CN110598248B - A Discrimination Method for Killing Stages and Ending Conditions by Direct Pushing - Google Patents

Abstract

The invention discloses a method for judging well kill stages and end conditions by a direct push method. The method comprises the following steps: S1, logging in the shut-in data, formation and fluid physical property parameters after shut-in through geological logging data and adjacent well data; S2 , process the data and parameters described in S1 and draw the theoretical wellbore pressure change curve; S3, process the data collected through the wellhead pressure sensor and the bottom hole pressure sensor and draw the actual wellbore pressure change curve; S4, analyze the theoretical wellbore pressure The change curve and the actual wellbore pressure change curve are used to identify and judge the killing stage; S5, the end condition of killing the well is judged. The invention has the beneficial effects that the killing stage can be judged in combination with the change of the flow resistance and the variation law of the wellhead pressure in the killing process, so as to accurately control the killing process and guarantee the safe operation of the well killing and the protection of the reservoir.

Description

A method for judging well kill stage and end condition by direct push method

technical field

The invention relates to the technical field of oil drilling well control, in particular to a method for judging well killing stages and end conditions of a direct push method.

Background technique

At present, with the stricter requirements for environmental protection in my country, the pressure on environmental protection of oil and gas drilling has been further increased. However, with the continuous expansion of the field of oil and gas exploration and development, drilling from onshore to tidal flats and shallow seas, from shallow to deep layers, is becoming more and more difficult, and overflow occurs from time to time, which is difficult to completely avoid. The discharge of overflows and contaminated drilling fluids has become a difficult problem for traditional choke-circulation well control methods, especially when drilling into formations with toxic gases such as hydrogen sulfide, and when the circulation cannot be established such as drill pipe damage, traditional well control methods Technology cannot control overflow quickly. In order to deal with complex formations, implement fast drilling in a safe and high-quality manner, and take into account the national requirements for environmental protection, well control technology must be taken as an important part of research and development.

The direct-push well control technology can be used regardless of whether there are drilling tools in the wellbore under the premise of shut-in. The high pressure at the wellhead can quickly push the overflow back into the formation, especially for drilling encounters such as hydrogen sulfide, etc. Toxic gas intrusion, direct push method of well killing can effectively prevent toxic gas from reaching the ground. The direct-push kill well control technology can effectively control the overflow, while effectively avoiding the environmental pollution caused by the overflow, which meets the requirements of environmental protection. However, the existing direct push method for killing well control technology does not compare the change law of the measured data of well killing with the change law of wellbore pressure in the theoretical well killing stage to obtain the actual killing stage, which is judged based on the idea of reservoir protection. The composition of the fluid in the wellbore and the pressure of the hydrostatic column make it impossible to accurately grasp the killing process, and it is impossible to provide safety guarantees for the wellbore and formation during the killing process. Therefore, there is an urgent need for a direct inference method that combines the change of flow resistance and the change of wellhead pressure during the killing process to distinguish the killing stage, so as to accurately control the killing process, and ensure the safe operation of the well and the protection of the reservoir. A method for judging well kill stages and end conditions.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the shortcomings of the prior art, and to provide a method for judging the well kill stage and end conditions of the direct push method.

The object of the present invention is realized through the following technical solutions: a kind of method for discriminating the well kill stage and the end condition of the direct push method, it comprises the following steps:

S1. Input the shut-in data, formation and fluid physical property parameters after shut-in through geological logging data and adjacent well data;

S2. Process the data and parameters described in S1 and draw a theoretical wellbore pressure variation curve;

S3. Process the data collected by the wellhead pressure sensor and the bottom hole pressure sensor and draw the actual wellbore pressure change curve;

S4. Analyze the theoretical wellbore pressure change curve and the actual wellbore pressure change curve, and identify and judge the killing stage;

S5. Discrimination of the killing end condition.

The step S2 includes the following sub-steps:

S21. Calculate killing displacement and killing fluid density;

S22. Determine the composition relationship of the pressure in the wellbore during the killing process;

S23. Calculate the air column pressure;

S24, draw the wellbore pressure variation law in the killing stage and analyze the theoretical well killing curve;

The step S3 includes the following sub-steps:

S31, transmitting the collected data to the data processing system through the signal receiver through the wellhead pressure sensor and the bottom hole pressure sensor;

S32. The data processing system performs cleaning and noise reduction preprocessing on the data;

S33, the data processing system analyzes the variation law of the wellbore pressure in real time, and draws the actual wellbore pressure variation curve.

In the step S4, the kill stage is determined according to the similarity.

The specific condition for judging the end condition of the well kill in the step S5 is that the overflow in the wellbore is completely pushed back to the formation and the hydrostatic column pressure in the wellbore meets the well control requirement.

The formation and fluid physical property parameters described in the step S1 include formation pressure, rock porosity, permeability, production layer thickness, gas density, gas viscosity, wellbore size and formation pressure boundary; post-well shut-in data includes wellbore structure , drilling tool assembly, shut-in casing pressure, shut-in vertical pressure, drilling fluid outlet density, drilling fluid viscosity, drilling fluid density, fluid distribution in the wellbore and fluid distribution in the wellbore.

Before the step S3, the step of killing a physical model is further included, and the physical model for killing the well includes a blowout preventer group (1) arranged on the top of the well and a signal receiver (2) arranged on the blowout preventer group (1). ), the signal receiver (2) is electrically connected with the data processing system, the bottom hole is provided with a bottom hole pressure sensor (3), the top of the well is provided with a wellhead pressure sensor (4), a wellhead pressure sensor (4) and a bottom hole pressure sensor ( 3) Both are electrically connected to the signal receiver (2), a drill pipe (5) is arranged in the blowout preventer group (1), the drill pipe (5) extends downward in the well, and a drill bit ( 6).

The present invention has the following advantages:

(1) In the present invention, the wellbore pressure in each stage of well killing is calculated theoretically, and the law of wellbore pressure change in each stage is obtained. In the actual killing stage, based on the idea of reservoir protection, by judging the fluid composition and hydrostatic column pressure in the wellbore, a process of judging the end conditions of the direct push method is proposed, which can reduce the risk of contaminating the reservoir.

(2) The present invention provides a guarantee for the safety of the wellbore and formation during the killing process by accurately mastering the killing process, thereby providing theoretical guidance for the implementation of the killing operation.

Description of drawings

Fig. 1 is the discrimination flow chart of the present invention;

Fig. 2 is the flow chart of judging the end condition of killing well;

Fig. 3 is the schematic diagram of the physical model of well killing;

In the figure, 1- blowout preventer group, 2- signal receiver, 3- bottom hole pressure sensor, 4- wellhead pressure sensor, 5- drill pipe, 6- drill bit, 7- kill fluid, 8- drilling fluid, 9 -Gas-liquid two-phase flow, 10-gas column, 11-formation.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings, and the protection scope of the present invention is not limited to the following:

As shown in Figure 1, a method for judging the killing stage and end conditions of the direct push method, which includes the following steps:

S1. Input the shut-in data, formation and fluid physical property parameters after shut-in through geological logging data and adjacent well data. The formation and fluid physical property parameters include formation pressure, rock porosity, permeability, production layer thickness, gas density, Gas viscosity, wellbore size and formation pressure boundary; post-well shut-in data include wellbore structure, BHA, shut-in casing pressure, shut-in vertical pressure, drilling fluid outlet density, drilling fluid viscosity, drilling fluid density, wellbore Fluid distribution and fluid distribution in the wellbore;

S2. Process the data and parameters described in S1 and draw a theoretical wellbore pressure variation curve, including the following sub-steps:

S21. Calculate the killing displacement and the killing fluid density, and the specific calculation steps are as follows:

The design principle of the killing fluid density is: under the condition of ensuring the safety of the wellbore, use a higher density of the killing fluid as much as possible to quickly establish a balance to ensure that the drilling fluid is not pushed back or is pushed back into the formation. The calculation formula is as follows:

However, according to this principle, sometimes the formation may be pressurized and leaked because the density of the killing fluid is too high and the wellbore pressure is too high during the killing process. At this time, it is necessary to appropriately reduce the killing fluid density through trial calculation to meet the wellbore safety requirements, but it cannot be lower than the minimum killing fluid density ρ _k ′. The calculation formula is as follows:

In the formula, P _e is the additional safety pressure, 3-5MPa; H is the well depth, m; h _m is the length of the original wellbore uncontaminated drilling fluid, m; g is the acceleration of gravity, m/s ² ;

The design principle of killing fluid displacement is as follows: the downward velocity of the killing fluid must be greater than the upward slipping velocity of the bubbles, so as to ensure that the gas in the wellbore is completely removed and the well is killed successfully. However, the killing displacement cannot be greater than the formation-wellbore safety condition, and the formation cannot be crushed and the wellbore damaged, resulting in more serious accidents. The calculation formula is as follows:

The formula for calculating the minimum kill fluid displacement is as follows:

Q _min = v _gr A (3)

v _gr is the gas slippage velocity, m/s; ρ _m , ρ _g are the drilling fluid density and gas density, respectively, kg/m ³ ; σ is the surface tension, 10 ^-3 N/m; A is the annular cross-sectional area, m ² ;

The formula for calculating the maximum displacement is as follows:

Q _max <min(Q ₁ ,Q ₂ ,Q ₃ ,Q ₄ ) (5)

In the formula: Q ₁ is the maximum kill displacement allowed by the wellhead equipment under pressure, m ³ /s; Q ₂ is the maximum kill displacement allowed by the bottom hole fracturing pressure, m ³ /s; Q ₃ is the casing shoe Maximum kill displacement allowed by fracturing pressure, m ³ /s; Q ₄ is the maximum kill displacement allowed by casing internal pressure, m ³ /s;

S22. Determine the pressure composition relationship in the wellbore during the killing process, and the specific steps are as follows:

In the initial stage of well killing, the bottom hole pressure may be less than the formation pressure. At the moment when the well kill starts, flow friction is generated, and then as the gas is continuously compressed, the force of the compressed gas increases and the wellhead pressure continues to rise until the bottom hole pressure equals the formation pressure. This stage is called the dynamic sealing stage. At this stage, the wellhead pressure and flow resistance have the following relationship:

P _a =P _C +P _f +P _p -P _h (6)

where P _a is the wellhead pressure, MPa; P _h is the hydrostatic column pressure, MPa; P _f is the flow friction resistance, MPa; PC is the force generated by the compressed natural gas, MPa; _{P p} is the formation pressure, MPa.

When the bottom hole pressure is equal to the formation pressure, the overflow fluid begins to be pushed back to the formation. At this time, the gas compressive force reaches the maximum, and as the wellbore gas phase is pushed back to the formation, it slowly decreases until zero. When the liquid phase is pushed back to the formation, its seepage resistance is different, and a turning point will occur in the kill curve. After the turning point, due to the change of the fluid type in the wellbore, the fluid flow friction resistance and the composition of the hydrostatic column pressure in the wellbore will also change. , the wellhead pressure has the following relationship with various pressures in the wellbore:

P _a =P _C +P _f +P _p +ΔP-P _h (7)

where P _a is the wellhead pressure, MPa; P _h is the hydrostatic column pressure, MPa; P _f is the flow friction resistance, MPa; PC _C is the force generated by the compressed natural gas, MPa; P _p is the formation pressure, MPa; ΔP _i is the seepage resistance of a certain type of fluid, MPa;

During the killing process, the pressure in the wellbore changes continuously with the killing, and the wellhead pressure changes with the change of the flow resistance. The flow resistance is composed of the fluid flow friction, the seepage resistance generated in the process of the fluid being pushed back into the formation, the formation pressure, and the gas column pressure generated after the gas column in the wellbore is compressed. The composition of various pressures at different stages is shown in Table 1. .

Table 1 Composition of various pressures in different killing stages

S23, air column pressure calculation, the specific calculation steps are as follows:

The pressure in the wellbore includes the hydrostatic column pressure, and its calculation formula is as follows:

P _hi =0.0098ρ _i H _i

The flow friction calculation formula is as follows:

where f _i is the Fanning friction coefficient of a certain type of fluid; ρ _i is the density of a certain type of fluid, Kg/m ³ ; D _w and D _z are the inner diameter of the casing and the outer diameter of the drill string, respectively, in mm; _Hi is the certain type of fluid The length in the wellbore, m; v is the flow rate of the killing fluid, m/s;

The calculation formula of seepage resistance is as follows:

Where: Q is the kill displacement, m ³ /d; K _φ is the fluid formation flow coefficient, μm ² ; μ _i is the viscosity of a certain type of fluid, mPa·s; ΔP _i is the seepage resistance of a certain type of fluid, MPa; r _e and r _w are the outer edge radius and borehole radius controlled by the well, respectively, m; h _r is the thickness of the reservoir, m;

The gas column pressure is composed of the pressure at which the killing fluid compresses the original wellbore gas and continues to invade the gas. The calculation formula is as follows:

P _C = P _C1 + P _C2 (10)

In the formula: P _C1 and P _C2 are the gas column pressure of the freewheeling effect and the gas column pressure generated by the original wellbore gas compression, respectively, MPa;

The calculation formula of the after-flow effect gas column pressure is as follows:

The gas column pressure generated by compressing the gas in the original wellbore is ^[6] :

S24, draw the wellbore pressure variation law in the killing stage and analyze the theoretical well killing curve. The specific steps are as follows:

After obtaining the physical properties, fluid parameters of the formation, and relevant data after shut-in, calculate the density of the killing fluid according to formulas (1) and (2), and select the optimal displacement of the killing fluid according to formulas (3) and (4). Formulas (6) and (7) determine the relationship between the wellhead pressure and the pressure in the wellbore. Combine Table 1 to determine the composition of the pressure in the wellbore. Calculate the relevant pressure by formulas (8), (9), and (10), and analyze the composition of the pressure in the wellbore. The variation law of the wellbore pressure at each stage is drawn by using the drawing software to draw the wellbore pressure variation curve.

S3. Process the data collected by the wellhead and bottom hole pressure sensors and draw the actual wellbore pressure change curve, which includes the following sub-steps:

S31. Before the step S3, it also includes the step of killing a physical model. The killing physical model includes a blowout preventer group 1 arranged on the top of the well, and a signal receiver 2 arranged on the blowout preventer group 1. The signal receiving The device 2 is electrically connected with the data processing system, a bottom hole pressure sensor 3 is arranged at the bottom of the well, and a wellhead pressure sensor 4 is arranged at the top of the well. A drill pipe 5 is arranged in the blower group 1, the drill pipe 5 extends downward in the well, and a drill bit 6 is installed at the extended end;

S32, transmit the collected data to the data processing system through the signal receiver through the wellhead pressure sensor and the bottom hole pressure sensor;

S33. The data processing system performs cleaning and noise reduction preprocessing on the data;

S34. The data processing system analyzes the variation law of wellbore pressure in real time, and draws the actual wellbore pressure variation curve;

S4. Analyze the theoretical wellbore pressure change curve and the actual wellbore pressure change curve, identify and judge the killing stage: analyze the change law of the processed wellbore pressure data through the data analysis software and compare and analyze the change law of the theoretical wellbore pressure data, according to the similarity Identifying the killing stage specifically includes the following steps: after the actual data is preprocessed, the data is regarded as a group, and as the killing progresses, the change law between each group and the previous group of data is analyzed and compared with the theoretical pressure of each pressure. The law of well stage change is compared and analyzed, and the change law with the highest similarity is the actual kill stage;

S5. As shown in Figure 2, the specific conditions for judging the end conditions of well kill are that the overflow in the wellbore is completely pushed back to the formation and the static liquid column pressure in the wellbore meets the well control requirements, which specifically includes the following steps:

S51, according to step S4, judge whether to complete the push back stage of the overflow, and the overflow includes gas and gas-liquid two-phase flow;

S52. Determine whether the hydrostatic column pressure at this time meets the well control requirements, that is, the hydrostatic column pressure in the wellbore has balanced the formation pressure and has an additional safety pressure of 3-5MPa;

S53. If the above two conditions are satisfied, the well killing can be ended.

In the present invention, the wellbore pressure in each stage of well killing is calculated theoretically, and the law of wellbore pressure variation in each stage is obtained. , based on the idea of reservoir protection, by judging the fluid composition and hydrostatic column pressure in the wellbore, a process of judging the end conditions of the direct push method is proposed, which can reduce the risk of contaminating the reservoir. The present invention provides a guarantee for the safety of the wellbore and the formation during the well killing process by accurately mastering the well killing process, thereby providing theoretical guidance for the implementation of the well killing operation.

The foregoing are only preferred embodiments of the present invention, and it should be understood that the present invention is not limited to the forms disclosed herein, and should not be construed as an exclusion of other embodiments, but may be used in various other combinations, modifications, and environments, and Modifications can be made within the scope of the concepts described herein, from the above teachings or from skill or knowledge in the relevant field. However, modifications and changes made by those skilled in the art do not depart from the spirit and scope of the present invention, and should all fall within the protection scope of the appended claims of the present invention.

Claims (6)

1. a discriminating method of direct push method kill stage and termination condition, is characterized in that: it comprises the following steps: S1. Input the shut-in data, formation and fluid physical property parameters after shut-in through geological logging data and adjacent well data; S2. Process the data and parameters described in S1 and draw a theoretical wellbore pressure variation curve; S3. Process the data collected by the wellhead pressure sensor and the bottom hole pressure sensor and draw the actual wellbore pressure change curve; S4. Analyze the theoretical wellbore pressure change curve and the actual wellbore pressure change curve, and identify and judge the killing stage; S5. Judgment of killing end conditions: The specific conditions for judging the end conditions of well killing are that the overflow in the wellbore is completely pushed back to the formation and the hydrostatic column pressure in the wellbore meets the well control requirements, which specifically includes the following steps: S51, according to step S4, judge whether to complete the push back stage of the overflow, and the overflow includes gas and gas-liquid two-phase flow; S52. Determine whether the hydrostatic column pressure at this time meets the well control requirements, that is, the hydrostatic column pressure in the wellbore has balanced the formation pressure and a safety pressure of 3-5MPa is added; S53. If the above two conditions are met, the well killing can be ended; The step S2 includes the following sub-steps: S21. Calculate killing displacement and killing fluid density; S22. Determine the composition relationship of the pressure in the wellbore during the killing process; S23. Calculate the air column pressure; S24, draw the wellbore pressure variation law in the killing stage and analyze the theoretical well killing curve. 2. The method for judging the well kill stage and end condition of a direct push method according to claim 1, wherein the step S3 comprises the following sub-steps: S31, transmitting the collected data to the data processing system through the signal receiver through the wellhead pressure sensor and the bottom hole pressure sensor; S32. The data processing system performs cleaning and noise reduction preprocessing on the data; S33, the data processing system analyzes the variation law of the wellbore pressure in real time, and draws the actual wellbore pressure variation curve. 3 . The method for judging the kill stage and the end condition of the direct push method according to claim 1 , wherein in the step S4 , the kill stage is judged according to the similarity. 4 . 4. the method for judging a kind of direct push method kill stage and end condition according to claim 1, it is characterized in that: the specific condition of judging the kill end condition in the described step S5 is that the overflow in the wellbore is completely pushed back to the formation and the hydrostatic column pressure in the wellbore meets well control requirements. 5 . The method for judging the well kill stage and end condition of the direct push method according to claim 1 , wherein the formation and fluid physical property parameters described in the step S1 include formation pressure, rock porosity, and permeability. 6 . , production layer thickness, gas density, gas viscosity, wellbore size and formation pressure boundary; post-well shut-in data include wellbore structure, drilling tool assembly, shut-in casing pressure, shut-in vertical pressure, drilling fluid outlet density, drilling fluid Viscosity, drilling fluid density, fluid distribution in the wellbore, and fluid distribution in the wellbore. 6 . The method for judging the well kill stage and the end condition of the direct push method according to claim 1 , wherein the step S3 further comprises the step of killing a physical model, and the physical model of killing a well includes setting The blowout preventer group (1) on the top of the well, the signal receiver (2) arranged on the blowout preventer group (1), the signal receiver (2) is electrically connected with the data processing system, and the bottom hole pressure is set at the bottom of the well A sensor (3), a wellhead pressure sensor (4) is provided on the top of the well, and both the wellhead pressure sensor (4) and the bottom hole pressure sensor (3) are electrically connected to the signal receiver (2), and the blowout preventer group (1) A drill pipe (5) is arranged inside, the drill pipe (5) extends downward in the well, and a drill bit (6) is installed at the extending end.

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