CN111764866A - Leaking stoppage method for leakage stratum - Google Patents
Leaking stoppage method for leakage stratum Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
- E21B33/138—Plastering the borehole wall; Injecting into the formation
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Abstract
The invention relates to a plugging method of a lost stratum, which comprises the following steps: s10, plugging the bridging material; s20, judging whether plugging is successful; if yes, normally drilling through the lost circulation stratum, and then executing step S60; if not, executing the steps S30-S60; s30, plugging while drilling and drilling through a leakage stratum; s40, controlling the ground squeeze pressure calculated by the pressure bearing capacity of the lost stratum to squeeze cement slurry for plugging; s50, building pressure-holding waiting set, drilling through the cement plug; and S60, testing the pressure bearing capacity of the stratum, and if the test is unqualified, executing the steps S40-S50 until the test of the pressure bearing capacity of the stratum is qualified. The invention can be used for guiding the drilling and plugging of the leakage stratum, reducing the operation risk, improving the operation efficiency, simultaneously improving the pressure bearing capacity of the leakage stratum, reducing the re-leakage risk and ensuring safe drilling.
Description
Technical Field
The invention relates to the technical field of well drilling, in particular to a plugging method for a lost stratum.
Background
In the process of offshore oil exploration and development, due to the requirement of a well track, leakage stratum such as a fault and a limestone layer are often drilled during well drilling, the leakage stoppage is difficult after the well leakage, even if the leakage stoppage is successful, the possibility of the occurrence of the leakage is very high along with the continuous uncovering of the leakage stratum, the leakage stoppage is required to be carried out again after the leakage stoppage is carried out, the operation period is seriously influenced, and the operation cost is increased. Meanwhile, as the pressure-bearing capacity of the lost stratum is low, in the process of continuously drilling after drilling through the lost stratum, along with the increase of the density of the drilling fluid, the equivalent drilling fluid density exceeds the pressure-bearing capacity of the lost stratum, so that the lost stratum leaks again, the operation period and the cost are influenced, and in severe cases, well control risks, stratum collapse and drilling jamming accidents or even well bore abandonment can occur.
Therefore, a set of systematic plugging method for drilling the stratum lost when encountering leakage is urgently needed to be designed.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method for plugging a lost formation, aiming at the above-mentioned defects in the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method of plugging a lost circulation formation is constructed comprising:
s10, plugging the bridging material;
s20, judging whether plugging is successful; if yes, normally drilling through the lost circulation stratum, and then executing step S60; if not, executing the steps S30-S60;
s30, plugging while drilling and drilling through a leakage stratum;
s40, controlling the ground squeeze pressure calculated by the pressure bearing capacity of the lost stratum to squeeze cement slurry for plugging;
s50, building pressure-building waiting-setting, drilling through cement plug
And S60, testing the pressure bearing capacity of the stratum, and if the test is unqualified, executing the steps S40-S50 until the test of the pressure bearing capacity of the stratum is qualified.
In one embodiment, the step S10 includes:
s101, lifting the drilling tool to a safe position;
s102, preparing bridging material plugging mud, and lowering the drilling tool to a leakage stratum;
s103, pumping plugging mud to the leaking stratum and the top of the leaking stratum;
and S104, lifting the drilling tool to the top of the plugging mud, and stopping the drilling tool statically or circularly.
In one embodiment, the step S20 includes:
s201, lowering a drilling tool to the bottom of a well, and opening the displacement of the drilling tool to a preset displacement;
s202, judging whether leakage occurs or not, if not, indicating that the leakage stoppage is successful, and if so, indicating that the leakage stoppage is unsuccessful.
In one embodiment, the step S30 includes:
and continuously adding plugging materials into the slurry, and drilling through the lost circulation stratum at a preset mechanical drilling speed by adopting a first displacement control drilling.
In one embodiment, the step S30 further includes:
in the drilling process, drilling one single reaming hole once, drilling one upright post reaming hole twice, and stopping drilling after drilling through the lost stratum by 10-15 m.
In one embodiment, the step S40 includes:
s401, calculating the pressure bearing capacity of the lost stratum required in the subsequent drilling process of the lost stratum;
s402, calculating the ground squeezing pressure of squeezing and injecting the plugging cement slurry according to the pressure bearing capacity of the leakage stratum;
s403, squeezing cement paste according to the ground squeezing pressure;
s404, in the cement paste squeezing and injecting process, monitoring and recording the total leakage amount in the well after the cement paste is discharged out of the drill rod and before the cement paste is squeezed, and determining the squeezed cement paste amount according to the leakage amount.
In one embodiment, the step S40 further includes: in the cement paste squeezing process, squeezing is carried out at a small discharge capacity.
In one embodiment, the step S403 includes:
when cement paste is extruded and injected for the first time, the first extrusion and injection amount is controlled to be half of the extrusion and injection amount of the cement paste;
judging whether the ground pressure of the first extrusion amount reaches the ground extrusion pressure or not;
if yes, the pump is stopped, and step S50 is executed;
if not, intermittently squeezing and injecting cement paste.
In one embodiment, the intermittent squeeze of cement slurry comprises:
and after the first cement slurry squeezing and injecting is finished, stopping the pump, squeezing and injecting the cement slurry every 20-30 minutes, wherein the squeezing and injecting amount of the cement slurry every time is half of the residual squeezing and injecting amount until the ground pressure reaches the ground squeezing and injecting pressure, stopping the pump, and executing the step S50.
In one embodiment, the step S50 includes:
and if no cement slurry is extruded in the step S40, releasing pressure and waiting for setting, and drilling a cement plug after 8-12 hours according to the strength of the ground cement slurry sample.
In one embodiment, the step S50 further includes:
and if cement paste is extruded in the step S40 and the ground pressure reaches the ground extrusion pressure, carrying out pressure building and waiting for setting until the cement paste sample on the ground is initially set, then carrying out pressure relief, and drilling the cement plug after 8-12 hours.
In one embodiment, the pressure build-up waiting time comprises:
under the condition that the blowout preventer is closed, the ground pressure is kept to be the ground squeezing pressure calculated by the pressure bearing capacity of the lost stratum;
if the ground pressure is reduced, the pressure is supplemented to the ground squeezing pressure;
and if the ground pressure rises, releasing the pressure to the ground squeezing pressure.
In one embodiment, the step S60 includes:
closing the blowout preventer;
testing the pressure bearing capacity of the stratum;
judging whether the stratum pressure-bearing capacity is the pressure-bearing capacity of the lost stratum or not;
if so, stopping the pump, and stabilizing the pressure for 10-15 minutes;
judging whether the current stratum pressure-bearing capacity is reduced or not, and if not, determining that the test is qualified; if the test result is reduced, the test is failed.
In one embodiment, the displacement range of small displacement is: 80L/min to 160L/min.
The implementation of the leaking stoppage method for the leaking stratum has the following beneficial effects: the method comprises the following steps: s10, plugging the bridging material; s20, judging whether plugging is successful; if yes, normally drilling through the lost circulation stratum, and then executing step S60; if not, executing the steps S30-S60; s30, plugging while drilling and drilling through a leakage stratum; s40, controlling the ground squeeze pressure calculated by the pressure bearing capacity of the lost stratum to squeeze cement slurry for plugging; s50, building pressure-holding waiting set, drilling through the cement plug; and S60, testing the pressure bearing capacity of the stratum, and if the test is unqualified, executing the steps S40-S50 until the test of the pressure bearing capacity of the stratum is qualified. The invention can be used for guiding the drilling and plugging of the leakage stratum, reducing the operation risk, improving the operation efficiency, simultaneously improving the pressure bearing capacity of the leakage stratum, reducing the re-leakage risk and ensuring safe drilling.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
fig. 1 is a schematic flow chart of a method for plugging a lost formation according to an embodiment of the present invention.
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
Referring to fig. 1, a schematic flow chart of a method for plugging a lost formation according to an embodiment of the present invention is provided.
As shown in fig. 1, the method for plugging a lost formation comprises the following steps: step S10, step S20, step S30, step S40, step S50, and step S60.
And step S10, plugging the bridging material.
Step S10 includes:
s101, the drilling tool is lifted to a safe position.
S102, bridging material plugging mud is prepared, and the drilling tool is lowered to a leakage stratum.
S103, pumping plugging mud to the leaking stratum and the top of the leaking stratum.
And S104, lifting the drilling tool to the top of the plugging mud, and stopping the drilling tool statically or circularly.
In the drilling process, after the drilling tool is drilled to uncover the lost formation and the lost circulation occurs, the drilling tool is tripped to a safe position (step S101). In some embodiments, tripping to a safe position refers to tripping about 100m above the thief zone or into the upper casing to prevent the drilling tool from being buried in the open hole due to loss of fluid pressure in the wellbore caused by lost circulation.
In some embodiments, the adapting material plugging mud is prepared by using inert materials with different shapes (such as particles, sheets, fibers) and sizes (thick, medium and thin), and bridging material plugging mud with different gradations and depths is prepared according to different leakage rates, and is directly injected into a leakage layer, and bridging materials are bridged and filled in a leakage channel along with the leakage of drilling fluid under the action of pressure difference, so that the purpose of plugging is achieved. The granular materials include, but are not limited to, common walnut shells, rubber particles, crushed plastic particles, diatomite, perlite, quicklime, asphalt powder and the like; fibrous material: mainly from plants, minerals and a series of synthetic fibers, such as sawdust, peanut shells, corn cobs, bagasse, cottonseed hulls, waste palm ropes and the like; sheet materials include, but are not limited to, mica sheets, rice hulls, cellophane, and the like, which are commonly used. Current bridging materials for offshore applications include, but are not limited to, PF-BLN1, PF-BLN2, and PF-BLN3 formulated using a blend of particulate, sheet, and fibrous inert materials of varying sizes.
In the step S104, in the process of plugging, the drilling tool needs to be kept moving up and down to prevent the occurrence of complex situations such as drill sticking.
Step S20, judging whether plugging is successful; if yes, drilling the lost circulation stratum normally, and executing step S60; if not, steps S30-S60 are executed.
If plugging is successful, the lost circulation formation is drilled normally, and the operation of step S60 is performed.
Further, step S20 includes:
step S201, lowering the drilling tool to the bottom of the well, and opening the displacement of the drilling tool to a preset displacement.
Step S202, judging whether leakage occurs or not, if no leakage occurs, the leakage stoppage is successful, and if the leakage occurs, the leakage stoppage is unsuccessful.
In this embodiment, the preset displacement is a normal drilling displacement. Namely, after the bridging material stops leaking in the step S10, the drilling tool is lowered to the bottom of the well, the discharge capacity is opened to the normal drilling discharge capacity, if no leakage occurs at the moment, the plugging is successful, and if the leakage occurs, the plugging is unsuccessful. Wherein, at the test loss in-process, the discharge capacity of drilling tool needs slowly to promote upwards gradually, then can not continue to promote the discharge capacity test upwards after taking place the loss, prevents that the leakage rate from increasing, leads to the well to lose and returns. In some embodiments, the drilling displacement is the displacement of the drilled formation.
And step S30, plugging the leak while drilling and drilling through the lost circulation stratum.
Wherein, step S30 includes: and continuously adding plugging materials into the slurry, and drilling through the lost circulation stratum at a preset mechanical drilling speed by adopting a first displacement control drilling.
In the embodiment of the invention, the preset mechanical drilling speed is less than 20 m/h. In some embodiments, the first displacement is around 1/2 for normal drilling, e.g., 4000L/min for normal drilling of a 12-1/4 "wellbore, then 2000L/min for the first displacement, 2400L/min for normal drilling of a 8-1/2" wellbore, then 1200L/min for the first displacement.
Further, step S30 further includes: in the drilling process, drilling one single reaming hole once, drilling one upright post reaming hole twice, and stopping drilling after drilling through the lost stratum by 10-15 m.
In some embodiments, leak rates are sensitive to displacement, pump pressure, and therefore, using low displacement drilling during drilling prevents the leak rate from expanding and even losing returns. In addition, the discharge capacity in the drilling process is low, the annulus return speed is low due to well leakage, the well is difficult to clean, the drilling speed of the drilling machine is controlled to be less than 20m/h in the drilling process, one single reaming is finished each time, and two reaming is finished each time one upright post is drilled, so that the underground safety is ensured. In some embodiments, large-particle plugging materials are used for plugging while drilling due to high leakage speed, in order to ensure the concentration of the plugging materials during drilling and avoid the plugging materials from being removed by a solid control system, and in the process of forcibly drilling a leakage stratum, the sieve cloth of the vibrating screen is detached, so that the plugging materials and rock debris are returned to a sand basin in a closed circuit after being returned. In some embodiments, each drill pipe is referred to as a single in the field, and the hole is scribed up and down once for each drill pipe single drilled. On site, every three drill rods are called as an upright post, and the upright post is scratched twice up and down when one drill rod is drilled.
And step S40, controlling the ground squeeze pressure calculated by the pressure bearing capacity of the lost stratum to squeeze cement slurry for plugging.
Specifically, after drilling through a lost circulation stratum, tripping out, replacing a cementing drilling tool into a well, lowering the cementing drilling tool to the bottom of the lost circulation stratum, injecting plugging cement slurry, tripping out to the top of the plugging cement slurry by 30-50 m, closing a blowout preventer, and then squeezing the cement slurry.
Further, step S40 includes:
and S401, calculating the pressure bearing capacity of the lost stratum required in the subsequent drilling process of the lost stratum.
In some embodiments, the lost formation bearing capacity is the maximum of two:
firstly, simulating the required pressure bearing capacity of the leakage stratum according to the condition that the leakage stratum is not pressed when the maximum drilling fluid density required by drilling the lower stratum is circulated, wherein the theory is PF＝9.81×10-3×ρ×H+PbIn the formula: pFThe bearing capacity (MPa) of the lost formation is obtained, and rho is the maximum drilling fluid density (g/cm) required by drilling the lower formation3) H is the vertical depth (m) of the top of the lost formation, PbThe annular pressure loss (MPa) above the lost circulation formation.
Second, according to the lost formation well section sleeveThe pressure bearing capacity of the lost formation required by the maximum annular liquid column pressure during the casing cementing process without leaking the lost formation is generally the annular static liquid column pressure of the lost formation after the casing cementing of the lost formation well section is finished according to the formula PF＝9.81×10-3× ρ × H, wherein P isFThe bearing capacity (MPa) of the leakage stratum, and rho is the density (g/cm) of the annular fluid above the top of the leakage stratum3) And H is the vertical depth (m) at the top of the leakage formation.
And S402, calculating the ground squeezing pressure of squeezing and injecting the plugging cement slurry according to the pressure bearing capacity of the leakage stratum.
In some embodiments, P is according to the formulaF-9.81×10-3× rho × H can calculate the ground squeezing pressure of squeezing plugging cement slurry, wherein P is the ground squeezing pressure (MPa) and P is the ground squeezing pressureFThe pressure bearing capacity (MPa) of the lost formation, and rho is the density (g/cm) of the fluid above the top of the lost formation3) And H is the vertical depth (m) at the top of the leakage formation.
And S403, squeezing cement paste according to the ground squeezing pressure.
And S404, monitoring and recording the total leakage amount of the cement slurry in the well after the cement slurry is discharged out of the drill rod and before the cement slurry is squeezed in the cement slurry squeezing process, and determining the cement slurry squeezing amount according to the leakage amount.
In the embodiment of the invention, the squeezed cement slurry amount is determined according to the leakage amount, so that 30m of cement slurry is ensured above the leakage stratum.
Specifically, the total leakage amount in the well after cement slurry is discharged out of the drill rod and before cement squeezing is set as A, the cement slurry squeezing amount is set as B, and the total cement slurry injection amount in the well is set as Q. In the whole cement paste squeezing process, the sum of the leakage A and the squeezing B is controlled to be equal to the difference between the total cement paste amount Q injected into the well and the open hole volume N and the open hole volume K of 30m of the thickness of the leakage stratum, namely A + B is Q-N-K. After cement slurry is squeezed out, 30m of cement slurry is ensured above the leaking stratum, the leaking stoppage can be finished, the leaking stratum is covered by the cement slurry, the success of leaking stoppage is ensured, and the success rate of leaking stoppage is improved.
Further, step S40 further includes: in the cement paste squeezing process, squeezing is carried out at a small discharge capacity. Wherein, the displacement range of the small displacement is as follows: 80L/min to 160L/min.
Further, step S403 includes: when cement paste is extruded and injected for the first time, the first extrusion and injection amount is controlled to be half of the extrusion and injection amount B of the cement paste; judging whether the ground pressure of the first extrusion amount reaches the ground extrusion pressure or not; if yes, the pump is stopped, and step S50 is executed; if not, intermittently squeezing and injecting cement paste.
Wherein, the intermittent squeeze cement paste is as follows: and after the first cement slurry squeezing and injecting is finished, stopping the pump, squeezing and injecting the cement slurry every 20-30 minutes, wherein the squeezing and injecting amount of the cement slurry every time is half of the residual squeezing and injecting amount until the ground pressure reaches the ground squeezing and injecting pressure, stopping the pump, and executing the step S50.
Assuming that the first extrusion amount is B1, the first extrusion amount of the first cement slurry extrusion is 1/2 (the difference between the total injection well cement slurry amount Q minus the lost formation thickness open hole volume N, 30m open hole volume K, and slurry leakage amount a), that is, B1 is 1/2 (Q-N-K-a). And if the ground pressure reaches the ground squeezing pressure, stopping the pump, and building the pressure to wait for coagulation. And if the ground pressure does not reach the ground squeezing pressure, intermittently squeezing cement, stopping the pump, squeezing and injecting cement paste every 20-30 min, and stopping the pump until the ground pressure reaches the ground squeezing pressure, wherein the squeezing and injecting amount is 1/2 (the residual squeezing and injecting amount) each time, and the pump is stopped, and the time is set when the pressure is suppressed. The extrusion injection amount of each time is half of the residual extrusion injection amount, so that the plugging cement slurry at least covers 30m above the lost formation after the extrusion injection of the cement slurry is finished. In some embodiments, the amount of plugging cement slurry per squeeze may be 1/3 (the remaining squeeze).
In the embodiment of the invention, the residual extrusion injection amount is the difference of the total cement slurry amount Q in the injection well minus the open hole volume N of the thickness of the lost stratum, the open hole volume K of 30m, the slurry leakage amount A and the cement slurry amount extruded. Therefore, the second bolus B2 was 1/2 (residual bolus), i.e., B2 was 1/2 (Q-N-K-a-B1), the third bolus was B3 was 1/2 (Q-N-K-a-B1-B2), and so on.
And step S50, building pressure and waiting for setting, and drilling through the cement plug.
Step S50 includes:
and if no cement slurry is extruded in the step S40, releasing pressure and waiting for setting, and drilling a cement plug after 8-12 hours according to the strength of the ground cement slurry sample.
Further, step S50 further includes:
and if cement paste is extruded in the step S40 and the ground pressure reaches the ground extrusion pressure, carrying out pressure building and waiting for setting until the cement paste sample on the ground is initially set, then carrying out pressure relief, and drilling the cement plug after 8-12 hours.
In some embodiments, the set-back time is a surface squeeze pressure calculated by maintaining the surface pressure at the bearing capacity of the lost circulation formation with the blowout preventer closed until the surface cement sample is initially set. During the pressure building and waiting for setting, if the ground pressure is reduced, the pressure is supplemented to the ground squeezing pressure, and if the ground pressure is increased, the pressure is released to the ground squeezing pressure.
And the stratum after the leakage stoppage has certain bearing capacity can be ensured by pressure-building and waiting for coagulation.
And S60, testing the pressure bearing capacity of the stratum, and if the test is unqualified, executing S40-S50 until the test of the pressure bearing capacity of the stratum is qualified.
Specifically, step S60 includes: closing the blowout preventer; testing the pressure bearing capacity of the stratum; judging whether the stratum bearing capacity is the pressure bearing capacity of the leakage stratum or not; if so, stopping the pump, and stabilizing the pressure for 10-15 minutes; judging whether the current stratum pressure-bearing capacity is reduced or not, and if not, determining that the test is qualified; if the test result is reduced, the test is failed. Further, if the pressure is reduced or the pressure bearing capacity of the leaking stratum is not achieved, the step S40-the step S50 are continued until the stratum pressure test is qualified, so that the risk of repeated leakage in subsequent operation is avoided, and the operation risk is reduced.
The invention performs plugging by plugging while drilling and forcibly drilling through the leaking stratum, and then performs extrusion plugging of plugging cement slurry by controlling the ground extrusion pressure calculated by the pressure bearing capacity of the leaking stratum, thereby improving the success rate of plugging and the operation efficiency. When leaking stoppage, the pressure bearing capacity of a leakage stratum is improved, the risk of repeated leakage is reduced, safe drilling is ensured, and the operation risk is reduced.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.
Claims (14)
1. A method for plugging a lost formation, comprising:
s10, plugging the bridging material;
s20, judging whether plugging is successful; if yes, normally drilling through the lost circulation stratum, and then executing step S60; if not, executing the steps S30-S60;
s30, plugging while drilling and drilling through a leakage stratum;
s40, controlling the ground squeeze pressure calculated by the pressure bearing capacity of the lost stratum to squeeze cement slurry for plugging;
s50, building pressure-holding waiting set, drilling through the cement plug;
and S60, testing the pressure bearing capacity of the stratum, and if the test is unqualified, executing the steps S40-S50 until the test of the pressure bearing capacity of the stratum is qualified.
2. A method of plugging a lost circulation formation according to claim 1, wherein said step S10 comprises:
s101, lifting the drilling tool to a safe position;
s102, preparing bridging material plugging mud, and lowering the drilling tool to a leakage stratum;
s103, pumping plugging mud to the leaking stratum and the top of the leaking stratum;
and S104, lifting the drilling tool to the top of the plugging mud, and stopping the drilling tool statically or circularly.
3. A method of plugging a lost circulation formation according to claim 1, wherein said step S20 comprises:
s201, lowering a drilling tool to the bottom of a well, and opening the displacement of the drilling tool to a preset displacement;
s202, judging whether leakage occurs or not, if not, indicating that the leakage stoppage is successful, and if so, indicating that the leakage stoppage is unsuccessful.
4. A method of plugging a lost circulation formation according to claim 1, wherein said step S30 comprises:
and continuously adding plugging materials into the slurry, and drilling through the lost circulation stratum at a preset mechanical drilling speed by adopting a first displacement control drilling.
5. A method for plugging a lost circulation formation according to claim 4, wherein said step S30 further comprises:
in the drilling process, drilling one single reaming hole once, drilling one upright post reaming hole twice, and stopping drilling after drilling through the lost stratum by 10-15 m.
6. A method of plugging a lost circulation formation according to claim 1, wherein said step S40 comprises:
s401, calculating the pressure bearing capacity of the lost stratum required in the subsequent drilling process of the lost stratum;
s402, calculating the ground squeezing pressure of squeezing and injecting the plugging cement slurry according to the pressure bearing capacity of the leakage stratum;
s403, squeezing cement paste according to the ground squeezing pressure;
s404, in the cement paste squeezing and injecting process, monitoring and recording the total leakage amount in the well after the cement paste is discharged out of the drill rod and before the cement paste is squeezed, and determining the squeezed cement paste amount according to the leakage amount.
7. A method for plugging a lost circulation formation according to claim 6, wherein said step S40 further comprises: in the cement paste squeezing process, squeezing is carried out at a small discharge capacity.
8. A method for plugging a lost circulation formation according to claim 6, wherein said step S403 comprises:
when cement paste is extruded and injected for the first time, the first extrusion and injection amount is controlled to be half of the extrusion and injection amount of the cement paste;
judging whether the ground pressure of the first extrusion amount reaches the ground extrusion pressure or not;
if yes, the pump is stopped, and step S50 is executed;
if not, intermittently squeezing and injecting cement paste.
9. A method of plugging a lost circulation formation according to claim 8, wherein said intermittently injecting cement slurry comprises:
and after the first cement slurry squeezing and injecting is finished, stopping the pump, squeezing and injecting the cement slurry every 20-30 minutes, wherein the squeezing and injecting amount of the cement slurry every time is half of the residual squeezing and injecting amount until the ground pressure reaches the ground squeezing and injecting pressure, stopping the pump, and executing the step S50.
10. A method of plugging a lost circulation formation according to claim 1, wherein said step S50 comprises:
and if no cement slurry is extruded in the step S40, releasing pressure and waiting for setting, and drilling a cement plug after 8-12 hours according to the strength of the ground cement slurry sample.
11. A method of plugging a lost circulation formation according to claim 1, wherein said step S50 further comprises:
and if cement paste is extruded in the step S40 and the ground pressure reaches the ground extrusion pressure, carrying out pressure building and waiting for setting until the cement paste sample on the ground is initially set, then carrying out pressure relief, and drilling the cement plug after 8-12 hours.
12. A method of plugging a lost circulation formation according to claim 11, wherein said pressure build-up waiting solidification comprises:
under the condition that the blowout preventer is closed, the ground pressure is kept to be the ground squeezing pressure calculated by the pressure bearing capacity of the lost stratum;
if the ground pressure is reduced, the pressure is supplemented to the ground squeezing pressure;
and if the ground pressure rises, releasing the pressure to the ground squeezing pressure.
13. A method of plugging a lost circulation formation according to claim 1, wherein said step S60 comprises:
closing the blowout preventer;
testing the pressure bearing capacity of the stratum;
judging whether the stratum pressure-bearing capacity is the pressure-bearing capacity of the lost stratum or not;
if so, stopping the pump, and stabilizing the pressure for 10-15 minutes;
judging whether the current stratum pressure-bearing capacity is reduced or not, and if not, determining that the test is qualified; if the test result is reduced, the test is failed.
14. A method of plugging a lost circulation formation according to claim 7, wherein the displacement range of small displacement is: 80L/min to 160L/min.
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