Drilling formation pressure profile prediction method

Abstract

The invention provides a well drilling formation pressure profile prediction method, which comprises the following steps of: 1, researching a regional pressure distribution rule, and analyzing a reason for generating abnormal pressure; step 2, selecting a proper reference well; 3, selecting a proper pressure prediction method model according to the abnormal pressure cause determined in the step 1; 4, a proper method is selected to establish a mudstone velocity model, and a formation pressure curve is generated; and step 5, adjusting additional coefficients and related parameters according to different geological conditions, and generating a final formation pressure prediction curve. According to the drilling formation pressure profile prediction method, the accuracy of formation pressure prediction can be improved, a reliable basis is provided for reasonably designing the drilling fluid density and optimizing a well body structure, on-site drilling fluid density use is guided, and technical guarantee is provided for safe and efficient operation of drilling engineering and oil and gas discovery.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration and development, and in particular to a method for predicting a drilling formation pressure profile. Background Art

[0002] The formation pressure prediction profile is one of the necessary data for drilling geological design, and is of great significance for optimizing wellbore structure and drilling fluid selection. In particular, the existence of abnormal deep pressure increases the risk and cost of oil and gas exploration and development. Therefore, the prediction of formation pressure profile before drilling begins is a very important task in the oil and gas exploration process.

[0003] There are many methods to calculate formation pressure. In the early exploration stage, the velocity profile of seismic data is generally used to analyze and predict formation pressure in areas without drilling. After a certain amount of drilling, the formation pressure profile of the designed well is predicted through the adjacent drilling engineering parameters and logging and logging data. Compared with the calculation of formation pressure by seismic wave velocity, the formation pressure prediction method based on logging data can more accurately obtain the distribution of single well formation pressure and better predict the formation pressure characteristics of the study area. It is currently the most commonly used prediction method. However, there are also some problems. For example, the prediction method based on logging data is to select the prediction of the design well based on the well. Whether there is a suitable well is an important prerequisite for accurate prediction; the accuracy and completeness of the data affect the prediction results. For example, collapse pressure is difficult to calculate and use on a large scale because data is not easy to obtain; there are many methods for calculating formation pressure, such as the equilibrium depth method, Eaton method, Bowers method, etc., and it is necessary to select the appropriate method to establish a model to obtain the correct prediction results; there are many parameter adjustments and human factors. In field operations, a certain calculation software is generally used to use a single method for prediction. If no correction is made, the results often have large errors.

[0004] In the Chinese patent application with patent number: CN115807664B, a method for constructing an abnormal pressure prediction model is involved. This method predicts the abnormal pore pressure formed by undercompaction and vertical structural action by applying the pore pressure predicted by the corrected Eaton method to a single well by establishing the relationship between the amount of structural supercharging and depth; on the basis of the calculated undercompaction pore pressure, a structural supercharging model is established for the structural supercharging section, and the measured pore pressure is used for quality control to obtain the well point structural coefficient; and then, by establishing the pore pressure body of the work area, the pore pressure can be predicted with high accuracy, providing guidance for the design of well depth structure and mud density. The method described in this patent is suitable for the prediction of abnormal pore pressure caused by structural supercharging, but not for the prediction of abnormal pore pressure caused by other causes such as hydrocarbon generation supercharging. In addition, when the Eaton method is used to calculate the formation pore pressure, the slope and intercept of the compaction trend line have a greater impact on it, while the influence of the Eaton index increases with the increase of the abnormal degree of pore pressure. Therefore, in abnormally high-pressure layers, the n index needs to be optimized in combination with previous actual drilling and measurement data. This patent does not consider the problem of parameter selection, and does not consider the impact of the selection of key basis wells on the prediction effect. The final prediction results are not corrected according to the geological conditions, and the prediction effect is not ideal.

[0005] In the Chinese patent application with patent number: CN110069751B, a method for predicting pore pressure in non-undercompacted formations is involved. On-site drilling is used to establish a longitudinal wave velocity and density intersection diagram. According to the mudstones at different depths of on-site drilling, the velocity and density intersection points of these mudstones are established in the longitudinal wave velocity and density intersection diagram. Then, the velocity and density intersection points that deviate from the loading trend line are compared with the classical pressure unloading model. The cause of abnormal pressure in non-undercompacted formations is judged by comparison. The pore pressure of mudstones at different depths is calculated using the formation velocity. The pressure coefficient error between the calculated mudstone pore pressure and the measured mudstone pore pressure is statistically calculated. The formation depth and the pressure coefficient error are used to establish a fitting function. The mudstone pore pressure obtained by the fitting function and the obtained mudstone pore pressure are used to realize the prediction of pore pressure in non-undercompacted formations. The beneficial effects of the invention are: the prediction of pore pressure in non-undercompacted formations is realized, and the qualitative judgment of the cause of abnormal pressure in non-undercompacted formations is realized. The method described in this patent is suitable for the prediction of abnormal pore pressure that is not undercompacted, but is not suitable for the prediction of abnormal pore pressure caused by other reasons such as structural supercharging. It also does not consider the impact of the selection of key wells on the prediction effect, and the prediction results are not corrected according to the geological conditions, which often results in large errors.

[0006] In the Chinese patent application with patent number: CN108875109B, a prediction method for abnormal formation pressure is involved, including sorting abnormal formation pressure data; analyzing the logging response characteristics of abnormal formation pressure data; establishing a formation pressure calculation model through the logging response characteristics; and measuring the formation pressure data using the formation pressure calculation model. By statistically analyzing the abnormal formation pressure data measured by drilling, and analyzing the response characteristics of each logging curve, then selecting the logging curve with good correlation with the abnormal formation pressure data to construct an abnormal pressure identification factor model, and further combining the measured formation pressure data to obtain a new formation pressure calculation formula, finally, using geophysical inversion based on pre-stack and post-stack seismic data to obtain each parameter data body in the formula, these parameter data bodies are substituted into the new formation pressure calculation formula to obtain the formation pressure data body, thereby obtaining the spatial distribution characteristics of the formation pressure, which is conducive to the exploration and development of abnormal pressure oil and gas reservoirs. The method described in this patent does not take into account the impact of different causes of abnormal pressure and different lithologies on the method model, nor does it select key reference wells for quality control or make corrections based on different geological causes. Its prediction results often have very large errors.

[0007] The above existing technologies are all significantly different from the present invention. Through searching, it can be seen that there is no XY document, and the present invention is innovative. Since there is no solution to the technical problem we want to solve in the existing technology, we have invented a new method for predicting the drilling formation pressure profile. Summary of the invention

[0008] The purpose of the present invention is to provide a drilling formation pressure profile prediction method which predicts the formation pressure profile by steps such as prediction method selection, well optimization, empirical coefficient N value determination and geological parameter correction, thereby improving the prediction accuracy.

[0009] The object of the present invention can be achieved by the following technical measures: a method for predicting a drilling formation pressure profile, the method comprising:

[0010] Step 1: Study the regional pressure distribution law and analyze the causes of abnormal pressure;

[0011] Step 2, select a suitable basis well;

[0012] Step 3, selecting a suitable pressure prediction method model according to the abnormal pressure cause determined in step 1;

[0013] Step 4, select a suitable method to establish a mudstone velocity model and generate a formation pressure curve;

[0014] Step 5: Adjust the additional coefficients and related parameters according to different geological conditions to generate the final formation pressure prediction curve.

[0015] The purpose of the present invention can also be achieved by the following technical measures:

[0016] In step 1, the formation pressure distribution law in the study area where the drilling is located is studied, the distribution areas and layers where abnormal formation pressure may appear are analyzed, and a comprehensive geological analysis is carried out to determine the cause of abnormal pressure.

[0017] In step 1, the formation pressure distribution law of the study area includes the plane distribution law of the main layer segments, the vertical distribution law and the distribution law of each layer segment; the data required to study the formation pressure distribution include regional geological data, drilling data, seismic data, logging data, well logging data, pressure test data, oil test and production test data, etc.

[0018] In step 2, the selection of the reference well is mainly based on the comparative analysis of the geological characteristics of the well location, structural position, rock type, the presence or absence of measured pressure data and fracture development conditions, and the drilled well with the highest similarity to the geological conditions of the designed well is selected as the reference well; on the basis of the optimization of the reference well, an auxiliary correction well can also be selected.

[0019] In step 3, according to the principles of commonly used formation pressure prediction methods, the normal trend line method, including the equivalent depth method or the Eaton formula method, should be used to predict the under-compacted formation pressure profile; the mudstone acoustic wave velocity method, including the Bowers method, should be used to predict the overpressure formation pressure profile due to fluid pressurization and pressure transmission mechanisms.

[0020] In step 3, when the Eaton method is used to predict the formation pressure profile, in the abnormally high-pressure layer, N, namely the Eaton index, should be optimized according to the specific conditions of the region and geological age; the approximate range of the N index is determined by parameter regression of some abnormally high-pressure wells in the study area and combined with measured data, and the middle value is taken as the preferred N index result for the area.

[0021] In step 4, according to the method selected in step 3, the required raw data are collected to predict the formation pressure, including data preprocessing, calculation of the overlying formation pressure gradient, and determination of mudstone logging parameters. In combination with the pressure genesis, an appropriate method is selected to establish a mudstone velocity model and generate a formation pressure curve.

[0022] In step 4, the original data include the logging density, wellbore diameter, acoustic wave time difference, density, resistivity, natural gamma, shear wave time difference, basic formation stratification data, gamma base value stratification depth, segmented drill bit data, mud density, cuttings logging lithology, measured formation pressure, N index and pore pressure gradient PPG, fracture pressure gradient FPG, collapse pressure gradient CPG range, and normal compaction depth range.

[0023] In step 5, different geological conditions and parameter adjustments can be carried out according to the following principles: if there is regional pressure anomaly, it is necessary to deeply analyze the cause of abnormal pressure, select the reference well, select the appropriate method model, and make adjustments based on various factors; if the pressure difference in the same layer of adjacent well areas is large, it is necessary to analyze the cause of the pressure difference, clarify the regional pressure change, and re-select the reference well reasonably; if the adjacent well drills the target layer of the designed well, but the structural position is quite different, it is necessary to combine the specific data of the drilled well, and use the prediction of the reference well logging curve to reduce or increase a certain coefficient based on experience for correction; if the adjacent well is not drilled into the target layer, based on the distance between the well and the current well, it is necessary to combine the seismic profile, analyze the structural and sedimentary characteristics, and combine the actual drilling situation of the drilled well to analyze the pressure change characteristics, and finally form a predicted profile through inversion and splicing of the logging curves of multiple wells.

[0024] The purpose of the present invention can also be achieved through the following technical measures: a drilling formation pressure profile prediction system, which uses a drilling formation pressure profile prediction method to generate a formation pressure prediction curve to predict the drilling formation pressure profile.

[0025] The drilling formation pressure profile prediction method of the present invention first studies the regional pressure distribution law through geological, drilling, seismic, logging, testing and other data, analyzes the causes of abnormal pressure, selects a suitable calculation basis well according to the causes of abnormal pressure, and optimizes the prediction method. On this basis, after data preprocessing, overburden pressure gradient calculation, mudstone logging parameter acquisition and other steps, combined with the pressure causes, a suitable method is selected to establish a mudstone velocity model, generate a formation pressure curve, and finally, according to different geological conditions, adjust the additional coefficients and related parameters to generate the final formation pressure prediction curve. The invention can greatly improve the accuracy of drilling pressure prediction results by using the drilling formation pressure profile prediction method and process based on the analysis of the causes of pressure, including the steps of basis well selection, method optimization, mudstone velocity model optimization, and correction of additional coefficients and related parameters according to geological conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flowchart of a specific embodiment of the method for predicting a drilling formation pressure profile of the present invention;

[0027] Figure 2 A schematic diagram of the pressure plane distribution law of a certain stratum in a certain area according to an embodiment of the present invention;

[0028] Figure 3 A schematic diagram of the vertical distribution law of the formation pressure coefficient in a certain area according to an embodiment of the present invention;

[0029] Figure 4 It is a schematic diagram of a predicted formation pressure profile of a well according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0032] The drilling formation pressure profile prediction method of the present invention comprises:

[0033] Step 1: Study the distribution law of formation pressure in the study area where the well is located, analyze the distribution areas and layers where abnormal formation pressure may appear, and determine the cause of abnormal pressure.

[0034] Step 2: Select the appropriate reference well.

[0035] Step 3, according to the abnormal pressure cause determined in step 1, select the appropriate pressure prediction method model. The normal trend line method, such as the equivalent depth method or the Eaton formula method, should be used to predict the pressure profile of under-compacted formations; the mudstone acoustic wave velocity method, such as the Bowers method, should be used to predict the pressure profile of overpressure formations with multiple genetic mechanisms such as fluid pressurization and pressure transmission.

[0036] Step 4, according to the method selected in step 3, collect the required raw data and predict the formation pressure, including data preprocessing, calculating the pressure gradient of the overlying formation, obtaining mudstone logging parameters, combining the pressure genesis, selecting a suitable method to establish a mudstone velocity model, and generating a formation pressure curve.

[0037] Step 5: Adjust the additional coefficients and related parameters according to different geological conditions to generate the final formation pressure prediction curve.

[0038] The present invention provides a method and process for predicting the drilling formation pressure profile by combining multiple means based on geological feature analysis, which can improve the accuracy of formation pressure prediction, provide a reliable basis for the reasonable design of drilling fluid density and optimization of wellbore structure, guide the use of drilling fluid density on site, and provide technical guarantee for the safe and efficient operation of drilling projects and oil and gas discovery.

[0039] The following are several specific embodiments of the present invention.

[0040] Example 1

[0041] In a specific embodiment 1 of the present invention, the method for predicting a drilling formation pressure profile includes the following steps:

[0042] Step (1): Study the distribution pattern of formation pressure in the study area where the well is drilled, analyze the distribution areas and layers where abnormal formation pressure may appear, and determine the cause of abnormal pressure. Figure 2 This is a plane distribution diagram of abnormal pressure of the target layer in the study area of ​​this embodiment. It can be seen that the predicted well is located in the abnormal pressure area. Figure 3 This is the vertical distribution diagram of abnormal pressure in the study area of ​​this embodiment. The pressure coefficient in this area can be basically divided into three zones vertically. The shallow pressure coefficient above 2500m is concentrated around 1.0, the pressure coefficient between 2500m and 3500m is concentrated between 0.7-1.0 and gradually increases to greater than 1.2, and the deep pressure coefficient above 3500m is more dispersed, with a distribution of 0.8-1.5. The target layer of the well in the embodiment is in the abnormal pressure distribution area. Comprehensive analysis of the corresponding relationship between abnormal pressure and oil shale and salt-gypsum rock shows that undercompaction and hydrocarbon generation by thermal evolution of organic matter are the main reasons for the formation of overpressure in the study area.

[0043] Step (2): Select a suitable reference well. Through comprehensive analysis of structural maps, seismic profiles, etc., it is believed that among the two nearest wells, Well L20 is located in a similar structural position to the well in this embodiment, there is no fault separation between the two, and the target layer has measured pressure data. Therefore, Well L20 is selected as the main reference well, and another adjacent well, Well L67, is selected as an auxiliary correction well.

[0044] Step (3): According to the abnormal pressure cause determined in step (1), select an appropriate pressure prediction method model. The normal trend line method, such as the equivalent depth method or the Eaton formula method, is suitable for predicting the pressure profile of under-compacted formations; the mudstone acoustic wave velocity method, such as the Bowers method, is suitable for predicting the pressure profile of overpressure formations with various genetic mechanisms such as fluid pressurization and pressure transmission. According to step (1), this embodiment is based on the well logging acoustic wave curve of well L67, and the method model is mainly based on the normal trend line method, combined with the Bowers method for prediction.

[0045] Step (4): According to the method selected in step (3), collect the required raw data and predict the formation pressure, including data preprocessing, calculating the pressure gradient of the overlying formation, obtaining mudstone logging parameters, combining the pressure genesis, selecting a suitable method to establish a mudstone velocity model, and generating a formation pressure curve. In this embodiment, based on step (3), the formation pressure profile of well Z27 is compared, the slope and intercept of the trend line of this well are corrected, the error is reduced, and it is as accurate as possible. The formation pressure prediction profile of the designed well is formed. Figure 4 shown.

[0046] Step (5): Adjust the additional coefficients and related parameters according to different geological conditions to generate the final formation pressure prediction curve. The structural location of this well is close to that of the reference well, so no correction is required. Figure 4 This is the predicted profile of the formation pressure of a certain well in Example 1. During the drilling process, judging from the use of drilling fluid density and the total hydrocarbon value, the predicted pressure coefficient of this well is relatively appropriate.

[0047] The formation pressure distribution law of the research area in step (1) includes the plane distribution law of the main layer section, the vertical distribution law and the distribution law of each layer section, etc. The data required for the research on the formation pressure distribution law include regional geological data, drilling data, seismic data, logging data, pressure test data, oil test and production test data, etc.

[0048] The selection of the well in step (2) is mainly based on comparative analysis of factors such as the geological characteristics, structural location, rock type and fracture development of the well location.

[0049] If the Eaton method is used to predict the formation pressure profile in step (3), the N (Eaton) index is optimized in the abnormally high-pressure layer according to the specific conditions of the region and geological age. The approximate range of the N (Eaton) index is determined by parameter regression of some abnormally high-pressure wells in the study area and combined with measured data, and the middle value is taken as the preferred N (Eaton) index result for the area.

[0050] The original data in step (4) include the density, wellbore diameter, acoustic wave time difference, density, resistivity, natural gamma, shear wave time difference of logging, basic formation stratification data, gamma base value stratification depth, segmented drill bit data, mud density, cuttings logging lithology, measured formation pressure, N index and pore pressure gradient (PPG), fracture pressure gradient (FPG), collapse pressure gradient (CPG) range, normal compaction depth range, etc.

[0051] Example 2

[0052] In a specific embodiment 2 of the present invention, the method for predicting a drilling formation pressure profile includes the following steps:

[0053] Step (1): Study the formation pressure distribution law in the study area where the well is drilled, analyze the distribution area and layer section where abnormal formation pressure may appear, and determine the cause of abnormal pressure. Through analysis, the target layer of this well is located in the abnormal pressure distribution area, such as Figure 2 As shown in the figure, the pressure difference between adjacent well areas and the same layer is large. The sand body of the target layer of this well is wrapped in a large set of dark oil shale. The thermal evolution of organic matter and hydrocarbon generation are the main reasons for the overpressure of this well.

[0054] Step (2): Select a suitable reference well. Through comprehensive analysis of structural maps, seismic profiles, etc., it is believed that there is no well with a particularly close structural location between the two nearest wells. After comparison, the structural location of L20 well is similar to that of the well in this embodiment, so L20 well is selected as the main reference well.

[0055] Step (3): According to the abnormal pressure cause determined in step (1), select an appropriate pressure prediction method model. The normal trend line method, such as the equivalent depth method or the Eaton formula method, is suitable for predicting the pressure profile of under-compacted formations; the mudstone acoustic wave velocity method, such as the Bowers method, is suitable for predicting the pressure profile of overpressure formations with various genetic mechanisms such as fluid pressurization and pressure transmission. According to step (1), this embodiment is based on the well logging acoustic wave curve of well Z23, and the method model uses the Bowers method for prediction.

[0056] Step (4): According to the method selected in step (3), the required raw data is collected to predict the formation pressure, including data preprocessing, calculation of the overlying formation pressure gradient, determination of mudstone logging parameters, and selection of an appropriate method to establish a mudstone velocity model in combination with the pressure genesis to generate a formation pressure curve.

[0057] Step (5): Adjust the additional coefficients and related parameters according to different geological conditions to generate the final formation pressure prediction curve. Combined with the specific data of the drilled well, the well is located at the top of the anticline. Based on the well being in a depression, the lithology combination and structural background are basically consistent, and the height difference is within 500m. Based on the inversion of the well logging curve, the coefficient is reduced by 0.05-0.10 according to the experience of the well, so as to more accurately predict the formation pressure of the designed well. In actual operation, the coefficient was reduced by 0.05. It was confirmed by actual drilling that the predicted pressure coefficient of this well is close to the actual situation, with a small error.

[0058] Example 3

[0059] In a specific embodiment 3 of the present invention, the method for predicting a drilling formation pressure profile includes the following steps:

[0060] Step (1): Conduct a study on the formation pressure distribution law in the study area where the well is drilled, analyze the distribution areas and layers where abnormal formation pressure may appear, and determine the cause of abnormal pressure. In this embodiment, there are relatively few actual wells drilled. Through seismic data, structural and sedimentary characteristics, combined with the actual drilling results of a few wells, the pressure distribution law of the study area is analyzed. The target layer of this well is located in an abnormally high-pressure area, and the pressure difference between the same layer in adjacent well areas is large. The target layer is deeply buried, and under-compaction is the main reason for the overpressure of this well.

[0061] Step (2): Select a suitable reference well. Through comprehensive analysis of structural maps, seismic profiles, etc., it is believed that there is no well with a particularly close structural location between the two nearest wells. Through comparative analysis, the M1 well with a similar structural background and VSP measured pressure data is selected as the main reference well. Then, the logging curves of multiple wells in the block are inverted and spliced ​​to improve the prediction accuracy.

[0062] Step (3): According to the abnormal pressure cause determined in step (1), select an appropriate pressure prediction method model. The normal trend line method, such as the equivalent depth method or the Eaton formula method, is suitable for predicting the pressure profile of under-compacted formations; the mudstone acoustic wave velocity method, such as the Bowers method, is suitable for predicting the pressure profile of overpressure formations with various genetic mechanisms such as fluid pressurization and pressure transmission. According to step (1), this embodiment uses the normal trend line method Eaton method for prediction.

[0063] Step (4): According to the method selected in step (3), the required raw data is collected to predict the formation pressure, including data preprocessing, calculation of the overlying formation pressure gradient, determination of mudstone logging parameters, and selection of an appropriate method to establish a mudstone velocity model in combination with the pressure genesis to generate a formation pressure curve.

[0064] Step (5): Adjust the additional coefficient and related parameters according to different geological conditions to generate the final formation pressure prediction curve. Combined with the specific data of the wells that have been drilled, the well is located in the center of the depression. According to the experience summary of oil and gas display on the well surface, shallow gas layer, water injection of adjacent wells, and complex engineering conditions (mainly well leakage), the coefficient is increased by 0.1-0.2 to more accurately predict the formation pressure of the designed well. In actual operation, the coefficient was increased by 0.1. It was confirmed by actual drilling that the predicted pressure coefficient of this well is basically close to the actual situation and is relatively reasonable.

[0065] The drilling formation pressure profile prediction method of the present invention, based on the analysis of geological characteristics, selects suitable adjacent wells according to different geological conditions, selects a reasonable method to predict the formation pressure curve of the designed well according to the cause of abnormal pressure, and adjusts additional coefficients and related parameters according to different geological conditions, and then generates a final formation pressure prediction profile, thereby improving the accuracy of formation pressure of unknown wells, providing a reliable basis for the reasonable design of drilling fluid density and optimization of wellbore structure, and providing technical guarantee for the safe and efficient operation of drilling projects and oil and gas discovery.

[0066] The drilling formation pressure profile prediction method of the present invention mainly includes: studying the distribution law of formation pressure; analyzing the causes of abnormal pressure; selecting wells and optimizing methods according to the causes of pressure; optimizing mudstone velocity models according to the causes of pressure; obtaining preliminary drilling formation pressure prediction results according to the above steps; correcting additional coefficients and related parameters according to specific geological conditions in combination with the results obtained in the above steps; and obtaining the final drilling formation pressure prediction profile based on the results calculated in the above steps. The present invention provides a method and process for predicting drilling formation pressure profiles by combining multiple means based on geological feature analysis, which can improve the accuracy of formation pressure prediction, provide a reliable basis for the reasonable design of drilling fluid density and the optimization of wellbore structure, guide the use of drilling fluid density on site, and provide technical guarantees for the safe and efficient operation of drilling projects and oil and gas discoveries.

[0067] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0068] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A method for predicting a drilling formation pressure profile, characterized in that: The drilling formation pressure profile prediction method includes: Step 1: Study the regional pressure distribution law and analyze the causes of abnormal pressure; Step 2, select a suitable basis well; Step 3, selecting a suitable pressure prediction method model according to the abnormal pressure cause determined in step 1; Step 4, select a suitable method to establish a mudstone velocity model and generate a formation pressure curve; Step 5: Adjust the additional coefficients and related parameters according to different geological conditions to generate the final formation pressure prediction curve.

2. The method for predicting a drilling formation pressure profile according to claim 1, characterized in that: In step 1, the formation pressure distribution law in the study area where the drilling is located is studied, the distribution areas and layers where abnormal formation pressure may appear are analyzed, and a comprehensive geological analysis is carried out to determine the cause of abnormal pressure.

3. The method for predicting a drilling formation pressure profile according to claim 2, characterized in that: In step 1, the formation pressure distribution law of the study area includes the plane distribution law of the main layer segments, the vertical distribution law and the distribution law of each layer segment; the data required to study the formation pressure distribution include regional geological data, drilling data, seismic data, logging data, well logging data, pressure test data, and oil test and production test data.

4. The method for predicting a drilling formation pressure profile according to claim 1, characterized in that: In step 2, the selection of the reference well is mainly based on the comparative analysis of the geological characteristics of the well location, structural position, rock type, the presence or absence of measured pressure data and fracture development conditions, and the drilled well with the highest similarity to the geological conditions of the designed well is selected as the reference well; on the basis of the optimization of the reference well, an auxiliary correction well can also be selected.

5. The method for predicting a drilling formation pressure profile according to claim 1, characterized in that: In step 3, according to the principle of formation pressure prediction method, the normal trend line method, including the equivalent depth method or the Eaton formula method, should be used to predict the under-compacted formation pressure profile; the mudstone acoustic wave velocity method, including the Bowers method, should be used to predict the overpressure formation pressure profile due to fluid pressurization and pressure transmission mechanisms.

6. The method for predicting a drilling formation pressure profile according to claim 5, characterized in that: In step 3, when the Eaton method is used to predict the formation pressure profile, in the abnormally high-pressure layer, N, namely the Eaton index, should be optimized according to the specific conditions of the region and geological age; the approximate range of the N index is determined by parameter regression of some abnormally high-pressure wells in the study area and combined with measured data, and the middle value is taken as the preferred N index result for the area.

7. The method for predicting a drilling formation pressure profile according to claim 1, characterized in that: In step 4, according to the method selected in step 3, the required raw data are collected to predict the formation pressure, including data preprocessing, calculation of the overlying formation pressure gradient, and determination of mudstone logging parameters. In combination with the pressure genesis, an appropriate method is selected to establish a mudstone velocity model and generate a formation pressure curve.

8. The method for predicting a drilling formation pressure profile according to claim 7, characterized in that: In step 4, the original data include the logging density, wellbore diameter, acoustic wave time difference, density, resistivity, natural gamma, shear wave time difference, basic formation stratification data, gamma base value stratification depth, segmented drill bit data, mud density, cuttings logging lithology, measured formation pressure, N index and pore pressure gradient PPG, fracture pressure gradient FPG, collapse pressure gradient CPG range, and normal compaction depth range.

9. The method for predicting a drilling formation pressure profile according to claim 1, characterized in that: In step 5, different geological conditions and parameter adjustments can be carried out according to the following principles: if there is regional pressure anomaly, it is necessary to deeply analyze the cause of abnormal pressure, select the reference well, select the appropriate method model, and make adjustments based on various factors; if the pressure difference in the same layer of adjacent well areas is large, it is necessary to analyze the cause of the pressure difference, clarify the regional pressure change, and re-select the reference well reasonably; if the adjacent well drills the target layer of the designed well, but the structural position is quite different, it is necessary to combine the specific data of the drilled well, and use the prediction of the reference well logging curve to reduce or increase a certain coefficient based on experience for correction; if the adjacent well is not drilled into the target layer, based on the distance between the well and the current well, it is necessary to combine the seismic profile, analyze the structural and sedimentary characteristics, and combine the actual drilling situation of the drilled well to analyze the pressure change characteristics, and finally form a predicted profile through inversion and splicing of the logging curves of multiple wells.

10. A drilling formation pressure profile prediction system, characterized in that: The drilling formation pressure profile prediction system adopts the drilling formation pressure profile prediction method described in any one of claims 1 to 9 to generate a formation pressure prediction curve to perform drilling formation pressure profile prediction.

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