CN115749672A - Multi-stage combined plugging process outside casing - Google Patents
Multi-stage combined plugging process outside casing Download PDFInfo
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Abstract
The invention belongs to the technical field of casing plugging of oil fields, and particularly relates to an external casing multi-stage combined plugging process. A multi-stage combined plugging process outside a casing comprises the following steps: collecting data of a well section to be plugged; determining the total dosage of water injection slurry of the multi-stage pump and the lowest extrusion sealing pump pressure; a plugging operation tubular column is put in; performing multistage cement slurry plugging operation; performing multi-stage high-strength plugging agent plugging operation; and (5) replacing with clear water, closing the well and waiting for coagulation to finish the plugging operation. According to the invention, through multi-stage cement extrusion sealing, by utilizing a pressure-bearing superposition effect, the outer stratum of the leakage point pipe of the casing pipe can be fully filled, a larger fan-shaped confining pressure range is formed, and meanwhile, a high-strength plugging radius is formed in a region close to a well bore of the leakage point through a high-strength plugging agent, so that compared with the simple multi-stage cement extrusion sealing, the pressure-bearing capacity of the well bore is improved, and finally the pressure test of the well bore can reach more than 55 MPa.
Description
Technical Field
The invention belongs to the technical field of casing plugging of oil fields, and particularly relates to an external casing multi-stage combined plugging process.
Background
With the increase of the number of damaged casing wells of various large oil fields in China year by year, the problem of casing damage becomes a difficult problem in the petroleum industry in China and restricts the development of oil fields. The casing leakage accounts for more than 50% of casing damage, is the main expression form of casing damage, particularly after some high-pressure gas well oil layer casings leak, the phenomenon of annulus pressure occurs, which brings a severe test to on-site safety production, and in severe cases, the oil and gas wells cannot be normally produced or scrapped, and even threaten the safety of lives and properties.
At present, the casing leakage repair technology is mainly divided into the following three types: 1. the technique for repairing the casing pipe of the expansion pipe is a technique which is popular in recent years and is used for effectively repairing the leakage section of the casing pipe, and the two techniques are a solid expansion pipe and a corrugated expansion pipe which are commonly adopted and have long respective lengths. The main disadvantage is that the drift diameter of the casing becomes smaller, which restricts the subsequent operation measures. 2. The principle of the technology is that a bidirectional hanger is used for hanging a pipe string at the top of a damaged section of a casing pipe, and then packers are combined and used respectively at the upper part and the lower part of a leakage section of the casing pipe, so that the casing pipe obtains the pressure bearing capacity, and the defect of the technology still causes the drift diameter of the casing pipe to be reduced. 3. The chemical plugging mainly comprises inorganic cementing materials, and has the most important advantages that the inner drift diameter of the casing can be recovered through drilling and plugging and other modes after plugging, and the chemical plugging technical difficulty of casing damage and leakage is as follows: firstly, the leakage point has large corresponding stratum leakage loss and poor stratum homogeneity, a plugging area after single extrusion cannot form a complete fan-shaped state outside a sleeve, and the pressure bearing is low; secondly, due to the heterogeneity of the stratum, secondary extrusion sealing can generate new leakage cracks in different directions of the stratum of the leakage point, and the bearing capacity after sealing cannot be effectively improved. The existing chemical plugging agent is difficult to enter or reside in a leakage section, has low cementing strength with a sleeve and a stratum, can not meet high-pressure requirements under pressure bearing and the like, has low plugging success rate and poor adaptability and safety and reliability.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a multi-stage combined plugging process outside a casing, which is used for plugging a casing leakage well section by combining cement multi-stage extrusion sealing and high-strength plugging agent multi-stage extrusion sealing, a good fan-shaped plugging area is formed outside a leakage point casing, the plugging effect is good, the strength is higher, the integral bearing capacity of the casing damage leakage well casing can be improved, and the pressure test of a shaft can reach more than 55 Mpa.
The technical scheme of the invention is as follows: a multi-stage combined plugging process outside a casing comprises the following steps:
s1: collecting data of a well section to be plugged, wherein the data comprise the position of the well section to be plugged, the thickness of a leakage point stratum, porosity, water absorption index and plugging pretreatment radius;
s2: determining the total dosage of water injection slurry of the multi-stage pump and the lowest extrusion sealing pump pressure;
s3: a plugging operation tubular column is put in;
s4: performing multistage cement slurry plugging operation through the operation pipe column which is lowered in the step S3;
s5: after multi-stage cement slurry plugging operation, if the cement plugging pressure reaches the designed lowest extrusion sealing pump pressure, a cement plug and a waiting set are left in the shaft, if the cement plugging pressure is lower than the designed lowest extrusion sealing pump pressure, all cement slurry is squeezed into the stratum by using clean water, and after the well is closed for a period of time, the multi-stage cement slurry plugging operation in S4 is repeated;
s6: treating the shaft after the coagulation, and performing multistage high-strength plugging agent plugging operation by using a high-strength plugging agent;
s7: after the multi-stage high-strength plugging agent is used for plugging, clear water replacement and shut-in and coagulation waiting are carried out, and the multi-stage combined plugging operation outside the casing of the well section to be plugged is completed.
And in the S2, the total dosage Q of the cement slurry injected into the multistage pump is determined, and the calculation formula is as follows:
Q=πR 2 HP （1）
in the formula, H is the thickness of the leak source stratum, m; p is porosity, dimensionless; r is the plugging pretreatment radius m.
And determining the lowest extrusion sealing pump pressure in the S2, wherein the numerical value of the lowest extrusion sealing pump pressure is not lower than the pump injection pressure in the process of testing the water absorption index before sealing and is not higher than the fracture pressure of the leakage stratum.
The density range of the multistage pump cement slurry in the S4 is 1.8 to 1.9g/cm 3 The initial setting time of the multistage pump water injection slurry is longer than the total construction time.
And in the S4, the cement used by the multistage pump cement slurry is G-grade cement, and the compression resistance of the multistage pump cement slurry is greater than 24MPa under the condition of indoor test and 48-hour curing at 27 ℃.
And in the S4, the multistage pump cement injection slurry is divided into first stage pump cement injection slurry, second stage pump cement injection slurry and third stage pump cement injection slurry, the pump injection amount of the first stage pump cement injection slurry is 60-70% of the total amount of the multistage pump cement injection slurry, the pump injection amount of the second stage pump cement injection slurry is 20-30% of the total amount of the multistage pump cement injection slurry, and the balance is the pump injection amount of the third stage pump cement injection slurry.
And the pump stopping time is 15 to 30min after the first-stage pump water injection slurry pump finishes the injection, 30 to 60min after the second-stage pump water injection slurry pump finishes the injection, and the pump is stopped after the third-stage pump water injection slurry pump finishes the injection, and the well shut-in and the waiting time are 72 hours.
And in the S5, when the cement plugging pressure is lower than the designed lowest extrusion pump pressure, the well closing time is more than or equal to 24 hours, then the multistage cement slurry plugging operation in the S4 is repeated, and when the cement plugging pressure reaches the designed lowest extrusion pump pressure, the length of a cement plug left in the shaft is 30-50 meters.
The S6 medium-high strength plugging agent is a pressure difference plugging agent, the indoor test compressive strength of the high strength plugging agent is not less than 55Mpa, the plugging stage number of the pressure difference plugging agent plugging operation is N stage, N is not less than 2, and the extrusion amount Q of the single-stage plugging high strength plugging agent is within the range of 0.01 m 3 ≤Q≤0.2m 3 。
The S6 medium-high strength plugging agent is a resin adhesive plugging agent, the indoor test compressive strength of the high strength plugging agent is not less than 55Mpa, the plugging stage number of the plugging operation of the resin adhesive plugging agent is n, n is not less than 5 and not less than 1, and the range of the extrusion amount q of the single-stage plugging high strength plugging agent is 0.02 m 3 ≤q≤0.25m 3 。
The invention has the technical effects that:
1. the invention controls the infinite absorption of stratum to cement slurry through multi-stage cement slurry plugging, controls the cement slurry to gradually solidify and accumulate near the radius of 3m, reduces plugging materials and shortens the construction period.
2. The invention can fully fill the outer stratum of the leakage point pipe of the casing by multi-stage cement paste plugging and utilizing the pressure-bearing superposition effect, and form the fan-shaped or even cylindrical confining pressure range with the radius of more than 3m, and the pressure-bearing reaches 35MPa.
3. According to the invention, the high-strength plugging agent forms a high-strength plugging radius in the area close to the leakage point, compared with single multi-stage cement extrusion, the pressure bearing capacity of the shaft is improved, and finally the pressure test of the shaft can reach more than 55 MPa.
4. The multistage combined plugging process disclosed by the invention is simple in process and convenient to implement, the one-time plugging success rate can be greatly improved, and the shaft plugging period is shortened by over 50%.
The following will be further described with reference to the accompanying drawings.
Drawings
FIG. 1 is a schematic view of the sealing effect of conventional cement paste;
fig. 2 is a schematic diagram of the plugging effect of the multi-stage combined plugging process outside the casing according to the embodiment of the invention.
Detailed Description
Example 1
A multi-stage combined plugging process outside a casing comprises the following steps:
s1: collecting data of a well section to be plugged, wherein the data comprise the position of the well section to be plugged, the thickness of a leak source stratum, porosity, a water absorption index and a plugging pretreatment radius;
s2: determining the total dosage of water injection slurry of the multi-stage pump and the lowest extrusion sealing pump pressure;
s3: a plugging operation tubular column is put in;
s4: performing multistage cement slurry plugging operation through the operation pipe column which is lowered in the step S3;
s5: after multi-stage cement slurry plugging operation, if the cement plugging pressure reaches the designed lowest squeezing and sealing pump pressure, a cement plug is left in the shaft and is kept for waiting for setting, if the cement plugging pressure is lower than the designed lowest squeezing and sealing pump pressure, all cement slurry is squeezed into the stratum by using clear water, and after the well is closed for a period of time, the multi-stage cement slurry plugging operation in S4 is repeated;
s6: treating the shaft after the coagulation, and performing multistage high-strength plugging agent plugging operation by using a high-strength plugging agent;
s7: after the multi-stage high-strength plugging agent is used for plugging, clear water replacement and shut-in and coagulation waiting are carried out, and the multi-stage combined plugging operation outside the casing of the well section to be plugged is completed.
And in the S2, the total dosage Q of the cement slurry injected into the multistage pump is determined, and the calculation formula is as follows:
Q=πR 2 HP （1）
in the formula, H is the thickness of the leak source stratum, m; p is porosity, dimensionless; r is the plugging pretreatment radius m.
And determining the lowest extrusion sealing pump pressure in the S2, wherein the numerical value of the lowest extrusion sealing pump pressure is not lower than the pump injection pressure in the process of testing the water absorption index before sealing and is not higher than the fracture pressure of the leakage stratum. Minimum squeeze seal pump pressure: the pressure value is designed by adding a coefficient to the pump injection pressure in the process of testing the water absorption index before plugging the lost stratum, and the value of the pressure value is close to the fracture pressure of the lost stratum. Namely: and before plugging, the pump injection pressure in the process of testing the water absorption index is less than or equal to the lowest extrusion sealing pump pressure and less than or equal to the fracture pressure of the lost circulation formation.
As shown in fig. 1, after a conventional cement slurry squeezing and plugging operation is performed on a class B leak point (a leak stratum outside a pipe) in the figure, a plugging area formed by the stratum outside the leak point pipe is heterogeneous, and a single plugging may form plugging areas (such as areas 1, 2 and 3 in the figure) in different directions, so that the pressure bearing is low. As shown in figure 2, the invention can fully fill the outer stratum of the bushing leak point pipe by multistage cement extrusion sealing and utilizing the pressure-bearing superposition effect, and form a larger fan-shaped confining pressure range, such as a first plugging area in figure 2, and then use a high-strength plugging agent for plugging to form a high-strength plugging area close to a well zone, such as a second plugging area in figure 2, compared with the single multistage cement extrusion sealing, the pressure-bearing capacity of a shaft is improved, and the final pressure test of the shaft can reach more than 55 Mpa.
The density range of the multistage pump cement slurry in the S3 is 1.8 to 1.9g/cm 3 The initial setting time of the multistage pump for injecting the cement slurry is longer than the total construction time.
In the actual use process, the initial setting time of the multistage pump for injecting the cement slurry is longer than the total construction time, so that the cement slurry is prevented from being solidified in advance, and a drilling tool is prevented from being solidified in a shaft.
And in the S4, the multi-stage pump cement paste is divided into first-stage pump cement paste, second-stage pump cement paste and third-stage pump cement paste, the pump injection amount of the first-stage pump cement paste is 60-70% of the total amount of the multi-stage pump cement paste, the pump injection amount of the second-stage pump cement paste is 20-30% of the total amount of the multi-stage pump cement paste, and the balance is the pump injection amount of the third-stage pump cement paste.
And the pump stopping time is 15 to 30min after the first-stage pump water injection slurry pump finishes the injection, 30 to 60min after the second-stage pump water injection slurry pump finishes the injection, and the pump is stopped after the third-stage pump water injection slurry pump finishes the injection, and the well shut-in and the waiting time are 72 hours.
And in the S5, when the cement plugging pressure is lower than the designed lowest extrusion pump pressure, the well closing time is more than or equal to 24 hours, then the multistage cement slurry plugging operation in the S4 is repeated, and when the cement plugging pressure reaches the designed lowest extrusion pump pressure, the length of a cement plug left in the shaft is 30-50 meters.
In the actual use process, the multistage pump water injection mud is pumped into the well in different time intervals, and the stratum outside the leakage point pipe of the casing pipe can be fully filled by utilizing the pressure-bearing superposition effect, and a larger fan-shaped confining pressure range is formed.
And in the S5, when the cement plugging pressure is lower than the designed lowest squeezing pump pressure, the well closing time is more than or equal to 24 hours, then the multistage cement slurry plugging operation in the S4 is repeated, and when the cement plugging pressure reaches the designed lowest squeezing pump pressure, the length of a cement plug left in the shaft is 30 to 50 meters.
In the actual use process, the length of a cement plug left in the shaft is 30-50, so that the shaft has enough pressure bearing capacity in the blocking operation process of the multi-stage high-strength blocking agent.
The S6 medium-high strength plugging agent is a pressure difference plugging agent, the indoor test compressive strength of the high strength plugging agent is not less than 55Mpa, the plugging stage number of the pressure difference plugging agent plugging operation is N stage, N is not less than 2, and the extrusion amount Q of the single-stage plugging high strength plugging agent is within the range of 0.01 m 3 ≤Q≤0.2m 3 。
In the actual use process, the pressure difference plugging agent is mainly liquid consisting of latex, an activating agent, a terminating agent and a stabilizing agent, the pressure difference plugging agent is the prior art and is mainly used for pressure-bearing plugging while drilling in the drilling process, different densities are adopted according to different leak rates, the pressure difference plugging agent is used for external casing plugging, when the pressure difference plugging agent is used, the pressure difference plugging agent is injected into a leakage space and is pressurized to activate a polymerization process under the condition of pressure difference of a leakage part, the pressure difference plugging agent generates chemical reaction and is solidified at the leakage part to repair the leakage point, the plugging stage number of the pressure difference plugging agent plugging operation is N stage which is not less than 2, the extrusion amount Q of the single-stage plugging high-strength plugging agent is within the range of 0.01 m 3 ≤Q≤0.2m 3 And the multi-stage and small-dosage interval injection ensures that the pressure difference plugging agent is solidified and then fills the space after cement extrusion, thereby further improving the pressure bearing capacity of the shaft.
Example 2
On the basis of embodiment 1, in this embodiment, preferably, the high-strength plugging agent in S6 is a resin adhesive plugging agent, and the indoor test resistance of the high-strength plugging agent is preferably testedThe compressive strength is more than or equal to 55Mpa, the plugging stage number of the plugging operation of the resin adhesive plugging agent is n, n is more than or equal to 5 and more than or equal to 1, and the extrusion amount q of the single-stage plugging high-strength plugging agent is within the range of 0.02 m 3 ≤q≤0.25m 3 。
In the actual use process, the resin adhesive plugging agent adopts a polymer system, and when the resin adhesive plugging agent permeates into formation pores or microcracks through the synergistic effect of the multi-component polymer and the control agent, the resin adhesive plugging agent is directly cured through temperature activation, so that effective plugging is implemented. The plugging stage number of the plugging operation of the resin adhesive plugging agent is n, n is more than or equal to 5 and is more than or equal to 1, and the extrusion amount q of the single-stage plugging high-strength plugging agent is within the range of 0.02 m 3 ≤q≤0.25m 3 And the resin adhesive plugging agent is injected at intervals in multiple stages and small dosage, so that the space formed after the cement is extruded and sealed after the resin adhesive plugging agent is cured is ensured, and the pressure bearing capacity of the shaft is further improved.
Example 3
The multi-stage combined plugging process outside the casing pipe is adopted to perform plugging operation on a horizontal well of a certain oil well in a certain oil field. In the 15 th section fracturing process of the hydraulic pumping bridge plug of the horizontal well, the fracture pressure is 48.2MPa, the working pressure is suddenly reduced to 0 from 41.5MPa, the construction is stopped, and the pump stopping pressure is 3.2MPa.
S1: collecting data of a well section to be plugged, wherein the data comprise the position of the well section to be plugged, the thickness of a leak source stratum, porosity, a water absorption index and a plugging pretreatment radius;
under the observation of a down-hole television, the casing body is damaged, the diameter is about 70mm, the depth of a leaking point is 547.6m, the thickness H of a leaking point stratum is 5m, the porosity P is 13%, and the plugging radius R is designed to be 3m;
s2: determining the total dosage of water injection slurry of the multi-stage pump and the lowest extrusion sealing pump pressure;
determining the total dosage Q of the cement slurry injected into the multistage pump, wherein the calculation formula is as follows:
Q=πR 2 HP （1）
in the formula, H is the thickness of the leak source stratum, m; p is porosity, dimensionless; r is the plugging pretreatment radius, m;
the total dosage of the multistage pump water injection mud is calculated to be 18.37m 3 (ii) a According to the pump injection pressure and leakage ground in the process of testing water absorption index before pluggingThe burst pressure of the layer, the lowest extrusion pressure, was determined to be 15Mpa;
s3: a plugging operation tubular column is put in;
s4: performing multistage cement slurry plugging operation through the operation pipe column which is lowered in the step S3;
the multistage pump water injection slurry squeezing and sealing scheme is as follows: adopting G-grade cement with the density of 1.86G/cm 3 Cement slurry 20m 3 Squeezing in three stages; the pump injection amount of the first-stage pump water injection mud is 60 to 70 percent of the total amount of the multistage pump water injection mud, the pump injection amount of the second-stage pump water injection mud is 20 to 30 percent of the total amount of the multistage pump water injection mud, and the balance is the pump injection amount of the third-stage pump water injection mud;
actual plugging process parameters: pump injection amount of first-stage pump injection mud is 12.5m 3 The discharge capacity is 430L/min, the pump pressure is 3.3Mpa, and the well is closed and thickened for 30min; pump injection of second stage pump injection mud 4.3m 3 The discharge capacity is 200L/min, the pump pressure is 9.8Mpa, and the well is closed and thickened for 45min; pump injection amount of third stage pump water injection slurry is 2.1m 3 The discharge capacity is 200L/min, the pump pressure is 17.7Mpa, and the cement plugging pressure reaches the designed lowest extrusion sealing pump pressure;
s5: after the plugging operation of the multistage cement paste, closing the well and waiting for setting for 72 hours, and leaving a cement plug of 30m;
s6: after waiting for the coagulation, treating the shaft, and performing multi-stage high-strength plugging agent plugging operation by using a high-strength plugging agent;
the high-strength plugging agent adopts a pressure difference plugging agent, and the extrusion sealing scheme is that after cement extrusion sealing, the pressure test of a leakage point is 25 MPa, and the pressure test is reduced to 15MPa within 10 min; the density adopted in this time is 1.07g/cm 3 Pressure difference plugging agent 2.5m 3 Adopting multi-stage extrusion, wherein the final extrusion pressure is required to reach more than 50MPa, and the actual plugging process parameters are shown in table 1;
TABLE 1 multistage Pump injection pressure differential plugging agent plugging Process
S7: after the plugging operation of the multi-level high-strength plugging agent, clear water replacement and shut-in and coagulation waiting are carried out, the multi-level combined plugging operation outside the casing of the well section to be plugged is completed, the plugging effect is good, finally, the pressure test of a shaft is 51MPa, the pressure drop is qualified, and the expectation is reached.
Example 4
The multi-stage combined plugging process outside the casing pipe is adopted to perform plugging operation on a horizontal well of a certain oil well in a certain oil field. The horizontal well is subjected to pressure test of a shaft after well opening and well flushing, the pressure of a pump is not increased when the pressure of the pump is increased to 36MPa, the discharge capacity is 300L/min, and the pressure is reduced to 15MPa after the pump is stopped for 1 min.
S1: collecting data of a well section to be plugged, wherein the data comprise the position of the well section to be plugged, the thickness of a leakage point stratum, porosity, water absorption index and plugging pretreatment radius;
the position of a leakage point found by using a TDZ packer is 628-630m (the position of a casing collar is 628.39 m), and the casing wall is intact and 629.0m collar gap is abnormal by the observation of a downhole television. The depth of the leak point well is 629.0m, the thickness H of the leak point stratum is 3.5m, the porosity P is 11.5%, the plugging radius R is designed to be 3m,
s2: determining the total dosage of water injection slurry of the multi-stage pump and the lowest extrusion sealing pump pressure;
determining the total dosage Q of the cement slurry injected into the multistage pump, wherein the calculation formula is as follows:
Q=πR 2 HP （1）
in the formula, H is the thickness of the leak source stratum, m; p is porosity, dimensionless; r is the plugging pretreatment radius, m;
the total dosage of the multistage pump water injection slurry is calculated to be 11.3m 3 (ii) a According to the pump injection pressure and the fracture pressure of a leakage stratum in the process of testing the water absorption index before plugging, the lowest extrusion pressure is determined to be 20Mpa;
s3: putting in a plug to make a pipe column;
s4: performing multistage cement slurry plugging operation through the operation pipe column which is lowered in the step S3;
the multistage pump water injection slurry squeezing and sealing scheme is as follows: adopting G-grade cement with the density of 1.85G/cm 3 12m cement slurry 3 . Extruding according to three stages; the pump injection amount of the first-stage pump water injection slurry is 60 to 70 percent of the total amount of the multistage pump water injection slurry, the pump injection amount of the second-stage pump water injection slurry is 20 to 30 percent of the total amount of the multistage pump water injection slurry, and the balance is the pump injection amount of the third-stage pump water injection slurry;
actual plugging process parameters: pump injection amount of first-stage pump water injection slurry 7.2m 3 The discharge capacity is 350L/min, the pump pressure is 23.7Mpa, and the well closing is thickened for 45min; pump injection of second stage pump injection mud 3.3m 3 The discharge capacity is 200L/min, the pump pressure is 25.0Mpa, and the well is closed and thickened for 30min; pump injection amount of third stage pump water injection slurry is 0.6m 3 The discharge capacity is 100L/min, the pump pressure is 25.0Mpa, and the cement plugging pressure reaches the designed lowest extrusion sealing pump pressure;
s5: after the plugging operation of the multistage cement paste, closing the well and waiting for setting for 72 hours, and leaving a cement plug of 30m;
s6: treating the shaft after the coagulation, and performing multistage high-strength plugging agent plugging operation by using a high-strength plugging agent;
the high-strength plugging agent adopts a resin adhesive plugging agent, and the extrusion sealing scheme is that after the cement is extruded and sealed, the pressure test of a leakage point is 20.5 MPa, and the pressure test of 30min is reduced to 17.5MPa; the density adopted in this time is 1.1g/cm 3 0.5m of resin adhesive plugging agent 3 And adopting multi-stage extrusion, wherein the extrusion amount is required to be more than 300L, and the plug is 5-15m.
Actual plugging process parameters: the pump injection amount of the first-stage pump injection resin adhesive plugging agent is 0.216m 3 The discharge capacity is 100L/min, the pump pressure is 25.0Mpa, and the well is closed and thickened for 45min; the pump injection amount of the second-stage pump injection resin adhesive plugging agent is 0.083m 3 The discharge capacity is 100L/min, the pump pressure is 11.0Mpa, and the well is closed and thickened for 90min; the pump injection amount of the third-stage pump injection resin adhesive plugging agent is 0.045m 3 The discharge capacity is 100L/min, the pump pressure is 10.0Mpa, the accumulated extrusion amount of the resin adhesive plugging agent reaches the design requirement, and the pump injection process is shown in a table 2.
TABLE 2 multistage resin adhesive plugging agent plugging process
S7: after the plugging operation of the multi-stage high-strength plugging agent, clear water is replaced, the well is closed for coagulation, the multi-stage combined plugging operation outside the casing of the well section to be plugged is completed, the plugging effect is good, the final pressure test of the shaft is 52.5MPa, and the pressure drop is qualified, so that the expectation is reached.
While the invention has been described with reference to specific preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
Claims (10)
1. A multi-stage combined plugging process outside a casing is characterized in that: the method comprises the following steps:
s1: collecting data of a well section to be plugged, wherein the data comprise the position of the well section to be plugged, the thickness of a leak source stratum, porosity, a water absorption index and a plugging pretreatment radius;
s2: determining the total dosage of water injection slurry of the multi-stage pump and the lowest extrusion sealing pump pressure;
s3: a plugging operation tubular column is put in;
s4: performing multistage cement slurry plugging operation through the operation pipe column which is lowered in the step S3;
s5: after multi-stage cement slurry plugging operation, if the cement plugging pressure reaches the designed lowest squeezing and sealing pump pressure, a cement plug is left in the shaft and is kept for waiting for setting, if the cement plugging pressure is lower than the designed lowest squeezing and sealing pump pressure, all cement slurry is squeezed into the stratum by using clear water, and after the well is closed for a period of time, the multi-stage cement slurry plugging operation in S4 is repeated;
s6: after waiting for the coagulation, treating the shaft, and performing multi-stage high-strength plugging agent plugging operation by using a high-strength plugging agent;
s7: after the multi-stage high-strength plugging agent is used for plugging, clear water replacement and shut-in and coagulation waiting are carried out, and the multi-stage combined plugging operation outside the casing of the well section to be plugged is completed.
2. The multi-stage combined plugging process outside the casing according to claim 1, wherein: and in the S2, the total dosage Q of the cement slurry injected into the multistage pump is determined, and the calculation formula is as follows:
Q=πR 2 HP （1）
in the formula, H is the thickness of the leak source stratum, m; p is porosity, dimensionless; r is the plugging pretreatment radius, m.
3. The multi-stage combined plugging process outside the casing according to claim 1, wherein: and determining the lowest extrusion sealing pump pressure in the S2, wherein the numerical value of the lowest extrusion sealing pump pressure is not lower than the pump injection pressure in the process of testing the water absorption index before sealing and is not higher than the fracture pressure of the leakage stratum.
4. The multi-stage combined plugging process outside the casing according to claim 1, wherein: the density range of the multistage pump cement slurry in the S4 is 1.8 to 1.9g/cm 3 The initial setting time of the multistage pump for injecting the cement slurry is longer than the total construction time.
5. The multi-stage combined plugging process outside the casing according to claim 1, wherein: and in the S4, the cement used by the multistage pump cement slurry is G-grade cement, and the compression resistance of the multistage pump cement slurry is greater than 24MPa under the condition of indoor test and 48-hour curing at 27 ℃.
6. The multi-stage combined plugging process outside the casing according to claim 1, wherein: and in the S4, the multi-stage pump cement paste is divided into first-stage pump cement paste, second-stage pump cement paste and third-stage pump cement paste, the pump injection amount of the first-stage pump cement paste is 60-70% of the total amount of the multi-stage pump cement paste, the pump injection amount of the second-stage pump cement paste is 20-30% of the total amount of the multi-stage pump cement paste, and the balance is the pump injection amount of the third-stage pump cement paste.
7. The multi-stage combined plugging process outside the casing according to claim 6, wherein: and stopping the pump after the first-stage pump water injection slurry pump finishes injecting, wherein the pump stopping time is 15-30min, the pump stopping time is 30-60min after the second-stage pump water injection slurry pump finishes injecting, the pump is stopped after the third-stage pump water injection slurry pump finishes injecting, and the well is closed for waiting for setting for 72 hours.
8. The multi-stage combined plugging process outside the casing according to claim 1, wherein: and in the S5, when the cement plugging pressure is lower than the designed lowest extrusion pump pressure, the well closing time is more than or equal to 24 hours, then the multistage cement slurry plugging operation in the S4 is repeated, and when the cement plugging pressure reaches the designed lowest extrusion pump pressure, the length of a cement plug left in the shaft is 30-50 meters.
9. The multi-stage combined plugging process outside the casing according to claim 1, wherein: the S6 high-strength plugging agent is a pressure difference plugging agent, the indoor test compressive strength of the high-strength plugging agent is not less than 55Mpa, the plugging stage number of the plugging operation of the pressure difference plugging agent is N, N is not less than 2, and the extrusion amount Q of the single-stage plugging high-strength plugging agent is within the range of 0.01 m 3 ≤Q≤0.2m 3 。
10. The multi-stage combined plugging process outside the casing according to claim 1, wherein: the S6 medium-high strength plugging agent is a resin adhesive plugging agent, the indoor test compressive strength of the high strength plugging agent is not less than 55Mpa, the plugging stage number of the plugging operation of the resin adhesive plugging agent is n, n is not less than 5 and not less than 1, and the extrusion amount q of the single-stage plugging high strength plugging agent is within the range of 0.02 m 3 ≤q≤0.25m 3 。
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