Reverse circulation well cementation tool and well cementation process thereof

Abstract

The invention relates to the technical field of well cementation devices, in particular to a reverse circulation well cementation tool and a well cementation technology thereof.The reverse circulation well cementation tool comprises a direct circulation well mouth device, a reverse circulation well mouth short section, an upper casing string, a lower casing string, a float collar, a float shoe and a communicating device; the outer side of the upper end of the upper casing string is provided with a reverse circulation well mouth short section capable of sealing an annulus between the casing and the well wall, and the reverse circulation well mouth short section is provided with a reverse circulation opening capable of being communicated with the annulus. The plugging and pressure bearing time before well cementation can be greatly shortened; the cement paste setting waiting sequence is changed, and the super-retarding phenomenon is effectively avoided; large-displacement construction is achieved, the displacement efficiency is improved, and the two-interface well cementation quality is improved; tool accessories such as a grading hoop and a rubber plug are not needed, the construction cost is saved, and complex accidents caused by the tool accessories are eliminated; during construction, pollution slurry is not returned out and does not need to be recycled, the drilling fluid cost is saved, and the problem of environmental pollution caused by conventional well cementation is completely eradicated.

Description

Technical Field

[0001] The invention relates to the technical field of cementing devices, in particular to a reverse circulation cementing tool and a cementing process thereof. Background Art

[0002] Cementing is one of the most important links in the process of oil and gas extraction. At present, the commonly used cementing method at home and abroad is to inject cement slurry from the casing, and then use the displacement fluid to displace it into the annulus to achieve the purpose of sealing. Reverse circulation cementing is to establish a reverse circulation channel, inject cement slurry from the annulus, and return the drilling fluid from the casing, so that the cement slurry stays directly in the annulus for sealing. When cementing low-pressure wells that are prone to leakage, small gap wells, and wells with long sealing sections, the conventional cementing process has a high equivalent circulating density (ECD) at the bottom of the hole and a high risk of leakage; when cementing wells with long sealing sections and large temperature differences, the cement slurry is super slow to set and the waiting time is long; the cement slurry returns to the surface well, which is easy to cause environmental pollution; there are well control risks and cementing accidents. Summary of the invention

[0003] The present invention provides a reverse circulation cementing tool and a cementing process thereof, which overcome the deficiencies of the above-mentioned prior art and can effectively solve the problems of high bottom hole equivalent circulation density, high leakage risk and long waiting time in the prior art cementing.

[0004] One of the technical solutions of the present invention is achieved through the following measures: a reverse circulation cementing tool, including a positive circulation wellhead device, a reverse circulation wellhead short section, an upper casing string, a lower casing string, a floating collar, a floating shoe, and a connecting device. The outer side of the lower end of the positive circulation wellhead device is connected to the inner side of the upper end of the upper casing string. A reverse circulation wellhead short section capable of closing the annulus between the casing and the well wall is installed on the outer side of the upper end of the upper casing string. The reverse circulation wellhead short section is provided with a reverse circulation port capable of connecting the annulus. The upper casing string, the floating collar, the lower casing string and the floating shoe are installed together in sequence from top to bottom. The connecting device can open the floating collar to connect the positive circulation wellhead device, the upper casing string, the connecting device and the lower casing string to form a circulation channel.

[0005] The following are further optimizations and / or improvements to the above technical solutions: The above-mentioned positive circulation wellhead device may include a positive circulation short joint and a pressure cap. A pressure cap is installed on the inner side of the upper end of the positive circulation short joint. The upper end of the pressure cap is located above the positive circulation short joint. A through hole connected to the positive circulation short joint is provided in the middle of the pressure cap. A ball valve is installed in the middle of the pressure cap. A positive circulation port is provided on the positive circulation short joint.

[0006] The positive circulation wellhead device may further include a sealing sleeve, a sealing sleeve capable of sealing the cable passing through the through hole is provided in the middle of the gland, and the ball valve can compress the sealing sleeve and is threadedly connected to the upper part of the gland.

[0007] The above-mentioned floating collar may include a floating collar pup joint and a flap valve, and the flap valves are installed in the floating collar pup joint at upper and lower intervals.

[0008] The above may also include a monitoring system. The connecting device includes a lifting pup section, a control pup section, a lifting cable, a lifting ring, a communication cable, and a monitor. A lifting ring is provided at the upper end of the lifting pup section, a communication cable is integrated in the lifting cable, a control pup section is installed at the lower end of the lifting pup section, a connecting channel is provided on the side walls of the lifting pup section and the control pup section, a monitor is installed on the inner side of the lower end of the control pup section, the communication cable passes through the channel and is connected to the monitor, the communication cable is connected to the monitoring system, a conical hole with a larger inner diameter at the top and a smaller inner diameter at the bottom is provided on the inner side of the upper part of the control pup section, and a floating ball is provided in the conical hole.

[0009] The second technical solution of the present invention is achieved by the following measures: A cementing process is carried out according to the following steps: Step 1: Casing operation. According to the cementing construction design, the float shoe, lower casing string, float collar, and upper casing string are lowered in sequence. After the casing string is lowered into the predetermined position, the positive circulation wellhead device and reverse circulation wellhead nipple are installed. Step 2: Circulation and well washing. Close the ball valve of the positive circulation wellhead device, open the plug valves at the positive circulation port and the reverse circulation port, pump drilling fluid into the positive circulation port to circulate and wash the well, and the impurities deposited at the bottom of the well and the drilling fluid flow out from the reverse circulation port; Step 3: Establish a reverse circulation channel. Remove the gland of the positive circulation wellhead device and open the ball valve. Disconnect the lifting sub from the lifting cable before construction. Pass the lifting cable through the gland before lowering the connecting device. Then connect the lifting cable to the lifting sub. When lowering the connecting device, the floating ball forms a seal with the conical surface of the tapered hole under the action of gravity. When the wellhead is pressurized, the control sub is blocked. The control sub moves downward under the action of pressure. When the control sub moves down to the floating hoop position, the two flap valves are pushed open respectively. After the flap valve is opened, the annulus between the positive circulation sub, the upper casing string, the connecting device, the lower casing string, the well wall and the suit is connected to form a reverse circulation channel connecting the inside and outside of the pipe. Step 4: Reverse circulation cementing. When mixing cement slurry, add the monitored substance to the front-end cement slurry, inject pre-fluid and cement slurry from the reverse circulation port respectively, and the front-end cement slurry is injected from the annulus and enters the lower casing string through the float shoe. When the front-end cement slurry with the monitored substance reaches the monitor, it is identified by the monitor and transmits the signal to the ground monitoring system through the communication cable. After receiving the signal, the construction is stopped; Step 5: Lift up the connecting device, control the lifting cable through the reel to lift the lifting section to the wellhead, close the plug valves at the positive circulation port and the reverse circulation port, and the construction is completed.

[0010] Magnetic powder can be added to the above-mentioned front-stage cement slurry, and the magnetic powder can be identified by the magnetic material identifier in the monitor.

[0011] The invention has a reasonable and compact structure and is easy to use. By establishing a circulation channel to connect the inside and outside of the casing, cementing cement slurry can be directly injected from the annulus, which can reduce a large amount of plugging and pressure-bearing time before cementing, help to speed up and improve drilling efficiency, change the cement slurry waiting sequence, and during cementing construction, the cement slurry reaches the high-temperature zone at the bottom of the well from the low-temperature zone at the wellhead, thereby reducing the requirements for the fluidity of the cement slurry, eliminating the need to add excessive retarders, and effectively avoiding the super-retarded setting phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Attached Figure 1 It is a schematic diagram of the front cross-sectional structure of the positive circulation wellhead device of the present invention.

[0013] Attached Figure 2 It is a schematic diagram of the front cross-sectional structure of the floating hoop of the present invention.

[0014] Attached Figure 3 It is a schematic diagram of the front cross-sectional structure of the communication device of the present invention.

[0015] Attached Figure 4 It is a schematic diagram of the main cross-sectional structure after the pipe string is lowered into the present invention.

[0016] Attached Figure 5 For attachment Figure 4 Schematic diagram of the main cross-sectional structure after the connecting device is inserted into the middle and lower parts.

[0017] The codes in the attached drawings are: 1 is a ball valve, 2 is a sealing sleeve, 3 is a gland, 4 is a positive circulation port, 5 is a positive circulation short section, 6 is a tongue valve, 7 is a lifting cable, 8 is a lifting ring, 9 is a control short section, 10 is a floating ball, 11 is a communication cable, 12 is a monitor, 13 is a floating collar short section, 14 is a reverse circulation wellhead short section, 15 is annulus, 16 is a well wall, 17 is an upper casing string, 18 is a floating shoe, 19 is a reel, 20 is a monitoring system, 21 is a lower casing string, 22 is a lifting short section, and 23 is an outer cone. DETAILED DESCRIPTION

[0018] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0019] In the present invention, for the convenience of description, the relative position relationship of each component is described according to the attached Figure 1 The positional relationships such as front, back, top, bottom, left, and right are described according to the layout directions of the drawings in the specification.

[0020] The present invention will be further described below in conjunction with embodiments and drawings: Embodiment 1: As attached Figure 1 , 2As shown in Figures 3, 4 and 5, the reverse circulation cementing tool comprises a positive circulation wellhead device, a reverse circulation wellhead short section 14, an upper casing string 17, a lower casing string 21, a floating collar, a floating shoe 18 and a connecting device. The outer side of the lower end of the positive circulation wellhead device is connected to the inner side of the upper end of the upper casing string 17. The outer side of the upper end of the upper casing string 17 is provided with a reverse circulation wellhead short section 14 capable of closing the annulus 15 between the casing and the well wall 16. The reverse circulation wellhead short section 14 is provided with a reverse circulation port capable of connecting the annulus 15. The upper casing string 17, the floating collar, the lower casing string 21 and the floating shoe 18 are sequentially installed together from top to bottom. The connecting device can open the floating collar to connect the positive circulation wellhead device, the upper casing string 17, the connecting device and the lower casing string 21 to form a circulation channel.

[0021] The floating collar is open in one direction. During the positive circulation well washing, the well washing drilling fluid enters the casing from the positive circulation wellhead device and flows out from the reverse circulation port. The drilling fluid in the well can also be reversely circulated to the pipe and the ground mud tank for reuse. During construction, no contaminated drilling fluid is returned, and there is no need to recover the drilling fluid, which greatly saves the drilling fluid cost and eliminates the environmental pollution problem caused by the contaminated slurry produced by conventional cementing. During cementing, the connecting device is lowered, the floating collar is opened, the casing is connected inside and outside, and cement slurry is injected from the reverse circulation port. The cement slurry directly enters the annulus 15 between the well wall 16 and the casing for cementing. Compared with conventional cementing, reverse circulation cementing can reduce the equivalent circulating density (ECD) at the bottom of the hole and reduce the risk of leakage. It usually takes 1-30 days to plug the leak and 1-2 days to bear the pressure. It can reduce a lot of plugging and pressure bearing time before cementing, which helps drilling. The drilling speed and efficiency are improved; the cement slurry waiting sequence is changed, and during cementing construction, the cement slurry reaches the high-temperature zone at the bottom of the well from the low-temperature zone at the wellhead, which reduces the requirements for the fluidity of the cement slurry, and there is no need to add excessive retarders, effectively avoiding the super-retardation phenomenon; it can break through the displacement limit of conventional cementing construction, increase the construction displacement, improve the displacement efficiency, and significantly improve the cementing quality of the second interface, which is beneficial to improving the integrity of the wellbore and promoting the management of the whole life cycle of the wellbore; there is no need for tool accessories such as grading collars and rubber plugs, which not only saves construction costs, but also eliminates the risk of complex accidents caused by tool accessories; all the drilling fluid in the well can be recycled to the pipe and the ground mud tank for reuse, and no contaminated drilling fluid is returned during construction, and there is no need to recover the drilling fluid, which saves a lot of drilling fluid costs and eliminates the environmental pollution caused by the contaminated slurry produced by conventional cementing.

[0022] The above reverse circulation cementing tools can be further optimized and / or improved according to actual needs: As attached Figure 1 , 4As shown in Figure 5, the positive circulation wellhead device includes a positive circulation pup joint 5 and a pressure cap 3. The pressure cap 3 is installed on the inner side of the upper end of the positive circulation pup joint 5. The upper end of the pressure cap 3 is located above the positive circulation pup joint 5. A through hole connected to the positive circulation pup joint 5 is provided in the middle of the pressure cap 3. A ball valve 1 is installed on the upper side of the pressure cap 3 corresponding to the position of the through hole. The ball valve 1 can open and close the through hole. The positive circulation pup joint 5 is provided with a positive circulation port 4.

[0023] The ball valve 1 and the gland 3 are set to seal the upper end of the positive circulation short joint 5, and the drilling fluid for well washing is injected through the positive circulation port 4. The positive circulation port 4 and the reverse circulation port are both provided with a plug valve to control the opening and closing of the positive circulation port 4 and the reverse circulation port. The positive circulation wellhead device is simple and does not require tool accessories such as grading hoops and rubber plugs, which not only saves construction costs, but also eliminates the risk of complex accidents caused by tool accessories.

[0024] As attached Figure 1 , 4 As shown in , 5 , the positive circulation wellhead device also includes a sealing sleeve 2. A sealing sleeve 2 is provided on the outer side of the middle part of the through hole. The sealing sleeve 2 can seal the lifting cable 7 passing through the through hole. The ball valve 1 can compress the sealing sleeve 2 and be threadedly connected with the inner side of the upper part of the pressure cover 3.

[0025] The lifting cable 7 is sealed by the sealing sleeve 2 to prevent the underground liquid from flowing out.

[0026] As attached Figure 2 , 4 As shown in FIG. 5 , the floating hoop comprises a floating hoop nipple 13 and a flap valve 6, and two flap valves 6 are installed at intervals in the floating hoop nipple 13. Two one-way flap valves 6 are provided to control whether the floating hoop channel is open.

[0027] As attached Figure 3 , 4 As shown in , 5, it also includes a monitoring system 20, the connecting device includes a lifting short section 22, a control short section 9, a lifting cable, a lifting ring 8, a communication cable 11, and a monitor 12. The upper end of the lifting short section 22 is provided with a lifting ring 8, the lifting cable is connected to the lifting ring 8, and the communication cable 11 is integrated in the lifting cable. The lower end of the lifting short section 22 is installed with a control short section 9, and a connecting channel is provided on the side walls of the lifting short section 22 and the control short section 9. The monitor 12 is installed on the inner side of the lower end of the control short section 9. One end of the communication cable 11 passes through the channel and is connected to the monitor 12, and the other end of the communication cable 11 is connected to the monitoring system 20. A conical hole with a larger inner diameter at the top and a smaller inner diameter at the bottom is provided on the inner side of the upper part of the control short section 9, and a floating ball 10 is provided in the conical hole. The outer side of the control short section 9 corresponding to the position of the conical hole is provided with an outer conical surface 23 with a larger outer diameter at the top and a smaller outer diameter at the bottom. The position of the outer conical surface 23 of the control short section 9 can be hung on the inner side of the flap valve 6 located above and can form a conical surface seal with the inner side of the flap valve 6.

[0028] During reverse circulation cementing, the lifting cable is lowered through the reel 19, and the lifting short section 22 and the control short section 9 are lowered to open the flap valve 6 at the lower part of the control short section 9. When the cement slurry for cementing flows from the annulus 15 and enters the lower casing string 21 along the float shoe 18, when the cement slurry reaches the monitor 12, the monitor 12 transmits the signal to the monitoring system 20 through the communication cable 11, and the injection of cement slurry for cementing is stopped.

[0029] Embodiment 2: As attached Figure 1 , 2 As shown in , 3, 4, and 5, the cementing process is carried out according to the following steps: Step 1: Casing operation: according to the cementing construction design, the float shoe 18, the lower casing string 21, the float collar, and the upper casing string 17 are sequentially lowered. After the casing string is lowered into the predetermined position, the forward circulation wellhead device and the reverse circulation wellhead short section 14 are installed; Step 2: Circulation and well washing. Close the ball valve 1 of the positive circulation wellhead device, open the plug valves at the positive circulation port 4 and the reverse circulation port, pump drilling fluid from the positive circulation port 4, and circulate and wash the well. The impurities deposited at the bottom of the well and the drilling fluid flow out from the reverse circulation port. Step 3: Establish a reverse circulation channel. Remove the gland 3 of the positive circulation wellhead device and open the ball valve 1. Disconnect the lifting sub 22 from the lifting cable 7 before construction. Pass the lifting cable 7 through the gland 3 before lowering into the connecting device. Then connect the lifting cable 7 to the lifting sub 22. When lowering into the connecting device, the floating ball 10 forms a seal with the conical surface of the tapered hole under the action of gravity. When the wellhead is pressurized, the control sub 9 is blocked. Under the action of pressure, the control sub 9 moves downward. When the control sub 9 moves downward to the floating hoop position, the two flap valves 6 are pushed open respectively. After the flap valve 6 is opened, the positive circulation sub 5, the upper casing string 17, the connecting device, the lower casing string 21, the well wall 16 and the annulus 15 between the casing are connected to form a reverse circulation channel connecting the inside and outside of the pipe. Step 4: Reverse circulation cementing. When mixing cement slurry, add the monitored substance to the front-stage cement slurry, inject the pre-fluid and cement slurry from the reverse circulation port respectively, and the front-stage cement slurry is injected from the annulus 15 and enters the lower casing string 21 through the float shoe 18. When the front-stage cement slurry with the monitored substance reaches the monitor 12, it is identified by the monitor 12, and the signal is transmitted to the monitoring system 20 on the ground through the communication cable 11. After receiving the signal, the construction is stopped; Step 5: Lift up the connecting device, control the lifting cable 7 by the winding drum 19 to lift the lifting short section 22 to the wellhead, close the plug valves at the positive circulation port 4 and the reverse circulation port, and the construction is completed.

[0030] Magnetic powder is added to the front-stage cement slurry, and the magnetic powder can be identified by the magnetic material identifier in the monitor 12 .

[0031] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A reverse circulation cementing tool, characterized in that It includes a positive circulation wellhead device, a reverse circulation wellhead short section, an upper casing string, a lower casing string, a floating collar, a floating shoe, and a connecting device. The outer side of the lower end of the positive circulation wellhead device is connected to the inner side of the upper end of the upper casing string. A reverse circulation wellhead short section capable of closing the annulus between the casing and the well wall is installed on the outer side of the upper end of the upper casing string. The reverse circulation wellhead short section is provided with a reverse circulation port capable of connecting the annulus. The upper casing string, the floating collar, the lower casing string and the floating shoe are installed together in sequence from top to bottom. The connecting device can open the floating collar to connect the positive circulation wellhead device, the upper casing string, the connecting device and the lower casing string to form a circulation channel.

2. The reverse circulation cementing tool according to claim 1, characterized in that The positive circulation wellhead device includes a positive circulation nipple and a pressure cap. A pressure cap is installed on the inner side of the upper end of the positive circulation nipple. The upper end of the pressure cap is located above the positive circulation nipple. A through hole connected to the positive circulation nipple is provided in the middle of the pressure cap. A ball valve is installed on the upper side of the pressure cap corresponding to the position of the through hole. The ball valve can open and close the through hole. A positive circulation port is provided on the positive circulation nipple.

3. The reverse circulation cementing tool according to claim 2, characterized in that The positive circulation wellhead device also includes a sealing sleeve, which is provided on the outer side of the middle part of the through hole. The sealing sleeve can seal the lifting cable passing through the through hole. The ball valve can compress the sealing sleeve and is threadedly connected with the inner side of the upper part of the gland.

4. The reverse circulation cementing tool according to claim 1, 2 or 3, characterized in that The floating hoop comprises a floating hoop nipple and a tongue valve. Two tongue valves are installed in the floating hoop nipple at intervals in the upper and lower parts.

5. The reverse circulation cementing tool according to claim 4, characterized in that It also includes a monitoring system, and the connecting device includes a lifting pup joint, a control pup joint, a lifting cable, a lifting ring, a communication cable, and a monitor. A lifting ring is provided at the upper end of the lifting pup joint, the lifting cable is connected to the lifting ring, and the communication cable is integrated in the lifting cable. A control pup joint is installed at the lower end of the lifting pup joint, and a connecting channel is provided on the side walls of the lifting pup joint and the control pup joint. A monitor is installed on the inner side of the lower end of the control pup joint, one end of the communication cable passes through the channel and is connected to the monitor, and the other end of the communication cable is connected to the monitoring system. A conical hole with a larger inner diameter at the top and a smaller inner diameter at the bottom is provided on the inner side of the upper part of the control pup joint, and a floating ball is provided in the conical hole. An outer conical surface with a larger outer diameter at the top and a smaller outer diameter at the bottom is provided on the outer side of the control pup joint corresponding to the position of the conical hole. The position of the outer conical surface of the control pup joint can be hung on the inner side of the tongue valve located above and can form a conical surface seal with the inner side of the tongue valve.

6. A cementing process using the reverse circulation cementing tool as claimed in claim 5, characterized in that Follow the steps below: Step 1: Casing operation. According to the cementing construction design, the float shoe, lower casing string, float collar, and upper casing string are lowered in sequence. After the casing string is lowered into the predetermined position, the positive circulation wellhead device and reverse circulation wellhead nipple are installed. Step 2: Circulation and well washing. Close the ball valve of the positive circulation wellhead device, open the plug valves at the positive circulation port and the reverse circulation port, pump drilling fluid into the positive circulation port to circulate and wash the well, and the impurities deposited at the bottom of the well and the drilling fluid flow out from the reverse circulation port; Step 3: Establish a reverse circulation channel. Remove the gland of the positive circulation wellhead device and open the ball valve. Disconnect the lifting sub from the lifting cable before construction. Pass the lifting cable through the gland before lowering the connecting device. Then connect the lifting cable to the lifting sub. When lowering the connecting device, the floating ball forms a seal with the conical surface of the tapered hole under the action of gravity. When the wellhead is pressurized, the control sub is blocked. The control sub moves downward under the action of pressure. When the control sub moves down to the floating hoop position, the two flap valves are pushed open respectively. After the flap valve is opened, the annulus between the positive circulation sub, the upper casing string, the connecting device, the lower casing string, the well wall and the suit is connected to form a reverse circulation channel connecting the inside and outside of the pipe. Step 4: Reverse circulation cementing. When mixing cement slurry, add the monitored substance to the front-end cement slurry, inject pre-fluid and cement slurry from the reverse circulation port respectively, and the front-end cement slurry is injected from the annulus and enters the lower casing string through the float shoe. When the front-end cement slurry with the monitored substance reaches the monitor, it is identified by the monitor and transmits the signal to the ground monitoring system through the communication cable. After receiving the signal, the construction is stopped; Step 5: Lift up the connecting device, control the lifting cable through the reel to lift the lifting section to the wellhead, close the plug valves at the positive circulation port and the reverse circulation port, and the construction is completed.

7. The cementing process according to claim 6, characterized in that Magnetic powder is added to the cement slurry in the front stage, and the magnetic powder can be identified by the magnetic material identifier in the monitor.

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