Coiled tubing casing deformation horizontal well reservoir reformation method

Abstract

The present application relates to the technical field of downhole operation, and is a coiled tubing casing deformation horizontal well reservoir reconstruction method, which comprises the following steps: first, installing a casing damage reservoir reconstruction tool string at the lower end of the coiled tubing, wherein the casing damage reservoir reconstruction tool string comprises, from top to bottom, an upper centralizer, a directional device, a pulse generating device, a spray gun assembly, a lower centralizer and a guide shoe which are fixedly installed together. The present application optimizes the casing damage reservoir reconstruction tool string, thereby enhancing the passability of the tool. The spray gun assembly generates a low-pressure area at its nozzle by means of high-speed jet flow, so as to promote the high-pressure fluid in the annulus to enter the target layer, thereby achieving the isolation of the fracturing process without the need for a mechanical isolation device. The pulse energy increasing device arranged on the pulse generating device can convert the continuous and stable flow into a periodic pulsating flow, and has the characteristics of stability, high efficiency and good seepage capacity.

Description

Technical Field

[0001] This invention relates to the field of downhole operation technology and is a method for reservoir stimulation in horizontal wells with coiled tubing casing deformation. Background Technology

[0002] With the continuous deepening of oil exploration and development, unconventional oil and gas reservoirs with low permeability and low porosity are increasing. Conventional vertical wells can no longer meet development requirements, and horizontal wells are gradually becoming a necessary means to improve the overall benefits of oilfield exploration and development. Horizontal wells have advantages such as large drainage area, high single-well production, high penetration, high reserve utilization, and the ability to effectively avoid obstacles and harsh environments. Horizontal well staged fracturing technology has become the main technology for unconventional oil and gas development.

[0003] Shale gas, as a typical unconventional oil and gas reservoir resource, is characterized by low porosity and extremely low matrix permeability. Implementing staged fracturing in horizontal wells has become a key technology for achieving efficient development of shale gas reservoirs. Cluster perforation and staged fracturing technology have become key technologies for the development of shale gas horizontal wells. This technology achieves volumetric fracturing by fracturing in stages within the horizontal well, thereby increasing shale gas production.

[0004] Currently, due to the combined effects of multiple factors such as casing quality, wellbore quality, cementing quality, changes in in-situ stress, tectonic movements, and the highly variable stress during horizontal well fracturing, casing damage is becoming increasingly frequent and severe, which will seriously affect the development progress of unconventional reservoirs. Existing horizontal well stimulation methods mostly employ bridge plug perforation combined fracturing and coiled tubing bottom-sealed drag fracturing. In casing-damaged horizontal wells, the inability of the tool string to pass through the damaged area means that the stimulation section below the damaged section cannot be stimulated, or can only be stimulated using temporary plugging and redirection techniques. However, this technique has limited segmented effectiveness and is prone to single-layer surges. Therefore, a reservoir stimulation method specifically for casing-damaged horizontal wells is urgently needed.

[0005] Chinese patent document CN 112696184B discloses a method for fracturing oil and gas wells, and Chinese patent document CN 105672970B discloses a method for achieving temporary plugging and diversion fracturing in horizontal well sections. Both of these Chinese patent documents adopt temporary plugging and diversion technology for existing reservoir stimulation techniques in damaged horizontal wells. However, this technology suffers from problems such as significant differences between different stimulation sections, excessively high costs, and inability to achieve refined stimulation. Summary of the Invention

[0006] This invention provides a method for reservoir stimulation in horizontal wells with deformed coiled tubing casing, which overcomes the shortcomings of the prior art and can effectively solve the problem that existing horizontal wells with deformed coiled tubing casing cannot be finely stimulated.

[0007] The technical solution of this invention is achieved through the following measures: A method for reservoir stimulation in a horizontal well with deformed casing of coiled tubing includes the following steps: First, a reservoir stimulation tool string is installed at the lower end of the coiled tubing. The reservoir stimulation tool string includes an upper centralizer, a directional device, a pulse generator, a spray gun assembly, a lower centralizer, and a guide shoe, which are fixedly installed together from top to bottom. The coiled tubing is lowered to deliver the reservoir stimulation tool string to the target formation. The directional device achieves horizontal well orientation and angle determination. The pulse generator is equipped with a pulse booster, which can convert continuous and stable flow into periodic waves. The process involves three steps: First, a pulsed flow of fluid is generated, with at least one nozzle evenly spaced on the outer side of the spray gun. Second, high-pressure abrasive fluid is pumped into the coiled tubing. This fluid is then ejected at high speed from multiple nozzles in the pulse generator and spray gun assembly, penetrating the casing and cement sheath to form a channel of a specific shape in the formation. Third, high-pressure fluid is injected into the annulus to increase the bottom hole pressure. Due to the high-speed jet from the spray gun assembly creating a low-pressure area at the nozzle outlet, the high-pressure fluid injected into the annulus flows towards this low-pressure area, thus sealing off the fracturing process. The channel will then initiate and extend under the combined pressure of the fluid in the tubing and the annulus at the injection point.

[0008] The following are further optimizations and / or improvements to the above-mentioned technical solution: The aforementioned orientation device may include an upper connector, an upper outer cylinder, a lower outer cylinder, a track tube, a guide ball, and a lower connector. The upper end of the upper connector is fixedly installed together with the lower end of the upper centralizer. The lower outer side of the upper connector is sealed and fixedly installed together with the upper inner side of the upper outer cylinder. The lower inner side of the upper outer cylinder is fixedly installed together with the upper outer side of the lower outer cylinder. A track tube, with its lower end sealed and passing through the lower outer cylinder, is fitted inside the upper outer cylinder at the position corresponding to the lower end of the upper connector. The upper outer side of the track tube is in sealed contact with the upper inner side of the upper outer cylinder. The track tube has a vertically penetrating, tapered throttling channel with a larger upper section and a smaller lower section. An outer annular groove is provided on the upper outer side of the track tube at the position corresponding to the upper outer cylinder. A guide ball is installed in the outer annular groove. At least one spiral guide groove is evenly distributed around the circumference on the upper outer side of the track tube. The lower end of each guide groove is connected to... The upper end of the outer ring groove is connected. An outer ring platform is fixed on the outside of the track tube at the position between the lower side of the outer ring groove and the upper end of the lower outer cylinder. An arc-shaped limiting groove with an opening facing inward is provided on the inner side of the upper end of the lower outer cylinder, which corresponds to the lower end of the guide groove. The outer side of the lower end of the track tube at the position below the lower outer cylinder is fixedly installed together with the inner side of the upper part of the lower connector. The lower end of the lower connector is fixedly connected to the upper end of the pulse generator. An inner ring platform is fixed on the outer side of the lower end of the lower outer cylinder. At least one sealing ring is provided at intervals between the inner side of the upper part of the inner ring platform and the outer side of the track tube, and between the outer side of the upper end of the track tube and the inner side of the upper part of the upper outer cylinder. A shearing hole is provided on the outer side of the lower part of the track tube below the lowest sealing ring. A radially penetrating shearing screw hole is provided on the outer side of the lower part of the lower outer cylinder at the position of the shearing hole. A shearing pin with its end located in the shearing hole is screwed into the shearing screw hole.

[0009] This invention enhances the maneuverability of the tool string by optimizing the reservoir stimulation tool string; it generates a low-pressure area at the nozzle by using a high-speed jet in the spray gun assembly, which promotes the entry of high-pressure fluid in the annulus into the target layer for fracturing, thus achieving isolation of the fracturing process without the need for mechanical isolation devices; and it converts continuous and stable flow into periodic oscillating pulse flow by setting a pulse energy enhancement device on the pulse generator, which has the characteristics of stability, high efficiency and good permeability. Attached Figure Description

[0010] Appendix Figure 1 This is a schematic diagram of the main cross-sectional structure of Embodiments 1 and 2 of the present invention.

[0011] Appendix Figure 2 For the appendix Figure 1 A schematic diagram of the front cross-sectional structure of the central orientation device.

[0012] Appendix Figure 3 For the appendix Figure 2 A top view of the lower outer cylinder.

[0013] Appendix Figure 4 For the appendix Figure 1 A schematic diagram of the structure of the medium pulse generator.

[0014] The codes in the attached diagram are as follows: 1 is the lower outer cylinder, 2 is the track tube, 3 is the lower connector, 4 is the guide ball, 5 is the throttling channel, 6 is the outer ring groove, 7 is the guide groove, 8 is the outer ring platform, 9 is the inner ring platform, 10 is the sealing ring, 11 is the shear pin, 12 is the mounting pin, 13 is the guide shoe, 14 is the arc-shaped limiting groove, 15 is the upper connector, 16 is the upper outer cylinder, 17 is the upper stabilizer, 18 is the pulse generator, 19 is the pulse booster, 20 is the spray gun assembly, 21 is the nozzle, and 22 is the lower stabilizer. Detailed Implementation

[0015] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0016] In this invention, for ease of description, the description of the relative positions of the components is based on the appendix to the specification. Figure 1 The layout is described using a diagrammatic method, such as front, back, top, bottom, left, right, etc. The positional relationships are determined based on the layout direction of the attached diagram in the instruction manual.

[0017] The present invention will be further described below with reference to embodiments and accompanying drawings: Example 1: As shown in the attached document Figure 1 , 2As shown in Figures 3 and 4, the method for reservoir stimulation in a horizontal well with casing deformation of coiled tubing includes the following steps: First, a casing-damaged reservoir stimulation tool string is installed at the lower end of the coiled tubing. The tool string includes, from top to bottom, an upper centralizer 17, a directional device, a pulse generator 18, a spray gun assembly 20, a lower centralizer 22, and a guide shoe 13, all fixedly installed together. The coiled tubing is lowered to deliver the tool string to the target formation. The directional device achieves horizontal well orientation and angle determination. The pulse generator 18 is equipped with a pulse booster 19, which converts continuous, stable flow into periodically fluctuating pulse flows. The first step involves pumping high-pressure abrasive fluid into the coiled tubing. This high-pressure abrasive fluid is then ejected at high speed from the pulse generator 18 and the multiple nozzles 21 of the spray gun assembly 20, penetrating the casing and cement sheath to form a channel of a certain shape in the formation. The second step involves injecting high-pressure fluid into the annulus to increase the bottom hole pressure. Because the high-speed jet from the spray gun assembly 20 creates a low-pressure area at the nozzle 21 outlet, the high-pressure fluid injected into the annulus flows towards this low-pressure area, thus sealing off the fracturing process. The channel will initiate and extend at the injection position under the combined pressure of the tubing and the annulus fluid.

[0018] In use, this invention utilizes a series of tools, including a self-developed directional device, a pulse generator 18, and a spray gun assembly 20, to match the process. By setting the directional device, circumferential directional and angled perforation modification of horizontal wells can be achieved. By setting the pulse generator 18, the pulsed fluid at the outlet end can achieve energy enhancement within the perforation orifice during fracturing, increasing the propagation distance of the jet pressure wave along the perforation direction and guiding the fracturing fluid in the annulus along a predetermined direction. It features adjustable frequency and amplitude, strong erosion resistance, and can also use existing known pulse generators 18. The downhole pulse booster device 19 converts continuous and stable flow into periodic oscillating pulse flow, thereby obtaining higher pulse impact pressure. When the impact frequency coincides with the natural frequency of the object, a resonance phenomenon can be generated, achieving a better impact crushing effect. By setting up the spray gun assembly 20, a low-pressure area can be generated at its nozzle 21 by relying on high-speed jet, which can promote the high-pressure fluid in the annulus to enter the target layer of the operation, achieving the isolation of the fracturing process without the need for mechanical isolation devices. It meets the requirements of a cumulative sand throughput of 60m³ for a single nozzle 21 and strong erosion resistance. It can also use existing known spray gun devices.

[0019] In the first step mentioned above, the minimum diameter of the casing damage reservoir stimulation tool string can be 25.4 mm, which solves the problem of the process tubing's passability.

[0020] In the second step above, a downhole pulse booster device 19 is designed by establishing a "pulse + spray gun" model.

[0021] In the third step above, according to Bernoulli's law of conservation of energy, when the jet energy remains constant, the higher the jet velocity, the lower the pressure. The fluid is ejected through nozzle 21, and the jet velocity is the highest and the pressure is the lowest at the outlet of nozzle 21. As the jet moves forward, its velocity gradually decreases and its pressure increases due to the influence of the surrounding medium. Therefore, the high-speed jet can generate a low-pressure area at the outlet of nozzle 21, and its pressure is the lowest value in the downhole flow field. Under pressure control, the high-pressure fluid injected into the annulus will inevitably flow to this low-pressure area and will not enter the fractures of the fractured section. After the annulus fluid enters this area, it is carried into the formation by the viscosity of the jet fluid, maintaining the fracture propagation.

[0022] This invention is a reservoir stimulation technology developed through theoretical research and field practice, based on the theories of triaxial stress rock mechanics, hydrodynamics, and mechanical tool operation. The technology is grounded in the elastoplastic constitutive model of rocks, incorporating the rock's pulse dynamic pressure resonance response characteristics with the triaxial stress and physical parameters of the formation. It also integrates hydrodynamic principles such as Bernoulli's equation, innovatively proposing the pressure drop cycle theory and the dual-combination pressure system theory. Furthermore, it has developed a series of customized reservoir stimulation tools, achieving volumetric stimulation under small-diameter conditions that features limited perforation, increased speed, increased pressure, precision, differentiation, and balance. This results in "high throughput, effective hydraulic isolation, pulse-pressurized perforation fracturing initiation, and precision," maximizing the complexity of the fracture network in damaged horizontal wells and enabling precise and differentiated "dense cutting" stimulation, thereby maximizing the seepage area and flow capacity. Currently, this technology has been successfully applied to 17 wells, with all 17 wells showing effectiveness, resulting in an average increase in crude oil production of 20 t / d per well.

[0023] The above-mentioned method for reservoir stimulation in horizontal wells with coiled tubing casing deformation can be further optimized and / or improved according to actual needs: Example 2: As shown in the attached document Figure 1 , 2As shown in Figures 3 and 4, the orientation device includes an upper connector 15, an upper outer cylinder 16, a lower outer cylinder 1, a track tube 2, a guide ball 4, and a lower connector 3. The upper end of the upper connector 15 is fixedly installed together with the lower end of the upper stabilizer 17. The lower outer side of the upper connector 15 is sealed and fixedly installed together with the upper inner side of the upper outer cylinder 16. The lower inner side of the upper outer cylinder 16 is fixedly installed together with the upper outer side of the lower outer cylinder 1. A track tube 2, which passes through the lower outer cylinder 1 and is located below the lower outer cylinder 1, is fitted inside the upper outer cylinder 16 at the lower end of the upper connector 15. The upper outer side of the track tube 2 is in sealed contact with the upper inner side of the upper outer cylinder 16. The track tube 2 has a tapered throttling channel 5 that runs vertically through the upper part and is wider at the top and narrower at the bottom. An outer ring groove 6 is provided on the upper outer side of the track tube 2 at the position above the lower outer cylinder 1. A guide ball 4 is installed in the outer ring groove 6. At least one spiral guide groove 7 is evenly distributed around the circumference on the upper outer side of the track tube 2. The lower end of the guide groove 7 is connected to the upper end of the outer ring groove 6. The outer ring platform 8 is fixed on the outside of the track tube 2 at the position between the lower side of the outer ring groove 6 and the upper end of the lower outer cylinder 1. The inner side of the upper end of the lower outer cylinder 1 is provided with an arc-shaped limiting groove 14 that corresponds to the lower end of the guide groove 7 and opens inward. The outer side of the lower end of the track tube 2 at the position below the lower outer cylinder 1 is fixedly installed together with the inner side of the upper part of the lower connector 3. The lower end of the lower connector 3 is fixedly connected to the upper end of the pulse generator 18. The outer side of the lower end of the lower outer cylinder 1 is fixed with an inner ring platform 9. At least one sealing ring 10 is provided at intervals between the inner side of the upper part of the inner ring platform 9 and the outer side of the track tube 2, and between the outer side of the upper end of the track tube 2 and the inner side of the upper part of the upper outer cylinder 16. The outer side of the lower part of the track tube 2 is provided with a shearing hole located below the lowest sealing ring 10. The outer side of the lower part of the lower outer cylinder 1 at the position of the shearing hole is provided with a radially penetrating shearing screw hole. A shearing pin 11 with its end located in the shearing hole is screwed into the shearing screw hole.During use, the upper part of the throttling channel 5 is tapered, wider at the top and narrower at the bottom, which throttles the fluid entering the inner side of the upper part of the track pipe 2. The fluid's action on the inner side of the upper part of the track pipe 2 causes the track pipe 2 to move downward within the upper outer cylinder 16. After the self-adjusting directional device enters the horizontal well section, the guide ball 4 first rolls down to the lowest point of the outer annular groove 6 under the action of gravity. Then, under the action of the fluid within the track pipe 2, the track pipe 2 shears the shear pin 11 and moves towards the end away from the wellhead. Then, under the action of the outer annular groove 6, the guide ball 4 rolls to the corresponding position of the arc-shaped limiting groove 14. The track pipe 2 continues to move, and the guide ball 4 moves to the corresponding position of the guide groove 7. Then, under the constraint of the arc-shaped limiting groove 14, the guide ball 4 continues to move relative to the track pipe 2 within the guide groove 7. At the same time, because the guide ball 4 is constrained by the arc-shaped limiting groove 14, the guide ball... 4. When the guide ball 4 moves relative to the spiral guide groove 7 in the track pipe 2, the track pipe 2 rotates. When the guide ball 4 moves to the end of the guide groove 7 away from the outer ring groove 6, the guide ball 4 and the fluid in the track pipe 2 act together on the track pipe 2, which plays a directional role on the track pipe 2. It also causes the pulse generator 18 and the spray gun assembly 20 connected to the track pipe 2 to rotate, thereby positioning the nozzle 21 angle of the spray gun assembly 20. At least one spiral guide groove 7 is evenly distributed along the circumference on the upper outer side of the track pipe 2. The inner side of the upper end of the lower outer cylinder 1, corresponding to the lower end of the outer ring platform 8, is provided with an arc-shaped limiting groove 14 that corresponds to the lower end of the guide groove 7 and opens inward. This setting can realize the rotation of the track pipe 2 at a set angle in the horizontal well section, and it can also realize the rotation of the track pipe 2 at a set angle in the vertical well section, which has a wide range of applications. By setting the shear pin 11, the track pipe 2 can be better fixed and positioned. It can also facilitate the marking of the reference azimuth line of the self-adjusting orienter, prevent the tool string from rotating when it is lowered into the well, and improve the positioning accuracy.

[0024] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method for reservoir stimulation in a horizontal well with deformable coiled tubing casing, characterized in that... The steps are as follows: First, the casing damage reservoir stimulation tool string is installed at the lower end of the coiled tubing. The casing damage reservoir stimulation tool string includes, from top to bottom, an upper centralizer, a directional device, a pulse generator, a spray gun assembly, a lower centralizer, and a guide shoe. The coiled tubing is lowered to deliver the casing damage reservoir stimulation tool string to the target formation. The directional device enables horizontal well orientation and angle determination. The pulse generator is equipped with a pulse booster, which converts continuous and stable flow into periodic pulsating flow. At least one nozzle is evenly distributed on the outer side of the spray gun. Second, high-pressure abrasive fluid is pumped into the coiled tubing. The high-pressure abrasive fluid flows through the coiled tubing and from the pulse... The nozzles of the fracturing generator and the spray gun assembly eject at high speed, piercing the casing and cement sheath to form a channel of a certain shape in the formation. The third step involves injecting high-pressure fluid into the annulus to increase the bottom hole pressure. Because the high-speed jet from the spray gun assembly creates a low-pressure area at the nozzle outlet, the high-pressure fluid injected into the annulus flows towards this low-pressure area, achieving isolation during the fracturing process. The channel will initiate and extend at the injection point under the combined pressure of the tubing and the annulus fluids. The aforementioned directional device includes an upper connector, an upper outer cylinder, a lower outer cylinder, a track tube, a guide ball, and a lower connector. The upper end of the upper connector is fixedly installed with the lower end of the upper centralizer, and the lower outer side of the upper connector is sealed and fixedly installed with the upper inner side of the upper outer cylinder. Together, the inner lower part of the upper outer cylinder and the outer upper part of the lower outer cylinder are fixedly installed together. A track tube, with its lower end sealed and passing through the lower outer cylinder, is fitted inside the inner side of the upper outer cylinder at the lower end of the upper connector. The outer upper end of the track tube is in sealed contact with the inner upper part of the upper outer cylinder. The track tube has a vertically connected, tapered throttling channel that is wider at the top and narrower at the bottom. An outer annular groove is provided on the outer upper part of the track tube at the position above the lower outer cylinder. A guide ball is installed in the outer annular groove. At least one spiral guide groove is evenly distributed around the circumference on the outer upper part of the track tube. The lower end of each guide groove communicates with the upper end of the outer annular groove. An outer annular platform is fixed to the outer side of the track tube at the position between the lower side of the outer annular groove and the upper end of the lower outer cylinder. The inner side of the upper end of the lower outer cylinder is provided with an arc-shaped limiting groove that corresponds to the lower end of the guide groove and opens inward. The outer side of the lower end of the track tube corresponding to the position below the lower outer cylinder is fixedly installed together with the inner side of the upper part of the lower connector. The lower end of the lower connector is fixedly connected to the upper end of the pulse generator. An inner ring platform is fixed on the outer side of the lower end of the lower outer cylinder. At least one sealing ring is provided at intervals between the inner side of the upper part of the inner ring platform and the outer side of the track tube, and between the outer side of the upper end of the track tube and the inner side of the upper part of the upper outer cylinder. A shearing hole is provided on the outer side of the lower part of the track tube below the lowest sealing ring. A radially penetrating shearing screw hole is provided on the outer side of the lower part of the lower outer cylinder corresponding to the position of the shearing hole. A shearing pin with its end located in the shearing hole is screwed into the shearing screw hole.

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