Horizontal well shaft reconstruction and re-fracturing method

Abstract

The invention discloses a horizontal well shaft reconstruction and re-fracturing method which comprises the following steps: performing pre-fracturing energy supplementation on an old well shaft of a horizontal well, and plugging an original crack in the old well shaft of the horizontal well; a casing pipe is put into the old horizontal well shaft, and the outer diameter of the casing pipe is smaller than the inner diameter of the old horizontal well shaft; a resin sealing material is injected into an annulus formed by the casing and the old well shaft of the horizontal well, and a preparation method of the resin sealing material comprises the steps that maleic acid and D-33 dihydric alcohol are mixed and then react for a set duration at the set temperature, a vinyl monomer is added into a reaction product, stirring is conducted, and the resin sealing material is obtained; and after the resin sealing material is cured, horizontal well refracturing is carried out in the casing pipe. The invention aims to solve the problems of gas channeling and water channeling in the well cementation process.

Description

Technical Field

[0001] The invention belongs to the field of oil production technology, and in particular relates to a horizontal wellbore reconstruction and repeated fracturing method. Background Art

[0002] The patent application with the publication number CN109973067A discloses a horizontal well fracture plugging wellbore reconstruction and repeated fracturing method, which injects liquid into the formation until the wellhead injection pressure is greater than the formation closing pressure of the well; injects fracture plugging particles into the original fracture; injects cement into the formation; then injects drillable plugging materials; after the cement and fracture plugging particles are stable, the drilling and grinding tool is lowered to drill and grind the drillable plugging materials and circulate them out of the ground through liquid; the first drillable bridge plug and perforating gun are pumped down to the first new fracture position, the perforating gun is controlled to perforate, and the perforating gun is separated from the first drillable bridge plug, the first drillable bridge plug is set, and then the perforating gun is pulled out, and then the casing is injected for fracturing, and the drillable bridge plug and perforating gun pump are repeatedly injected to complete all the layers that need to be transformed. Although the patent creates a new wellbore by plugging old fractures and filling the layers that failed cementing before with plugging agents and cement, it effectively prevents the tool sand burial caused by the upper and lower layers of the casing due to poor cementing quality. However, during cement injection wellbore reconstruction, gas and water channeling are prone to occur during the cement slurry cementing process due to the high viscosity and density of cement and its high shrinkage rate. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a horizontal wellbore re-fracturing method, which aims to solve the gas and water channeling phenomena occurring during the cementing process.

[0004] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0005] A horizontal wellbore re-fracturing method comprising:

[0006] Performing pre-pressure energy replenishment on the wellbore of the horizontal well and sealing the original cracks in the wellbore of the horizontal well;

[0007] A casing is lowered into the wellbore of the horizontal well and the old well, wherein the outer diameter of the casing is smaller than the inner diameter of the wellbore of the horizontal well and the old well;

[0008] Injecting a resin sealing material into the annulus formed by the casing and the wellbore of the horizontal well, the resin sealing material is prepared by: mixing maleic acid and D-33 diol, reacting at a set temperature for a set time, adding a vinyl monomer to the reaction product, and stirring to obtain the resin sealing material;

[0009] After the resin sealing material is solidified, repeated fracturing of the horizontal well is performed in the casing.

[0010] Furthermore, the molar ratio of the maleic acid to the D-33 diol is (1-2):1.

[0011] Furthermore, the molar ratio of the vinyl monomer to the maleic acid is 1:1.

[0012] Furthermore, the set temperature is 190°C to 220°C.

[0013] Furthermore, the set duration is 1 hour to 2 hours.

[0014] Further, a catalyst is added to the mixed maleic acid and D-33 diol.

[0015] Furthermore, the catalyst is methyl ethyl ketone peroxide.

[0016] Furthermore, the wellbore of the horizontal well is replenished with energy before pressure increase, specifically: the energy is replenished before pressure increase to 100% to 120% of the original formation pressure.

[0017] Furthermore, gel leakage reduction material is used to seal the original cracks in the wellbore of the old horizontal well.

[0018] Furthermore, the casing is lowered into the wellbore of the horizontal well with the help of a drag reducing agent.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The present invention provides a horizontal wellbore re-fracturing method, which firstly performs pre-fracturing energy replenishment on the horizontal wellbore and seals the original cracks in the horizontal wellbore, then lowers casing into the horizontal wellbore, wherein the outer diameter of the casing is smaller than the inner diameter of the horizontal wellbore, and injects resin sealing material into the annulus formed by the casing and the horizontal wellbore. The resin sealing material is: maleic acid and D-33 diol are mixed, reacted at a set temperature for a set time, vinyl monomer is added to the reaction product, and stirred to obtain the resin sealing material. The resin sealing material has the characteristics of low viscosity, low density and good pumpability. The use of a small casing and the resin sealing material can effectively solve the problem of gas and water channeling in the cement slurry cementing process due to the large viscosity and density of cement and the high shrinkage rate.

[0021] It is beneficial to restore the integrity of the old horizontal wellbore, effectively block the pipe leakage, carry out bridge-shot continuous subdivision cutting fracturing to improve the efficiency of horizontal well volume repeated fracturing operations, increase the daily oil increase of a single well from 8t to 10t, and effectively shorten the fracturing operation cycle by 15 to 20 days. It has positive significance for improving the technical level of horizontal well small-casing cementing wellbore reconstruction repeated fracturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the specific implementation modes of the present invention, the drawings required for use in the description of the specific implementation modes will be briefly introduced below. Obviously, the drawings described below are some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 The present invention is a flowchart of the preparation of resin sealing materials in a horizontal wellbore reconstruction and repeated fracturing method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In some embodiments, a horizontal wellbore re-fracture method comprises the following steps:

[0026] S1. Recharge the wellbore of the old horizontal well before pressure is applied, and seal the original cracks in the wellbore of the old horizontal well.

[0027] In this embodiment, the pre-pressure compensation can reach 100% to 120% of the original formation pressure, which is conducive to forming a complex fracture network.

[0028] In this embodiment, the gel leakage reduction material is used to seal the original cracks in the wellbore of the old horizontal well.

[0029] S2. A casing is lowered into the wellbore of the horizontal well. The outer diameter of the casing is smaller than the inner diameter of the wellbore of the horizontal well.

[0030] In this embodiment, the casing is lowered into the wellbore of the horizontal well with the help of a drag reducing agent.

[0031] S3. Inject resin sealing material into the annulus formed by the casing and the wellbore of the horizontal well. The preparation method of the resin sealing material is: mix maleic acid and D-33 diol, react at a set temperature for a set time (to characterize the degree of reaction, the acid value of the synthetic resin is 17 to 25), add vinyl monomer to the reaction product, and stir to obtain the resin sealing material.

[0032] In this embodiment, the molar ratio of maleic acid to D-33 diol is 2:1, the catalyst added to the mixed maleic acid and D-33 diol is methyl ethyl ketone peroxide, the set temperature is 200°C, the set time is 1.5h1h~2h, and the molar ratio of vinyl monomer to maleic acid is 1:1.

[0033] The first and second interfaces of the resin sealing material have medium and good bonding, accounting for 100%, meeting the requirements for subdivided cutting volume fracturing pressure, and the compressive strength reaches 65MPa.

[0034] S4. After the resin sealing material is solidified, repeated fracturing of the horizontal well is performed in the casing.

[0035] More specifically, when replenishing energy before pressure is applied, the segmented deficit status is calculated, and a chart showing the degree of recovery of formation pressure at different replenishment multiples is established. The replenishment multiple is optimized to be 0.8-1 times. At the same time, the amount of replenishment fluid is differentiated within a single well segment. To achieve uniform replenishment, a fixed tubing tool is used to replenish energy in 4-6 segments. Based on the scaling characteristics of the reservoir, deblocking acid is placed in front of each segment.

[0036] When plugging the original fractures in the wellbore of the horizontal well, for large-scale artificial fractures, high-strength gel leakage reduction materials are used, multi-stage plug leakage reduction, and the gel injection volume is optimized (≥400m 3 ), weak-strong gel ratio (1:3), achieving one-time successful leakage reduction, and the water absorption index after leakage reduction is ≤80L / min.Mpa, meeting the requirements of later cementing.

[0037] When running casing into the wellbore of an old horizontal well, the Landmark drilling engineering software is used to calculate the mechanical conditions for running a 41 / 2″ small casing according to the wellbore trajectory and the length of the horizontal section. The weight rod and drag reducer are matched to control the running speed (50m / h~80m / h) to ensure smooth running of the small casing.

[0038] When repeating horizontal well fracturing in casing, the soluble bridge plug for 41 / 2″ small casing is used, and the pressure bearing capacity reaches 70MPa, realizing efficient and rapid fracturing; the ultra-deep penetration perforating bullet with equal aperture is used to increase the penetration depth of perforation, solving the problem of difficult formation fracturing and high pressure after double-layer casing bridge shooting in soluble casing wellbore reconstruction technology.

[0039] Preferably, when injecting resin sealing material into the annulus formed by the casing and the wellbore of the horizontal well and the old well, a composite curing system is injected. For example, at 50°C, the composite curing system is: 0.2% methyl ethyl ketone peroxide + 0.02% cobalt cyclopentaneate, the curing time is 7 hours, and the compressive strength is 30 MPa; at 60°C, the composite curing system is: 0.1% methyl ethyl ketone peroxide + 0.02% cobalt cyclopentaneate, the curing time is 7 hours, and the compressive strength is 32 MPa; at 70°C, the composite curing system is: 0.1% methyl ethyl ketone peroxide + 0.01% cobalt cyclopentaneate, the curing time is 7 hours, and the compressive strength is 32 MPa. Kaolin and titanium dioxide can both meet the requirements, but titanium dioxide has a high cost, so kaolin is preferably used as the filler.

[0040] The fracturing method of the present invention has low cost, with a daily cost of 30,000 yuan per well, saving 450,000 to 600,000 yuan per well. About 10 old wells with casing and wellbore reconstruction are constructed each year, and the market scale can reach 9 to 18 million yuan in the next three years.

[0041] In some embodiments, a horizontal wellbore re-fracture method comprises the following steps:

[0042] S1. Recharge the wellbore of the old horizontal well before pressure is applied, and seal the original cracks in the wellbore of the old horizontal well.

[0043] In this embodiment, the pre-pressure compensation can reach 100% to 120% of the original formation pressure, which is conducive to forming a complex fracture network.

[0044] In this embodiment, the gel leakage reduction material is used to seal the original cracks in the wellbore of the old horizontal well.

[0045] S2. A casing is lowered into the wellbore of the horizontal well. The outer diameter of the casing is smaller than the inner diameter of the wellbore of the horizontal well.

[0046] In this embodiment, the casing is lowered into the wellbore of the horizontal well with the help of a drag reducing agent.

[0047] S3. Inject resin sealing material into the annulus formed by the casing and the wellbore of the horizontal well. The preparation method of the resin sealing material is: mix maleic acid and D-33 diol, react at a set temperature for a set time (to characterize the degree of reaction, the acid value of the synthetic resin is 17 to 25), add vinyl monomer to the reaction product, and stir to obtain the resin sealing material.

[0048] In this embodiment, the molar ratio of maleic acid to D-33 diol is 1:1, the catalyst added to the mixed maleic acid and D-33 diol is methyl ethyl ketone peroxide, the set temperature is 220°C, the set time is 1 hour, and the molar ratio of vinyl monomer to maleic acid is 1:1.

[0049] The first and second interfaces of the resin sealing material have medium and good bonding, accounting for 100%, meeting the requirements for subdivided cutting volume fracturing pressure, and the compressive strength reaches 65MPa.

[0050] S4. After the resin sealing material is solidified, repeated fracturing of the horizontal well is performed in the casing.

[0051] In some embodiments, a horizontal wellbore re-fracture method comprises the following steps:

[0052] S1. Recharge the wellbore of the old horizontal well before pressure is applied, and seal the original cracks in the wellbore of the old horizontal well.

[0053] In this embodiment, the pre-pressure compensation can reach 100% to 120% of the original formation pressure, which is conducive to forming a complex fracture network.

[0054] In this embodiment, the gel leakage reduction material is used to seal the original cracks in the wellbore of the old horizontal well.

[0055] S2. A casing is lowered into the wellbore of the horizontal well. The outer diameter of the casing is smaller than the inner diameter of the wellbore of the horizontal well.

[0056] In this embodiment, the casing is lowered into the wellbore of the horizontal well with the help of a drag reducing agent.

[0057] S3. Inject resin sealing material into the annulus formed by the casing and the wellbore of the horizontal well. The preparation method of the resin sealing material is: mix maleic acid and D-33 diol, react at a set temperature for a set time (to characterize the degree of reaction, the acid value of the synthetic resin is 17 to 25), add vinyl monomer to the reaction product, and stir to obtain the resin sealing material.

[0058] In this embodiment, the molar ratio of maleic acid to D-33 diol is 2:1, the catalyst added to the mixed maleic acid and D-33 diol is methyl ethyl ketone peroxide, the set temperature is 190°C, the set time is 2h, and the molar ratio of vinyl monomer to maleic acid is 1:1.

[0059] The first and second interfaces of the resin sealing material have medium and good bonding, accounting for 100%, meeting the requirements for subdivided cutting volume fracturing pressure, and the compressive strength reaches 65MPa.

[0060] S4. After the resin sealing material is solidified, repeated fracturing of the horizontal well is performed in the casing.

[0061] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0062] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A horizontal wellbore re-fracturing method, characterized in that: include: Performing pre-pressure energy replenishment on the wellbore of the horizontal well and sealing the original cracks in the wellbore of the horizontal well; A casing is lowered into the wellbore of the horizontal well and the old well, wherein the outer diameter of the casing is smaller than the inner diameter of the wellbore of the horizontal well and the old well; Injecting a resin sealing material into the annulus formed by the casing and the wellbore of the horizontal well and the old well, the resin sealing material is prepared by: mixing maleic acid and D-33 diol, reacting at a set temperature for a set time, adding a vinyl monomer to the reaction product, and stirring to obtain the resin sealing material; After the resin sealing material is solidified, repeated fracturing of the horizontal well is performed in the casing.

2. A horizontal wellbore re-fracturing method according to claim 1, characterized in that: The molar ratio of the maleic acid to the D-33 diol is (1-2):

1.

3. A horizontal wellbore re-fracturing method according to claim 2, characterized in that: The molar ratio of the vinyl monomer to the maleic acid is 1:

1.

4. A horizontal wellbore re-fracturing method according to claim 1, characterized in that: The set temperature is 190°C to 220°C.

5. A horizontal wellbore re-fracturing method according to claim 1, characterized in that: The set duration is 1h to 2h.

6. A horizontal wellbore re-fracturing method according to claim 1, characterized in that: The catalyst was added to the mixed maleic acid and D-33 diol.

7. A horizontal wellbore re-fracturing method according to claim 6, characterized in that: The catalyst is methyl ethyl ketone peroxide.

8. A horizontal wellbore re-fracturing method according to claim 1, characterized in that: The horizontal well old wellbore is replenished before pressure is applied, specifically: the energy is replenished before pressure to 100% to 120% of the original formation pressure.

9. A horizontal wellbore re-fracturing method according to claim 1, characterized in that: The gel leakage reduction material is used to seal the original cracks in the wellbore of the old horizontal well.

10. A horizontal wellbore re-fracturing method according to claim 1, characterized in that: The casing is lowered into the wellbore of the horizontal well with the drag reducing agent.

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