes dividing the low-permeability layer, medium-permeability layer, and high-permeability layer longitudinally in the target gas reservoir; respectively obtaining the reservoir geological parameters of the low-permeability layer, medium-permeability layer, and high-permeability layer in the target gas reservoir and the engineering parameters of the horizontal well; respectively determining the toe-end positions of the horizontal wells in the low-permeability layer, medium-permeability layer, and high-permeability layer according to the reservoir geological parameters, the engineering parameters of the horizontal well, and the low-permeability-medium-permeability-high-permeability three-level composite reservoir seepage model; building a longitudinal heterogeneous large-scale physical model seepage test device, injecting water at a constant speed at the edge to simulate the process of edge water invasion, and realizing the visual tracking of the water drive front evolution characteristics under the multi-layer differential well pattern through a transparent glass plate. The present invention is beneficial to alleviating the longitudinal development contradiction, coordinating the differential physical property resistance and the gas drainage power, promoting the uniform advancement of the gas-water interface, and realizing the gas well's gas stabilization and water control and the balanced utilization of the gas reservoir longitudinally and horizontally.

Description

Technical Field

[0001] The present invention relates to a method for optimizing the well positions of multi-layer three-dimensional horizontal wells in a marine positive rhythm low-permeability edge-water sandstone gas reservoir, belonging to the field of oil and gas field development. Background Art

[0002] Due to the large differences in physical properties between layers and the non-uniform distribution of sand bodies in marine positive rhythm low-permeability edge-water gas reservoirs, during the development process, there are characteristics such as uneven edge-water advancement in the vertical direction and strong heterogeneity in utilization, with prominent contradictions in the utilization between and within gas reservoir layers, making it difficult to achieve balanced utilization of reserves. Secondly, restricted by production platforms at sea, the well pattern density is limited, the development investment is large, and the operating costs are high, resulting in a heavy economic task per well. The mature drainage gas production technology and fracturing reconstruction technology on land are difficult to implement on a large scale at sea.

[0003] Therefore, how to effectively utilize limited wellheads to optimize well position design, coordinate the physical property resistance and gas drainage power between layers with different physical properties, achieve the coupling of differential pressure gradient disturbances, and lead to the balanced advancement of edge water in the vertical direction is the key issue for the overall efficient utilization of marine gas reservoirs. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for optimizing the well positions of multi-layer three-dimensional horizontal wells in a marine positive rhythm low-permeability edge-water sandstone gas reservoir in view of the problems existing in the prior art. This method is conducive to alleviating the vertical development contradictions, coordinating the differential physical property resistance and gas drainage power, promoting the uniform advancement of the gas-water interface, and achieving stable gas production and water control of gas wells and the balanced utilization of gas reservoirs in the vertical and horizontal directions.

[0005] The technical solution provided by the present invention to solve the above technical problems is: A method for optimizing the well positions of multi-layer three-dimensional horizontal wells in a marine positive rhythm low-permeability edge-water sandstone gas reservoir, comprising the following steps:

[0006] Step S10: Divide the low-permeability layer, medium-permeability layer, and high-permeability layer longitudinally in the target gas reservoir;

[0007] Step S20: Respectively obtain the reservoir geological parameters of the low-permeability layer, medium-permeability layer, and high-permeability layer in the target gas reservoir and the engineering parameters of the horizontal wells;

[0008] Step S30: Construct a low-permeability-medium-permeability-high-permeability three-level composite reservoir seepage model based on the coupling mechanism of optical wave propagation and reflection;

[0009] Step S40: Respectively determine the horizontal well lengths in the low-permeability layer, medium-permeability layer, and high-permeability layer according to the reservoir geological parameters of the low-permeability layer, medium-permeability layer, and high-permeability layer, the engineering parameters of the horizontal wells, and the low-permeability-medium-permeability-high-permeability three-level composite reservoir seepage model

[0010] Step S50: Build a vertical heterogeneous large-scale physical model for seepage testing. Inject water at a constant rate at the edge to simulate the process of edge water invasion, and visually track the evolution characteristics of the water drive front under the multi-layer differential well pattern through a transparent glass plate.

[0011] A further technical solution is that in step S10, through the multi-level information fusion of core description - 3D seismic - rock physics logging parameters, based on the tectonic - sedimentary - diagenetic evolution characteristics, three layers of low permeability - medium permeability - high permeability are vertically divided.

[0012] A further technical solution is that the reservoir geological parameters include effective thickness, wellbore radius, gas saturation, real gas compression factor, gas viscosity, formation temperature, formation pressure, porosity, and permeability.

[0013] A further technical solution is that the engineering parameters include drainage radius and the distance of the horizontal well from the lower boundary.

[0014] A further technical solution is that the three - level composite reservoir seepage model of low permeability - medium permeability - high permeability is as follows:

[0015]

[0016] In the formula: Z represents the natural gas compression factor; c g represents its compressibility coefficient, MPa -1 ; represents the porosity of the reservoir; μ represents the gas viscosity, mPa•s; δ represents the high - speed non - Darcy characteristic parameter; P represents the current formation pressure, MPa; 、 、 are the permeabilities; represents the current formation pressure of the nth layer, MPa; x 、 y 、 z respectively represent the projection distances in the three coordinate axes; t represents time.

[0017] A further technical solution is that the determination process of the horizontal well length in step S40 is as follows:

[0018] Step A: Set the horizontal well lengths of the three layers of low permeability layer, medium permeability layer and high permeability layer to meet the configuration principle of longer upper and shorter lower.

[0019] Step B: Then, substitute the horizontal well lengths of the low-permeability layer, medium-permeability layer, and high-permeability layer into the seepage model of the low-permeability-medium-permeability-high-permeability three-level composite reservoir respectively to calculate the pressures of the low-permeability layer, medium-permeability layer, and high-permeability layer.

[0020] Step C: Calculate the pressure gradients between the low-permeability layer, medium-permeability layer, and between the medium-permeability layer and high-permeability layer respectively. If the pressure gradient is greater than the maximum pressure gradient threshold between adjacent layers, then decrease and adjust the horizontal well section length of the medium-permeability layer or high-permeability layer, and repeat Step A - Step C until the pressure gradients between the low-permeability layer, medium-permeability layer, and between the medium-permeability layer and high-permeability layer are all less than or equal to the maximum pressure gradient threshold between adjacent layers, then output the final horizontal well lengths of the low-permeability layer, medium-permeability layer, and high-permeability layer.

[0021] A further technical solution is that in the step S50, the geometric length, position, and displacement velocity of the horizontal well in the large-scale physical simulation experiment are determined according to geometric similarity, flow rate similarity, and resistance similarity.

[0022] A further technical solution is that in the step S50, the porosity and permeability of quartz sand with a single mesh number are calibrated through an artificial one-dimensional core to obtain the reservoir physical properties under different confining pressure conditions, and clarify the sand filling scheme under different pressures and pore permeability conditions during the sand filling process of the physical model.

[0023] Advantages of the present invention:

[0024] 1. Considering the low-permeability seepage characteristics and the non-uniform pressure response characteristics between longitudinal multiple layers, a seepage model of the low-permeability-medium-permeability-high-permeability three-level composite reservoir based on the coupling mechanism of optical wave propagation and reflection is constructed, realizing the fine characterization of the comprehensive seepage characteristics of the composite reservoir.

[0025] 2. A three-dimensional multi-layer differential well layout method is proposed to coordinate the physical property resistance and gas drainage power between different layers, promote the uniform advance of the edge water, and is conducive to the uniform production of the gas reservoir.

[0026] 3. A large-size physical model test device is built to truly reflect the longitudinal heterogeneity characteristics of the gas reservoir, realize the visual tracking of the water invasion front under the three-dimensional multi-layer differential well layout mode, and demonstrate the rationality of the well layout strategy. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the propagation and reflection of pressure waves at the interface between different layers in the embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of a three-dimensional multi-layer well pattern of an offshore positive rhythm edge water gas reservoir in the embodiment of the present invention;

[0029] Figure 3 It is a flow chart of a two-dimensional visualization model experiment in the embodiment of the present invention;

[0030] Figure 4 This is for the effect of coordinated uniform edge water advance in the vertical heterogeneous reservoir in the embodiment of the present invention. Specific implementation manner

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work fall within the scope of protection of the present invention.

[0032] A method for optimizing the well positions of multi-layer three-dimensional horizontal wells in an offshore positive rhythm low-permeability edge water sandstone gas reservoir provided by the present invention includes the following steps:

[0033] Step S10: Through multi-level information fusion of core description - 3D seismic - rock physical logging parameters on the target gas reservoir, combine well and seismic data to implement the structural model - sedimentary background - diagenetic evolution law, and reveal the development and distribution law of "sweet spots" in heterogeneous reservoirs; taking into account sedimentary rhythm and physical property differences, three layers of low permeability - medium permeability - high permeability can be divided vertically;

[0034] Step S20: Obtain the reservoir geological parameters and engineering parameters of horizontal wells in the low-permeability layer, medium-permeability layer, and high-permeability layer of the target gas reservoir respectively;

[0035] Among them, the reservoir geological parameters include effective thickness, wellbore radius, gas saturation, real gas compression factor, gas viscosity, formation temperature, formation pressure, porosity, and permeability.

[0036] The engineering parameters include drainage radius and the distance between the horizontal well and the lower boundary.

[0037] Step S30: Construct a three-level composite reservoir seepage model based on the coupling mechanism of optical and electrical wave propagation and reflection;

[0038] Considering the stress sensitivity and non-Darcy seepage characteristics of the low-permeability layer, the permeability can be expressed as:

[0039]

[0040] In the formula: K represents the current reservoir permeability, K i represents the permeability in the original state of the reservoir, mD; α represents the stress sensitivity coefficient; P i represents the original formation pressure, MPa; P represents the current formation pressure, MPa; δ represents the high-speed non-Darcy characteristic parameter.

[0041] High-speed non-Darcy characteristic parameter δ It can be characterized by the seepage velocity and the Forchheimer coefficient:

[0042]

[0043] In the formula: β represents the Forchheimer coefficient related to the non-Darcy seepage characteristics; v represents the seepage velocity, m / d; ρ represents the gas density, g / m 3 ; μ represents the gas viscosity, mPa•s.

[0044] For a multi-layer composite gas reservoir, combined with the unsteady continuity equation, gas state equation, etc., the real gas seepage equation can be expressed as:

[0045]

[0046] In the formula: Z represents the natural gas compressibility factor; c g represents its compressibility coefficient, MPa -1 ; represents the porosity of the reservoir; μ represents the gas viscosity, mPa•s; δ represents the high-speed non-Darcy characteristic parameter; P represents the current formation pressure, MPa; , , are the permeabilities; represents the current formation pressure of the nth layer, MPa; x , y , z respectively represent the projected distances in the three coordinate axes; t represents time.

[0047] Dimensionless variables:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053] In the formula: h is the layer where the horizontal well is located, zw is the distance of the horizontal well from the lower boundary, L w is the half-length of the horizontal well.

[0054] Pseudo-pressure m is:

[0055]

[0056] In the formula: P 0 is the reference pressure, taking the atmospheric pressure;

[0057] The model is made dimensionless through characteristic parameters such as pressure, time, and wellbore radius. Among them, the dimensionless pressure (m D ) h and time t D are:

[0058]

[0059]

[0060] In the formula: h h is the thickness of the small layer where the horizontal well is located, m; T sc is the temperature under standard conditions, 273.15 K; p sc is the pressure under standard conditions, 0.101 MPa; q sc is the gas flow rate under surface conditions, m 3 ; T is the temperature, K; m ini is the original pseudo-pressure; ( m w ) h ( t ) is the pseudo-pressure at the bottom of the horizontal well at any moment; c t is the comprehensive compressibility, MPa -1 .

[0061] The dimensionless wellbore radius is r wD :

[0062]

[0063] Introduce the Green's function of a point source in a closed formation, perform a constant-pressure boundary treatment on the top and bottom of the reservoir, and solve in the Laplace space to obtain the differential response characteristics of the multi-layer pressure,

[0064]

[0065] In the formula:s is the Laplace space variable; s / k n is the dimensionless variable;

[0066] Written as a partial differential equation of the Green's function, where the pressure of the h sub-layer where the horizontal well is located is:

[0067]

[0068] In the formula: r is the seepage radius of any point in the formation, m; G is the Green's function;

[0069] The pressures of the other n sub-layers are respectively:

[0070]

[0071] Given the boundary conditions:

[0072]

[0073] In the formula: r D is the dimensionless radial distance; r eD is the dimensionless supply boundary radius;

[0074] Therefore, the point source solution of the h layer where the horizontal well is located is expressed as:

[0075]

[0076] In the formula: U represents the upward propagation coefficient; D represents the downward propagation coefficient.

[0077] Finally, through the Stehfest numerical inversion, the dimensionless pressure (m D ) h and time t D relationship are obtained, so as to determine the relationship between pressure and production.

[0078] Step S40: According to the reservoir geological parameters of the low-permeability layer, medium-permeability layer, and high-permeability layer, the engineering parameters of the horizontal well, and the seepage model of the low-permeability-medium-permeability-high-permeability three-level composite reservoir, determine the lengths of the horizontal wells in the low-permeability layer, medium-permeability layer, and high-permeability layer respectively;

[0079] As Figure 1 shown, for the pressure disturbances between different layers, the propagation of the pressure wave will change at each layer boundary. By analogy with the reflection principle of waves at the interface in optoelectronics, local reflection and propagation coefficients are established to solve the pressure response characteristics between different layers.

[0080] For different permeability layers in the gas reservoir, based on the productivity formula, calculate the influence of factors such as different horizontal well lengths and vertical positions within the layer on productivity, and preliminarily clarify the reasonable range of factors such as horizontal well length.

[0081] Since the sand body distribution in the low-permeability layer of the target block shows a discontinuous and non-uniform distribution law, based on the development and distribution law of "sweet spots" in its heterogeneous reservoir, long horizontal wells that can penetrate multiple "sweet spots" are preferably selected for development. First, determine the target point position at the toe end of the upper low-permeability reservoir to release the productivity of the low-permeability reservoir.

[0082] By analogy with the propagation and reflection of pressure at different layer interfaces, obtain the non-uniform distribution characteristics of the pressure in the low-permeability layer and the pressure in other layers in the vertical direction. Subsequently, use the redistributed pressure as the input parameter and substitute it into the seepage equation of the medium-permeability layer to update the calculation of the pressure response under the influence of reservoir physical properties, horizontal well parameters, and production in the medium-permeability layer. On this basis, further calculate the overall pressure disturbance and redistribution caused by the deployment of horizontal wells in the high-permeability layer.

[0083] Due to the different seepage resistances caused by the physical property differences in the vertical direction, during the setting of the horizontal well length, in order to coordinate the difference in gas drainage power, the horizontal well length gradually decreases from the low-permeability layer to the high-permeability layer to balance the disturbance scale of the pressure fields in different sub-layers. Initially set the length relationship of the horizontal wells in the upper low-permeability layer, the middle medium-permeability layer, and the lower high-permeability layer to meet the configuration principle of "longer in the upper part and shorter in the lower part", with the initial settings being 1600 m, 1000 m, and 800 m respectively. Secondly, for the reasonable selection of the well position, calculate the pressure gradient of each layer through the pressure difference between the bottom hole pressure obtained and the pressure at the edge water position of the side. Coordinate the disturbance scale of the pressure fields in different sub-layers from the top low-permeability layer to the bottom high-permeability layer. The horizontal well length gradually decreases from top to bottom, and the toe end is gradually farther away from the edge water, forming a "three-layer" three-dimensional horizontal well distribution pattern as shown in Figure 2 shown.

[0084] The determination process of the horizontal well length is as follows:

[0085] Step A: Set the horizontal well lengths of the low-permeability layer, the medium-permeability layer, and the high-permeability layer to meet the configuration principle of longer in the upper part and shorter in the lower part;

[0086] Step B: Then substitute the horizontal well lengths of the low-permeability layer, the medium-permeability layer, and the high-permeability layer into the low-permeability-medium-permeability-high-permeability three-level composite reservoir seepage model respectively to calculate the pressures of the low-permeability layer, the medium-permeability layer, and the high-permeability layer;

[0087] Step C: Calculate the pressure gradients between the low-permeability layer, the medium-permeability layer, and between the medium-permeability layer and the high-permeability layer respectively. If the pressure gradient is greater than the maximum pressure gradient threshold between adjacent layers, then decrease the horizontal well section length of the medium-permeability layer or the high-permeability layer (the adjustment step is 50 m). Repeat Step A - Step C until the pressure gradients between the low-permeability layer, the medium-permeability layer, and between the medium-permeability layer and the high-permeability layer are all less than or equal to the maximum pressure gradient threshold between adjacent layers, then output the final horizontal section length of the upper low-permeability layer as 1200 m, the horizontal section length of the medium-permeability layer as 700 m, and the horizontal section length of the high-permeability layer as 400 m.

[0088] Step S50: Build a vertical heterogeneous large-scale physical model seepage test device (as shown in Figure 3 ), inject water at a constant speed at the edge to simulate the process of edge water invasion, and realize the visual tracking of the water drive front evolution characteristics under the multi-layer differential well pattern through the transparent glass plate.

[0089] To further verify the established three-dimensional horizontal well pattern for delaying the problem of local edge water breakthrough, build a large-scale physical model test device as shown in Figure 4 , the size of the three-dimensional effective space is 50×50×2 cm 3 , and determine the experimental basic parameters such as the geometric length and position of the horizontal well and the displacement velocity in the large-scale physical simulation experiment according to geometric similarity, flow similarity, resistance similarity, etc.

[0090] Based on artificial one-dimensional cores, calibrate the porosity and permeability of single-mesh quartz sand. The selected quartz sands are five types of 200 - 230, 300 - 330, 400 - 430, 500 - 530 respectively. Through physical property tests on small lithologies made of 10 ratios under different confining pressure conditions, its permeability mainly ranges from 1 to 160 mD, and the porosity mainly ranges from 10% to 18%, and clarify the sand filling scheme of the physical model under different pressure and porosity-permeability conditions. The permeability distribution range of the block in the embodiment is mainly 10 - 120 mD.

[0091] Use the wet filling method to fill the sand into the two-dimensional visualization model. In order to ensure the uniform stress of the model, 16 sets of high-pressure hydraulic devices are used to change the overburden pressure of the model to simulate the reservoir environment. After the model is pressed, it needs to be poured and sealed with epoxy resin. Place the pressed model into a customized mold, melt the epoxy resin, pour it into the mold, and pour and seal the model. Stand the two-dimensional flat model upright, inject water into the model from the bottom valve until water comes out from all the top valves and observe that the sand body inside the model is filled with water. After the model is left standing for 24 hours, inject gas from the top valve to establish the original gas saturation.

[0092] While conducting horizontal well production, water is injected at a constant rate at the edge to simulate the process of edge water invasion. The visualization tracking of the evolution characteristics of the water drive front under the multi-layer differential well pattern is realized through a transparent glass plate. As Figure 4 shown, the horizontal well lengths of the horizontal sections from the top to the bottom decrease in sequence, and the toe ends are successively farther away from the edge water. Through the differential horizontal well deployment in the vertical direction, the gas-water interface regions of the three layers of low permeability - medium permeability - high permeability in the two-dimensional model are relatively flat, demonstrating the rationality of the well pattern strategy.

[0093] The water cut at the wellhead is calculated by a metering device, and 99% is used as the critical condition for shutting down the gas well. The calculation results of the recovery factor show that through the arrangement of the vertical three-dimensional well pattern, the edge water at the three layers in the vertical direction tends to advance synchronously, basically realizing the balanced development of the gas reservoir, and effectively alleviating the contradictions between layers and within layers.

[0094] Table 1 Recovery degrees of each small layer in the vertical direction of the gas reservoir

[0095]

[0096] A method for optimizing the well positions of multi-layer three-dimensional horizontal wells in an offshore positive rhythm low-permeability edge water sandstone gas reservoir provided by the present invention, based on the structural - sedimentary - diagenetic evolution characteristics, taking into account the sedimentary rhythm and physical property differences, finely divides the low-permeability - medium-permeability - high-permeability layers in the vertical direction; considering the low-permeability seepage characteristics and the non-uniform pressure response characteristics between multiple vertical layers, constructs a composite reservoir seepage model of the pressure propagation and reflection coupling mechanism at the layered interface; preferentially determines the toe end position of the upper low-permeability reservoir, and gradually optimizes the toe end position from top to bottom to form a "three-layer" three-dimensional well pattern, coordinates the pressure field disturbances of different small layers, and promotes the uniform advance of the edge water. By building a vertical heterogeneous large-scale physical model seepage test device, the visualization tracking of the edge water invasion front under the multi-layer differential well pattern is realized, and the rationality of the well pattern strategy is demonstrated.

[0097] The present invention helps to effectively utilize the limited wellheads of offshore platforms to optimize the well position design, coordinates the physical property resistance and gas drainage power between layers with different physical properties, realizes the coupling of differential pressure gradient disturbances, can solve the inter-layer contradictions in the edge water drive development mode of offshore positive rhythm reservoirs, leads the uniform advance of the edge water front in the vertical direction, and realizes stable gas control and balanced utilization of the gas reservoir in the vertical and horizontal directions.

[0098] As described above, it is not any form of limitation to the present invention. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, can make some changes or modifications to the above-disclosed technical content to obtain equivalent embodiments of equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention all fall within the scope of the technical solution of the present invention.

Claims

1. A method for optimizing the well location of multi-layered horizontal wells in an offshore positive rhythm low permeability edge water sandstone gas reservoir, characterized in that: The following steps are involved: Step S10, dividing the target gas reservoir into a low permeability layer, a medium permeability layer, and a high permeability layer in the longitudinal direction; Step S20, respectively obtaining reservoir geological parameters of the low permeability layer, the medium permeability layer, and the high permeability layer in the target gas reservoir and engineering parameters of the horizontal well; Step S30, constructing a three-level composite reservoir seepage model of low permeability, medium permeability and high permeability based on the photoelectric wave propagation and reflection coupling mechanism; The three-level composite reservoir seepage model of low permeability, medium permeability and high permeability is: Where: Z represents the natural gas compression factor; c g Indicates the compression coefficient, MPa -1 ; Indicates the porosity of the reservoir; μ Indicates gas viscosity, mPa•s; δ represents high-speed non-Darcy characteristic parameters; P Indicates the current formation pressure, MPa; , , is the permeability; Indicates the current formation pressure of layer n, MPa; x , y , z Respectively represent the projection distances in the three directions of the coordinate axis; t Indicates time; Step S40, determining the length of the horizontal well in the low permeability layer, the medium permeability layer, and the high permeability layer respectively according to the reservoir geological parameters of the low permeability layer, the medium permeability layer, and the high permeability layer, the engineering parameters of the horizontal well, and the low permeability-medium permeability-high permeability three-level composite reservoir seepage model; Step S50, construct a longitudinal heterogeneous large-scale physical model seepage test device, inject water at a constant rate at the edge to simulate the process of edge water invasion, and realize the visual tracking of the evolution characteristics of the water drive front in the multi-layer differentiated well mode through a transparent glass plate.

2. The method for optimizing the well location of multi-layer horizontal wells in an offshore positive rhythm low permeability edge water sandstone gas reservoir according to claim 1, characterized in that: In step S10, by fusion of multi-level information of core description, 3D seismic and rock physical logging parameters, three layers of low permeability, medium permeability and high permeability are vertically divided based on the structural, sedimentary and diagenetic evolution characteristics.

3. The method for optimizing the well location of multi-layered horizontal wells in an offshore positive rhythm low permeability edge water sandstone gas reservoir according to claim 1, characterized in that: The reservoir geological parameters include effective thickness, wellbore radius, gas saturation, true gas compressibility factor, gas viscosity, formation temperature, formation pressure, porosity, and permeability.

4. The method for optimizing the well location of multi-layered horizontal wells in an offshore positive rhythm low permeability edge water sandstone gas reservoir according to claim 1, characterized in that: The engineering parameters include the gas leakage radius and the distance between the horizontal well and the lower boundary.

5. The method for optimizing the well location of multi-layered horizontal wells in an offshore positive rhythm low permeability edge water sandstone gas reservoir according to claim 1, characterized in that: The process of determining the horizontal well length in step S40 is as follows: Step A, setting the lengths of the three horizontal wells in the low permeability layer, the medium permeability layer and the high permeability layer to meet the configuration principle of long at the top and short at the bottom; Step B, respectively substituting the lengths of the three horizontal wells of the low permeability layer, the medium permeability layer and the high permeability layer into the low permeability-medium permeability-high permeability three-level composite reservoir seepage model to calculate the pressures of the low permeability layer, the medium permeability layer and the high permeability layer; Step C, respectively calculate the pressure gradient between the low permeability layer, the medium permeability layer, and the medium permeability layer and the high permeability layer. If the pressure gradient is greater than the maximum pressure gradient threshold between adjacent layers, the horizontal well section length of the medium permeability layer or the high permeability layer is adjusted downward, and steps A to C are repeated until the pressure gradients between the low permeability layer, the medium permeability layer, and the medium permeability layer and the high permeability layer are all less than or equal to the maximum pressure gradient threshold between adjacent layers, and then the final horizontal well lengths of the low permeability layer, the medium permeability layer, and the high permeability layer are output.

6. The method for optimizing the well location of multi-layered horizontal wells in an offshore positive rhythm low permeability edge water sandstone gas reservoir according to claim 1, characterized in that: In the step S50, the geometric length and position of the horizontal well and the displacement speed of the large-scale physical simulation experiment are determined based on geometric similarity, flow similarity and resistance similarity.

7. The method for optimizing the well location of multi-layered horizontal wells in an offshore positive rhythm low permeability edge water sandstone gas reservoir according to claim 1, characterized in that: In step S50, the porosity and permeability of single-mesh quartz sand are calibrated by artificial one-dimensional cores to obtain reservoir properties under different confining pressure conditions and clarify the sand filling scheme under different pressures and porosity and permeability conditions during the sand filling process of the physical model.

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