Jet fracturing yield increasing method for open hole horizontal well

Abstract

The invention discloses a jet fracturing yield increasing method for an open hole horizontal well, and relates to the technical field of oil and gas field development. Comprising the following steps: putting a coiled tubing with a spray gun into the toe of the open hole horizontal well to replace an acid-soluble temporary plugging agent solution; the pre-prepad fluid is positively injected, so that the open hole well wall is covered and temporarily plugged by the acid-soluble temporary plugging agent; the coiled tubing is dragged to the position needing to be fractured, fracturing fluid is injected into the coiled tubing and the open hole well wall annulus at the same time, the large-displacement fracturing fluid is sprayed to the well wall from the spray gun at a high speed to form holes and cracks, and fracturing of the first position to the (N-1) th position is completed; injecting prepad fluid at the Nth position, injecting original rubber spacer fluid to replace the sand-carrying fluid after the sand-carrying fluid is jetted to form a hole crack; finally, hydrochloric acid is positively squeezed to dissolve the temporary plugging agent, and the well is normally closed for open flow; the purpose of preventing fracturing fluid from leaking, acidizing and dissolving organic matters by one tubular column is effectively achieved, and the effects of reducing damage of the fracturing fluid to a reservoir, improving the fracturing effect and reducing the fracturing operation cost are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and in particular to a jet fracturing production increase method for open hole horizontal wells. Background Art

[0002] Fracturing is one of the two key technologies in reservoir stimulation. It creates conductive fractures in low- or ultra-low-permeability reservoirs, effectively increasing well production. However, fracturing fluid filtration into near-fracture reservoirs or openhole reservoirs, where it comes into contact with water-sensitive minerals, causes mineral expansion and shrinks pore throats, hindering formation fluid flow and ultimately compromising the effectiveness of fracturing. Consequently, reducing fracturing fluid filtration has been a key research priority for decades. While research into fracturing fluid filtration has reached near-limited limits, 100% filtration-free performance remains elusive. This persistent problem of fracturing fluid filtration has limited its application in openhole wells, forcing the technology primarily to cased completions, increasing well completion costs.

[0003] In response to the damage and pollution caused by fracturing fluid loss to the horizontal open hole reservoir, even if the fracturing fluid performance is studied to the extreme, it cannot be guaranteed that there will be no loss. The present invention changes the research direction and creatively proposes a jet fracturing production increase method for open hole horizontal wells, thereby reducing the damage and pollution caused by fracturing fluid loss to the open hole horizontal section. Summary of the Invention

[0004] The present invention aims to solve the technical problem in the prior art that fracturing fluid loss causes damage and pollution to the horizontal open hole section reservoir, and aims to provide a jet fracturing production increase method for open hole horizontal wells. The method adopts a dual-liquid injection method of simultaneously injecting into the oil pipe and the open hole wall annulus. First, a temporary plugging agent is injected into the wellbore to establish a temporary plugging layer on the open hole wall, which can not only play the role of temporary casing to provide guarantee for hydrodynamic isolation and fluid supply, but also effectively reduce the damage of fracturing fluid loss to the open hole horizontal section. Then, after the temporary plugging agent is injected, a pre-preflush fluid is injected to remove organic matter blockage and prevent organic matter precipitation and deposition. Finally, hydrochloric acid is added to remove the pollution of the open hole section, improve the fracturing effect, and effectively achieve the purpose of preventing fracturing fluid loss, acidification and dissolution of organic matter in one trip of the tubing string.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for increasing production through jet fracturing in an open hole horizontal well comprises the following steps:

[0007] S1. Run the coiled tubing, with a spray gun connected to its lower end, into the toe of the open-hole horizontal well. Displace the acid-soluble temporary plugging agent solution through the coiled tubing.

[0008] S2. Positively squeeze the pre-pad fluid through the coiled tubing at a pressure 80% lower than the formation fracture pressure, allowing the acid-soluble temporary plugging agent to adhere to the wellbore wall to achieve temporary plugging, while simultaneously removing organic blockage and preventing organic matter precipitation and deposition.

[0009] S3. Slowly drag the coiled tubing to the first location in the openhole horizontal well section designed for jet fracturing. Simultaneously inject fracturing fluid from the coiled tubing and the annulus of the openhole wellbore. The fracturing fluid is ejected at high speed from the spray guns of the coiled tubing into the openhole wellbore, forming holes and cracks.

[0010] S4 repeats step S3 until the jet fracturing at the N-1th position of the open hole horizontal well section is completed;

[0011] S5. Slowly drag the coiled tubing to the Nth location in the openhole horizontal well section designed for jet fracturing. Simultaneously inject a pre-pad fluid, a sand-carrying fluid, and a raw rubber spacer fluid from the coiled tubing and the openhole wellbore annulus. The raw rubber spacer fluid displaces the sand-carrying fluid in the coiled tubing and casing annulus into the fracture at the Nth location, thereby completing the jet fracturing at the Nth location.

[0012] S6. Run the coiled tubing into the toe of the open-hole horizontal well, quickly pull it up, and flush the wellbore with 10% hydrochloric acid through the coiled tubing to dissolve the acid-soluble temporary plugging agent adsorbed on the open-hole wellbore wall.

[0013] S7. Inject clean water into the coiled tubing to replace the hydrochloric acid inside;

[0014] S8. Shut down the well and wait for the fracture to close and the wellhead pressure to stabilize, then release the fluid normally to complete the dual-fluid jet fracturing.

[0015] The present invention performs jet fracturing by a dual-fluid method of simultaneous injection of continuous oil tubing and the annulus of the open hole wall. First, a temporary plugging agent is injected into the wellbore to establish a temporary plugging layer on the open hole wall, which can not only play the role of temporary casing to provide guarantee for hydrodynamic isolation and fluid supply, but also effectively reduce the damage of fracturing fluid loss to the open hole horizontal section. Then, after the injection of the temporary plugging agent, a pre-preflush fluid is injected to remove organic blockage and prevent organic matter precipitation and deposition. Finally, hydrochloric acid is added to remove contamination of the open hole section and improve the fracturing effect, thereby effectively achieving the purpose of preventing fracturing fluid loss, acidification and dissolution of organic matter in one trip of the tubing string.

[0016] Furthermore, in step S1, the volume of the n-substituted acid-soluble temporary plugging agent solution is equivalent to the volume of the open hole horizontal well section.

[0017] Furthermore, the acid-soluble temporary plugging agent solution comprises the following components in percentage by weight: 4-7% calcium carbonate, 2-5% quartz particles, 0.3-0.7% acrylamide polymer temporary plugging agent, and the remainder water. Preferably, the acid-soluble temporary plugging agent solution comprises 5% calcium carbonate + 3% quartz particles + 0.5% acrylamide polymer temporary plugging agent, and the balance water.

[0018] Furthermore, in step S2, the volume of the positive squeeze pre-pad fluid is 1.2 to 1.4 times the wellbore volume.

[0019] Furthermore, the pre-pad solution comprises the following components in percentage by weight: 5-10% ethylene glycol butyl ether, 0.5% SP169, 0.1% fluorocarbon chain surfactant, and the remainder water. Preferably, the pre-pad solution has a formula of 8% ethylene glycol butyl ether + 0.5% SP169 + 0.1% fluorocarbon chain surfactant + the remainder water.

[0020] Furthermore, the fracturing fluid includes a pre-fluid, a sand-carrying fluid and clean water, wherein the pre-fluid and the sand-carrying fluid are at the formation temperature and the shear rate is 170s -1 When the viscosity is greater than 100 mPa·s, the performance of the pre-fluid and the sand-carrying fluid needs to be designed and adjusted according to the requirements of jet fracturing. The pre-fluid and the sand-carrying fluid can adopt any formula in the prior art that can achieve the corresponding function. Since it is a very mature prior art and is not an improvement point of the present invention, the present invention does not impose any limitation on this.

[0021] Furthermore, a proppant for keeping the cracks open is added to the sand-carrying fluid. The proppant can be any proppant in the prior art that can achieve the corresponding function. Since it is a very mature prior art and is not an improvement point of the present invention, the present invention does not impose any limitation on it.

[0022] Furthermore, the original rubber spacer liquid adopts a guar gum aqueous solution with a mass concentration of 0.1%.

[0023] Furthermore, in step S7, when the clean water is injected, it is necessary to ensure that when the coiled tubing is lifted to the bottom of the open hole horizontal section, the injected clean water just displaces the hydrochloric acid inside the coiled tubing to the nozzle of the spray gun.

[0024] Furthermore, the spray gun has spirally distributed small diameter nozzles. The specific structure and working principle of the spray gun are well-established prior art and are not an improvement point of the present invention. The present invention will not elaborate on this, but only defines the spiral arrangement of the nozzles to improve the spraying effect.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] 1. The present invention performs jet fracturing by a dual-fluid method of simultaneous injection of coiled tubing and open hole wall annulus. A temporary plugging agent is first injected into the wellbore to establish a temporary plugging layer on the open hole wall, which can not only play the role of temporary casing to provide guarantee for hydrodynamic isolation and fluid supply, but also effectively reduce the damage of fracturing fluid loss to the open hole horizontal section. Then, after the injection of the temporary plugging agent, a pre-preflush fluid is injected to remove organic blockage and prevent organic precipitation and deposition. Finally, hydrochloric acid is added to remove contamination of the open hole section and improve the fracturing effect, thereby effectively achieving the purpose of preventing fracturing fluid loss, acidification and dissolution of organic matter in one trip of the tubing string.

[0027] 2. The present invention injects the original gel spacer fluid after the sand-carrying fluid of the last fracturing to isolate the sand-carrying fluid from the subsequent hydrochloric acid and prevent the sand-carrying fluid from breaking and dissolving, resulting in a large amount of carried proppant accumulating in the wellbore and near-wellbore area.

[0028] 3. The present invention is suitable for open hole completion and does not require processes such as casing, cementing, and perforating, which can effectively save costs and improve economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0030] Figure 1 This is a schematic diagram of the state where the coiled tubing is lowered into the toe of an open hole horizontal well in the method of the present invention.

[0031] Figure 2 This is a schematic diagram of the coiled tubing being lowered into the heel of an open hole horizontal well in the method of the present invention. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the embodiments and drawings. Obviously, the schematic implementation methods of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0033] An embodiment of the present invention's jet fracturing stimulation method for open-hole horizontal wells will be described in detail below, with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions may be omitted. This is done to avoid unnecessary redundancy and to facilitate understanding by those skilled in the art.

[0034] As used herein, "ranges" are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, i.e., any lower limit may be combined with any upper limit to form a range.

[0035] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0036] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0037] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other substances not listed may also be included or that only the listed substances are included.

[0038] Unless otherwise specified, all steps of the present application can be performed sequentially or randomly, preferably sequentially.

[0039] Fracturing is one of the most effective means to increase reservoir permeability, among which hydraulic fracturing is the most widely used. However, the implementation of hydraulic fracturing technology generally requires staged fracturing or perforation completion, which increases construction costs. At the same time, the loss of fracturing fluid will cause pollution to the reservoir and the near-fracture area. Therefore, it limits the further large-scale use of fracturing technology in open hole wells.

[0040] Based on this, in order to reduce the filtration loss of fracturing fluid in the reservoir and improve the fracturing effect, achieve the purpose of reducing the cost of fracturing operations and being widely used in open hole horizontal wells, the present invention adopts a dual-liquid injection method of simultaneous injection of oil pipes and open hole well wall annuli. First, a temporary plugging agent is injected into the horizontal open hole section to form a temporary plugging of the reservoir well wall, effectively reducing the damage of fracturing fluid filtration loss to the open hole horizontal section. Then, the low permeability reservoir is transformed by jet fracturing to establish high permeability channels such as microcracks or cracks. Finally, hydrochloric acid is injected to dissolve the temporary plugging agent and release the exposed horizontal reservoir well wall. The present invention is suitable for open hole completion and does not require processes such as casing, cementing and perforating, which can effectively save costs and improve economic benefits.

[0041] The technical solution of the present invention is further described in detail below with reference to the embodiments.

[0042] It should be noted that the materials, reagents, methods and equipment used in the examples are conventional materials, reagents, methods and equipment in the art unless otherwise specified.

[0043] Example 1

[0044] A method for increasing production through jet fracturing in an open hole horizontal well comprises the following steps:

[0045] S1. Lower the coiled tubing with the spray gun connected to the bottom end into the toe of the open hole horizontal well (such as Figure 1 (as shown), open the casing gate, and replace the acid-soluble temporary plugging agent solution with a volume equivalent to that of the open hole horizontal well section through the coiled tubing;

[0046] The spray gun has spirally distributed small-diameter nozzles, and the number of nozzles is set according to the formation conditions. The formula of the acid-soluble temporary plugging agent solution is 5% calcium carbonate + 3% quartz particles + 0.5% acrylamide polymer temporary plugging agent + the balance water. This formula has a slow natural decomposition rate under wellbore conditions and has excellent temporary plugging performance. It can be quickly dissolved after contact with 10% hydrochloric acid, and the dissolved product is non-polluting.

[0047] S2. Close the casing gates and positively squeeze 1.2 to 1.4 times the wellbore volume of a pre-flush fluid through the coiled tubing at a pressure 80% lower than the formation fracture pressure. The pre-flush fluid has a formula of: 8% ethylene glycol butyl ether, 0.5% SP169, 0.1% fluorocarbon chain surfactant, and the balance water.

[0048] This step further enables the acid-soluble temporary plugging agent to adhere closely to the well wall to achieve temporary plugging without being contaminated by subsequent operations, and the pre-pad fluid can remove organic blockage and prevent organic matter from precipitating and depositing.

[0049] S3. Slowly drag the coiled tubing to the first position of the open hole horizontal well section designed for jet fracturing, open the casing gate, and inject fracturing fluid (pre-flush, sand-carrying fluid, and clean water) from the coiled tubing and the open hole well annulus simultaneously; the properties of the pre-flush and sand-carrying fluids need to be designed and adjusted according to the requirements of jet fracturing. In the present invention, the pre-flush and sand-carrying fluids are at formation temperature and a shear rate of 170s -1 When the viscosity is greater than 100 mPa·s, the sand-carrying fluid also contains a proppant for keeping the cracks open.

[0050] This step requires that the displacement in the coiled tubing is large enough so that the fracturing fluid is ejected at high speed from the nozzle of the coiled tubing. The open hole well wall is sprayed with high-pressure, high-energy fracturing fluid to form perforations. Under the continuous high-pressure impact of the fracturing fluid, cracks gradually form in the perforations and extend from the well wall to the deep reservoir. The fracturing fluid injected into the annulus of the open hole well wall fills the crack gap. When the sand-carrying fluid is displaced into the crack, the jet fracturing at the first position is completed.

[0051] S4. Slowly drag the coiled tubing to the second location in the openhole horizontal well section where jet fracturing is required, and then repeat step S3 to complete jet fracturing at the second location. Repeat this process until jet fracturing is completed at the N-1th location in the openhole horizontal well section.

[0052] S5. Slowly drag the coiled tubing to the Nth position in the open hole horizontal well section where jet fracturing is required, i.e. the position closest to the end of the horizontal well and the last designed fracturing point (e.g. Figure 2 ); pre-pad fluid, sand-carrying fluid, and original rubber spacer fluid are injected from the coiled tubing and the annulus of the open hole wellbore. The original rubber spacer fluid displaces all the sand-carrying fluid in the coiled tubing and the casing annulus into the crack at the Nth position, completing the jet fracturing at the Nth position.

[0053] In this step, the original gel spacer fluid is injected after the sand-carrying fluid to isolate the sand-carrying fluid from the subsequent hydrochloric acid, preventing the sand-carrying fluid from breaking and dissolving, resulting in a large amount of carried proppant accumulating in the wellbore and near-well area.

[0054] S6. Run the coiled tubing into the toe of the open-hole horizontal well, quickly pull up the coiled tubing, and positively displace 10% hydrochloric acid through the coiled tubing into the wellbore to dissolve the acid-soluble temporary plugging agent adsorbed on the open-hole wellbore wall. The amount of hydrochloric acid to be displaced is calculated based on the pulling speed, pumping rate, and coiled tubing diameter.

[0055] This step involves injecting 10% hydrochloric acid after the original rubber spacer fluid. On the one hand, hydrochloric acid flushing accelerates the dissolution of the acid-soluble temporary plugging agent close to the open hole wall. On the other hand, acidification also has the effect of unblocking the well wall.

[0056] S7. Inject clean water into the coiled tubing to replace the hydrochloric acid therein. The timing of the clean water injection is determined based on the coiled tubing lifting speed, pump displacement, and coiled tubing volume in step S6. This ensures that when the coiled tubing is raised to the heel of the open hole horizontal section, the injected clean water displaces the hydrochloric acid inside the coiled tubing to the nozzle. Furthermore, if the wellhead injection pressure is low during the hydrochloric acid squeezing process, the pump displacement may need to be increased to ensure stable injection pressure.

[0057] S8. Shut down the well and wait for the fracture to close and the wellhead pressure to stabilize, then release the fluid normally to complete the dual-fluid jet fracturing.

[0058] Finally, it should be noted that the above specific embodiments are only used to explain in detail the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above is only a specific implementation method of the present invention and is not used to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above specific embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions described in the above embodiments, or to replace or improve some or all of the technical features therein. These modifications, equivalent replacements, and improvements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and description of the present invention.

Claims

1. A method for increasing production by jet fracturing in open hole horizontal wells, characterized in that: The following steps are involved: S1. The coiled tubing with a spray gun connected to the bottom is lowered into the toe of the open hole horizontal well, and the acid-soluble temporary plugging agent solution is replaced through the coiled tubing; S2. The pre-flushing fluid is squeezed through the coiled tubing at a pressure 80% lower than the formation fracture pressure, so that the acid-soluble temporary plugging agent is close to the well wall to achieve temporary plugging, while removing the organic blockage and preventing the precipitation and deposition of organic matter; S3. Slowly drag the coiled tubing to the first position of the open hole horizontal well section designed for jet fracturing, and inject fracturing fluid from the coiled tubing and the annulus of the open hole well wall at the same time, so that the fracturing fluid is sprayed out from the spray gun of the coiled tubing at a high speed to spray the open hole well wall to form holes and cracks; S4. Repeat step S3 until the jet fracturing at the N-1th position of the open hole horizontal well section is completed; S5. slowly drag the coiled tubing to the Nth position of the open hole horizontal well section designed to be jet fracturing, and simultaneously inject the pre-fluid, sand-carrying fluid and original rubber spacer fluid from the coiled tubing and the open hole well wall annulus. The original rubber spacer fluid displaces the sand-carrying fluid in the coiled tubing and the casing annulus into the crack at the Nth position, thus completing the jet fracturing at the Nth position; S6. Lower the coiled tubing into the toe of the open hole horizontal well, quickly pull up the coiled tubing, and wash the well with 10% hydrochloric acid through the coiled tubing to dissolve the acid-soluble temporary plugging agent adsorbed on the open hole well wall; S7. Inject clean water into the coiled tubing to replace the hydrochloric acid inside it; S8. Shut down the well and wait for the fractures to close and the wellhead pressure to stabilize, then release the fluid normally to complete the dual-fluid jet fracturing.

2. A jet fracturing production enhancement method for open hole horizontal wells according to claim 1, characterized in that: In step S1, the volume of the n-substituted acid-soluble temporary plugging agent solution is equivalent to the volume of the open hole horizontal well section.

3. The method for increasing production by jet fracturing in open hole horizontal wells according to claim 1, characterized in that: The acid-soluble temporary plugging agent solution comprises the following components in percentage by mass: 4-7% calcium carbonate, 2-5% quartz particles, 0.3-0.7% acrylamide polymer temporary plugging agent, and the rest is water.

4. The method for increasing production by jet fracturing in open hole horizontal wells according to claim 1, characterized in that: In step S2, the volume of the positive squeeze pre-pad fluid is 1.2 to 1.4 times the wellbore volume.

5. The method for increasing production by jet fracturing in open hole horizontal wells according to claim 1, characterized in that: The pre-prefill solution comprises the following components in mass percentage: 5-10% ethylene glycol butyl ether, 0.5% SP169, 0.1% fluorocarbon chain surfactant, and the rest is water.

6. The method for increasing production by jet fracturing in open hole horizontal wells according to claim 1, characterized in that: The fracturing fluid includes a pre-fluid, a sand-carrying fluid and clean water, wherein the pre-fluid and the sand-carrying fluid are at the formation temperature and the shear rate is 170s -1 When the viscosity is greater than 100mPa·s.

7. A jet fracturing production enhancement method for open hole horizontal wells according to claim 6, characterized in that: The sand-carrying fluid also contains a proppant for keeping the cracks open.

8. The method for increasing production by jet fracturing in open hole horizontal wells according to claim 1, characterized in that: The original rubber spacer liquid is a guar gum aqueous solution with a mass concentration of 0.1%.

9. The method for increasing production by jet fracturing in open hole horizontal wells according to claim 1, characterized in that: In step S7, when the clean water is injected, it is necessary to ensure that when the coiled tubing is lifted to the bottom of the open hole horizontal section, the injected clean water just displaces the hydrochloric acid inside the coiled tubing to the nozzle of the spray gun.

10. A jet fracturing production enhancement method for open hole horizontal wells according to any one of claims 1 to 9, characterized in that: The spray gun has a spirally distributed small diameter nozzle.

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