Horizontal well spacing method based on fracture development strength characteristics

Abstract

The invention discloses a horizontal well spacing method based on fracture development strength characteristics. The horizontal well spacing method comprises the steps that firstly, a reservoir fracture development degree and strength model is established; 2, establishing a classification standard of reservoir fracture development degrees; thirdly, a development mode is selected according to fracture development strength classification, long horizontal well quasi-natural energy development is adopted in a first-class fracture strength area, and rectangular well pattern advanced water injection development is adopted in a second-class fracture strength area and a third-class fracture strength area; and 4, determining a water injection development mode, wherein different modes are adopted for heat exchange of the second-class crack strength region and the third-class crack strength region. The method has the advantages that natural fracture orientation identification based on logging is carried out, a fracture development degree classification standard based on logging parameters is constructed, different horizontal well spacing modes are formulated according to different fracture strength classification, horizontal well pattern parameters are optimized, the adaptability of a horizontal well pattern reservoir is improved, and finally the aims of improving the water flooding effect, reducing the water breakthrough risk and achieving efficient development are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield development, and in particular relates to a horizontal well arrangement method based on fracture development intensity characteristics. Background Art

[0002] In recent years, with the deepening of oil field development, the production targets of new areas have gradually shifted from low permeability and extra-low permeability reservoirs to ultra-low permeability and tight oil reservoirs. At present, horizontal well development is mainly based on ultra-permeability and tight oil reservoirs. Horizontal wells have become the main technical means to increase the single well production of such reservoirs in the early stage. The horizontal well water injection development of ultra-low permeability reservoirs has the problem of adaptability between the well network and the fractures, which leads to water easy to see when put into production, low degree of effectiveness, large decline, low oil production rate and other problems.

[0003] Domestic scholars' research on the development law and well pattern of fractured horizontal wells mainly focuses on the productivity research of horizontal well-vertical well network. There are few studies on the law of production decline and water content increase of low permeability horizontal wells. Conventional medium and high permeability reservoir prediction methods are still used or partially improved, which has poor adaptability. In terms of formation energy supplement, based on conventional water drive, advanced water injection and mild water injection technologies have been developed. However, there are still problems such as insufficient energy supplement, poor water drive effect and easy water jump in the development of horizontal wells, and it is difficult to adjust the horizontal well development in the later stage. Summary of the invention

[0004] The purpose of the present invention is to provide a horizontal well layout method based on the fracture development intensity characteristics. According to the fracture development intensity, different well layout methods are adopted to improve the adaptability of the horizontal well pattern and the fractures, ultimately improving the water drive effect and reducing the risk of water breakthrough.

[0005] The object of the present invention is achieved by the following technical means, a horizontal well layout method based on fracture development intensity characteristics, comprising the following steps:

[0006] The first step is to establish a reservoir fracture development intensity model to calculate the sand layer fracture intensity SFI and the intra-layer fracture intensity FFI;

[0007] The second step is to establish the classification standard of reservoir fracture development degree. According to the production dynamic data, SFI and FFI values, the relationship curve between the production dynamic data and the SFI or FFI value is drawn by the intersection diagram method. The relationship curve is a trend line summarized by scatter points. The trend line is obtained by the curve tangent intersection method to obtain the dividing points A and B. The horizontal coordinate values ​​of A and B are the specific dividing values. Among them, the horizontal coordinate A is less than the horizontal coordinate B, and the SFI or FFI value is less than the horizontal coordinate A, which is the third category, the horizontal coordinate greater than or equal to the horizontal coordinate A to less than or equal to the horizontal coordinate B, which is the second category, and the horizontal coordinate greater than the horizontal coordinate B is the first category; when there is only one body segment with fracture development in the reservoir, the SFI is used as the horizontal coordinate, and when there are multiple body segments with fracture development in the reservoir, the FFI is used as the horizontal coordinate;

[0008] Step 3: Select the development method based on the intensity of fracture development. For areas with the first type of fracture intensity, long horizontal wells and quasi-natural energy development are used. For areas with the second and third types of fracture intensity, rectangular well pattern advanced water injection development is used.

[0009] Step 4: Determine the water injection development method.

[0010] For the second type of fracture intensity area, the coupling degree between the natural fractures, artificial fractures and the principal stress direction in the block is calculated based on the imaging logging data. When the coupling degree is higher than 85%, the horizontal well orientation is perpendicular to the principal stress direction; when the coupling degree is lower than 85%, the horizontal well orientation is perpendicular to the natural fracture angle.

[0011] For the third type of fracture intensity area, the horizontal well orientation is perpendicular to the principal stress direction.

[0012] The coupling degree refers to the proportion of the number of cracks within the safe angle range among the natural cracks and artificial cracks to the total number of cracks.

[0013] The safety angle range is between δ-α and δ+α, where δ-α is the minimum safety angle, δ+α is the maximum safety angle, α is the angle between the injection well and the horizontal well, and δ is the maximum principal stress direction angle.

[0014] Said Where L is the thickness of the sand body section, i1 is the top depth of the i-th fracture development section in the sand body section, i2 is the bottom depth of the i-th fracture development section in the sand body section, and FIP(x) is the fracture index parameter value at depth x.

[0015] Said L i is the thickness of the i-th sand body segment, i1 is the top depth of the i-th fracture development segment of the k-th sand body segment, i2 is the bottom depth of the i-th fracture development segment of the k-th sand body segment, and FIP(x) is the fracture index parameter value at depth x.

[0016] The beneficial effects of the present invention are: based on the identification of the orientation of natural fractures by logging, a classification standard for the degree of fracture development based on logging parameters is constructed, different horizontal well layout methods are formulated according to different fracture intensity classifications, the horizontal well network parameters are optimized, and the adaptability of the horizontal well network reservoir is improved, ultimately improving the effectiveness of water flooding, reducing the risk of water breakthrough, and achieving the goal of efficient development. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of the horizontal well layout method based on the fracture development intensity characteristics;

[0018] Figure 2 Schematic diagram of crack strength and intra-layer crack strength;

[0019] Figure 3 This is a classification map based on FFI and monthly liquid production in the Huaqingmaling area;

[0020] Figure 4 This is a schematic diagram of the safe angle range;

[0021] Figure 5 This is a statistical table of fracture development degree and coupling characteristics in Class III blocks;

[0022] Figure 6 This is the statistical diagram of natural fracture angle distribution of imaging logging in L183 area;

[0023] Figure 7 This is the statistical diagram of the natural fracture angle distribution of imaging logging in the S183 area;

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0025] [Example 1]

[0026] like Figure 1 As shown, a horizontal well layout method based on fracture development intensity characteristics includes the following steps:

[0027] The first step is to establish a reservoir fracture development intensity model to calculate the fracture intensity SFI of the sand layer and the intra-layer fracture intensity FFI; the fracture intensity SFI of the sand layer is for when there is only one fracture development segment, such as Figure 2 When only the crack strength within the L1 section is calculated, SFI is used for calculation.

[0028] If there are multiple fracture development sections, such as L1 and L3, the intralayer fracture intensity FFI is used for calculation, so FFI includes SFI.

[0029] The second step is to establish the classification standard of reservoir fracture development degree. According to the production dynamic data, SFI and FFI values, the relationship curve between the production dynamic data and the SFI or FFI value is drawn by the intersection diagram method. The relationship curve is a trend line summarized by scatter points. The trend line is obtained by the curve tangent intersection method to obtain the dividing points A and B. The horizontal coordinate values ​​of A and B are the specific dividing values. Among them, the horizontal coordinate A is less than the horizontal coordinate B, and the SFI or FFI value is less than the horizontal coordinate A, which is the third category, the horizontal coordinate greater than or equal to the horizontal coordinate A to less than or equal to the horizontal coordinate B, which is the second category, and the horizontal coordinate greater than the horizontal coordinate B is the first category; when there is only one body segment with fracture development in the reservoir, the SFI is used as the horizontal coordinate, and when there are multiple body segments with fracture development in the reservoir, the FFI is used as the horizontal coordinate;

[0030] Similarly, when drawing a curve graph, if there is a single fracture development section, SFI is used as the horizontal axis; if there are multiple fracture development sections, FFI is used as the horizontal axis.

[0031] When drawing a graph, use production dynamic data, such as monthly liquid production, as the ordinate and FFI or SFI as the abscissa, mark each scattered point on the graph, and use these scattered points to draw a trend line for the monthly production scattered points, such as Figure 3 Line a and line c are the trend lines of the scattered points in Ma Ling area and Hua Qing area respectively. The conventional trend line can be divided into three sections, each of which has a different curvature and different tangents. Through the curve tangent intersection method, a tangent is drawn for each trend line. The tangents of two adjacent trend lines will intersect at one point. There will be two intersection points for the three sections, such as Figure 2 As shown, lines b and d are tangents to the trend lines in Maling area and Huaqing area respectively.

[0032] The intersection with the smaller horizontal coordinate is marked as the dividing point A, and the larger one is marked as the dividing point B. Taking the tangent line in the Maling area as an example, the horizontal coordinate of point A is 0.048, and the horizontal coordinate of point B is 0.081.

[0033] In the Maling area, FFI between 0-0.048 (excluding 0.048) is the third category, between 0.048-0.081 (including 0.048 and 0.081) is the second category, and greater than 0.081 (excluding 0.081) is the third category. The details are shown in the following table.

[0034]

[0035]

[0036] Step 3: Select the development method based on the intensity of fracture development. For areas with the first type of fracture intensity, long horizontal wells and quasi-natural energy development are used. For areas with the second and third types of fracture intensity, rectangular well pattern advanced water injection development is used.

[0037] The first type of fracture intensity area, such as the western part of the basin, is affected by the development of Indosinian and Himalayan faults, and the YC long 6 micro-fractures are developed. Although the imaging logging shows that the fracture angle is basically within the safe range, due to the development of bedding fractures and high fracture density, the water breakthrough problem is still prominent. For example, the Y31 horizontal well sees water at five points, with a large decline and poor development effect. The Y192 high-angle rectangular well pattern also has water breakthrough problems and poor development effects. Therefore, long horizontal wells are used for quasi-natural energy development of this type of reservoir.

[0038] Step 4: Determine the water injection development method.

[0039] For the second type of fracture intensity area, the coupling degree between the natural fractures, artificial fractures and the principal stress direction in the block is calculated based on the imaging logging data. When the coupling degree is higher than 85%, the horizontal well orientation is perpendicular to the principal stress direction; when the coupling degree is lower than 85%, the horizontal well orientation is perpendicular to the natural fracture angle.

[0040] For the third type of fracture intensity area, the horizontal well orientation is perpendicular to the principal stress direction. Since fractures are no longer developed in the third type of fracture intensity area, the influence of fractures does not need to be considered, and the horizontal well orientation can be directly perpendicular to the principal stress direction.

[0041] The coupling degree refers to the proportion of the number of cracks within the safe angle range among the natural cracks and artificial cracks to the total number of cracks.

[0042] like Figure 4 As shown in FIG. 1 , the safety angle range is between δ-α and δ+α, where δ-α is the minimum safety angle, δ+α is the maximum safety angle, α is the angle between the injection well and the horizontal well, and δ is the angle of the maximum principal stress direction. When the fracture orientation is between the safety angles, the risk of fracture water breakthrough is reduced.

[0043] Through outcrop profiles and imaging logging observations, the trend of natural fractures in the same area is highly consistent over a large range. However, for oil reservoirs with developed natural fractures or poor coupling between the orientation of natural fractures and ground stress, or with excessively large angles, even if the reservoir has good compressibility, good fluid properties, and uniform pore throat distribution, it will still cause premature flooding of the oil wells and affect the development effect of the reservoir. Through tracking research on horizontal well development areas with relatively developed natural fractures in Heshui areas, it is found that fracture-type water breakthrough accounts for about 20%, with an average water breakthrough period of 14 months, and it is difficult to control water breakthrough.

[0044] like Figure 5 As shown in the figure, it can be seen that the better the coupling degree between the fracture direction of natural fractures and artificial fractures and the principal stress is, the lower the proportion of water breakthrough wells is. On the contrary, the proportion of water breakthrough wells is high.

[0045] Therefore, we first count the direction, that is, the angle, of each natural and artificial fracture in the block based on the imaging logging data, and calculate the coupling degree, that is, how many fractures among all the fractures are within the safe angle range.

[0046] like Figure 6 and Figure 7 As shown in the figure, taking the S177 well area and the L83 well area as examples, the maximum principal stress direction of the L183 and S177 areas is 73.6° northeast, the angle between the injection well and the horizontal section projection is 21.8°, and the safe angle range is between 53.2° and 96.8°. The imaging logging data statistics show that nearly 20% of the fracture distribution directions in the S177 area are beyond the safe range. Field practice has proved that the proportion of fracture water breakthrough in the S177 area is indeed larger than that in the L183 area.

[0047] When the coupling degree is higher than 85%, the horizontal well orientation is perpendicular to the principal stress direction; when the coupling degree is lower than 85%, the horizontal well orientation should be perpendicular to the natural fracture angle.

[0048] like Figure 2 As shown, Where L is the thickness of the sand body section, i1 is the top depth of the i-th fracture development section of the sand body section, i2 is the bottom depth of the i-th fracture development section of the sand body section, and FIP(x) is the fracture index parameter value at depth x. The existing SFI is simply (h1+h2) / L1, that is, L1 is calculated as the thickness of the L1 sand body, h1 and h2 are the thickness of the two fracture development sections of the L1 section. L is the thickness of the terrace section, S is the fracture development intensity area, and h is the thickness of the fracture development section.

[0049] Said L i is the thickness of the i-th sand body segment, i1 is the top depth of the i-th fracture development segment of the k-th sand body segment, i2 is the bottom depth of the i-th fracture development segment of the k-th sand body segment, and FIP(x) is the fracture index parameter value at depth x. The existing FFI is (h1+h2+h3) / (L1+L3), that is, the sum of the thickness of the three fracture development segments in the L1 and L3 segments is divided by the sum of the thickness of the two sand body segments.

[0050] Specifically, in the Chang 6 reservoir of the Y192 block, the permeability of the area is 0.19mD, the median radius is 0.16μm, and due to the development of natural fractures, this method is used to adjust the well pattern parameters:

[0051] 1. Establish a reservoir fracture development intensity model, use the sand fracture intensity (SFI) and intra-layer fracture intensity (FFI) to evaluate the fracture development intensity, and identify 70 fractures in the 101m long 6th section;

[0052] 2. According to the classification standard of reservoir fracture development degree, the development method of fracture development intensity in this area is determined to be the second type, and the rectangular well pattern advanced water injection development is determined;

[0053] 3. The maximum principal stress orientation in this area is mainly NE70°, the safe angle range is between 53.2° and 96.8°, the coupling degree between the fracture angle and the principal stress is less than 85%, and the fracture angle is mainly concentrated between 80° and 90°. The horizontal well orientation is adjusted to be perpendicular to the main fracture angle.

[0054] It is predicted that the initial output will be 8.7t-11.0t, and 6.9t-9.5t in the year of reaching full production, with an internal rate of return of 8.1%, which can be effectively developed.

Claims

1. A horizontal well layout method based on fracture development intensity characteristics, characterized in that: The following steps are involved: The first step is to establish a reservoir fracture development intensity model to calculate the sand layer fracture intensity SFI and the intra-layer fracture intensity FFI; The second step is to establish the classification standard of reservoir fracture development degree. According to the production dynamic data, SFI and FFI values, the relationship curve between the production dynamic data and the SFI or FFI value is drawn by the intersection diagram method. The relationship curve is a trend line summarized by scatter points. The trend line is obtained by the curve tangent intersection method to obtain the dividing points A and B. The horizontal coordinate values ​​of A and B are the specific dividing values. Among them, the horizontal coordinate A is less than the horizontal coordinate B, and the SFI or FFI value is less than the horizontal coordinate A, which is the third category, the horizontal coordinate greater than or equal to the horizontal coordinate A to less than or equal to the horizontal coordinate B, which is the second category, and the horizontal coordinate greater than the horizontal coordinate B is the first category; when there is only one body segment with fracture development in the reservoir, the SFI is used as the horizontal coordinate, and when there are multiple body segments with fracture development in the reservoir, the FFI is used as the horizontal coordinate; Step 3: Select the development method based on the intensity of fracture development. For areas with the first type of fracture intensity, long horizontal wells and quasi-natural energy development are used. For areas with the second and third types of fracture intensity, rectangular well pattern advanced water injection development is used. Step 4: Determine the water injection development method. For the second type of fracture intensity area, the coupling degree between the natural fractures, artificial fractures and the principal stress direction in the block is calculated based on the imaging logging data. When the coupling degree is higher than 85%, the horizontal well orientation is perpendicular to the principal stress direction; when the coupling degree is lower than 85%, the horizontal well orientation is perpendicular to the natural fracture angle. For the third type of fracture intensity area, the horizontal well orientation is perpendicular to the principal stress direction.

2. A horizontal well layout method based on fracture development intensity characteristics according to claim 1, characterized in that: The coupling degree refers to the proportion of the number of cracks within the safe angle range among the natural cracks and artificial cracks to the total number of cracks.

3. A horizontal well layout method based on fracture development intensity characteristics according to claim 2, characterized in that: The safety angle range is between δ-α and δ+α, where δ-α is the minimum safety angle, δ+α is the maximum safety angle, α is the angle between the injection well and the horizontal well, and δ is the maximum principal stress direction angle.

4. A horizontal well layout method based on fracture development intensity characteristics according to claim 1, characterized in that: Said Where L is the thickness of the sand body section, i1 is the top depth of the i-th fracture development section in the sand body section, i2 is the bottom depth of the i-th fracture development section in the sand body section, and FIP(x) is the fracture index parameter value at depth x.

5. The method for horizontal well layout based on fracture development intensity characteristics according to claim 1, characterized in that: Said L i is the thickness of the i-th sand body segment, i1 is the top depth of the i-th fracture development segment of the k-th sand body segment, i2 is the bottom depth of the i-th fracture development segment of the k-th sand body segment, and FIP(x) is the fracture index parameter value at depth x.

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