Method for judging bottom interface of permian system stone thousand peak group by applying element logging data

Abstract

The invention belongs to the technical field of petroleum and natural gas exploration and development, and particularly relates to a method for judging a bottom interface of a permian stone thousand peak group by applying element logging data, which comprises the following steps: S1, collecting logging rock debris while drilling; s2, performing coarse division on the bottom interface of the permian stone thousand-peak group by combining regional deposition characteristics and geological design information, and delimiting a coarse division interface; s3, performing X-ray fluorescence spectrum scanning on the logging rock debris while drilling to obtain strontium, copper and barium element data; s4, carrying out data processing, analysis and judgment on the strontium, copper and barium element data, and calculating an interface coefficient JM; and S5, correcting the depth of the coarse interface to obtain the bottom interface depth of the permian stone thousand-peak group. According to the method for judging the bottom interface of the permian stone thousand peak group by applying the element logging data, errors existing in a lithology combination judgment method which mainly depends on naked eyes of technicians to recognize rock debris are corrected, and the method has the advantages of being small in error, small in data processing amount, high in accuracy, low in cost, easy to operate and wide in application range.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration and development technology, specifically relating to a method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data. Background Technology

[0002] The Shiqianfeng Formation is the uppermost formation of the Permian System. Its main lithology consists of a set of fluvial purplish-red rock strata, including siltstone, mudstone, with a small amount of conglomerate, coarse to medium-fine grained clean sandstone and mixed sandstone. It contains plant fossils: Taiyuan ferns, pointed whorled ferns, and Korean feather ferns. It has a conformable contact relationship with the underlying Upper Shihezi Formation, is over 150m thick, and is widely developed in the central and western regions of my country.

[0003] During on-site drilling operations, timely and accurate identification of the bottom interface of the Shiqianfeng Formation is helpful for on-site stratigraphic correlation, prediction of stratigraphic lithology, and determination of the encountered strata. It is also of great significance in reconstructing paleogeography, paleolithic facies, and paleoclimate. Conventional methods for identifying the bottom interface of the Shiqianfeng Formation include three main types: lithological combination identification, well logging curve identification, and element combination identification.

[0004] The lithology combination judgment method has the following technical problems: Due to the improvement of drilling technology, especially the promotion and application of PDC drill bit turbine drill tool combination, gas drilling and other technologies, the logging cuttings are very fine and mixed, and the lithology combination judgment method that relies on technicians to identify cuttings by visual inspection has a large error.

[0005] Well logging curve identification method can accurately determine formation interfaces, but well logging is mostly a post-drilling procedure, and during drilling, well logging is mostly not performed, making it impossible to identify formation interfaces in a timely and accurate manner.

[0006] Existing element combination identification methods primarily use element combination characteristics as an auxiliary to lithological combination judgment methods. The main methods are: ① Curve anomaly combination method: At the boundaries of stratigraphic layers of different ages, the background values ​​of general element combinations will show significant abrupt changes, characterized by an overall abrupt change. ② Lithological combination method: Different sedimentary environments at different ages result in different sedimentary sources and backgrounds. Consequently, lithological combinations also vary significantly due to different facies environments. Different lithological combinations lead to significant changes in elemental composition, especially at lithological combination transition interfaces, where the characteristics are particularly pronounced. ③ Characteristic element method: Certain elements react more sensitively at key stratigraphic boundaries for various reasons. Therefore, stratigraphic boundaries can be defined based on certain characteristic elements, and element curves show significant changes at stratigraphic boundaries.

[0007] Chinese patent CN107313770A discloses a new method for stratigraphic division using elemental logging feature profiles, comprising: firstly, establishing elemental logging feature profiles, and then summarizing the elemental characteristics of different stratigraphic units and marker beds through the feature profiles to perform stratigraphic division; wherein, the process of establishing elemental logging feature profiles can be divided into seven steps: (1) understanding the geological background; (2) data processing and correction; (3) elemental cross-plot analysis; (4) sensitive element screening; (5) correction of theoretical values ​​and standard rock samples; (6) segmented and lithological feature extraction; (7) establishing feature profiles by block. This method extracts sensitive elements through elemental cross-plots and processes 136 cross-plots, resulting in a large amount of data processing. Summary of the Invention

[0008] To address the technical problems of existing lithological combination judgment methods, which rely heavily on technicians' visual identification of rock cuttings and have large errors, as well as the technical problems of existing logging curve identification methods, which can accurately identify logging formation interfaces but cannot timely and accurately identify non-logging formation interfaces during drilling, and the technical problem of existing element combination identification methods, which have large data processing requirements, this invention provides a method for judging the bottom interface of the Permian Shiqianfeng Formation using element logging data, in order to solve the above-mentioned technical problems.

[0009] This invention provides a method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data. This method corrects the errors present in the lithological combination judgment method that mainly relies on technicians to visually identify rock cuttings. It has the advantages of small error, small data processing volume, high accuracy, low cost, easy operation, and wide applicability.

[0010] The technical solution adopted by this invention to solve the technical problem is as follows:

[0011] This invention provides a method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data, which mainly includes the following steps:

[0012] Step S1: Collect logging cuttings;

[0013] Step S2: Based on regional sedimentary characteristics and geological design information, the bottom interface of the Permian Shiqianfeng Formation is roughly divided, and the rough division interface is delineated.

[0014] Step S3: Perform X-ray fluorescence spectroscopy scanning on the logging cuttings to obtain elemental data;

[0015] Step S4: Perform data processing, analysis, and judgment on the element data, and calculate the interface coefficient JM;

[0016] Step S5: Correct the coarse interface depth to obtain the bottom interface depth of the Permian Shiqianfeng Formation.

[0017] In a preferred embodiment, in step S3, the elemental data is strontium, copper, and barium elemental data.

[0018] In a preferred embodiment, in step S3, before performing X-ray fluorescence spectroscopy scanning on the logging-while-drilling cuttings, false cuttings in the logging-while-drilling cuttings are first manually removed.

[0019] In a preferred embodiment, in step S4, the formula for calculating the interface coefficient JM is:

[0020] JM = Sr 2 / Cu / Ba-X (1)

[0021] Where JM is the interface coefficient; Sr is the mass percentage of strontium content measured by elemental logging; Cu is the mass percentage of copper content measured by elemental logging; Ba is the mass percentage of barium content measured by elemental logging; and X is the correction coefficient.

[0022] In a more preferred embodiment, the correction coefficient X is in the range of 0.65-0.95.

[0023] In a more preferred embodiment, the correction coefficient X is in the range of 0.7-0.9.

[0024] In a more preferred embodiment, both the interface coefficient and the correction coefficient are dimensionless.

[0025] In a preferred embodiment, step S4 involves processing the element data and amplifying the features.

[0026] In a preferred embodiment, in step S5, the depth of the bottom interface of the Permian Shiqianfeng Formation is further divided based on the coarse interface defined in step S2.

[0027] In a more preferred implementation, in step S5, after the second division, the depth at which the interface coefficient JM near the coarse interface drops sharply from positive to negative is taken as the bottom interface depth of the Permian Shiqianfeng Formation.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. Small Error: Existing lithological combination judgment methods suffer from significant errors due to improvements in drilling technology, particularly the widespread application of PDC drill bit turbine drill string combinations and gas drilling, which result in highly fragmented and mixed logging cuttings. This reliance on technicians' visual identification of cuttings leads to substantial errors. In contrast, this invention utilizes elemental logging data, especially strontium, copper, and barium element data, to determine the bottom interface of the Permian Shiqianfeng Formation, correcting the errors inherent in visual cuttings identification methods and thus offering the advantage of small errors.

[0030] 2. Small data processing volume and high accuracy: This invention uses drilling data, which reduces the amount of data processing and improves work efficiency. It has the advantages of strong real-time performance, low cost, easy operation and high accuracy.

[0031] 3. Wide range of applications: This invention is applicable not only to vertical wells and directional wells, but also to horizontal wells. It can still accurately identify the bottom interface of the Shiqianfeng Formation without logging, which solves the problem that existing logging curve identification methods cannot identify formation interfaces without logging in a timely and accurate manner. Attached Figure Description

[0032] Figure 1 The flowchart of a method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data provided by the present invention is shown.

[0033] Figure 2 This is a composite diagram of well M. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings.

[0035] Since there is a specific correspondence between the specific depositional age, specific depositional environment and the content of certain trace elements, this invention proposes a method for determining the bottom interface of the Permian Shiqianfeng Formation by utilizing specific trace elements such as strontium, copper and barium in the elemental logging data during drilling.

[0036] Strontium, copper, and barium are trace elements, and their mass percentage content in rock fragments is low. The Shiqianfeng Formation was deposited in a shallow-water oxidizing environment on a terrestrial scale. After data processing, the strontium, copper, and barium element data correspond to this stratum, which can be used to determine stratigraphic interfaces. This invention can also be applied to determine other shallow-water oxidizing environments on a terrestrial scale.

[0037] See Figure 1 The present invention provides a method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data, the specific implementation process of which is as follows:

[0038] Step S1: Collect logging cuttings;

[0039] Step S2: Based on regional sedimentary characteristics and geological design information, the bottom interface of the Permian Shiqianfeng Formation is roughly divided, and the rough division interface is delineated.

[0040] Step S3: Perform X-ray fluorescence spectroscopy on the logging cuttings to obtain strontium, copper, and barium element data; before performing X-ray fluorescence spectroscopy on the logging cuttings, it is necessary to manually remove false cuttings in order to extract formation information more accurately and improve the accuracy of determining the depth of the bottom interface of the Permian Shiqianfeng Formation.

[0041] Step S4: Process and analyze the strontium, copper, and barium element data, and calculate the interface coefficient (JM) based on the strontium, copper, and barium element data obtained in Step S3. The specific calculation formula is as follows:

[0042] JM = Sr 2 / Cu / Ba-X (1)

[0043] Wherein, JM is the interface coefficient, dimensionless; Sr is the mass percentage of strontium content measured by elemental logging; Cu is the mass percentage of copper content measured by elemental logging; Ba is the mass percentage of barium content measured by elemental logging; X is the correction coefficient, dimensionless, with a value range of 0.65-0.95, preferably 0.8.

[0044] Using only one of the elements strontium, copper, and barium, or simply using their ratios, has certain limitations in determining stratigraphic positions. Therefore, it is necessary to process the strontium, copper, and barium data to amplify the characteristics.

[0045] Step S5: Correct the coarse interface depth to obtain the bottom interface depth of the Permian Shiqianfeng Formation;

[0046] Specifically, based on the coarse interface defined in step S2, the depth of the bottom interface of the Permian Shiqianfeng Formation is divided a second time. The depth at which the interface coefficient (JM) near the coarse interface drops sharply from positive to negative (the depth is taken as an integer) is the depth of the bottom interface of the Permian Shiqianfeng Formation.

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment provides a method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data. Taking a horizontal well M in the Sulige area of ​​the Ordos Basin as an example, the method is implemented through the following steps:

[0050] a. Collect drilling cuttings while logging;

[0051] b. Based on regional sedimentary characteristics and geological design information, the bottom interface of the Permian Shiqianfeng Formation was roughly divided, and the rough interface was delineated at 3134m.

[0052] c. First, the false cuttings in the logging-while-drilling cuttings are manually removed, and then the logging-while-drilling cuttings are scanned by X-ray fluorescence spectroscopy to obtain the strontium, copper and barium element data;

[0053] d. Data processing, analysis and judgment of strontium, copper and barium elements, and calculation of interface coefficient (JM) according to formula (1); the cuttings logging spacing of this well is 2m / pack, JM(3130)=1.89, JM(3132)=-0.54, JM(3134)=-0.50;

[0054] e. Based on the coarse interface of 3134m defined in step b, the depth of the bottom interface of the Permian Shiqianfeng Formation is divided a second time. The depth at which the interface coefficient (JM) near the coarse interface drops sharply from positive to negative (the depth is taken as an integer) is the bottom interface depth of the Permian Shiqianfeng Formation, which is 3130m.

[0055] like Figure 2 As shown in Table 1, taking a horizontal well M in the Sulige area of ​​the Ordos Basin as an example, the depth of the bottom interface of the Shiqianfeng Formation corresponding to the natural gamma curve after drilling is 3129.5m. The original cuttings during drilling indicate that the bottom interface of the Shiqianfeng Formation is 3134m (error 4.5m). However, the interface depth determined by the method of this invention is 3130m (error 0.5m), which greatly reduces the error of the bottom interface depth.

[0056] Table 1. Data Information for Well M

[0057]

[0058]

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data, characterized in that, Includes the following steps: Step S1: Collect logging cuttings; Step S2: Based on regional sedimentary characteristics and geological design information, the bottom interface of the Permian Shiqianfeng Formation is roughly divided, and the rough division interface is delineated. Step S3: Perform X-ray fluorescence spectroscopy scanning on the logging cuttings to obtain elemental data; Step S4: Perform data processing, analysis, and judgment on the element data, and calculate the interface coefficient JM; Step S5: Correct the coarse interface depth to obtain the bottom interface depth of the Permian Shiqianfeng Formation.

2. The method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data according to claim 1, characterized in that, In step S3, the elemental data is strontium, copper, and barium elemental data.

3. The method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data according to claim 1, characterized in that, In step S3, before performing X-ray fluorescence spectroscopy scanning on the logging-while-drilling cuttings, the false cuttings in the logging-while-drilling cuttings are first manually removed.

4. The method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data according to claim 1, characterized in that, In step S4, the formula for calculating the interface coefficient JM is: JM=Sr 2 / Cu / Ba-X (1) Where JM is the interface coefficient; Sr is the mass percentage of strontium content measured by elemental logging; Cu is the mass percentage of copper content measured by elemental logging; Ba is the mass percentage of barium content measured by elemental logging; and X is the correction coefficient.

5. The method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data according to claim 4, characterized in that, The correction coefficient X ranges from 0.65 to 0.

95.

6. The method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data according to claim 4, characterized in that, The correction coefficient X ranges from 0.7 to 0.

9.

7. The method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data according to claim 4, characterized in that, Both the interface coefficient and the correction coefficient are dimensionless.

8. The method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data according to claim 1, characterized in that, In step S4, the element data is processed and the features are amplified.

9. The method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data according to claim 1, characterized in that, In step S5, the depth of the bottom interface of the Permian Shiqianfeng Formation is further divided based on the coarse interface defined in step S2.

10. The method for determining the bottom interface of the Permian Shiqianfeng Formation using elemental logging data according to claim 9, characterized in that, In step S5, after the second division, the depth at which the interface coefficient JM near the coarse division interface drops sharply from positive to negative is the bottom interface depth of the Permian Shiqianfeng Formation.

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