A method for predicting the pore pressure of a target formation of a current well before drilling based on well logging data of a neighboring well

Abstract

The present application belongs to the field of petroleum and natural gas engineering, and provides a method for predicting the pore pressure of a target formation of a current well before drilling based on well logging data of a neighboring well. First, the pore pressure of the neighboring well is calculated based on the well logging data of the neighboring well. Then, the depth range of the target formation of the current well is divided. Finally, the pore pressure of the target formation of the current well in each depth range is calculated in combination with the geometric azimuth diagram of the neighboring well and the current well. The prediction accuracy of the method is more than 95% through comparison with field tests, and the prediction accuracy is improved by about 20% compared with conventional methods. The present application also provides a field test method for testing the pore pressure of the target formation of the current well. Compared with the oil test method in the production stage, the coincidence rate is 95.9%, and the problem that the pore pressure of the target formation is difficult to test in the drilling stage is solved.

Description

Technical Field

[0001] This invention belongs to the field of petroleum and natural gas engineering and relates to a method for predicting the pore pressure of the target formation in the current well before drilling based on logging data from adjacent wells. Background Technology

[0002] Formation pore pressure is a critical parameter in oil and gas drilling, often simply referred to as formation pressure. Accurate prediction of formation pore pressure can significantly reduce drilling risks such as blowouts and lost circulation, effectively shortening the project cycle and saving drilling costs. However, current pre-drilling prediction systems for formation pore pressure are still immature, heavily reliant on seismic velocity data. Considering the insufficient resolution of seismic velocity (far lower than the 0.1m resolution of well logging), pre-drilling prediction of formation pore pressure consistently falls short of field requirements. Within the same well site, well logging data from drilled wells has sufficiently high resolution (typically 0.1m) and is of significant value for pre-drilling prediction of the target formation pore pressure in the current well. Therefore, there is an urgent need to propose a method for pre-drilling prediction of the target formation pore pressure in the current well based on logging data from adjacent wells.

[0003] Currently, many methods have been proposed to predict the pore pressure of the target formation in the current well, such as a method for predicting formation pore fluid pressure applicable to carbonate formations (CN202210040987.4), a three-dimensional formation pressure prediction method and device based on seismic data (CN202111674358.9), a formation pressure prediction method and lithologic reservoir evaluation method (CN201910996100.7), a method, device and equipment for predicting formation pressure coefficient using seismic data (CN202110292026.8), a formation pressure prediction and analysis method, device, medium and equipment (CN202110763391.2), and a formation pore pressure prediction method based on seismic data (CN201510246679.7). However, the above methods can be divided into two categories: one is to analyze formation pore pressure post-drilling using well logging data, which is obviously difficult to guide actual drilling in the field; the other is to analyze formation pore pressure pre-drilling using seismic data, but this type of method does not consider the resolution accuracy of seismic layer velocities, thus the accuracy of the obtained formation pore pressure is problematic. Therefore, it is imperative to propose a method for predicting the target formation pore pressure of the current well pre-drilling based on adjacent well logging data. Summary of the Invention

[0004] This invention provides a method for predicting the pore pressure of the target formation in the current well based on logging data from adjacent wells before drilling. First, the pore pressure of the formation in the adjacent well is calculated based on the logging data of the adjacent well. Then, the depth range of the target formation in the current well is divided. Finally, the pore pressure of the formation in each depth range of the target formation in the current well is calculated by combining the geometric orientation maps of the adjacent wells and the current well. The effectiveness of the proposed method is verified by field tests.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for predicting the pore pressure of the target formation in the current well based on logging data from adjacent wells before drilling, the operation steps of which are:

[0006] (1) Select all valid neighboring wells of the current well from the same well site. The number of valid neighboring wells should be greater than or equal to 5.

[0007] The selection of effective adjacent wells should simultaneously meet the following five conditions:

[0008] 1) Each effective adjacent well should have the same stratigraphic sequence as the current well in the depth direction;

[0009] 2) Each valid adjacent well should contain the target formation and have density logging data and sonic transit time data on the target formation;

[0010] 3) The target formation depth range of each effective adjacent well should intersect with the target formation depth range of the current well. Due to geological structure, the target formation depth range of the effective adjacent well is generally different from that of the current well. The target formation depth range of each effective adjacent well should intersect with the target formation depth range of the current well. Preferably, in actual prediction, the formation pore pressure of the current well is predicted with an intersection of 5m or more.

[0011] 4) The depth range of all valid adjacent wells in the target formation constitutes a set, and the upper and lower limits of this set should include the depth range of the target formation of the current well;

[0012] 5) The line connecting any two valid adjacent wells cannot pass through the current well. If it does, the valid adjacent well that is horizontally farther away from the current well should be discarded.

[0013] (2) Formation pore pressure prediction of effective adjacent wells

[0014] 1) Establish an effective adjacent well normal compaction trend line

[0015] Based on the lithology of each effective adjacent well, the pure mudstone formation of each effective adjacent well is identified. The sonic transit time of the pure mudstone formation under normal compaction is then screened out. That is, the sonic transit time at each depth location in the pure mudstone formation that "decreases with increasing depth" is found. Then, the selected sonic transit time scatter data is fitted into a logarithmic curve as described in equation (1) using Matlab, where the dependent variable is Δt. nWith H as the independent variable, establish the normal compaction trend line for each effective adjacent well, as shown in the following formula:

[0016] lnΔt n =lnΔt0-CH (1)

[0017] In the formula, Δt n Δt0 is the acoustic transit time at a certain depth, in μs / m; Δt0 is the acoustic transit time at a depth of zero, in μs / m; C is the compaction coefficient, dimensionless; H is the depth, in m;

[0018] 2) Obtain the formation pore pressure of each effective adjacent well.

[0019] Substituting density logging data and sonic transit time data into the Eaton formula yields the formation pore pressure for each effective adjacent well, as shown in equation (2):

[0020]

[0021] In the formula: P P P0 is the formation pore pressure, in MPa; P0 is the vertical pressure of the overlying formation, obtained by integrating the density along the depth direction. MPa; ρ is density, obtained from density logging, g / cm³. 3 ;P h The hydrostatic pressure is obtained by integrating the water density along the depth direction, in MPa; Δt n Δt is the sonic transit time on the normal compaction trend line, obtained through the normal compaction trend line equation in formula (1), μs / m; Δt is the sonic transit time in the actual well logging data, μs / m; N is the Eaton index, obtained from a designated well with measured formation pore pressure in the same well site. The measured formation pore pressure of the designated well, the vertical pressure of the overlying formation at the corresponding depth, the hydrostatic pressure, the sonic transit time on the normal trend line, and the measured sonic transit time are substituted into the following formula (3) to calculate the Eaton index:

[0022]

[0023] In the formula: P p 'P0' represents the measured formation pore pressure of the specified well, in MPa; P0' represents the vertical pressure of the overlying formation at the measured depth of the specified well, obtained by integrating the density of the specified well along the depth direction, in MPa; P h 'The hydrostatic pressure is obtained by integrating the water density along the depth direction, in MPa; Δt' n The sonic transit time on the normal compaction trend line of the specified well is obtained by formula (1) and is μs / m; Δt' is the measured sonic transit time at the measured depth of the formation pore pressure of the specified well and is μs / m.

[0024] (3) Delineate the depth range of the target formation in the current well.

[0025] Assuming the current well's target formation depth range is [h, h'], the division method is as follows:

[0026] 1) Define the effective depth range as the depth range in which the effective adjacent wells and the current well overlap in the target formation;

[0027] 2) Assume there are i effective neighboring wells, and label the effective depth range of each effective neighboring well as [h1, h2], [h3, h4], ..., [h...]. 2i-1 ,h 2i ], with depths h1, h2, ..., h 2i Sort by size (keeping only one of the equal variables) and relabel them as a1 (a1 = h), a2, ..., a u (a u =h');

[0028] 3) Construct a new depth range [a1, a2] from the minimum depth a1 and the second minimum depth a2, and observe the relationship between [a1, a2] and the effective depth ranges of each adjacent well [h1, h2], [h3, h4], ..., [h...]. 2i-1 ,h 2i The inclusion relationship of ] is used to screen out each effective adjacent well that includes [a1,a2] in the effective depth range, and form the first well group;

[0029] 4) Construct a new depth range [a2, a3] from the second minimum depth value a2 and the third minimum depth value a3. Observe the relationship between [a2, a3] and the effective depth ranges of each effective adjacent well [h1, h2], [h3, h4], ..., [h...]. 2i-1 ,h 2i Based on the inclusion relationship, the effective adjacent wells within the effective depth range of [a2, a3] are selected to form the second well group;

[0030] 5) Continue in this manner until the second largest depth value a is reached. u-1 and maximum value a u Constitutes a new depth range [a u-1 ,a u ], observe [a u-1 ,a u The effective depth ranges of each effective adjacent well [h1,h2], [h3,h4], ..., [h 2i-1 ,h 2i The inclusion relationship of ] will include the effective depth range [a u-1 ,a u Each effective adjacent well was selected to form the u-1 well group;

[0031] Preferably, the number of effective neighboring wells in each well group should be a natural number greater than or equal to 3; in steps (4) and (5), the geometric orientation map of the current well is constructed and the formation pore pressure of the target formation at each depth range of the current well is calculated when the number of effective neighboring wells in each well group is odd; if the number of effective neighboring wells in each well group is even, the effective neighboring well that is furthest from the current well in horizontal distance should be discarded.

[0032] (4) Construct a geometric orientation map of the effective adjacent wells and the current well within each well group.

[0033] Taking the j-th well group as an example, assuming that the j-th well group consists of k effective neighboring wells, the method for constructing the geometric orientation map of these k effective neighboring wells and the current well is as follows:

[0034] 1) Select key neighboring wells from effective neighboring wells

[0035] The criteria for selecting critical adjacent wells are as follows: the line connecting the critical adjacent well and the current well should divide the well site into two regions, and the number of effective adjacent wells in each region should be equal. These two regions are named Region 1 and Region 2.

[0036] 2) Name the effective adjacent wells in each region.

[0037] In Region 1, the effective neighboring wells are named sequentially from closest to furthest in terms of horizontal distance from the key adjacent well: Well No. 1, Well No. 3, ..., Well No. k-2. In Region 2, the effective neighboring wells are named sequentially from closest to furthest in terms of horizontal distance from the key adjacent well: Well No. 2, Well No. 4, ..., Well No. k-1. The k-1 effective neighboring wells in Regions 1 and 2, together with the key adjacent well, constitute the k effective neighboring wells of the j-th well group. That is to say, in Region 1, the closest horizontal well to the key adjacent well is Well No. 1, the second closest is Well No. 3, and so on; in Region 2, the closest horizontal well to the key adjacent well is Well No. 2, the second closest is Well No. 4, and so on.

[0038] 3) Connect adjacent valid wells in region 1 and region 2 and measure the distance between the connecting lines.

[0039] Connect adjacent wells 1 and 2, 3 and 4, ..., k-2 and k-1 respectively. There are a total of... This line The connecting lines will intersect with the connecting lines of key adjacent wells and the current well, respectively, and the intersection points will be defined as virtual well 1, virtual well 2, ..., For each virtual well, the distance between each virtual well and its two adjacent wells is measured. Taking virtual well No. 1 as an example, the distance L1 between virtual well No. 1 and its adjacent well No. 1, the distance L2 between virtual well No. 1 and its adjacent well No. 2, and so on are measured and denoted as L1, L2...L... k-1 ;

[0040] 4) Measure the distance between each adjacent well on the line connecting the critical neighboring well and the current well.

[0041] The distance between the critical neighbor well and the nearest virtual well is d1, and the distance between each adjacent virtual well is... The distance between the current well and the nearest virtual well is

[0042] (5) Calculate the formation pore pressure at various depths of the target formation in the current well.

[0043] Taking the j-th well group as an example, assuming that the j-th well group consists of k effective adjacent wells, the depth range of the target formation of the corresponding current well is [a j ,a j+1 ], then the current well target formation [a j ,a j+1 The calculation method for formation pore pressure within the depth range is as follows:

[0044] ① Obtain the formation pore pressure of the effective adjacent wells in the j-th well group from step (2), and then calculate the formation pore pressure of each virtual well in [a] by combining the distance between the virtual well and the corresponding two adjacent wells. j ,a j+1 The formation pore pressure within the depth range is shown in equation (4):

[0045]

[0046] In the formula: D 虚拟1 D represents the formation pore pressure of virtual well No. 1, in MPa; 虚拟2 The formation pore pressure of virtual well No. 2, in MPa; ...; for The formation pore pressure of virtual well No. 1, MPa; D1 is the formation pore pressure of adjacent well No. 1, MPa; D2 is the formation pore pressure of adjacent well No. 2, MPa; ...; D k-1 L1 represents the formation pore pressure of adjacent well k-1, in MPa; L2 represents the distance between virtual well k-1 and adjacent well k-1, in meters; L3 represents the distance between virtual well k-1 and adjacent well k-2, in meters; ...; L k-1 for The distance between virtual well number k and adjacent well number k-1, in meters;

[0047] ② Considering the distance relationship between the virtual well and the current well, the target formation of the current well is in [a j ,a j+1 The formation pore pressure within the depth range can be expressed as equation (5):

[0048]

[0049] In the formula: P j For the current well target formation in [a j ,a j+1 Formation pore pressure within the depth range, MPa; D a D represents the formation pore pressure of the critical adjacent well, in MPa; 虚拟1 D represents the formation pore pressure of virtual well No. 1, in MPa; 虚拟2 The formation pore pressure of virtual well No. 2, in MPa; ...; for Formation pore pressure of virtual well No. 1, MPa; d1 is the distance between the critical adjacent well and virtual well No. 1, m; d2 is the distance between virtual well No. 1 and virtual well No. 2, m; ...; for The distance between the virtual well and the current well, in meters;

[0050] By repeating the above method, the target formation of the current well can be obtained at various depth ranges [a1,a2], [a2,a3], ..., [a...]. j ,a j+1 ]……、[a u-1 ,a u Formation pore pressure;

[0051] (6) Assemble the current well formation pore pressure obtained in step (5) according to depth to obtain the current well target formation pore pressure.

[0052] The depth ranges of the target formation in the current well are [a1,a2], [a2,a3], ..., [a...]. j ,a j+1 ]……、[a u-1 ,a u The formation pore pressures are simply combined in order of depth to obtain the pore pressure of the target formation in the current well.

[0053] The second aspect of this invention provides a field test method for testing the pore pressure of the target formation in the current well, verifying the accuracy of the above-mentioned method for predicting the pore pressure of the target formation in the current well based on logging data from adjacent wells before drilling. The operation steps are as follows:

[0054] Step 1: Deploy the fluid velocity sensor and fluid pressure sensor

[0055] A fluid velocity sensor is placed on the inner wall of the target formation wellbore to monitor the radial velocity of the fluid flowing between the wellbore and the formation; a fluid pressure sensor is placed on the drill bit to monitor the formation pore pressure at the stop drilling location.

[0056] Step 2: Test the pore pressure of the target formation in the current well.

[0057] (1) Stop drilling when the current well reaches any depth in the target formation;

[0058] (2) After drilling is stopped, adjust the drilling fluid density sequentially, with each adjustment increment being 0.02 g / cm³. 3 Each adjusted drilling fluid density should be maintained for 30 minutes. Within 30 minutes, record the fluid velocity sensor monitoring value corresponding to the current drilling fluid density and extract the fluid radial velocity data. Plot the curve of the fluid radial velocity corresponding to the current drilling fluid density over time.

[0059] (3) Observe the curve of the radial velocity of the fluid changing with time after each adjustment of the drilling fluid density. When the radial velocity of the fluid is close to 0 within 30 minutes and the radial velocity of the fluid does not change with time, record the drilling fluid density ρ0 and the fluid pressure sensor monitoring value P0 for this time.

[0060] (4) Maintain the drilling fluid density at the ρ0 level for 24 hours, record the fluid pressure sensor reading P0′ after 24 hours, and compare P0 and P0′. If the difference between the two is less than 3%, then... This refers to the measured formation pore pressure at any depth in the target formation of the current well.

[0061] Step 3: Secondary confirmation of the pore pressure test values ​​of the current well target formation

[0062] (1) Condition 1: Shut down all adjacent wells within 1 km of the current well, and measure the pore pressure P1 at any depth of the target formation of the current well according to step 2;

[0063] (2) Condition 2: Shut down all adjacent wells within 2 kilometers of the current well, and measure the pore pressure P2 at any depth of the target formation of the current well according to step 2;

[0064] (3) Condition 3: Shut down all adjacent wells within 3 kilometers of the current well, and measure the pore pressure P3 at any depth of the target formation of the current well according to step 2;

[0065] (4) Condition 4: Shut down all adjacent wells within 4 kilometers of the current well, and measure the pore pressure P4 at any depth of the target formation of the current well according to step 2;

[0066] (5) Condition 5: Shut down all adjacent wells within 5 kilometers of the current well, and measure the pore pressure P5 at any depth of the target formation of the current well according to step 2;

[0067] (6) Compare P1, P2, P3, P4, and P5 obtained under the above five working conditions at the same depth with P0 obtained in step 2. If the error between the two is within 5%, it indicates that the influence of neighboring wells on the pore pressure of the target formation of the current well is small, and secondary confirmation can be performed. This represents the measured value of the pore pressure in the target formation of the current well.

[0068] Step 4: Verify the effectiveness of the above method for predicting the pore pressure of the target formation in the current well based on adjacent well logging data before drilling.

[0069] (1) Verify the prediction method using measured formation pore pressure from effective adjacent wells.

[0070] Comparing the measured formation pore pressure values ​​of the effective adjacent wells with the predicted values ​​of the above method, if the error is within 3%, it indicates that the above method can meet the requirements of the field project.

[0071] (2) Verify the prediction method using the current well measured formation pore pressure.

[0072] If the measured formation pore pressure of the current well is compared with the predicted value of the above method, and the error is within 3%, it indicates that the above method can meet the requirements of the field project.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] 1. This invention proposes a method for predicting the pore pressure of the target formation in the current well based on logging data from adjacent wells before drilling. By comparing with field tests, it can be seen that the prediction accuracy of this method exceeds 95%, which is about 20% higher than that of conventional methods.

[0075] 2. This invention proposes a field test method for testing the pore pressure of the target formation in the current well. Compared with the oil testing method in the production stage, the consistency rate is 95.9%, which solves the problem of difficulty in testing the pore pressure of the target formation in the drilling stage. Attached Figure Description

[0076] Figure 1 This is a schematic diagram illustrating the depth range of the target formation in the current well according to the present invention;

[0077] Figure 2 This is a geometric orientation diagram of the effective adjacent wells and the current well in the j-th well group of the present invention;

[0078] Figure 3 This is a schematic diagram of a field test for the present invention. In the diagram: 1. Drill bit; 2. Wellbore; 3. Fluid velocity sensor; 4. Fluid pressure sensor;

[0079] Figure 4 This is a list of basic parameters for the effective adjacent well AT2 in Embodiment 1 of the present invention;

[0080] Figure 5 This is a list of basic parameters for the effective adjacent well SY1 in Embodiment 1 of the present invention;

[0081] Figure 6 Here is a list of basic parameters for the effective adjacent well S51 in Embodiment 1 of the present invention;

[0082] Figure 7 This is a list of basic parameters for the effective adjacent well WG1 in Embodiment 1 of the present invention;

[0083] Figure 8 This is a list of basic parameters for the effective adjacent well AT3 in Embodiment 1 of the present invention;

[0084] Figure 9 This is the formation pore pressure prediction result of the effective adjacent well AT2 in Embodiment 1 of the present invention;

[0085] Figure 10 This is the formation pore pressure prediction result of the effective adjacent well SY1 in Embodiment 1 of the present invention;

[0086] Figure 11 This is the prediction result of formation pressure porosity in the adjacent well S51 of Embodiment 1 of the present invention;

[0087] Figure 12 This is the formation pore pressure prediction result of the effective adjacent well WG1 in Embodiment 1 of the present invention;

[0088] Figure 13 This is the formation pore pressure prediction result of the effective adjacent well AT3 in Embodiment 1 of the present invention;

[0089] Figure 14 This refers to the seismic layer velocity data of well AT4 in Embodiment 3 of the present invention.

[0090] Figure 15 This is the formation pore pressure prediction result based on layer velocity in well AT4 in Embodiment 3 of the present invention;

[0091] Figure 16 This is a comparison chart of the results of embodiments 1, 2 and 3 of the present invention. Detailed Implementation

[0092] The details of the present invention can be more clearly understood by referring to the accompanying drawings and the description of specific embodiments. However, the specific embodiments of the present invention described herein are for illustrative purposes only and should not be construed as limiting the invention in any way. Under the teachings of this invention, those skilled in the art can conceive of any possible modifications based on the invention, and these should all be considered to fall within the scope of the invention.

[0093] Example 1:

[0094] Example 1 describes the prediction of pore pressure in the target formation of well AT4 in block JZ using the method described in this invention. The target formation depth is 2000m-3000m.

[0095] (1) Based on the screening criteria for effective adjacent wells, the effective adjacent wells of AT4 are selected as AT2, SY1, S51, SY302, WG1, and AT3.

[0096] (2) The effective depth ranges of each effective adjacent well are [2000, 2650], [2450, 3000], [2000, 3000], [2500, 3000], [2000, 2950], and [2200, 2800]; for example Figure 1 As shown, the current method for dividing the target formation depth range of well AT4 can be divided into 7 depth ranges: [2000, 2200], [2200, 2450], [2450, 2500], [2500, 2650], [2650, 2800], [2800, 2950], [2950, ​​3000], corresponding to 7 well groups. Well group 1: AT2 well, S51 well, WG1 well; Well group 2: AT2 well, S... Wells 51, WG1, and AT3; Well Group 3: AT2, SY1, S51, WG1, and AT3; Well Group 4: AT2, SY1, S51, SY302, WG1, and AT3; Well Group 5: SY1, S51, SY302, WG1, and AT3; Well Group 6: SY1, S51, SY302, and WG1; Well Group 7: SY1, S51, and SY302.

[0097] (3) The field-measured formation pore pressure depths of well AT4 are 2465m and 2485m. Therefore, it is necessary to calculate the formation pore pressure of wells AT2, SY1, S51, WG1, and AT3 within the depth range [2450, 2500] in the third well group, and then obtain the predicted values ​​of well AT4 at 2465m and 2485m. The basic parameters for predicting the formation pore pressure of wells AT2, SY1, S51, WG1, and AT3 are derived from well logging data, including H, ρ, and Δt, see [link to documentation]. Figures 4-8 According to formula (1), the normal compaction trend line equations for wells AT2, SY1, S51, WG1, and AT3 are obtained as lnΔt=0.0009H+2.8236, lnΔt=-0.0008H+7.2207, lnΔt=0.0056H-8.4898, lnΔt=-0.00006H+5.0676, and lnΔt=-0.0017H+9.5117. Before drilling well AT4, the only well in this well field with measured formation pore pressure data was well SY302. Therefore, the basic parameters at the measured formation pore pressure depth of well SY302 are H'=3500m and ρ'=2.371g / cm. 3 Δt'=263.504μs / m, Δt' n =255.325μs / m, P pSubstituting '=35.93MPa into formula (3), the Eaton index of this well site is obtained as 1.08; according to formula (2), the formation pore pressures of wells AT2, SY1, S51, WG1, and AT3 are obtained, see Figures 9-13 ;

[0098] (4) Construct geometric azimuth maps of well AT4 with wells AT2, SY1, S51, WG1, and AT3, see [link to map]. Figure 2 In the figure, the current well is AT4, the key adjacent well is AT2, and the adjacent wells 1, 2, 3 and 4 are SY1, S51, WG1 and AT3, respectively. The distances are d1 = 7.1 km, d2 = 7.6 km, d3 = 7.3 km, L1 = 8 km, L2 = 7 km, L3 = 7.5 km and L4 = 6.8 km. According to formulas (4) to (6), the formation pore pressures of virtual wells 1 and 2 at depths of 2465 m and 2485 m are 24.1 MPa and 24.7 MPa, respectively. According to formula (7), the formation pore pressures of well AT4 at depths of 2465 m and 2485 m are 23.9 MPa and 24.3 MPa, respectively.

[0099] Example 2:

[0100] Example 2 is a field test used to obtain the measured formation pore pressure at depths of 2465m and 2485m in well AT4.

[0101] Following step 1, when drilling AT4 well to a depth of 2465m, a fluid velocity sensor was placed on the well wall and a fluid pressure sensor was placed on the drill bit.

[0102] Following step 2, drilling was stopped at a depth of 2465m, at which point the drilling fluid density was 1.3g / cm³. 3 0.02 g / cm 3 The drilling fluid density was adjusted by decreasing the drilling fluid density to 0.94 g / cm³. 3 At that time, the radial velocity of the fluid was monitored to be close to 0 within 30 minutes and remained essentially unchanged over time. The drilling fluid density at this point was recorded as ρ1 = 0.94 g / cm³. 3 With the fluid pressure sensor data P0 = 23.5 MPa, and the drilling fluid density ρ0 maintained for 24 hours, the fluid pressure sensor monitoring value P0' = 22.9 MPa, with an error of 2.5% compared to P0;

[0103] Following step 3, the formation pore pressures at 2465m under five different operating conditions were measured to be 24.3 MPa, 24.1 MPa, 23.5 MPa, 22.9 MPa, and 24 MPa, respectively. The errors compared to P0 were all less than 5%. Based on this, the measured formation pore pressure at a depth of 2450m in well AT4 was confirmed to be...

[0104] Following the same method, drilling was stopped at a depth of 2485m on AT4 well, and the drilling fluid density was adjusted to 0.97g / cm³. 3 At that time, the radial velocity of the fluid was monitored to be close to 0 within 30 minutes and remained essentially unchanged over time. The drilling fluid density ρ'0 was recorded as 0.97 g / cm³ at this point. 3 With the fluid pressure sensor reading P1 = 24.5 MPa, and maintaining the drilling fluid density ρ'0 for 24 hours, the fluid pressure sensor reading P1' = 23.9 MPa, with an error of 2.4% compared to P1. Following step 3, the formation pore pressure at 2485m was measured under five different conditions: 25.3 MPa, 25.1 MPa, 25.5 MPa, 24.9 MPa, and 24.7 MPa, with errors of less than 5% compared to P1. Based on this, the measured formation pore pressure at a depth of 2485m in well AT4 is confirmed to be...

[0105] Example 3:

[0106] Example 3 is a pre-drilling prediction of pore pressure in the target formation of well AT4 based on seismic layer velocity. The seismic layer velocity data of the target formation in well AT4 (see...) Figure 14 Substituting the values ​​into the Fillippone model (model source: Zhou Donghong, Xiong Xiaojun. A high-precision formation pressure prediction method [J]. Petroleum Geophysical Exploration, 2014, 49(02):344-348+222.), the pore pressure of the target formation in well AT4 can be obtained. See Figure 15 .

[0107] Example 4:

[0108] Example 4 uses the oil testing method during the production stage (method source: He Bin, Gu Xiaogang, Li Fengchang. Oil testing technology for shale oil in Anshen 1 well [J]. Oil and Gas Well Testing, 2015, 24(01):63-64+78.) to obtain the formation pore pressures of well AT4 at depths of 2465m and 2485m, which are 22.5MPa and 24.9MPa, respectively.

[0109] Comparing the formation pore pressure results of Examples 1 and 2, see... Figure 16 It can be seen that the prediction method described in this invention has an accuracy of 98.3%; comparing the formation pore pressure results of Examples 2 and 3, see... Figure 16 It can be seen that the prediction accuracy of the Fillippone model is 77.4%; comparing the prediction accuracy of the two methods mentioned above, it can be seen that the method described in this invention improves the prediction accuracy by 20.9% compared with the Fillippone model.

[0110] Comparing the formation pore pressure results of Examples 2 and 4, it can be seen that the field test method described in this invention has a consistency rate of 95.9% with the oil testing method, indicating that the field test method described in this invention can solve the problem of difficulty in testing the pore pressure of the target formation during the drilling stage.

Claims

1. A method for predicting the pore pressure of the target formation in the current well before drilling based on logging data from adjacent wells, characterized in that, The specific operating steps are as follows: (1) Select all valid neighboring wells of the current well from the same well site. There are i valid neighboring wells in total, i≥5; (2) Formation pore pressure prediction of effective adjacent wells; (3) Delineate the depth range of the target formation in the current well. Assume the current well target formation depth range is [h, The division method is as follows: 1) Define the effective depth range as the depth range in which the effective adjacent wells and the current well overlap in the target formation; 2) Mark the effective depth range of each effective adjacent well as [h1, h2], [h3, h4], ..., [h 2i-1 ,h 2i ], with depths h1, h2, ..., h 2i Sort by size and relabel as a1, a2, ..., a u Among them, only one variable with the same depth value is retained, a1=h, a u = ; 3) Construct a new depth range [a1, a2] from the minimum depth value a1 and the second minimum depth value a2, and observe the relationship between [a1, a2] and the effective depth ranges of each adjacent well [h1, h2], [h3, h4], ..., [h...]. 2i-1 ,h 2i The inclusion relationship of ] is used to screen out all effective adjacent wells whose effective depth range includes [a1,a2], forming the first well group; 4) Construct a new depth range [a2, a3] from the second minimum depth value a2 and the third minimum depth value a3. Observe the relationship between [a2, a3] and the effective depth ranges of each effective adjacent well [h1, h2], [h3, h4], ..., [h...]. 2i-1 ,h 2i Based on the inclusion relationship, all effective adjacent wells whose effective depth range includes [a2, a3] are selected to form the second well group; 5) Continue in this manner until the second largest depth value a is reached. u-1 and maximum value a u Constitutes a new depth range [a u-1 ,a u ], observe [a u-1 ,a u The effective depth ranges of each effective adjacent well [h1,h2], [h3,h4], ..., [h 2i-1 ,h 2i The inclusion relationship of ] will include the effective depth range [a u-1 ,a u All valid adjacent wells were selected to form well group u-1; (4) Construct a geometric orientation map of the effective neighboring wells and the current well within each well group. Taking the j-th well group as an example, assuming that the j-th well group consists of k effective neighboring wells, the method for constructing the geometric orientation map of these k effective neighboring wells and the current well is as follows: 1) Select key neighboring wells from the effective neighboring wells The criteria for selecting critical adjacent wells are: the line connecting the critical adjacent well and the current well should be able to divide the well site into two regions, and the number of effective adjacent wells in each region should be equal. These two regions are named Region 1 and Region 2. 2) Name the effective adjacent wells in each region. In Region 1, the effective neighboring wells are named sequentially from closest to farthest from the critical adjacent well, namely, Adjacent Well No. 1, Adjacent Well No. 3, ..., Adjacent Well No. k-2, according to their horizontal distance from the critical adjacent well. In Region 2, the effective neighboring wells are named sequentially from closest to farthest from the critical adjacent well, namely, Adjacent Well No. 2, Adjacent Well No. 4, ..., Adjacent Well No. k-1, together with the critical adjacent well, constitute the k effective neighboring wells of the j-th well group. 3) Connect adjacent valid wells in region 1 and region 2 and measure the distance between the connecting lines. Connect adjacent wells 1 and 2, 3 and 4, ..., k-2 and k-1 respectively. There are a total of... This line The connecting lines will intersect with the connecting lines of key adjacent wells and the current well, respectively, and the intersection points will be defined as virtual well 1, virtual well 2, ..., For each virtual well, the distance between each virtual well and its two adjacent wells needs to be measured. Taking virtual well number 1 as an example, the distance between virtual well number 1 and its adjacent well number 1 needs to be measured. Distance between virtual well No. 1 and adjacent well No. 2 And so on, denoted as follows: , … ; 4) Measure the distances between each adjacent well on the line connecting the critical neighboring well and the current well. The distance between the critical adjacent well and the nearest virtual well is measured as follows: The distance between each adjacent virtual well is , … The distance between the current well and the nearest virtual well is ; (5) Calculate the formation pore pressure at various depths of the target formation in the current well. Taking the j-th well group as an example, assuming that the j-th well group consists of k effective adjacent wells, the depth range of the target formation of the corresponding current well is [a j ,a j+1 ], then the current well target formation [a j ,a j+1 The calculation method for formation pore pressure within the depth range is as follows: ① Obtain the formation pore pressure of the effective adjacent wells in the j-th well group from step (2), and then calculate the formation pore pressure of each virtual well in [a] by combining the distance between the virtual well and the corresponding two adjacent wells. j ,a j+1 The formation pore pressure within the depth range is given by the following formula: In the formula: for Formation pore pressure of virtual well No. , MPa; The formation pore pressure of adjacent well k-1 is in MPa. ② Considering the distance relationship between the virtual well and the current well, the target formation of the current well is in [a j ,a j+1 The formation pore pressure within a certain depth range is expressed by the following formula: In the formula: For the current well target formation in [a j ,a j+1 Formation pore pressure within the depth range, MPa; The formation pore pressure of the critical adjacent well, in MPa; By repeating the above method, the target formation of the current well can be obtained at various depth ranges [a1,a2], [a2,a3], ..., [a...]. j ,a j+1 ]……、[a u-1 ,a u Formation pore pressure; (6) Assemble the formation pore pressure of the current well obtained in step (5) according to the depth to obtain the target formation pore pressure of the current well.

2. The method for predicting the pore pressure of the target formation in the current well based on logging data from adjacent wells before drilling, as described in claim 1, is characterized in that... The screening of effective adjacent wells in step (1) should simultaneously meet the following 5 conditions: 1) Each effective adjacent well should have the same stratigraphic sequence as the current well in the depth direction; 2) Each effective adjacent well should contain the target formation and have density logging data and sonic transit time data on the target formation; 3) The target formation depth range of each effective adjacent well should overlap with the target formation depth range of the current well; 4) The depth ranges of all valid adjacent wells in the target formation constitute a set, and the upper and lower limits of this set should include the depth range of the target formation of the current well; 5) The line connecting any two valid adjacent wells cannot pass through the current well. If it does, the valid adjacent well that is horizontally farther away from the current well should be discarded.

3. The method for predicting the target formation pore pressure in the current well based on adjacent well logging data before drilling, as described in claim 2, is characterized in that... In step (1), 3) there is an intersection, which means that the target formation depth set of each effective adjacent well should intersect with the target formation depth set of the current well by 5m or more.

4. The method for predicting the pore pressure of the target formation in the current well based on logging data from adjacent wells before drilling, as described in claim 1, is characterized in that... The specific steps for predicting the formation pore pressure of effective adjacent wells in step (2) are as follows: 1) Establish an effective adjacent well normal compaction trend line Based on the lithology of each effective adjacent well, the pure mudstone formation of each effective adjacent well was identified. The sonic transit time of the pure mudstone formation under normal compaction was then selected. Specifically, the sonic transit time at depths where "sonic transit time decreases with increasing depth" was identified within the pure mudstone formation. Then, the selected sonic transit time scatter plot data was fitted into a logarithmic curve using Matlab, where the dependent variable is... With H as the independent variable, establish the normal compaction trend line for each effective adjacent well, as shown in the following formula: In the formula, Let be the acoustic transit time at a certain depth, in μs / m; is the acoustic transit time at depth zero, μs / m; C is the compaction coefficient, dimensionless; H is the depth, m; 2) Obtain the formation pore pressure of each effective adjacent well. Substituting density logging data and sonic transit time data into the Eaton formula yields the formation pore pressure for each effective adjacent well, as shown in the following formula: In the formula: Formation pore pressure, MPa; The density is obtained by integrating along the depth direction to represent the vertical pressure of the overlying strata. MPa; Density, obtained from density logging, g / cm³ 3 ; The hydrostatic pressure is obtained by integrating the water density along the depth direction, in MPa. The acoustic transit time along the normal compaction trend line is obtained through the equation of the normal compaction trend line, in μs / m. is the sonic transit time in actual well logging data, in μs / m; N is the Eaton exponent.

5. The method for predicting the pore pressure of the target formation in the current well based on logging data from adjacent wells before drilling, as described in claim 4, is characterized in that... In step (2), the Eaton index is obtained from a designated well within the same well site with measured formation pore pressure. The measured formation pore pressure of the designated well, the vertical pressure of the overlying formation at the corresponding depth, the hydrostatic pressure, the sonic transit time on the normal trend line, and the measured sonic transit time are substituted into the following formula to calculate the Eaton index: In the formula: The measured value of formation pore pressure for a specified well, in MPa; The vertical pressure of the overlying formation at the measured depth of the formation pore pressure of a specified well is obtained by integrating the density of the specified well along the depth direction, in MPa. The hydrostatic pressure is obtained by integrating the water density along the depth direction, in MPa. The sonic transit time along the normal compaction trend line of a specified well is obtained through the equation of the normal compaction trend line, in μs / m. The measured sonic transit time at the depth of the well's formation pore pressure is expressed in μs / m.

6. The method for predicting the pore pressure of the target formation in the current well based on logging data from adjacent wells before drilling, as described in claim 1, is characterized in that... In step (3), the number of effective neighboring wells constituting each well group should be a natural number greater than or equal to 3; in steps (4) and (5), the geometric orientation map of the current well and the formation pore pressure of the target formation at each depth range of the current well are constructed with the number of effective neighboring wells in each well group being odd; if the number of effective neighboring wells in each well group is even, the effective neighboring well that is furthest from the current well in horizontal distance should be discarded.

7. A field test method for testing the pore pressure of the target formation in the current well, verifying the accuracy of the method for predicting the pore pressure of the target formation in the current well based on logging data from adjacent wells as described in any one of claims 1-6, characterized in that, The specific operating steps are as follows: Step 1: Deploy the fluid velocity sensor and fluid pressure sensor A fluid velocity sensor is placed on the inner wall of the target formation wellbore to monitor the radial velocity of the fluid flowing between the wellbore and the formation; a fluid pressure sensor is placed on the drill bit to monitor the formation pore pressure at the stop drilling location. Step 2: Test the pore pressure of the target formation in the current well. (1) Stop drilling when the current well reaches any depth in the target formation; (2) After drilling stops, adjust the drilling fluid density in sequence, record the fluid velocity sensor monitoring value corresponding to the drilling fluid density within a certain time range, extract the fluid radial velocity data, and plot the curve of the change of fluid radial velocity with time corresponding to the drilling fluid density. (3) Observe the curve of the radial velocity of the fluid versus time after each adjustment of the drilling fluid density. When the radial velocity of the fluid approaches 0 within 30 minutes and the radial velocity of the fluid does not change much with time, record the drilling fluid density for this adjustment. and fluid pressure sensor monitoring values ; (4) Maintain drilling fluid density at Horizontally, record the fluid pressure sensor readings after 24 hours. ,Compare and If the difference between the two is less than 3%, then This refers to the measured formation pore pressure at any depth in the target formation of the current well. Step 3: Secondary confirmation of the pore pressure test values ​​of the current well target formation (1) Shut down all adjacent wells within different kilometers of the current well to form at least 5 working conditions, and measure the pore pressure at any depth of the target formation of the current well under different working conditions according to step 2; (2) Compare the pore pressure obtained at the same depth under different working conditions with the pore pressure obtained in step 2. If the errors of both are within 5%, it indicates that the influence of neighboring wells on the pore pressure of the current well's target formation is relatively small, and secondary confirmation is possible. This represents the measured value of the pore pressure in the target formation of the current well. Step 4: Verify the effectiveness of the above method for predicting the pore pressure of the target formation in the current well based on adjacent well logging data before drilling. (1) Verify the prediction method using measured formation pore pressure from adjacent wells. Comparing the measured formation pore pressure values ​​of the effective adjacent wells with the predicted values ​​of the above method, if the error is within 3%, it indicates that the above method can meet the requirements of the field project. (2) Verify the prediction method using the measured formation pore pressure in the current well. If the measured formation pore pressure of the current well is compared with the predicted value of the above method, and the error is within 3%, it indicates that the above method can meet the requirements of the field project.

8. The field test method for testing the pore pressure of the target formation in a current well according to claim 7, characterized in that, In step 2(2), when adjusting the drilling fluid density, the adjustment increment is 0.02 g / cm³ each time. 3 Each adjusted drilling fluid density should be maintained for 30 minutes. Within 30 minutes, record the fluid velocity sensor monitoring value corresponding to the current drilling fluid density and extract the fluid radial velocity data.

9. A field test method for testing the pore pressure of a target formation in a current well, as described in claim 7, is characterized in that... In step 3(1), five working conditions are formed, namely: (1) Condition 1: Shut down all adjacent wells within 1 km of the current well, and measure the pore pressure at any depth of the target formation of the current well according to step 2. ; (2) Condition 2: Shut down all adjacent wells within 2 kilometers of the current well, and measure the pore pressure at any depth of the target formation of the current well according to step 2. ; (3) Condition 3: Shut down all adjacent wells within 3 kilometers of the current well, and measure the pore pressure at any depth of the target formation of the current well as in step 2. ; (4) Condition 4: Shut down all adjacent wells within a 4-kilometer radius of the current well, and measure the pore pressure at any depth of the target formation of the current well as in step 2. ; (5) Condition 5: Shut down all adjacent wells within 5 kilometers of the current well, and measure the pore pressure at any depth of the target formation of the current well as in step 2. .

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