While-drilling pressure monitoring method for different lithologic stratums

Abstract

The invention discloses a method for monitoring pressure while drilling under different lithologic stratums, which comprises the following steps of: respectively calculating the formation pressure of a target well and the formation pressure of an adjacent well by using three formation pressure calculation methods suitable for different lithologic stratums, and calculating the formation pressure of the target well according to the actually measured formation pressure of the adjacent well and the calculated formation pressure of the adjacent well. Weighting coefficients of the three calculation methods are obtained, weighting calculation is conducted on the formation pressure, obtained through the three calculation methods, of the target well through the weighting coefficients, and the formation pressure while drilling of the target well is obtained. According to the method, different lithologic formation pressures can be monitored in the while-drilling process, high accuracy can be achieved in monitoring of the different lithologic formation pressures, the applicability and accuracy of formation pressure while-drilling monitoring are improved, and the problem that while-drilling pressure monitoring cannot be achieved for complex lithology or the monitoring precision is too low is solved. In the while-drilling process, if the formation pressure is abnormal, early warning can be conducted in time, so that the well control risk is reduced, and sufficient safety guarantee is provided for high-speed well drilling.

Description

Technical Field

[0001] This invention relates to the field of petroleum exploration and development technology, and in particular to a method for monitoring drilling pressure in formations with different lithologies. Background Technology

[0002] With increasing energy demand, the exploration and development of oil and gas resources is intensifying, and exploration targets are gradually shifting from shallow to deep formations, leading to a rise in the risk of abnormal pressure events encountered during drilling. As a crucial foundation for ensuring drilling safety, accurate calculation of formation pore pressure is paramount. In drilling operations, appropriate engineering parameters and drilling fluid density are prerequisites for ensuring downhole safety and improving drilling efficiency, and accurately understanding the distribution of formation pore pressure is essential for this work.

[0003] In recent years, with a deeper understanding of formation pressure and more detailed analysis of its causes, it has become possible to monitor formation pressure using rock drillability parameters. However, these methods have significant limitations. A single monitoring method may be highly accurate for monitoring the formation pressure of a particular lithology, but less accurate for other lithologies. In actual drilling operations, various lithologies are encountered, especially in wells with complex formations or ultra-deep wells. Failure to accurately monitor the formation pressure of different lithologies in real time can lead to extremely high drilling risks.

[0004] Therefore, how to develop a method for monitoring formation pressure during drilling that is applicable to different lithological formations, and how to achieve high accuracy in monitoring formation pressure across different lithological formations, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for monitoring formation pressure while drilling in different lithological formations, which can perform full-coverage monitoring of formation pressure while drilling, accurately calculate formation pressure, and reduce drilling risks and drilling costs.

[0006] Therefore, the present invention provides a method for monitoring drilling pressure in formations with different lithologies, comprising the following steps:

[0007] S1: Collect the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density in the area where the target well is located;

[0008] S2: Calculate the DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value for the target well.

[0009] S3: Calculate the DC index formation pressure of the target well based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend; calculate the Sigma index formation pressure of the target well based on the drilling fluid density, Sigma index, Sigma index trend, and compensation adjustment coefficient; calculate the MSE formation pressure of the target well based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value.

[0010] S4: Collect the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density in the area where the target well is located;

[0011] S5: Calculate the DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value of the adjacent well.

[0012] S6: Calculate the DC index formation pressure of the adjacent well based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend; calculate the Sigma index formation pressure of the adjacent well based on the drilling fluid density, Sigma index, Sigma index trend, and compensation adjustment coefficient; calculate the MSE formation pressure of the adjacent well based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value.

[0013] S7: Calculate the DC index formation pressure weighting coefficient of the adjacent well based on the DC index formation pressure and the measured formation pressure of the adjacent well; calculate the Sigma index formation pressure weighting coefficient of the adjacent well based on the Sigma index formation pressure and the measured formation pressure of the adjacent well; calculate the MSE formation pressure weighting coefficient of the adjacent well based on the MSE formation pressure and the measured formation pressure of the adjacent well.

[0014] S8: Based on the weighted coefficients of the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure of the adjacent wells, the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure of the target well are weighted and calculated to obtain the drilling formation pressure of the target well.

[0015] In one possible implementation, in the above-described method for monitoring drilling pressure under different lithological formations provided by the present invention, in step S3, the DC index formation pressure of the target well is calculated based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend. Specifically, the calculation is performed using the following formula:

[0016]

[0017] Among them, PP dc This represents the dc exponential formation pressure of the target well, in g / cm³. 3 OBG represents the overlying formation pressure of the target well, in g / cm³. 3 ;PP N This represents the formation hydrostatic pressure of the target well, in g / cm³. 3 dc represents the DC exponent of the target well, which is dimensionless; dcn represents the DC exponent trend value of the target well, which is dimensionless.

[0018] In one possible implementation, in the above-described method for monitoring drilling pressure under different lithological formations provided by the present invention, in step S3, the sigma index formation pressure of the target well is calculated based on the drilling fluid density, sigma index, sigma index trend, and compensation adjustment coefficient of the target well, specifically calculated using the following formula:

[0019]

[0020] Among them, PP sigma This represents the sigma-index formation pressure of the target well, expressed in g / cm³. 3 ;ρ 钻井液 This indicates the drilling fluid density of the target well, in g / cm³. 3 ; sigma represents the sigma exponent of the target well, dimensionless; sigma' represents the trend value of the sigma exponent of the target well, dimensionless; h represents the well depth in meters; n represents the compensation adjustment coefficient of the target well, dimensionless.

[0021] In one possible implementation, in the above-described method for monitoring drilling pressure under different lithological formations provided by the present invention, in step S3, the MSE formation pressure of the target well is calculated based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value. Specifically, the calculation is performed using the following formula:

[0022] PP MSE =OBG-(OBG-PP) N (MSE / MSEN) X(4)

[0023] Among them, PP MSE The MSE (Mean Sedimentary Estimate) of the target well is expressed in g / cm³. 3 MSE represents the MSE of the target well, in MPa; MSEN represents the MSE trend of the target well, in MPa; X represents the Eaton index correction value of the target well, dimensionless.

[0024] In one possible implementation, in the above-described method for monitoring drilling pressure under different lithological formations provided by the present invention, in step S6, the DC index formation pressure of the adjacent well is calculated based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend. Specifically, it is calculated using the following formula:

[0025]

[0026] Among them, PP dc邻井 This represents the DC exponential formation pressure of the adjacent well, in g / cm³. 3 ;OBG 邻井 This indicates the overlying formation pressure of the adjacent well, in g / cm³. 3 ;PP N邻井 This indicates the formation hydrostatic pressure of the adjacent well, in g / cm³. 3 ;dc 邻井 The dc exponent of the adjacent well is dimensionless; dcn 邻井 The DC exponential trend value of the adjacent well is dimensionless.

[0027] In one possible implementation, in the above-described method for monitoring drilling pressure under different lithological formations provided by the present invention, in step S6, the sigma index formation pressure of the adjacent well is calculated based on the drilling fluid density, sigma index, sigma index trend, and compensation adjustment coefficient of the adjacent well, specifically calculated using the following formula:

[0028]

[0029] Among them, PP sigma邻井 This represents the sigma-index formation pressure of the adjacent well, in g / cm³. 3 ;ρ 邻井钻井液 This indicates the drilling fluid density of the adjacent well, in g / cm³. 3 ; sigma 邻井 The sigma exponent of the adjacent well is dimensionless; sigma' 邻井 The sigma exponential trend value of the adjacent well is dimensionless; h 邻井 Indicates well depth, in meters (m); n邻井 This represents the compensation adjustment coefficient of the adjacent well, which is dimensionless.

[0030] In one possible implementation, in the above-described method for monitoring drilling pressure under different lithological formations provided by the present invention, in step S6, the MSE formation pressure of the adjacent well is calculated based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value of the adjacent well. Specifically, the calculation is performed using the following formula:

[0031]

[0032] Among them, PP MSE邻井 This indicates the MSE formation pressure of the adjacent well, in g / cm³. 3 MSE 邻井 The MSE of the adjacent well is expressed in MPa; MSEN 邻井 The MSE trend of the adjacent well is represented in MPa; X 邻井 This represents the Eaton index correction value of the adjacent well, which is dimensionless.

[0033] In one possible implementation, in the above-described method for monitoring drilling pressure under different lithological formations provided by the present invention, in step S7, the DC index formation pressure weighting coefficient of the adjacent well is calculated based on the DC index formation pressure and the measured formation pressure of the adjacent well; the Sigma index formation pressure weighting coefficient of the adjacent well is calculated based on the Sigma index formation pressure and the measured formation pressure of the adjacent well; and the MSE formation pressure weighting coefficient of the adjacent well is calculated based on the MSE formation pressure and the measured formation pressure of the adjacent well. Specifically, these calculations are performed using the following formulas:

[0034]

[0035] Where, a represents the DC exponential formation pressure weighting coefficient of the adjacent well, dimensionless; b represents the Sigma exponential formation pressure weighting coefficient of the adjacent well, dimensionless; c represents the MSE formation pressure weighting coefficient of the adjacent well, dimensionless; N represents the number of adjacent wells, a positive integer, dimensionless; PP 实测i This represents the measured formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N; PP dc邻井i This represents the DC exponential formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N; PP sigma邻井i This represents the sigma index formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N; PP MSE邻井iThis represents the MSE formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N.

[0036] In one possible implementation, in the above-described method for monitoring drilling pressure under different lithological formations provided by the present invention, step S8 involves weighting the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure of the target well according to the DC index formation pressure weighting coefficient, Sigma index formation pressure weighting coefficient, and MSE formation pressure weighting coefficient of the adjacent well, to calculate the drilling formation pressure of the target well; specifically, it is calculated using the following formula:

[0037]

[0038] Wherein, PP represents the formation pressure while drilling in the target well, in g / cm³. 3 ;PP dc This represents the dc exponential formation pressure of the target well, in g / cm³. 3 ;PP sigma This represents the sigma-index formation pressure of the target well, expressed in g / cm³. 3 ;PP MSE The MSE (Mean Sedimentary Estimate) of the target well is expressed in g / cm³. 3 a represents the DC exponential formation pressure weighting coefficient of the adjacent well, which is dimensionless; b represents the Sigma exponential formation pressure weighting coefficient of the adjacent well, which is dimensionless; c represents the MSE formation pressure weighting coefficient of the adjacent well, which is dimensionless.

[0039] In one possible implementation, in the above-described method for monitoring drilling pressure under different lithological formations provided by the present invention, the Eaton index correction value is greater than 0 and less than or equal to 2.

[0040] The drilling pressure monitoring method for different lithological formations provided by this invention first calculates the formation pressure of the target well and adjacent wells using three formation pressure calculation methods applicable to different lithological formations. Then, based on the measured formation pressure of the adjacent well and the calculated formation pressure of the adjacent well, a weighting coefficient of the three calculation methods is obtained. Finally, the formation pressure of the target well obtained by the three calculation methods is weighted using the weighting coefficient of the three calculation methods to obtain the drilling formation pressure of the target well. The formation pressure obtained by the method of this invention can achieve high accuracy for different lithological formations of the target well. The method of this invention can monitor formation pressure in different lithologies during drilling, and can achieve high accuracy in monitoring formation pressure in different lithologies. This improves the applicability and accuracy of formation pressure monitoring during drilling, and solves the problem that it is impossible to monitor formation pressure during drilling or the monitoring accuracy is too low for complex lithologies. In this way, if the formation pressure is abnormal during drilling, it can provide timely warning, thereby reducing well control risks and providing sufficient safety for high-speed drilling. It has extremely high application prospects in complex lithology oil and gas reservoirs and ultra-deep well drilling. Attached Figure Description

[0041] Figure 1 A schematic flowchart of a drilling pressure monitoring method for different lithological formations provided by the present invention;

[0042] Figure 2 This is a formation pressure error analysis diagram of the target well SG189 in Embodiment 2 of the present invention. Detailed Implementation

[0043] The following detailed description, in conjunction with the accompanying drawings, describes a specific implementation of a drilling pressure monitoring method for different lithological formations provided by the present invention.

[0044] This invention provides a method for monitoring drilling pressure in formations with different lithologies, such as... Figure 1 As shown, it may include the following steps:

[0045] Step 1: Collect data on the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density in the area where the target well is located.

[0046] In practice, data on the target well can be collected by consulting drilling and completion data, well history, geological design, or regional geological information.

[0047] Step 2: Calculate the target well's DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value.

[0048] In practical implementation, during well logging, engineering parameters such as drilling pressure, rotary table speed, mechanical drilling speed, drilling fluid density, and drill bit size are comprehensively collected. The DC index, Sigma index, and MSE are calculated using existing formulas. For the DC index, data processing is performed, selecting the initial and final DC index values ​​from the same formation or drill bit's footage. These values ​​are then plotted on a logarithmic coordinate system, and the trend slope is calculated to obtain the DC index trend line. The value corresponding to each well depth is the DC index trend value. Similarly, for the Sigma index, data processing is performed, selecting the initial and final Sigma index values ​​from the same formation or drill bit's footage. These values ​​are then plotted on a linear coordinate system, and the trend slope is calculated to obtain the Sigma index trend line. The value corresponding to each well depth is the Sigma index trend value. By processing the MSE data, the initial depth MSE value and the completed depth MSE value during the drilling footage of the same layer or the same drill bit are selected, and then put into a linear coordinate system to calculate the trend slope and obtain the MSE trend line. The value corresponding to each well depth is the MSE trend value.

[0049] In practice, the compensation adjustment coefficient n is selected based on the value of the sigma exponent. Specifically, when sigma > 1, n = (1 / 640) × (4 - (0.75 / sigma)); when sigma ≤ 1, n = 3.25 / (640 × sigma).

[0050] In practice, the Eaton index correction value can be selected from a range greater than 0 and less than or equal to 2. Preferably, the Eaton index correction value can be 1.5, which is dimensionless.

[0051] Step 3: Calculate the DC index formation pressure of the target well based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend; calculate the Sigma index formation pressure of the target well based on the drilling fluid density, Sigma index, Sigma index trend, and compensation adjustment coefficient; calculate the MSE formation pressure of the target well based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value.

[0052] In practical implementation, the DC index formation pressure of the target well is calculated based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend. This calculation can be performed using the following formula:

[0053]

[0054] Among them, PP dc This represents the dc exponential formation pressure of the target well, expressed in g / cm³. 3OBG represents the overlying formation pressure of the target well, in g / cm³. 3 ;PP N This represents the formation hydrostatic pressure of the target well, expressed in g / cm³. 3 ;dc represents the DC exponent of the target well, which is dimensionless;dcn represents the trend value of the DC exponent of the target well, which is dimensionless.

[0055] In practical implementation, the Sigma-index formation pressure of the target well is calculated based on the drilling fluid density, Sigma index, Sigma index trend, and compensation adjustment coefficient. This can be achieved using the following formula:

[0056]

[0057] Among them, PP sigma This represents the formation pressure at the sigma index of the target well, expressed in g / cm³. 3 ;ρ 钻井液 This indicates the drilling fluid density of the target well, expressed in g / cm³. 3 ; sigma represents the sigma exponent of the target well, dimensionless; sigma' represents the trend value of the sigma exponent of the target well, dimensionless; h represents the well depth in meters; n represents the compensation adjustment coefficient of the target well, dimensionless.

[0058] In practical implementation, the MSE formation pressure of the target well is calculated based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value. Specifically, it can be calculated using the following formula:

[0059] PP MSE =OBG-(OBG-PP) N (MSE / MSEN) X (4)

[0060] Among them, PP MSE This indicates the MSE (Mean Sedimentary Estimate) formation pressure of the target well, expressed in g / cm³. 3 MSE represents the target well's MSE in MPa; MSEN represents the target well's MSE trend in MPa; X represents the target well's Eaton index correction value, which is dimensionless.

[0061] Step 4: Collect the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density in the area where the target well is located.

[0062] It should be noted that the number of neighboring wells of the target well can be 1, or the number of neighboring wells of the target well can be multiple, without limitation. When the number of neighboring wells is 1, the neighboring well closest to the target well is selected; when multiple neighboring wells are selected, they can be selected in order of their distance from the target well to the farthest.

[0063] In practice, the methods for collecting the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density in the area where the adjacent well is located are the same as those for collecting the data of the target well in the first step, and will not be repeated here.

[0064] Step 5: Calculate the DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value for adjacent wells.

[0065] In practice, the calculation methods for the DC index, DC index trend, Sigma index, Sigma index trend, MSE, and MSE trend of adjacent wells are the same as those for the target well in the second step, and will not be elaborated here.

[0066] In practice, the compensation adjustment coefficient n is selected based on the value of the sigma exponent. Specifically, when sigma > 1, n = (1 / 640) × (4 - (0.75 / sigma)); when sigma ≤ 1, n = 3.25 / (640 × sigma).

[0067] In practice, the Eaton index correction value can be selected from a range greater than 0 and less than or equal to 2. Preferably, the Eaton index correction value can be 1.5, which is dimensionless.

[0068] Step 6: Calculate the DC index formation pressure of the adjacent well based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend; calculate the Sigma index formation pressure of the adjacent well based on the drilling fluid density, Sigma index, Sigma index trend, and compensation adjustment coefficient; calculate the MSE formation pressure of the adjacent well based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value.

[0069] In practical implementation, the DC index formation pressure of the adjacent well is calculated based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend. This can be achieved using the following formula:

[0070]

[0071] Among them, PP dc邻井 This represents the DC index formation pressure of the adjacent well, expressed in g / cm³. 3;OBG 邻井 This indicates the overlying formation pressure of the adjacent well, expressed in g / cm³. 3 ;PP N邻井 This indicates the formation hydrostatic pressure of the adjacent well, expressed in g / cm³. 3 ;dc 邻井 The DC exponent of the adjacent well is dimensionless; dcn 邻井 This represents the DC exponential trend value of the adjacent well, and is dimensionless.

[0072] In practice, the Sigma-index formation pressure of the adjacent well is calculated based on the drilling fluid density, Sigma index, Sigma index trend, and compensation adjustment coefficient of the adjacent well. This can be achieved using the following formula:

[0073]

[0074] Among them, PP sigma邻井 This represents the sigma index formation pressure of the adjacent well, expressed in g / cm³. 3 ;ρ 邻井钻井液 This indicates the drilling fluid density of the adjacent well, expressed in g / cm³. 3 ; sigma 邻井 The sigma exponent of the adjacent well is dimensionless; sigma' 邻井 h represents the trend value of the sigma exponent of adjacent wells, dimensionless; 邻井 Indicates well depth, in meters (m); n 邻井 This represents the compensation adjustment coefficient for adjacent wells, and is dimensionless.

[0075] In practice, the MSE formation pressure of the adjacent well is calculated based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value. This can be achieved using the following formula:

[0076]

[0077] Among them, PP MSE邻井 This indicates the MSE formation pressure of the adjacent well, in g / cm³. 3 MSE 邻井 MSEN represents the MSE of adjacent wells, in MPa. 邻井 Indicates the MSE trend of adjacent wells, in MPa; X 邻井 This represents the Eaton index correction value for the adjacent well, and is dimensionless.

[0078] Step 7: Calculate the DC index formation pressure weighting coefficient of the adjacent well based on the DC index formation pressure and the measured formation pressure of the adjacent well; calculate the Sigma index formation pressure weighting coefficient of the adjacent well based on the Sigma index formation pressure and the measured formation pressure of the adjacent well; calculate the MSE formation pressure weighting coefficient of the adjacent well based on the MSE formation pressure and the measured formation pressure of the adjacent well.

[0079] In practical implementation, the DC index formation pressure weighting coefficient, Sigma index formation pressure weighting coefficient, and MSE formation pressure weighting coefficient of adjacent wells can be calculated using the following formulas:

[0080]

[0081] Where, a represents the DC exponential formation pressure weighting coefficient of the adjacent well, dimensionless; b represents the Sigma exponential formation pressure weighting coefficient of the adjacent well, dimensionless; c represents the MSE formation pressure weighting coefficient of the adjacent well, dimensionless; N represents the number of adjacent wells, a positive integer, dimensionless; PP 实测i This represents the measured formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N; PP dc邻井i This represents the DC exponential formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N; PP sigma邻井i This represents the sigma index formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N; PP MSE邻井i This represents the MSE formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N.

[0082] Step 8: Based on the weighted coefficients of the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure of the adjacent wells, the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure of the target well are weighted and calculated to obtain the drilling formation pressure of the target well.

[0083] It should be noted that using the DC index to calculate formation pressure is mainly suitable for monitoring formation pressure in shale and mudstone formations; using the Sigma index is mainly suitable for monitoring formation pressure in carbonate rocks; and using the MSE index can be applied to special lithologies such as volcanic and metamorphic rocks, and is less affected by drilling parameters, making it suitable for both pressure-controlled drilling and directional drilling. In actual drilling operations, various lithologies are encountered. If only one calculation method is used for formation pressure monitoring while drilling, the accuracy of formation pressure monitoring will inevitably be low. Therefore, in order to adapt to different lithologies, improve the monitoring accuracy of formation pressure while drilling, and reduce the influence of human-controlled engineering parameters during drilling, this invention calculates the formation pressure while drilling of the target well by weighting the target well's DC index formation pressure, Sigma index formation pressure, and MSE formation pressure based on the weighting coefficients of adjacent wells' DC index formation pressure, Sigma index formation pressure, and MSE formation pressure. The calculation can be performed using the following formula:

[0084]

[0085] Where PP represents the formation pressure while drilling in the target well, in g / cm³. 3 ;PP dc This represents the dc exponential formation pressure of the target well, expressed in g / cm³. 3 ;PP sigma This represents the formation pressure at the sigma index of the target well, expressed in g / cm³. 3 ;PP MSE This indicates the MSE (Mean Sedimentary Estimate) formation pressure of the target well, expressed in g / cm³. 3 a represents the DC index formation pressure weighting coefficient of the adjacent well, dimensionless; b represents the Sigma index formation pressure weighting coefficient of the adjacent well, dimensionless; c represents the MSE formation pressure weighting coefficient of the adjacent well, dimensionless.

[0086] The drilling pressure monitoring method for different lithological formations provided by this invention first calculates the formation pressure of the target well and adjacent wells using three formation pressure calculation methods applicable to different lithological formations. Then, based on the measured formation pressure of the adjacent well and the calculated formation pressure of the adjacent well, a weighting coefficient of the three calculation methods is obtained. Finally, the formation pressure of the target well obtained by the three calculation methods is weighted using the weighting coefficient of the three calculation methods to obtain the drilling formation pressure of the target well. The formation pressure obtained by the method of this invention can achieve high accuracy for different lithological formations of the target well. The method of this invention can monitor formation pressure in different lithologies during drilling, and can achieve high accuracy in monitoring formation pressure in different lithologies. This improves the applicability and accuracy of formation pressure monitoring during drilling, and solves the problem that it is impossible to monitor formation pressure during drilling or the monitoring accuracy is too low for complex lithologies. In this way, if the formation pressure is abnormal during drilling, it can provide timely warning, thereby reducing well control risks and providing sufficient safety for high-speed drilling. It has extremely high application prospects in complex lithology oil and gas reservoirs and ultra-deep well drilling.

[0087] The following two specific embodiments illustrate in detail the implementation of the drilling pressure monitoring method for different lithological formations provided by the present invention.

[0088] Example 1: Using H37 as the target well, H33 was selected as the adjacent well.

[0089] Step 1: Collect the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density in the area where the target well H37 is located, as shown in Table 1.

[0090] Table 1

[0091]

[0092] Step 2: Calculate the DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value for well H37, as shown in Table 2.

[0093] Table 2

[0094]

[0095] Step 3: Based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend of well H37, the DC index formation pressure of well H37 is calculated; based on the drilling fluid density, Sigma index, Sigma index trend, and compensation adjustment coefficient of well H37, the Sigma index formation pressure of well H37 is calculated; based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value of well H37, the MSE formation pressure of well H37 is calculated, as shown in Table 3.

[0096] Table 3

[0097]

[0098] Step 4: First, collect the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density in the area where the adjacent well H33 is located. Then, calculate the DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value for the adjacent well H33. Next, calculate the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure for the adjacent well H33. Finally, calculate the DC index formation pressure weighting coefficient a, the Sigma index formation pressure weighting coefficient b, and the MSE formation pressure weighting coefficient c for the adjacent well H33, as shown in Table 4.

[0099] Table 4

[0100]

[0101] Step 5: Based on the dc exponential formation pressure weighting coefficient, sigma exponential formation pressure weighting coefficient, and MSE formation pressure weighting coefficient of the adjacent well H33, the dc exponential formation pressure, sigma exponential formation pressure, and MSE formation pressure of the target well H37 are weighted and calculated to obtain the drilling formation pressure of the target well H37, as shown in Table 5.

[0102] Table 5

[0103]

[0104] Example 2: Using SG189 as the target well, SG165, SG180, and SG151 were selected as adjacent wells.

[0105] First, the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density of the area where the target well SG189 is located are collected. Then, the DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value for well SG189 are calculated. Next, the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure of well SG189 are calculated. Afterward, the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density of the areas where adjacent wells (SG165, SG180, and SG151) are located are collected. Then, the DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value for the three adjacent wells are calculated respectively. Finally, the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure for the three adjacent wells are calculated respectively. Next, the weighting coefficients for DC formation pressure (a), Sigma formation pressure (b), and MSE formation pressure (c) were calculated. Finally, using the weighting coefficients a, b, and c, the DC formation pressure, Sigma formation pressure, and MSE formation pressure of well SG189 were weighted and calculated to obtain the drilling formation pressure of well SG189, as shown in Tables 6 and 7.

[0106] Table 6

[0107]

[0108] Table 7

[0109]

[0110] Post-drilling analysis revealed significant lithological variation throughout well SG189, with sedimentary, volcanic, and metamorphic rocks all present. Example 2 of this invention also includes an error analysis of the formation pressure calculated using the method of this invention. This is achieved by comparing the formation pressure obtained from the drilling monitoring using the method of this invention with the actual logging pressure, and calculating the error, such as... Figure 2 As shown in Table 8, the method of this invention achieves high accuracy in formation pressure monitoring during drilling, with an average error of less than 5%. This demonstrates that the method of this invention can monitor formation pressure in different lithologies during drilling, achieving high accuracy across various formation types. It improves the applicability and accuracy of formation pressure monitoring during drilling, solving the problem of inability to monitor formation pressure during drilling or insufficient accuracy in complex lithologies (such as volcanic rocks and metamorphic rocks). Thus, if abnormal formation pressure occurs during drilling, timely warnings can be issued, reducing well control risks and providing sufficient safety assurance for high-speed drilling. This method has extremely high application prospects in complex lithology oil and gas reservoirs and ultra-deep well drilling.

[0111] Table 8

[0112]

[0113] This invention provides a method for monitoring drilling pressure in different lithological formations. First, three formation pressure calculation methods applicable to different lithological formations are used to calculate the formation pressure of the target well and adjacent wells respectively. Then, based on the measured formation pressure of the adjacent well and the calculated formation pressure of the adjacent well, weighting coefficients of the three calculation methods are obtained. Finally, the formation pressure of the target well obtained by the three calculation methods is weighted using the weighting coefficients of the three calculation methods to obtain the drilling formation pressure of the target well. The formation pressure obtained by the method of this invention can achieve high accuracy for different lithological formations of the target well. The method of this invention can monitor formation pressure in different lithologies during drilling, and can achieve high accuracy in monitoring formation pressure in different lithologies. This improves the applicability and accuracy of formation pressure monitoring during drilling, and solves the problem that it is impossible to monitor formation pressure during drilling or the monitoring accuracy is too low for complex lithologies. In this way, if the formation pressure is abnormal during drilling, it can provide timely warning, thereby reducing well control risks and providing sufficient safety for high-speed drilling. It has extremely high application prospects in complex lithology oil and gas reservoirs and ultra-deep well drilling.

[0114] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for monitoring drilling pressure in formations of different lithologies, characterized in that, Includes the following steps: S1: Collect the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density in the area where the target well is located; S2: Calculate the DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value for the target well. S3: Calculate the DC index formation pressure of the target well based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend; calculate the Sigma index formation pressure of the target well based on the drilling fluid density, Sigma index, Sigma index trend, and compensation adjustment coefficient; calculate the MSE formation pressure of the target well based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value. S4: Collect the overlying formation pressure, formation hydrostatic pressure, and drilling fluid density in the area where the target well is located; S5: Calculate the DC index, DC index trend, Sigma index, Sigma index trend, compensation adjustment coefficient, MSE, MSE trend, and Eaton index correction value of the adjacent well. S6: Calculate the DC index formation pressure of the adjacent well based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend; calculate the Sigma index formation pressure of the adjacent well based on the drilling fluid density, Sigma index, Sigma index trend, and compensation adjustment coefficient; calculate the MSE formation pressure of the adjacent well based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value. S7: Calculate the DC index formation pressure weighting coefficient of the adjacent well based on the DC index formation pressure and the measured formation pressure of the adjacent well; calculate the Sigma index formation pressure weighting coefficient of the adjacent well based on the Sigma index formation pressure and the measured formation pressure of the adjacent well; calculate the MSE formation pressure weighting coefficient of the adjacent well based on the MSE formation pressure and the measured formation pressure of the adjacent well. S8: Based on the weighted coefficients of the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure of the adjacent wells, the DC index formation pressure, Sigma index formation pressure, and MSE formation pressure of the target well are weighted and calculated to obtain the drilling formation pressure of the target well.

2. The drilling pressure monitoring method for different lithological formations as described in claim 1, characterized in that, In step S3, the DC index formation pressure of the target well is calculated based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend. Specifically, it is calculated using the following formula: Among them, PP dc This represents the dc exponential formation pressure of the target well, in g / cm³. 3 OBG represents the overlying formation pressure of the target well, in g / cm³. 3 ;PP N This represents the formation hydrostatic pressure of the target well, in g / cm³. 3 dc represents the DC exponent of the target well, which is dimensionless; dcn represents the DC exponent trend value of the target well, which is dimensionless.

3. The drilling pressure monitoring method for different lithological formations as described in claim 2, characterized in that, In step S3, the sigma index formation pressure of the target well is calculated based on the drilling fluid density, sigma index, sigma index trend, and compensation adjustment coefficient of the target well, specifically using the following formula: Among them, PP sigma This represents the sigma-index formation pressure of the target well, expressed in g / cm³. 3 ;ρ 钻井液 This indicates the drilling fluid density of the target well, in g / cm³. 3 ; sigma represents the sigma exponent of the target well, dimensionless; sigma' represents the trend value of the sigma exponent of the target well, dimensionless; h represents the well depth in meters; n represents the compensation adjustment coefficient of the target well, dimensionless.

4. The drilling pressure monitoring method for different lithological formations as described in claim 3, characterized in that, In step S3, the MSE formation pressure of the target well is calculated based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value. Specifically, the calculation is performed using the following formula: PP MSE =OBG-(OBG-PP N (MSE / MSEN) X (4) Among them, PP MSE The MSE (Mean Sedimentary Estimate) of the target well is expressed in g / cm³. 3 MSE represents the MSE of the target well, in MPa; MSEN represents the MSE trend of the target well, in MPa; X represents the Eaton index correction value of the target well, dimensionless.

5. The drilling pressure monitoring method for different lithological formations as described in claim 1, characterized in that, In step S6, the DC index formation pressure of the adjacent well is calculated based on the overlying formation pressure, formation hydrostatic pressure, DC index, and DC index trend. Specifically, it is calculated using the following formula: Among them, PP dc邻井 This represents the DC exponential formation pressure of the adjacent well, in g / cm³. 3 ;OBG 邻井 This indicates the overlying formation pressure of the adjacent well, expressed in g / cm³. 3 ;PP N邻井 This indicates the formation hydrostatic pressure of the adjacent well, in g / cm³. 3 ;dc 邻井 The dc exponent of the adjacent well is dimensionless; dcn 邻井 The DC exponential trend value of the adjacent well is dimensionless.

6. The drilling pressure monitoring method for different lithological formations as described in claim 5, characterized in that, In step S6, the sigma index formation pressure of the adjacent well is calculated based on the drilling fluid density, sigma index, sigma index trend, and compensation adjustment coefficient of the adjacent well. Specifically, this is calculated using the following formula: Among them, PP sigma邻井 This represents the sigma-index formation pressure of the adjacent well, in g / cm³. 3 ;ρ 邻井钻井液 This indicates the drilling fluid density of the adjacent well, in g / cm³. 3 ; sigma 邻井 The sigma exponent of the adjacent well is dimensionless; sigma' 邻井 The sigma exponential trend value of the adjacent well is represented, dimensionless; h 邻井 Indicates well depth, in meters (m); n 邻井 This represents the compensation adjustment coefficient of the adjacent well, which is dimensionless.

7. The drilling pressure monitoring method for different lithological formations as described in claim 6, characterized in that, In step S6, the MSE formation pressure of the adjacent well is calculated based on the overlying formation pressure, formation hydrostatic pressure, MSE, MSE trend, and Eaton index correction value. Specifically, the calculation is performed using the following formula: Among them, PP MSE邻井 This indicates the MSE formation pressure of the adjacent well, in g / cm³. 3 MSE 邻井 The MSE of the adjacent well is expressed in MPa; MSEN 邻井 The MSE trend of the adjacent well is represented in MPa; X 邻井 This represents the Eaton index correction value of the adjacent well, which is dimensionless.

8. The drilling pressure monitoring method for different lithological formations as described in claim 7, characterized in that, In step S7, the weighting coefficient of the DC-index formation pressure of the adjacent well is calculated based on the DC-index formation pressure and the measured formation pressure of the adjacent well; the weighting coefficient of the Sigma-index formation pressure of the adjacent well is calculated based on the Sigma-index formation pressure and the measured formation pressure of the adjacent well; and the weighting coefficient of the MSE formation pressure of the adjacent well is calculated based on the MSE formation pressure and the measured formation pressure of the adjacent well. Specifically, these calculations are performed using the following formulas: Where, a represents the DC exponential formation pressure weighting coefficient of the adjacent well, dimensionless; b represents the Sigma exponential formation pressure weighting coefficient of the adjacent well, dimensionless; c represents the MSE formation pressure weighting coefficient of the adjacent well, dimensionless; N represents the number of adjacent wells, a positive integer, dimensionless; PP 实测i This represents the measured formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N; PP dc邻井i This represents the DC exponential formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N; PP sigma邻井i This represents the sigma index formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N; PP MSE邻井i This represents the MSE formation pressure of adjacent well i, in g / cm³. 3 , i = 1, 2, ..., N.

9. The drilling pressure monitoring method for different lithological formations as described in claim 4 or 8, characterized in that, Step S8: Based on the DC exponential formation pressure weighting coefficient, Sigma exponential formation pressure weighting coefficient, and MSE formation pressure weighting coefficient of the adjacent wells, the DC exponential formation pressure, Sigma exponential formation pressure, and MSE formation pressure of the target well are weighted and calculated to obtain the drilling formation pressure of the target well; specifically, it is calculated using the following formula: Wherein, PP represents the formation pressure while drilling in the target well, in g / cm³. 3 ;PP dc This represents the dc exponential formation pressure of the target well, in g / cm³. 3 ;PP sigma This represents the sigma-index formation pressure of the target well, expressed in g / cm³. 3 ;PP MSE The MSE (Mean Sedimentary Estimate) of the target well is expressed in g / cm³. 3 a represents the DC exponential formation pressure weighting coefficient of the adjacent well, which is dimensionless; b represents the Sigma exponential formation pressure weighting coefficient of the adjacent well, which is dimensionless; c represents the MSE formation pressure weighting coefficient of the adjacent well, which is dimensionless.

10. The method for monitoring drilling pressure under different lithological formations as described in any one of claims 1 to 8, characterized in that, Eaton index correction values ​​are greater than 0 and less than or equal to 2.

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