A method for repeatedly fracturing a high water cut horizontal well in a low permeability reservoir

Abstract

The application discloses a repeated fracturing method for a high-water-cut horizontal well in a low-permeability reservoir, which comprises the following steps: performing a repeated fracturing seam design on the high-water-cut horizontal well, determining a high-water-yielding fracture of the high-water-cut horizontal well in a target block, determining a safety distance S of the high-water-yielding fracture and an adjacent fracturing fracture, performing the seam design according to the principle that the distance of the high-water-yielding fracture and the adjacent fracturing fracture along the wellbore direction is greater than the safety distance S, and determining the safety distance S according to the maximum horizontal stress direction of the target block, judging the predicted extension direction of the high-water-yielding fracture, and determining the safety distance S based on the included angle alpha between the extension direction and the wellbore. The method solves the problem that the existing repeated fracturing construction of the high-water-cut horizontal well in the low-permeability reservoir easily leads to water flooding.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of oil extraction engineering, in particular to a repeated fracturing process method for a high water cut horizontal well in a low permeability reservoir. BACKGROUND

[0002] Currently, repeated fracturing is performed on a high water cut horizontal well in a low permeability reservoir. When repeated fracturing is performed after water plugging in the horizontal well, if the distance between the repeated fracturing fractures and the water plugging fractures is too close, the water plugging fractures are prone to failure due to matrix seepage, resulting in water flooding. Therefore, for a high water cut horizontal well in a low permeability reservoir, a corresponding repeated fracturing construction method needs to be developed. SUMMARY

[0003] Therefore, the present disclosure provides a repeated fracturing method for a high water cut horizontal well in a low permeability reservoir, which solves the problem that the existing repeated fracturing construction of a high water cut horizontal well in a low permeability reservoir is prone to water flooding.

[0004] To achieve the above-mentioned purpose, the repeated fracturing method for a high water cut horizontal well in a low permeability reservoir comprises a repeated fracturing fracture design for a high water cut horizontal well, wherein:

[0005] determining a high water production fracture of a high water cut horizontal well in a target block;

[0006] determining a safe distance S between the high water production fracture and an adjacent fracturing fracture;

[0007] performing the fracture design according to the principle that the distance between the high water production fracture and the adjacent fracturing fracture along the wellbore direction is greater than the safe distance S;

[0008] The determination method of the safe distance S comprises:

[0009] determining the safe distance S based on the angle a between the extension direction and the wellbore according to the maximum horizontal stress direction of the target block.

[0010] In the present disclosure and possibly some embodiments, the maximum vertical distance between two artificial fractures that have occurred during the segmented fracturing construction process of the horizontal well in the target block is taken as the reference value D of the safe distance between the high water production fracture and the adjacent fracturing fracture. If there is no relevant reference value, the reference value D is 30 m;

[0011] When the angle a = 90°, S = D, when 0° < a < 90°, S = D / sin a, and when 90° < a < 180°, S = D / sin (a-90°).

[0012] In the present disclosure and possibly some embodiments, the method of the fracture design comprises:

[0013] When the length of the sandstone section on both sides of the high-yield water fracture is greater than the safe distance S, the sandstone section is designed to be fractured; when the length of the sandstone section is less than or equal to the safe distance S, the sandstone section is not designed to be fractured when repeated fracturing is performed in the sandstone section.

[0014] When the length of the sandstone section on both sides of the high-yield water fracture is less than or equal to the safe distance S, and the sandstone section is adjacent to a mudstone section, if the length of the mudstone section on both sides or on one side is greater than or equal to 20 m, a fracture is designed at the starting position of the other sandstone section adjacent to the mudstone section; if the length of the mudstone section on both sides or on one side is less than 20 m, the length S1 of the corresponding sandstone section and the length S2 of the mudstone section are obtained, and a fracture is designed in the other sandstone section adjacent to the mudstone section, with the other end of the mudstone section as the starting position and S3=S-S1-S2*1.5 as the length.

[0015] In the present disclosure and some possible embodiments, when the length of the sandstone section on both sides or on one side of the high-yield water fracture is greater than or equal to two safe distances S, the in-situ temporary plugging and steering technology cannot be used for the adjacent repeated fracturing fractures in the sandstone section.

[0016] In the present disclosure and some possible embodiments, the high-yield water fracture is determined by a geological analysis method.

[0017] The geological analysis method is to obtain the position of the high-yield water fracture by the relationship between the sedimentary facies belt and the horizontal well and the adjacent injection well.

[0018] In the present disclosure and some possible embodiments, the high-yield water fracture is determined by a field test method.

[0019] The field test method is to lower a horizontal well segmented production capacity measurement and control tool in a target well, apply a cable transmission signal, obtain downhole liquid production and water cut data of each section through a ground direct-reading terminal, and determine the water production of each section to determine the position of the high-yield water fracture.

[0020] In the present disclosure and some possible embodiments, when repeated fracturing construction is performed, water plugging is performed on the high-yield water fracture, and whether the water plugging is effective is determined according to the production effect after the operation. If the water plugging is effective, repeated fracturing construction is performed on the well; if the water plugging is not effective, the water plugging operation is performed again until the water plugging is effective.

[0021] In the present disclosure and some possible embodiments, when fracturing construction is performed on a fracturing fracture adjacent to the high-yield water fracture, whether the fracturing fracture communicates with the high-yield water fracture is determined. If the communication occurs, the safe distance S is corrected.

[0022] The method of the present application, aiming at high-yield water fracture, combines artificial fracture and wellbore direction to determine the reasonable safety distance S with adjacent repeated fracturing fractures, and according to the safety distance S, the position selection of the fracture of the repeated fracturing target well is guided, and then the target well is subjected to effective water plugging and then repeated fracturing, so as to improve the single well production of the low permeability reservoir high water cut horizontal well, realize the combination of water plugging and repeated fracturing of the horizontal well high water cut old well, improve the water injection development effect of the low permeability horizontal well, and solve the problem that the existing low permeability reservoir high water cut horizontal well is prone to water flooding during repeated fracturing construction. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of the embodiments of the present disclosure taken with reference to the accompanying drawings, in which:

[0024] Figure 1 is a design fracture distribution schematic diagram of the sandstone section where the high-yield water fracture is located when the length of the sandstone section of the present application is greater than the safety distance S;

[0025] Figure 2 is a design fracture distribution schematic diagram of the sandstone section where the high-yield water fracture is located when the length of the sandstone section of the present application is less than or equal to the safety distance S;

[0026] Figure 3 is a design fracture distribution schematic diagram of the sandstone section where the high-yield water fracture is located when the length of the sandstone section of the present application is less than or equal to the safety distance S;

[0027] Figure 4 is a high-yield water fracture and sandstone section schematic diagram of the A horizontal well of the Z block of the embodiment 1 of the present disclosure;

[0028] Figure 5 is a repeated fracturing target well fracturing fracture distribution schematic diagram of the embodiment 1 of the present disclosure. EMBODIMENT

[0029] The present disclosure is described below based on the embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the following detailed description of the present disclosure, some specific details are described in detail. However, those skilled in the art can also fully understand the present disclosure without detailed description of the parts.

[0030] In addition, those skilled in the art should understand that the drawings provided are only for the purpose of illustrating the purposes, features and advantages of the present disclosure, and the drawings are not actually drawn to scale.

[0031] At the same time, unless the context clearly requires otherwise, the terms "comprise", "comprise", and similar words in the entire specification and claims should be interpreted as inclusive meaning rather than exclusive or exhaustive meaning; that is, as "including but not limited to".

[0032] The low-permeability reservoir high-water-cut horizontal well repeated fracturing method adopted by the embodiments of the present disclosure, in combination with the drawings, has the following specific steps:

[0033] Step one: determining the high-water-cut fracture of the high-water-cut horizontal well in the target block:

[0034] The high-water-cut fracture of the high-water-cut horizontal well in the target block is determined through a geological analysis method or a field test method. The geological analysis method is to comprehensively determine and analyze the position of the high-water-cut fracture by the relationship between the sedimentary facies belt and the adjacent injection well of the horizontal well. The field test method is to lower the horizontal well section production measurement and control tool in the target well, apply cable transmission signals, obtain the production capacity of each section through a ground direct-reading terminal, measure the downhole liquid production, water cut and other data, directly determine the water production of each section, and determine the high-water-cut fracture.

[0035] Step two: determining the reasonable safety distance S between the high-water-cut fracture and the adjacent fracturing fracture:

[0036] First, the predicted extension direction of the artificial fracture of the high-water-cut horizontal well is determined according to the maximum horizontal stress direction of the target block. If the target block has only been tested for the stress direction, since the extension direction of the artificial fracture is always consistent with the maximum horizontal principal stress direction, the maximum horizontal principal stress direction is taken as the predicted extension direction of the artificial fracture of the well. If the well in the block has been fractured and monitored or monitored, the monitored extension direction of the artificial fracture is taken as the predicted extension direction of the high-water-cut fracture of the well.

[0037] Then, the maximum vertical distance between the two artificial fractures that have occurred during the section fracturing construction of the horizontal well in the target block in the past is taken as the reference value D of the safety distance between the high-water-cut fracture and the adjacent fracturing fracture. If there is no relevant reference value, the reference value D is 30 m.

[0038] Finally, the reasonable safety distance S between the high-water-cut fracture and the adjacent fracturing fracture is determined based on the angle a between the extension direction and the wellbore. Specifically, when the angle a = 90°, S = D, when 0° < a < 90°, S = D / sin a, and when 90° < a < 180°, S = D / sin (a-90°).

[0039] Step three: designing the fracture distribution for the repeated fracturing of the high-water-cut horizontal well:

[0040] The principle of designing the fracture distribution for the repeated fracturing of the high-water-cut horizontal well is that the high-water-cut fracture needs to be water-plugged, and the other fractures are repeatedly fractured. The distance between the repeatedly fractured fracture and the high-water-cut fracture along the wellbore direction is greater than the safety distance S, so as to ensure that the repeatedly fractured fracture will not communicate with the high-water-cut fracture during the operation. The fracture distribution is designed according to the following conditions:

[0041] 1. If the lengths of the sandstone strata on both sides of the high-yield water fracture are greater than the safe distance S, such as Figure 1 As shown, the third fracture is a high-water-yield fracture. Fractures were designed on both sides of the sandstone layer of this high-water-yield fracture, and the resulting repeated fracturing and re-fracturing new fractures are the second and fourth fractures, respectively.

[0042] If the high-yield water fracture has only one side with a sandstone layer length greater than the safe distance S, such as Figure 2 As shown, the second fracture is a high-yield water fracture. The length of the sandstone layer to the right of this high-yield water fracture is greater than the safety distance S. Therefore, the fracture is designed and laid only in the sandstone layer to the right. The resulting repeated fracturing and repair fracture is the third fracture in the figure. The same applies to the left side.

[0043] 2. When the length of the sandstone layer on either side or one side of a high-yield water fracture is less than or equal to the safety distance S, no fracture layout should be designed during repeated fracturing within that sandstone layer; if... Figure 2 As shown, if the length of the sandstone layer to the left of the high-yield water fracture is less than the safety distance S, then no fracture should be designed on that left side.

[0044] 3. The lengths of the sandstone sections on both sides of the high-yield water fracture are both less than or equal to the safe distance S, and the sandstone sections are adjacent to mudstone sections. If the length of the mudstone section is ≥20m, then... Figure 3 As shown, the third fracture is a high-water-yield fracture. The mudstone section to the left of the high-water-yield fracture is ≥20m. Therefore, a fracture is designed at the beginning of another sandstone section adjacent to this mudstone section. The resulting repeated fracturing and repair fracture is the second fracture in the figure.

[0045] If the length of the mudstone layer is <20m, then... Figure 3 As shown, the mudstone section on the right side of the high-yield water fracture 3 is <20m. It is necessary to obtain the length S1 of the sandstone section and the length S2 of the mudstone section. Then, taking the other end of the mudstone section as the starting position, and with a length of S3 = S - S1 - S2 × 1.5, design the fracture layout in another sandstone section adjacent to the mudstone section. The resulting repeated fracturing and repair fracture is the 4th fracture in the figure.

[0046] 4. If the high-yield fracture is located within a large sandstone section, and the length of the large sandstone section is greater than or equal to two safety distances S, when designing the repeated fracturing fracture layout, adjacent repeated fracturing fractures within this sandstone section should not use the in-fracture temporary plugging and diversion process to prevent the high-yield fracture from being connected through diversion.

[0047] Step 4: Perform water plugging operations on the high-yield cracks:

[0048] If the water plugging is not successful, the subsequent repeated fracturing can cause the water production and water content to further increase, and therefore the prerequisite for the repeated fracturing is to effectively plug the high water production fracture. Specifically, according to the conventional technique in the art, a water plugging agent is injected into the high water production fracture of the repeated fracturing target well to plug the layer, and whether the water plugging is effective is determined according to the production effect after the operation. If the water plugging is effective, the repeated fracturing operation is performed on the well, and if the water plugging is not effective, the water plugging operation is performed again until the water plugging is effective.

[0049] Step five: according to the conventional technique in the art, the perforating gun string is run into the repeated fracturing target horizontal well to perforate the position of the new fracture that needs to be pressurized, the perforating string is pulled out, and the well section perforated and the packer setting position are scraped to pass through the well.

[0050] Step six: according to the conventional technique in the art, the double-sealing single-clamp fracturing string is run in, the fracturing wellhead is installed, the fracturing manifold is connected, the surface pipeline is tested, and the pipeline is qualified without the phenomena of stabbing, leakage and seepage.

[0051] Step seven: according to the conventional technique in the art, the repeated fracturing fractures of the horizontal well are designed to be fractured, the string is pulled up step by step to sequentially complete the repeated fracturing fracture operation, and the water plugging fracture is not fractured.

[0052] During the fracturing operation, attention should be paid to judging whether the fracturing fracture communicates with the high water content fracture when the adjacent fracture of the high water content fracture is fractured. The main manifestations are as follows: first, after communicating with the high water production fracture, the tubing pressure will be obviously and rapidly reduced, and second, since the fracturing operation is sequentially pulled up from the bottom of the well, whether the lower fracturing layer communicates with the upper high water production fracture can be judged by the casing pressure. If it is found during the operation that the design safety distance S is still insufficient to effectively separate the high water content fracture from the adjacent repeated fracturing fracture, the safety distance S value needs to be further modified, and the subsequent wells of this type should be designed according to the modified safety distance.

[0053] Step eight: after the operation of all the designed target layers is completed, the fracturing string in the well is pulled out, and the pump is put into production. EMBODIMENT

[0054] The horizontal well Z block in the low-permeability reservoir of Daqing periphery has a reservoir permeability of 30 mD-100 mD, and there are 15 wells including the A horizontal well in the block. At present, 11 wells have water content exceeding 90%, and the production effect is poor. The A horizontal well has been fractured and put into production for 7 years, and at present, the daily water production is 27 m 3 , the daily oil production is 0.8 m 3 , and the water content is 97.1%.

[0055] The high water content A horizontal well adopts the repeated fracturing process method of the present application, and the specific steps are as follows:

[0056] Step one: Put the horizontal well section productivity control tool into the A horizontal well, and determine the high water production fracture of the A horizontal well as the second fracture by testing. Figure 4

[0057] Step two: The artificial fracture extension direction of the Z block is NE12°-NE26°, with an average of NE18°. It is judged that the artificial fracture extension direction of the horizontal well is NE18°. The maximum vertical distance between the two artificial fractures in the Z block is 25m, that is, the reference value of the safety distance D is 25m. Combined with the angle a between the wellbore and the fracture extension direction of 72°, the reasonable safety distance S between the high water production fracture and the adjacent fractured fracture is determined as 25 / sin72°=26.3m.

[0058] Step three: Design the fracture distribution for the repeated fracturing of the A horizontal well. There is a large section of sandstone on both sides of the original high water production fracture of the A horizontal well, which needs to be supplemented during repeated fracturing to achieve full transformation of the horizontal well. Taking the fracture distance of 26.3m as a reference, the repeated fracturing fracture distribution is designed as shown in Figure 5 . Among them, the distance between the second fracture and the third fracture is 27m, and the distance between the third fracture and the fourth fracture is 27m.

[0059] Step four: Perform water plugging operation in the high water production fracture of the A horizontal well, and inject water plugging agent into the second fracture. After plugging, the daily water production of the whole well is 18m 3 , the daily oil production is 3.5m 3 , and the water content decreases from 97.1% to 83.7%. It is judged that the water plugging is effective.

[0060] Step five: Put the perforating gun string into the A horizontal well, perforate the second fracture and the fourth fracture of the supplemented new fracture, and pull out the perforating string. Scrape the wellbore and the packer setting position.

[0061] Step six: Put in the double-sealing single-clamping fracturing string, install the fracturing wellhead, connect the fracturing manifold, and test the ground pipeline and gate. The pipeline is qualified without sticking, leakage and seepage.

[0062] Step seven: Perform repeated fracturing operation on the A horizontal well. Use the double-sealing single-clamping fracturing process string, and complete the repeated fracturing section construction in turn by gradually lifting the string. The third fracture is not fractured.

[0063] Step eight: After the fifth fracture is completed, pull out the fracturing string in the well, and put the pump into production.

[0064] ​The above-described embodiments are merely illustrative of the implementation of the present disclosure, which are described in a more specific and detailed manner, but should not be understood as a limitation on the scope of the patent of the present disclosure. It should be noted that, for those skilled in the art, without departing from the concept of the present disclosure, a number of modifications, equivalent replacements, improvements, etc. can be made, which are all within the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure should be subject to the appended claims.

Claims

1.A method for repeated fracturing of a high water cut horizontal well in a low permeability reservoir, comprising a repeated fracturing fracture design for a high water cut horizontal well, characterized in that: a high water production fracture of a high water cut horizontal well in a target block is determined; a safe distance S between the high water production fracture and an adjacent fracturing fracture is determined; the fracture design is performed according to the principle that the distance between the high water production fracture and the adjacent fracturing fracture along the wellbore direction is greater than the safe distance S; the method for determining the safe distance S comprises: determining the expected extension direction of the high water production fracture according to the maximum horizontal stress direction of the target block, and determining the safe distance S based on the included angle a between the extension direction and the wellbore; the maximum vertical distance between two artificial fractures that have occurred during the staged fracturing construction of a horizontal well in the target block in the past is taken as the safe distance reference value D between the high water production fracture and the adjacent fracturing fracture, and if there is no relevant reference value, the reference value D is 30 m; when the included angle a = 90°, S = D, when 0° < a < 90°, S = D / sin a, and when 90° < a < 180°, S = D / sin (a-90°); the method for the fracture design comprises: when the length of the sandstone section on both sides or one side of the high water production fracture is greater than the safe distance S, a fracture is designed in the sandstone section; when the length of the sandstone section on both sides or one side of the high water production fracture is less than or equal to the safe distance S, no fracture is designed in the sandstone section during repeated fracturing; when the length of the sandstone section on both sides of the high water production fracture is less than or equal to the safe distance S, and the sandstone section is adjacent to a shale section, and the length of the shale section on both sides or one side is ≥ 20 m, a fracture is designed at the starting position of the other sandstone section adjacent to the shale section; when the length of the shale section on both sides or one side is < 20 m, the length S1 of the corresponding sandstone section and the length S2 of the shale section are obtained, a fracture is designed in the other sandstone section adjacent to the shale section with S3 = S-S1-S2×1.5 as the length and the other end of the shale section as the starting position. 2.The method for repeated fracturing of a high water cut horizontal well in a low permeability reservoir according to claim 1, characterized in that: when the length of the sandstone section on both sides or one side of the high water production fracture is greater than or equal to two safe distances S, the adjacent repeated fracturing fractures in the sandstone section cannot use the in-fracture temporary plugging and diverting technology. 3.The method for repeated fracturing of a high water cut horizontal well in a low permeability reservoir according to claim 1 or 2, characterized in that: the high water production fracture is determined by a geological analysis method; the geological analysis method is to obtain the position of the high water production fracture through the relationship between the sedimentary facies belt and the horizontal well and the adjacent injection well. 4.The method for repeated fracturing of a high water cut horizontal well in a low permeability reservoir according to claim 1 or 2, characterized in that: the high water production fracture is determined by a field test method; The field test method is to apply cable transmission signal to the segmented production and control tool of the horizontal well in the target well, to obtain the downhole liquid production and water cut data of each segment through the ground direct reading terminal, to obtain the water production of each segment through the liquid production and water cut, and to determine the high water production fracture position. 5.The repeated fracturing method for high water cut horizontal well in low permeability reservoir according to claim 1 or 2, characterized in that: When the repeated fracturing operation is performed, water plugging operation is performed on the high water production fracture, and whether the water plugging is effective is determined according to the production effect after the operation, if the water plugging is effective, the repeated fracturing operation is performed on the well, and if the water plugging is not effective, the water plugging operation is performed again until the water plugging is effective. 6.The repeated fracturing method for high water cut horizontal well in low permeability reservoir according to claim 5, characterized in that: When the fracturing operation is performed on the fracturing fracture adjacent to the high water production fracture, whether the fracturing fracture and the high water production fracture are communicated is determined, and if the communication occurs, the safe distance S is corrected.

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