Horizontal well productivity prediction method based on well logging reservoir classification and box drilling rate

Abstract

The present application relates to a kind of based on well logging reservoir classification and box drilling rate horizontal well productivity prediction method.The main problem of low accuracy of existing shale gas horizontal well productivity prediction method is solved.It is characterized by: calculating the daily gas production of several gas testing well single well per hundred meters fractured well section, the box drilling rate of gas testing horizontal well single well;Classify the shale gas reservoir of pilot hole of gas testing well, and count the maximum continuous thickness of pilot hole I shale gas reservoir;Establish a binary linear regression model about the daily gas production of per hundred meters fractured well section;Calculate the daily gas production of the single well per hundred meters fractured well section of the well to be predicted;Calculate the daily gas production of the single well of the well to be predicted.The method combines the maximum continuous thickness of pilot hole I shale gas reservoir of well logging reservoir comprehensive classification and the box drilling rate of horizontal well single well to predict the productivity of shale gas horizontal well single well, effectively improves the accuracy of shale gas horizontal well productivity prediction, and provides a reference for the development plan of shale gas reservoir.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas well logging evaluation, in particular to a horizontal well productivity prediction method based on well logging reservoir classification and box drilling rate. BACKGROUND

[0002] Shale gas reservoir productivity evaluation and prediction is an important part of oilfield development plan. Many scholars have explored in this field, which can be divided into two categories: one is to establish statistical relationship between various logging parameters and reservoir productivity based on a large number of oil test and production data; the other is to use machine learning methods such as neural network, decision tree and support vector machine to establish productivity evaluation model using known samples (multiple logging parameters and corresponding productivity data), and then use the model to predict unknown samples. For example, there is a linear model based shale gas horizontal well initial maximum productivity prediction method, which uses the initial maximum stable production of each shale gas well tested and the sum of the porosity of each I, II type shale gas layer in the horizontal section of the well tested and the length of the gas layer tested to establish a linear regression model according to the least square method. There is also a method to calculate the daily production of single well shale gas according to the content of brittle mineral in the formation, the porosity of the formation, the permeability of the formation and the gas saturation of the formation. These methods only consider the influence of a certain parameter index, although they have certain applicability, but the precision is not high and the effect is not ideal. SUMMARY

[0003] In order to overcome the low precision of the existing shale gas horizontal well productivity prediction method, the present application provides a horizontal well productivity prediction method based on well logging reservoir classification and box drilling rate, which comprehensively considers the maximum continuous thickness of the I type shale gas reservoir of the pilot hole of the well tested and the box drilling rate of the single well of the horizontal well to predict the single well productivity of the shale gas horizontal well, effectively improves the accuracy of the shale gas horizontal well productivity prediction, and provides a reference for the development plan of the shale gas reservoir.

[0004] The technical scheme of the present application is: a horizontal well productivity prediction method based on well logging reservoir classification and box drilling rate, comprising:

[0005] S1, respectively calculating the daily gas production per hundred meters of fractured well section QCI of a plurality of wells tested and the box drilling rate ZI0 of the single well of the horizontal well tested;

[0006] S2, classifying the shale gas reservoir of the pilot hole of the well tested, and counting the maximum continuous thickness HI0 of the I type shale gas reservoir of the pilot hole;

[0007] S3, according to the results of steps S1 and S2, establishing a binary linear regression model according to the least square method, and obtaining

[0008] QCI = A + B1*ZI0 + B2*HI0

[0009] wherein A, B1, B2 are constants;

[0010] S4, calculating the daily gas production per 100 meters of fractured well section of the single well of the well to be predicted according to the model in step S3,

[0011] QCIY = A + B1*ZI + B2*HI;

[0012] wherein ZI is the single well box drilling rate of the well to be predicted, and HI is the maximum continuous thickness of the I-type shale gas reservoir of the single well of the well to be predicted, in meters;

[0013] S5, calculating the daily gas production QCY of the single well of the well to be predicted,

[0014] QCY = (A + B1*ZI + B2*HI)*YL / 100

[0015] wherein YL is the designed fractured well section of the single well of the well to be predicted, in meters.

[0016] Further, in the step S1, the daily gas production per 100 meters of fractured well section QCI of the single well of the tested gas well is calculated according to the single well daily gas production QC of the tested gas well and the fractured well section length YL of the tested gas well,

[0017] QCI = (QC / YL0)*100

[0018] wherein QC is in units of ten thousand cubic meters per day; YL0 is in meters; and QCI is in units of ten thousand cubic meters per day.

[0019] Further, in the step S1, the single well box drilling rate ZI0 of the tested gas well is calculated according to the single well box drilling section length ZL0 of the tested gas well and the actual horizontal section length SL0 of the tested gas well,

[0020] ZI0 = (ZL0 / SL0)*100

[0021] wherein ZL and SL are in meters.

[0022] Further, in the step S2, first, the total organic carbon content TOC, the total gas content QALL, the porosity POR and the brittle mineral content BRMC4 are obtained, and the shale gas reservoir of the horizontal well is classified according to the reservoir classification evaluation standard.

[0023] Further, in the step S5, since

[0024] QCY = QCIY*YL / 100

[0025] the daily gas production QCY of the single well of the well to be predicted is obtained,

[0026] QCY=(A+B1*ZI+B2*HI)*YL / 100

[0027] In the formula, YL is the single-well designed fracturing well section length of the well to be predicted, in meters.

[0028] Further, to verify the accuracy of the single-well daily gas production QCY formula of the well to be predicted, the single-well daily gas production QCI calculated according to the formula is compared with the actual daily gas production QC, and the difference meets the preset threshold requirement.

[0029] Further, the tested well and the predicted well are the same layer horizontal well.

[0030] The present application has the following beneficial effects: due to the above-mentioned scheme, on the basis of analyzing the shale gas horizontal well productivity influencing factor, the total organic carbon content, total gas content, porosity and brittle mineral content in the logging processing result data are applied to classify the pilot well reservoir, the maximum continuous thickness of the pilot well I shale gas reservoir is counted, the known horizontal well drilling rate and the gas testing data are combined, the binary first-order equation is adopted to construct the shale gas horizontal well productivity prediction formula, and the problem of low shale gas horizontal well productivity prediction precision is solved. The correlation between the single-well predicted productivity and the actual productivity of the shale gas horizontal well reaches 97.2% on average by using the method, the maximum continuous thickness of the pilot well I shale gas reservoir and the horizontal well box drilling rate are comprehensively used for the single-well productivity prediction of the shale gas horizontal well for the first time in China, and the accuracy is at the leading level in the similar technologies. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a flow chart of the present application;

[0032] Figure 2 is a cross plot of the predicted per-hundred-meter fracturing well section daily gas production QCIY and the actual single-well per-hundred-meter fracturing well section daily gas production QCI of 7 wells in the embodiment;

[0033] Figure 3 is a cross plot of the predicted daily gas production QCY and the actual single-well daily gas production data QC of 7 wells in the embodiment. DETAILED DESCRIPTION

[0034] The present application will be further described below in combination with the drawings:

[0035] As shown in Figure 1 , a horizontal well productivity prediction method based on logging reservoir classification and box drilling rate, comprising:

[0036] S1, obtaining the single-well daily gas production data QC and the fracturing well section length YL0 of each tested well from a known database, and calculating the single-well per-hundred-meter fracturing well section daily gas production QCI of the tested well, and the expression is:

[0037] QCI = (QC / YL0) * 100 (1)

[0038] In the formula, QC is in units of ten thousand square meters per day; YL0 is in units of meters; and QCI is in units of ten thousand square meters per day.

[0039] Further, the length ZL0 of the drilled section of the single well casing of each tested gas well and the actual horizontal section length data SL0 thereof are obtained from a known database, and the drilled section rate ZI0 of the single well casing of the tested gas well is calculated, and the expression thereof is:

[0040] ZI0 = (ZL0 / SL0) * 100 (2)

[0041] In the formula, ZL and SL are in units of meters.

[0042] S2, total organic carbon content TOC, total gas content QALL, porosity POR, and brittle mineral content BRMC4 are obtained from a well logging interpretation processing result file, and the units of TOC, QALL, POR, and BRMC4 are %, m3 / t, %, and % respectively; the shale gas reservoir of the pilot hole is classified according to a reservoir classification evaluation standard, and the maximum continuous thickness HI0 of the Class I shale gas reservoir of the pilot hole is counted, and the unit of HI0 is meters.

[0043] S3, according to the results of steps S1 and S2, a binary linear regression model is established according to the least square method, and the regression curve of the model passes through the origin. The linear model is:

[0044] QCI = A + B1*ZI0 + B2*HI0 (3)

[0045] In the formula, QCI is the daily gas production per hundred meters of the fractured well section of the single well of the tested gas well, and the unit is ten thousand square meters per day; ZI0 is the drilled section rate of the single well casing of the tested gas well, and the unit is %; and HI0 is the maximum continuous thickness of the Class I shale gas reservoir of the pilot hole of the tested gas well, and the unit is meters.

[0046] S4, the daily gas production per hundred meters of the fractured well section of the single well of the predicted well QCIY is calculated according to the model in step S3, and the expression thereof is:

[0047] QCIY = A + B1*ZI + B2*HI (4)

[0048] In the formula, QCIY is the daily gas production per hundred meters of the fractured well section of the single well of the predicted well, and the unit is ten thousand square meters per day; ZI is the drilled section rate of the single well of the predicted well, and the unit is %; and HI is the maximum continuous thickness of the Class I shale gas reservoir of the pilot hole of the predicted well, and the unit is meters.

[0049] S5, the daily gas production QCY of the single well of the predicted well is calculated according to the daily gas production per hundred meters of the fractured well section QCIY of the single well of the predicted well and the designed fractured well section YL thereof, and the expression thereof is:

[0050] QCY = QCIY * YL / 100 (5)

[0051] In the formula, QCY is in units of ten thousand cubic meters per day, QCIY is in units of ten thousand cubic meters per day, and YL is the single-well designed fracturing well length of the well to be predicted, in units of meters.

[0052] Further, a single-well daily gas production formula of the well to be predicted is derived, and the formula is:

[0053] QCY = (A + B1 * ZI + B2 * HI) * YL / 100 (6)

[0054] In the formula, QCY is the single-well daily gas production of the well to be predicted, in units of ten thousand cubic meters per day; and ZI is the single-well box drilling rate of the well to be predicted, in units of %.

[0055] It can be seen that the shale gas horizontal well productivity is related to the reservoir classification and the box drilling rate. The greater the maximum continuous thickness of the Class I shale gas reservoir of the pilot hole is, the higher the horizontal well box drilling rate is, and the higher the single-well productivity of the shale gas horizontal well is.

[0056] To verify the accuracy of the formula (6), the single-well daily gas production QCY calculated according to the formula is compared with the actual daily gas production QC of the well. If the difference meets the preset threshold requirement, it means that the formula is accurate. The preset threshold can be determined according to the reservoir condition and the well condition.

[0057] The above-described tested gas well and the well to be predicted are required to be the same level horizontal well.

[0058] Embodiment:

[0059] Taking Z301 well and Z305 well in a block of Zigong low-fold structural belt in the Sichuan Basin low-steep structural belt as examples, the following steps are included.

[0060] In step S1, the single-well daily gas production data QC and the fracturing well length YL0 of the seven tested gas horizontal wells are obtained from the known data. The single-well daily gas production per hundred meters of fracturing well section QCI of the horizontal wells is calculated according to formula (1). The box drilling section length ZL0 and the actual horizontal section length data SL0 of the eight wells are obtained. The box drilling rate ZI0 of the horizontal wells is calculated according to formula (2). See Table 2 for details.

[0061] In step S2, the total organic carbon content TOC, the total gas content QALL, the porosity POR and the brittle mineral content BRMC4 are obtained from the pilot hole logging interpretation processing result file provided by the logging company. The pilot hole shale gas reservoir is classified according to the reservoir classification evaluation standard, and the classification standard is shown in Table 1.

[0062] Table 1

[0063]

[0064] The maximum continuous thickness Hio of the I-type shale gas reservoir of the pilot well is counted.

[0065] Table 2

[0066]

[0067]

[0068] In step S3, according to the drilling rate ZI of each well box and the maximum continuous thickness Hio of the I-type shale gas reservoir of the pilot well calculated in steps S1 and S2, a binary linear regression model is established according to the least square method, and the daily gas production per hundred meters of the fractured well section of a single well QCIY is obtained,

[0069] QCIY = -0.093 + 0.015 * ZI + 0.059 * HI (7)

[0070] Then the single well daily gas production formula of the to-be-predicted well is further obtained:

[0071] QCY = (-0.093 + 0.015 * ZI + 0.059 * HI) * YL / 100 (8)

[0072] Figure 2 is a cross plot of the predicted daily gas production per hundred meters of the fractured well section of a single well QCIY and the actual daily gas production per hundred meters of the fractured well section of a single well QCI of the seven wells in Table 2, and the regression analysis correlation coefficient R 2 is greater than 0.9.

[0073] The daily gas production per hundred meters of the fractured well section QCIY and the single well daily gas production QCY of each well are calculated according to formula (7) and formula (8), and the predicted values calculated are shown in Table 3.

[0074] Table 3

[0075]

[0076] The predicted single well daily gas production QCY of each well is compared with the gas production QC in Table 2, and after verification, the error meets the requirements, proving that formula (8) is accurate. Figure 3 is a cross plot of the predicted single well daily gas production QCY and the actual single well daily gas production QC of the seven wells in Table 2, and the correlation reaches 97.2%.

[0077] In step S4, the single well daily gas production QCY of Z305 well and Z301 well is predicted according to the formula obtained in step S3, wherein Z305 well is:

[0078] S4.11, the length of the horizontal well box drilled section ZL of the well Z305 is 1374.4 meters, the actual horizontal section length data SL is 1730 meters, the horizontal well box drilling rate ZI of the well Z305 is calculated according to the formula (2) as 79.45;

[0079] S4.12, the maximum continuous thickness HI of the I-type shale gas reservoir of the pilot hole of the well Z305 is 11.4 meters;

[0080] S4.13, the daily gas production per hundred meters of the fractured well section QCIY of the well Z305 is calculated according to the formula (7) as 1.8×104m3 / d;

[0081] QCIY=-0.093+0.015*ZI+0.059*HI

[0082] = -0.093 + 0.015 * 79.45 + 0.059 * 11.4 = 1.77135

[0083] S4.14, the designed fractured well section length YL of the well Z305 is 1670 meters, the daily gas production QCY of the single well of the well Z305 is calculated according to the formula (8) as 29.58×104m3 / d.

[0084] QCY=(-0.093+0.015*ZI+0.059*HI)*YL / 100

[0085] = (-0.093 + 0.015 * 79.45 + 0.059 * 11.4) * 1670 / 100 = 29.58,

[0086] Therefore, the predicted daily gas production of the single well of the well Z305 is 29.58×104m3 / d.

[0087] The well Z301 is:

[0088] S4.21, the length of the horizontal well box drilled section ZL of the well Z301 is 1635.84 meters, the actual horizontal section length data SL is 1800 meters, the horizontal well box drilling rate ZI of the well Z301 is calculated according to the formula (2) as 90.88;

[0089] S4.22, the maximum continuous thickness HI of the I-type shale gas reservoir of the pilot hole of the well Z301 is 9 meters;

[0090] S4.23, the daily gas production per hundred meters of the fractured well section QCIY of the well Z301 is calculated according to the formula (7) as 1.8×104m3 / d;

[0091] S4.24, the designed fractured well section length YL of the well Z301 is 1800 meters, the daily gas production QCY of the single well of the well Z301 is calculated according to the formula (8) as 32.44×104m3 / d.

[0092] In actual production, the actual daily gas production of Z301 well is 310,000 cubic meters, the predicted single well daily gas production is 324,400 cubic meters, the absolute error is 14,400 cubic meters, and the relative error is 4.44%, which meets the requirements.

[0093] The present application uses the logging reservoir classification technology to count the maximum continuous thickness of the I-class shale gas reservoir of the shale gas pilot hole, and combines the horizontal well box drilling rate to predict the productivity of the shale gas horizontal well, compared with the prior art, the accuracy of the productivity prediction of the shale gas horizontal well is effectively improved, and a reference basis is provided for the development plan of the shale gas reservoir.

[0094] Those skilled in the art can understand that, in the above method of the specific embodiment, the writing order of each step does not mean a strict execution order and constitute any limitation on the implementation process, and the specific execution order of each step should be determined according to its function and possible internal logic.

[0095] The above-described embodiments are only to express the embodiments of the present disclosure, which are described in detail and specifically, but should not be understood as a limitation on the scope of the present disclosure. It should be noted that, for those skilled in the art, without departing from the concept of the present disclosure, a number of modifications, equivalent replacements, improvements and the like can be made, which are all within the protection scope of the present disclosure.

Claims

1. A method for predicting the productivity of a horizontal well based on well logging reservoir classification and cased hole penetration rate, characterized in that The method comprises the following steps: S1, respectively calculating the single-well per-hundred-meter fractured well section daily gas production QCI of a plurality of tested gas wells and the single-well box body drilling rate ZI0 of a horizontal well that has been tested, comprising: According to the single-well daily gas production QC of the tested gas well and the fractured well section length YL0 of the tested gas well, the single-well per-hundred-meter fractured well section daily gas production QCI of the tested gas well is calculated, QCI=(QC / YL 0 ）*100 In the formula, QC is in units of ten thousand cubic meters per day; YL0 is in units of meters; and QCI is in units of ten thousand cubic meters per day; According to the box body drilling section length ZL0 of the single well of the tested gas well and the actual horizontal section length SL0 of the tested gas well, the single-well box body drilling rate ZI0 of the tested gas well is calculated, ZI 0 =(ZL 0 / SL 0 ）*100 In the formula, ZL and SL are in units of meters; S2, classifying the shale gas reservoir of the pilot hole of the tested gas well, and counting the maximum continuous thickness HI0 of the shale gas reservoir of the pilot hole of the tested gas well; S3, according to the results of steps S1 and S2, a binary linear regression model is established according to the least square method, QCI=A+B 1 *ZI 0 +B 2 *HI 0 In the formula, A, B1 and B2 are constants; S4, according to the model in step S3, the single-well per-hundred-meter fractured well section daily gas production QCIY of the to-be-predicted well is calculated, QCIY= A+B 1 *ZI+B 2 *HI; In the formula, ZI is the single-well box body drilling rate of the to-be-predicted well, and HI is the maximum continuous thickness of the shale gas reservoir of the pilot hole of the to-be-predicted well, in units of meters; S5, the single-well daily gas production QCY of the to-be-predicted well is calculated, QCY=(A+B 1 *ZI+B 2 *HI)*YL / 100 In the formula, YL is the single-well designed fractured well section of the to-be-predicted well, in units of meters.

2. The method according to claim 1, characterized in that: In step S2, the total organic carbon content TOC, the total gas content QALL, the porosity POR and the brittle mineral content BRMC4 are first obtained, and the pilot hole shale gas reservoir is classified by comparing the reservoir classification evaluation standard.

3. The method according to claim 1, characterized in that: In step S5, because QCY=QCIY*YL / 100 The single-well daily gas production QCY of the to-be-predicted well is obtained, QCY=(A+B 1 *ZI+B 2 *HI)*YL / 100 In the formula, YL is the single-well designed fractured well section length of the to-be-predicted well, in units of meters.

4. The method according to claim 1, characterized in that: In order to verify the accuracy of the single-well daily gas production QCY formula of the to-be-predicted well, the single-well daily gas production QCY calculated according to the formula is compared with the actual daily gas production QC, and the difference meets the preset threshold requirement.

5. The method according to any one of claims 1-4, characterized in that: The tested gas well and the to-be-predicted well are the same horizon horizontal well.

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