Well spacing method for multi-thin-layer tight sandstone gas reservoir under complex topographic and geomorphic conditions

Abstract

The invention provides a well spacing method for a multi-thin-layer tight sandstone gas reservoir under complex landform conditions. The well spacing method comprises the following steps: finely describing a sand body structure, determining the development scale and characteristics of a single sand body, and constructing a width-to-thickness ratio empirical formula of the single sand body; according to a sedimentary microfacies research result of a to-be-distributed well area and a single sand body width-to-thickness ratio empirical formula, drawing a plane distribution diagram of each layer of sand body, according to a reservoir parameter standard of the to-be-distributed well area, compiling and developing a favorable area in a layered manner, and overlapping to form a construction and production favorable area plane graph; collecting interference well testing data of a to-be-distributed well area or an adjacent area, counting well row spacing when interference is seen so as to determine reasonable well spacing of the to-be-distributed well, and carrying out numerical simulation to optimize the well pattern model; according to the method, topographic and geomorphic characteristics are considered as a whole, and in a construction and production superposition favorable area, a regular hexagon seven-point well pattern is adopted for well spacing, so that the well pattern is matched with a topographic and geomorphic target body. The problem that in the prior art, a multi-thin-layer sandstone gas reservoir is not prone to forming a well site under the complex landform condition is solved.

Description

Technical Field

[0001] This invention relates to the field of natural gas development technology, and more specifically, to a well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex terrain conditions. Background Technology

[0002] Continental sedimentary thin-layered sandstone oil and gas reservoirs are generally characterized by being "thin and multi-layered," with wide planar distribution, numerous vertical gas-bearing layers, small effective thickness of individual layers, and small interlayer thickness. The geological characteristics of thin-layered interbedded gas reservoirs lead to unsatisfactory development results, low gas production rates and recovery rates, and significant challenges in achieving stable production. In recent years, with the deepening of oil and gas exploration and development, the numerous distributed thin-layered interbedded multi-layered reservoirs have gradually become important resources for increasing oil production. For such gas reservoirs, well pattern and spacing technology is a key technology for improving single-well controlled reserves and recovery rates, and achieving effective large-scale development of gas fields. However, due to the complex relationship between well pattern and spacing and topography, reservoir structure, single-well production, and block development benefits, the well pattern design for multi-layered gas reservoirs has significant uncertainties. Furthermore, existing well placement methods do not consider the well site formation under complex topographic conditions, the changes in horizontal sections during horizontal well construction, or the difficulties in later well pattern densification.

[0003] As can be seen from the above, the existing technology has the problem that it is not easy to form a well site for multi-thin sandstone gas reservoirs under complex terrain and geomorphological conditions. Summary of the Invention

[0004] The main objective of this invention is to provide a well placement method for multi-thin-layer tight sandstone gas reservoirs under complex terrain conditions, so as to solve the problem that it is not easy to form well sites for multi-thin-layer sandstone gas reservoirs under complex terrain conditions in the prior art.

[0005] To achieve the above objectives, this invention provides a well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex topographic conditions, comprising: Step S1: collecting relevant data on the area to be well placed, finely characterizing the sand body structure, clarifying the development scale and characteristics of individual sand bodies, and constructing an empirical formula for the width-to-thickness ratio of individual sand bodies; Step S2: based on the sedimentary microfacies research results of the area to be well placed and the empirical formula for the width-to-thickness ratio of individual sand bodies, drawing a planar distribution map of each layer of sand bodies, and compiling favorable development areas layer by layer according to the reservoir parameter standards of the area to be well placed, and superimposing them to form a planar map of favorable production areas; Step S3: collecting interference test data of the area to be well placed or adjacent areas, statistically analyzing the well spacing when interference is observed, to determine the reasonable well spacing for the wells to be placed, and conducting numerical simulation to optimize the well network model; Step S4: taking into account the topographic features, within the favorable production superposition area, using the reasonable well spacing for the wells to be placed as the well spacing, adopting a regular hexagonal seven-point well network for well placement, while also considering the orientation and space of horizontal well deployment, so that the well network is compatible with the topography and geological targets.

[0006] Furthermore, step S1 also includes: establishing a grid-shaped profile to finely depict the sand body structure and clarify the development scale and characteristics of individual sand bodies.

[0007] Furthermore, in step S2, the sedimentary microfacies study results include at least one of lithology, paleontology, and geochemical markers.

[0008] Furthermore, step S2 also includes: establishing reservoir parameter standards for the well-to-be-placed area by analyzing the correlation between the reservoir parameters of the test layer and the unobstructed flow rate.

[0009] Furthermore, in step S4, the orientation of the horizontal well deployment is determined by the orientation of the main gas-bearing sand body in the area to be deployed.

[0010] Furthermore, step S4 also includes: when using a regular hexagonal seven-point well network, the length of the horizontal well is adjusted by 0.5 or 1 well spacing according to the sand body development and the distance in front of the target.

[0011] The well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex topographic conditions, applying the technical solution of this invention, includes the following steps: Step S1: Collect relevant data on the area to be well placed, finely characterize the sand body structure, clarify the development scale and characteristics of individual sand bodies, and construct an empirical formula for the width-to-thickness ratio of individual sand bodies; Step S2: Based on the sedimentary microfacies research results and the empirical formula for the width-to-thickness ratio of individual sand bodies in the area to be well placed, draw a planar distribution map of each layer of sand bodies, and according to the reservoir parameter standards of the area to be well placed, compile favorable development areas layer by layer, and overlay them to form a planar map of favorable production areas; Step S3: Collect interference test data from the area to be well placed or adjacent areas, and statistically analyze the well spacing when interference is observed to determine the optimal well placement area. Step S4: Taking into account the topographic features, within the favorable area of ​​overlapping production areas, a hexagonal seven-point well network is used as the well spacing to be deployed, while also considering the orientation and space of horizontal well deployment to ensure that the well network is compatible with the topography and geological targets. This hexagonal seven-point well network allows for a certain range of well site movement within the drilling rig's capabilities, facilitating well site formation under complex topographic conditions. It saves both land and investment, solving the problem of difficulty in forming well sites in complex topographic conditions for multi-layered sandstone gas reservoirs in existing technologies. Furthermore, the well deployment method of this application fully utilizes the relationship between well spacing and target distance to achieve compatibility between the actual length of the horizontal section and the well network after successful horizontal well implementation, improving reservoir control and reserve utilization. It has the advantages of being easy to operate and implement at different stages, and the scheme design stage can achieve "centralized deployment and one-time network formation," saving manpower. Furthermore, the well placement method proposed in this application allows for phased implementation in the early stages without affecting the well network. Even if the well network needs to be densified later to exploit smaller secondary producing layers, it can be done at equal intervals without changing the overall well network pattern. This allows for comprehensive consideration of the vertical development characteristics of multiple thin-layer gas reservoirs, enabling effective utilization of low-quality reserves in these thin layers and improving natural gas recovery. Moreover, the well placement method in this application employs a large-well-group model for production capacity construction. During the production phase, the relatively small number of well sites and management nodes reduce manpower and lower management costs. Attached Figure Description

[0012] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0013] Figure 1 A flowchart of a well placement method for multi-thin-layer tight sandstone gas reservoirs under complex terrain conditions is shown in a specific embodiment of the present invention.

[0014] Figure 2 A diagram illustrating a single-wellfield well location deployment pattern in a specific embodiment of the present invention is shown.

[0015] Figure 3 This diagram illustrates a first well site and well type combination mode according to a specific embodiment of the present invention.

[0016] Figure 4 A diagram illustrating a second well site and well type combination mode in a specific embodiment of the present invention is shown. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0019] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0020] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0021] To address the problem that existing technologies often fail to establish well sites for multi-thin sandstone gas reservoirs under complex terrain conditions, this invention provides a well placement method for multi-thin tight sandstone gas reservoirs under complex terrain conditions.

[0022] like Figure 1As shown, the well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex topographic conditions includes: Step S1: Collect relevant data on the area to be well placed, finely characterize the sand body structure, clarify the development scale and characteristics of individual sand bodies, and construct an empirical formula for the width-to-thickness ratio of individual sand bodies; Step S2: Based on the sedimentary microfacies research results and the empirical formula for the width-to-thickness ratio of individual sand bodies in the area to be well placed, draw a planar distribution map of each layer of sand bodies, and compile favorable development areas layer by layer according to the reservoir parameter standards of the area to be well placed, and superimpose them to form a planar map of favorable production areas; Step S3: Collect interference test data of the area to be well placed or adjacent areas, count the well spacing when interference is observed, determine the reasonable well spacing of the wells to be placed, and conduct numerical simulation to optimize the well network model; Step S4: Taking into account the topographic and geomorphological characteristics, within the favorable production superposition area, use the reasonable well spacing of the wells to be placed as the well spacing, adopt a regular hexagonal seven-point well network layout, and simultaneously consider the deployment orientation and space of horizontal wells to ensure that the well network is compatible with the topography, geomorphology, and geological targets.

[0023] The well placement method proposed in this application employs a hexagonal seven-point well network. Within the drilling rig's capabilities, this allows for a certain range of well site movement, facilitating well site formation under complex terrain conditions and saving both land and investment. Furthermore, this method fully utilizes the relationships between well spacing and target distance to ensure compatibility between the actual length of the horizontal section and the well network after successful horizontal well implementation. This improves reservoir control and reserve utilization. It offers advantages of ease of operation and implementation at all stages, enabling "centralized deployment and one-time network formation" during the design phase, saving manpower. Moreover, using this method, phased implementation in the early stages does not affect well network changes. Even if subsequent mining of smaller secondary producing layers requires densification of the well network, equal-interval densification can be used without altering the network form. This allows for comprehensive consideration of the vertical development characteristics of multiple thin-layer gas reservoirs, enabling effective utilization of low-quality reserves and improving natural gas recovery. Furthermore, the well placement method of this application adopts a large well group model for production capacity construction. During the production stage, due to the relatively small number of well sites and reduced management nodes, manpower can be saved and management costs can be reduced.

[0024] In this embodiment, the empirical formula for the width-to-thickness ratio of a single sand body is:

[0025] w = 59.9h 1.8 ;

[0026] h = 1.5L;

[0027] Where h is the water depth in meters (m); L is the maximum thickness of a single sand body in the channel in meters (m); and w is the width of the channel in meters (m).

[0028] In this embodiment, the well placement method not only considers the well network design during the production capacity construction phase, but also takes into account the densification and adjustment in the later stages of development. At the same time, it facilitates production management, greatly reduces the workload, and saves on manual management costs.

[0029] In this embodiment, step S1 further includes: establishing a grid-shaped profile to finely depict the sand body structure and clarify the development scale and characteristics of individual sand bodies.

[0030] In this embodiment, in step S2, the sedimentary microfacies research results include at least one of lithology, paleontology, and geochemical markers.

[0031] In this embodiment, step S2 further includes: establishing reservoir parameter standards for the well-to-be-placed area by analyzing the correlation between the reservoir parameters of the test layer and the unobstructed flow rate.

[0032] In this embodiment, in step S4, the horizontal well deployment orientation is determined by the orientation of the main gas layer sand body in the well-to-be-deployed area.

[0033] In this embodiment, step S4 further includes: when using a regular hexagonal seven-point well network, the length of the horizontal well is adjusted by 0.5 or 1 well spacing according to the sand body development and the target distance.

[0034] In this embodiment, as Figure 2 As shown, well sites are selected by surveying within a radius of about 200m based on the terrain. The distance of well site movement can be adjusted appropriately according to the drilling rig capacity and well depth; the bottom coordinates and well spacing are relatively fixed.

[0035] In this embodiment, as Figure 3 As shown in Figure ①, the length of the horizontal well section is adjusted by 0.5 or 1 well spacing according to the sand body development and target distance, without affecting the well pattern. Figure ② shows that the azimuth angle of the horizontal section of the horizontal well is adjusted according to the sand body development direction to achieve optimal matching between the horizontal section and the sand body. Figure ③ shows that starting from the central well, directional wells can be drilled further away, provided the drilling rig capacity is sufficient, without affecting the well pattern. Furthermore, Figure ④ shows that each well point in this application can serve as a central well without affecting the well pattern. Further, as... Figure 4 As shown, the well locations ①②③ remain unchanged, while the location of the central well ④ can be changed at will.

[0036] The well placement method of this application will be explained in detail below using a specific gas field as an example.

[0037] (1) Collect relevant data on the well area to be laid out, establish a grid-shaped profile, clarify the development scale and characteristics of single sand bodies, finely depict the structure of multiple gas-bearing sand bodies such as Taiyuan Formation, Shan 2, Shan 1, and He 8, and construct a single sand body with a width-to-thickness ratio between 50:1 and 270:1.

[0038] (2) Make full use of lithological, paleontological and geochemical indicators to clarify that the Daibujing area belongs to the delta-shallow lacustrine sedimentary system, mainly developing the delta front and delta plain octagon. The underwater distributary channel is the most favorable sedimentary microfacies. Based on the research results of sedimentary microfacies in the Daibujing area, combined with the empirical formula of sand body width-to-thickness ratio, draw the planar distribution map of each layer of sand body.

[0039] (3) By analyzing the correlation between reservoir parameters and flow rate in the test layer, reservoir parameter standards for the well-to-be-placed area are established, favorable development areas are drawn in layers, and then superimposed to form a plan of favorable production area.

[0040] (4) Collect well test data on interference in the area to be laid out or adjacent areas, count the well spacing when interference occurs, determine the reasonable well spacing in the area to be laid out as 600m, and carry out numerical simulation to optimize the well network model.

[0041] (5) Based on the preliminary work, in the favorable area of ​​overlapping production areas, a seven-point hexagonal well network with a well spacing of 600m is used for overall well placement. To ensure the drilling effect of horizontal wells, the azimuth of the horizontal wells is mainly determined by the strike of the main gas layer sand body in the area to be welled, which is 0° or 180°. According to the development plan of this gas field, the reasonable length of the horizontal wells in the area to be welled is 1500m. Since the target distance of the horizontal wells is designed to be 500m, during the field implementation, the length of the horizontal section can be adjusted within the range of 1500±300m according to the development scale of the sand body and the change of the target distance. The regularity of the well network and well spacing will not be affected.

[0042] (6) Since the gas field is located on the Loess Plateau with complex topography and geomorphology, the main target layer is developed at a depth of about 2500m. In combination with the fact that the drilling rig model used in the gas field production capacity construction is mainly ZJ40J, in order to ensure that the drilling rig has spare capacity to handle complex situations and has the ability to drill normally to the farthest well in the well group, it is initially determined to conduct a reconnaissance of the well site within 200m of the central well, so as to achieve the best matching between the well network and the topography and geological target body, and improve the utilization of reserves.

[0043] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: The well placement method of this application adopts a hexagonal seven-point well network, which allows for a certain range of well site movement within the drilling rig's capacity, thus facilitating well site formation under complex terrain conditions, saving both land and investment. Furthermore, the well placement method of this application can fully utilize the relationship between well spacing, target distance, etc., to achieve compatibility between the actual length of the horizontal section and the well network after successful horizontal well implementation, improving reservoir control and reserve utilization. It has the advantages of being easy to operate and implement at different stages, and the scheme design stage can achieve "centralized deployment and one-time network formation," saving manpower. Further, using the well placement method of this application, phased implementation in the early stages does not affect the well network changes. Even if the well network needs to be densified later for mining smaller secondary producing layers, it can be densified at equal intervals without changing the well network form. This allows for comprehensive consideration of the vertical development characteristics of multiple thin-layer gas reservoirs, achieving effective utilization of multiple thin-layer low-quality reserves and improving natural gas recovery. Furthermore, the well placement method of this application adopts a large well group model for production capacity construction. During the production stage, due to the relatively small number of well sites and reduced management nodes, manpower can be saved and management costs can be reduced.

[0044] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0045] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex topographic conditions, characterized in that, include: Step S1: Collect relevant data on the area to be laid out, finely characterize the sand body structure, clarify the development scale and characteristics of individual sand bodies, and construct an empirical formula for the width-to-thickness ratio of individual sand bodies; Step S2: Based on the research results of sedimentary microfacies in the area to be welled and the empirical formula for the width-to-thickness ratio of the single sand body, draw a planar distribution map of each layer of sand bodies. Based on the reservoir parameter standards of the area to be welled, compile a layered map of favorable development areas and overlay them to form a planar map of favorable production areas. Step S3: Collect interference test data of the area to be deployed or adjacent areas, count the well spacing when interference occurs, determine the reasonable well spacing to be deployed, and carry out numerical simulation to optimize the well network model; Step S4: Taking into account the topographic features, within the favorable area of ​​overlapping production sites, the well spacing is set as the reasonable well spacing to be deployed. A regular hexagonal seven-point well network is adopted, while also considering the orientation and space of horizontal well deployment, so that the well network is compatible with the topography and geological targets.

2. The well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex topographic conditions according to claim 1, characterized in that, Step S1 further includes: By establishing a grid-shaped profile to finely depict the sand body structure, the development scale and characteristics of individual sand bodies can be clarified.

3. The well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex topographic conditions according to claim 1, characterized in that, In step S2, the sedimentary microfacies study results include at least one of lithology, paleontology, and geochemical markers.

4. The well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex topographic conditions according to claim 1, characterized in that, Step S2 further includes: By analyzing the correlation between reservoir parameters of the test layer and unobstructed flow rate, a reservoir parameter standard for the well-to-be-placed area is established.

5. The well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex topographic conditions according to claim 1, characterized in that, In step S4, the orientation of the horizontal well deployment is determined by the orientation of the main gas-bearing sand body in the area to be well deployed.

6. The well placement method for multi-layered thin-walled tight sandstone gas reservoirs under complex topographic conditions according to claim 1, characterized in that, Step S4 further includes: When using the aforementioned hexagonal seven-point well network, the length of the horizontal well section is adjusted by 0.5 or 1 well spacing according to the sand body development and the distance in front of the target.

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