Calculation method of the influence of fault and erosion line on formation pressure

Abstract

The present invention discloses a method for calculating the influence value of faults and erosion lines on formation pressure, including: a. collecting data; b. using the fault drop and the fault disappearing layer as classification parameters to classify the faults in the region, and after classification, presetting the influence coefficients of each level of faults on formation pressure according to the fault level, and presetting the influence coefficients of the erosion line on formation pressure; c. establishing a calculation model for the influence value of faults and erosion lines on formation pressure; d. adjusting the preset influence coefficients of each level of faults on formation pressure and the influence coefficients of the erosion line on formation pressure in a graded manner; finally, substituting the influence coefficient adjusted when the correlation coefficient is the highest into the calculation model, and obtaining a calculation formula for the influence value of faults and erosion lines on formation pressure; e. using the distance between the designed well and the fault and erosion line, combined with the calculation formula obtained in step d, to calculate the influence value of formation pressure. The present invention realizes the quantitative calculation of the influence value of formation pressure, can obtain accurate influence values, and provides important technical support for the prediction of formation pressure coefficient in drilling geological design.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploration and development, and relates to a method for calculating the influence value of faults and erosion lines on formation pressure. The method mainly predicts the formation pressure coefficient of a designed well through the calculated influence value. Background Art

[0002] The prediction of the formation pressure coefficient of the design well is an important part of the drilling geological design. The main method at present is to refer to the formation pressure data measured in the adjacent wells around the design well. This method has a certain applicability, but the value is relatively fixed and the accuracy is not high.

[0003] The results of shale gas exploration in Sichuan and Chongqing show that some geological parameters have a great impact on formation pressure, especially faults and erosion. However, their impact is relatively complex and cannot be quantified. It is specifically reflected in the following two aspects:

[0004] 1. The impact of geological factors on formation pressure cannot be measured and can only be reflected indirectly based on the high or low test production of a single well.

[0005] 2. The weight of the impact of different geological factors on formation pressure cannot be determined.

[0006] This makes it difficult to effectively calculate the geological design of drilling. Therefore, it is necessary to develop new technologies to solve this technical problem. Summary of the invention

[0007] The purpose of the present invention is to overcome the above technical problems existing in the prior art and provide a method for calculating the influence of faults and erosion lines on formation pressure. The present invention realizes the quantitative calculation of the influence of formation pressure and can obtain accurate influence values, which provides important technical support for the prediction of formation pressure coefficient in drilling geological design.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] A method for calculating the influence of faults and erosion lines on formation pressure comprises the following steps:

[0010] a. Collect well logging, fault, erosion line and formation pressure test data of the formation in the area around the designed well;

[0011] b. Based on the fault data of the formation, the fault drop and the fault disappearance layer upward are used as classification parameters to classify the faults in the area. After classification, the influence coefficients of each level of fault on the formation pressure are preset according to the fault grade, and the influence coefficient of the erosion line on the formation pressure is preset at the same time;

[0012] c. According to the shortest distance between the drilled well and the fault and erosion line, combined with the preset influence coefficients of each level of fault on the formation pressure and the influence coefficients of the erosion line on the formation pressure, a calculation model for the influence value of the fault and erosion line on the formation pressure is established;

[0013] d. Calculate the effective vertical pressure of the formation using the vertical depth and logging density data of the wells that have been drilled in the area, and combine the formation pressure test data of the wells that have been drilled. Through correlation analysis, with a high correlation coefficient as the goal, adjust the influence coefficients of the preset faults at all levels on the formation pressure and the influence coefficients of the erosion line on the formation pressure in stages; finally, substitute the influence coefficients of the faults at all levels on the formation pressure and the influence coefficients of the erosion line on the formation pressure adjusted when the correlation coefficient is the highest into the calculation model, and obtain the calculation formula for the influence value of the faults and the erosion line on the formation pressure;

[0014] e. Use the distance between the designed well and the fault and erosion line, combined with the calculation formula obtained in step d, to calculate the formation pressure impact value.

[0015] In the step b, a fault influence threshold is set to correct the influence coefficient of each level of fault on the formation pressure.

[0016] The fault impact threshold includes the fault drop level impact threshold and the fault upward disappearance level impact threshold.

[0017] The fault impact threshold is obtained based on the lower limit of the level of impact of the fault on the formation pressure in regional research results.

[0018] In step b, the faults in the region are classified using a two-dimensional model, and the method is as follows:

[0019] The classification of fault drop is:

[0020] D={D1,D2,D3……D m} (1)

[0021] In formula (1), D is the fault drop level, and m is the number of fault drop levels;

[0022] The classification of the layers disappearing upward along the fault is as follows:

[0023] U={U1,U2,U3……U n} (2)

[0024] In formula (2), U is the level of the horizon disappearing upwards on the fault, and n is the number of levels of the horizon disappearing upwards on the fault;

[0025] The fault drop and the fault disappearance level classification are combined into a two-dimensional fault level C m×n ,but:

[0026]

[0027] In step b, the influence coefficient of each level of fault on the formation pressure is preset as E m×n ,but:

[0028]

[0029] In step b, the threshold value of the fault drop level is j, the threshold value of the fault disappearing upward is k, and the influence coefficient of each level of fault on the formation pressure after correction is E' m×n ,but:

[0030]

[0031] The method for establishing the calculation model in step c is:

[0032] First, based on the wells and fault data in the area, the shortest distance between the wells and faults at all levels is extracted. m×n ,as follows:

[0033]

[0034] Then extract the shortest distance S between the drilled well and the erosion line D , then the established calculation model is:

[0035]

[0036] In formula (7), P E is the influence of fault and erosion line on formation pressure, E D It is the influence coefficient of the preset erosion line on the formation pressure.

[0037] In step d, the calculation method of the effective vertical pressure of the formation is:

[0038] P ％ =∑(ρ-1)gH (8)

[0039] In formula (8), P v is the effective vertical pressure of the formation, ρ is the logging density, and H is the vertical depth of the formation.

[0040] In step d, the calculation formula for the influence of faults and erosion lines on formation pressure is obtained by:

[0041] First, the formation pressure test value of the drilled well is obtained according to the formation pressure test data of the drilled well, and then the difference is calculated according to the effective vertical pressure of the formation and the obtained formation pressure test value, as follows:

[0042] ΔP=P v -P m 9)

[0043] In formula (9), ΔP is the difference between the effective vertical pressure of the formation and the measured formation pressure, P m is the formation pressure test value;

[0044] Then the difference between the effective vertical pressure of the formation and the formation pressure test value ΔP and the influence of the fault and erosion line on the formation pressure P E To perform correlation analysis, press E 11 >E 12 >…>E 1k >E 21 >…>E jk >E D The influence coefficients of the preset faults and the influence coefficients of the erosion lines on the formation pressure are adjusted step by step from high to low priority, so that the correlation coefficient reaches the highest value, and the difference ΔP between the effective vertical pressure of the formation and the test value of the formation pressure and the influence value P of the fault and the erosion line on the formation pressure are calculated. E The correlation formula is used as the influence value correction formula:

[0045] ΔP=f(P E ) (10)

[0046] Finally, the influence coefficients of faults at all levels adjusted when the correlation coefficient is the highest and the influence coefficients of erosion lines on the formation pressure are substituted into formula (7), and then formula (7) is substituted into formula (10) to obtain the calculation formula for the influence values ​​of faults and erosion lines on the formation pressure:

[0047]

[0048] P E is the impact of faults and erosion lines on formation pressure.

[0049] The advantages of adopting the present invention are:

[0050] 1. The present invention first classifies the faults in the region in two dimensions according to the drop and the layer that disappears upward. By presetting the influence coefficient of the fault and erosion line on the formation pressure, and combining the distance between the well and the fault and erosion line, a calculation model for the formation pressure influence value is established. Combined with the drilling data in the region, by setting a reasonable fault impact threshold, and adopting a graded adjustment and step-by-step matching method to reversely deduce the influence coefficient of the real fault and erosion line on the formation pressure, the formation pressure influence value calculation method is obtained by integration. Compared with the prior art, the present invention establishes for the first time a calculation method for the influence value of faults and erosion lines on formation pressure, and realizes the quantitative calculation of the formation pressure influence value. In addition, the method is calibrated with formation pressure test data to ensure the reliability of the method, which provides important technical support for the prediction of formation pressure coefficient in drilling geological design.

[0051] 2. The present invention adopts a hierarchical adjustment and step-by-step matching method, which effectively solves the problem of difficult weight allocation caused by multiple fault levels. The setting of the fault drop level impact threshold and the fault upward disappearance level impact threshold makes the method more controllable and applicable, and makes it more accurate.

[0052] 3. The present invention sets an impact threshold, which is the lower limit of the level of impact of the fault on the formation pressure. The impact threshold is determined by the results of regional geological research, and the guarantee method is consistent with the regional geological understanding.

[0053] 4. The present invention aims to optimize the correlation between the difference ΔP between the effective vertical pressure of the formation and the test value of the formation pressure and the influence value PE of the fault and erosion line on the formation pressure. The preset influence coefficient is adjusted in levels, first high and then low, first fault and then erosion line, and the best influence coefficient (including the influence coefficients of various faults in the area) is selected, achieving the optimal solution under multiple unknown parameter conditions, and then realizing quantitative calculation.

[0054] 5. The present invention is relatively simple to apply and adjust, and can be widely used in the process of drilling geological design. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flow chart of Example 1.

[0056] Figure 2 This is a schematic diagram of the correlation analysis between the formation pressure impact value and the pressure difference in Example 2. DETAILED DESCRIPTION

[0057] Example 1

[0058] The present invention discloses a method for calculating the influence of fault and erosion line on formation pressure. Figure 1 As shown, it includes the following steps:

[0059] a. Collect well logging, fault, erosion line and formation pressure test data of the formation in the area around the designed well.

[0060] b. Based on the logging, fault, erosion line and formation pressure test data of the formation collected in step a, a two-dimensional model is used to classify the faults in the area using the fault drop and the layer where the fault disappears upward as classification parameters. After classification, the influence coefficient of each level of fault on the formation pressure is preset according to the fault grade, and the influence coefficient of the erosion line on the formation pressure is also preset.

[0061] Specifically, the method of classifying the faults in the region using the two-dimensional model is as follows:

[0062] The classification of fault drop is:

[0063] D={D1,D2,D3……D m} (1)

[0064] In formula (1), D is the fault drop level, and m is the number of fault drop levels;

[0065] The classification of the layers disappearing upward along the fault is as follows:

[0066] U={U1,U2,U3……U n} (2)

[0067] In formula (2), U is the level of the horizon disappearing upwards on the fault, and n is the number of levels of the horizon disappearing upwards on the fault;

[0068] The fault drop and the fault disappearance level classification are combined into a two-dimensional fault level C m×n ,but:

[0069]

[0070] In step b, the influence coefficient of each level of fault on the formation pressure is preset as E m×n ,but:

[0071]

[0072] The influence coefficient of the preset erosion line on the formation pressure is E D .

[0073] This step also sets a fault impact threshold to correct the impact coefficient of each preset fault on the formation pressure. Among them, the fault impact threshold is obtained according to the lower limit of the level of impact of the fault on the formation pressure in the regional research results. The impact coefficient of each level of fault below this level on the formation pressure is zero. The fault impact threshold includes the fault drop level impact threshold and the fault upward disappearance level impact threshold. The correction method is:

[0074] Assume that the threshold value of the fault drop level is j, the threshold value of the fault disappearing upward is k, and the influence coefficient of each level of fault on the formation pressure after correction is E' m×n ,but:

[0075]

[0076] c. According to the shortest distance between the drilled well and the fault and erosion line, combined with the preset influence coefficients of each level of fault on the formation pressure and the influence coefficients of the erosion line on the formation pressure, a calculation model for the influence value of the fault and erosion line on the formation pressure is established.

[0077] Specifically, the method for establishing the calculation model is:

[0078] First, based on the wells and fault data in the area, the shortest distance between the wells and faults at all levels is extracted. m×n ,as follows:

[0079]

[0080] Then extract the shortest distance S between the drilled well and the erosion line D , then the established calculation model is:

[0081]

[0082] In formula (7), P E is the influence of fault and erosion line on formation pressure, E D It is the influence coefficient of the preset erosion line on the formation pressure.

[0083] d. Use the vertical depth of the formation and the logging density data of the wells drilled in the area to calculate the effective vertical pressure of the formation. Combined with the formation pressure test data of the wells drilled, through correlation analysis, with a high correlation coefficient as the goal, adjust the influence coefficients of the preset faults at all levels on the formation pressure and the influence coefficients of the erosion line on the formation pressure in stages; finally, substitute the influence coefficients of the faults at all levels on the formation pressure and the influence coefficients of the erosion line on the formation pressure adjusted when the correlation coefficient is the highest into the calculation model to obtain the calculation formula for the influence value of the faults and the erosion line on the formation pressure.

[0084] Specifically, the calculation method of the effective vertical pressure of the formation is:

[0085] P v =∑(ρ-1)gH (8)

[0086] In formula (8), P v is the effective vertical pressure of the formation, ρ is the logging density, and H is the vertical depth of the formation.

[0087] Furthermore, the calculation formula for the influence of faults and erosion lines on formation pressure is obtained as follows:

[0088] First, the formation pressure test value of the drilled well is obtained according to the formation pressure test data of the drilled well, and then the difference is calculated according to the effective vertical pressure of the formation and the obtained formation pressure test value, as follows:

[0089] ΔP=P v -P m (9)

[0090] In formula (9), ΔP is the difference between the effective vertical pressure of the formation and the measured formation pressure, P m is the formation pressure test value;

[0091] Then the difference between the effective vertical pressure of the formation and the formation pressure test value ΔP and the influence of the fault and erosion line on the formation pressure P E To perform correlation analysis, press E 11 >E 12 >…>E 1k >E 21 >…>E jk >E D The influence coefficients of the preset faults and the influence coefficients of the erosion lines on the formation pressure are adjusted step by step from high to low priority, so that the correlation coefficient reaches the highest value, and the difference ΔP between the effective vertical pressure of the formation and the test value of the formation pressure and the influence value P of the fault and the erosion line on the formation pressure are calculated. E The correlation formula is used as the influence value correction formula:

[0092] ΔP=f(P E ) (10)

[0093] Finally, the influence coefficients of faults at all levels adjusted when the correlation coefficient is the highest and the influence coefficients of erosion lines on the formation pressure are substituted into formula (7), and then formula (7) is substituted into formula (10) to obtain the calculation formula for the influence values ​​of faults and erosion lines on the formation pressure:

[0094]

[0095] In formula (11), P E is the impact of faults and erosion lines on formation pressure.

[0096] e. The formation pressure impact value can be calculated by using the distance between the designed well and the fault and erosion line, combined with the calculation formula for the impact value of the fault and erosion line on the formation pressure obtained in step d.

[0097] It should be noted that different types of faults and erosion lines have different effects on formation pressure, and the effect decreases with increasing distance. Therefore, the effect of faults and erosion lines on formation pressure is the sum of the effects of the nearest levels of faults and erosion lines around the well on formation pressure. Based on this, in order to obtain more accurate calculation results, this embodiment sets the influence coefficient of faults on formation pressure to 0-20MPa / km, and the influence coefficient of erosion lines on formation pressure to 0-20MPa / km, and preferably both preset values ​​are 10MPa / km.

[0098] Example 2

[0099] This example verifies the method described in Example 1, as follows:

[0100] 1. According to the fault classification standards in the following areas, the faults are classified in two dimensions. The classification standards are as follows:

[0101] Fault classification standards in the region

[0102]

[0103] Assuming the influence coefficient of fault and erosion line on formation pressure is 10, then:

[0104]

[0105] E $ =10.

[0106] 2. According to the results of regional geological research, the threshold of fault drop level is 2, and the threshold of fault disappearance level is 2, that is,

[0107]

[0108] 3. Based on the well data in the area, extract the distance S between each well and the nearest faults of all levels in the surrounding area according to Table 1 m×n The distance S from the erosion line D ,but:

[0109]

[0110] Table 1 Distances between each well and the fault and erosion line

[0111] hashtag S11 S12 S12 S22 S34 S44 SD Well A / / 5.3 / 5.3 2.9 18.7 Well B / / 7.7 / 1.3 0.5 15.6 C Well 3.4 / 1.6 6.8 1.9 / 12.9 D Well 12.7 / 5.8 / 4.2 1.4 17.9 E Well 10.8 / 6.3 / 2.7 1.4 17.5 F Well 13.6 / 5.4 / 5.6 2.9 18.6 G Well 13.3 / 5.5 / 5.4 2.7 17.4 H Well 12.9 / 5.7 / 4 2.5 17.6 I well 8.4 / 5.4 / 4.2 2.3 15.7

[0112] 4. Combine the above formula to establish the formation pressure impact value P E The computational model.

[0113] 5. Calculate the difference ΔP between the effective vertical pressure and the obtained formation pressure test value and the formation pressure influence value P E To perform correlation analysis, press E 11 >E 12 >E 21 >E 22 >E D The order of high first then low, fault first then erosion line is adjusted step by step, and the influence coefficients of the preset fault and erosion line on the formation pressure are shown in Table 2 below. Then Figure 1 As shown in the figure, the best coefficients of influence of faults and erosion lines on formation pressure are selected with the best correlation as the goal.

[0114] Table 2 The influence coefficients and models of faults and erosion lines on formation pressure

[0115]

[0116] 6. Based on the optimal influence coefficient, the calculation method of the influence value of fault and erosion line on formation pressure is obtained.

[0117] PE =9.1 / S 11 +9.5 / S 12 +8.2 / S 21 +7.8 / S 22 +5.5 / S D

[0118] In summary, when the specific scheme described in the present invention is put into practical application, the pressure prediction accuracy can be improved from 45.2% to 77.4%, which provides important technical support for the prediction of formation pressure coefficient in drilling geological design.

[0119] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A method for calculating the impact of faults and erosion lines on formation pressure, characterized by: The steps include: a. Collect well logging, fault, erosion line and formation pressure test data of the formation in the area around the designed well; b. Based on the fault data of the formation, the fault drop and the fault disappearance layer upward are used as classification parameters to classify the faults in the area. After classification, the influence coefficients of each level of fault on the formation pressure are preset according to the fault grade, and the influence coefficient of the erosion line on the formation pressure is preset at the same time; c. According to the shortest distance between the drilled well and the fault and erosion line, combined with the preset influence coefficients of each level of fault on the formation pressure and the influence coefficients of the erosion line on the formation pressure, a calculation model for the influence value of the fault and erosion line on the formation pressure is established; d. Calculate the effective vertical pressure of the formation using the vertical depth and logging density data of the wells that have been drilled in the area, and combine the formation pressure test data of the wells that have been drilled. Through correlation analysis, with a high correlation coefficient as the goal, adjust the influence coefficients of the preset faults at all levels on the formation pressure and the influence coefficients of the erosion line on the formation pressure in stages; finally, substitute the influence coefficients of the faults at all levels on the formation pressure and the influence coefficients of the erosion line on the formation pressure adjusted when the correlation coefficient is the highest into the calculation model, and obtain the calculation formula for the influence value of the faults and the erosion line on the formation pressure; e. Calculate the formation pressure impact value by using the distance between the designed well and the fault and erosion line in combination with the calculation formula obtained in step d; In step b, a fault influence threshold is set to correct the influence coefficient of each level of fault on the formation pressure; The fault impact threshold includes the fault drop level impact threshold and the fault upward disappearance level impact threshold; In step b, the faults in the region are classified using a two-dimensional model, and the method is as follows: The classification of fault drop is: <h2 style=";text-align:left;direction:ltr">D = {D1,D2,D3……D<h2 style=";text-align:left;direction:ltr"> m <h2 style=";text-align:left;direction:ltr">} (1) In formula (1), D is the fault drop level, and m is the number of fault drop levels; The classification of the layers disappearing upward along the fault is as follows: U={U1,U2,U3……U n } (2) In formula (2), U is the level of the horizon disappearing upwards on the fault, and n is the number of levels of the horizon disappearing upwards on the fault; The fault drop and the fault disappearance level classification are combined into a two-dimensional fault level C m×n ,but: In step b, the influence coefficient of each level of fault on the formation pressure is preset as E m×n ,but: In step b, the threshold value of the fault drop level is j, the threshold value of the fault disappearing upward is k, and the influence coefficient of each level of fault on the formation pressure after correction is E ’ m×n ,but: The method for establishing the calculation model in step c is: First, based on the wells and fault data in the area, the shortest distance between the wells and faults at all levels is extracted. m×n ,as follows: Then extract the shortest distance S between the drilled well and the erosion line D , then the established calculation model is: In formula (7), P E is the influence of fault and erosion line on formation pressure, E D is the influence coefficient of the preset erosion line on the formation pressure; In step d, the calculation method of the effective vertical pressure of the formation is: P v =∑(ρ-1)gH (8) In formula (8), P v is the effective vertical pressure of the formation, ρ is the logging density, and H is the vertical depth of the formation; In step d, the calculation formula of the influence value of the fault and the erosion line on the formation pressure is obtained by first obtaining the formation pressure test value of the drilled well according to the formation pressure test data of the drilled well, and then calculating the difference according to the effective vertical pressure of the formation and the obtained formation pressure test value, as follows: ΔP=P v -P m (9) In formula (9), ΔP is the difference between the effective vertical pressure of the formation and the test value of the formation pressure, P m is the formation pressure test value; Then the difference between the effective vertical pressure of the formation and the formation pressure test value ΔP and the influence of the fault and erosion line on the formation pressure P E To perform correlation analysis, press E 11 >E 12 >…>E 1k >E 21 >…>E jk >E $ The influence coefficients of the preset faults and the influence coefficients of the erosion lines on the formation pressure are adjusted step by step from high to low priority, so that the correlation coefficient reaches the highest value, and the difference ΔP between the effective vertical pressure of the formation and the test value of the formation pressure and the influence value P of the fault and the erosion line on the formation pressure are calculated. E The correlation formula is used as the influence value correction formula: ΔP=f(P E ) (10) Finally, the influence coefficients of faults at all levels adjusted when the correlation coefficient is the highest and the influence coefficients of erosion lines on the formation pressure are substituted into formula (7), and then formula (7) is substituted into formula (10) to obtain the calculation formula for the influence values ​​of faults and erosion lines on the formation pressure:

2. The method for calculating the influence of fault and erosion line on formation pressure according to claim 1, characterized in that: The fault impact threshold is obtained based on the lower limit of the level of impact of the fault on the formation pressure in regional research results.

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