A low-yield horizontal well management method based on fine injection-production correspondence

Abstract

The present invention discloses a low-yield horizontal well treatment method based on fine injection-production correspondence, which relates to the field of development of low-permeability and ultra-low-permeability multi-stage sedimentary superimposed sandstone oil reservoirs, and particularly to a low-yield horizontal well treatment method based on fine injection-production correspondence, comprising the following steps: finely dividing the multi-layer sedimentary superimposed sandstone where the target layer of the horizontal section of the horizontal well is located; establishing a well-connected sand body profile comparison diagram of the horizontal well and the water injection well; judging the injection-production correspondence relationship of the well-connected profile, and qualitatively and quantitatively analyzing and judging the three-dimensional injection-production correspondence relationship; classifying and determining horizontal well group treatment methods and measures based on the causes of low production; the present invention performs fine stratigraphic division on the multi-layer sedimentary superimposed sandstone where the target layer of the horizontal section of the horizontal well is located, and then establishes a well-connected sand body profile comparison diagram of the horizontal well and the water injection well of the horizontal well group, analyzes and evaluates the fine injection-production correspondence relationship, thereby increasing water drive reserves, promoting the effectiveness of horizontal well water injection, and increasing production, thereby effectively treating low-yield horizontal wells.

Description

Technical Field

[0001] The present invention relates to the field of development of low-permeability and ultra-low-permeability multi-stage sedimentary superimposed sandstone oil reservoirs, and in particular to a method for treating low-yield horizontal wells in a combined direct injection and horizontal production well pattern (horizontal well oil production and vertical well area water injection), and more particularly to a method for treating low-yield horizontal wells based on fine injection and production correspondence. Background Art

[0002] For low- and ultra-low permeability sandstone reservoirs, multi-stage fracturing horizontal well technology is an effective means of increasing single-well production. Water injection is an economical and long-lasting method for replenishing formation energy. Therefore, the combined direct injection and horizontal production pattern technology has been widely used for the efficient development of ultra-low permeability reservoirs. However, in long-term development practice, a large number of low-yielding horizontal wells have emerged. Because testing technologies such as horizontal well segment pressure and production profiles are expensive and inaccurate, it is difficult to directly analyze the production status of horizontal well segments. Therefore, the reasons for low horizontal well production are not fully understood, and the treatment of inefficient horizontal wells has become a major challenge in the efficient development of horizontal wells.

[0003] For multi-stage sedimentary superimposed sandstones, the conventional wisdom holds that a single hydraulic fracture, sufficiently high to penetrate the mudstone or physical interlayers between two adjacent sandstone reservoirs, effectively mobilizing multiple individual sand bodies vertically. However, Tang Pengfei, Liu Yuzhang, and others have demonstrated through experiments and fracturing practice that interlayer stress differentials are the primary factor influencing the vertical extension of hydraulic fractures. The greater the interlayer stress differential, the greater the difficulty in achieving fracture penetration, and the hydraulic pressure must overcome the interlayer stress differential to achieve vertical fracture penetration. Specifically, a single hydraulic fracturing curve must contain multiple fracture pressure peaks, with each peak exceeding the previous one by a factor exceeding the interlayer stress differential between adjacent layers in the perforated section, for fractures to achieve vertical fracture penetration. In reality, this phenomenon is rarely observed in numerous staged fracturing curves, with fractures typically extending along the plane of the sandstone within the perforated section.

[0004] Taking the Chang 6 oil reservoir in the Triassic Yanchang Formation of the Ordos Basin as an example, thin interlayers, including mudstone, calcareous, and physical interlayers, are present in multi-stage sedimentary superimposed sandstone reservoirs, interbedded with sandstone. During the process of displacing crude oil, injected water is less likely to vertically penetrate the adjacent thin interlayers above and below the sandstone due to their poorer physical properties and higher fracture pressure. Therefore, if the perforated sandstone sections of the injection well are not precisely aligned with the sandstone perforated and fractured in the horizontal well section, the water injection efficiency will be reduced or even ineffective, failing to effectively replenish the horizontal well's energy. This is the main reason why horizontal wells experience significant declines in production after commissioning, gradually becoming low-yielding wells. In actual development practice, however, geological stratification is not refined down to the level of individual sand bodies. The perforated sections of the injection wells are often located in small vertically favorable zones, rather than precisely aligned with the horizontal well sections. This results in a significant injection-production mismatch, leading to a decrease in formation energy and production.

[0005] In summary, a clear understanding of the precise injection-production relationship between water injection wells and horizontal wells is crucial. It is fundamental and crucial for injecting water, replenishing energy, and maintaining high production in horizontal wells. Poor precise injection-production correspondence is also one of the main reasons for rapid production decline and low production after commissioning horizontal wells. However, previous research on this precise injection-production relationship has been limited, and no corresponding methods for managing low-yield wells exist. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a low-yield horizontal well treatment method based on fine injection and production.

[0007] The present invention provides a method for treating low-yield horizontal wells based on fine injection and production, comprising the following steps:

[0008] 1) Finely divide the multi-layer sedimentary superimposed sandstones where the target layer of the horizontal section of the horizontal well is located, down to the level of single sand bodies;

[0009] 2) Based on 1), a comparative diagram of the sand body profiles of the horizontal wells and injection wells in the horizontal well group is established;

[0010] 3) Based on the comparison diagram of the sand body sections of the horizontal wells and water injection wells in the horizontal well group established in 2), the injection-production correspondence of the well section was determined, and research on the fine injection-production correspondence was conducted to analyze and evaluate the corresponding relationship. The perforation and fracturing sections of the horizontal wells and the perforation sections of the water injection wells were added to perform qualitative and quantitative analysis to determine the three-dimensional injection-production correspondence. The results were observed to determine whether the fracturing sections of the horizontal wells corresponded to the perforation sections of the water wells.

[0011] ①Analyze and evaluate the corresponding conditions of static injection and production

[0012] The number of water injection wells in the horizontal well group is N, where N is a natural number. From the heel to the toe of the horizontal section of the horizontal well, with the single sand body where the horizontal well trajectory is located as the target, analyze and determine whether all water injection wells in the horizontal well group have this single sand body. If so, the water injection well is considered to correspond to the static injection-production of the horizontal well. Otherwise, they are not. The number of water injection wells with this single sand body is Nj, where Nj is a natural number. The static injection-production correspondence rate of the horizontal well group is Nj / N.

[0013] ②Analyze and evaluate the dynamic injection-production correspondence

[0014] The number of water injection wells in a horizontal well group is N, where N is a natural number. From the heel to the toe of the horizontal section of the horizontal well, with the perforation and fracturing section of the single sand body where the horizontal well trajectory is located as the target, analyze and determine whether the single sand body where all water injection wells in the horizontal well group are perforated and fractured. If the single sand body where the water injection well is located has been perforated and fractured, it is considered that the water injection well corresponds to the dynamic injection and production of the horizontal well; otherwise, it does not correspond. The number of water injection wells perforated and fractured in the single sand body where the water injection well is located, Nd, is counted, and the dynamic injection and production correspondence rate of the well group is Nd / N;

[0015] ③Analysis and evaluation of the degree of perfection of injection-production correspondence in well groups

[0016] The degree of injection-production correspondence of a well group is the ratio of the static injection-production correspondence rate of the horizontal well group to the dynamic injection-production correspondence rate of the well group, D = Nd / Nj. If D = 100%, the horizontal well group has a perfect injection-production correspondence. If D < 100%, the injection-production correspondence of the horizontal well group is not perfect, and water injection needs to be carried out on the single sand body corresponding to the perforation of the water injection well.

[0017] 4) Based on the causes of low production, classify and determine the treatment methods and measures for horizontal well groups

[0018] Based on the injection-production correspondence, the following four main reasons can explain the gradual decline in production of a horizontal well group after it is put into production: 1. Incomplete injection-production well network, lack of water injection wells; 2. Poor dynamic injection-production correspondence, lack of water injection direction; 3. Low water injection intensity, resulting in an imbalance between injection and production; 4. High water injection intensity in some water injection wells, resulting in unidirectional or multidirectional water flooding. Determine the reasons for the low production of the target horizontal well group and develop corresponding treatment methods and measures:

[0019] 1. If the target horizontal well group has an incomplete injection-production well network, the injection-production well network will be improved by adding water injection wells;

[0020] 2. If static correspondence is achieved, but the horizontal layer corresponding to the water injection well is not perforated and fractured, resulting in poor dynamic injection-production correspondence, which makes it impossible to replenish energy for the horizontal well, making the horizontal well ineffective and the production declining, then it is necessary to determine the water injection well replenishment measures to improve the injection-production correspondence;

[0021] 3. If, under dynamic injection-production conditions, the injection wells have insufficient water injection, resulting in an imbalance between injection and production, insufficient energy replenishment of the horizontal wells, slow effectiveness of the horizontal wells, and decreased production, the injection rate needs to be increased;

[0022] 4. If, under dynamic injection-production conditions, the waterline advances due to excessive water injection in individual injection wells, rapidly flooding the corresponding section of the horizontal well and causing a decrease in horizontal well production, water control measures must be taken.

[0023] Preferably, in step 1), based on high-resolution sequence stratigraphy and reservoir architecture theory, the target horizontal well formation section is gradually divided into 24 single sand bodies in five levels of strata, namely, oil layer group, sand layer group, small layer, composite single sand body, and single genetic sand body, using the standard layer method, sedimentary cycle method, approximate thickness method, or interlayer identification method. The sequence stratigraphic unit is subdivided from three levels to eight levels; the reservoir architecture interface level is subdivided from nine levels to four levels, and the sand layer interpretation accuracy is refined to an accuracy of 1 to 3 meters.

[0024] Preferably, the method for establishing the comparative diagram of the sand body profile of the horizontal wells and the water injection wells in the horizontal well group is as follows:

[0025] ① Based on the stratification standards and workflow, well logging curves are selected to finely stratify the large set of sandstones in the target interval of the injection well around the horizontal well, and subdivide them into single channel sand bodies;

[0026] ② Draw a cross-sectional view of the sand bodies of the connected water injection wells within the horizontal well group: First, draw the water injection wells on one side of the horizontal well in the same plane according to the actual distance, and then align the deviated water injection wells. Secondly, refer to the well group location plan and connect the same layers of the water injection wells on the same side of the horizontal well from the heel end to the toe end of the horizontal section of the horizontal well. Connect single sand bodies with the same layer number within the layer. If adjacent wells do not have the same layer number, they will be treated as pinch-out. Finally, cut a cross-sectional view parallel to the horizontal section of the horizontal well on the well group location plan, and project the logging curves of the water injection well and the horizontal section of the horizontal well onto the cross-sectional view to obtain the cross-sectional view of the connected sand bodies of the two groups of water injection wells within the horizontal well group.

[0027] ③ Use the altitude-depth comparison method and the marker layer method to adjust the sand body profile of the connected injection wells in the horizontal well group. First, straighten the horizontal well and find the marker layer before the horizontal well entry window. Align it horizontally with the same marker layer of the surrounding injection wells. The marker layer refers to a set of strata with a certain thickness and stable development in the area. Then align the injection well and the horizontal well according to the altitude. By fine-tuning the altitude offset, the marker layer of the injection well and the horizontal well are aligned horizontally.

[0028] ④ Finely adjust the sand body profile of the connected water injection wells in the horizontal well group: After completing ③, place the horizontal section trajectory of the horizontal well in the sand body profile of the connected water injection wells in the two groups of horizontal well groups, observe the movement of the horizontal section trajectory of the horizontal well in the sand body, and judge the movement of the horizontal section trajectory of the horizontal well in sandstone, muddy sandstone and mudstone according to the staged fracture pressure monitored during the staged fracturing operation of the horizontal well. According to the judgment result, adjust the position of the horizontal section trajectory of the horizontal well in the sand body profile of the connected water injection wells in the horizontal well group, and obtain the comparative sand body profile of the horizontal wells and water injection wells in the horizontal well group.

[0029] The present invention divides the multi-layer sedimentary superimposed sandstones where the target layer of the horizontal section of the horizontal well is located into fine stratigraphic divisions down to the single sand body level, and then establishes a comparative cross-section of the sand bodies of the horizontal wells and water injection wells in the horizontal well group, analyzes and evaluates the fine injection-production correspondence, thereby increasing water drive reserves, promoting the effectiveness of horizontal well water injection, and increasing production; delaying water breakthrough in the horizontal well or controlling the water cut rising speed, thereby improving the recovery rate and effectively treating low-yield horizontal wells.

[0030] The present invention improves the well network and increases the water injection direction, thereby increasing the water drive reserves in that direction, increasing production, delaying the effective time, and improving the recovery rate; through layer filling measures, the injection-production correspondence on the plane is improved, and the water injection direction is increased from the layer to replenish the energy and increase the production of this section; by increasing the water injection volume, the injection and production are balanced and the effect is detailed; through water breakthrough and water control measures, the water content of the horizontal well is reduced, reducing pollution to the non-water breakthrough section, and restoring the horizontal well production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 In the embodiment, the length of the well P is 61 1 Comprehensive diagram of fine division of single sand body.

[0032] Figure 2 1 is a comparison diagram of the sand body profiles of the horizontal wells and the water injection well EFG in the horizontal well group in the embodiment.

[0033] Figure 3 Schematic diagram of the horizontal well group location in the embodiment.

[0034] Figure 4 Schematic diagram of the alignment of standard layers of a horizontal well group in the embodiment.

[0035] Figure 5 1 is a comparison diagram of the sand body profiles of the horizontal well w and the water injection well EFG in the horizontal well group in the embodiment.

[0036] Figure 6 3 is a comparison diagram of the sand body profile of the horizontal well w and the water injection well HJ in the horizontal well group in the embodiment.

[0037] Figure 7 This is a comparison diagram of the corresponding relationship of water injection on the west side of horizontal well w in the embodiment.

[0038] Figure 8 This is a comparison diagram of the corresponding relationship of water injection on the east side of horizontal well w in the embodiment.

[0039] Figure 9 This is a schematic diagram of the well group well location plan.

[0040] Figure 10 This is the injection-production response curve of oil well A.

[0041] Figure 11 is the injection-production response curve of horizontal well B.

[0042] Figure 7 、 Figure 8 middle This is the perforation section of the water injection well; This is the horizontal well fracturing section. DETAILED DESCRIPTION

[0043] The present invention provides a method for treating low-yield horizontal wells based on fine injection and production, comprising the following steps:

[0044] 1) Finely divide the multi-layer sedimentary superimposed sandstones where the target layer of the horizontal section of the horizontal well is located, down to the level of single sand bodies;

[0045] 2) Based on 1), a comparative diagram of the sand body profiles of the horizontal wells and injection wells in the horizontal well group is established;

[0046] 3) Based on the comparison diagram of the sand body sections of the horizontal wells and water injection wells in the horizontal well group established in 2), the injection-production correspondence of the well section was determined, and research on the fine injection-production correspondence was conducted to analyze and evaluate the corresponding relationship. The perforation and fracturing sections of the horizontal wells and the perforation sections of the water injection wells were added to perform qualitative and quantitative analysis to determine the three-dimensional injection-production correspondence. The results were observed to determine whether the fracturing sections of the horizontal wells corresponded to the perforation sections of the water wells.

[0047] ①Analyze and evaluate the corresponding conditions of static injection and production

[0048] The number of water injection wells in the horizontal well group is N, where N is a natural number. From the heel to the toe of the horizontal section of the horizontal well, with the single sand body where the horizontal well trajectory is located as the target, analyze and determine whether all water injection wells in the horizontal well group have this single sand body. If so, the water injection well is considered to correspond to the static injection-production of the horizontal well. Otherwise, they are not. The number of water injection wells with this single sand body is Nj, where Nj is a natural number. The static injection-production correspondence rate of the horizontal well group is Nj / N.

[0049] ②Analyze and evaluate the dynamic injection-production correspondence

[0050] The number of water injection wells in a horizontal well group is N, where N is a natural number. From the heel to the toe of the horizontal section of the horizontal well, with the perforation and fracturing section of the single sand body where the horizontal well trajectory is located as the target, analyze and determine whether the single sand body where all water injection wells in the horizontal well group are perforated and fractured. If the single sand body where the water injection well is located has been perforated and fractured, it is considered that the water injection well corresponds to the dynamic injection and production of the horizontal well; otherwise, it does not correspond. The number of water injection wells perforated and fractured in the single sand body where the water injection well is located, Nd, is counted, and the dynamic injection and production correspondence rate of the well group is Nd / N;

[0051] ③Analysis and evaluation of the degree of perfection of injection-production correspondence in well groups

[0052] The degree of injection-production correspondence of a well group is the ratio of the static injection-production correspondence rate of the horizontal well group to the dynamic injection-production correspondence rate of the well group, D = Nd / Nj. If D = 100%, the horizontal well group has a perfect injection-production correspondence. If D < 100%, the injection-production correspondence of the horizontal well group is not perfect, and water injection needs to be carried out on the single sand body corresponding to the perforation of the water injection well.

[0053] 4) Based on the causes of low production, classify and determine the treatment methods and measures for horizontal well groups

[0054] Based on the injection-production correspondence, the following four main reasons can explain the gradual decline in production of a horizontal well group after it is put into production: 1. Incomplete injection-production well network, lack of water injection wells; 2. Poor dynamic injection-production correspondence, lack of water injection direction; 3. Low water injection intensity, resulting in an imbalance between injection and production; 4. High water injection intensity in some water injection wells, resulting in unidirectional or multidirectional water flooding. Determine the reasons for the low production of the target horizontal well group and develop corresponding treatment methods and measures:

[0055] 1. If the target horizontal well group has an incomplete injection-production well network, the injection-production well network will be improved by adding water injection wells;

[0056] 2. If static correspondence is achieved, but the horizontal layer corresponding to the water injection well is not perforated and fractured, resulting in poor dynamic injection-production correspondence, which makes it impossible to replenish energy for the horizontal well, making the horizontal well ineffective and the production declining, then it is necessary to determine the water injection well replenishment measures to improve the injection-production correspondence;

[0057] 3. If, under dynamic injection-production conditions, the injection wells have insufficient water injection, resulting in an imbalance between injection and production, insufficient energy replenishment of the horizontal wells, slow effectiveness of the horizontal wells, and decreased production, the injection rate needs to be increased;

[0058] 4. If, under dynamic injection-production conditions, the waterline advances due to excessive water injection in individual injection wells, rapidly flooding the corresponding section of the horizontal well and causing a decrease in horizontal well production, water control measures must be taken.

[0059] In step 1), based on high-resolution sequence stratigraphy and reservoir architecture theory, the target horizontal well stratigraphic section is gradually divided into five levels of strata, namely, oil layer group, sand layer group, small layer, composite single sand body, and single genetic sand body, with 24 single sand bodies, using the standard layer method, sedimentary cycle method, approximate thickness method, or interlayer identification method. The sequence stratigraphic unit is subdivided from three to eight levels; the reservoir architecture interface level is subdivided from nine to four levels, and the sand layer interpretation accuracy is refined to 1 to 3 meters.

[0060] The method for establishing the comparative diagram of the sand body profile of the horizontal wells and water injection wells in the horizontal well group is as follows:

[0061] ① According to the stratification standards and workflow, well logging curves such as gamma, natural potential, and acoustic transit time are selected to accurately align the layers; the large set of sandstones in the target interval of the injection well surrounding the horizontal well is finely stratified geologically and subdivided into single channel sand bodies;

[0062] ② Draw a cross-sectional view of the sand bodies of the connected water injection wells within the horizontal well group: First, draw the water injection wells on one side of the horizontal well in the same plane according to the actual distance, and then align the deviated water injection wells. Secondly, refer to the well group location plan and connect the same layers of the water injection wells on the same side of the horizontal well from the heel end to the toe end of the horizontal section of the horizontal well. Connect single sand bodies with the same layer number within the layer. If adjacent wells do not have the same layer number, they will be treated as pinch-out. Finally, cut a cross-sectional view parallel to the horizontal section of the horizontal well on the well group location plan, and project the logging curves of the water injection well and the horizontal section of the horizontal well onto the cross-sectional view to obtain the cross-sectional view of the connected sand bodies of the two groups of water injection wells within the horizontal well group.

[0063] ③ Use the altitude-depth comparison method and the marker layer method to adjust the sand body profile of the connected injection wells in the horizontal well group. First, straighten the horizontal well and find the marker layer before the horizontal well entry window. Align it horizontally with the same marker layer of the surrounding injection wells. The marker layer refers to a set of strata with a certain thickness and stable development in the area. Then align the injection well and the horizontal well according to the altitude. By fine-tuning the altitude offset, the marker layer of the injection well and the horizontal well are aligned horizontally.

[0064] ④ Finely adjust the sand body profile of the connected water injection wells in the horizontal well group: After completing ③, place the horizontal section trajectory of the horizontal well in the sand body profile of the connected water injection wells in the two groups of horizontal well groups, observe the movement of the horizontal section trajectory of the horizontal well in the sand body, and judge the movement of the horizontal section trajectory of the horizontal well in sandstone, muddy sandstone and mudstone according to the staged fracture pressure monitored during the staged fracturing operation of the horizontal well. According to the judgment result, adjust the position of the horizontal section trajectory of the horizontal well in the sand body profile of the connected water injection wells in the horizontal well group, and obtain the comparative sand body profile of the horizontal wells and water injection wells in the horizontal well group. Example

[0065] The multiple layers of sedimentary superimposed sandstone are finely divided into stratigraphic divisions down to the level of single sand bodies.

[0066] Thin interlayers exist within multi-layered sedimentary sandstone reservoirs, including mudstone, calcareous, and physical interlayers, interbedded with sandstone. This is illustrated by the Chang 6 reservoir in the Triassic Yanchang Formation in the Ordos Basin. The Chang 6 reservoir is a typical multi-layered sedimentary sandstone formation, primarily composed of interbedded fine-grained sandstone, siltstone, and black mudstone, interbedded with black carbonaceous mudstone. This formation is primarily deltaic progradational, with a high sand content, making it one of the best reservoir intervals in the basin.

[0067] Based on high-resolution sequence stratigraphy and reservoir architecture theory, the Chang 6 oil layer group, with a thickness of 110~120m, was gradually divided into 24 single sand bodies in five levels of strata, namely oil layer group, sand layer group, small layer, composite single sand body, and single genetic sand body, using working methods such as standard layer method, sedimentary cycle method, approximate thickness method, and interlayer identification method. The sequence stratigraphic unit was subdivided from three levels to eight levels; the reservoir architecture interface level was subdivided from nine levels to four levels, and the sand layer interpretation accuracy was refined to 1 meter to 3 meters.

[0068] The detailed division method of the Chang 6 stratigraphic section is as follows:

[0069] Identify and divide the third-level system tract, namely the Chang 6 stratigraphic section: use the K1 and K2 standard layers to determine the bottom of the Chang 6 oil layer group, and use the K4 and B2 standard layers to determine the top of the Chang 6 oil layer group.

[0070] ② Identify and divide the four-level parasequence, namely the Chang 6 reservoir oil layer group: Using the standard layers B3, K3 and B5, the Chang 6 formation section can be divided into four oil layer groups, namely Chang 61, Chang 62, Chang 63 and Chang 64.

[0071] ③ Identify and divide the fifth-level medium-term base level and the sixth-level ultra-high frequency anomaly cycle, namely the sand layer group and sub-layer of Chang 6 reservoir: by comprehensively applying the sedimentary cycle method, standard layer method, formation thickness method and closure tracking of adjacent wells, a single oil layer group can be subdivided into two sand layer groups, and Chang 61 can be divided into two sand layer groups according to actual needs. 1 ~62cm long 1 The three sand layers are further divided into long 61 1-1 , length 61 1-2 , length 61 2-1 , length 61 2-2 Length 62 1-1 and length 62 1-2 .

[0072] ④ Identification and classification of single sand bodies in the Chang 6 reservoir: Single sand bodies can be divided into composite single sand bodies and single genetic sand bodies. The identification marks for single sand bodies are mainly divided into vertical identification marks and horizontal identification marks, which are determined by the identification of interface characteristics and interlayers. The results of stratigraphic division are shown in Table 1:

[0073] Table 1 Results of fine stratigraphic division of Chang 6 reservoir

[0074] .

[0075] 2) Establishing a horizontal well group profile

[0076] ① According to the stratification standards and work flow, the large set of sandstones where the target interval of the water injection well around the horizontal well is located is finely stratified into single channel sand bodies, and key logging curves such as gamma, natural potential, acoustic time difference, and resistance are selected. Figure 1 In the P well, the Chang 61-1 sand layer group was finely divided into 6 single sand bodies, which are Chang 61- 1-1-1 、61- 1-1-2 、61- 1-1-3 、61- 1-1-4 、61- 1-1-5 、61- 1-1-6 For the convenience of description, the following text is simplified as single sand bodies No. 1-6;

[0077] ② Draw the cross-section of the connected sand bodies of the injection wells in the horizontal well group. Taking the seven-point method area injection and production well network as an example, first straighten the conventional wells in the cross-section, then refer to the well group well location map, and follow the direction from point A to point B in the horizontal section. Connect the three injection wells on each side of the horizontal well in the same layer of the injection wells in turn, and connect the single sand bodies with the same layer number within the layer. If the adjacent wells do not have the same layer number, it will be treated as pinch-out. Figure 2 Finally, a section parallel to the horizontal section of the horizontal well is cut on the well location plan, as shown in the figure below: Figure 3 As shown in the figure, the well logging curves of the injection well and the horizontal section of the horizontal well are projected onto the section;

[0078] ③ Use the altitude-depth comparison method and the marker layer method to adjust the sand body profile of the well connection. Due to geological tectonic movement, the strata have an inclination, so it is necessary to adjust the horizontal well altitude offset to align the sand bodies of the horizontal well and the injection well with the same layer number. In the alignment process, the horizontal well must be straightened first, and the key marker layer in the area before the horizontal well enters the window must be found to align it horizontally with the same marker layer of the surrounding injection wells. Figure 4 The marker layer of the mid-level horizontal well, Well W, is a typical tuff. The well logging characteristics of the marker layer are low gamma, low natural potential, and high acoustic transit time. Secondly, the injection well and the horizontal well are aligned according to their altitude. By fine-tuning the altitude offset, the marker layers of the injection well and the horizontal well are aligned horizontally.

[0079] ④ Finely adjust the well connection profile. After completing ③, place the horizontal segment trajectory in the two groups of water injection well connection profiles to observe its movement in the sand body. Use the segmented fracture pressure monitored by the horizontal well staged fracturing operation to assist in judging the movement of the horizontal segment trajectory in sandstone, argillaceous sandstone, and mudstone. Due to compaction, mudstone is dense and has low porosity, so its fracture pressure value is high; the opposite is true for sandstone. Figure 5 The fracture pressure at point Q is relatively low, at 36.5 MPa, and is adjusted to penetrate sandstone; the fracture pressure at point P is relatively high, at 47.8 MPa, and is adjusted to penetrate mudstone. Follow the same steps to complete the detailed comparison diagram of the well cross section on the other side of the horizontal well, as shown in the figure below. Figure 6 shown.

[0080] 3) Analyze and evaluate the precise injection-production correspondence

[0081] Add the perforation and fracturing sections of the horizontal well and the perforation sections of the water injection well to qualitatively and quantitatively analyze the three-dimensional injection-production correspondence and observe whether the fracturing section of the horizontal well corresponds to the injection-production of the perforation section of the water well:

[0082] ①Analyze and evaluate the corresponding conditions of static injection and production

[0083] The number of injection wells in the well group is N. From point A to point B in the horizontal section, with the single sand body where the horizontal wellbore trajectory is located as the target, analyze and determine whether all injection wells in the well group have this single sand body. If so, it is considered to correspond to the static injection and production of the horizontal well. Otherwise, it does not correspond. The number of injection wells with this single sand body, Nj, is counted. The static injection and production correspondence rate of the well group is Nj / N. The closer the static injection and production correspondence rate of the well group is to 1, the better.

[0084] ②Analyze and evaluate the dynamic injection-production correspondence

[0085] From point A to point B in the horizontal section, take the perforation and fracturing section of the single sand body where the horizontal wellbore trajectory is located as the target, analyze and determine whether the single sand body of all water injection wells in the well group is perforated and fractured. If it is perforated, it is considered to correspond to the dynamic injection and production of the horizontal well; otherwise, it is not. Count the number of water injection wells Nd that perforate the single sand body, and the dynamic injection and production correspondence rate of the well group is Nd / N. The closer the dynamic injection and production correspondence rate of the well group is to 1, the better.

[0086] ③ Analysis and evaluation of the degree of perfection of injection-production correspondence in well groups

[0087] The degree of correspondence between the injection and production of the well group is the static correspondence ratio of the well group to the single sand body perforation. D = Nd / Nj. The larger D is, the better. D = 100% indicates that the well group has a perfect correspondence between injection and production. D < 100% indicates that the correspondence between the injection and production of the well group is not perfect and it is necessary to inject water into the single sand body corresponding to the perforation of the injection well.

[0088] exist Figure 7 , Figure 8In the example, horizontal well W is perforated and fractured throughout layer 2, while injection wells E and F are perforated in layers 3 and 5. If the artificial fractures in the horizontal well fail to penetrate the interlayer between layers 2 and 3 after fracturing, then the two injection wells, E and F, will not be accurately dynamically aligned with the horizontal well. Injection well G is perforated in layers 2 and 5, with layer 2 dynamically aligned with the horizontal well. Injection wells H and J are perforated in layer 2, dynamically aligned with the horizontal well. The static correspondence rate for the well group is 100%, the dynamic correspondence rate is 60%, and the injection-production correspondence level (D) for the well group is 60%. This indicates that the injection-production correspondence in this well group is incomplete, and water injection is needed to address the single yarn body corresponding to the perforation of the injection well supplementary layer.

[0089] 4) Classify and determine horizontal well management methods and measures based on the causes of low production

[0090] Based on the injection-production correspondence, the main reasons for the gradual decrease in production of horizontal wells after commissioning are the following four situations: ① Incomplete injection-production well network and lack of water injection wells; ② Poor dynamic injection-production correspondence and lack of water injection direction; ③ Low water injection intensity and imbalance between injection and production; ④ High water injection intensity in some water injection wells, resulting in unidirectional or multidirectional flooding.

[0091] In response to the above four reasons, corresponding treatment methods and measures are formulated respectively:

[0092] ① For well groups with incomplete well patterns, improve the injection-production well pattern by adding water injection wells;

[0093] Compared with the seven-point method of direct injection and horizontal production well pattern, if there is a lack of water injection wells, the seven-point method of area well pattern can be formed by changing the injection wells or drilling new water injection wells. Figure 9 , the water injection wells K and E are missing, and it is necessary to form a complete seven-point injection-production well network by re-injection or drilling new water injection wells;

[0094] For well groups with incomplete injection-production correspondence, determine water injection well supplementation measures to improve the injection-production correspondence;

[0095] For an imperfect well group corresponding to injection and production, that is, when D < 100%, find the static corresponding single sand body of the injection well and implement layer filling measures to make the perfection degree D reach 100%;

[0096] like Figure 7 、 8 Horizontal well W is perforated and fractured in layer 2, while the perforation section of water injection wells E and F is layer 5. The dynamic injection and production do not correspond. Layer 2 of water injection wells E and F needs to be perforated and water injected to improve the dynamic injection and production correspondence rate.

[0097] For well groups with low production due to ineffective water injection and perfect injection-production correspondence, it is necessary to reasonably increase injection allocation;

[0098] For the purpose of improving the well group corresponding to injection and production, that is, D=100%, if water injection is still ineffective for more than one year, the formation energy and single well production can be restored by gradually increasing the injection well allocation and increasing the injection volume, such as Figure 10 , the water injection intensity of well A1 is low. By increasing the water injection intensity, horizontal well A slowly takes effect at time point T1;

[0099] For well groups with perfect injection-production correspondence but low production due to water seepage after water injection, water control measures should be taken;

[0100] The direction of water breakthrough is determined by analyzing the distance between the injection and production wells and the amount of water injection. For wells with doubts about the direction of water breakthrough, the direction of water breakthrough can be verified by stopping injection and observing the changes in water content in the horizontal wells. For injection wells with confirmed water breakthrough directions, measures such as stopping injection, periodic water injection with small water volumes, and profile adjustment can be implemented to control the water content of the horizontal wells and stabilize their production. Figure 11 After a period of production, the water cut in horizontal well B gradually increased from 21% to approximately 50%. Analysis of the injection-production well spacing (i.e., the vertical distance between horizontal well B and injection well B1) and the injection-production response curve indicated that the horizontal well received the injected water from injection well B1. By reducing the injection rate of injection well B1, the water cut in horizontal well B gradually decreased, while monthly oil production steadily increased.

Claims

1. A method for treating low-yield horizontal wells based on fine injection and production, characterized in that: The following steps are involved: 1) Finely divide the multi-layer sedimentary superimposed sandstones where the target layer of the horizontal section of the horizontal well is located, down to the level of single sand bodies; 2) Based on 1), a comparative diagram of the sand body profiles of the horizontal wells and injection wells within the horizontal well group is established; 3) Based on the comparison diagram of the sand body sections of the horizontal wells and water injection wells within the horizontal well group established in 2), the injection-production correspondence of the well section is determined, and research on the detailed injection-production correspondence is conducted. The perforation and fracturing sections of the horizontal wells and the perforation sections of the water injection wells are added to qualitatively and quantitatively analyze and determine the three-dimensional injection-production correspondence. The results are then analyzed to see whether the fracturing sections of the horizontal wells correspond to the perforation sections of the water wells. ①Analyze and evaluate the corresponding conditions of static injection and production The number of water injection wells in the horizontal well group is N, where N is a natural number. From the heel to the toe of the horizontal section of the horizontal well, with the single sand body where the horizontal well trajectory is located as the target, analyze and determine whether all water injection wells in the horizontal well group have this single sand body. If so, the water injection well is considered to correspond to the static injection-production of the horizontal well. Otherwise, they are not. The number of water injection wells with this single sand body is Nj, where Nj is a natural number. The static injection-production correspondence rate of the horizontal well group is Nj / N. ②Analyze and evaluate the dynamic injection-production correspondence The number of water injection wells in a horizontal well group is N, where N is a natural number. From the heel to the toe of the horizontal section of the horizontal well, with the perforation and fracturing section of the single sand body where the horizontal well trajectory is located as the target, analyze and determine whether the single sand body where all water injection wells in the horizontal well group are perforated and fractured. If the single sand body where the water injection well is located has been perforated and fractured, it is considered that the water injection well corresponds to the dynamic injection and production of the horizontal well; otherwise, it does not correspond. The number of water injection wells perforated and fractured in the single sand body where the water injection well is located, Nd, is counted, and the dynamic injection and production correspondence rate of the well group is Nd / N; ③Analysis and evaluation of the degree of perfection of injection-production correspondence in well groups The degree of injection-production correspondence of a well group is the ratio of the static injection-production correspondence rate of the horizontal well group to the dynamic injection-production correspondence rate of the well group, D = Nd / Nj. If D = 100%, the horizontal well group has a perfect injection-production correspondence. If D < 100%, the injection-production correspondence of the horizontal well group is not perfect, and water injection needs to be carried out on the single sand body corresponding to the perforation of the water injection well. 4) Based on the causes of low production, classify and determine the treatment methods and measures for horizontal well groups Based on the injection-production correspondence, the following four main reasons can explain the gradual decline in production of a horizontal well group after it is put into production:

1. Incomplete injection-production well network, lack of water injection wells; 2. Poor dynamic injection-production correspondence, lack of water injection direction; 3. Low water injection intensity, resulting in an imbalance between injection and production; 4. High water injection intensity in some water injection wells, resulting in unidirectional or multidirectional water flooding. Determine the reasons for the low production of the target horizontal well group and develop corresponding treatment methods and measures:

1. If the target horizontal well group has an incomplete injection-production well network, the injection-production well network will be improved by adding water injection wells; 2. If static correspondence is achieved, but the horizontal layer corresponding to the water injection well is not perforated and fractured, resulting in poor dynamic injection-production correspondence, which makes it impossible to replenish energy for the horizontal well, making the horizontal well ineffective and the production declining, then it is necessary to determine the water injection well replenishment measures to improve the injection-production correspondence; 3. If, under dynamic injection-production conditions, the injection wells have insufficient water injection, resulting in an imbalance between injection and production, insufficient energy replenishment of the horizontal wells, slow effectiveness of the horizontal wells, and decreased production, the injection rate needs to be increased; 4. If, under dynamic injection-production conditions, the waterline advances due to excessive water injection in individual injection wells, rapidly flooding the corresponding section of the horizontal well and causing a decrease in horizontal well production, water control measures must be taken.

2. A method for treating low-yield horizontal wells based on fine injection and production according to claim 1, characterized in that: In step 1), based on high-resolution sequence stratigraphy and reservoir architecture theory, the target horizontal well stratigraphic section is gradually divided into five levels of strata, namely, oil layer group, sand layer group, small layer, composite single sand body, and single genetic sand body, with 24 single sand bodies, using the standard layer method, sedimentary cycle method, approximate thickness method, or interlayer identification method. The sequence stratigraphic unit is subdivided from three to eight levels; the reservoir architecture interface level is subdivided from nine to four levels, and the sand layer interpretation accuracy is refined to 1 to 3 meters.

3. A method for treating low-yield horizontal wells based on fine injection and production as claimed in claim 2, characterized in that: The method for establishing the comparative diagram of the sand body profile of the horizontal wells and the water injection wells in the horizontal well group is as follows: ① Based on the stratification standards and workflow, well logging curves are selected to finely stratify the large set of sandstones in the target interval of the water injection well around the horizontal well, and subdivide them into single channel sand bodies; ② Draw a cross-sectional view of the sand bodies of the connected water injection wells within the horizontal well group: First, draw the water injection wells on one side of the horizontal well in the same plane according to the actual distance, and then align the deviated water injection wells. Secondly, refer to the well group location plan and connect the same layers of the water injection wells on the same side of the horizontal well from the heel end to the toe end of the horizontal section of the horizontal well. Connect single sand bodies with the same layer number within the layer. If adjacent wells do not have the same layer number, they will be treated as pinch-out. Finally, cut a cross-sectional view parallel to the horizontal section of the horizontal well on the well group location plan, and project the logging curves of the water injection well and the horizontal section of the horizontal well onto the cross-sectional view to obtain the cross-sectional view of the connected sand bodies of the two groups of water injection wells within the horizontal well group. ③ Use the altitude-depth comparison method and the marker layer method to adjust the sand body profile of the connected injection wells in the horizontal well group. First, straighten the horizontal well and find the marker layer before the horizontal well entry window. Align it horizontally with the same marker layer of the surrounding injection wells. The marker layer refers to a set of strata with a certain thickness and stable development in the area. Then align the injection well and the horizontal well according to the altitude. By fine-tuning the altitude offset, the marker layer of the injection well and the horizontal well are aligned horizontally. ④ Finely adjust the sand body profile of the connected water injection wells in the horizontal well group: After completing ③, place the horizontal section trajectory of the horizontal well in the sand body profile of the connected water injection wells in the two groups of horizontal well groups, observe the movement of the horizontal section trajectory of the horizontal well in the sand body, and judge the movement of the horizontal section trajectory of the horizontal well in sandstone, muddy sandstone and mudstone according to the staged fracture pressure monitored during the staged fracturing operation of the horizontal well. According to the judgment result, adjust the position of the horizontal section trajectory of the horizontal well in the sand body profile of the connected water injection wells in the horizontal well group, and obtain the comparative sand body profile of the horizontal wells and water injection wells in the horizontal well group.

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