An evaluation device and method for a cementing interface under simulated differential pressure conditions

Abstract

The application discloses a kind of simulation differential pressure condition under cementing interface evaluation device and method, belong to oil and gas well cementing field.The device is cylindrical steel structure, upper fluid bin, lower fluid bin are connected with interface reaction loading bin respectively by sealing thread, form a closed space;Interface reaction loading bin outside is stainless steel pipeline, inner wall places sealed rubber sleeve, filter screen is set at the sealing thread where loading bin is connected with lower fluid bin, and core is fixed in the center of filter screen.The method comprises: injecting drilling fluid to form filter cake on core;After injecting cement slurry to submerge core, respectively inject curing fluid in upper and lower fluid bin to form pressure difference, and cure cement stone;Filter screen is replaced with support ring, continuously pressurize in upper fluid bin by pressure control pump, until flowmeter in lower fluid bin shows stable reading, and cement sheath interface cementing strength is calculated.The application is reasonable in design, convenient to use, and the evaluation result is accurate and reliable, which can provide technical support for improving cementing quality.

Description

Technical Field

[0001] This invention relates to a cementing interface evaluation device and method under simulated differential pressure conditions, belonging to the field of oil and gas well cementing technology. Background Technology

[0002] Cementing is one of the most critical steps in oil and gas well construction. The quality of cementing not only affects well safety but also the efficiency of oil and gas extraction. Therefore, the quality of cementing cement is particularly important. Cementing cement is a cement material used in the petroleum industry to fix the wellbore and prevent oil and gas leakage. The quality of cementing cement often depends on its bonding strength with the casing and formation.

[0003] During cementing, a cement slurry mixture is pumped downhole, forming a hardened protective layer between the wellbore and the tubing wall to prevent oil and gas leakage and wellbore collapse. As well depth increases, the temperature and pressure at the bottom of the well also increase, creating extremely large pressure and temperature differentials. These extreme pressure differentials and other harsh environmental conditions can cause the sealing performance of the cement sheath in oil and gas wells to fail, leading to oil and gas leakage from the cemented interface, severely impacting cementing safety and production efficiency. The goal of interface curing is to prevent leakage and insufficient adhesion between the cement sheath and the wellbore, ensuring the wellbore's sealing and strength. Interface evaluation of cement sheaths cured under pressure differential conditions will provide guidance for field operations.

[0004] Currently, both domestic and international devices and methods for the maintenance and evaluation of cement sheath interfaces have certain defects and shortcomings: "A cement sheath performance simulation device" (CN212201989U) adjusts the specifications of the cement sheath obtained after maintenance by changing the position of the upper limit ring, while the lower limit ring applies upward pressure to the cement sheath to simulate formation pressure. However, because it cannot realize the pressure difference between the upper and lower interfaces, it cannot truly simulate the pressure difference at the bottom of the well, resulting in discrepancies with actual working conditions. "A sample preparation device for testing the bonding strength of cement interface" (CN217006577U) simulates the bonding strength of the downhole cement sheath-casing interface by placing and fixing a simulated casing in the positioning groove of the base. When a solid core is placed and fixed in the positioning groove of the base, it can simulate the bonding strength of the downhole cement sheath-formation interface. However, the pressure and temperature considered are very limited, and it can only perform a simple one-time evaluation of the cement sheath, with limited guidance for actual working conditions. "A measuring device and method for measuring the bonding strength of the cementing interface before and after deformation of ultra-high temperature and high pressure casing" (CN114718551A) tests the bonding strength of the first interface between the casing and cement stone before and after deformation under the coupled action of high temperature and high pressure and the exothermic effect of cement hydration after cementing by simulating the high temperature and high pressure curing conditions of cement slurry under the formation. However, it only considers a single pressure and cannot truly simulate the pressure difference at the bottom of the well.

[0005] This invention proposes a device for cement stone interface curing and evaluation under simulated differential pressure conditions. The simulation results are highly reliable and have strong engineering applicability. It can be used to study the sealing performance of cement stone under differential pressure conditions and to accurately evaluate the bonding strength of cement stone interface under complex working conditions, thereby providing better technical support for improving cementing quality. Summary of the Invention

[0006] The purpose of this invention is to provide a cementing interface evaluation device under simulated differential pressure conditions. This device is reliable in principle, has a reasonable structural design, is easy to use, and has a low fault tolerance rate. While satisfying the requirement of curing the cement stone interface under differential pressure conditions, it can further test the interface bonding strength of the cement sheath after curing.

[0007] Another objective of this invention is to provide a method for evaluating the interfacial bonding strength of cement stone under simulated differential pressure conditions using the aforementioned device. By evaluating the interfacial bonding strength of cement sheath cured under differential pressure conditions, the influence of various complex environments on cement sheath can be analyzed, further guiding actual working conditions.

[0008] To achieve the above technical objectives, the present invention adopts the following technical solution.

[0009] A cementing interface evaluation device under simulated differential pressure conditions, consisting of an upper fluid chamber, an interface reaction loading chamber, and a lower fluid chamber from top to bottom.

[0010] Both the upper and lower fluid chambers are corrosion-resistant stainless steel cavities, which are connected to the interface reaction loading chamber via sealing threads, respectively, and apply pressure to the interface reaction loading chamber. The upper fluid chamber is equipped with a liquid inlet and valve, and a precision pressure control pump at the upper end, and a liquid outlet and valve at the lower end. The upper end of the lower fluid chamber is similar to that of the upper fluid chamber, and the liquid outlet and valve at the lower end are connected to a flow meter.

[0011] The interface reaction loading chamber is externally constructed of stainless steel pipes, which are connected to the upper and lower fluid chambers via sealing threads to form a sealed space. The stainless steel pipes are connected to a confining pressure pump, and a sealing rubber sleeve is placed on the inner wall. A filter screen is installed at the sealing thread connecting the interface reaction loading chamber and the lower fluid chamber, and a rock core is fixed in the center of the filter screen. The rock core is located at the center of the sealing rubber sleeve. The confining pressure pump applies pressure to the sealing rubber sleeve to form confining pressure.

[0012] The upper fluid chamber, lower fluid chamber, and interfacial reaction loading chamber are equipped with heating jackets, which are connected to temperature control devices.

[0013] When the fluid required for the experiment is added to the upper fluid chamber through the inlet and valve at its upper end, the outlet and valve should be closed, and the pressure should be controlled by a precision pressure control pump.

[0014] The method for evaluating the cement-stone interface bonding strength under simulated pressure difference conditions using the above-mentioned device includes the following steps: (1) Prepare drilling fluid and cement slurry according to the on-site working conditions; (2) Inject drilling fluid into the upper fluid chamber through the filling port and valve to submerge the core, let it stand until a filter cake forms outside the core, and then discharge the drilling fluid through the drain port and valve. (3) Inject cement slurry into the upper fluid chamber through the filling port and valve, so that the cement slurry submerges the rock core. Inject the required curing fluid into the upper and lower fluid chambers respectively, and control the required pressure through the confining pressure pump and the pressure control pump. The pressure in the upper fluid chamber is P. 上 The interface reaction loading chamber confining pressure is P 围 The pressure in the lower fluid chamber is P. 下 And P 上 >P 下 Turn on the temperature control device, set the temperature to the desired temperature, and cure to form cement stone; (4) Turn off the temperature control device, release the pressure through the pressure control pump, open the drain ports and valves of the upper and lower fluid chambers to drain the fluid, and close the drain port and valve of the upper fluid chamber; (5) Replace the filter screen with a support ring, open the drain port and valve of the lower fluid chamber, the drain port and valve are connected to the flow meter, and the pressure is continuously increased in the upper fluid chamber by the pressure control pump until the flow meter shows a stable reading, so as to calculate the bonding strength of the cement ring interface.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention simulates well interface curing under differential pressure conditions, truly simulating downhole working conditions and exploring the impact of different working conditions on cement sheath curing. After curing, it can also evaluate the interface, analyze the causes of cement sheath failure, accurately locate the causes of failure, and thus select the most suitable cement slurry system for different working conditions, providing better guidance for actual construction. Attached Figure Description

[0016] The accompanying drawings constitute the basis of this invention for a better understanding of the invention, and the illustrative embodiments thereof and their descriptions are for the purpose of explaining the invention and do not constitute an undue limitation of the invention.

[0017] Figure 1 This is a schematic diagram of a cement interface evaluation device under simulated pressure differential conditions.

[0018] Figure 2 This is a schematic diagram of testing the bonding strength of the cement stone interface by replacing the filter screen with the support ring 15.

[0019] In the diagram: 1-Filter screen, 2-Lower fluid chamber, 3-Sealing thread, 4-Rock core, 5-Sealing rubber sleeve, 6-Interfacial reaction loading chamber, 7-Upper fluid chamber, 8-Pressure pump, 9-Inlet and valve, 10-Outlet and valve, 11-Pressure control pump, 12-Temperature control device, 13-Heating jacket, 14-Flow meter, 15-Support ring. Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings to enable those skilled in the art to understand the invention. However, it should be understood that the present invention is not limited to the specific embodiments described herein. For those skilled in the art, any modifications that fall within the spirit and scope of the invention as defined and determined by the appended claims are protected.

[0021] See Figure 1 , Figure 2 .

[0022] A cementing interface evaluation device under simulated differential pressure conditions is a cylindrical steel structure consisting of an upper fluid chamber 7, an interface reaction loading chamber 6, and a lower fluid chamber 2, arranged from top to bottom. The upper fluid chamber 7 and the lower fluid chamber 2 are connected to the interface reaction loading chamber 6 via sealing threads 3, forming a sealed space.

[0023] The upper fluid chamber 7 is provided with a liquid inlet and valve 9 and a pressure control pump 11 at the upper end, and a liquid outlet and valve 10 at the lower end. The lower fluid chamber 2 is also provided with a liquid inlet and valve and a pressure control pump at the upper end, and a liquid outlet and valve at the lower end are connected to a flow meter 14.

[0024] The interface reaction loading chamber 6 is externally made of stainless steel pipes, which are connected to the upper fluid chamber and the lower fluid chamber respectively through sealing threads 3. The stainless steel pipes are connected to the confining pressure pump 8, and the inner wall is placed with a sealing rubber sleeve 5. A filter screen 1 is set at the sealing thread connecting the interface reaction loading chamber and the lower fluid chamber. A rock core 4 is fixed in the center of the filter screen. The rock core is located in the center of the sealing rubber sleeve. The confining pressure pump applies pressure to the inside of the sealing rubber sleeve to form confining pressure.

[0025] The upper fluid chamber, lower fluid chamber, and interface reaction loading chamber are equipped with heating jackets 13, which are connected to temperature control devices 12.

[0026] Furthermore, the upper fluid chamber and the lower fluid chamber apply a pressure difference to the interface reaction loading chamber through a pressure-controlled pump.

[0027] Furthermore, the sealing threads of the upper fluid chamber and the lower fluid chamber are internal sealing threads, and the sealing thread of the interface reaction loading chamber is an external sealing thread, with a sealing ring provided at the sealing thread to ensure the airtightness of the device.

[0028] Furthermore, the sealing ring and sealing rubber sleeve are made of materials that are resistant to high temperatures and corrosion.

[0029] Furthermore, when testing the cement-stone interface bonding strength, the filter screen is replaced with a support ring 15. The support ring is circular in shape, with an outer diameter equal to the diameter of the filter screen and an inner diameter slightly larger than the diameter of the rock core. When the pressure pump of the upper fluid chamber pressurizes to a certain level, the rock core can pass through the support ring and fall into the lower fluid chamber.

[0030] The above-mentioned device was used to simulate the curing and evaluation method of cement sheath interface under pressure difference conditions. The specific process is as follows: Prepare drilling fluid and cement slurry as needed; in the interface reaction loading chamber, place the filter screen at the sealing thread of the lower fluid chamber, with the rock core in the center of the filter screen, and then put the sealing rubber sleeve into the stainless steel pipe. Install the O-ring at the sealing thread, and connect the stainless steel pipe to the upper and lower fluid chambers through the sealing thread to form a closed space.

[0031] Drilling fluid is injected into the upper fluid chamber through the filling port and valves to form a filter cake outside the core. Cement slurry is then injected to fill the annular space between the core and the sealing rubber sleeve. All valves are closed, and the required curing fluid is injected into the upper and lower fluid chambers through the filling port and valves respectively. The required pressure is set using the confining pressure pump and the control pressure pump (pressure P in the upper fluid chamber). 上 The interface reaction loading chamber confining pressure is P 围 The pressure in the lower fluid chamber is P. 下 At this time P 围 =P 上 P 上 >P 下 Turn on the temperature control device and set the temperature to the desired temperature.

[0032] After the cement stone curing is completed, turn off the temperature control device and release the pressure through the pressure control pump. Then, open the drain valves of the upper and lower fluid chambers to drain all the fluid. Close all valves of the upper fluid chamber, unscrew the lower fluid chamber, and replace the filter screen with a support ring. At this time, open the drain port and valve of the lower fluid chamber and connect the drain port and valve to the flow meter. Continuously pressurize the upper fluid chamber through the pressure control pump until the flow meter displays a stable reading. This indicates that the interface between the cement stone and the core has been damaged and the interface has failed. The test ends, and the pressure control pump reading is recorded at this time.

[0033] By using the readings from the flow meter and the pressure-controlled pump, the bond strength of the cement ring interface after curing can be converted through relevant algorithms.

[0034] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the foregoing embodiments. Various simple modifications and transformations can be made within the technical concept of the present invention, and such modifications and transformations are all within the protection scope of the present invention.

Claims

1. A method for evaluating the bonding strength of cement stone interface under simulated pressure difference using a device. The device is a cylindrical steel structure consisting of an upper fluid chamber (7), an interface reaction loading chamber (6), and a lower fluid chamber (2) from top to bottom. The upper and lower fluid chambers are connected to the interface reaction loading chamber via sealing threads to form a closed space. The upper fluid chamber (7) is equipped with a liquid inlet and valve (9) and a pressure control pump (11) at its upper end, and a liquid outlet and valve (10) at its lower end. The lower fluid chamber (2) is also equipped with a liquid inlet and valve and a pressure control pump at its upper end, and a liquid outlet and valve at its lower end are connected to a flow meter (14). The interface reaction loading chamber (6) is equipped with a liquid inlet and valve and a pressure control pump at its upper end, and a liquid outlet and valve at its lower end are connected to a flow meter (14). The exterior is a stainless steel pipe, which is connected to the upper fluid chamber and the lower fluid chamber respectively through a sealing thread. The stainless steel pipe is connected to a confining pressure pump (8). A sealing rubber sleeve (5) is placed on the inner wall. A filter screen (1) is set at the sealing thread connecting the interface reaction loading chamber and the lower fluid chamber. A rock core (4) is fixed in the center of the filter screen. The rock core is located in the center of the sealing rubber sleeve. The exterior of the upper fluid chamber, the lower fluid chamber and the interface reaction loading chamber is equipped with a heating sleeve (13). The heating sleeve is connected to a temperature control device (12). When testing the cement stone interface bonding strength, the filter screen is replaced with a support ring (15). The support ring is circular in shape, with an outer diameter equal to the diameter of the filter screen and an inner diameter slightly larger than the diameter of the rock core. The method includes the following steps in sequence: (1) Prepare drilling fluid and cement slurry according to the on-site working conditions; (2) Inject drilling fluid into the upper fluid chamber through the filling port and valve to submerge the core, let it stand until a filter cake forms outside the core, and then discharge the drilling fluid through the drain port and valve. (3) Inject cement slurry into the upper fluid chamber through the filling port and valve, so that the cement slurry submerges the rock core. Inject the required curing fluid into the upper and lower fluid chambers respectively, and control the required pressure through the confining pressure pump and the pressure control pump. The pressure in the upper fluid chamber is P. 上 The interface reaction loading chamber confining pressure is P 围 The pressure in the lower fluid chamber is P. 下 And P 上 >P 下 Turn on the temperature control device, set the temperature to the desired temperature, and cure to form cement stone; (4) Turn off the temperature control device, release the pressure through the pressure control pump, open the drain ports and valves of the upper and lower fluid chambers to drain the fluid, and close the drain port and valve of the upper fluid chamber; (5) Replace the filter screen with a support ring, open the drain port and valve of the lower fluid chamber, the drain port and valve are connected to the flow meter, and the pressure is continuously increased in the upper fluid chamber by the pressure control pump until the flow meter shows a stable reading, so as to calculate the bonding strength of the cement ring interface.

2. The method as described in claim 1, characterized in that, The upper and lower fluid chambers apply a pressure difference to the interface reaction loading chamber via a pressure-controlled pump.

3. The method as described in claim 1, characterized in that, The sealing threads of the upper and lower fluid chambers are internal sealing threads, while the sealing thread of the interface reaction loading chamber is an external sealing thread, and a sealing ring is provided at the sealing thread to ensure sealing.

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