Method, system, storage medium and computing device for evaluating formation pore pressure

Abstract

The present invention relates to a method, system, storage medium and computing device for evaluating formation pore pressure. The method includes: determining the equivalent drilling fluid density of bottom hole pressure under different working conditions; obtaining the gas logging values under different working conditions, and determining the range of equivalent drilling fluid density of formation pore pressure at the current measuring point according to the change trend of the gas logging values and the equivalent drilling fluid density of bottom hole pressure under different working conditions; and determining the range of formation pore pressure at the current measuring point according to the range of equivalent drilling fluid density of formation pore pressure at the current measuring point. The present invention does not need to rely on a prediction model, can realize the evaluation of formation pore pressure while drilling, and has the advantages of low cost and easy popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of downhole safety monitoring in oil and gas exploration and development drilling, and particularly to a method, system, storage medium and computing device for evaluating formation pore pressure. Background Art

[0002] Traditional methods for obtaining formation pore pressure in the section to be drilled mainly include predicting formation pore pressure based on seismic data of the block and logging data (such as acoustic wave, gamma ray, spontaneous potential, compensated neutron, etc.) of the same horizon in adjacent wells. However, such methods have strong uncertainty and the formation pore pressure in different regions and lithologies depends highly on the model empirical coefficients. It is difficult to obtain formation pore pressure data based on logging data for risk exploration wells without adjacent wells, and it is impossible to achieve formation pore pressure evaluation while drilling according to such methods.

[0003] Real-time formation pore pressure monitoring and evaluation based on the measurement of drilling parameters (such as acoustic wave, gamma ray, etc.) (such as Schlumberger's logging-while-drilling acoustic tool) is also an effective means to obtain formation pore pressure in real time. However, the use cost of such technologies or tools is relatively high and they cannot be widely promoted and used on a large scale. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method, system, storage medium and computing device for evaluating formation pore pressure in view of the problems existing in the prior art.

[0005] To solve the above technical problem, the present invention provides a method for evaluating formation pore pressure, including:

[0006] Determining the equivalent drilling fluid density of bottomhole pressure under different working conditions;

[0007] Obtaining the gas logging values under different working conditions, and determining the range of equivalent drilling fluid density of formation pore pressure at the current measuring point according to the change trend of the gas logging values and the equivalent drilling fluid density of bottomhole pressure under different working conditions;

[0008] Determining the range of formation pore pressure at the current measuring point according to the range of equivalent drilling fluid density of formation pore pressure at the current measuring point.

[0009] To solve the above technical problem, the present invention also provides a system for evaluating formation pore pressure, including:

[0010] A parameter determination module for determining the equivalent drilling fluid density of bottomhole pressure under different working conditions;

[0011] An equivalent drilling fluid density determination module of formation pore pressure for obtaining the gas logging values under different working conditions and determining the range of equivalent drilling fluid density of formation pore pressure at the current measuring point according to the change trend of the gas logging values and the equivalent drilling fluid density of bottomhole pressure under different working conditions;

[0012] A formation pore pressure determination module, configured to determine the formation pore pressure range of the current measurement point according to the formation pore pressure equivalent drilling fluid density range of the current measurement point.

[0013] To solve the above technical problems, the present invention provides a computer-readable storage medium, including instructions, which when run on a computer, cause the computer to execute the formation pore pressure evaluation method provided by the above technical solution.

[0014] To solve the above technical problems, the present invention provides a computing device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, it implements the formation pore pressure evaluation method provided by the above technical solution.

[0015] The beneficial effects of the present invention are as follows: It is only necessary to determine the change trends of the bottom-hole pressure equivalent drilling fluid density and the gas logging value under different working conditions. According to the change trend of the gas logging value, the bottom-hole pressure difference under different working conditions can be determined. According to the positive or negative situation of the bottom-hole pressure difference and the corresponding bottom-hole pressure equivalent drilling fluid density, the formation pore pressure equivalent drilling fluid density range of the current measurement point can be determined, and further the formation pore pressure range of the current measurement point can be determined. This method does not need to rely on a prediction model and can realize formation pore pressure evaluation while drilling; moreover, it has the advantages of low cost and easy popularization and application, and can be used as a digital technology for monitoring and evaluating formation pore pressure while drilling and preventing downhole accidents in the future, supporting the development of future scientific and automated drilling technologies.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flowchart of the formation pore pressure evaluation method provided by an embodiment of the present invention;

[0018] Figure 2 It is a block diagram of the formation pore pressure evaluation system provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following describes the embodiments of the present disclosure through specific examples. Those skilled in the art can easily understand other advantages and effects of the present disclosure from the content disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of them. The present disclosure can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts belong to the scope of protection of the present disclosure.

[0020] It should be noted that the following describes various aspects of embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on the present disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functions in addition to one or more of the aspects described herein.

[0021] In the embodiment of the present invention, a comprehensive logging instrument is used to measure data such as well depth, bit position, weight on bit, rotary speed, torque, displacement, hook height, gas logging value, etc., to determine the current drilling working condition of the well section. At the same time, the equivalent drilling fluid density of the bottom hole pressure under different working conditions is calculated, and combined with the gas logging data under different working conditions and the calculated equivalent drilling fluid density of the bottom hole pressure, the monitoring and evaluation of the formation pore pressure are realized, which is applicable to the monitoring and evaluation of downhole working conditions during oil and gas well drilling and automated drilling operations.

[0022] Figure 1 It is a flow chart of the formation pore pressure evaluation method provided by the embodiment of the present invention. As Figure 1 shown, the method includes:

[0023] S1, determining the equivalent drilling fluid density of the bottom hole pressure under different working conditions.

[0024] Define the bottom hole pressure under different working conditions: According to whether the pump is on, whether the drill string is lifted, and whether the drill string is drilling and circulating, the bottom hole pressure is divided into the bottom hole pressure in the pump-off condition (i.e., the static condition, pump off and drill string stationary), the bottom hole pressure in the drill string lifting condition (pump off and drill string lifted), and the bottom hole pressure in the drilling and circulating condition.

[0025] Bottom hole pressure under pump-off condition: When the drill string is set in the slips and the pump is turned off, the bottom hole pressure at this time is the bottom hole pressure under pump-off condition. The equivalent static density of drilling fluid (ESD) under pump-off condition is equal to the actual density of drilling fluid:

[0026] ESD = ρ

[0027] Where ρ represents the density of drilling fluid in the current wellbore, g / cm 3 .

[0028] Bottom hole pressure during drilling and circulation condition: During normal drilling, the bottom hole pressure is equal to the hydrostatic pressure of the drilling fluid plus the circulation friction pressure. The equivalent static density of drilling fluid under this condition is equal to the equivalent circulating density of drilling fluid (ECD). The equivalent static density of drilling fluid (ECD) during drilling and circulation condition is expressed as follows:

[0029]

[0030]

[0031] Where ρ represents the density of drilling fluid in the current wellbore, g / cm 3 ; P f represents the pressure loss during drilling fluid circulation, Pa; TVD represents the vertical depth of the calculated section, m; i represents the number of sections from the bottom to the wellhead in the well section, dimensionless; N represents the total number of sections from the bottom to the wellhead, dimensionless; g represents the acceleration due to gravity, 9.8 m / s 2 ; f represents the friction coefficient between the drilling fluid and the wellbore, dimensionless; V represents the annular return velocity of the drilling fluid, m / s; L i represents the length of the i-th calculated section, m; d oi represents the wellbore diameter of the i-th calculated section, m; d i represents the outer diameter of the drill string in the i-th calculated section, m.

[0032] Bottom hole pressure during drill string pulling condition: After the pump is turned off, the drill string is lifted off the bottom hole at a certain speed. The bottom hole pressure at this time is the bottom hole pressure during drill string pulling condition. The bottom hole pressure at this time is equal to the hydrostatic pressure of the drilling fluid minus the swabbing pressure P swap , and the equivalent static density of drilling fluid (Swap) during drill string pulling condition is expressed as follows:

[0033]

[0034] P swap = p τ + p v + p a

[0035]

[0036]

[0037]

[0038] In the formula, ESD represents the equivalent density of drilling fluid at the bottom of the well under the pump-off condition, g / cm 3 ; P swap represents the swabbing pressure caused by the upward movement of the drill string, Pa; TVD represents the vertical depth of the calculated section, m; i represents the number of sections from the bottom of the well to the wellhead, dimensionless; N represents the total number of sections from the bottom of the well to the wellhead, dimensionless; g represents the acceleration due to gravity, 9.8 m / s 2 ; p τ represents the fluctuating pressure caused by the static shear force of the drilling fluid, Pa; p v represents the fluctuating pressure caused by the viscous force of the drilling fluid, Pa; p a represents the fluctuating pressure caused by the inertial force of the drill string, Pa; τ w represents the static shear stress of the drilling fluid, Pa; a represents the acceleration of the drill string movement, m / s 2 ; v represents the moving speed of the drill string, m / s; n represents the flow behavior index of the drilling fluid, dimensionless; K represents the consistency coefficient of the drilling fluid, Pa·sn; L i represents the length of the i-th calculated section, m; d oi represents the hole diameter of the i-th calculated section, m; d i represents the outer diameter of the drill string in the i-th calculated section, m.

[0039] Determine the equivalent density of drilling fluid at the bottom of the well under the pump-off condition, the upward movement condition of the drill string, and the drilling circulation condition; among them, the equivalent density of drilling fluid at the bottom of the well Swap under the upward movement condition of the drill string is less than the equivalent density of drilling fluid at the bottom of the well ESD under the pump-off condition, and the equivalent density of drilling fluid at the bottom of the well ESD under the pump-off condition is less than the equivalent density of drilling fluid at the bottom of the well ECD under the drilling circulation condition; that is, Swap < ESD < ECD.

[0040] S2. Obtain the gas logging values under different conditions, and determine the range of the equivalent density of formation pore pressure at the current measurement point according to the change trend of the gas logging values and the equivalent density of drilling fluid at the bottom of the well under different conditions.

[0041] S3. Determine the range of formation pore pressure at the current measurement point according to the range of the equivalent density of formation pore pressure at the current measurement point.

[0042] The corresponding formation pore pressure calculation formula is as follows:

[0043] P p = PP * TVD * 0.00981;

[0044] In the above formula, P p represents the formation pore pressure, with the unit of MPa; PP represents the equivalent density of formation pore pressure, with the unit of g / cm 3; TVD represents the vertical depth where the measurement point is located, with the unit of m.

[0045] In the embodiments of the present invention, it is only necessary to determine the changing trends of the equivalent drilling fluid density of the bottom-hole pressure and the gas logging value under different working conditions. According to the changing trend of the gas logging value, the bottom-hole pressure difference under different working conditions can be determined. According to the positive and negative conditions of the bottom-hole pressure difference and the corresponding equivalent drilling fluid density of the bottom-hole pressure, the range of the equivalent drilling fluid density of the formation pore pressure at the current measurement point can be determined, and then the range of the formation pore pressure at the current measurement point can be determined. This method does not need to rely on a prediction model and can realize the evaluation of the formation pore pressure while drilling; moreover, it has the advantages of low cost and easy popularization and application, and can be used as a digital technology for monitoring and evaluating the formation pore pressure while drilling and preventing downhole accidents in the future, supporting the development of future scientific and automated drilling technologies.

[0046] Optionally, determining the range of the equivalent drilling fluid density of the formation pore pressure at the current measurement point according to the changing trend of the gas logging value and the equivalent drilling fluid density of the bottom-hole pressure under different working conditions includes:

[0047] S21. Determine the positive and negative conditions of the bottom-hole pressure difference under different working conditions according to the changing trend of the gas logging value, where the bottom-hole pressure difference ΔP is the difference between the bottom-hole pressure BHP and the formation pore pressure P p That is, ΔP = BHP - P p .

[0048] Analysis of the bottom-hole pressure difference and the gas logging value: Under the drilling circulation working condition, when normally drilling through a large section of sandstone-shale and mud (shale) rock formations, due to the amount of gas dissolved in the drilling fluid by the bit crushing the rock, the gas logging value at this time is the background gas BG, and the background gas corresponds to the bottom-hole pressure difference ΔP circulate under the drilling circulation working condition. Under the condition of lifting the drill string, stopping the pump and lifting the drill string will cause the current bottom-hole pressure to decrease compared with the bottom-hole pressure under the drilling circulation working condition. The bottom-hole pressure difference under the condition of lifting the drill string is ΔP swap ; In this condition, if a gas logging value greater than the gas logging value of the background gas is observed, it is called the single-joint peak CG. Under the pump-stopping working condition (i.e., the static working condition), stopping the pump will cause the current bottom-hole pressure to decrease compared with the bottom-hole pressure under the drilling circulation working condition. The bottom-hole pressure difference under the pump-stopping working condition is ΔP static ; In this condition, if a gas logging value greater than the gas logging value of the background gas is observed, it is called the pump-stopping peak POG.

[0049] S22. Determine the range of the equivalent drilling fluid density of the formation pore pressure at the current measurement point according to the positive and negative conditions of the bottom-hole pressure difference under different working conditions and the equivalent drilling fluid density of the bottom-hole pressure under different working conditions.

[0050] In the embodiments of the present invention, the positive and negative conditions of the bottom-hole pressure difference under different working conditions are determined according to the changing trend of the gas logging value. The bottom-hole pressure difference under different working conditions reflects the magnitude relationship between the bottom-hole pressure and the formation pressure under different working conditions. That is to say, according to the positive and negative conditions of the bottom-hole pressure difference under different working conditions, the pressure range where the formation pore pressure is located can be determined. Furthermore, by obtaining the equivalent drilling fluid density of the bottom-hole pressure under different working conditions, the equivalent drilling fluid density range of the formation pore pressure at the current measurement point can be determined according to the positive and negative conditions of the bottom-hole pressure difference under different working conditions and the equivalent drilling fluid density of the bottom-hole pressure under different working conditions.

[0051] Optionally, in some embodiments, the evaluation method of the equivalent drilling fluid density of the formation pore pressure is as follows: When the equivalent drilling fluid density of the bottom-hole pressure under different working conditions satisfies Swap < ESD < ECD, according to the evaluation criterion of the equivalent drilling fluid density range of the formation pore pressure based on the change of the gas logging value:

[0052] 1. When the background gas BG remains unchanged, and there is no single-stand peak CG and no pump-off peak POG, it is determined that the bottom-hole pressure differences under the drilling circulation condition, the drill string lifting condition, and the pump-off condition are all positive pressure differences. Furthermore, it is determined that PP < Swap < ESD < ECD.

[0053] The fact that the background gas BG remains unchanged indicates that the amount of formation gas entering the wellbore under the drilling circulation condition remains unchanged. Therefore, the bottom-hole pressure difference under the drilling circulation condition is a positive pressure difference.

[0054] The absence of the single-stand peak CG indicates that the amount of formation gas entering the wellbore under the drill string lifting condition does not increase compared with that under the drilling circulation condition. Therefore, the bottom-hole pressure difference under the drill string lifting condition is also a positive pressure difference.

[0055] The absence of the pump-off peak POG indicates that the amount of formation gas entering the wellbore under the pump-off condition does not increase compared with that under the drilling circulation condition. Therefore, the bottom-hole pressure difference under the pump-off condition is also a positive pressure difference.

[0056] The bottom-hole pressure under the drilling circulation condition is greater than the bottom-hole pressure under the pump-off condition, the bottom-hole pressure under the pump-off condition is greater than the bottom-hole pressure under the drill string lifting condition, and the bottom-hole pressure differences under all three conditions are positive pressure differences. Therefore, the bottom-hole pressure under the drill string lifting condition is greater than the formation pore pressure, and the equivalent drilling fluid density Swap of the bottom-hole pressure under the drill string lifting condition > the equivalent drilling fluid density PP of the formation pore pressure.

[0057] 2. When the background gas BG remains unchanged, and there is a single-stand peak CG but no pump-off peak POG, it is determined that the bottom-hole pressure differences under the drilling circulation condition and the pump-off condition are positive pressure differences, and the bottom-hole pressure difference under the drill string lifting condition is a negative pressure difference. Furthermore, it is determined that Swap < PP < ESD < ECD;

[0058] The fact that the background gas BG remains unchanged indicates that the amount of formation gas entering the wellbore under the drilling circulation condition remains unchanged. Therefore, the bottom-hole pressure difference under the drilling circulation condition is a positive pressure difference.

[0059] The appearance of a single peak CG indicates that the amount of formation gas entering the wellbore under the condition of the drill string being lifted is increased compared to that under the drilling circulation condition. Therefore, the bottom-hole pressure difference is a negative pressure difference under the condition of the drill string being lifted.

[0060] The absence of a pump-off peak POG indicates that the amount of formation gas entering the wellbore under the pump-off condition is not increased compared to that under the drilling circulation condition. Therefore, the bottom-hole pressure difference is also a positive pressure difference under the pump-off condition.

[0061] The bottom-hole pressure under the drilling circulation condition is greater than the bottom-hole pressure under the pump-off condition, the bottom-hole pressure under the pump-off condition is greater than the bottom-hole pressure under the condition of the drill string being lifted, and the bottom-hole pressure difference under the drilling circulation and pump-off conditions is a positive pressure difference, while it is a negative pressure difference under the condition of the drill string being lifted. Therefore, the bottom-hole pressure under the condition of the drill string being lifted is less than the formation pore pressure, and the bottom-hole pressure under the pump-off condition is greater than the formation pore pressure; the equivalent drilling fluid density Swap < the equivalent drilling fluid density of the formation pore pressure PP < the equivalent drilling fluid density ESD under the pump-off condition.

[0062] 3. When the background gas BG remains unchanged and there appear a pump-off peak POG and a single peak CG, it is determined that the bottom-hole pressure difference under the drilling circulation condition is a positive pressure difference, and the bottom-hole pressure differences under the pump-off and drill string lifting conditions are negative pressure differences. Furthermore, Swap < ESD < PP < ECD is determined.

[0063] The unchanged background gas BG indicates that the amount of formation gas entering the wellbore under the drilling circulation condition remains unchanged. Therefore, the bottom-hole pressure difference under the drilling circulation condition is a positive pressure difference.

[0064] The appearance of a single peak CG indicates that the amount of formation gas entering the wellbore under the condition of the drill string being lifted is increased compared to that under the drilling circulation condition. Therefore, the bottom-hole pressure difference under the condition of the drill string being lifted is a negative pressure difference.

[0065] The appearance of a pump-off peak POG indicates that the amount of formation gas entering the wellbore under the pump-off condition is increased compared to that under the drilling circulation condition. Therefore, the bottom-hole pressure difference under the pump-off condition is a negative pressure difference.

[0066] The bottom-hole pressure under the drilling circulation condition is greater than the bottom-hole pressure under the pump-off condition, the bottom-hole pressure under the pump-off condition is greater than the bottom-hole pressure under the condition of the drill string being lifted, and the bottom-hole pressure difference under the drilling circulation condition is a positive pressure difference, while the bottom-hole pressure differences under the drill string lifting and pump-off conditions are negative pressure differences. Therefore, the bottom-hole pressure under the pump-off condition is less than the formation pore pressure, and the bottom-hole pressure under the drilling circulation condition is greater than the formation pore pressure; the equivalent drilling fluid density ESD under the pump-off condition < the equivalent drilling fluid density of the formation pore pressure PP < the equivalent drilling fluid density ECD under the drilling circulation condition.

[0067] 4. When the background gas BG increases by more than a preset value compared to the initial value (e.g., increases by more than 5% compared to the initial value), and a single peak CG and / or a pump-off peak POG appear, it is determined that the bottom-hole pressure differences under the drilling circulation condition, the drill string pulling condition, and the pump-off condition are all negative pressure differences, and the formation pore pressure is of the same order of magnitude as the bottom-hole pressure under the drilling circulation condition (i.e., the difference between the formation pore pressure and the bottom-hole pressure under the drilling circulation condition is not very large), and then it is determined that Swap < ESD < ECD < PP.

[0068] The increase in the background gas BG indicates an increase in the amount of formation gas entering the wellbore under the drilling circulation condition. Therefore, the bottom-hole pressure difference under the drilling circulation condition is a negative pressure difference. Since the bottom-hole pressure under the drilling circulation condition is greater than the bottom-hole pressure under the pump-off condition, and the bottom-hole pressure under the pump-off condition is greater than the bottom-hole pressure under the drill string pulling condition, when the bottom-hole pressure difference under the drilling circulation condition is a negative pressure difference, it can be known that the bottom-hole pressure differences under the pump-off condition and the drill string pulling condition are also negative pressure differences.

[0069] Since a single peak CG and / or a pump-off peak POG appear, it indicates that the gas logging values under the drill string pulling condition and the pump-off condition are quite different from the gas logging value under the drilling circulation condition, resulting in the peak value of the single peak CG and / or the peak value of the pump-off peak POG being recognizable. It can be inferred that the pressure difference reduction caused by pump-off and drill string pulling leads to more formation gas flowing into the wellbore under the pump-off and drill string pulling conditions than under the drilling circulation condition or a relatively large increase in the amount of formation gas flowing into the wellbore under the pump-off and drill string pulling conditions compared to the drilling circulation condition. Therefore, it can be determined that the formation pore pressure is greater than the bottom-hole pressure under the drilling circulation condition, that is, the equivalent mud density of the bottom-hole pressure under the drilling circulation condition ECD < the equivalent mud density of the formation pore pressure PP.

[0070] 5. When the background gas BG increases to a preset multiple of the initial value (e.g., increases to 2 times the initial value), and no single peak CG and pump-off peak POG appear, it is determined that the bottom-hole pressure differences under the drilling circulation condition, the drill string pulling condition, and the pump-off condition are all negative pressure differences, and the formation pore pressure is much greater than the bottom-hole pressure under the drilling circulation condition, and then it is determined that Swap < ESD < ECD << PP.

[0071] The background gas BG increasing to a preset multiple of the initial value indicates an increase in the amount of formation gas entering the wellbore under the drilling circulation condition. Therefore, the bottom-hole pressure difference under the drilling circulation condition is a negative pressure difference. Since the bottom-hole pressure under the drilling circulation condition is greater than the bottom-hole pressure under the pump-off condition, and the bottom-hole pressure under the pump-off condition is greater than the bottom-hole pressure under the drill string pulling condition, when the bottom-hole pressure difference under the drilling circulation condition is a negative pressure difference, it can be known that the bottom-hole pressure differences under the pump-off condition and the drill string pulling condition are also negative pressure differences.

[0072] Since there is no single - peak CG and pump - off peak POG, it indicates that the gas logging values under the conditions of lifting the drill string and stopping the pump are not much different from those under the drilling and circulation conditions. As a result, the peak values of the single - peak CG and the pump - off peak POG cannot be identified. It can be inferred that the decrease in differential pressure caused by stopping the pump and lifting the drill string does not lead to more formation gas flowing into the wellbore under the conditions of stopping the pump and lifting the drill string compared with the drilling and circulation conditions, or the increase in the amount of formation gas flowing into the wellbore under the conditions of stopping the pump and lifting the drill string compared with the drilling and circulation conditions is very small. Therefore, it can be determined that the formation pore pressure is much greater than the bottom - hole pressure under the drilling and circulation conditions, that is, the equivalent circulating density ECD of the bottom - hole pressure under the drilling and circulation conditions << the equivalent pore - pressure density PP of the formation.

[0073] 6. If the total hydrocarbon value of gas logging (including background gas BG, single - peak CG, and pump - off peak POG) decreases after increasing the ECD by increasing the drilling fluid density or displacement, it is determined that the bottom - hole differential pressure under the drilling and circulation conditions, the drill - string lifting conditions, and the pump - off conditions is a negative differential pressure, and the formation pore pressure is greater than the bottom - hole pressure under the drilling and circulation conditions. Furthermore, it is determined that PP > ECD. If the total hydrocarbon value of gas logging remains unchanged, it is determined that the bottom - hole differential pressure under the drilling and circulation conditions is zero, and then it is determined that PP = ECD.

[0074] In the embodiment of the present invention, the positive and negative conditions of the bottom - hole differential pressure under different conditions are determined according to the change trend of the gas logging value. The bottom - hole differential pressure under different conditions reflects the magnitude relationship between the bottom - hole pressure and the formation pressure under different conditions. That is to say, according to the positive and negative conditions of the bottom - hole differential pressure under different conditions, the pressure range of the formation pore pressure can be determined. The equivalent circulating density of the bottom - hole pressure under different conditions is relatively easy to obtain. Therefore, the equivalent pore - pressure density range of the formation at the current measurement point can be determined according to the positive and negative conditions of the bottom - hole differential pressure under different conditions and the equivalent circulating density of the bottom - hole pressure under different conditions. The embodiment of the present invention can calculate and evaluate the formation pore pressure in real - time based on the measured parameters, predict the high - pressure water layer, assist in optimizing the drilling fluid density, optimizing the wellbore structure design, and preventing down - hole accidents and complications such as well kick, lost circulation, and differential - pressure sticking.

[0075] Another embodiment of the present invention provides a method for evaluating formation pore pressure, including the following steps:

[0076] Step 1: Define the bottom - hole pressure under different conditions: According to whether the pump is on, whether the drill string is lifted, and whether the drill string is in drilling circulation, the bottom - hole pressure is divided into the bottom - hole pressure under the pump - off condition (i.e., the static condition, pump off and drill string stationary), the bottom - hole pressure under the drill - string lifting condition (pump off and drill string lifted), and the bottom - hole pressure under the drilling and circulation condition;

[0077] Step 2: Bottom - hole pressure under the pump - off condition (pump off and drill string stationary): When the drill string is set in the slips and the pump is stopped, the bottom - hole pressure at this time is the bottom - hole pressure under the pump - off condition. The equivalent circulating density ESD of the bottom - hole pressure under this condition is equal to the actual drilling fluid density:

[0078] ESD = ρ

[0079] Where ρ represents the density of the current wellbore drilling fluid, g / cm 3 .

[0080] Step 3: Bottom hole pressure under the drilling circulation condition: During normal drilling, the bottom hole pressure is equal to the hydrostatic pressure of the drilling fluid plus the circulation friction pressure. Under this condition, the equivalent density of the drilling fluid at the bottom hole is equal to the equivalent circulating density of the drilling fluid ECD. The equivalent density of the drilling fluid at the bottom hole ECD is expressed as follows:

[0081]

[0082]

[0083] Where ρ represents the density of the current drilling fluid, g / cm 3 ; P f represents the pressure loss of the drilling fluid circulation, Pa; TVD represents the vertical depth of the calculated section, m; i represents the number of sections from the bottom hole to the wellhead, dimensionless; N represents the total number of sections from the bottom hole to the wellhead, dimensionless; g represents the acceleration due to gravity, 9.8 m / s 2 ; f represents the friction coefficient between the drilling fluid and the wellbore, dimensionless; V represents the return velocity of the drilling fluid in the annulus, m / s; L i represents the length of the i-th calculated section, m; d oi represents the wellbore diameter of the i-th calculated section, m; d i represents the outer diameter of the drill string in the i-th calculated section, m.

[0084] Step 4: Bottom hole pressure under the drill string lifting condition: After stopping the pump, the drill string is lifted off the bottom hole at a certain speed. At this time, the bottom hole pressure is the bottom hole pressure under the drill string lifting condition. At this time, the bottom hole pressure is equal to the hydrostatic pressure of the drilling fluid minus the swabbing pressure P swap , and the equivalent density of the drilling fluid at the bottom hole Swap under the drill string lifting condition is expressed as follows:

[0085]

[0086] P swap = p τ + p v + p a

[0087]

[0088]

[0089]

[0090] where ESD represents the equivalent mud density at the bottom hole under the pump-off condition, g / cm 3 ; P swap represents the swabbing pressure caused by pulling up the drill string, Pa; TVD represents the vertical depth of the calculated interval, m; i represents the number of intervals from the bottom hole to the wellhead, dimensionless; N represents the total number of intervals from the bottom hole to the wellhead, dimensionless; g represents the acceleration due to gravity, 9.8 m / s 2 ; p τ represents the fluctuating pressure caused by the static shear force of the drilling fluid, Pa; p v represents the fluctuating pressure caused by the viscous force of the drilling fluid, Pa; p a represents the fluctuating pressure caused by the inertial force of the drill string, Pa; τ w represents the static shear stress of the drilling fluid, Pa; a represents the acceleration of the drill string movement, m / s 2 ; v represents the movement speed of the drill string, m / s; n represents the flow behavior index of the drilling fluid, dimensionless; K represents the consistency coefficient of the drilling fluid, Pa·sn; L i represents the length of the i-th calculated interval, m; d oi represents the hole diameter of the i-th calculated interval, m; d i represents the outer diameter of the drill string in the i-th calculated interval, m.

[0091] Step 5: Analysis of bottom hole pressure differential and gas value: Define the bottom hole pressure differential as the difference between the bottom hole pressure and the formation pore pressure, i.e., ΔP = BHP - P p is the bottom hole pressure differential, and define the equivalent mud density of the formation pore pressure PP.

[0092] Under the drilling and circulating condition, when drilling through a long section of sandstone-shale or shale formation during normal drilling, due to the amount of gas dissolved in the drilling fluid by the bit crushing the rock, the gas logging value at this time is the background gas BG, and the background gas corresponds to the bottom hole pressure differential ΔP circulate under the drilling and circulating condition. Under the condition of pulling up the drill string, stopping the pump and pulling up the drill string will cause the bottom hole pressure to decrease compared with the bottom hole pressure under the drilling and circulating condition. At this time, the bottom hole pressure differential is ΔP swap , and the gas logging value greater than the background gas value observed under this condition is called the single joint peak CG. Under the pump-off condition, stopping the pump will cause the bottom hole pressure under the pump-off condition to decrease compared with the bottom hole pressure under the drilling and circulating condition. At this time, the bottom hole pressure differential is ΔP static , and the gas logging value greater than the background gas value observed under this condition is called the pump-off peak POG.

[0093] Step 6: Evaluation of formation pore pressure: If the equivalent mud density at the bottom hole under different conditions satisfies Swap < ESD < ECD, then according to the formation pore pressure evaluation criterion based on the change of gas logging value, there are:

[0094] ①When the background gas BG remains unchanged, there is no single peak CG and no pump shutdown peak POG, then PP < Swap < ESD < ECD;

[0095] ②When the background gas BG remains unchanged and a single peak CG appears but there is no pump shutdown peak POG, then Swap < PP < ESD < ECD;

[0096] ③When the background gas BG remains unchanged and a pump shutdown peak POG and a single peak CG appear, then Swap < ESD < PP < ECD;

[0097] ④When the background gas BG increases by 5% compared to the initial value and a single peak CG and / or a pump shutdown peak POG appear, then Swap < ESD < ECD < PP;

[0098] ⑤When the background gas BG increases to twice the initial value and no single peak CG and no pump shutdown peak POG appear, then at this time Swap < ESD < ECD << PP;

[0099] ⑥If after increasing the ECD by increasing the drilling fluid density or displacement, the gas logging total hydrocarbon value (including the background gas BG, single peak CG, and pump shutdown peak POG) decreases, then PP > ECD. If the total hydrocarbon value remains unchanged, at this time PP = ECD.

[0100] The corresponding formation pore pressure calculation method:

[0101] P p = PP * TVD * 0.00981

[0102] In the above formula, P p represents the formation pore pressure, with the unit of MPa; PP represents the equivalent drilling fluid density of the formation pore pressure (formation pore pressure gradient), with the unit of g / cm 3 ; TVD represents the vertical depth where the measurement point is located, with the unit of m.

[0103] It should be noted that in the embodiments of the present invention, the execution order of the above steps 2-4 is not limited.

[0104] The embodiments of the present invention can calculate and evaluate the formation pore pressure in real time based on measurement parameters, predict high-pressure water layers, and assist in optimizing the drilling fluid density, optimizing the wellbore structure design, and preventing downhole accidents and complexities such as well kicks, lost circulation, and differential sticking.

[0105] As Figure 2 shown, the embodiments of the present invention also provide a formation pore pressure evaluation system, including:

[0106] A parameter determination module for determining the equivalent drilling fluid density of the bottom hole pressure under different working conditions;

[0107] The formation pore pressure equivalent drilling fluid density determination module is used to obtain gas logging values under different working conditions, and determine the formation pore pressure equivalent drilling fluid density range of the current measurement point according to the change trend of the gas logging values and the bottom hole pressure equivalent drilling fluid density under different working conditions;

[0108] The formation pore pressure determination module is used to determine the formation pore pressure range of the current measurement point according to the formation pore pressure equivalent drilling fluid density range of the current measurement point.

[0109] An embodiment of the present invention also provides a computer-readable storage medium, including instructions, when the instructions run on a computer, the computer is caused to execute the formation pore pressure evaluation method provided in the above embodiment.

[0110] An embodiment of the present invention also provides a computing device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, it implements the formation pore pressure evaluation method provided in the above embodiment.

[0111] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes of the above-described devices and units can refer to the corresponding processes in the foregoing method embodiments, and will not be described herein again.

[0112] In several embodiments provided by the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of units is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0113] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment of the present invention.

[0114] In addition, each functional unit in various embodiments of the present invention can be integrated in one processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated units can be implemented in the form of hardware or in the form of software functional units.

[0115] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in various embodiments of the present invention. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs that can store program codes.

[0116] The foregoing are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for evaluating formation pore pressure, characterized in that Including: Determine the equivalent mud density for bottom hole pressure under different working conditions; The determination of the equivalent mud density for bottom hole pressure under different working conditions includes: determining the equivalent mud density for bottom hole pressure ESD under the pump-off condition, the equivalent mud density for bottom hole pressure Swap under the drill string lifting condition, and the equivalent mud density for bottom hole pressure ECD under the drilling and circulation condition; where Swap < ESD < ECD; Obtain the gas logging values under different working conditions, and determine the equivalent mud density range of the formation pore pressure at the current measuring point according to the change trend of the gas logging values and the equivalent mud density of the bottom hole pressure under different working conditions; The determination of the equivalent mud density range of the formation pore pressure at the current measuring point according to the change trend of the gas logging values and the equivalent mud density of the bottom hole pressure under different working conditions includes: Determine the positive and negative conditions of the bottom hole pressure difference under different working conditions according to the change trend of the gas logging values, where the bottom hole pressure difference is the difference between the bottom hole pressure and the formation pore pressure; Determine the equivalent mud density range of the formation pore pressure at the current measuring point according to the positive and negative conditions of the bottom hole pressure difference under different working conditions and the equivalent mud density of the bottom hole pressure under different working conditions; The determination of the equivalent mud density range of the formation pore pressure at the current measuring point according to the positive and negative conditions of the bottom hole pressure difference under different working conditions and the equivalent mud density of the bottom hole pressure under different working conditions includes: When the background gas BG remains unchanged, and there is no single joint peak CG and no pump-off peak POG, it is determined that the bottom hole pressure differences under the drilling and circulation condition, the drill string lifting condition, and the pump-off condition are all positive pressure differences, and then it is determined that PP < Swap < ESD < ECD; When the background gas BG remains unchanged, and there is a single joint peak CG but no pump-off peak POG, it is determined that the bottom hole pressure differences under the drilling and circulation condition and the pump-off condition are positive pressure differences, and the bottom hole pressure difference under the drill string lifting condition is a negative pressure difference, and then it is determined that Swap < PP < ESD < ECD; When the background gas BG remains unchanged, and there are a pump-off peak POG and a single joint peak CG, it is determined that the bottom hole pressure difference under the drilling and circulation condition is a positive pressure difference, and the bottom hole pressure differences under the pump-off condition and the drill string lifting condition are negative pressure differences, and then it is determined that Swap < ESD < PP < ECD; Wherein, PP is the equivalent mud density of the formation pore pressure, the gas logging value obtained under the drilling and circulation condition is called the background gas BG; the gas logging value observed to be greater than the background gas logging value under the drill string lifting condition is called the single joint peak CG, and the gas logging value observed to be greater than the background gas logging value under the pump-off condition is called the pump-off peak POG; Determine the formation pore pressure range of the current measuring point according to the equivalent mud density range of the formation pore pressure at the current measuring point; The corresponding formation pore pressure calculation formula is as follows: P p = PP * TVD * 0.00981; In the above formula, P p represents the formation pore pressure, with the unit of MPa; PP represents the equivalent drilling fluid density of the formation pore pressure, with the unit of g / cm 3 ; TVD represents the vertical depth where the measurement point is located, with the unit of m.

2. The method according to claim 1, characterized in that The determination of the equivalent mud density range of the formation pore pressure at the current measuring point according to the positive and negative conditions of the bottom hole pressure difference under different working conditions and the equivalent mud density of the bottom hole pressure under different working conditions further includes: When the background gas BG increases by more than a preset value compared to the initial value, and a single peak CG and / or a pump shutdown peak POG appear, it is determined that the bottomhole pressure differences under the drilling circulation condition, the drill string pulling-up condition, and the pump shutdown condition are all negative pressure differences, and the formation pore pressure is greater than the bottomhole pressure under the drilling circulation condition. Furthermore, it is determined that Swap < ESD < ECD < PP.

3. The method according to claim 1, characterized in that, The method for determining the formation pore pressure equivalent mud density range of the current measurement point according to the positive or negative conditions of the bottomhole pressure differences under different conditions and the equivalent mud densities of the bottomhole pressures under different conditions further includes: When the background gas BG increases to a preset multiple of the initial value and neither a single peak CG nor a pump shutdown peak POG appears, it is determined that the bottomhole pressure differences under the drilling circulation condition, the drill string pulling-up condition, and the pump shutdown condition are all negative pressure differences, and the formation pore pressure is much greater than the bottomhole pressure under the drilling circulation condition. Furthermore, it is determined that Swap < ESD < ECD << PP.

4. The method according to claim 1, characterized in that, The method for determining the formation pore pressure equivalent mud density range of the current measurement point according to the positive or negative conditions of the bottomhole pressure differences under different conditions and the equivalent mud densities of the bottomhole pressures under different conditions further includes: If the gas logging total hydrocarbon value decreases after increasing the equivalent mud density of the bottomhole pressure ECD under the drilling circulation condition by increasing the mud density or displacement, it is determined that the bottomhole pressure differences under the drilling circulation condition, the drill string pulling-up condition, and the pump shutdown condition are all negative pressure differences, and the formation pore pressure is greater than the bottomhole pressure under the drilling circulation condition. Furthermore, it is determined that PP > ECD. If the gas logging total hydrocarbon value remains unchanged, it is determined that the bottomhole pressure difference under the drilling circulation condition is zero, and further it is determined that PP = ECD.

5. A formation pore pressure evaluation system, characterized in that, A system for implementing the formation pore pressure evaluation method according to any one of claims 1 to 4, the system includes: A parameter determination module for determining the equivalent mud density of the bottomhole pressure under different conditions; A formation pore pressure equivalent mud density determination module for obtaining the gas logging values under different conditions and determining the formation pore pressure equivalent mud density range of the current measurement point according to the change trend of the gas logging values and the equivalent mud density of the bottomhole pressure under different conditions; A formation pore pressure determination module for determining the formation pore pressure range of the current measurement point according to the formation pore pressure equivalent mud density range of the current measurement point.

6. A computer-readable storage medium, comprising instructions, characterized in that, When the instruction runs on a computer, the computer is caused to execute the formation pore pressure evaluation method according to any one of claims 1 to 4.

7. A computing device, comprising: A memory, a processor, and a computer program stored on the memory and executable on the processor, wherein when the processor executes the program, the formation pore pressure evaluation method according to any one of claims 1 to 4 is implemented.

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