A method for casing lowering with full-process sealing and pressure control

Abstract

The present invention discloses a method for lowering casing with full-process sealing and pressure control, and belongs to the technical field of oil and gas cementing. It includes designing a set of sealing devices at the wellhead, and the sealing device includes a pipe section connected to the wellhead, an upper sealing structure and a lower sealing structure arranged in the pipe section; when lowering the casing with a centralizer, the upper sealing structure is opened, the annulus is closed by the lower sealing structure, and the casing is lowered normally; when the casing centralizer is lowered into the cavity between the upper sealing structure and the lower sealing structure, the upper sealing structure is closed; when the upper sealing structure completes the cavity closure, the lower sealing structure is opened, and the casing lowering operation is continued. After the casing centralizer is lowered into the wellbore as a whole, the lower sealing structure is closed again; and the pressure relief valve is used to discharge the pressurized drilling fluid in the cavity. The present invention can realize fast and safe casing lowering operation, improve the efficiency and safety of drilling and completion construction, and lay a good foundation for later fracturing transformation.

Description

Technical Field

[0001] The invention relates to the field of oil and gas cementing, and in particular to a casing lowering method with full-process sealing and pressure-controlled operation. Background Art

[0002] At present, casing can only be run in high-risk wells after the safe period is measured to be longer than the casing operation time under the condition of stable formation pressure and no leakage or overflow. The key measures of this method are as follows:

[0003] 1) When running casing without a centralizer section, the wellhead can be sealed with a rotating control head to ensure the safety of the casing running operation;

[0004] 2) Prepare the blowout prevention casing and circulation joint equipped with the rotating control head assembly. When there is a risk of overflow well control during the casing lowering process, quickly connect the blowout prevention casing and circulation joint with the rotating assembly. After the rotating assembly is seated to seal the wellhead, circulate the well to kill the well. At the same time, the casing can be moved to avoid complicated casing jams. The casing lowering operation can only be continued after the formation is stabilized by circulation. This method requires sufficient safety time to complete the connection of the rotating control head, connecting the casing, circulation joint and other tools, and cannot be implemented for wells with sudden overflow.

[0005] Wells with high well control risk, special process wells, advanced high-pressure water injection area wells, abnormal pressure reservoir wells, etc. are prone to overflow water, gas invasion, leakage and overflow during drilling and completion operations, which seriously affect the safety of drilling and completion. If the control is not timely, accidents such as blowouts may occur. At present, the pressure control equipment and supporting processes such as rotary control heads and throttling pressure control devices can be used to achieve the wellhead sealing and dynamic balance of bottom hole pressure during the drilling, tripping and cementing operations, and the safe operation capacity of drilling and completion is significantly improved. However, since there is no full-process sealing and pressure control technology matching the casing operation at home and abroad, it is impossible to achieve a full-process sealing and pressure control of the casing operation under abnormal wellbore pressure conditions, which makes it easy for overflow, leakage and overflow to occur during the casing operation of high well control and operation risk wells, and there are well control accidents that induce overflow blowouts, causing huge losses and impacts, and affecting the cementing quality and the service life of the well, and even posing a great threat to the safety of personnel and property. Therefore, in high-risk wells that require sealing or pressure-controlled casing, such as leaky blowout conversion risk wells, high-pressure and high-sulfur wells, and special process operation wells (full-process underbalanced wells, full-process controlled pressure drilling, gas drilling, etc.), it is urgent to solve the technical problems of safe casing lowering in order to further improve the safe operation capabilities of drilling and completion.

[0006] According to the search of published patents, there is currently no method for the full-process sealing of casing and casing centralizers and other completion pipe strings under abnormal wellbore pressure conditions. Therefore, it is urgent to propose a full-process sealing and pressure-controlled casing lowering method under abnormal wellbore pressure conditions to effectively solve the problems of overflow, leakage and overflow during the cementing of casing in wells with high well control risk, special process wells, advanced high-pressure water injection area wells, and abnormal pressure reservoir wells. Summary of the invention

[0007] In order to solve the problem that existing equipment and processes cannot achieve full-process sealed and pressure-controlled lowering of casing with a stabilizer, the present invention provides a method for lowering casing under full-process sealed and pressure-controlled conditions under abnormal wellbore pressure conditions, which can achieve full-process sealing, wellhead pressure control, circulation at any time, gas measurement and other operations during the casing lowering process, thereby improving the safety of casing lowering operations and construction efficiency.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0009] A method for casing lowering with full-process sealing and pressure control, characterized by comprising the following steps:

[0010] Step 1: design a sealing device at the wellhead, the sealing device comprising a pipe section connected to the wellhead, an upper sealing structure and a lower sealing structure arranged in the pipe section;

[0011] Step 2: When lowering the casing with the centralizer, open the upper sealing structure, use the lower sealing structure to close the annulus, and lower the casing normally;

[0012] Step 3: When the casing centralizer is lowered into the cavity between the upper sealing structure and the lower sealing structure, the upper sealing structure is closed;

[0013] Step 4: When the upper sealing structure completes the cavity sealing, open the lower sealing structure and continue the casing operation.

[0014] Step 5: After the casing centralizer is lowered into the wellbore as a whole, the lower sealing structure is closed again;

[0015] Step 6: Use the pressure relief valve to release the pressurized drilling fluid in the cavity.

[0016] In one embodiment, the method further includes step seven: after the pressure in the cavity is completely released, the upper sealing structure is opened, and the operations of steps one to six are cycled to continue the casing lowering operation and prepare to pass through the next casing centralizer.

[0017] In one embodiment, at each step in the casing lowering process, a pressure gauge and a flow meter are used to measure the wellbore annular pressure and the flow rate of the returned drilling fluid, respectively, and the inlet and outlet flows are compared in real time.

[0018] In one embodiment, during the casing running process, a pressure controlled throttle valve is used to adjust the wellhead back pressure.

[0019] In one embodiment, in step three, a positioner is used to detect the position of the casing centralizer, and an alarm is triggered when the casing centralizer is in the correct position in the cavity.

[0020] In one embodiment, in step 4, after the lower sealing structure is opened, the drilling fluid in the wellbore enters the cavity, and after the pressure in the cavity and the annulus reaches equilibrium, the casing lowering operation is continued.

[0021] In one embodiment, the locator is an infrared sensor.

[0022] In one embodiment, the pressure control throttle valve is installed on the cavity between the lower sealing structure and the wellhead.

[0023] In summary, the present invention has the following advantages:

[0024] 1. The present invention adopts an upper and lower sealing structure, and safely lowers the casing centralizer component with a larger diameter under pressure to achieve annular sealing and casing lowering. During the casing lowering process, the wellbore annular pressure and the return flow of drilling fluid are monitored in real time through a pressure gauge and a flow meter, and the inlet and outlet flows are compared. The wellhead pressure control throttle valve is used to adjust the wellhead back pressure to complete the pressure-controlled casing lowering, and a cycle can be established as needed at any process node to achieve the purpose of full-process pressure control during the drilling and completion cycle and dynamically balance the wellbore pressure;

[0025] 2. The present invention has the following three technical advantages: ① It realizes the sealing of the wellhead during the process of casing lowering and casing centralizer; ② It monitors the downhole complexities such as overflow, leakage, water outflow, gas invasion in real time through the pressure gauge and flow meter, and determines the timely pressure control according to the downhole formation conditions; ③ It realizes the circulation pressure control during the casing lowering process by adjusting the wellhead pressure control throttle valve, which is suitable for the supporting technology of safe drilling and completion of wells with abnormal reservoir pressure, realizes fast and safe casing lowering operation, improves the efficiency and safety of drilling and completion construction, and lays a good foundation for later fracturing transformation. It can be promoted and used in the water injection area of ​​Changqing area, with good application prospects and economic benefits.

[0026] 3. The present invention utilizes the whole process sealed and pressure controlled casing technology, which can eliminate the weak link of unsealed wellhead during the casing cementing process in wells with high well control risks and special process wells, thereby ensuring cementing safety and improving cementing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the first step of sealing and controlling the pressure of casing in the whole process of an embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of the second step of the casing lowering under sealed pressure in the whole process of the embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the third step of the casing lowering under sealed pressure in the whole process of the embodiment of the present invention;

[0030] Figure 4 It is a schematic diagram of the fourth step of sealing and controlling the pressure of the casing in the whole process of the embodiment of the present invention;

[0031] Figure 5 It is a schematic diagram of the fifth step of sealing and controlling the pressure of the casing in the whole process of the embodiment of the present invention;

[0032] Figure 6 It is a schematic diagram of the sixth step of sealing and controlling the pressure of the casing in the whole process of the embodiment of the present invention;

[0033] Figure 7 It is a schematic diagram of the seventh step of sealing and controlling the pressure of the casing in the whole process of the embodiment of the present invention;

[0034] In the figure,

[0035] 1. Casing, 2. Centralizer, 3. Upper sealing structure, 4. Lower sealing structure, 5. Positioner, 6. Pressure gauge, 7. Pressure relief valve, 8. Pressure gauge, flow meter, 9. Pressure control throttle valve, 10. Wellhead assembly, 11. Wellbore. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0037] In order to solve the problem of safe lowering of casing with centralizer, and realize the whole process sealing, wellhead pressure control, circulation at any time, gas measurement and other operations during the casing lowering process, the present invention provides a whole process sealing and pressure controlled casing lowering method. The specific design technical ideas of the method of the present invention are as follows: adopting the upper and lower two sealing structures and the step-by-step sealing method, the casing centralizer is safely passed under the condition of ensuring the annulus sealing.

[0038] At each node in the casing lowering process, the wellbore annular pressure and the return flow of drilling fluid can be measured by the pressure gauge and flowmeter. The inflow and outflow can be compared in real time during the grouting cycle. The return volume of drilling fluid and the volume of casing can be compared in real time during the casing lowering process. By comparing the whole process of casing lowering, it is possible to monitor in real time whether there are complicated underground conditions such as overflow, leakage, water outflow, gas invasion, etc. The pressure-controlled throttle valve can be used to adjust the wellhead back pressure to achieve the whole process of sealed and pressure-controlled casing lowering under abnormal pressure conditions in the wellbore.

[0039] Specifically, the present invention is implemented by the following steps:

[0040] First, a sealing device is designed above the wellhead device 10. The sealing device includes a pipe joint connected to the wellhead, an upper sealing structure 3 and a lower sealing structure 4 arranged in the pipe joint. The upper sealing structure 3 and the lower sealing structure 4 can achieve sealing on the cross section of the pipe joint. A pressure relief valve 7 and a pressure gauge 6 are arranged in the cavity between the upper sealing structure 3 and the lower sealing structure 4. A pressure control throttle valve 9 is arranged between the lower sealing structure 4 and the wellhead device 10 to adjust the wellhead back pressure. A pressure gauge 8 and a flow meter are arranged to measure the annular pressure of the wellbore 11 and the flow rate of the returned drilling fluid. The inlet and outlet flows are compared in real time during the mid-grouting cycle. The return amount of drilling fluid and the volume of the casing 1 are compared in real time during the casing 1 process. By comparing the whole process of casing 1, it is judged in real time whether there are complicated underground conditions such as overflow, leakage, water outflow, gas invasion, etc. in the well.

[0041] In the first step, during the lowering of the casing 1 with the centralizer 2, the upper sealing structure 3 of the sealing device is opened, and the lower sealing structure 4 is in a closed state. The annulus of the wellbore 11 is sealed by the lower sealing structure 4 to control the wellhead pressure and ensure pressure balance. Figure 1 shown.

[0042] Step 2: When lowering the casing 1, the casing 1 centralizer 2 is partially lowered safely into the cavity between the upper sealing structure 3 and the lower sealing structure 4. The positioner 5 is used to detect the position of the casing 1 centralizer 2 and alarm to ensure that the casing 1 centralizer 2 is in the correct position and stop lowering the casing 1. Figure 2 As shown, the locator 5 may be an infrared sensor.

[0043] Step 3: After the casing 1 centralizer 2 is in place, close the upper sealing structure 3. At this time, the cavity between the upper sealing structure 3 and the lower sealing structure 4 is sealed, the pressure relief valve 7 is also in a closed state, and the pressure gauge 6 value is zero. Figure 3 shown.

[0044] Step 4: Slowly open the lower sealing structure 4, the cavity is opened; the sleeve centralizer 2 is in the annulus of the wellbore 11, the wellbore 11 is connected to the cavity, the drilling fluid in the wellbore 11 enters the cavity, the pressure of the cavity and the annulus of the wellbore 11 reaches equilibrium, and the value of the pressure gauge 8 increases, such as Figure 4 shown.

[0045] Step 5: The lower sealing structure 4 has been opened, and the cavity between the upper and lower sealing structures 4 and the annular pressure of the wellbore 11 are balanced. The value of the pressure gauge 8 is equal to the annular pressure of the wellbore 11. Continue to lower the casing 1. The casing 1 with the centralizer 2 continues to be lowered into the wellbore 11. Figure 5 shown.

[0046] Step 6: After the sleeve centralizer 2 enters the annulus of the wellbore 11 through the lower sealing structure 4, after detecting that the centralizer 2 enters the annulus of the wellbore 11, the lower sealing structure 4 is closed to separate the annulus of the wellbore 11 and the cavity between the upper and lower sealing structures 4, and then the pressure relief valve 7 is opened to drain the drilling fluid in the cavity between the upper and lower sealing structures 4, and the value of the pressure gauge 6 is reduced until the pressure is zero, and the pressure is released as follows: Figure 6 shown.

[0047] Step 7. After the cavity pressure between the upper sealing structure 3 and the lower sealing structure 4 is released, the upper sealing structure 3 is opened, and the casing 1 operation is continued, and the second centralizer 2 component is prepared to be passed, and the operation is cycled to the first step.

[0048] The present invention adopts an upper and lower sealing structure, and safely lowers a casing centralizer component with a larger diameter under pressure to achieve annular sealing and casing lowering. During the casing lowering process, the wellbore annular pressure and the flow rate of the returned drilling fluid are monitored in real time through a pressure gauge and a flow meter, and the inlet and outlet flows are compared. The wellhead pressure control throttle valve is used to adjust the wellhead back pressure to complete the pressure-controlled casing lowering, and a circulation can be established as needed at any process node, so as to achieve the purpose of full-process pressure control in the drilling and completion cycle and dynamically balance the wellbore pressure.

[0049] In the present invention, the upper sealing structure and the lower sealing structure can be realized by using the existing technology. The focus of the present invention is to provide a method for sealing and controlling the pressure of the casing during the whole process.

[0050] Although the specific implementation of the present invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

[0051] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for casing lowering with full sealing and pressure control. It is characterized in that The steps include: Step 1: Design a sealing device above the wellhead device, the sealing device comprising a pipe joint connected to the wellhead, an upper sealing structure (3) and a lower sealing structure (4) arranged in the pipe joint; a pressure relief valve (7) and a pressure gauge (6) are arranged in the cavity between the upper sealing structure (3) and the lower sealing structure (4); a pressure control throttle valve (9) is arranged between the lower sealing structure (4) and the wellhead device (10) for adjusting the wellhead back pressure, and a pressure gauge (8) and a flow meter are arranged for measuring the annular pressure of the wellbore (11) and the flow rate of the returned drilling fluid; Step 2: When lowering the casing (1) with the centralizer (2), open the upper sealing structure (3), use the lower sealing structure (4) to close the annulus, and lower the casing (1) normally; Step 3: When the casing centralizer (2) is lowered into the cavity between the upper sealing structure (3) and the lower sealing structure (4), the positioner (5) is used to detect the position of the casing centralizer (2) and an alarm is sounded; after the casing centralizer (2) is in place, the upper sealing structure (3) is closed. At this time, the cavity between the upper sealing structure (3) and the lower sealing structure (4) is sealed, the pressure relief valve (7) is in a closed state, and the value of the pressure gauge (6) is zero; Step 4: After the upper sealing structure (3) completes the sealing of the cavity, the lower sealing structure (4) is opened and the casing lowering operation (1) is continued; the casing centralizer (2) is located in the annulus of the wellbore (11), the wellbore (11) is connected to the cavity, the drilling fluid in the wellbore (11) enters the cavity, and after the pressure of the cavity and the annulus of the wellbore (11) reaches equilibrium, the casing lowering operation (1) is continued; Step 5: After the casing centralizer (2) is lowered into the wellbore (11) as a whole, the lower sealing structure (4) is closed again to separate the wellbore (11) annulus and the cavity between the upper and lower sealing structures; Step 6: Use the pressure relief valve (7) to release the pressurized drilling fluid in the cavity between the upper and lower sealing structures; Step 7: After the pressure in the cavity is completely released, the upper sealing structure (3) is opened, and the operations of steps 1 to 6 are repeated to continue the operation of lowering the casing (1) and prepare to pass the next casing (1) through the centralizer (2).

2. A method for casing lowering with full-process sealing and pressure control according to claim 1, It is characterized in that At each step in the process of lowering the casing (1), a pressure gauge (8) and a flow meter are used to measure the wellbore (11) annular pressure and the flow rate of the returned drilling fluid respectively, and the inlet and outlet flows are compared in real time.

3. A method for casing lowering with full-process sealing and pressure control according to claim 1, It is characterized in that The locator (5) adopts an infrared sensor.

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