CN114991690B

CN114991690B - Formation pressure test method and device while drilling

Info

Publication number: CN114991690B
Application number: CN202111016552.8A
Authority: CN
Inventors: 刘伟; 付加胜; 赵庆; 李牧; 翟小强; 张瑞凇; 王振; 张国斌; 罗良波
Original assignee: China National Petroleum Corp; CNPC Engineering Technology R&D Co Ltd; Beijing Petroleum Machinery Co Ltd
Current assignee: China National Petroleum Corp; CNPC Engineering Technology R&D Co Ltd; Beijing Petroleum Machinery Co Ltd
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2024-08-02
Anticipated expiration: 2041-08-31
Also published as: CN114991690A

Abstract

The invention provides a method and a device for testing formation pressure while drilling. The device comprises: the system comprises a flow measuring unit, a pressure measuring unit and a pressure control system; the flow measurement unit comprises pumped drilling fluid flow measurement equipment and back flow drilling fluid flow measurement equipment; the pumping drilling fluid flow metering device is used for metering the flow of the drilling fluid injected into the drilling system, and the back flow drilling fluid flow metering device is used for metering the flow of the drilling fluid discharged from the drilling system; the pressure measurement unit comprises a riser pressure gauge, an annular pressure measurement while drilling tool and a wellhead pressure gauge; the riser pressure gauge is arranged at the riser manifold; an annulus pressure measurement while drilling tool is mounted in the bottom hole assembly for measuring the annulus pressure; the wellhead pressure gauge is arranged on the wellhead return pipeline and is used for measuring the pressure of the wellhead return drilling fluid; the pressure control system comprises back pressure control equipment arranged on a wellhead back pressure pipeline and is used for realizing regulation and control of wellhead back pressure.

Description

Formation pressure test method and device while drilling

Technical Field

The invention relates to a method and a device for testing formation pressure while drilling, and belongs to the technical fields of petroleum and natural gas drilling and completion, natural gas hydrate drilling and production and intelligent drilling.

Background

In drilling engineering, formation pore pressure, fracture pressure are the key geomechanical parameters for measuring wellbore stability. Among these, formation pore pressure is particularly important.

The usual formation pore pressure determination method is to estimate pore pressure using seismic and logging data, well drilling parameters; however, due to parameter errors and uncertain geological factors, estimated and predicted formation pore pressures often have large uncertainties, and accuracy is difficult to guarantee. Formation pore pressure and formation fracture pressure, determined using while-drilling data, are relatively accurate, typically by two methods: the method is relatively coarse, has low precision, is more suitable for approximate estimation and prediction, and cannot effectively determine the true values of the formation pore pressure and the fracture pressure; secondly, the special stratum pore pressure tester or the formation pressure while drilling tester is adopted for direct measurement, for example, the traditional cable type stratum pressure tester is adopted, and the method needs to independently lower a test tubular column, occupies long drilling machine time and is difficult to lower in a large-displacement well and a horizontal well, so that the comprehensive cost is high, and the efficiency is low. At present, internationally used stratum pressure testers while drilling, such as Testrak and GeoTAP, are advanced, and a cable type probe, a polar plate and a quartz pressure sensor are used for pressure testing during suspension periods of single connection and the like of drilling operation, but normal drilling construction is delayed to a certain extent, and the comprehensive cost is high; in addition, common formation while drilling pressure testers are repeated formation pressure testers (RFT, repeat Formation Tester), drill pipe testers (DST, drill String Test), and the like, but are relatively time-consuming and labor-consuming.

Disclosure of Invention

The invention aims to provide a formation pressure while drilling test method and device capable of rapidly and accurately determining formation pore pressure and/or formation fracture pressure.

In order to achieve the above object, the present invention provides a formation pressure while drilling testing device, wherein the device comprises:

The system comprises a flow measuring unit, a pressure measuring unit and a pressure control system;

the flow measurement unit comprises pumped drilling fluid flow measurement equipment and back-flow drilling fluid flow measurement equipment; the pumped drilling fluid flow metering device is used for metering the flow of the drilling fluid injected into the drilling system, and the back-off drilling fluid flow metering device is used for metering the flow of the drilling fluid discharged from the drilling system;

the pressure measurement unit comprises a riser pressure gauge, an annular pressure measurement while drilling tool and a wellhead pressure gauge; the riser pressure gauge is arranged at a riser manifold; the annulus pressure measurement while drilling tool is installed in the bottom hole assembly and is used for measuring the annulus pressure; the wellhead pressure gauge is arranged on a wellhead return pipeline and is used for measuring the pressure of wellhead return drilling fluid;

the pressure control system comprises back pressure control equipment arranged on a wellhead back pressure pipeline and is used for realizing regulation and control of wellhead back pressure.

In the formation pressure while drilling testing device, preferably, the pumped drilling fluid flow metering device comprises a slurry pump inlet flowmeter and a slurry supplementing pump inlet flowmeter; the slurry pump inlet flowmeter is arranged at an inlet pipeline of a slurry pump for supplying liquid to the vertical pipe and is used for metering the flow of drilling liquid pumped into the vertical pipe; the slurry supplementing pump inlet flowmeter is arranged at an inlet pipeline of the drilling fluid slurry supplementing pipeline slurry supplementing pump and is used for measuring the flow of the drilling fluid pumped into the drilling system by the slurry supplementing pump; the fluid supplementing pipeline refers to a drilling fluid input pipeline used when drilling fluid in a drilling system establishes ground short circulation.

In the formation pressure while drilling testing device, preferably, the flow rate measuring device for the flow rate of the back-off drilling fluid includes a drilling fluid outlet flow meter, and the drilling fluid outlet flow meter is arranged on a wellhead return pipeline and is used for measuring the flow rate of the drilling fluid returned from the wellhead.

In the formation pressure while drilling testing device, preferably, the back pressure control device comprises a first pneumatic control flat valve and a self-control throttle valve which are sequentially arranged on a wellhead return pipeline; the first pneumatic control flat valve is used for opening the connection between the automatic control throttle valve and the wellhead, and the automatic control throttle valve realizes the regulation and control of the wellhead back pressure by remotely controlling the opening degree of the automatic control throttle valve.

In the above-mentioned formation while drilling pressure testing apparatus, preferably, the pressure control system further includes a second pneumatically controlled plate valve provided on the drilling fluid make-up line for isolating the drilling fluid make-up line during circulation of the drilling fluid driven by a mud pump supplying the riser with fluid.

In the formation pressure while drilling testing apparatus described above, preferably, the formation pressure while drilling testing apparatus further includes an injection system including an injection pipe and an injection pressure gauge; the injection pipe is composed of a continuous oil pipe, a preset port of the wellhead blowout preventer stack stretches into the annular space of the shaft to a certain depth, and an injection pressure measuring meter is arranged at the lowest end of the injection pipe and is used for measuring the pressure of an injection port.

The invention also provides a formation pressure while drilling test method, which is carried out by using the formation pressure while drilling test device, and comprises the following steps:

Gradually reducing wellhead back pressure, recording the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system in real time, and performing bottom hole overflow judgment by using a working condition recognition model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system after reducing wellhead back pressure each time; if the well bottom overflow occurs or the well head back pressure is reduced to 0, the well head back pressure is not reduced any more; the working condition identification model is a model for judging working conditions based on the pressure of a vertical pipe, the pressure of an annulus, the pressure of a wellhead, the flow of drilling fluid injected into a drilling system and the flow of drilling fluid discharged from the drilling system; in the process of gradually reducing wellhead back pressure, the time interval for wellhead back pressure adjustment is not lower than the interval time for measuring signal feedback by the annular pressure measurement-while-drilling tool;

Determining the corresponding bottom hole pressure as the stratum pore pressure based on the riser pressure, the annular pressure and/or the wellhead pressure before the bottom hole overflow occurs; or alternatively; and determining the bottom hole pressure corresponding to the back pressure of 0 based on the riser pressure, the annulus pressure and/or the wellhead pressure after the back pressure drop of 0, and further determining that the formation pore pressure is smaller than the bottom hole pressure corresponding to the back pressure of 0.

In the formation while drilling pressure testing method described above, preferably, the method further comprises:

Before gradually reducing wellhead back pressure, injecting low-density drilling fluid (drilling fluid with density lower than that of original drilling fluid) into a shaft, so as to realize that bottom hole pressure reaches a preset value; the preset value should be as close as possible to but not below the formation pore pressure, and one skilled in the art can make a determination based on the predicted formation pore pressure;

more preferably, during the process of injecting low-density drilling fluid into the well bore, the pressure of the vertical pipe, the annular pressure and the pressure of the well head are monitored in real time, so that the bottom hole pressure is regulated and controlled according to the expected values as far as possible;

More preferably, the injecting of the low density drilling fluid into the wellbore is accomplished by: injecting a low-density drilling fluid into the annulus at a certain height, and adjusting the density of the original drilling fluid above the injection point, wherein the low-density drilling fluid comprises at least one of liquid phase drilling fluid and gas phase drilling fluid (preferably gas phase drilling fluid); further preferably, the density of the low density drilling fluid is less than 0.2g/cm ³ of the original drilling fluid;

More preferably, the injecting of the low density drilling fluid into the wellbore is accomplished by: injecting a low density drilling fluid through the riser, displacing the original drilling fluid in the drilling system, the low density drilling fluid comprising at least one of a liquid phase drilling fluid and a gas phase drilling fluid (preferably a liquid phase drilling fluid); further preferably, the density of the low density drilling fluid is less than 0.1g/cm ³ of the original drilling fluid density.

In the above preferred technical scheme, the wellhead back pressure is dynamically regulated and controlled after the hydrostatic column pressure is dynamically regulated and controlled, so that the bottom hole pressure is better controlled, and the bottom hole pressure can be greatly reduced by injecting the low-density drilling fluid or the low-density drilling fluid with a certain annular space height, so that the disadvantage that the formation pore pressure cannot be or is difficult to detect in the conventional drilling mode is overcome.

In the formation pressure while drilling test method, preferably, in the process of gradually reducing wellhead back pressure, the pressure reduction value of each wellhead back pressure is 0.2-0.5MPa.

In the formation pressure while drilling test method, preferably, in the process of gradually reducing wellhead back pressure, the pressure reduction value of the last wellhead back pressure does not exceed the pressure reduction value of the previous wellhead back pressure; in one embodiment, the pressure drop value of the first wellhead back pressure is 0.5MPa and the pressure drop value of the last wellhead back pressure is 0.2MPa.

In the formation pressure while drilling test method, preferably, the measurement time interval time of the riser pressure and the wellhead pressure is the same as the measurement time interval of the annulus pressure.

If the well bottom overflow occurs, the wellhead back pressure is not reduced, the wellhead back pressure is gradually increased until the well bottom overflow disappears, the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system are recorded in real time, and after the wellhead back pressure is increased each time, the well bottom overflow judgment is carried out by utilizing a working condition identification model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system;

Determining the corresponding bottom hole pressure as a formation pore pressure verification value based on the riser pressure, annulus pressure and/or wellhead pressure corresponding to the bottom hole overflow no longer occurring for the first time; correcting the determined formation pore pressure based on the formation pore pressure verification value; when the wellhead back pressure is gradually raised, the time interval for wellhead back pressure adjustment is not lower than the interval time for measuring signal feedback by the primary annulus pressure measurement-while-drilling tool;

in the preferred technical scheme, the correctness of the result is effectively ensured through positive and negative bidirectional tests.

In the formation pressure while drilling test method, preferably, the working condition identification model is a trained support vector machine working condition identification model, and can realize the identification of working conditions in overflow, leakage, simultaneous existence of overflow and leakage, no overflow and no leakage 4.

In a specific embodiment, the trained support vector machine condition recognition model is determined by:

Acquiring historical riser pressure, annulus pressure, wellhead pressure, flow of drilling fluid injected into a drilling system, flow data of drilling fluid discharged from the drilling system and working condition marks, and performing [0,1] normalization processing on the historical riser pressure, annulus pressure, wellhead pressure, flow of drilling fluid injected into the drilling system and flow data of drilling fluid discharged from the drilling system to obtain a training data set;

presetting 5 input parameters: riser pressure, annulus pressure, wellhead pressure, flow of drilling fluid injected into the drilling system and flow of drilling fluid discharged from the drilling system, 4 conditions of output: overflow, leakage, overflow and leakage coexist, and non-overflow and non-leakage support vector machine model;

training a support vector machine model by using the training data set, so as to obtain a trained support vector machine work identification model;

Preferably, the preset support vector machine model is of an SVM kernel function type, and comprises a linear kernel function, a polynomial kernel function, a radial basis kernel function, a multi-layer perceptron kernel function and/or the like;

Preferably, the support vector machine model training is performed in a cross-validation mode.

According to the above preferred technical scheme, a training data set is mapped from a low-dimensional space to a high-dimensional feature space by a support vector machine (SVM, support vector machine) method, and the problem of linear inseparable is converted into the problem of linear inseparable, so that 5 parameters are input: riser pressure, annulus pressure, wellhead pressure, flow of drilling fluid injected into the drilling system and flow of drilling fluid discharged from the drilling system, corresponding output of 4 conditions: overflow, leakage, overflow and leakage coexist, and the overflow and leakage are avoided. In order to improve the accuracy of early working condition discrimination, the training data is subjected to [0,1] normalization processing, then SVM kernel function types are optimized, the SVM kernel function types comprise linear kernel functions, polynomial kernel functions, radial basis kernel functions, multi-layer perceptron kernel functions and the like, and finally cross verification is carried out, so that a model is optimized.

In the above-mentioned formation pressure while drilling test method, preferably, performing the bottom hole overflow judgment by using the working condition identification model based on the measured riser pressure, annulus pressure, wellhead pressure, flow rate of the drilling fluid injected into the drilling system, and flow rate of the drilling fluid discharged from the drilling system includes:

Determining overflow or leakage amount, column pressure change value, annulus pressure change value and wellhead pressure change value based on the measured riser pressure, annulus pressure, wellhead pressure, drilling fluid flow injected into the drilling system and drilling fluid flow discharged from the drilling system, so as to judge whether bottom hole overflow occurs;

More preferably, the overflow amount is determined by the following formula:

Wherein: Δq _{Overflow valve} is the overflow amount; q _in (t) is the flow rate of drilling fluid injected into the drilling system; q _out (t) is the flow rate of drilling fluid discharged from the drilling system; the interval time t2-t1 is not less than the interval time of the measurement signal feedback by the primary annular pressure measurement while drilling tool (preferably the interval time of the measurement signal feedback by the primary annular pressure measurement while drilling tool);

More preferably, the leakage amount is determined by the following formula:

Wherein: Δq _{Leakage device} is the leakage amount; q _in (t) is the flow rate of drilling fluid injected into the drilling system; q _out (t) is the flow rate of drilling fluid discharged from the drilling system; the interval time t2-t1 is not less than the interval time of the measurement signal feedback by the primary annular pressure measurement while drilling tool (preferably the interval time of the measurement signal feedback by the primary annular pressure measurement while drilling tool).

In the above-described formation while drilling pressure testing method, preferably, the bottom hole pressure is determined by the following formula:

P_BHP＝P_PWD+ρ·g·(H_TVD+H_PWD)

Wherein P _BHP is bottom hole pressure; p _PWD is the annulus pressure; ρ is the drilling fluid density; g is gravity acceleration; h _TVD is the bottom hole depth; h _PWD is the depth of the measurement point for measuring the annular pressure.

In the above-described formation pressure while drilling test method, preferably, the bottom hole pressure is determined by the following formula:

P_BHP＝P_d+P_H-P_{l_in}

wherein P _BHP is bottom hole pressure; p _d is riser pressure; p _H is the hydrostatic column pressure in the water hole of the drill string; p _{l_in} is the drill string port friction resistance.

P_BHP＝P_h+P_{l_out}+P_back

Wherein P _BHP is bottom hole pressure; p _h is the hydrostatic column pressure of the drilling fluid in the borehole annulus; p _{l_out} is the wellbore annulus friction resistance; p _back is wellhead pressure.

Gradually increasing wellhead back pressure, recording the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system in real time, and performing bottom hole leakage judgment by using a working condition recognition model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system after each wellhead back pressure increase; if the well bottom leakage or the well top back pressure is increased to the highest value required by the well site, the well top back pressure is not increased any more; the working condition identification model is a model for judging working conditions based on the pressure of a vertical pipe, the pressure of an annulus, the pressure of a wellhead, the flow of drilling fluid injected into a drilling system and the flow of drilling fluid discharged from the drilling system; in the process of gradually increasing wellhead back pressure, the time interval for wellhead back pressure adjustment is not lower than the interval time for measuring signal feedback by the annular pressure measurement-while-drilling tool;

Determining the corresponding bottom hole pressure as the stratum fracture pressure based on the riser pressure, the annulus pressure and/or the wellhead pressure before the bottom hole leakage occurs; or alternatively; and determining that the back pressure is the bottom hole pressure corresponding to the highest wellsite requirement value based on the riser pressure, the annulus pressure and/or the wellhead pressure after the back pressure is increased to the highest wellsite requirement value, and further determining that the stratum fracture pressure is greater than the bottom hole pressure corresponding to the highest wellsite requirement value.

Before raising wellhead back pressure step by step, injecting high-density drilling fluid (drilling fluid with density higher than that of original drilling fluid) into a shaft to realize that bottom hole pressure reaches a preset value; the preset value should be as close as possible but not higher than the formation fracture pressure, and one skilled in the art can determine based on the predicted formation fracture pressure;

more preferably, during the process of injecting high-density drilling fluid into the well bore, the pressure of the vertical pipe, the annular pressure and the pressure of the well head are monitored in real time, so that the bottom hole pressure is regulated and controlled according to the expected values as far as possible;

more preferably, the injecting of the high density drilling fluid into the wellbore is accomplished by: injecting high-density drilling fluid into the annulus at a certain height, and adjusting the density of the original drilling fluid above the injection point; further preferably, the density of the high density drilling fluid is greater than the original drilling fluid density of 0.2g/cm ³;

More preferably, the injecting of the high density drilling fluid into the wellbore is accomplished by: injecting high-density drilling fluid through the vertical pipe to replace original drilling fluid in the drilling system; further preferably, the high density drilling fluid has a density greater than 0.1g/cm ³ of the original drilling fluid.

In the above preferred technical scheme, the wellhead back pressure is dynamically regulated and controlled after the hydrostatic column pressure is dynamically regulated and controlled, so that the bottom hole pressure is better controlled accurately, and the bottom hole pressure can be greatly improved by injecting high-density drilling fluid or high-density drilling fluid with a certain annular space height, so that the disadvantage that the conventional drilling mode cannot or is difficult to detect the formation fracture pressure is overcome.

In the formation pressure while drilling test method, preferably, in the process of gradually increasing wellhead back pressure, the pressure increasing value of each wellhead back pressure is 0.2-1.5MPa.

In the formation pressure while drilling test method, preferably, in the process of gradually increasing wellhead back pressure, the pressure increasing value of the last wellhead back pressure does not exceed the pressure increasing value of the previous wellhead back pressure; in a specific embodiment, the pressure rise value of the first wellhead back pressure is 1.5MPa, and the pressure rise value of the last wellhead back pressure is 0.2MPa.

If the well bottom leakage occurs, the well top back pressure is not increased any more, the well top back pressure is gradually reduced until the well bottom leakage disappears, the measured riser pressure, the annulus pressure, the well top pressure, the flow of the drilling fluid injected into the drilling system and the flow of the drilling fluid discharged from the drilling system are recorded in real time, and after the well top back pressure is reduced each time, the well bottom leakage judgment is carried out by utilizing a working condition identification model based on the measured riser pressure, the annulus pressure, the well top pressure, the flow of the drilling fluid injected into the drilling system and the flow of the drilling fluid discharged from the drilling system;

Determining the corresponding bottom hole pressure as a stratum fracture pressure verification value based on the riser pressure, annulus pressure and/or wellhead pressure corresponding to the bottom hole leakage no longer occurs for the first time; correcting the determined formation fracture pressure based on the formation fracture pressure verification value; when the wellhead back pressure is gradually reduced, the time interval of wellhead back pressure adjustment is not lower than the interval time of measuring signal feedback by the primary annulus pressure measurement-while-drilling tool;

According to the optimal technical scheme, through intelligent data characteristic analysis, the traditional stratum pore pressure and fracture pressure prediction accuracy is greatly improved, and uncertainty factors are removed.

In the above method for testing formation pressure while drilling, preferably, performing the bottom hole leakage judgment by using the working condition identification model based on the measured riser pressure, annulus pressure, wellhead pressure, flow rate of drilling fluid injected into the drilling system, and flow rate of drilling fluid discharged from the drilling system includes:

Determining overflow or leakage amount, column pressure change value, annulus pressure change value and wellhead pressure change value based on the measured riser pressure, annulus pressure, wellhead pressure, drilling fluid flow injected into the drilling system and drilling fluid flow discharged from the drilling system, so as to judge whether bottom hole leakage occurs;

More preferably, the overflow amount is determined by the following formula:

More preferably, the leakage amount is determined by the following formula:

P_BHP＝P_PWD+ρ·g·(H_TVD+H_PWD)

P_BHP＝P_d+P_H-P_{l_in}

P_BHP＝P_h+P_{l_out}+P_back

At present, the pressure control drilling technology and equipment can monitor the annular pressure in real time, ensure the accurate control of the bottom hole pressure, and accurately monitor the change of the flow of drilling fluid through a closed loop circulation system; the well bottom and annular pressure are precisely controlled by controlling the wellhead back pressure, and the well bottom and annular pressure can be controlled by an automatic closed-loop control system by using a high-precision automatic hydraulic throttle valve; drilling fluid return flow, temperature, and density may be measured using a coriolis flowmeter; the pressure of the vertical pipe and the back pressure of the wellhead can be measured by using a precise digital sensor, so that the precise control of pressure control is ensured. This provides technical support for the implementation of the present invention. According to the technical scheme provided by the invention, the back pressure of the wellhead is dynamically regulated and controlled, the bottom hole pressure is accurately controlled, the pressure balance of a shaft and a stratum and the occurrence and development conditions of overflow and leakage are monitored, and the analysis and judgment of the change of the annular pressure, the column pressure, the wellhead pressure, the drilling fluid injection quantity and the outflow quantity are combined, so that the technical problems of inaccurate prediction and monitoring of the pore pressure and the fracture pressure of the stratum of a complex ultra-deep well and a complex stratum are effectively solved, and the safety control capability of the shaft is improved.

According to the technical scheme provided by the invention, the bottom hole pressure is accurately regulated and controlled, the relative difference value between the bottom hole pressure and the formation pore pressure and the formation fracture pressure is controlled, and the micro overflow or micro leakage state is artificially caused, so that the true values of the formation pore pressure and the formation fracture pressure are accurately obtained. Therefore, the pressure safety operation interval of the shaft can be better guided, namely, the pressure upper boundary without leakage and the pressure lower boundary without overflow are maintained, so that the loss of time and expense caused by underground complexity is avoided, the non-production time is reduced, the comprehensive drilling efficiency and benefit are improved, and the safe and rapid drilling is realized.

The technical scheme provided by the method has the following beneficial effects:

(1) Compared with the traditional method and technological measures, the method can repeatedly test the formation pore pressure and the fracture pressure without stopping the circulation of drilling fluid.

(2) The pressure of the bottom hole is changed rapidly by regulating and controlling the back pressure of the wellhead, and the pore pressure and the fracture (leakage) pressure of the stratum can be measured rapidly by measuring the pressure of the annular pressure while drilling measuring tool and the pressure of the vertical pipe, measuring the back pressure of the wellhead, measuring the injection quantity of drilling fluid and measuring the reverse discharge capacity.

Drawings

FIG. 1 is a schematic diagram of an apparatus for testing formation pressure while drilling according to an embodiment.

FIG. 2A is a graph of annulus pressure measurements when flooding occurs in one embodiment.

FIG. 2B is a schematic diagram of drilling fluid injection and outflow when flooding occurs in one embodiment.

FIG. 3A is a graph of annulus pressure measurements when a leak occurs in one embodiment.

FIG. 3B is a schematic diagram of drilling fluid injection and outflow when a leak occurs in one embodiment.

FIG. 4 is a schematic flow chart of a support vector machine working condition identification model for identifying a downhole working condition structure according to an embodiment of the invention.

FIG. 5 is a flow chart of a method for testing formation pressure while drilling according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.

Referring to fig. 1, in one embodiment, the present invention provides a formation pressure while drilling testing apparatus, wherein the apparatus includes:

the system comprises a flow measurement unit, a pressure measurement unit, an injection system and a pressure control system;

The flow measurement unit comprises pumped drilling fluid flow measurement equipment and back flow drilling fluid flow measurement equipment; the pumping drilling fluid flow metering device is used for metering the flow of the drilling fluid injected into the drilling system, and the back flow drilling fluid flow metering device is used for metering the flow of the drilling fluid discharged from the drilling system; the flow metering device for the drilling fluid comprises a slurry pump inlet flowmeter 1 and a slurry supplementing pump inlet flowmeter 8, and the flow metering device for the back-off drilling fluid comprises a drilling fluid outlet flowmeter 12; the slurry pump inlet flowmeter 1 is arranged at an inlet pipeline of the slurry pump 2 for supplying liquid to the vertical pipe and is used for metering the flow of drilling liquid pumped into the vertical pipe; the slurry supplementing pump inlet flowmeter 8 is arranged at an inlet pipeline of a drilling fluid slurry supplementing pipeline slurry supplementing pump (not shown in fig. 1) and is used for measuring the flow rate of the drilling fluid pumped into the drilling system by the slurry supplementing pump; the drilling fluid outlet flowmeter 12 is arranged on the wellhead return pipeline and is used for measuring the flow of the wellhead return drilling fluid;

The pressure measurement unit comprises a riser pressure gauge 3, an annular pressure measurement while drilling tool 6 and a wellhead pressure gauge 9; riser pressure gauge 3 is mounted at the riser manifold; an annulus pressure measurement while drilling tool 6 is mounted in the bottom hole assembly for measuring the annulus pressure; the wellhead pressure gauge 9 is arranged on a wellhead return pipeline and is used for measuring the pressure of wellhead return drilling fluid;

The pressure control system comprises back pressure control equipment and a second pneumatic control flat valve 7 which are arranged on a wellhead back pressure pipeline and are used for realizing regulation and control of wellhead back pressure; the back pressure control equipment comprises a first pneumatic control flat valve 10 and an automatic control throttle valve 11 which are sequentially arranged on a wellhead return pipeline; the first pneumatic control flat valve 10 is used for opening the connection between the self-control throttle valve 11 and the wellhead, and the self-control throttle valve 12 realizes the regulation and control of the wellhead back pressure by remotely controlling the opening degree; a second pneumatically controlled plate valve 7 is arranged on the drilling fluid make-up line for isolating the drilling fluid make-up line during circulation of the drilling fluid driven by a mud pump supplying fluid to the riser; the first pneumatic control plate valve 10, the wellhead pressure gauge 9, the self-control throttle valve 11 and the drilling fluid outlet flowmeter 12 are arranged in sequence from the inlet to the outlet of the wellhead return pipeline, and the first pneumatic control plate valve 10, the wellhead pressure gauge 9, the self-control throttle valve 11 and the drilling fluid outlet flowmeter 12 are arranged in sequence;

The injection system comprises an injection pipe 4 and an injection pressure measuring table 5; the injection pipe 4 consists of a continuous oil pipe, a preset port of the wellhead blowout preventer stack extends into the annular space of the shaft to a certain depth, and an injection pressure measuring meter 5 is arranged at the lowest end of the injection pipe and is used for measuring the injection port pressure.

Wherein, the slurry pump inlet flowmeter 1 can be an ultrasonic mass flowmeter, and the drilling fluid outlet flowmeter 12 can be a mass flowmeter.

The fluid supplementing pipeline refers to a drilling fluid input pipeline used when drilling fluid in a drilling system establishes ground short circulation, and the outlet end of the fluid supplementing pipeline is communicated with the wellhead return pipeline and is close to the inlet end of the wellhead return pipeline; in the present invention, the set point of the outlet end of the make-up line on the return line is closer to the inlet end of the wellhead return line than the wellhead pressure gauge 9.

An embodiment of the present invention provides a method for testing formation pressure while drilling, which is performed by using the formation pressure while drilling testing device provided by the foregoing embodiment, and includes:

Step S11: gradually reducing wellhead back pressure, recording the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system in real time, and performing bottom hole overflow judgment by using a working condition recognition model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system after reducing wellhead back pressure each time; if the well bottom overflow occurs or the well head back pressure is reduced to 0, the well head back pressure is not reduced any more; the working condition identification model is a model for judging working conditions based on the pressure of a vertical pipe, the pressure of an annulus, the pressure of a wellhead, the flow of drilling fluid injected into a drilling system and the flow of drilling fluid discharged from the drilling system; in the process of gradually reducing wellhead back pressure, the time interval for wellhead back pressure adjustment is not lower than the interval time for measuring signal feedback by the annular pressure measurement-while-drilling tool;

Step S12: determining the corresponding bottom hole pressure as the stratum pore pressure based on the riser pressure, the annular pressure and/or the wellhead pressure before the bottom hole overflow occurs; or alternatively; and determining the bottom hole pressure corresponding to the back pressure of 0 based on the riser pressure, the annulus pressure and/or the wellhead pressure after the back pressure drop of 0, and further determining that the formation pore pressure is smaller than the bottom hole pressure corresponding to the back pressure of 0.

If, however, no overflow occurs after the wellhead back pressure has fallen to zero, the formation pore pressure effect can in principle be disregarded during the drilling process.

Further, the method further comprises:

Before proceeding to step S10, step S0 is first performed:

Injecting low-density drilling fluid (drilling fluid with density lower than that of the original drilling fluid) into a shaft to realize that bottom hole pressure reaches a preset value; the preset value should be as close as possible to but not below the formation pore pressure, and one skilled in the art can make a determination based on the predicted formation pore pressure;

in the process of injecting low-density drilling fluid into a shaft, the pressure of a vertical pipe, the pressure of an annulus and the pressure of a wellhead can be monitored in real time, so that the bottom hole pressure is regulated and controlled according to the expected value as far as possible;

still further, injecting a low density drilling fluid into the wellbore is accomplished by: injecting a low-density drilling fluid into the annulus at a certain height, and adjusting the density of the original drilling fluid above the injection point, wherein the low-density drilling fluid comprises at least one of liquid phase drilling fluid and gas phase drilling fluid (preferably gas phase drilling fluid); wherein, the low-density drilling fluid is preferably selected from drilling fluids with the density less than 0.2g/cm ³ of the original drilling fluid;

Still further, injecting a low density drilling fluid into the wellbore is accomplished by: injecting a low density drilling fluid through the riser, displacing the original drilling fluid in the drilling system, the low density drilling fluid comprising at least one of a liquid phase drilling fluid and a gas phase drilling fluid (preferably a liquid phase drilling fluid); wherein, the low-density drilling fluid is preferably drilling fluid with the density less than that of the original drilling fluid by 0.1g/cm ³.

In the above preferred technical solution, under the condition that other parameters of the drilling parameters are not changed, the density of the drilling fluid above the injection point is adjusted, if the injected drilling fluid is in a liquid phase, the change of the bottom hole pressure is caused as follows:

ΔP＝ΔρgH

wherein: Δρ is the density difference between the injected drilling fluid and the original drilling fluid; g is gravity acceleration; h is the injection point height; thus, if the injection depth is unchanged, the drilling fluid density change amount is:

the bottom hole pressure changes with time as:

Wherein: q (t) _in is the cumulative amount of low density drilling fluid returned to the injection port, the time from the return port; s _a is the annulus area;

if the drilling fluid density change amount is determined, the injection depth needs to be adjusted as follows:

Typically, because the coiled tubing depth is fixed, adjustments are more demanding on wellhead seals, and methods of varying drilling fluid density are typically used. If the injected drilling fluid is in a gas phase, the change of the bottom hole pressure becomes complex, and the influence on the change of the average hydrostatic column pressure is complex mainly because the volume is continuously collided and the pressure is continuously reduced in the process of upward gas migration, but the accurate pressure change can be realized by using special fluid calculation software, and in addition, the injection pressure measuring meter can accurately monitor the change process of the whole pressure so as to ensure that the bottom hole pressure is regulated and controlled according to an expected value.

In the above preferred technical scheme, the bottom hole pressure coarse adjustment is carried out by changing the drilling fluid density once, and the bottom hole pressure fine adjustment is carried out by changing the wellhead back pressure for a plurality of times, so that the determination of the stratum pore pressure can be realized more quickly and conveniently.

Further, in the process of gradually reducing wellhead back pressure, the pressure reduction value of each wellhead back pressure is 0.2-0.5MPa.

Further, in the process of gradually reducing wellhead back pressure, the pressure reduction value of the last wellhead back pressure does not exceed the pressure reduction value of the previous wellhead back pressure; for example, the pressure decrease value of the first wellhead back pressure is 0.5MPa, and then the pressure decrease value of each wellhead back pressure is gradually decreased until the pressure decrease value of the wellhead back pressure is 0.2MPa.

The change of wellhead back pressure can quickly adjust the bottom hole pressure, the wellhead pressure, the riser pressure and the annulus pressure (PWD measured value) form mutual influence, and the change values of the bottom hole pressure, the wellhead pressure, the riser pressure and the annulus pressure (PWD measured value) in a certain time period have certain equivalence, the wellhead back pressure and the riser pressure change ground are easy to observe, the signal feedback is quick, the signal feedback of the annulus pressure (PWD measured value) which is one of the key factors of underground complex such as overflow, leakage and the like is delayed for 3-5 minutes, but is closer to the underground complex occurrence place, and is the main influence factor of underground complex feature analysis. Searching for the formation pressure to be tested cannot be completed in one step, and each pressure adjustment amplitude and adjustment times need to be optimized, namelyΔp _step,n may be the same or different. In order to test the formation pore pressure conveniently, a larger pressure adjustment amplitude is adopted in the initial stage, after the pressure adjustment amplitude approaches to the formation pressure estimated value, a smaller pressure adjustment amplitude is adopted, the minimum value of each step of adjustment pressure is influenced by the control precision of the wellhead pressure, the highest value is required by the test precision of the formation pressure, and in general drilling design, the pressure of drilling fluid column and the circulating pressure consumption approach to the formation pore pressure, so that the wellhead back pressure can be reduced to be 0.2-0.5MPa, and the wellhead back pressure can be gradually reduced to be 0.2MPa from the larger value of 0.5 MPa.

Further, the time interval between the measurement of the riser pressure and the wellhead pressure is the same as the time interval between the measurement of the annulus pressure.

Further, the method further comprises:

Step S13: if the well bottom overflow occurs, the wellhead back pressure is not reduced, the wellhead back pressure is gradually increased until the well bottom overflow disappears, the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system are recorded in real time, and after the wellhead back pressure is increased each time, the well bottom overflow judgment is carried out by utilizing a working condition identification model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system;

Further, the bottom hole pressure is determined based on the annulus pressure, specifically by the following formula:

P_BHP＝P_PWD+P_lh+P_hc

Wherein P _BHP is bottom hole pressure; p _PWD is the annulus pressure; p _lh is the hydrostatic column pressure of the drilling fluid below the measuring point for measuring the annular pressure; p _hc is the well annulus friction resistance below the measured point of the annulus pressure;

under normal drilling conditions, the annulus pressure measurement while drilling tool (PWD tool) is very close to the bottom of the well, and the length is generally not more than 20-30 meters, so that the sum of the drilling fluid hydrostatic column pressure from the measuring point for measuring the annulus pressure to the bottom of the well and the friction resistance of the annulus of the well is relatively small, and therefore, the bottom hole pressure can be determined by the following formula:

P_BHP＝P_PWD+ρ·g·(H_TVD+H_PWD)

Further, the bottom hole pressure is determined based on the riser pressure, specifically by the following formula:

P_BHP＝P_d+P_H-P_{l_in}

Further, the bottom hole pressure is determined based on the wellhead pressure, specifically by the following formula:

P_BHP＝P_h+P_{l_out}+P_back

Further, the working condition identification model is a trained support vector machine working condition identification model, and can realize the identification of working conditions in overflow, leakage, simultaneous overflow and leakage 4;

Further, the trained support vector machine working condition recognition model is determined by the following method:

Training a support vector machine model by utilizing a training data set, so as to obtain a trained support vector machine work identification model;

The preset support vector machine model preferably adopts SVM kernel function types, including linear kernel functions, polynomial kernel functions, radial basis kernel functions, multi-layer perceptron kernel functions and the like;

the support vector machine model training is preferably performed in a cross-validation mode.

According to the above preferred technical scheme, a training data set is mapped from a low-dimensional space to a high-dimensional feature space by a support vector machine (SVM, support vector machine) method, and the problem of linear inseparable is converted into the problem of linear inseparable, so that 5 parameters are input: riser pressure, annulus pressure, wellhead pressure, flow of drilling fluid injected into the drilling system and flow of drilling fluid discharged from the drilling system, corresponding output of 4 conditions: overflow, leakage, overflow and leakage coexist, and the overflow and leakage are avoided. In order to improve the accuracy of early-stage working condition discrimination, the training data is subjected to [0,1] normalization processing, then SVM kernel function types are optimized, the SVM kernel function types comprise linear kernel functions, polynomial kernel functions, radial basis kernel functions, multi-layer perceptron kernel functions and the like, and finally cross verification is carried out, so that a model is optimized;

In a specific embodiment, a schematic flow chart of working condition structure recognition and working condition structure proceeding of the built trained support vector machine working condition recognition model is shown in fig. 4.

Further, performing a bottom hole overflow determination using the condition identification model based on the measured riser pressure, annulus pressure, wellhead pressure, flow rate of drilling fluid injected into the drilling system, and flow rate of drilling fluid discharged from the drilling system includes:

Still further, the overflow amount is determined by the following formula:

still further, the leak-off amount is determined by the following formula:

Wherein: Δq _{Leakage device} is the leakage amount; q _in (t) is the flow rate of drilling fluid injected into the drilling system; q _out (t) is the flow rate of drilling fluid discharged from the drilling system; the interval time t2-t1 is not less than the interval time of the measurement signal feedback by the primary annular pressure measurement while drilling tool (preferably the interval time of the measurement signal feedback by the primary annular pressure measurement while drilling tool);

Under normal circulation conditions, the flow data of the drilling fluid injected into the drilling system is derived from the slurry pump inlet flowmeter 1, and can also be calculated through the displacement of the slurry pump checked by the drilling fluid outlet flowmeter 12; and when the slurry pump stops running and the ground short-cycle control bottom hole pressure is established through the slurry supplementing pump, reading the data of the inlet flowmeter 8 of the slurry supplementing pump. The source of flow data for the drilling fluid discharged from the drilling system is the drilling fluid outlet flow meter 12.

Neglecting the influence of the elasticity of the well bore and the drilling fluid, and the like, the wellhead return change is controlled by the change of the bottom hole pressure and the stratum pressure difference. The magnitude of the flow change is a main basis for judging the occurrence of overflow or leakage in the pit, wherein the integral duration is a key factor, generally 3-5 minutes is required, namely, the interval t2-t1 is 3-5 minutes, the technical requirement is that an annular pressure measurement feedback value is contained as much as possible, and a time interval with enough flow integral accumulation is reserved for circulating inflow and outflow of drilling fluid, generally, delta Q is larger than +/-0.1 m ³, namely, an alarm threshold is provided, and the alarm threshold can be prolonged properly along with the increase of well depth and stratum complexity;

still further, the method further includes performing a coefficient determination of the cumulative change in outlet flow versus the change in bottom hole pressure:

setting the cumulative change of the outlet flow and the change of the bottom hole pressure to form a linear relation:

ΔQ＝k·ΔP_BF

Δq is overflow or leakage; k. is a proportionality coefficient; Δp _BF is the formation pore pressure and bottom hole pressure difference;

and fitting to obtain a proportionality coefficient based on the overflow or leakage data and the determined formation pore pressure data.

In one embodiment, the flooding discrimination is based on the amount of flooding or loss, the column pressure change, the annulus pressure change, the wellhead pressure change, and the annulus pressure, column pressure, specifically:

The calibration standards for gas overflow are: the overflow quantity is larger than the first rated value (positive) or the leakage quantity is smaller than the second rated value (negative), the column pressure change value, the annulus pressure change value and the wellhead pressure change value deviate (in normal working condition, the three values are equal or similar), the annular pressure is continuously gradually lower after being temporarily gradually higher than the annular pressure change trend line under normal working condition, and the column pressure is gradually lower than the column pressure change trend line under normal working condition; as shown in fig. 2A, 2B;

the calibration standards for liquid overflow are: the overflow quantity is larger than the first rated value (positive) or the leakage quantity is smaller than the second rated value (negative), the column pressure change value, the annulus pressure change value and the wellhead pressure change value deviate (in normal working condition, the three values are equal or similar), the annulus pressure is continuously gradually lower compared with the change trend line of the annulus pressure under the normal working condition, and the column pressure is gradually lower compared with the change trend line of the column pressure under the normal working condition.

When gas overflows, the gas passes through the well wall barrier, the pressure is not fully released, the gas pressure is basically the formation pressure, the measured value of the annular pressure is characterized in that the pressure is temporarily increased, the pressure of the vertical pipe is not obviously changed, but as the drilling fluid circulates, the bubbles rise along the annular space of the well hole, the volume is gradually expanded, the bubbles gather, and the circulating density of the drilling fluid is obviously reduced, so the measured value of the annular pressure is characterized in that the measured value continuously falls, the pressure of the vertical pipe continuously falls, the outflow flow of the drilling fluid at the return outlet is continuously larger than the fluid flow of the pump of the slurry pump, and the leakage amount continuously increases negatively or the overflow amount continuously increases positively.

When liquid overflows, stratum liquid is generally oil or water, the density is smaller than that of common drilling liquid, the original pressure is rapidly reduced to wellbore pressure through a well wall barrier due to the influence of expansibility, but the circulating drilling liquid density is only generated by the stratum fluid density, but the pressure difference between bottom hole pressure and stratum pressure is small and the time is short, so that the volume of overflowed stratum liquid is relatively small, the characteristics of annulus pressure measurement value and riser pressure change are relatively mild, the characteristic of slowly and continuously reducing is caused, the outflow flow of a drilling liquid return outlet is continuously larger than that of a slurry pump, and the leakage amount is continuously increased negatively or the overflow amount is continuously increased positively.

Under the condition that parameters such as drilling flow are not changed, the hydrostatic column pressure of drilling fluid and the annular friction resistance of a well bore are not changed, and the wellhead back pressure control value is adjusted, so that the change of bottom hole pressure is as follows: Δp _BHP＝ΔP_back. Under normal drilling conditions, the annulus pressure measurement while drilling tool (PWD tool) is very close to the bottom of the well, and the length is generally not more than 20-30 meters, so that the sum of the drilling fluid hydrostatic column pressure from the measuring point for measuring the annulus pressure to the bottom of the well and the friction resistance of the well annulus is relatively small, and under the conditions that the well track is not greatly adjusted and the change of the drilling fluid displacement is not great, the change of the bottom pressure is approximately regarded as no change, and the change value of the bottom pressure is delta P=delta P _PWD. Under the condition that other parameters are unchanged, the hydrostatic column pressure in the water hole of the drill string and the frictional resistance of the water hole of the drill string are unchanged, and the change value of the bottom hole pressure is deltaP=deltaP _BHP＝ΔP_d. From this, it can be seen that if no abnormal conditions such as underground complexity and the like occur and the spatial attitude of the PWD tool changes significantly, the values should be substantially consistent, and the equivalence of underground complexity judgment is achieved, but there is a difference in signal feedback time, the wellhead back pressure changes fastest, the riser pressure is inferior, but the pressure is mainly affected by pressure wave signal (the pressure wave propagation speed is 1500-2000m/s in liquid phase drilling fluid), the difference is in second level, the PWD pressure return value is slowest, the pressure is affected by the instrument transmission bandwidth and the like, and the change of the lagged wellhead back pressure value is about 3-5 minutes, but the change of capturing the PWD return pressure value is significant to whether overflow or leakage occurs truly at the bottom of the well.

The annulus pressure measurement normal feedback characteristics are:

P_PWD(t+Δt)＝P_PWD(t)+ρgΔH(Δt)+f(Δl_out(Δt))

Wherein P _PWD is annular pressure; ρ is the drilling fluid density; g is gravity acceleration; h _TVD is the bottom hole depth; ΔH is the vertical depth of the downstream of the PWD at Δt (the same vertical depth drilled at Δt); f (Δl _out (Δt)) is the annulus friction increase caused by the depth of the PWD run/drill.

The normal feedback characteristic of the pressure of the vertical pipe is as follows:

P_d(t+Δt)＝P_d(t)+f(Δl_in(Δt))+f(Δl_out(Δt))

Wherein P _d is the riser pressure; h _TVD is the bottom hole depth; f (Deltal _in (Deltat)) is the increase in water in-hole pressure loss caused by the increase in water in-hole length of the drill string due to the drilling depth in Deltat time; f (Δl _out (Δt)) is the annulus friction increase caused by the depth of the PWD run/drill.

With the increase of drilling depth, the annulus pressure measurement value and the riser pressure measurement value change value are basically consistent without the change of other parameters and working conditions, and if the annulus pressure measurement value and the riser pressure measurement value change value are inconsistent, overflow or leakage of an upper stratum and even blockage or fracture of a pipe string can occur.

The formation pressure while drilling test method is suitable for obtaining the formation pore pressure under the condition that the formation has fluid and the formation pressure can maintain pressure balance with the well bore pressure.

Step S21: gradually increasing wellhead back pressure, recording the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system in real time, and performing bottom hole leakage judgment by using a working condition recognition model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system after each wellhead back pressure increase; if the well bottom leakage or the well top back pressure is increased to the highest value required by the well site, the well top back pressure is not increased any more; the working condition identification model is a model for judging working conditions based on the pressure of a vertical pipe, the pressure of an annulus, the pressure of a wellhead, the flow of drilling fluid injected into a drilling system and the flow of drilling fluid discharged from the drilling system; in the process of gradually increasing wellhead back pressure, the time interval for wellhead back pressure adjustment is not lower than the interval time for measuring signal feedback by the annular pressure measurement-while-drilling tool;

Step S22: determining the corresponding bottom hole pressure as the stratum fracture pressure based on the riser pressure, the annulus pressure and/or the wellhead pressure before the bottom hole leakage occurs; or alternatively; and determining that the back pressure is the bottom hole pressure corresponding to the highest wellsite requirement value based on the riser pressure, the annulus pressure and/or the wellhead pressure after the back pressure is increased to the highest wellsite requirement value, and further determining that the stratum fracture pressure is greater than the bottom hole pressure corresponding to the highest wellsite requirement value.

If the wellhead back pressure is increased to the highest value required by the well site and no leakage occurs, the formation pressure resistance in the drilling process is considered to be enough, and the influence of the leakage formation is not considered.

Further, the method further comprises:

Step S20: before raising wellhead back pressure step by step, injecting high-density drilling fluid (drilling fluid with density higher than that of original drilling fluid) into a shaft to realize that bottom hole pressure reaches a preset value; the preset value should be as close as possible but not higher than the formation fracture pressure, and one skilled in the art can determine based on the predicted formation fracture pressure;

In the process of injecting high-density drilling fluid into a shaft, the pressure of a vertical pipe, the pressure of an annulus and the pressure of a wellhead can be monitored in real time, so that the bottom hole pressure is regulated and controlled according to the expected value as far as possible;

Still further, injection of high density drilling fluid into the wellbore is accomplished by: at a certain height into the annulus to the annular space in (a) adjusting the injection point to be above the density of the original drilling fluid; wherein, the high-density drilling fluid is preferably drilling fluid with density of 0.2g/cm ³ higher than that of the original drilling fluid;

still further, injection of high density drilling fluid into the wellbore is accomplished by: injecting high-density drilling fluid through the vertical pipe to replace original drilling fluid in the drilling system; wherein, the high-density drilling fluid is preferably drilling fluid with density of 0.1g/cm ³ higher than that of the original drilling fluid;

ΔP＝ΔρgH

the bottom hole pressure changes with time as:

In the above preferred technical scheme, the bottom hole pressure coarse adjustment is carried out by changing the drilling fluid density once, and the bottom hole pressure fine adjustment is carried out by changing the wellhead back pressure for a plurality of times, so that the determination of the stratum fracture pressure can be realized more quickly and conveniently.

Further, in the process of gradually increasing wellhead back pressure, the pressure increasing value of each wellhead back pressure is 0.2-1.5MPa.

Further, in the process of gradually increasing the wellhead back pressure, the pressure increasing value of the wellhead back pressure at the next time does not exceed the pressure increasing value of the wellhead back pressure at the previous time; for example, the pressure rise value of the first wellhead back pressure is 1.5MPa, and the pressure rise value of the last wellhead back pressure is 0.2MPa.

The change of wellhead back pressure can quickly adjust the bottom hole pressure, the wellhead pressure, the riser pressure and the annulus pressure (PWD measured value) form mutual influence, and the change values of the bottom hole pressure, the wellhead pressure, the riser pressure and the annulus pressure (PWD measured value) in a certain time period have certain equivalence, the wellhead back pressure and the riser pressure change ground are easy to observe, the signal feedback is quick, the signal feedback of the annulus pressure (PWD measured value) which is one of the key factors of underground complex such as overflow, leakage and the like is delayed for 3-5 minutes, but is closer to the underground complex occurrence place, and is the main influence factor of underground complex feature analysis. Searching for the formation pressure to be tested cannot be completed in one step, and each pressure adjustment amplitude and adjustment times need to be optimized, namelyΔp _step,n may be the same or different. In order to test the fracture pressure of the stratum conveniently, a larger pressure adjustment amplitude is adopted in the initial stage, after the pressure adjustment amplitude approaches to the stratum pressure estimated value, a smaller pressure adjustment amplitude is adopted, the minimum value of each step of adjustment pressure is influenced by the control precision of the wellhead pressure, the highest value is required by the test precision of the stratum pressure, and in general drilling design, the pressure of drilling fluid column and the circulating pressure consumption approach to the pore pressure of the stratum and are far away from the fracture pressure of the stratum, so that the back pressure of the wellhead is raised to be generally 0.2-1.5MPa, and the back pressure of the wellhead is gradually reduced to be 0.2MP from the larger value of 1.5 MPa.

Further, the method further comprises:

step S23: if the well bottom leakage occurs, the well top back pressure is not increased any more, the well top back pressure is gradually reduced until the well bottom leakage disappears, the measured riser pressure, the annulus pressure, the well top pressure, the flow of the drilling fluid injected into the drilling system and the flow of the drilling fluid discharged from the drilling system are recorded in real time, and after the well top back pressure is reduced each time, the well bottom leakage judgment is carried out by utilizing a working condition identification model based on the measured riser pressure, the annulus pressure, the well top pressure, the flow of the drilling fluid injected into the drilling system and the flow of the drilling fluid discharged from the drilling system;

P_BHP＝P_PWD+P_lh+P_hc

P_BHP＝P_PWD+ρ·g·(H_TVD+H_PWD)

P_BHP＝P_d+P_H-P_{l_in}

P_BHP＝P_h+P_{l_out}+P_back

Further, the working condition identification model is a trained support vector machine working condition identification model, and can realize the identification of working conditions in overflow, leakage, simultaneous overflow and leakage 4.

Further, utilizing the condition identification model to make a bottom hole leak determination based on the measured riser pressure, annulus pressure, wellhead pressure, flow rate of drilling fluid injected into the drilling system, and flow rate of drilling fluid discharged from the drilling system includes:

Still further, the overflow amount is determined by the following formula:

still further, the leak-off amount is determined by the following formula:

ΔQ＝k·ΔP_BF

The calibration standards for the occurrence of leakage are: the overflow quantity is smaller than a third rated value (negative) or the leakage quantity is larger than a fourth rated value (positive), the column pressure change value, the annulus pressure change value and the wellhead pressure change value deviate (in normal working conditions, the three values are equal or similar), compared with the situation that the annulus pressure is continuously gradually lowered after the trend line of the change of the annulus pressure is continuously lowered gradually under normal working conditions or is continuously lowered after the trend line of the change of the annulus pressure is temporarily raised, and compared with the situation that the column pressure is gradually lowered under normal working conditions; as shown in fig. 3A and 3B.

The PWD measurement is also gradually increased along with the increase of the wellhead back pressure, but if leakage occurs, it means that a part of fluid flows into the stratum to reduce the annulus friction resistance, the annulus pressure measurement is gradually decreased, the annulus pressure measurement is returned to have a certain time difference (generally 3-5 minutes), the wellhead back pressure is generally set to be the basic measurement time interval by the annulus pressure return interval measured by the PWD, if the stratum is replaced, the fluid with higher pressure enters the wellbore measurement, the annulus pressure is increased for a short time, but the annulus pressure measurement is continuously turned into being decreased along with the progress of leakage and replacement for a long time, the riser pressure is continuously decreased, the outflow flow of the drilling fluid return outlet is continuously smaller than the inflow flow of the slurry pump, and the leakage is continuously increased or the overflow is continuously increased negatively.

The annulus pressure measurement normal feedback characteristics are:

P_PWD(t+Δt)＝P_PWD(t)+ρgΔH(Δt)+f(Δl_out(Δt))

P_d(t+Δt)＝P_d(t)+f(Δl_in(Δt))+f(Δl_out(Δt))

The formation pressure while drilling test method provided by the method is suitable for solving the formation pore pressure under the condition that the formation has fluid and the formation pressure can maintain a pressure balance with the well bore pressure.

Example 1

The embodiment provides a formation pressure while drilling test method, which is performed by using the formation pressure while drilling test device shown in fig. 1, as shown in fig. 5, and comprises the following steps:

A. formation pore pressure determination step

A1, reducing the pressure of a drilling hydrostatic column: injecting low-density drilling fluid into the annulus at a certain height, and adjusting the density of the original drilling fluid above the injection point; the density of the low-density drilling fluid is less than that of the original drilling fluid by 0.2g/cm ³;

In the process of injecting low-density drilling fluid into a shaft, monitoring the pressure of a vertical pipe, the pressure of an annulus and the pressure of a well head in real time, and ensuring that the bottom hole pressure is regulated and controlled according to the expected value as far as possible;

a2, reducing wellhead pressure: gradually reducing wellhead back pressure at a certain interval;

Gradually reducing wellhead back pressure, recording the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system in real time, and performing bottom hole overflow judgment by using a working condition recognition model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system after reducing wellhead back pressure each time; if the well bottom overflow occurs or the well head back pressure is reduced to 0, the well head back pressure is not reduced any more; the working condition identification model is a model for judging working conditions based on the pressure of a vertical pipe, the pressure of an annulus, the pressure of a wellhead, the flow of drilling fluid injected into a drilling system and the flow of drilling fluid discharged from the drilling system;

In the process of gradually reducing wellhead back pressure, the time interval for wellhead back pressure adjustment is not lower than the interval time for measuring signal feedback by the annular pressure measurement-while-drilling tool;

wherein, the back pressure of the wellhead can be reduced by 0.2-0.5MPa, and the pressure is gradually reduced from 0.5MPa with a larger value to 0.2MPa;

A3, calculating the formation pore pressure;

determining the corresponding bottom hole pressure as the stratum pore pressure based on the riser pressure, the annular pressure and/or the wellhead pressure before the bottom hole overflow occurs; or alternatively; determining bottom hole pressure corresponding to back pressure 0 based on the riser pressure, annulus pressure and/or wellhead pressure after the back pressure drop is 0, and further determining that the formation pore pressure is smaller than the bottom hole pressure corresponding to the back pressure 0; wherein the bottom hole pressure is determined by the following formula:

P_BHP＝P_PWD+ρ·g·(H_TVD+H_PWD)

B. formation fracture pressure determination step

B1, raising the pressure of a drilling hydrostatic column: injecting high-density drilling fluid into the annulus at a certain height, and adjusting the density of the original drilling fluid above the injection point; the density of the high-density drilling fluid is greater than that of the original drilling fluid by 0.2g/cm ³;

in the process of injecting high-density drilling fluid into a shaft, monitoring the pressure of a vertical pipe, the pressure of an annulus and the pressure of a well head in real time, and ensuring that the bottom hole pressure is regulated and controlled according to the expected value as far as possible;

B2, raising wellhead pressure: gradually increasing wellhead back pressure at a certain interval;

Gradually increasing wellhead back pressure, recording the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system in real time, and performing bottom hole leakage judgment by using a working condition recognition model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system after each wellhead back pressure increase; if the well bottom leakage or the well top back pressure is increased to the highest value required by the well site, the well top back pressure is not increased any more; the working condition identification model is a model for judging working conditions based on the pressure of a vertical pipe, the pressure of an annulus, the pressure of a wellhead, the flow of drilling fluid injected into a drilling system and the flow of drilling fluid discharged from the drilling system;

In the process of gradually increasing wellhead back pressure, the time interval for wellhead back pressure adjustment is not lower than the interval time for measuring signal feedback by the annular pressure measurement-while-drilling tool;

wherein, the back pressure of the wellhead is increased to be 0.2-1.5MPa, and the pressure is gradually reduced from a larger value of 1.5MPa to 0.2MPa;

b3, calculating the formation fracture pressure;

Determining the corresponding bottom hole pressure as the stratum fracture pressure based on the riser pressure, the annulus pressure and/or the wellhead pressure before the bottom hole leakage occurs; or alternatively; determining that the back pressure is bottom hole pressure corresponding to the highest wellsite requirement value based on the riser pressure, the annulus pressure and/or the wellhead pressure after the back pressure is raised to the highest wellsite requirement value, and further determining that the stratum fracture pressure is greater than the bottom hole pressure corresponding to the highest wellsite requirement value; wherein the bottom hole pressure is determined by the following formula:

P_BHP＝P_PWD+ρ·g·(H_TVD+H_PWD)

The working condition identification model is a trained support vector machine working condition identification model, and can realize the identification of working conditions in overflow, leakage, simultaneous overflow and leakage 4; the trained support vector machine working condition recognition model is determined by the following steps:

The support vector machine model is a SVM kernel function type, and a linear kernel function, a polynomial kernel function, a radial basis kernel function or a multi-layer perceptron kernel function and the like are selected; as shown in FIG. 4, 1,2,3 and 4 respectively represent four working conditions of overflow, leakage, simultaneous existence of overflow and leakage, no overflow and no leakage; SVM _1-4 (1, 2,3, 4) represents an initial state, and inputs 5 parameters. First, based on the overflow, overflow-free, leak-free base judgment conditions, SVM _1-3 (1, 2, 3) and SVM _2-4 (2, 3, 4) are obtained. Then, entering a second layer, and obtaining SVM _1-2 (1, 2) and SVM _2-3 (2, 3) based on overflow and overflow leakage coexistence judging conditions; based on the missing, overflow-free, and leak-free judgment conditions, SVM _2-3 (2, 3) and SVM _3-4 (3, 4) are obtained. Finally, entering a third layer, and obtaining 1 (overflow) and 2 (leakage) based on overflow and leakage judging conditions; based on the leakage and overflow coexistence judging condition, defining 2 (leakage) and obtaining 3 (overflow and overflow coexistence); based on the conditions of leak coexistence, no overflow and no leak, 3 (leak coexistence) is defined, and 4 (no overflow and no leak) is obtained.

And when the support vector machine model is trained, a cross verification mode is adopted.

When the working condition is judged by using the trained support vector machine working condition identification model, the calibration standard of overflow and the calibration standard of leakage are as follows:

the calibration standards for overflow are: the overflow quantity is larger than the first rated value (positive) or the leakage quantity is smaller than the second rated value (negative), the column pressure change value, the annulus pressure change value and the wellhead pressure change value deviate (in normal working condition, the three values are equal or similar), compared with the annular pressure of a trend line of change of the annulus pressure under normal working condition, the annular pressure is continuously gradually lower after being temporarily gradually higher or continuously lower, and compared with the trend line of change of the column pressure under normal working condition, the column pressure is gradually lower;

The calibration standards for the occurrence of leakage are: the overflow quantity is smaller than the third rated value (negative) or the leakage quantity is larger than the fourth rated value (positive), the column pressure change value, the annulus pressure change value and the wellhead pressure change value deviate (in normal working condition, the three values are equal or similar), compared with the annular pressure of the change trend line of the annulus pressure under normal working condition, the annular pressure is continuously gradually reduced or continuously gradually reduced after being temporarily increased, and compared with the column pressure of the change trend line of the column pressure under normal working condition, the column pressure is gradually reduced.

Wherein the overflow amount is determined by the following formula:

Wherein: Δq _{Overflow valve} is the overflow amount; q _in (t) is the flow rate of drilling fluid injected into the drilling system; q _out (t) is the flow rate of drilling fluid discharged from the drilling system; the interval time t2-t1 is the interval time of the measurement signal feedback of the primary annular pressure measurement while drilling tool;

the leak-off amount is determined by the following formula:

Wherein: Δq _{Leakage device} is the leakage amount; q _in (t) is the flow rate of drilling fluid injected into the drilling system; q _out (t) is the flow rate of drilling fluid discharged from the drilling system; the interval time t2-t1 is the interval time of the measurement signal feedback of the primary annular pressure measurement while drilling tool;

The first rated value and the fourth rated value are 0.1m ³, and the second rated value and the third rated value are-0.1 m ³.

Preferred embodiments of the present invention are described above with reference to the accompanying drawings. The many features and advantages of the embodiments are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the embodiments which fall within the true spirit and scope thereof. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the embodiments of the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope thereof.

Claims

1. A method of formation pressure while drilling, the method comprising:

injecting low-density drilling fluid into a shaft to realize that the bottom hole pressure reaches a preset value; the low-density drilling fluid refers to the drilling fluid with density lower than that of the original drilling fluid;

Gradually reducing wellhead back pressure, recording the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system in real time, and performing bottom hole overflow judgment by using a working condition recognition model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system after reducing wellhead back pressure each time; if the well bottom overflow occurs or the well head back pressure is reduced to 0, the well head back pressure is not reduced any more; the working condition identification model is a model for judging working conditions based on the pressure of a vertical pipe, the pressure of an annulus, the pressure of a wellhead, the flow of drilling fluid injected into a drilling system and the flow of drilling fluid discharged from the drilling system; in the process of gradually reducing wellhead back pressure, the time interval for wellhead back pressure adjustment is not lower than the interval time for measuring signal feedback by the annular pressure measurement-while-drilling tool; the pressure reduction value of the wellhead back pressure at each time is 0.2-0.5MPa, and the pressure reduction value of the wellhead back pressure at the last time does not exceed the pressure reduction value of the wellhead back pressure at the previous time;

Determining the corresponding bottom hole pressure as the stratum pore pressure based on the riser pressure, the annular pressure and/or the wellhead pressure before the bottom hole overflow occurs; or alternatively; determining bottom hole pressure corresponding to back pressure 0 based on the riser pressure, annulus pressure and/or wellhead pressure after the back pressure drop is 0, and further determining that the formation pore pressure is smaller than the bottom hole pressure corresponding to the back pressure 0;

The method further comprises the steps of:

the working condition identification model is a trained support vector machine working condition identification model, and can realize the identification of 4 working conditions of overflow, leakage, simultaneous existence of overflow and leakage, no overflow and no leakage;

the trained support vector machine working condition recognition model is determined by the following steps:

Presetting 5 input parameters: riser pressure, annulus pressure, wellhead pressure, flow of drilling fluid injected into the drilling system and flow of drilling fluid discharged from the drilling system, 4 conditions are output: overflow, leakage, overflow and leakage coexist, and non-overflow and non-leakage support vector machine model;

and training the support vector machine model by using the training data set, so as to obtain a trained support vector machine work identification model.

2. The method of claim 1, wherein the injecting the low density drilling fluid into the wellbore is accomplished by: injecting low-density drilling fluid into the annulus at a certain height, and adjusting the density of the original drilling fluid above the injection point; the density of the low-density drilling fluid is less than that of the original drilling fluid by 0.2g/cm ³.

3. The method of claim 1, wherein the injecting the low density drilling fluid into the wellbore is accomplished by: injecting low-density drilling fluid through the vertical pipe, and replacing original drilling fluid in the drilling system; the density of the low-density drilling fluid is less than that of the original drilling fluid by 0.1g/cm ³.

4. The method of claim 1, wherein the riser pressure, wellhead pressure measurement interval time is the same as the annulus pressure measurement interval time.

5. The method of claim 1, wherein utilizing the condition identification model to make a bottom hole overflow determination based on the measured riser pressure, annulus pressure, wellhead pressure, flow rate of drilling fluid injected into the drilling system, and flow rate of drilling fluid discharged from the drilling system comprises:

Based on the measured riser pressure, annulus pressure, wellhead pressure, flow of drilling fluid injected into the drilling system and flow of drilling fluid discharged from the drilling system, an overflow or leak is determined, a riser pressure change value is determined, an annulus pressure change value is determined, a wellhead pressure change value is determined, and further whether bottom hole overflow occurs is judged.

6. The method of claim 5, wherein the overflow volume is determined by the following equation:

Wherein: Δq _{Overflow valve} is the overflow amount; q _in (t) is the flow rate of drilling fluid injected into the drilling system; q _out (t) is the flow rate of drilling fluid discharged from the drilling system; the interval time t2-t1 is not less than the interval time of the measurement signal feedback of the primary annulus pressure measurement while drilling tool.

7. The method of claim 5, wherein the leakage amount is determined by the following equation:

wherein: Δq _{Leakage device} is the leakage amount; q _in (t) is the flow rate of drilling fluid injected into the drilling system; q _out (t) is the flow rate of drilling fluid discharged from the drilling system; the interval time t2-t1 is not less than the interval time of the measurement signal feedback of the primary annulus pressure measurement while drilling tool.

8. The method of claim 1, wherein the bottom hole pressure is determined by the following equation:

P_BHP＝P_PWD+ρ·g·(H_TVD-H_PWD)

9. A method of formation pressure while drilling, the method comprising:

Injecting high-density drilling fluid into a shaft to realize that the bottom hole pressure reaches a preset value; the high-density drilling fluid refers to the drilling fluid with density higher than that of the original drilling fluid;

Gradually increasing wellhead back pressure, recording the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system in real time, and performing bottom hole leakage judgment by using a working condition recognition model based on the measured riser pressure, annulus pressure, wellhead pressure, the flow of drilling fluid injected into the drilling system and the flow of drilling fluid discharged from the drilling system after each wellhead back pressure increase; if the well bottom leakage or the well top back pressure is increased to the highest value required by the well site, the well top back pressure is not increased any more; the working condition identification model is a model for judging working conditions based on the pressure of a vertical pipe, the pressure of an annulus, the pressure of a wellhead, the flow of drilling fluid injected into a drilling system and the flow of drilling fluid discharged from the drilling system; in the process of gradually increasing wellhead back pressure, the time interval for wellhead back pressure adjustment is not lower than the interval time for measuring signal feedback by the annular pressure measurement-while-drilling tool; the pressure rise value of the wellhead back pressure every time is 0.2-1.5MP, and the pressure rise value of the wellhead back pressure at the last time does not exceed the pressure rise value of the wellhead back pressure at the previous time;

Determining the corresponding bottom hole pressure as the stratum fracture pressure based on the riser pressure, the annulus pressure and/or the wellhead pressure before the bottom hole leakage occurs; or alternatively; determining that the back pressure is bottom hole pressure corresponding to the highest wellsite requirement value based on the riser pressure, the annulus pressure and/or the wellhead pressure after the back pressure is raised to the highest wellsite requirement value, and further determining that the stratum fracture pressure is greater than the bottom hole pressure corresponding to the highest wellsite requirement value;

the method further comprises the steps of:

10. The method of claim 9, wherein the injecting high density drilling fluid into the wellbore is accomplished by: injecting high-density drilling fluid into the annulus at a certain height, and adjusting the density of the original drilling fluid above the injection point; the density of the high-density drilling fluid is greater than that of the original drilling fluid by 0.2g/cm ³.

11. The method of claim 10, wherein the injecting high density drilling fluid into the wellbore is accomplished by: injecting high-density drilling fluid through the vertical pipe to replace original drilling fluid in the drilling system; the density of the high-density drilling fluid is greater than that of the original drilling fluid by 0.1g/cm ³.

12. The method of claim 9, wherein the riser pressure, wellhead pressure measurement interval time is the same as the annulus pressure measurement interval time.

13. The method of claim 9, wherein utilizing the condition identification model to make a bottom hole leak determination based on the measured riser pressure, annulus pressure, wellhead pressure, flow rate of drilling fluid injected into the drilling system, and flow rate of drilling fluid discharged from the drilling system comprises:

Based on the measured riser pressure, annulus pressure, wellhead pressure, flow of drilling fluid injected into the drilling system and flow of drilling fluid discharged from the drilling system, an overflow or leak is determined, a riser pressure change value is determined, an annulus pressure change value is determined, a wellhead pressure change value is determined, and further whether a bottom hole leak occurs is determined.

14. The method of claim 13, wherein the overflow volume is determined by the following equation:

15. The method of claim 13, wherein the leakage amount is determined by the following equation:

16. The method of claim 10 or 14, wherein the bottom hole pressure is determined by the following equation:

P_BHP＝P_PWD+ρ·g·(H_TVD-H_PWD)