A simulation wellbore for evaluating flushing efficiency of a cementing prepad fluid

Abstract

The utility model relates to oil and gas well cementing technical field especially relates to simulation well bore for cementing preflushing efficiency evaluation. Simulation well bore includes the outer tube of both ends sealing, and the simulation core is fixedly sleeved in the outer tube, and the simulation casing is fixedly sleeved in the simulation core and has the annular cavity between both, and the annular cavity bottom communicates with the simulation casing inner chamber bottom to make the liquid that pumps into the simulation casing inner chamber can flow back into the annular cavity to carry out the flushing to the casing wall and the core wall, and the outer tube top is equipped with the pump inlet that communicates the simulation casing inner chamber and the discharge port that communicates the annular cavity to discharge the liquid in the annular cavity. Simulation formation by simulation core, simulation cementing casing by simulation casing, cementing casing is in the core inside, and the flushing fluid first enters the simulation casing inner chamber, then flows back into the annular cavity to carry out the flushing to the casing wall and the core wall, and continues to discharge from the outer tube top, forms the dynamic circulation of flushing fluid, can more real simulation actual well bore flushing situation.

Description

Technical Field

[0001] This utility model relates to the field of oil and gas well cementing technology, and in particular to a simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing. Background Technology

[0002] Before cementing oil and gas wells, drilling fluid forms mud cakes on the wellbore and casing surfaces. If these mud cakes are not effectively removed during cementing, the annular cement slurry will not bond effectively with the wellbore rock and casing after cementing, affecting cementing quality. In severe cases, this can create flow channels, preventing effective isolation of formation fluids and even causing annular pressure. Therefore, a pre-flush fluid is typically injected before cementing to separate the drilling fluid from the cement slurry. The pre-flush fluid plays a crucial role in isolating the drilling fluid and cement slurry, flushing mud cakes from the wellbore, and improving interfacial bonding quality, making it a key technical measure to ensure cementing quality. With increasing drilling depth and geological complexity in oil and gas wells, the role of the pre-flush fluid in cementing engineering is becoming increasingly important, and the performance requirements for the pre-flush fluid are also becoming more stringent. Effectively evaluating the flushing efficiency of the pre-flush fluid is crucial for selecting the best pre-flush materials, reducing the cost of the pre-flush system, and improving cementing quality.

[0003] Wellbore simulation is a commonly used method for evaluating the efficiency of pre-cementing fluid flushing. This method requires simulating formation conditions using a simulated wellbore and employing dynamic circulation to simulate the flushing of the wellbore and casing walls by the pre-flush fluid. Existing simulated wellbores typically consist of an inner cylinder or core inside an outer cylinder. For example, the simulated wellbore of the cementing flushing fluid cleaning efficiency evaluation device disclosed in Chinese invention patent application CN115059454A includes an outer cylinder and a core placed inside the outer cylinder. The outer cylinder has wellbore covers at both ends, and there is an annulus between the outer cylinder and the core. The outer cylinder simulates the cementing casing, and the core simulates the formation. First, drilling fluid circulation is started to form a mud cake on the outer wall of the core. Then, pre-flush fluid circulation is started to flush the outer wall of the core. The pre-flush fluid flushing efficiency is calculated based on the change in core weight. Existing simulated wellbore systems use an outer cylinder to simulate cementing casing, with a core sample placed inside the outer cylinder to simulate the formation. The cementing casing is located outside the simulated core sample. However, in reality, the cementing casing is run into the wellbore and is located inside the core sample. Therefore, existing simulated wellbore systems cannot accurately simulate the actual wellbore conditions, thus affecting the accuracy of the pre-flush efficiency evaluation results. Utility Model Content

[0004] The purpose of this invention is to provide a simulated wellbore for evaluating the efficiency of cementing pre-flush fluid, in order to solve the problem that existing simulated wellbore cannot truly simulate the actual wellbore conditions, thus affecting the accuracy of the evaluation results of pre-flush fluid efficiency.

[0005] The present invention adopts the following technical solution:

[0006] A simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing includes an outer cylinder sealed at both ends, a simulated core fixedly installed inside the outer cylinder, a simulated casing fixedly installed inside the simulated core, and an annular cavity between the two. The bottom of the annular cavity is connected to the bottom of the inner cavity of the simulated casing so that the liquid pumped into the inner cavity of the simulated casing can flow upward back into the annular cavity to flush the casing wall and the core wall. The top of the outer cylinder is provided with a pump inlet connected to the inner cavity of the simulated casing and an outlet connected to the annular cavity to discharge the liquid in the annular cavity.

[0007] Furthermore, a simulated core fixing structure is provided on the inner wall surface of the outer cylinder, and the simulated core is fixedly supported on the simulated core fixing structure.

[0008] Furthermore, the simulated core fixing structure is a simulated core fixing block fixedly connected to the inner wall of the outer cylinder. The simulated core fixing block is an annular block, and the simulated core is fixedly supported on the annular block.

[0009] Furthermore, the outer cylinder is equipped with an eccentric control device for controlling the eccentricity of the simulated casing. There are two eccentric control devices, which are arranged at intervals along the axial direction of the simulated casing. The simulated casing is fixed and held inside the simulated core by the two eccentric control devices.

[0010] Furthermore, the eccentric control device includes a collar for fitting onto the simulated sleeve and two or more sets of eccentric adjustment screws detachably connected to the collar. Each set of eccentric adjustment screws has a different length to adjust the eccentricity of the simulated sleeve when different sets of eccentric adjustment screws are replaced. The eccentric adjustment screws are fixedly connected to the outer cylinder, and the simulated sleeve is supported on the lower eccentric control device.

[0011] Furthermore, at least two outwardly protruding anti-slip blocks are provided on the simulated sleeve at intervals along its circumference, and the simulated sleeve is supported on the lower eccentric control device by the simulated sleeve anti-slip blocks.

[0012] Furthermore, the outer cylinder includes a cylinder body and upper and lower pressure caps that are sealed at both ends of the cylinder body. The pump inlet and outlet are both located on the upper pressure cap, and a sealing diaphragm is provided inside the upper pressure cap to achieve a sealing fit between the upper pressure cap and the upper end of the simulated sleeve.

[0013] Furthermore, the pump inlet is located at the center of the upper pressure cover, and the outlet is located to the side of the pump inlet.

[0014] Furthermore, the discharge outlet has two or more outlets that are evenly spaced on the same circumference.

[0015] Furthermore, the bottom of the outer cylinder is provided with an vent that connects the inner cavity of the outer cylinder with the outside.

[0016] Beneficial Effects: This invention, using a simulated wellbore for evaluating the efficiency of pre-cleaning fluid flushing, is a pioneering creation. A simulated core is fixedly installed inside the outer cylinder, and a simulated casing is installed inside the simulated core. An annular cavity exists between the simulated casing and the simulated core. The simulated core simulates the formation, and the simulated casing simulates the cementing casing. The cementing casing is located inside the core. Flushing fluid enters the simulated casing cavity from the pump inlet at the top of the outer cylinder, flows out from the bottom of the simulated casing cavity, and then flows upwards back into the annular cavity to flush the casing wall and core wall. It continues to exit from the outlet at the top of the outer cylinder, forming a dynamic circulation of flushing fluid. This simulates the flushing of the wellbore and casing walls by the pre-cleaning fluid, more realistically mimicking the actual wellbore flushing situation, thereby improving the accuracy of the pre-cleaning fluid flushing efficiency evaluation results. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to this utility model;

[0018] Figure 2 This is a top view of the upper pressure cap;

[0019] Figure 3 This is a cross-sectional view of the upper pressure cap;

[0020] Figure 4 This is a schematic diagram of the eccentric control device.

[0021] In the diagram: 3061, upper pressure cap fastening screw; 3062, upper pressure cap; 3063, upper eccentric control device; 3064, simulated casing; 3065, upper pressure cap fixing nut; 3066, eccentric control device fixing nut; 3067, outer cylinder; 3068, simulated core; 3069, annular cavity; 30610, upper eccentric control device fixing block; 30611, simulated core fixing block; 30612, lower eccentric control device; 30613, lower pressure cap; 30614, vent; 30615, simulated casing anti-slip block; 30616, lower pressure cap fastening screw; 30617, lower pressure cap fixing nut;

[0022] 30621, Discharge port; 30622, Upper gland fastening screw hole; 30623, Pump inlet; 30624, Sealing diaphragm;

[0023] 30631, Eccentric control device fixing screw; 30632, Eccentric adjustment screw; 30633, Collar. Detailed Implementation

[0024] Existing simulated wellbore systems cannot realistically simulate actual wellbore conditions, thus affecting the accuracy of pre-flush efficiency evaluation results. Therefore, this invention provides a simulated wellbore system for evaluating pre-flush efficiency, which can more realistically simulate actual wellbore flushing conditions.

[0025] The basic inventive concept of this utility model is as follows: a simulated core is fixedly installed inside the outer cylinder, and a simulated casing is installed inside the simulated core, with an annular cavity between the simulated casing and the simulated core. The simulated core simulates the formation, and the simulated casing simulates the cementing casing. The cementing casing is located inside the core. The flushing fluid first enters the inner cavity of the simulated casing, flows out from the bottom of the inner cavity, and then flows back upward into the annular cavity to flush the casing wall and the core wall. It continues to be discharged from the outlet at the top of the outer cylinder, thus forming a dynamic circulation of flushing fluid to simulate the flushing of the well wall and casing wall by the pre-flush fluid. This can more realistically simulate the actual wellbore flushing situation, thereby improving the accuracy of the evaluation results of the pre-flush fluid flushing efficiency.

[0026] Based on the above inventive concept, the following is a detailed description of the embodiments of the simulated wellbore for evaluating the efficiency of cementing pre-flush fluid.

[0027] like Figure 1 As shown, the simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing in this invention includes components such as an outer cylinder 3067, a simulated core 3068, a simulated casing 3064, and an eccentric control device. The outer cylinder 3067 includes a body, with an upper pressure cap 3062 and a lower pressure cap 30613 fixedly connected to its two ends to seal both ends and achieve a sealing and pressure-maintaining effect. The simulated core 3068 is housed inside the outer cylinder 3067. The simulated core 3068 is used to simulate the wellbore. The simulated core 3068 and the outer cylinder 3067 are in a clearance fit. A simulated core fixing structure, specifically a simulated core fixing block 30611, is provided on the inner wall of the outer cylinder 3067 at a distance from the lower end of the cylinder. The simulated core 3068 is annular, and after being inserted, it is supported on the annular block, thus fixing the simulated core 3068 within the outer cylinder 3067. Since the simulated core 3068 is relatively heavy, an annular stop is installed around its circumference to support it, which helps ensure the reliability of its fixed support inside the outer cylinder. The simulated core 3068 can be obtained through drilling or manufactured artificially.

[0028] The simulated core 3068 is fitted with a simulated sleeve 3064. The simulated sleeve 3064 is fixed inside the simulated core 3068 by two eccentric control devices. There is an annular cavity 3069 between the simulated sleeve 3064 and the simulated core 3068. There is a distance between the bottom end of the simulated sleeve 3064 and the lower pressure cap 30613, forming a bottom connecting cavity below the simulated sleeve 3064. The bottom of the annular cavity 3069 is connected to the bottom of the inner cavity of the simulated sleeve 3064 through the bottom connecting cavity, so that the liquid pumped into the inner cavity of the simulated sleeve 3064 can return to the annular cavity 3069 through the bottom connecting cavity to flush the sleeve wall and the core wall.

[0029] The upper pressure cap 3062 is fixedly connected to the upper end of the outer cylinder 3067 by upper pressure cap fastening screws 3061. The upper end of the outer cylinder 3067 is provided with an upper pressure cap fixing nut 3065, and the upper pressure cap fastening screws 3061 are threaded into the upper pressure cap fixing nut 3065. The upper end of the simulated casing 3064 rests on the upper pressure cap 3062. The upper pressure cap 3062 has a sealing diaphragm 30624 inside to achieve a sealed fit between the upper pressure cap 3062 and the upper end of the simulated casing 3064. The upper pressure cap 3062 has a pump inlet 30623 communicating with the inner cavity of the simulated casing 3064 and an outlet 30621 communicating with the annular cavity 3069. Flushing fluid is pumped into the inner cavity of the simulated casing 3064 through the pump inlet 30623. The flushing fluid entering the annular cavity 3069 can be discharged from the simulated wellbore through the outlet 30621 and continue to enter the circulation pipeline, achieving dynamic circulation flushing of the flushing fluid.

[0030] The lower pressure cap 30613 is fixedly connected to the lower end of the outer cylinder 3067 by lower pressure cap fastening screws 30616. A lower pressure cap fixing nut 30617 is provided at the lower end of the outer cylinder 3067, and the lower pressure cap fastening screws 30616 are threaded into the lower pressure cap fixing nut 30617. The lower pressure cap 30613 is a circular cap with four lower pressure cap fastening screw holes evenly distributed circumferentially along its edge. The lower pressure cap 30613 is fixedly connected to the lower end of the outer cylinder 3067 by the four lower pressure cap fastening screws 30616, ensuring reliable connection. The lower pressure cap 30613 is provided with a drain port 30614 connecting the inner cavity of the outer cylinder 3067 to the outside, allowing the liquid inside the simulated well to be drained.

[0031] The structure of the upper pressure cap 3062 is as follows Figure 2-3 As shown, the upper pressure cover 3062 is a circular cover. A pump inlet 30623 is located at the center of the upper pressure cover 3062. Two outlets 30621 are located beside the pump inlet 30623 on the upper pressure cover 3062, and the two outlets 30621 are arranged at a 180° interval on the same circumference. Providing two outlets 30621 serves two purposes: firstly, it accelerates the outflow rate of the fluid in the annular cavity 3069, shortening the flushing cycle time; secondly, it helps prevent blockage at a single outlet 30621, which could prevent the fluid in the annular cavity 3069 from flowing out, rendering the device unusable. Of course, in other embodiments, the upper pressure cover 3062 can also have more outlets 30621, so that the outlets 30621 are evenly distributed on the same circumference. Alternatively, only one outlet 30621 may be provided.

[0032] The upper cover 3062 has four upper cover fastening screw holes 30622 at its edge. The four upper cover fastening screw holes 30622 are evenly distributed around the circumference of the upper cover 3062. The upper cover 3062 is fixedly connected to the upper end of the outer cylinder 3067 by the four upper cover fastening screws 3061 to ensure the reliability of the connection.

[0033] The simulated casing 3064 is fixedly held inside the simulated core 3068 by two eccentric control devices, which are fitted onto the simulated casing 3064 at intervals. Two outwardly protruding anti-slip blocks 30615 are provided at the lower part of the simulated casing 3064, threadedly connected to it. These blocks are supported on a lower eccentric control device 30612, which is fixedly connected to an outer cylinder 3067. This arrangement supports the simulated casing 3064 inside the simulated core 3068 and creates a gap between the bottom of the simulated casing 3064 and the bottom of the outer cylinder 3067, forming a channel for fluid to return to the annular cavity 3069. The simulated sleeve 3064 is supported on the lower eccentric control device by two spaced-apart simulated sleeve anti-slip blocks 30615. This design is simple and easy to assemble. Furthermore, the anti-slip blocks 30615 have a small obstruction area on the annular cavity 3069, minimizing resistance to fluid flow within the cavity and ensuring rapid upward flow of the liquid. An upper eccentric control device fixing block 30610 is threadedly connected to the upper part of the simulated sleeve 3064. The upper eccentric control device 3063 is supported on the upper eccentric control device fixing block 30610 to prevent it from slipping.

[0034] The eccentricity of the simulated casing 3064 is adjusted using two eccentric control devices to more realistically simulate wellbore conditions. The structure of the eccentric control device is as follows: Figure 4 As shown, it includes a collar 30633 for fitting onto the simulated sleeve 3064 and multiple sets of eccentric adjustment screws 30632 for threaded connection with the collar 30633 (only one set is shown in the figure). One end of the eccentric adjustment screw 30632 is fixedly connected to an eccentric control device fixing screw 30631. An eccentric control device fixing nut 3066 is provided on the outer cylinder 3067 (see...). Figure 2The eccentric control device can also be fixed to the outer cylinder 3067 by threading the eccentric control device fixing screw 30631 into the eccentric control device fixing nut 3066. Each set of eccentric adjustment screws 30632 has a different length. The eccentricity of the simulated casing 3064 is adjusted by changing different sets of eccentric adjustment screws 30632. The length of the eccentric adjustment screws 30632 can be calculated according to the simulated wellbore size and the outer diameter of the simulated casing 3064, with different eccentricity values ​​of 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9. Ten sets of eccentric adjustment screws 30632 with different eccentricities are provided. Appropriate eccentric adjustment screws 30632 are selected according to different test requirements and installed onto the collar 30633 for testing.

[0035] The eccentricity control device used in this embodiment has a simple structure and is easy to assemble. Of course, in other embodiments, existing eccentricity adjustment control devices can also be used, which will not be described in detail here.

[0036] The assembly process for the simulated wellbore can be referenced as follows:

[0037] (1) Determine the casing eccentricity for the test and select the corresponding length eccentricity adjusting screw 30632 of the two eccentricity control devices; (2) Install the simulated core 3068 into the outer cylinder 3067; (3) Place the simulated casing 3064 horizontally and put the collar 30633 of the lower eccentricity control device 30612 onto the simulated casing 3064; (4) Fix the anti-slip block 30615 of the simulated casing onto the simulated casing 3064; (5) Place the outer cylinder 3067 and the simulated core 3068 horizontally and place the simulated casing 3064 together with the lower eccentricity control device 30612 onto the simulated casing 3064. (6) Insert the collar 30633 of the control device 30612 into the simulated core 3068, and then use the eccentric adjustment screw 30632 of the corresponding length to fix the lower eccentric control device 30612 and adjust the eccentricity of the casing; (7) Put the collar 30633 of the upper eccentric control device 3063 on the upper part of the simulated casing 3064, and use the eccentric adjustment screw 30632 of the corresponding length to fix the upper eccentric control device 3063 and adjust the eccentricity of the casing; (8) Install the lower pressure cap 30613; (9) Install the upper pressure cap 3062.

[0038] Of course, this utility model is not limited to the embodiments described above.

[0039] For example, in the above embodiment, a simulated core fixing block is fixedly connected to the inner wall of the outer cylinder. The simulated core fixing block is an annular block, and the simulated core is supported on the annular block to achieve its fixation inside the outer cylinder. In other embodiments, multiple small blocks can be fixed at circumferential intervals on the inner wall of the outer cylinder to support the simulated core. Alternatively, in another embodiment, a simulated core fixing structure, such as a fixing bracket, is provided at the bottom of the outer cylinder to fix the simulated core.

[0040] For example, in the above embodiment, an eccentricity control device is provided inside the outer cylinder to control the eccentricity of the simulated casing. The simulated casing is fixedly held inside the simulated core by two eccentricity control devices. In other embodiments, the eccentricity control device may not be provided. The simulated casing can be fixedly held inside the simulated core by other structures. For example, multiple inwardly extending support rods can be fixedly connected circumferentially to the inner wall of the simulated core or the inner wall of the outer cylinder. A limiting step surface is machined on the outer wall of the simulated casing. The limiting step surface supports downward on each support rod, thereby fixing the simulated casing inside the simulated core.

[0041] For example, in the above embodiment, two outwardly protruding anti-slip blocks are provided at intervals along the circumference of the simulated sleeve, and the simulated sleeve is supported on the lower eccentric control device by the anti-slip blocks. In another embodiment, an anti-slip ring can also be fixedly connected to the outer wall of the simulated sleeve, so that the simulated sleeve is supported on the lower eccentric control device by the anti-slip ring.

[0042] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. The patent protection scope of the present utility model shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present utility model shall also be included within the protection scope of the present utility model.

Claims

1. A simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing, characterized in that: It includes an outer cylinder sealed at both ends, a simulated rock core fixedly installed inside the outer cylinder, a simulated casing fixedly installed inside the simulated rock core, and an annular cavity between the two. The bottom of the annular cavity is connected to the bottom of the inner cavity of the simulated casing so that the liquid pumped into the inner cavity of the simulated casing can flow upward back into the annular cavity to flush the casing wall and the rock core wall. The top of the outer cylinder is provided with a pump inlet connected to the inner cavity of the simulated casing and an outlet connected to the annular cavity to discharge the liquid in the annular cavity.

2. The simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to claim 1, characterized in that: The inner wall of the outer cylinder is provided with a simulated core fixing structure, and the simulated core is fixedly supported on the simulated core fixing structure.

3. The simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to claim 2, characterized in that: The simulated core fixing structure is a simulated core fixing block that is fixedly connected to the inner wall of the outer cylinder. The simulated core fixing block is an annular block, and the simulated core is fixedly supported on the annular block.

4. The simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to any one of claims 1-3, characterized in that: The outer cylinder is equipped with an eccentric control device for controlling the eccentricity of the simulated casing. There are two eccentric control devices, which are arranged at intervals along the axial direction of the simulated casing. The simulated casing is fixed and held inside the simulated core by the two eccentric control devices.

5. The simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to claim 4, characterized in that: The eccentricity control device includes a collar for fitting onto the simulated sleeve and two or more sets of eccentricity adjusting screws detachably connected to the collar. Each set of eccentricity adjusting screws has a different length to adjust the eccentricity of the simulated sleeve when different sets of eccentricity adjusting screws are replaced. The eccentricity adjusting screws are fixedly connected to the outer cylinder, and the simulated sleeve is supported on the lower eccentricity control device.

6. The simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to claim 5, characterized in that: The simulated sleeve is provided with at least two outwardly protruding anti-slip blocks along its circumference, and the simulated sleeve is supported on the lower eccentric control device by the simulated sleeve anti-slip blocks.

7. The simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to any one of claims 1-3, characterized in that: The outer cylinder includes a cylinder body and upper and lower pressure caps that are sealed at both ends of the cylinder body. The pump inlet and outlet are both located on the upper pressure cap. The upper pressure cap is provided with a sealing diaphragm to achieve a sealing fit between the upper pressure cap and the upper end of the simulated sleeve.

8. The simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to claim 7, characterized in that: The pump inlet is located at the center of the upper pressure cover, and the outlet is located to the side of the pump inlet.

9. The simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to claim 8, characterized in that: The discharge outlet has two or more outlets that are evenly spaced on the same circumference.

10. The simulated wellbore for evaluating the efficiency of pre-cementing fluid flushing according to any one of claims 1-3, characterized in that: The bottom of the outer cylinder is provided with an vent that connects the inner cavity of the outer cylinder to the outside.

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