Ground simulation test method for printing fractures in wellbore walls

Abstract

The present invention discloses a ground simulation test method for wellbore fracture printing, and the steps are as follows: fabricate a granite cylinder with cracks cut on the inner wall, and fabricate a wellhead cover plate, an upper cover plate and a well bottom plate; pour a concrete base at the bottom of the well pit and embed the well bottom plate; install the wellbore section by section on the well bottom plate; cover the wellhead with a wooden formwork and fix the embedded bolts; tie a steel reinforcement cage around the wellbore and pour concrete; after reaching the strength, remove the wooden formwork, screw on the upper joint at the upper end of the printing device and weld the central vertical pipe; lift the printing device and place it into the inner cavity of the wellbore and at the center of the well bottom plate; install the wellhead cover plate, and then cover the upper cover plate on the wellhead cover plate; install an in-cylinder pressure gauge on the central vertical pipe and connect it to the in-cylinder water injection pipe through the in-cylinder water injection valve, and install an annulus pressure gauge on the eccentric vertical pipe and connect it to the annulus water injection pipe through the annulus water injection valve; apply pressure to the well to conduct wellbore fracture printing on the printing device. The present invention can verify the wellbore printing action and effect and obtain printing parameters.

Description

Technical Field

[0001] The present invention relates to the printing of fractures in oil drilling, and particularly to a ground simulation test method for printing wellbore fissures, belonging to the technical field of drilling tool tests. Background Art

[0002] In the research work of oil exploration, oil production and drilling engineering, it is of great significance to figure out the shape, size and distribution of formation fractures on the wellbore. There are various methods to obtain the physical data of wellbore fractures. Among them, the Chinese invention patent application with publication number CN109162710A discloses a wellbore fissure printing device, including: an inner frame structure body, which has a central channel, and at least one mounting ring groove is arranged on the inner frame structure body along the axial direction; at least one printing mechanism, which is movably installed in at least one mounting ring groove in the radial direction, the printing mechanism has at least three mounting supports arranged along the circumferential direction, and printing structure layers are arranged on the outer sides of the mounting supports. This wellbore fissure printing device can obtain the fractures and holes of different lithologies in the formation on the wellbore, and parameters such as their shape, length, width, quantity distribution and direction, etc. The device has a simple structure and is convenient to operate.

[0003] This wellbore fracture printing device has not been able to actually be lowered into the well for printing so far. The main reasons are as follows: 1. The printing effect has not been verified on the ground, the printing parameters cannot be determined, and the risk of directly carrying out downhole operations is too high.

[0004] 2. Because during the drilling process, the complex fractures in the wellbore or the oil storage fractures in fractured reservoirs mostly exist in relatively hard and deeply buried rock formations such as granite, diabase, limestone, etc., and their sizes, quantities and orientations are different. The shallow formations are mostly mudstones with low hardness and few fractures, which are not easy to print. If the printing device is directly lowered into a deep well for printing, the rationality and reliability of the printing device during the movement of the mechanism cannot be observed, and the cycle is long, which is easy to cause downhole accidents.

[0005] Generally, the Mohs hardness of lead is 1.5, the density is 11.3437 g / cm³, the temperature resistance can reach above 220 °C, and the melting point is 327 °C. In the construction of salvaging downhole objects on site, for a wellbore with a diameter of Φ215.9 mm, a lead mold with a diameter of Φ200 mm is used, and a pressure of 5 T is required to print the surface shape of the downhole object at the bottom of the well, and the pressure is 1.56 MPa. However, ground tests have shown that different from printing sharp objects facing upwards in the well with a lead mold, there is no gravity of the drill string during wellbore printing, and there is paste-like drilling fluid adhering to the surface. The experience of printing sharp objects in the well cannot be applied to printing wellbore fissures.

[0006] After the traditional crack printing device completes the printing of the lead mold at the top of the piston, in many cases, the piston cannot retract into the cylinder block, exposing the printing surface of the lead mold outside the circumference of the tool. During the lifting process, it is easy to scrape against the wellbore wall, causing wear to the printing marks, and even the lead mold may fall off or get stuck at the wellbore step. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems existing in the prior art and provide a ground simulation test method for wellbore crack printing, which can more realistically simulate the downhole environment, verify the printing action and effect of the wellbore wall on the ground, and obtain accurate printing parameters.

[0008] To solve the above technical problems, a ground simulation test method for wellbore crack printing of the present invention successively includes the following steps:

[0009] S1. Fabricate multiple sections of granite cylinder rings for the simulated wellbore, and simulate cracks are cut on the inner walls of each granite cylinder ring;

[0010] S2. Fabricate the wellhead cover plate and the upper cover plate for closing the wellhead. An eccentric vertical pipe and a temperature measuring sleeve are welded on the wellhead cover plate, and the well bottom plate is welded and fabricated;

[0011] S3. Dig a well pit on the ground, pour a concrete base at the bottom of the pit, and horizontally embed the well bottom plate at the top center of the concrete base;

[0012] S4. After the concrete base solidifies, stack the granite cylinder rings on the well bottom plate one by one to form a bamboo joint wellbore;

[0013] S5. Cover a wooden mold on the upper port of the bamboo joint wellbore. The wooden mold is provided with wooden mold reamed holes corresponding one by one to the flange bolt holes of the wellhead cover plate, and each embedded bolt passes through and is fixed in the corresponding wooden mold reamed hole from bottom to top;

[0014] S6. Tie a steel reinforcement cage around the outer circumference of the bamboo joint wellbore, and then pour concrete;

[0015] S7. After the reinforced concrete reaches the strength, remove the wooden mold, and screw and connect a cylinder upper joint at the upper end of the printing device. A central vertical pipe extending upward is welded at the upper port of the central hole of the cylinder upper joint;

[0016] S8. Lift the printing device and place it into the inner cavity of the bamboo joint wellbore and at the center of the well bottom plate;

[0017] S9. Install the wellhead cover plate, and then cover the upper cover plate on the wellhead cover plate;

[0018] S10. Install an in-cylinder pressure gauge on the central vertical pipe and connect it to an in-cylinder water injection pipe through an in-cylinder water injection valve, and install an annulus pressure gauge on the eccentric vertical pipe and connect it to an annulus water injection pipe through an annulus water injection valve;

[0019] S11. Pressurize downhole through the in-tube water injection valve and the annulus water injection valve to perform wellbore fracture printing on the printing device.

[0020] As an improvement of the present invention, in step S2, a bottom plate anchor claw embedded in the reinforced concrete is welded to the lower end surface of the well bottom plate, and a cylinder positioning ring erected upward is welded to the outer periphery of the well bottom plate; in step S4, the lower end of the bottom granite cylinder ring is embedded in the cylinder positioning ring.

[0021] As a further improvement of the present invention, a center positioning ring is welded to the center of the upper end surface of the well bottom plate, and a rubber cone sleeve is embedded in the inner cavity of the center positioning ring. In step S8, the cylinder male joint at the lower end of the printing device is inserted into the rubber cone sleeve and is mutually adapted.

[0022] As a further improvement of the present invention, in step S4, cylinder ring positioning holes are respectively provided at the butting ports of adjacent granite cylinder rings, and cylinder ring positioning pins are respectively inserted into the cylinder ring positioning holes to achieve accurate positioning between the upper and lower granite cylinder rings.

[0023] As a further improvement of the present invention, in step S3, a heating device is installed at the center of the upper end surface of the well bottom plate, and the power supply cable of the heating device is located in the heating cable sleeve; the lower end of the temperature measuring sleeve is closed and the upper end is open, and a thermal resistance probe is installed in the inner cavity of the temperature measuring sleeve.

[0024] As a further improvement of the present invention, in step S9, the center of the top surface of the wellhead cover plate and the outer periphery of the upper cover plate center hole are mutually sealed through a well cover sealing ring, and then fastening nuts and cap nuts are screwed onto the upper ends of the embedded bolts to fix the wellhead cover plate and the upper cover plate 5 at the wellhead, and then the outer periphery of the center vertical pipe is welded to the upper port of the upper cover plate center hole.

[0025] As a further improvement of the present invention, a printing section is provided in the middle of the cylinder of the printing device. A plurality of lead mold supports are evenly provided on the outer periphery of the cylinder of the printing section. A lead mold is respectively attached to the outer wall of each lead mold support. Each lead mold support is driven by a plurality of pistons. Each piston is respectively embedded in a radial hole of the cylinder. An upper core shaft is provided in the central hole of the cylinder. A piston inclined surface is respectively provided at the inner end of each piston. The piston inclined surfaces of the pistons located on the same circumference respectively abut against the wedge-shaped inclined surfaces on the outer periphery of the same cone sleeve. Each of the cone sleeves is sequentially sleeved and fixed on the outer periphery of the upper core shaft. The wedge-shaped inclined surfaces on each of the cone sleeves are centrally symmetrically arranged and the lower ends are respectively inclined towards the axis direction of the cylinder; dovetail grooves are respectively provided on the wedge-shaped inclined surfaces of the cone sleeves, and dovetail tenons are respectively provided on the piston inclined surfaces of the pistons. The dovetail tenons are respectively embedded in the corresponding dovetail grooves.

[0026] As a further improvement of the present invention, the upper end of the upper mandrel is provided with an enlarged-diameter upper mandrel sealing section, and a ball seat is provided at the upper end of the central hole of the upper mandrel. A steel ball is seated on the ball seat. A return spring is provided below the step of the upper mandrel sealing section. The lower end of the return spring is supported on a spring seat, and the spring seat is fixed on the cylinder body.

[0027] As a further improvement of the present invention, the lower end of the upper mandrel is screwed with a lower mandrel. The upper end of the lower mandrel is provided with a large end of the lower mandrel. The large end of the lower mandrel abuts against the bottom of the lowermost cone sleeve. The lower end of the lower mandrel is inserted into a guide sleeve, and the guide sleeve is fixed in the inner cavity of the cylinder body.

[0028] As a further improvement of the present invention, an upper cylinder step is provided above the printing section, and a lower cylinder step is provided below the printing section. The outer walls of the lead molds are located within the axial projection ranges of the upper cylinder step and the lower cylinder step.

[0029] As a further improvement of the present invention, a plurality of cameras are provided in the upper part of the inner cavity of the bamboo joint wellbore, and each camera monitors the actions of the corresponding lead mold respectively.

[0030] As a further improvement of the present invention, three or four lead molds are symmetrically arranged in the circumferential direction, and the simulated crack widths of the inner walls of the wellbore faced by each lead mold are different; the simulated cracks are formed by cutters of different specifications; or a wider notch is first cut on the inner wall of the wellbore with a cutter, and then glue is filled in the notch, a metal sheet is added in the center of the glue, and the metal sheet is withdrawn before the glue solidifies, and different-width simulated cracks are formed after the glue solidifies.

[0031] As a further improvement of the present invention, step S11 includes the following sub-steps:

[0032] Step S11.1: Set the simulated well depth. According to the simulated well depth and the density of the drilling fluid, calculate the hydrostatic pressure P_liquid column at the corresponding well depth, and determine the test pressure value P_test in the wellbore;

[0033] Step S11.2: Fill the bamboo joint wellbore with water through the annulus water injection valve and the in-cylinder water injection valve, and evacuate the gas at the top of the wellbore;

[0034] Step S11.3: Pressurize the pressure in the annulus of the printing device to be equal to P_liquid column through the annulus water injection pipe, and raise the water temperature to be the same as that of the simulated well section;

[0035] Step S11.4: Pressurize the pressure in the inner cavity of the printing device to the starting value of P_test through the in-cylinder water injection pipe. The upper mandrel drives each cone sleeve to move downward. The dovetail on the piston slope slides upward along the dovetail groove on the cone sleeve. The wedge slope of the cone sleeve and the piston slope slide relative to each other. The piston pushes the lead mold outwards, and the lead mold presses on the inner wall of the wellbore for printing;

[0036] Step S11.5: Reduce the internal cavity pressure of the printing device to be equal to P liquid column, so that the pressure inside and outside the tool is balanced. The return spring pushes the upper mandrel upward. The upper mandrel drives each cone sleeve to move upward. The dovetail tenons on the piston slope slide downward along the dovetail grooves on the cone sleeves. The lead mold and the lead mold support retract to the outer periphery of the printing section of the cylinder body.

[0037] Step S11.6: First, relieve the pressure of the water injection pipe in the cylinder, and then relieve the pressure of the annulus water injection pipe. Dismantle the wellhead facilities, lift out the printing device, and observe the printing pattern of the lead mold.

[0038] As a further improvement of the present invention, in step S11.6, if only the printing pattern of the widest crack is clear, determine the printing pressure of the widest crack as P test; if the printing patterns of cracks with medium width and above are clear, determine the printing pressure of the medium-width crack as P test; if the printing pattern of the narrowest crack is clear, determine the printing pressure of the narrowest crack as P test.

[0039] As a further improvement of the present invention, in step S11.6, if the printing patterns of all lead molds are not clear, after repairing the lead mold and reassembling the test device, increase the test pressure value in the wellbore in step S11.1 by 5 MPa as the new P test, and continue the test.

[0040] Compared with the prior art, the present invention has the following beneficial effects: 1. It can verify the reliability of the piston push and retract actions of the new printing device on the ground;

[0041] 2. Since different types of media can be used in the granite jointed wellbore, cameras can be installed to observe the movement of the mechanism of the printing device underground;

[0042] 3. The inner walls of each granite cylinder ring are cut with simulated cracks. The experiment is simple and rapid. The lead mold can be reused. Problems are easy to handle. The cycle is short and the cost is low. It is convenient to verify the best printing parameters and reduce the risk of downhole operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The following further describes the present invention in detail with reference to the drawings and specific embodiments. The drawings are only provided for reference and illustration, and are not intended to limit the present invention.

[0044] Figure 1 It is a cross-sectional view of the printing device in the present invention;

[0045] Figure 2 It is a three-dimensional view of the piston in the printing device;

[0046] Figure 3 It is a three-dimensional view of the cone sleeve in the printing device;

[0047] Figure 4 It is a cross-sectional view of the bamboo joint wellbore in the present invention;

[0048] Figure 5 It is the front view of the well bottom plate in the present invention;

[0049] Figure 6 It is a schematic diagram after casting reinforced concrete on the outer periphery of the bamboo joint wellbore;

[0050] Figure 7 It is a schematic structural diagram of the well perimeter crack printing simulation test device in the present invention;

[0051] Figure 8 is Figure 7 an enlarged view of the upper part.

[0052] In the figure: 1. Printing device; 1a. Tapered female thread; 1b. Upper step of the cylinder; 1c. Lower step of the cylinder; 1d. Male joint of the cylinder; 1e. Upper mandrel; 1e1. Sealing section of the upper mandrel; 1e2. Ball seat; 1f. Cone sleeve; 1f1. Wedge-shaped inclined surface; 1f2. Dovetail groove; 1g. Piston; 1g1. Piston inclined surface; 1g2. Dovetail tenon; 1h. Return spring; 1j. Spring seat; 1j1. Spring seat locking pin; 1k. Lower mandrel; 1k1. Large end of the lower mandrel; 1m. Guide sleeve; 1m1. Guide sleeve locking pin; 1n. Lead mold support; 1p. Lead mold; 2. Bamboo joint wellbore; 2a. Cylinder ring positioning pin; 2b. Simulated crack; 3. Well bottom plate; 3a. Bottom plate anchor claw; 3b. Cylinder positioning ring; 3c. Center positioning ring; 3d. Rubber cone sleeve; 4. Wellhead cover plate; 4a. Embedded bolt; 4b. Temperature measuring sleeve; 4c. Well cover sealing ring; 5. Upper cover plate; 6. Upper joint of the cylinder; 7. Inner cylinder water injection pipe; 7a. Inner cylinder water injection valve; 7b. Inner cylinder pressure gauge; 7c. Central vertical pipe; 8. Annulus water injection pipe; 8a. Annulus water injection valve; 8b. Annulus pressure gauge; 8c. Eccentric vertical pipe; 9. Heating device; 10. Heating cable sleeve; 11. Reinforced concrete. Detailed implementation manners

[0053] In the following description of the present invention, the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating that the device must have a specific orientation.

[0054] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below with reference to specific drawings.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the specification of this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention.

[0056] As Figures 1 to 3 shown, at the upper end of the cylinder body of the printing device 1 tested in the present invention, there is a tapered female thread 1a, and the tapered female thread 1a is screwed onto the drill pipe above; at the lower end of the cylinder body, there is a cylinder male joint 1d, and the cylinder male joint 1d is screwed onto the drill pipe below. In the middle of the cylinder body, there is a printing section. On the outer periphery of the cylinder body of the printing section, a plurality of lead mold supports 1n are evenly arranged. On the outer walls of the respective lead mold supports 1n, lead molds 1p are respectively attached, and the lead molds 1p can be directly cast on the lead mold supports 1n. The outer wall arc surface of the lead mold 1p coincides with the outer circumferences of the upper and lower cylinder bodies, and the inner wall of the lead mold support 1n coincides with the outer circumference of the cylinder body of the printing section.

[0057] The inner walls of the respective lead mold supports 1n are respectively driven by a plurality of pistons 1g, and the respective pistons 1g are respectively embedded in the radial holes of the cylinder body. For example, each lead mold support 1n is driven by five pistons 1g in the height direction, and three or four lead molds 1p are usually evenly arranged in the circumferential direction of the printing section.

[0058] In the central hole of the cylinder body, there is an upper mandrel 1e. At the inner end of each piston 1g, there is a piston inclined surface 1g1. The piston inclined surfaces 1g1 of the pistons 1g located on the same circumference respectively abut against the wedge-shaped inclined surfaces 1f1 on the outer periphery of the same tapered sleeve 1f. The respective tapered sleeves 1f are sequentially sleeved and fixed on the outer periphery of the upper mandrel 1e. The top of the uppermost tapered sleeve 1f abuts against the lower side of the step of the upper mandrel 1e, and the respective tapered sleeves 1f are sequentially stacked. The wedge-shaped inclined surfaces 1f1 on the respective tapered sleeves 1f are symmetrically arranged about the center and the lower ends thereof are respectively inclined towards the axis of the cylinder body; on the wedge-shaped inclined surfaces 1f1 of the tapered sleeves 1f, there are respectively dovetail grooves 1f2. On the piston inclined surfaces 1g1 of the pistons 1g, there are respectively dovetail tenons 1g2, and the dovetail tenons 1g2 are respectively embedded in the corresponding dovetail grooves 1f2 and can slide along the dovetail grooves 1f2.

[0059] When the upper mandrel 1e drives the respective tapered sleeves 1f to move downward, relative sliding occurs between the wedge-shaped inclined surfaces 1f1 of the tapered sleeves 1f and the piston inclined surfaces 1g1. Since the pistons 1g are restricted in the radial holes of the cylinder body, the pistons 1g can only slide outward along the radial holes, and the distance between the pistons 1g and the axis of the cylinder body increases, pushing the lead mold supports 1n outward. At the same time, the dovetail tenons 1g2 on the piston inclined surfaces 1g1 slide relatively towards the large end, i.e., the upper end, of the wedge-shaped inclined surfaces 1f1 along the dovetail grooves 1f2 on the tapered sleeves 1f.

[0060] The upper end of the upper mandrel 1e is provided with an enlarged-diameter upper mandrel sealing section 1e1, and at least two sealing rings are embedded on the outer periphery of the upper mandrel sealing section 1e1 to achieve sealing with the inner wall of the cylinder body. At the upper end of the central hole of the upper mandrel, there is a ball seat 1e2, and the ball seat 1e2 is a flared opening that is wider at the top and narrower at the bottom, which is convenient for ball setting and sealing.

[0061] Below the step of the upper mandrel sealing section 1e1, there is a return spring 1h. The lower end of the return spring 1h is supported on the spring seat 1j, and the spring seat 1j is fixed on the cylinder body through the spring seat locking pin 1j1.

[0062] The lower end of the upper mandrel 1e is screwed with a lower mandrel 1k. The upper end of the lower mandrel 1k is provided with a large end 1k1 of the lower mandrel, and the large end 1k1 of the lower mandrel abuts against the bottom of the lowermost cone sleeve 1f to provide positioning for the lower part of the cone sleeve 1f. The lower end of the lower mandrel 1k is inserted into the guide sleeve 1m to control the translation of the upper mandrel 1e and the lower mandrel 1k along the axis of the cylinder body, avoiding inclination and ensuring good cooperation between the piston 1g and the cone sleeve 1f. The outer periphery of the guide sleeve 1m is fixed in the inner cavity of the cylinder body through the guide sleeve locking pin 1m1.

[0063] Above the printing section, there is a cylinder upper step 1b, and below the printing section, there is a cylinder lower step 1c. The tops of the lead molds 1p are located below the cylinder upper step 1b, and the bottoms of the lead molds 1p are located above the cylinder lower step 1c. Before the lead molds 1p are ejected, they are retracted inside the circumference formed by the cylinder upper step 1b and the cylinder lower step 1c, that is, the diameter of the circumference where the outer wall of the lead mold 1p is located is smaller than the diameter of the outer wall circumferences of the cylinder upper step 1b and the cylinder lower step 1c, so that the lead molds 1p are retracted inside the outer periphery of the tool or at most flush with the outer periphery of the tool, avoiding scraping against the wellbore wall.

[0064] When this tool reaches the well section where printing is required, a steel ball is dropped into the well. The steel ball falls until it seats on the ball seat 1e2 at the upper end of the upper mandrel 1e, closing the central hole of the upper mandrel 1e and generating pressure buildup. Then, the mud pump increases the pressure. Due to the setting of the steel ball, the pressure of the drilling fluid pushes the upper mandrel 1e downward, and the step of the upper mandrel sealing section 1e1 compresses the return spring 1h downward to store energy; at the same time, the cone sleeves 1f sleeved on the upper mandrel 1e move downward synchronously, and the wedge-shaped inclined surfaces 1f1 of the cone sleeves 1f squeeze the piston inclined surfaces 1g1 downward, forcing each piston 1g to slide outward along its respective radial hole, pushing the lead mold support 1n and the lead molds 1p outward. The lead molds 1p are attached to the inner wall of the wellbore, and under pressure, the cracks in the wellbore wall are printed on the outer surface of the lead molds 1p.

[0065] Then the mud pump reduces pressure. Under the tension of the return spring 1h, the upper mandrel 1e is pushed upward. The upper mandrel 1e drives each cone sleeve 1f to move upward. The wedge-shaped inclined surface 1f1 of the cone sleeve 1f and the piston inclined surface 1g1 slide relative to each other. The dovetail tenon 1g2 on the piston inclined surface 1g1 slides relative to the small end, i.e., the lower end, of the wedge-shaped inclined surface 1f1 along the dovetail groove 1f2 on the cone sleeve 1f. Since the piston 1g is restricted in the radial hole of the cylinder body, the piston 1g can only slide inward along the radial hole. The distance between the piston 1g and the axis of the cylinder body is reduced. The lead mold 1p and the lead mold support 1n retract to the outer periphery of the printing section of the cylinder body, located within the circumference formed by the upper step 1b and the lower step 1c of the cylinder body. In this way, during the process of lifting the tool to the wellhead, the lead mold 1p will not scrape against the well wall, and will not be stuck at the well wall step. The printed crack pattern can reach the ground intact for technicians to analyze.

[0066] A ground simulation test method for printing wellbore cracks of the present invention successively includes the following steps:

[0067] S1. Fabricate multiple sections of granite cylinder rings for simulating the wellbore.

[0068] Example 1 of the bamboo joint wellbore: The upper port of the lower granite cylinder ring is provided with an arc-shaped groove, and the lower port of the upper granite cylinder ring is provided with an arc-shaped tenon. The arc-shaped tenon is correspondingly inserted into the corresponding arc-shaped groove, and multiple sections of granite cylinder rings are stacked in sequence along the axial direction.

[0069] Example 2 of the bamboo joint wellbore: As Figure 4 shown, the butt joints of adjacent granite cylinder rings are respectively provided with cylinder ring positioning holes, and cylinder ring positioning pins 2a are respectively inserted into the cylinder ring positioning holes to achieve accurate positioning between the upper and lower granite cylinder rings. Multiple sections of granite cylinder rings are stacked in sequence along the axial direction.

[0070] For example, to simulate a wellbore with a diameter of Φ311mm and a wellbore enlargement rate designed at 2.9%, fabricate several sections of granite cylinder rings with a length of 0.5m, an inner diameter of Φ320mm, and a relatively thick wall thickness. In both embodiments, simulated cracks 2b are cut on the inner walls of the granite cylinder rings. Different-width simulated cracks 2b can be directly cut on the inner wall of the wellbore with cutters of different specifications. Also, a cutter of the same specification can be used to first cut a wider notch on the inner wall of the wellbore, then fill the notch with glue, add a metal sheet in the center of the glue, and draw out the metal sheet before the glue solidifies. After the glue solidifies, simulated cracks 2b with different shapes, numbers, and orientations are formed.

[0071] The widths of the simulated cracks on the inner wall of the wellbore faced by each lead mold are different. Taking four lead molds as an example, the crack widths corresponding to each lead mold are 1mm, 2mm, 4mm, and 6mm respectively.

[0072] S2. Make the wellhead cover plate 4 and the upper cover plate 5 for closing the wellhead. Both the wellhead cover plate 4 and the upper cover plate 5 are circular, and the outer periphery is provided with a flange larger than the outer diameter of the bamboo shaft. The flanges of the wellhead cover plate 4 and the upper cover plate 5 match each other, and the threaded holes correspond. Weld the temperature measuring sleeve 4b and the eccentric vertical pipe 8c on the wellhead cover plate 4, and process the center hole of the wellhead cover plate.

[0073] Then, the embedded bolts 4a for fixing the wellhead cover plate 4 and the upper cover plate 5 are made, a thread is hinged on the upper end of each embedded bolt 4a, and multiple transverse rods are welded to the bare rod section of the embedded bolt 4a to ensure that the embedded bolt 4a is reliably anchored in the reinforced concrete 11.

[0074] like Figure 5 As shown, the well bottom plate 3 is welded and made. The well bottom plate 3 is circular. A plurality of bottom plate anchor claws 3a are welded on the lower end surface of the well bottom plate 3. A cylinder positioning ring 3b erected upward is welded on the outer edge of the upper end surface of the well bottom plate 3. The inner diameter of the cylinder positioning ring 3b is adapted to the outer diameter of the granite cylinder ring. A center positioning ring 3c is welded at the center of the upper end surface of the well bottom plate 3. The inner diameter of the center positioning ring 3c is larger than the lower end outer diameter of the cylinder male joint 1d. The center positioning ring 3c, the cylinder positioning ring 3b and the well bottom plate 3 are all coaxial. A rubber cone sleeve 3d is embedded in the inner cavity of the center positioning ring 3c. The rubber cone sleeve 3d is adapted to the cylinder male joint 1d at the lower end of the printing device 1, which can accurately position the printing device 1 and protect the thread of the cylinder male joint 1d from damage.

[0075] S3, such as Figure 6 As shown, a well pit is dug on the ground, a concrete base is first poured at the bottom of the pit, the well bottom plate 3 is horizontally placed at the bottom of the pit, the bottom plate anchor claws 3a are embedded in the concrete, and the bottom of the heating cable sleeve 10 is also pre-buried in the concrete base.

[0076] A heating device 9 is placed in the central positioning ring 3c. The central opening of the well bottom plate 3 is used for the power supply cable of the heating device 9 to pass through. The power supply cable is connected to the heating device 9. The power supply cable passes through the heating cable casing 10 and extends to the ground. After power is connected, the heating function is tested to be normal.

[0077] S4. After the concrete base solidifies, the bamboo wellbore 2 is stacked section by section on the well bottom plate 3. The lower end of the bottom granite cylinder ring is embedded in the cylinder positioning ring 3b, and the upper sections are nested in sequence, or positioned with each other through the cylinder ring positioning pins 2a. The stacked bamboo wellbore 2 is coaxial with the center positioning ring 3c on the well bottom plate 3.

[0078] S5. Cover the upper end of the bamboo shaft 2 with a wooden mold, on which are provided wooden mold holes corresponding to the bolt holes of the flange of the wellhead cover plate. Each embedded bolt 4a passes through from bottom to top and is fixed in the corresponding wooden mold hole, and each embedded bolt 4a is suspended on the outer periphery of the bamboo shaft 2.

[0079] S6. Reinforce the steel cage around the outer periphery of the bamboo joint wellbore 2. The crossbar of the embedded bolt 4a can be spot-welded to the steel cage. After the steel cage is fabricated, pour concrete to form a reinforced concrete layer around the outer periphery of the bamboo joint wellbore 2, simulating the rock environment around the wellbore, and wait for the concrete 11 to reach the required strength.

[0080] S7. After the reinforced concrete reaches the required strength, remove the wooden formwork. As Figure 7 . Figure 8 shown in the figure, screw the upper joint 6 of the cylinder into the tapered female thread 1a at the upper end of the printing device 1. The upper port of the central hole of the upper joint 6 of the cylinder is welded with a central vertical pipe 7c that extends upward out of the wellhead.

[0081] S8. Lift the printing device 1 and place it into the inner cavity of the bamboo joint wellbore 2. The male joint 1d at its lower end is inserted into the rubber cone sleeve 3d to ensure that the printing device 1 and the bamboo joint wellbore 2 are coaxial. Multiple cameras can be installed in the upper part of the inner cavity of the bamboo joint wellbore, and each camera monitors the movement of the corresponding lead mold respectively.

[0082] S9. Cover the wellhead cover 4 on the top of the bamboo joint wellbore 2. Pass the upper end of the embedded bolt 4a through the flange bolt hole of the wellhead cover 4, and the central vertical pipe 7c extends out of the central hole of the wellhead cover. The eccentric vertical pipe 8c deviates from the axis of the bamboo joint wellbore 2 and its lower end is inserted into the upper inner cavity of the bamboo joint wellbore 2. The upper end of the temperature measuring sleeve 4b is open, and the part located in the inner cavity of the bamboo joint wellbore 2 is closed. A thermal resistor can be inserted into the temperature measuring sleeve 4b to measure the temperature of the drilling fluid, or heat-conducting oil can be injected into the temperature measuring sleeve 4b and a thermometer can be inserted to directly observe the temperature reading.

[0083] Then cover the upper cover 5 above the wellhead cover 4. The upper end of the eccentric vertical pipe 8c extends out of the through hole of the upper cover 5. There is also a hole on the upper cover 5 corresponding to the upper port of the temperature measuring sleeve 4b. The center of the top surface of the wellhead cover 4 and the outer periphery of the central hole of the upper cover are sealed with each other through the wellhead cover sealing ring 4c. Then screw on the fastening nut and the locknut at the upper end of each embedded bolt 4a to fix the wellhead cover 4 and the upper cover 5 at the wellhead. Then weld the outer periphery of the central vertical pipe 7c to the upper port of the central hole of the upper cover.

[0084] S10. Install a central vertical pipe tee at the upper end of the central vertical pipe 7c. Install a pressure gauge 7b inside the cylinder at the upper port of the central vertical pipe tee. Install an injection valve 7a inside the cylinder at the middle inlet of the central vertical pipe tee, and connect an injection pipe 7 inside the cylinder to the outer port of the injection valve 7a inside the cylinder.

[0085] Install an eccentric vertical pipe tee at the upper end of the eccentric vertical pipe 8c. Install a pressure gauge 8b in the annulus at the upper port of the eccentric vertical pipe tee. Install an injection valve 8a in the annulus at the middle inlet of the eccentric vertical pipe tee, and connect an injection pipe 8 in the annulus to the outer port of the injection valve 8a in the annulus.

[0086] S11. Inject water into the wellbore through the in-cylinder water injection valve 7a and the annulus water injection valve to apply pressure to the wellbore, and print the wellbore fractures with the printing device.

[0087] Step S11 includes the following sub-steps:

[0088] Step S11.1. Set the simulated well depth, calculate the hydrostatic pressure P_hydro at the corresponding well depth according to the simulated well depth and the drilling fluid density, and determine the test pressure value P_test in the wellbore.

[0089] Step S11.2. Fill the bamboo joint wellbore with water through the annulus water injection valve 8a and the in-cylinder water injection valve 7a, and evacuate the gas at the top of the wellbore.

[0090] Step S11.3. Pressurize the pressure in the annulus of the printing device to be equal to P_hydro through the annulus water injection pipe 8, and raise the water temperature to be the same as that of the simulated well section.

[0091] Step S11.4. Pressurize the pressure in the inner cavity of the printing device 1 to the starting value of P_test through the in-cylinder water injection pipe 7. The upper mandrel 1e drives each cone sleeve 1f to move downward. The dovetail tenon 1g2 on the piston inclined surface 1g1 slides upward along the dovetail groove 1f2 on the cone sleeve 1f. The wedge-shaped inclined surface 1f1 of the cone sleeve 1f and the piston inclined surface 1g1 slide relative to each other. The piston pushes the lead mold support outwards, and the lead mold presses on the inner wall of the wellbore for printing.

[0092] Step S11.5. Reduce the pressure in the inner cavity of the printing device 1 to be equal to P_hydro, so that the pressure inside and outside the tool is balanced. The return spring pushes the upper mandrel 1e upward. The upper mandrel 1e drives each cone sleeve 1f to move upward. The dovetail tenon 1g2 on the piston inclined surface 1g1 slides downward along the dovetail groove 1f2 on the cone sleeve 1f. The lead mold and the lead mold support retract to the outer periphery of the printing section of the cylinder.

[0093] Step S11.6. First, relieve the pressure of the in-cylinder water injection pipe 7, then relieve the pressure of the annulus water injection pipe 8. Dismantle the wellhead facilities, lift out the printing device 1, and observe the printing pattern of the lead mold 1p.

[0094] In step S11.6, because the wider the crack, the easier it is to print clearly. If only the printing pattern of the widest crack, such as 6 mm, is clear, then determine the printing pressure of the widest crack of 6 mm as P_test.

[0095] If the printing patterns of medium-width and above cracks are clear, then determine the printing pressure of the medium-width crack as P_test. For example, if the printing patterns of 4 mm and 6 mm cracks are clear, then determine the printing pressure of the 4 mm crack as P_test. For example, if the printing patterns of 2 mm, 4 mm, and 6 mm cracks are clear, then determine the printing pressure of the 2 mm crack as P_test.

[0096] If the printing pattern of the crack with the thinnest width of 1 mm is clear, and the printing patterns of the cracks with widths of 2 mm, 4 mm, and 6 mm are necessarily clearer, then determine the printing pressure of the crack with the thinnest width of 1 mm as P test.

[0097] If the printing patterns of all the lead molds are not clear, then after repairing the lead molds and reassembling the test device, increase the in-well test pressure value in step S11.1 by 5 MPa as the new P test, and continue the test.

[0098] If it is necessary to test the crack printing effect at other well depths, then start the test again from step S11.1.

[0099] The above is only the preferred and feasible embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention. It is not intended to limit the patent protection scope of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. Except for the above embodiments, without departing from the spirit and scope of the present invention, the present invention may have other implementation manners. The present invention will also have various changes and improvements. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention. The protection scope required by the present invention is defined by the appended claims and their equivalents. The technical features not described in the present invention can be realized by or adopted the existing technologies, which will not be elaborated here.

Claims

1. A ground simulation test method for printing wellbore fissures, characterized in that, The steps are as follows: S1. Making multiple granite cylinder rings for simulating a wellbore, wherein the inner wall of each granite cylinder ring is cut with simulated cracks; S2, making a wellhead cover plate and an upper cover plate for closing the wellhead, an eccentric vertical pipe and a temperature measuring sleeve are welded on the wellhead cover plate, and a well bottom plate is welded; S3, dig a well pit on the ground, pour a concrete base at the bottom of the pit, and embed the well bottom plate horizontally in the top center of the concrete base; S4. After the concrete base solidifies, granite cylinder rings are stacked section by section on the well bottom plate to form a bamboo well shaft; S5. Cover the upper end of the bamboo shaft with a wooden mold, which is provided with wooden mold reamed holes corresponding to the bolt holes of the flange of the wellhead cover plate, and each embedded bolt passes through from bottom to top and is fixed in the corresponding wooden mold reamed hole; S6. Tie a steel cage around the outer periphery of the bamboo shaft and then pour concrete; S7. After the reinforced concrete reaches the required strength, the wooden mold is removed, and the upper joint of the cylinder is screwed on the upper end of the printing device. A central vertical pipe extending upward is welded to the upper end of the central hole of the upper joint of the cylinder; S8, lifting the printing device, placing it into the inner cavity of the bamboo wellbore and placing it at the center of the well bottom plate; S9, installing the wellhead cover plate, and then covering the upper cover plate on the wellhead cover plate; S10, install an in-tube pressure gauge on the central vertical pipe and connect it to the in-tube water injection pipe through the in-tube water injection valve, install an annular pressure gauge on the eccentric vertical pipe and connect it to the annular water injection pipe through the annular water injection valve; S11, pressurizing the wellbore through the water injection valve in the barrel and the water injection valve in the annulus, and printing the cracks on the wellbore wall on the printing device; A printing section is provided in the middle of the cylinder of the printing device, and a plurality of lead mold supports are evenly provided on the outer periphery of the cylinder of the printing section, and the outer wall of each lead mold support is respectively fitted with a lead mold, and each lead mold support is respectively driven by a plurality of pistons, and each piston is respectively embedded in the radial hole of the cylinder, and an upper core shaft is provided in the central hole of the cylinder, and the inner end of each piston is respectively provided with a piston inclined surface, and the piston inclined surfaces of each piston located on the same circumference respectively abut against the wedge-shaped inclined surface of the outer periphery of the same cone sleeve, and each cone sleeve is sequentially mounted and fixed on the outer periphery of the upper core shaft, and each wedge-shaped inclined surface on each cone sleeve is centrally symmetrically arranged and the lower end is respectively inclined toward the axis direction of the cylinder; dovetail grooves are respectively provided on the wedge-shaped inclined surface of the cone sleeve, and dovetail tenons are respectively provided on the piston inclined surface of the piston, and the dovetail tenons are respectively embedded in the corresponding dovetail grooves; The upper end of the upper core shaft is provided with an enlarged upper core shaft sealing section and the upper end of the upper core shaft center hole is provided with a ball seat, a steel ball is seated on the ball seat, a return spring is provided under the step of the upper core shaft sealing section, the lower end of the return spring is supported on a spring seat, and the spring seat is fixed on the cylinder.

2. The ground simulation test method for printing wellbore fractures according to claim 1, characterized in that: In step S2, a bottom plate anchor claw embedded in reinforced concrete is welded to the lower end surface of the well bottom plate, and an upwardly erected cylinder positioning ring is welded to the outer periphery of the well bottom plate; in step S4, the lower end of the bottom granite cylinder ring is embedded in the cylinder positioning ring.

3. The ground simulation test method for printing wellbore fissures according to claim 2, wherein: A center positioning ring is welded at the center of the upper end surface of the well bottom plate, and a rubber cone sleeve is embedded in the inner cavity of the center positioning ring. In step S8, the male joint of the barrel at the lower end of the printing device is inserted into the rubber cone sleeve and adapted to each other.

4. The ground simulation test method for printing wellbore fissures according to claim 1, characterized in that: In step S4, the ports where adjacent granite tube rings are connected are respectively provided with tube ring positioning holes, and each tube ring positioning hole is respectively inserted with a tube ring positioning pin to achieve accurate positioning between the upper and lower granite tube rings.

5. The ground simulation test method for printing wellbore fissures according to claim 1, characterized in that: In step S3, a heating device is installed at the center of the upper end surface of the well bottom plate, and the power supply cable of the heating device is located in the heating cable sheath; the lower end of the temperature measuring sheath is closed and the upper end is open, and a thermal resistance probe is installed in the inner cavity of the temperature measuring sheath.

6. The ground simulation test method for printing wellbore fissures according to claim 1, wherein: In step S9, the center of the top surface of the wellhead cover plate and the outer periphery of the center hole of the upper cover plate are sealed with each other through a wellhead sealing ring, and then the fastening nuts and cap nuts are screwed on the upper ends of the embedded bolts to fix the wellhead cover plate and the upper cover plate to the wellhead, and then the outer periphery of the central vertical pipe is welded to the upper end of the center hole of the upper cover plate.

7. The ground simulation test method for printing wellbore fissures according to claim 1, characterized in that: The lower end of the upper core shaft is screwed with the lower core shaft, the upper end of the lower core shaft is provided with a lower core shaft large end, the lower core shaft large end abuts against the bottom of the lowest cone sleeve, the lower end of the lower core shaft is inserted in the guide sleeve, and the guide sleeve is fixed in the inner cavity of the cylinder.

8. The ground simulation test method for printing wellbore fissures according to claim 1, characterized in that: An upper cylinder step is provided above the printing section, and a lower cylinder step is provided below the printing section. The outer wall of each lead mold is located within the axial projection range of the upper cylinder step and the lower cylinder step.

9. The ground simulation test method for printing wellbore fractures according to claim 1, characterized in that: A plurality of cameras are arranged on the upper part of the inner cavity of the bamboo shaft, and each camera monitors the movement of a corresponding lead mold respectively.

10. The ground simulation test method for printing wellbore fissures according to claim 1, characterized in that The lead molds are symmetrically arranged in three or four pieces in the circumferential direction, and the simulated crack widths of the inner wall of the wellbore faced by each lead mold are different; the simulated cracks are formed by cutters of different specifications; or a wider groove is first cut on the inner wall of the wellbore with a cutter, and then glue is filled in the groove, a metal sheet is added to the center of the glue, and the metal sheet is pulled out before the glue solidifies, and simulated cracks of different widths are formed after the glue solidifies.

11. The method for ground simulation test of wellbore fracture printing according to claim 10, characterized in that, Step S11 includes the following sub-steps: Step S11.1, set the simulated well depth, and calculate the liquid column pressure P at the corresponding well depth according to the simulated well depth and drilling fluid density. 液柱 , and determine the test pressure value P in the wellbore 试验 ; Step S11.2, fill the bamboo wellbore with water through the annular water injection valve and the inner wellbore water injection valve to exhaust the gas at the top of the wellbore; Step S11.3: Pressurize the pressure in the annulus of the printing device to be equal to P through the annulus water injection pipe 液柱 , and raise the water temperature to be the same as that of the simulated well section; Step S11.4: Pressurize the pressure inside the cavity of the printing device to the starting value of P through the water injection pipe inside the cylinder. The upper mandrel drives each cone sleeve to move downward, and the dovetail on the piston slope slides upward along the dovetail groove on the cone sleeve. The wedge slope of the cone sleeve and the piston slope slide relative to each other, and the piston pushes the lead mold support outwards. The lead mold presses against the inner wall of the wellbore for printing. 试验 The starting value is such that the upper mandrel drives each cone sleeve to move downward. The dovetail on the piston slope slides upward along the dovetail groove on the cone sleeve. The wedge slope of the cone sleeve and the piston slope slide relative to each other, and the piston pushes the lead mold support outwards. The lead mold presses against the inner wall of the wellbore for printing. Step S11.5, reduce the internal cavity pressure of the printing device to be equal to P 液柱 , pressure balance is achieved inside and outside the tool, the return spring pushes the upper mandrel upward, the upper mandrel drives each tapered sleeve to move upward, the dovetail on the piston slope slides downward along the dovetail groove on the tapered sleeve, and the lead mold and the lead mold support retract to the outer periphery of the printing section of the cylinder body; Step S11.6, first depressurize the water injection pipe in the barrel, then depressurize the water injection pipe in the annulus, dismantle the wellhead facilities, remove the printing device, and observe the printing pattern of the lead mold.

12. The ground simulation test method for printing wellbore fissures according to claim 11, wherein, In step S11.6, if only the printing pattern of the widest crack is clear, determine that the printing pressure of the widest crack is P 试验 ; if the printing patterns of cracks with medium width or above are clear, determine that the printing pressure of the medium-width crack is P 试验 ; if the printing pattern of the narrowest crack is clear, determine that the printing pressure of the narrowest crack is P 试验 .

13. The ground simulation test method for printing wellbore fissures according to claim 11, characterized in that, In step S11.6, if the printed patterns of all the lead molds are not clear, after repairing the lead molds and reassembling the test device, increase the test pressure value in the wellbore in step S11.1 by 5 MPa as the new P 试验 , and continue the test.

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