An apparatus for simulating wellbore fluid loss measurement and filter cake evaluation and a test method thereof

Abstract

The present application belongs to the field of drilling fluid performance testing technology in the oil and gas industry, and relates to a simulation wellbore filtration loss measuring and filter cake evaluating device and a test method thereof. The simulation wellbore filtration loss measuring and filter cake evaluating device is composed of a base, a simulation wellbore outer tube, a supporting mechanism, a laser sensor, a laser sensor controller, a simulation wellbore inner tube, a driving mechanism, a liquid storage mechanism, a pressurizing mechanism and a heating mechanism. The use of the present application can reflect the dynamic filtration loss of the drilling fluid and test the filter cake erosion resistance for evaluating the filter cake quality. The simulation wellbore outer tube of the present application is made of transparent material resistant to high temperature and high pressure, and the filtration loss of the drilling fluid, the formation and destruction process and morphology of the filter cake under the conditions of fluid flow, nozzle injection, simulation wellbore inner tube and inner tube coupling agitation can be observed by visual observation. The present application has high simulation degree, simple operation, stable performance and strong reliability.

Description

Technical Field

[0001] This invention belongs to the field of drilling fluid performance testing technology in the oil and gas industry, specifically relating to a device and test method for simulating wellbore filtration loss measurement and filter cake evaluation. Background Technology

[0002] Drilling fluid filtration loss and filter cake quality are important indicators for judging the performance of drilling fluid. Drilling fluid with low filtration loss has only a small amount of filtrate entering the formation pores and fractures, which can reduce the degree of clay hydration dispersion, decrease hydraulic wedge effect, and enhance wellbore stability. To reduce drilling fluid filtration loss, the drilling fluid needs to form a thin and dense filter cake under pressure differential. Furthermore, the filter cake must have good toughness, adhere tightly to the wellbore, and not be easily broken by drilling fluid erosion. This is an important standard for measuring filter cake quality.

[0003] Existing API drilling fluid loss meters test filtration loss under static conditions, and the data obtained only reflects the static filtration properties of the drilling fluid. API stands for American Petroleum Institute, and an API drilling fluid loss meter is one that uses the standards of the American Petroleum Institute as its benchmark. However, in actual drilling operations, the drilling fluid flows within the wellbore. The flow and agitation of the fluid significantly affect the quality of the filter cake formed, thus influencing the filtration loss. Therefore, the drilling fluid filtration loss measured by conventional API drilling fluid loss meters differs significantly from the actual downhole conditions, and laboratory experimental data cannot effectively guide field operations. Furthermore, previously, the quality of the filter cake could only be evaluated based on the magnitude of the drilling fluid filtration loss, but the magnitude of filtration loss is not directly related to the quality of the filter cake, and when the filtration loss differences between different drilling fluids are small, it is impossible to determine the quality of the formed filter cake. Currently, there is a lack of effective methods for evaluating the quality of the filter cake formed by drilling fluid. Summary of the Invention

[0004] This invention provides a device and test method for simulating wellbore filtration loss measurement and filter cake evaluation. The purpose is to provide a device and method that can reflect the dynamic filtration loss of drilling fluid and test the erosion resistance of filter cake to evaluate the quality of filter cake.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A simulated wellbore filtration loss measurement and filter cake evaluation device, including

[0007] Base

[0008] The simulated well outer cylinder has a measuring platform connected to its bottom inner wall, and multiple filtrate collection mechanisms are connected at intervals on the measuring platform. An inner cylinder connecting mechanism is fixedly connected to the top side wall of the simulated well outer cylinder. The front end of the simulated well outer cylinder is sealed with an outer cylinder top cover plate, and a power transmission mechanism is connected to the outer cylinder top cover plate. The rear end of the simulated well outer cylinder is sealed with an outer cylinder bottom cover plate.

[0009] The support mechanism is vertically connected to the base, and the top of the support mechanism is connected to the simulated well outer cylinder. The support mechanism is used to support the simulated well outer cylinder and adjust its inclination.

[0010] A laser sensor is connected to the lower part of the inner cylinder connecting mechanism;

[0011] A laser sensor controller is installed outside the outer cylinder of the simulated well casing, and there is an electrical signal connection between the laser sensor controller and the laser sensor.

[0012] The simulated wellbore inner cylinder is horizontally connected to the simulated wellbore outer cylinder via an inner cylinder connecting mechanism, and a nozzle is connected to the rear end of the simulated wellbore inner cylinder.

[0013] The drive mechanism is rotatably connected to the inner cylinder of the simulated wellbore via a power transmission mechanism.

[0014] The liquid storage mechanism is connected to an inlet pipe and an outlet pipe. The inlet pipe is connected to the inside of the simulated well barrel through the top cover plate of the outer cylinder, and the outlet pipe is connected to the annulus of the outer cylinder and the inner cylinder of the simulated well barrel through the top cover plate of the outer cylinder.

[0015] The pressurizing mechanism is connected to the bottom cover plate of the outer cylinder;

[0016] The heating mechanism is connected to the bottom cover plate of the outer cylinder.

[0017] The simulated well outer cylinder is a hollow cylinder with open ends made of transparent material; its inner diameter is 117mm-311mm and its length is 0.5-50m; the measuring platform is a rectangular plate structure with multiple through holes at equal intervals, and each through hole is connected to a filtrate collection mechanism; the pressure resistance range of both the simulated well outer cylinder and the simulated well inner cylinder is 0-10MPa and the temperature range is room temperature-150℃.

[0018] The filtrate collection mechanism includes a filter paper cover, a filtrate guide pipe, and a filtrate collection box. The filter paper cover is connected to the upper surface of the measuring platform, the filtrate collection box is fixedly connected to the lower surface of the measuring platform, the filtrate guide pipe is placed in the through hole of the measuring platform, and the filter paper cover and the filtrate collection box are connected by the filtrate guide pipe. A valve is installed on the filtrate guide pipe located on the outer cylinder of the simulated well.

[0019] It also includes a camera; the camera is mounted on a base outside the simulated well casing and faces the center of the measuring platform.

[0020] The supporting mechanism includes a support rod and a wellbore inclination adjustment rod; the support rod and the wellbore inclination adjustment rod are vertically fixed to both sides of the base; the two ends of the simulated wellbore outer cylinder are horizontally fixed to the base through the support rod and the wellbore inclination adjustment rod; the inner cylinder connection mechanism includes multiple inner cylinder supports and multiple inner cylinder support lifting rings; the multiple inner cylinder supports are of the same length and are vertically fixed to the upper inner side wall of the simulated wellbore outer cylinder, and the bottom end of each inner cylinder support is connected to an inner cylinder support lifting ring, and the simulated wellbore inner cylinder is fixed inside the simulated wellbore outer cylinder through multiple inner cylinder support lifting rings; the bottom of each inner cylinder support lifting ring is connected to a laser sensor; the driving mechanism uses a stirring motor, and the power transmission mechanism uses a coupling, the outer end of the coupling is connected to the stirring motor placed outside the simulated wellbore outer cylinder, and the inner end of the coupling is connected to one end of the simulated wellbore inner cylinder.

[0021] The simulated wellbore inner cylinder comprises multiple cylinder sections and multiple inner cylinder couplings; adjacent cylinder sections are connected by inner cylinder couplings; the outer diameter of the inner cylinder coupling is 100-300% of the outer diameter of the simulated wellbore inner cylinder; each cylinder section is a hollow cylinder with an outer diameter of 89mm-152mm; the total length of the simulated wellbore inner cylinder is 0.3-49m.

[0022] The liquid storage mechanism is a liquid storage tank, which includes a tank body, a liquid supply pump, and a liquid supply pump controller. The liquid supply pump is located inside the tank body and at the lower part of the tank body's output end. The outer port of the liquid inlet pipe is connected to the liquid supply pump. The outer end of the liquid outlet pipe is connected to the inside of the tank body. The liquid supply pump controller is connected to the tank body and is electrically connected to the liquid supply pump.

[0023] The pressurization mechanism includes a gas source pressure divider and an air intake valve rod; one end of the air intake valve rod is connected to the interior of the simulated well outer cylinder through the bottom cover plate of the outer cylinder, and the other end of the air intake valve rod is connected to the gas source pressure divider.

[0024] The heating mechanism is an electric heating rod; the electric heating rod is connected to the bottom cover plate of the outer cylinder; the front end of the electric heating rod extends into the annulus between the outer cylinder and the inner cylinder of the simulated well.

[0025] A test method for a simulated wellbore filtration loss measurement and filter cake evaluation device includes the following steps:

[0026] Step 1: If a dynamic filtration loss test of drilling fluid is to be conducted, proceed to Step 2; if a quality evaluation test of the filter cake formed by drilling fluid is to be conducted, proceed to Step 8.

[0027] Step 2: Fix the filtrate collection mechanism to the measuring platform, then fix the measuring platform to the inner bottom surface of the outer cylinder of the simulated well, install the bottom cover plate and top cover plate of the outer cylinder, connect the heating mechanism, and connect the pressurization mechanism to the external air source;

[0028] Step 3: Adjust the wellbore inclination adjustment rod to adjust the outer cylinder of the simulated wellbore to the preset inclination angle;

[0029] Step 4: Fill the storage tank with the drilling fluid to be tested. First, run the supply pump at a flow rate of 3-8 L / s to fill the outer and inner cylinders of the simulated wellbore with the drilling fluid to be tested and establish circulation.

[0030] Step 5: Turn on the stirring motor. Driven by the stirring motor, the simulated well inner cylinder rotates until the simulated well inner cylinder reaches the preset test speed.

[0031] Step Six: When the temperature and pressure of the annulus of the simulated well outer cylinder and the simulated well inner cylinder reach the preset values ​​for the test, adjust the discharge rate of the liquid supply pump to the required discharge rate for the test, start the laser sensor, and start timing;

[0032] Step 7: Open the valve on the filtrate guide tube to allow the filtrate to flow into the filtrate collection box, and observe and record the filter cake formation process; after the preset test time has ended, record the final values ​​of the filtrate volume in the filtrate collection box and the filter cake thickness displayed on the laser sensor controller.

[0033] Step 8: Fix the filter paper containing the filter cake obtained from the API filter loss tester onto the filter paper cover plate on the measuring platform. Then, fix the measuring platform to the bottom surface of the outer cylinder of the simulated well. Install the bottom cover plate and the top cover plate of the outer cylinder. Turn on the heating mechanism and connect the pressurizing mechanism to the external air source.

[0034] Step 9: Repeat step 3;

[0035] Step 10: Fill the storage tank with clean water or drilling fluid. First, run the supply pump at a flow rate of 3-8L / s to fill the outer and inner cylinders of the simulated well with clean water or drilling fluid and establish circulation.

[0036] Step 11: Repeat steps 5 and 6;

[0037] Step 12: Close the valve on the filtrate guide pipe to prevent the flowing drilling fluid from producing filtrate. Observe and photograph the process of the filter cake being washed and destroyed by the drilling fluid. Record the filter cake thickness displayed on the laser sensor controller at preset time intervals. This filter cake thickness value is used for subsequent evaluation of the filter cake quality.

[0038] Beneficial effects:

[0039] (1) The present invention can perform dynamic filtration loss and filter cake quality evaluation tests of drilling fluid, overcoming the shortcomings of existing API drilling fluid filtration loss meters and measurement methods that cannot effectively guide on-site production.

[0040] (2) The outer cylinder of the simulated wellbore of the present invention is made of a transparent material that is resistant to high temperature and high pressure. The drilling fluid can be observed visually during fluid flow, nozzle injection, and agitation of the simulated wellbore inner cylinder and inner cylinder coupling, as well as the process and form of filter cake formation and destruction.

[0041] (3) The present invention has high simulation accuracy, simple operation, stable performance and strong reliability.

[0042] (4) The present invention has a simple structure and low manufacturing cost, which is conducive to its promotion and application.

[0043] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the structure of the device of the present invention.

[0046] In the diagram: 1. Simulated well outer cylinder; 2. Simulated well inner cylinder; 3. Inner cylinder coupling; 4. Inner cylinder support; 5. Inner cylinder support lifting ring; 6. Outer cylinder bottom cover plate; 7. Outer cylinder top cover plate; 8. Coupling; 9. Stirring motor; 10. Electric heating rod; 11. Gas source pressure divider; 12. Measuring platform; 13. Filter paper cover plate; 14. Filtrate guide pipe; 15. Filtrate collection box; 16. Laser sensor; 17. Base; 18. Support rod; 19. Well inclination adjustment rod; 20. Liquid inlet pipe; 21. Liquid outlet pipe; 22. Storage tank; 23. Liquid supply pump; 24. Liquid supply pump controller; 25. Laser sensor controller; 26. Nozzle; 27. Tank body; 28. Air inlet valve rod. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1:

[0049] according to Figure 1 The simulated wellbore filtration loss measurement and filter cake evaluation device shown includes:

[0050] Base 17,

[0051] The simulated well outer cylinder 1 has a measuring platform 12 connected to the bottom inner wall of the simulated well outer cylinder 1. Multiple filtrate collection mechanisms are connected at intervals on the measuring platform 12. An inner cylinder connecting mechanism is fixedly connected to the top side wall of the simulated well outer cylinder 1. The front end of the simulated well outer cylinder 1 is sealed with an outer cylinder top cover plate 7. A power transmission mechanism is connected to the outer cylinder top cover plate 7. The rear end of the simulated well outer cylinder 1 is sealed with an outer cylinder bottom cover plate 6.

[0052] The support mechanism is vertically connected to the base 17, and the top of the support mechanism is connected to the simulated well outer cylinder 1. The support mechanism is used to support the simulated well outer cylinder 1 and adjust its inclination.

[0053] Laser sensor 16 is connected to the lower part of the inner cylinder connecting mechanism;

[0054] A laser sensor controller 25 is installed outside the outer cylinder 1 of the simulated well casing, and the laser sensor controller 25 is electrically connected to the laser sensor 16.

[0055] The simulated well inner cylinder 2 is horizontally connected to the simulated well outer cylinder 1 through an inner cylinder connecting mechanism. A nozzle 26 is connected to the rear end of the simulated well inner cylinder 2.

[0056] The drive mechanism is rotatably connected to the inner cylinder 2 of the simulated wellbore via a power transmission mechanism;

[0057] The liquid storage mechanism is connected to an inlet pipe 20 and an outlet pipe 21. The inlet pipe 20 is connected to the inside of the inner cylinder 2 of the simulated well through the top cover plate 7 of the outer cylinder. The outlet pipe 21 is connected to the annulus of the outer cylinder 1 and the inner cylinder 2 of the simulated well through the top cover plate 7 of the outer cylinder.

[0058] A pressurizing mechanism is connected to the bottom cover plate 6 of the outer cylinder;

[0059] The heating mechanism is connected to the bottom cover plate 6 of the outer cylinder.

[0060] In practical applications, this invention can be used for filtration loss measurement and filter cake evaluation tests.

[0061] When measuring the dynamic filtration loss of drilling fluid using the device of the present invention, the following steps are performed:

[0062] The filtrate collection mechanism is fixed to the measuring platform 12, and then the measuring platform 12 is fixed to the inner bottom surface of the simulated wellbore outer cylinder 1. The outer cylinder bottom cover plate 6 and the outer cylinder top cover plate 7 are installed. The heating mechanism is turned on, and the pressurization mechanism is connected to the external air source. Then, the simulated wellbore outer cylinder 1 is adjusted to the preset inclination angle by adjusting the support mechanism. Subsequently, the drilling fluid to be tested is placed in the liquid storage mechanism, and the liquid storage mechanism starts to work. It first runs at a small displacement to fill the simulated wellbore outer cylinder 1 and simulated wellbore inner cylinder 2 with the drilling fluid to be tested and establish circulation. Then, the drive mechanism is turned on, and the simulated wellbore... The inner cylinder 2 rotates to reach the preset rotational speed of the simulated wellbore. When the temperature and pressure of the annulus between the outer cylinder 1 and the inner cylinder 2 of the simulated wellbore reach the preset values ​​of the test, the discharge capacity of the storage mechanism is adjusted to the required discharge capacity of the test, the laser sensor 16 is activated, and the timing begins. After the test time is completed, the filtrate collection mechanism starts to work, collects the filtrate, and observes and photographs the filter cake formation process. After the test time is completed, the final values ​​of the filtrate volume in the filtrate collection mechanism and the filter cake thickness displayed on the laser sensor controller 25 are recorded, thus obtaining the dynamic filtrate loss and filter cake thickness values ​​of the drilling fluid to be tested.

[0063] When using the apparatus of the present invention to conduct a quality evaluation test on the filter cake formed by drilling fluid, the following steps are performed:

[0064] First, the filtrate collection mechanism is fixed to the measuring platform 12. The filter paper cover 13 in the filtrate collection mechanism contains the filter paper containing the filter cake obtained from the API filtrate loss meter test. Then, the measuring platform 12 is fixedly connected to the inner bottom surface of the simulated well outer cylinder 1. The outer cylinder bottom cover 6 and the outer cylinder top cover 7 are installed. The heating mechanism is turned on, and the pressurization mechanism is connected to an external air source. Next, the support mechanism is adjusted to adjust the simulated well outer cylinder 1 to the preset inclination angle. Then, clean water or drilling fluid is filled into the storage mechanism, and the system is initially operated at a flow rate of 3-8 L / s to fill the simulated well outer cylinder 1 and simulated well inner cylinder 2 with clean water or drilling fluid, thus establishing a proper working order. Cycle; turn on the drive mechanism, and under the drive of the drive mechanism, the inner cylinder 2 of the simulated wellbore rotates, so that the rotation speed of the inner cylinder 2 of the simulated wellbore reaches the preset rotation speed of the test; when the temperature and pressure of the annulus of the outer cylinder 1 and the inner cylinder 2 of the simulated wellbore reach the preset value of the test, adjust the discharge capacity of the liquid storage mechanism to the required discharge capacity of the test, start the laser sensor 16, and start timing; then, close the filtrate guide pipe 14 in the filtrate collection mechanism so that the flowing drilling fluid cannot produce filtrate, observe and photograph the process of the filter cake being washed and destroyed by the drilling fluid, and record the filter cake thickness displayed by the laser sensor controller 25 at preset intervals. This filter cake thickness value is used for subsequent evaluation of the quality of the filter cake.

[0065] This invention enables dynamic filtration loss and filter cake quality evaluation tests for drilling fluid, overcoming the shortcomings of existing API drilling fluid filtration loss meters and measurement methods that cannot effectively guide on-site production.

[0066] This invention features high simulation accuracy, simple operation, stable performance, and strong reliability. Furthermore, it has a simple structure and low manufacturing cost, which facilitates its widespread application.

[0067] Example 2:

[0068] according to Figure 1 The simulated wellbore filtration loss measurement and filter cake evaluation device shown differs from Embodiment 1 in that: the simulated wellbore outer cylinder 1 is a hollow cylinder with open ends made of transparent material; its inner diameter is 117mm-311mm and its length is 0.5-50m; the measuring platform 12 is a rectangular plate structure with multiple through holes at equal intervals, each through hole connected to a filtrate collection mechanism; the pressure resistance range of both the simulated wellbore outer cylinder 1 and the simulated wellbore inner cylinder 2 is 0-10MPa, and the temperature range is room temperature-150℃.

[0069] Furthermore, the filtrate collection mechanism includes a filter paper cover plate 13, a filtrate guide pipe 14, and a filtrate collection box 15; the filter paper cover plate 13 is connected to the upper surface of the measuring platform 12, the filtrate collection box 15 is fixedly connected to the lower surface of the measuring platform 12, the filtrate guide pipe 14 is placed in the through hole of the measuring platform 12, and the filter paper cover plate 13 and the filtrate collection box 15 are connected by the filtrate guide pipe 14; a valve is provided on the filtrate guide pipe 14 located in the outer cylinder 1 of the simulated well.

[0070] In practical use, the measurement platform 12 adopts this technical solution, which allows for easy connection and fixation of the filtrate collection mechanism. The pressure resistance and heat resistance of the simulated well outer cylinder 1 and simulated well inner cylinder 2 are achieved using the above-mentioned technical solution, thus saving costs while meeting the actual requirements of the simulated drilling site.

[0071] When using the device of this invention to measure the dynamic filtration loss of drilling fluid, firstly, multiple API drilling fluid filter papers are placed and fixed on each filter paper cover plate 13. Then, the measuring platform is fixedly connected to the inner bottom surface of the simulated wellbore outer cylinder 1 before proceeding with subsequent test steps, thus conveniently measuring the dynamic filtration loss of the drilling fluid to be tested. When using the device of this invention to conduct a quality evaluation test of drilling fluid filter cake formation, firstly, multiple filter papers containing filter cake obtained from the API filtration loss meter test are fixed on each filter paper cover plate 13. Then, the measuring platform is fixedly connected to the inner bottom surface of the simulated wellbore outer cylinder 1 before proceeding with subsequent test steps, thus conveniently obtaining the dynamic filtration loss of drilling fluid and the thickness change of the drilling fluid filter cake under simulated real well site conditions, providing convenience for measuring the dynamic filtration loss of drilling fluid or evaluating the quality of drilling fluid filter cake formation.

[0072] The outer cylinder 1 of the simulated wellbore is made of transparent material, allowing visual observation of the drilling fluid's filtration loss, filter cake formation and destruction process and morphology under fluid flow, nozzle injection, and agitation of the inner cylinder and inner cylinder coupling. It also allows for testing of dynamic filtration loss and filter cake erosion resistance. Its inner diameter ranges from 117mm to 311mm, and its length from 0.5 to 50m, ensuring that this invention can meet the actual proportions of different sized wellbores and drill pipes in actual drilling processes, thus realistically simulating the actual drilling process.

[0073] The Chinese meaning of API above is American Petroleum Institute.

[0074] Example 3:

[0075] according to Figure 1 The simulated wellbore filtration loss measurement and filter cake evaluation device shown differs from Embodiment 1 in that it also includes a camera; the camera is mounted on a base 17 outside the simulated wellbore outer cylinder 1 and faces the center of the measurement platform 12.

[0076] In practical use, by setting up a camera, the process of mud cake formation is observed and recorded, as well as the specific conditions of mud cake formation at different time periods, such as density, thickness, roughness, and other visual characteristics, providing first-hand data for subsequent analysis and research.

[0077] Example 4:

[0078] according to Figure 1 The simulated wellbore filtration loss measurement and filter cake evaluation device shown differs from Embodiment 1 in that: the support mechanism includes a support rod 18 and a wellbore inclination adjustment rod 19; the support rod 18 and the wellbore inclination adjustment rod 19 are respectively vertically fixed on both sides of the base 17; both ends of the simulated wellbore outer cylinder 1 are horizontally fixed to the base 17 by the support rod 18 and the wellbore inclination adjustment rod 19; the inner cylinder connection mechanism includes multiple inner cylinder supports 4 and multiple inner cylinder support lifting rings 5; the multiple inner cylinder supports 4 are of the same length and vertically fixed. The inner cylinder 2 is attached to the upper inner wall of the outer cylinder 1 of the simulated well. Each inner cylinder support 4 is connected to an inner cylinder support ring 5 at its bottom. The inner cylinder 2 of the simulated well is fixed inside the outer cylinder 1 of the simulated well through multiple inner cylinder support rings 5. Each inner cylinder support ring 5 is connected to a laser sensor 16 at its bottom. The driving mechanism is a stirring motor 9, and the power transmission mechanism is a coupling 8. The outer end of the coupling 8 is connected to the stirring motor 9 located outside the outer cylinder 1 of the simulated well, and the inner end of the coupling 8 is connected to one end of the inner cylinder 2 of the simulated well.

[0079] In this embodiment, the outer cylinder support rod and the wellbore inclination adjustment rod fix the simulated wellbore outer cylinder 1. The support rod 18 is located at the bottom of the front end of the simulated wellbore outer cylinder 1, and has a fixed length but cannot be extended or retracted. The wellbore inclination adjustment rod 19 is located at the bottom of the rear end of the simulated wellbore outer cylinder 1 and has extension and retraction capabilities. By changing the length of the wellbore inclination adjustment rod 19, the simulated wellbore outer cylinder 1 can be adjusted to different well inclinations. The well inclination range is less than 75°. The well inclination is the angle between the central axis of the simulated wellbore outer cylinder 1 and the vertical line.

[0080] In this embodiment, to ensure that the simulated wellbore inner cylinder 2 operates normally under the drive of the stirring motor 9, a rotary seal is connected to each end of the coupling 8. One rotary seal is used to connect to the simulated wellbore inner cylinder 2, and the other rotary seal is connected to the inlet pipe 20, so that the drilling fluid enters the simulated wellbore inner cylinder 2 while the inner wellbore is rotating.

[0081] In practical use, in order to ensure that the simulated well outer cylinder 1 is placed stably, well cylinder seats are horizontally set at the top of both the support rod 18 and the well cylinder inclination adjustment rod 19. The top of the well cylinder seat is an arc shape that matches the simulated well outer cylinder 1. A clamp for fixing the simulated well outer cylinder 1 is connected to the well cylinder seat set at the top of the well cylinder inclination adjustment rod 19, so that the simulated well outer cylinder 1 is more stable when it is tilted.

[0082] Example 5:

[0083] according to Figure 1 The simulated wellbore filtration loss measurement and filter cake evaluation device shown differs from Embodiment 1 in that: the simulated wellbore inner cylinder 2 includes multiple cylinder sections and multiple inner cylinder couplings 3; each cylinder section is a hollow cylinder with an outer diameter of 89mm-152mm and a length of 0.3-49m; adjacent cylinder sections are connected by inner cylinder couplings 3; the outer diameter of the inner cylinder couplings 3 is 100-300% of the outer diameter of the simulated wellbore inner cylinder 2.

[0084] In practical use, the hollow cylinder body allows fluid to flow inside. The outer diameter of the inner cylinder coupling 3 adopts a technical solution that simulates the outer diameter of the inner cylinder 2 of the wellbore. The purpose is to simulate the drill string coupling in the actual drilling process, so as to evaluate the influence of the coupling on the flow pattern and velocity of the drilling fluid in the wellbore, as well as the influence of changes in the flow pattern and velocity of the drilling fluid on the movement of cuttings.

[0085] Example 6:

[0086] according to Figure 1 The simulated wellbore filtration loss measurement and filter cake evaluation device shown differs from Embodiment 1 in that: the liquid storage mechanism uses a liquid storage tank 22, which includes a tank body 27, a liquid supply pump 23, and a liquid supply pump controller 24; the liquid supply pump 23 is placed inside the tank body 27 and located at the lower part of the output end side of the tank body 27; the outer port of the liquid inlet pipe 20 is connected to the liquid supply pump 23; the outer end of the liquid outlet pipe 21 is connected to the interior of the tank body 27; and the liquid supply pump controller 24 is connected to the tank body 27, and the liquid supply pump controller 24 is electrically connected to the liquid supply pump 23.

[0087] In actual use, the start-up of the fluid supply pump 23 is controlled by the fluid supply pump controller 24. The drilling fluid to be tested, located in the storage tank 22, enters the simulated wellbore inner cylinder 2 through the inner port of the inlet pipe 20 under the action of the fluid supply pump 23. It then enters the annulus between the simulated wellbore inner cylinder 2 and the simulated wellbore outer cylinder 1 through the nozzle 26 connected to the rear end of the simulated wellbore inner cylinder 2. The drilling fluid in the annulus can also return to the tank 27 through the outlet pipe 21.

[0088] In this embodiment, the liquid supply pump 23 is an adjustable displacement pump with a displacement range of 0-15L / s.

[0089] The liquid supply pump controller 24 in this embodiment adopts existing technology and is used to control the opening, closing and discharge volume of the liquid supply pump 23.

[0090] Example 7:

[0091] according to Figure 1 The simulated wellbore filtration loss measurement and filter cake evaluation device shown differs from Embodiment 1 in that: the pressurization mechanism includes a gas source pressure divider 11 and an air inlet valve rod 28; one end of the air inlet valve rod 28 is connected to the interior of the simulated wellbore outer cylinder 1 through the outer cylinder bottom cover plate 6, and the other end of the air inlet valve rod 28 is connected to the gas source pressure divider 11.

[0092] In actual use, the external air source is regulated by the air source pressure divider 11 and then input into the annulus between the outer cylinder 1 and the inner cylinder 2 of the simulated wellbore via the air inlet valve rod 28. This ensures the supply and stability of the pressure in the annulus, and ensures that the test can be closer to the actual downhole pressure, providing accurate data support for subsequent drilling fluid loss testing or filter cake evaluation tests.

[0093] Example 8:

[0094] according to Figure 1 The simulated wellbore filtration loss measurement and filter cake evaluation device shown differs from Embodiment 1 in that: the heating mechanism uses an electric heating rod 10; the electric heating rod 10 is connected to the bottom cover plate 6 of the outer cylinder; the front end of the electric heating rod 10 extends into the annulus between the outer cylinder 1 and the inner cylinder 2 of the simulated wellbore.

[0095] In actual use, the heating end, i.e. the front end, of the electric heating rod 10 is placed in the annulus between the outer cylinder 1 and the inner cylinder 2 of the simulated wellbore to heat the drilling fluid to be tested in the annulus. The rear end of the electric heating rod 10 is connected to an external power source.

[0096] The heating mechanism uses an electric heating rod 10 for heating, which makes the heating operation more flexible and convenient, and at a lower cost.

[0097] Example 9:

[0098] A test method for a simulated wellbore filtration loss measurement and filter cake evaluation device includes the following steps.

[0099] Step 1: If a dynamic filtration loss test of drilling fluid is to be conducted, proceed to Step 2; if a quality evaluation test of the filter cake formed by drilling fluid is to be conducted, proceed to Step 8.

[0100] Step 2: Fix the filtrate collection mechanism on the measuring platform 12, then fix the measuring platform 12 on the inner bottom surface of the outer cylinder 1 of the simulated well, install the bottom cover plate 6 and the top cover plate 7 of the outer cylinder, turn on the heating mechanism, and connect the pressurization mechanism to the external air source.

[0101] Step 3: Adjust the wellbore inclination adjustment rod 19 to adjust the simulated wellbore outer cylinder 1 to the preset inclination angle;

[0102] Step 4: Fill the storage tank 22 with the drilling fluid to be tested. First, run the supply pump 23 at a flow rate of 3-8L / s to fill the outer cylinder 1 and inner cylinder 2 of the simulated wellbore with the drilling fluid to be tested and establish circulation.

[0103] Step 5: Turn on the stirring motor 9. Driven by the stirring motor 9, the simulated well inner cylinder 2 rotates until the speed of the simulated well inner cylinder 2 reaches the preset speed of the test.

[0104] Step 6: When the temperature and pressure of the annulus of the simulated well outer cylinder 1 and the simulated well inner cylinder 2 reach the preset values ​​of the test, adjust the discharge rate of the liquid supply pump 23 to the required discharge rate of the test, start the laser sensor 16, and start timing;

[0105] Step 7: Open the valve on the filtrate guide tube 14 to allow the filtrate to flow into the filtrate collection box 15. Observe and record the filter cake formation process and the specific conditions of the filter cake formed at different time periods through the installed camera, such as the visual state of density, thickness, and roughness. After the preset test time is over, record the final value of the filtrate volume in the filtrate collection box 15 and the filter cake thickness displayed on the laser sensor controller 25.

[0106] Step 8: Fix the filter paper containing the filter cake obtained from the test on the API filter loss meter onto the filter paper cover plate 13 on the measuring platform 12. Then, fix the measuring platform 12 to the inner bottom surface of the outer cylinder 1 of the simulated well. Install the bottom cover plate 6 and the top cover plate 7 of the outer cylinder, turn on the heating mechanism, and connect the pressurizing mechanism to the external air source.

[0107] Step 9: Repeat step 3;

[0108] Step 10: Fill the storage tank 22 with clean water or drilling fluid. First, run the supply pump 23 at a flow rate of 3-8L / s to fill the outer cylinder 1 and inner cylinder 2 of the simulated well with clean water or drilling fluid and establish circulation.

[0109] Step 11: Repeat steps 5 and 6;

[0110] Step 12: Close the valve on the filtrate guide pipe 14 to prevent the flowing drilling fluid from producing filtrate. Observe and photograph the process of the filter cake being washed and destroyed by the drilling fluid. Record the filter cake thickness displayed on the laser sensor controller 25 at preset intervals. This filter cake thickness value is used for subsequent evaluation of the quality of the filter cake.

[0111] The method used accurately reflects the actual drilling process, and the data obtained can effectively guide on-site construction.

[0112] Example 10:

[0113] An experiment was conducted to investigate the effect of Na2SO4 content in drilling fluid on its filtration performance using a simulated wellbore filtration loss measurement and filter cake evaluation device.

[0114] (1) Four groups of drilling fluid base slurries were prepared with the following formula: 2% bentonite + 0.05% NaOH + 0.2% xanthan gum + 0.2% filtration loss reducer + 2% emulsified asphalt + 5% limestone. 0%, 5%, 10% and 15% Na2SO4 were added respectively to test the effect of Na2SO4 addition on drilling fluid filtration loss and filter cake quality.

[0115] (2) Place the API drilling fluid filter paper on the filter paper cover plate of the measuring platform, then fix the measuring platform on the inner bottom surface of the outer cylinder of the simulated well, install the bottom cover plate and the top cover plate of the outer cylinder, connect the heating rod, and connect the gas source pressure divider in the pressurization mechanism to the external gas source.

[0116] (3) Adjust the wellbore inclination adjustment rod to adjust the simulated outer cylinder to a 45° angle with the vertical line;

[0117] (3) The above four types of drilling fluid to be tested are placed in the storage tank one after another. First, the supply pump is run at a small displacement of 6L / s to fill the inner cylinder and outer cylinder of the simulated well with the drilling fluid to be tested and establish circulation.

[0118] (4) Start the stirring motor to make the inner cylinder rotate at 60 rpm;

[0119] (5) After the temperature and pressure of the inner and outer cylinder annulus reach the test settings of 70℃ and 3.5MPa, adjust the liquid supply pump displacement to 15L / s and start timing;

[0120] (6) Open the filtrate guide tube to allow the filtrate to flow into the filtrate collection box, and observe and photograph the filter cake formation process. After 30 minutes, record the filtrate volume (FL). 动 FL 动 This is the dynamic filtration loss, and it is compared with the API filtration loss (static filtration loss FL) measured under the same conditions. 静 Compare the results; record the final value of the filter cake thickness displayed by the laser sensor controller as d.

[0121] Table 1. Effects of Na2SO4 dosage on drilling fluid filtration loss and filter cake thickness.

[0122]

[0123]

[0124] As shown in Table 1, with the increase of Na2SO4 content, the static filtration loss measurement value changes relatively little and without a certain pattern. However, the simulated dynamic filtration loss value changes significantly and exhibits a clear regularity: as the amount of K2SO4 increases, the filtration loss increases and the mud cake becomes thicker. Therefore, the data obtained using this invention makes it easier to derive experimental patterns and better evaluate the influence of the treatment agent on drilling fluid filtration loss.

[0125] Example 11:

[0126] A comparative test was conducted on the filter cake quality of drilling fluids with the same static filtration loss using a simulated wellbore filtration loss measurement and filter cake evaluation device.

[0127] (1) Take four portions of drilling fluid used at the drilling site (marked as A, B, C, and D respectively). The API low temperature and low pressure filtration loss of each portion is 6 mL and the filter cake mass is 1.2 mm. The quality of the four portions of drilling fluid is further evaluated through this invention.

[0128] (2) Measure the filtration loss of 4 parts of drilling fluid using an API low-temperature low-pressure filtration loss meter and obtain 4 filter cakes. Place the 4 filter cakes on the filter paper cover plate of the measuring platform one after another. Then fix the measuring platform on the bottom surface of the outer cylinder of the simulated well. Install the bottom cover plate and the top cover plate of the outer cylinder. Connect the heating rod and connect the gas source pressure divider in the pressurization mechanism to the external gas source.

[0129] (3) Adjust the wellbore inclination adjustment rod to adjust the simulated outer cylinder to a 45° angle with the vertical line;

[0130] (3) The above four types of drilling fluid to be tested are placed in the storage tank one after another. First, the supply pump is run at a small displacement of 8L / s to fill the inner cylinder and outer cylinder of the simulated well with the drilling fluid to be tested and establish a good circulation.

[0131] (4) Start the stirring motor to make the inner cylinder of the simulated well reach a speed of 60 rpm;

[0132] (5) After the temperature and pressure of the annulus of the inner and outer cylinders of the simulated well reach the 70℃ and 3.5MPa set for the test, adjust the flow rate of the liquid supply pump to 15L / s and start timing;

[0133] (6) Close the filtrate guide pipe to prevent the flowing drilling fluid from producing filtrate. Observe and photograph the process of the filter cake being washed away and destroyed by the drilling fluid. Record the filter cake thickness displayed on the laser sensor controller every 10 minutes. The test time is 60 minutes. The thicknesses are recorded as d0 and d1 respectively. 10 d 20 d 30 d 40 d 50 and d 60This is used to evaluate the quality of the filter cake.

[0134] Table 2. Thickness of filter cake formed by four drilling fluids after different flushing times.

[0135] sample <![CDATA[d0 / mm]]> <![CDATA[d 10 / mm]]> <![CDATA[d 20 / mm]]> <![CDATA[d 30 / mm]]> <![CDATA[d 40 / mm]]> <![CDATA[d 50 / mm]]> <![CDATA[d 60 / mm]]> Filter cake A 1.2 1.2 1.1 1.05 1.0 1.0 1.0 Filter cake B 1.2 1.0 0.9 0.6 0.2 0 0 Filter cake C 1.2 1.05 1.0 1.0 1.0 0.85 0.8 Filter cake D 1.2 1.0 0.8 0.65 0.50 0.45 0.3

[0136] As shown in Table 2, although the API low-temperature low-pressure filtration loss and filter cake thickness of the four drilling fluids are the same, the values ​​of the filter cake under dynamic scouring conditions are quite different. Filter cake A has the smallest change before and after the test, indicating that it has the strongest scouring resistance and the best filter cake quality. Filter cake B has the largest change, indicating that it has the weakest scouring resistance and the worst filter cake quality.

[0137] In summary, this invention can intuitively measure the quality of filter cakes formed by different drilling fluids.

[0138] This invention can be applied to the dynamic filtration loss and filter cake quality testing of drilling fluid under different conditions, depending on experimental needs.

[0139] Where there is no conflict, those skilled in the art can combine the relevant technical features in the above examples according to the actual situation to achieve the corresponding technical effects. Specific details of the various combinations will not be elaborated here.

[0140] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0141] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0142] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. Any simple modifications, equivalent variations, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the present invention.

Claims

1. A device for simulating wellbore filtration loss measurement and filter cake evaluation, characterized in that: include Base (17) The simulated well outer cylinder (1) has a measuring platform (12) connected to the bottom inner wall of the simulated well outer cylinder (1), and multiple filtrate collection mechanisms are connected at intervals on the measuring platform (12). The inner cylinder connecting mechanism is fixedly connected to the top side wall of the simulated well outer cylinder (1). The front end of the simulated well outer cylinder (1) is sealed with an outer cylinder top cover plate (7), and a power transmission mechanism is connected to the outer cylinder top cover plate (7). The rear end of the simulated well outer cylinder (1) is sealed with an outer cylinder bottom cover plate (6). The support mechanism is vertically connected to the base (17), and the top of the support mechanism is connected to the simulated well outer cylinder (1). The support mechanism is used to support the simulated well outer cylinder (1) and adjust its inclination. Laser sensor (16) is connected to the lower part of the inner cylinder connecting mechanism; A laser sensor controller (25) is installed outside the outer cylinder (1) of the simulated well casing. The laser sensor controller (25) is electrically connected to the laser sensor (16). The simulated well inner cylinder (2) is horizontally connected to the simulated well outer cylinder (1) through the inner cylinder connecting mechanism. The rear end of the simulated well inner cylinder (2) is connected to a nozzle (26). The drive mechanism is rotatably connected to the inner cylinder (2) of the simulated wellbore through a power transmission mechanism; The liquid storage mechanism is connected to an inlet pipe (20) and an outlet pipe (21). The inlet pipe (20) is connected to the inside of the inner cylinder (2) of the simulated well through the top cover plate (7) of the outer cylinder. The outlet pipe (21) is connected to the annulus of the outer cylinder (1) and the inner cylinder (2) of the simulated well through the top cover plate (7). A pressurizing mechanism is connected to the bottom cover plate (6) of the outer cylinder; Heating mechanism, the heating mechanism is connected to the bottom cover plate (6) of the outer cylinder; The filtrate collection mechanism includes a filter paper cover plate (13), a filtrate guide pipe (14), and a filtrate collection box (15). The filter paper cover plate (13) is connected to the upper surface of the measuring platform (12), the filtrate collection box (15) is fixedly connected to the lower surface of the measuring platform (12), the filtrate guide pipe (14) is placed in the through hole of the measuring platform (12), and the filter paper cover plate (13) and the filtrate collection box (15) are connected by the filtrate guide pipe (14). A valve is provided on the filtrate guide pipe (14) located on the outer cylinder (1) of the simulated well.

2. The simulated wellbore filtration loss measurement and filter cake evaluation device as described in claim 1, characterized in that: The simulated well outer cylinder (1) is a hollow cylinder with open ends made of transparent material; its inner diameter is 117mm-311mm and its length is 0.5-50m; the measuring platform (12) is a rectangular plate structure with multiple through holes at equal intervals on it, and a filtrate collection mechanism is connected to each through hole; the pressure resistance range of the simulated well outer cylinder (1) and the simulated well inner cylinder (2) is 0-10MPa and the temperature range is room temperature-150℃.

3. The simulated wellbore filtration loss measurement and filter cake evaluation device as described in claim 1, characterized in that: It also includes a camera; the camera is mounted on a base (17) outside the simulated well casing (1) and is directly facing the middle of the measuring platform (12).

4. The simulated wellbore filtration loss measurement and filter cake evaluation device as described in claim 1, characterized in that: The support mechanism includes a support rod (18) and a wellbore inclination adjustment rod (19); the support rod (18) and the wellbore inclination adjustment rod (19) are respectively vertically fixed on both sides of the base (17); the two ends of the simulated wellbore outer cylinder (1) are horizontally fixed on the base (17) through the support rod (18) and the wellbore inclination adjustment rod (19); the inner cylinder connection mechanism includes multiple inner cylinder supports (4) and multiple inner cylinder support lifting rings (5); the multiple inner cylinder supports (4) are of the same length and are vertically fixed to the upper inner sidewall of the simulated wellbore outer cylinder (1), each The bottom end of each inner cylinder support (4) is connected to an inner cylinder support lifting ring (5). The simulated well inner cylinder (2) is fixed inside the simulated well outer cylinder (1) by multiple inner cylinder support lifting rings (5). The bottom of each inner cylinder support lifting ring (5) is connected to a laser sensor (16). The driving mechanism is a stirring motor (9), and the power transmission mechanism is a coupling (8). The outer end of the coupling (8) is connected to the stirring motor (9) placed outside the simulated well outer cylinder (1), and the inner end of the coupling (8) is connected to one end of the simulated well inner cylinder (2).

5. A simulated wellbore filtration loss measurement and filter cake evaluation device as described in claim 1 or 4, characterized in that: The simulated wellbore inner cylinder (2) includes multiple cylinder sections and multiple inner cylinder couplings (3); adjacent cylinder sections are connected by inner cylinder couplings (3); the outer diameter of the inner cylinder couplings (3) is 100-300% of the outer diameter of the simulated wellbore inner cylinder (2); each cylinder section is a hollow cylinder with an outer diameter of 89mm-152mm; the total length of the simulated wellbore inner cylinder (2) is 0.3-49m.

6. The simulated wellbore filtration loss measurement and filter cake evaluation device as described in claim 1, characterized in that: The liquid storage mechanism is a liquid storage tank (22), which includes a tank body (27), a liquid supply pump (23), and a liquid supply pump controller (24). The liquid supply pump (23) is located inside the tank body (27) and at the lower part of the output end of the tank body (27). The outer port of the liquid inlet pipe (20) is connected to the liquid supply pump (23). The outer end of the liquid outlet pipe (21) is connected to the inside of the tank body (27). The liquid supply pump controller (24) is connected to the tank body (27), and the liquid supply pump controller (24) is electrically connected to the liquid supply pump (23).

7. The simulated wellbore filtration loss measurement and filter cake evaluation device as described in claim 1, characterized in that: The pressurization mechanism includes a gas source pressure divider (11) and an air intake valve rod (28); one end of the air intake valve rod (28) is connected to the interior of the simulated well outer cylinder (1) through the outer cylinder bottom cover plate (6), and the other end of the air intake valve rod (28) is connected to the gas source pressure divider (11).

8. The simulated wellbore filtration loss measurement and filter cake evaluation device as described in claim 1, characterized in that: The heating mechanism is an electric heating rod; the electric heating rod is connected to the bottom cover plate (6) of the outer cylinder; the front end of the electric heating rod extends into the annulus between the outer cylinder (1) and the inner cylinder (2) of the simulated well.

9. The test method for a simulated wellbore filtration loss measurement and filter cake evaluation device as described in any one of claims 1-8, characterized in that: Includes the following steps: Step 1: If a dynamic filtration loss test of drilling fluid is to be conducted, proceed to Step 2; if a quality evaluation test of the filter cake formed by drilling fluid is to be conducted, proceed to Step 8. Step 2: Fix the filtrate collection mechanism on the measuring platform (12), then fix the measuring platform (12) on the inner bottom surface of the outer cylinder (1) of the simulated well, install the bottom cover plate (6) and the top cover plate (7) of the outer cylinder, turn on the heating mechanism, and connect the pressurizing mechanism to the external gas source; Step 3: Adjust the wellbore inclination adjustment rod (19) to adjust the simulated wellbore outer cylinder (1) to the preset inclination angle; Step 4: Fill the storage tank (22) with the drilling fluid to be tested. First, run the supply pump (23) at a flow rate of 3-8L / s to fill the simulated well outer cylinder (1) and simulated well inner cylinder (2) with the drilling fluid to be tested and establish circulation. Step 5: Turn on the stirring motor (9). Driven by the stirring motor (9), the simulated well inner cylinder (2) rotates, so that the speed of the simulated well inner cylinder (2) reaches the preset speed of the test. Step 6: When the temperature and pressure of the annulus of the simulated well outer cylinder (1) and the simulated well inner cylinder (2) reach the preset values ​​of the test, adjust the discharge rate of the liquid supply pump (23) to the required discharge rate of the test, start the laser sensor (16), and start timing; Step 7: Open the valve on the filtrate guide tube (14) to allow the filtrate to flow into the filtrate collection box (15), and observe and record the filter cake formation process; after the preset test time is over, record the final values ​​of the filtrate volume in the filtrate collection box (15) and the filter cake thickness displayed on the laser sensor controller (25); Step 8: Fix the filter paper containing the filter cake obtained from the test on the API filter loss meter onto the filter paper cover plate (13) on the measuring platform (12). Then, fix the measuring platform (12) to the inner bottom surface of the outer cylinder (1) of the simulated well, install the bottom cover plate (6) and the top cover plate (7) of the outer cylinder, turn on the heating mechanism, and connect the pressurizing mechanism to the external air source. Step 9: Repeat step 3; Step 10: Fill the storage tank (22) with clean water or drilling fluid. First, run the supply pump (23) at a flow rate of 3-8L / s to fill the outer cylinder (1) and inner cylinder (2) of the simulated well with clean water or drilling fluid and establish a circulation. Step 11: Repeat steps 5 and 6; Step 12: Close the valve on the filtrate guide pipe (14) so ​​that the drilling fluid in the flow cannot produce filtrate. Observe and take pictures of the process of the filter cake being washed and destroyed by the drilling fluid. Record the filter cake thickness displayed by the laser sensor controller (25) at preset intervals. This filter cake thickness value is used for subsequent evaluation of the quality of the filter cake.

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