Method and system for determining lower limit of effective reservoir stratum of sandstone

Abstract

The invention provides a method and a system for determining the lower limit of an effective reservoir stratum of sandstone. The method comprises the following steps of: performing borehole collapse correction treatment on data of a natural gamma curve and an interval transit time logging curve; standardizing the natural gamma curve and the interval transit time logging curve; sampling natural gamma and interval transit time values of a single well or multiple wells in the same layer at equal intervals; presetting a first limiting condition, determining a sandstone section, extracting natural gamma and interval transit time values of the sandstone section, and sorting and marking; a system clustering analysis method is adopted to carry out similarity analysis; and based on the difference of the system clustering analysis differentiation distance, setting a second limiting condition, and determining the physical property lower limit of the effective reservoir stratum of the sandstone. According to the method, the natural gamma of the pure mudstone section is used as a base line to distinguish sandstone and mudstone; extracting interval transit time and natural gamma of a sandstone section, performing similarity analysis on two variables of sandstone by adopting a system clustering analysis method, and determining the lower limit of an effective reservoir stratum according to the difference of differentiation distances.

Description

Technical Field

[0001] The invention belongs to the field of oil and natural gas exploitation, and in particular relates to a method and a system for determining the lower limit of an effective sandstone reservoir. Background Art

[0002] At present, the main methods used to determine the lower limit of effective reservoirs include testing method, empirical statistical method, oil occurrence method, mercury injection parameter method, porosity-permeability intersection method, etc. These methods are mainly based on core data and analytical testing, and have the problems of high cost and small application range.

[0003] The present invention designs a method for determining the lower limit of an effective sandstone reservoir, and provides a new technical method for determining the lower limit of an effective sandstone reservoir. The natural gamma (GR) of a pure mudstone section is used as a baseline to distinguish sandstone from mudstone. The acoustic time difference (AC) and natural gamma (GR) of the sandstone section are extracted, and a system cluster analysis method is used to perform similarity analysis on two variables (AC, GR) of the sandstone, and the lower limit of the effective reservoir is determined according to the difference in differentiation distance. Summary of the invention

[0004] The purpose of the present invention is to make up for the shortcomings of the prior art, provide a method and system for determining the lower limit of an effective sandstone reservoir, establish a fast, intuitive and effective technical method for determining the lower limit of an effective sandstone reservoir, and solve the problems of high cost and small application range in the existing methods for determining the lower limit of an effective reservoir.

[0005] In order to solve the above problems, the present invention adopts the following technical solutions:

[0006] In a first aspect, a method for determining the lower limit of an effective sandstone reservoir comprises the following steps:

[0007] Step 1, obtaining natural gamma curve and acoustic time difference logging curve data, and performing borehole collapse correction processing on the natural gamma curve and acoustic time difference logging curve;

[0008] Step 2: standardize the natural gamma ray curve and the acoustic time difference logging curve after correction;

[0009] Step 3: Based on the standardized natural gamma and acoustic time difference values, equally spaced sampling is performed for a single well or multiple wells located in the same layer;

[0010] Step 4: Preset the first restriction condition, determine the sandstone section, extract the natural gamma and acoustic time difference values ​​of the sandstone section, and sort and number the acoustic time difference values;

[0011] Step 5: Based on the time difference of the sound waves and the natural gamma with the marked serial numbers, a system cluster analysis method is used to perform similarity analysis on them;

[0012] Step 6: Based on the differences in the differentiation distances of the system cluster analysis, the second restriction condition is set to determine the lower limit of the physical properties of the effective sandstone reservoir.

[0013] Furthermore, the borehole collapse correction processing of the natural gamma curve and the acoustic time difference logging curve includes: using the natural gamma curve and the acoustic time difference logging curve that are less affected by the borehole collapse, constructing a model curve by means of multivariate linear fitting, and performing slow correction processing on the natural gamma curve and the acoustic time difference logging curve that are more affected by the borehole collapse.

[0014] Furthermore, the first restriction condition is the natural gamma of the pure mudstone section.

[0015] Furthermore, the similarity analysis using the system cluster analysis method includes: using the inter-group connection algorithm to perform similarity analysis on the acoustic time difference and natural gamma that are arranged from large to small and marked with serial numbers.

[0016] Furthermore, the second restriction condition is the acoustic wave time difference value corresponding to the data sample points with obvious differentiation distance.

[0017] In a second aspect, a system for determining a lower limit of an effective sandstone reservoir comprises:

[0018] Acquisition module: acquires natural gamma curve and acoustic time difference logging curve data, and performs borehole collapse correction processing on the natural gamma curve and acoustic time difference logging curve;

[0019] Processing sampling module: standardize the natural gamma curve and acoustic time difference logging curve after correction, and perform equal-space sampling on the natural gamma curve and acoustic time difference logging curve of a single well or multiple wells in the same layer;

[0020] The first determination module: presets a first restriction condition, determines the sandstone segment, extracts the natural gamma and acoustic time difference values ​​of the sandstone segment, and sorts and numbers the acoustic time difference values;

[0021] Analysis module: Based on the time difference of the sound waves and the natural gamma with marked serial numbers, the system cluster analysis method is used to conduct similarity analysis;

[0022] The second determination module: based on the difference of differentiation distances through system cluster analysis, the second restriction condition is set to determine the lower limit of the physical properties of the effective sandstone reservoir.

[0023] The embodiments of the present invention bring the following beneficial effects:

[0024] In the vertical direction, the changes in the lithology and physical properties of the sandstone reservoir can be reflected by the porosity distribution trend, and the porosity can be calculated by the acoustic time difference (or density) logging data. Therefore, the present invention adopts a system cluster analysis method to perform similarity analysis on two variables (AC and GR) of the sandstone. According to the difference in the differentiation distance, the lower limit of the effective sandstone reservoir can be determined quickly, intuitively and effectively, overcoming the limitation that the lower limit of the effective reservoir cannot be determined due to insufficient core data, and is helpful to determine the logging evaluation plan and the oil testing plan for the new well.

[0025] Other features and advantages of the present invention will be described in the following description, and some features will become apparent from the description or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flow chart of a method for determining the lower limit of an effective sandstone reservoir provided by an embodiment of the present invention;

[0028] Figure 2 A comprehensive histogram of a single well of Well B16-84 provided in an embodiment of the present invention

[0029] Figure 3 A schematic diagram of the inter-group linkage method for system cluster analysis provided by an embodiment of the present invention;

[0030] Figure 4 This is an example diagram of data samples provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1: Figure 1 As shown, an embodiment of the present invention provides a method for determining the lower limit of an effective sandstone reservoir, comprising the following steps:

[0033] Step 1, obtaining natural gamma curve and acoustic time difference logging curve data, and performing borehole collapse correction processing on the natural gamma curve and acoustic time difference logging curve;

[0034] Specifically, the natural gamma ray (GR) curve and acoustic transit time (AC) logging curve, which are less affected by borehole collapse, are used to construct the model curve through multivariate linear fitting. The natural gamma ray (GR) curve and acoustic transit time (AC) logging curve, which are more affected by borehole collapse, are subjected to slow correction processing to eliminate the impact of borehole collapse.

[0035] Step 2: standardize the natural gamma ray curve and the acoustic time difference logging curve after correction;

[0036] Specifically, for the logging curve data collected by instruments of different periods and models, standard wells are selected, and the natural gamma (GR) curve and acoustic time difference (AC) logging curve are standardized and corrected to the measurement values ​​under the same measurement environment.

[0037] Step 3, sampling the natural gamma (GR) and acoustic time difference (AC) values ​​of a single well or multiple wells located in the same layer at equal intervals;

[0038] Specifically, Figure 2 As shown, through formation data comparison, for a certain layer, the natural gamma (GR) and acoustic time difference (AC) values ​​of a single well or multiple wells are extracted according to a certain sampling interval (for example, 0.125m sampling interval).

[0039] Step 4: Preset the first restriction condition, determine the sandstone segment, extract the natural gamma (GR) and acoustic time difference (AC) values ​​of the sandstone segment, and sort and number the acoustic time difference (AC) values;

[0040] Specifically, the natural gamma (GR) of the pure mudstone section is used as the baseline and the first restriction condition to distinguish sandstone from mudstone. For example, in this area, the natural gamma (GR) value less than 90 is considered sandstone. The natural gamma (GR) and acoustic transit time (AC) values ​​of the sandstone section are extracted to expand the selected area, and the acoustic transit time (AC) values ​​are sorted from large to small and marked with serial numbers.

[0041] Step 5: Based on the acoustic time difference (AC) value and natural gamma (GR) value of the marked serial number, a system cluster analysis method is used to perform similarity analysis on them;

[0042] Specifically, a systematic cluster analysis method was used, and an inter-group linkage algorithm was used to conduct a similarity analysis on the acoustic time difference (AC) and natural gamma (GR) that were arranged from large to small and labeled with serial numbers.

[0043] In this embodiment, if Figure 3 As shown, the acoustic time difference (AC) and natural gamma (GR) are marked with serial numbers A1, A2, A3, A4, A5...

[0044] Step 6: Based on the difference of the differentiation distance of the system cluster analysis, the second restriction condition is set to determine the lower limit of the physical properties of the effective sandstone reservoir;

[0045] Specifically, according to the difference of differentiation distance in system cluster analysis, the acoustic time difference (AC) value corresponding to the data sample point with obvious differentiation distance is read, and this value is used as the second restriction condition and the lower limit of the physical property of the effective sandstone reservoir.

[0046] Furthermore, based on the characteristic that the larger the acoustic time difference (AC) value, the better the corresponding rock physical properties, and the difference in differentiation distance of the system cluster analysis, the data samples with small acoustic time difference (AC) values ​​and obvious differentiation distances are read, and the acoustic time difference (AC) value is used as the second restriction condition and as the lower limit of the physical properties of the effective sandstone reservoir.

[0047] In this embodiment, if Figure 4 As shown in the figure, there is an obvious differentiation distance between A1 to A28 in this area and other data, so the acoustic time difference (AC) value of 226.481 (rounded to 227) corresponding to A28 is taken as the lower limit of the effective sandstone reservoir. Therefore, the lower limit of the sandstone in this area is the natural gamma (GR) value of 90 (the corresponding natural gamma value of sandstone is less than 90), and the lower limit of the effective sandstone reservoir is the acoustic time difference (AC) value of 227 (the corresponding acoustic time difference value of the effective reservoir is greater than 227).

[0048] Embodiment 2: A system for determining the lower limit of an effective sandstone reservoir, comprising:

[0049] Acquisition module: acquires natural gamma curve and acoustic time difference logging curve data, and performs borehole collapse correction processing on the natural gamma curve and acoustic time difference logging curve;

[0050] Processing sampling module: standardize the natural gamma curve and acoustic time difference logging curve after correction, and perform equal-space sampling on the natural gamma curve and acoustic time difference logging curve of a single well or multiple wells in the same layer;

[0051] The first determination module: presets a first restriction condition, determines the sandstone segment, extracts the natural gamma and acoustic time difference values ​​of the sandstone segment, and sorts and numbers the acoustic time difference values;

[0052] Analysis module: Based on the time difference of the sound waves and the natural gamma with marked serial numbers, the system cluster analysis method is used to conduct similarity analysis;

[0053] The second determination module: based on the difference of differentiation distances through system cluster analysis, the second restriction condition is set to determine the lower limit of the physical properties of the effective sandstone reservoir.

[0054] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for determining the lower limit of an effective sandstone reservoir, characterized in that: The following steps are involved: Step 1, obtaining natural gamma curve and acoustic time difference logging curve data, and performing borehole collapse correction processing on the natural gamma curve and acoustic time difference logging curve; Step 2: standardize the natural gamma ray curve and the acoustic time difference logging curve after correction; Step 3: Based on the standardized natural gamma and acoustic time difference values, equally spaced sampling is performed for a single well or multiple wells located in the same layer; Step 4: Preset the first restriction condition, determine the sandstone section, extract the natural gamma and acoustic time difference values ​​of the sandstone section, and sort and number the acoustic time difference values; Step 5: Based on the time difference of the sound waves and the natural gamma with the marked serial numbers, a system cluster analysis method is used to perform similarity analysis on them; Step 6: Based on the differences in the differentiation distances of the system cluster analysis, the second restriction condition is set to determine the lower limit of the physical properties of the effective sandstone reservoir.

2. The method for determining the lower limit of an effective sandstone reservoir according to claim 1, wherein in step 1, the natural gamma ray curve and the acoustic time difference logging curve are subjected to borehole collapse correction processing, characterized in that: The natural gamma curve and sonic time difference logging curve which are less affected by borehole collapse are used to construct the model curve through multivariate linear fitting, and the natural gamma curve and sonic time difference logging curve which are more affected by borehole collapse are subjected to slow correction.

3. The method for determining the lower limit of an effective sandstone reservoir according to claim 1, characterized in that: The first limiting condition in step 4 is the natural gamma of the pure mudstone section.

4. The method for determining the lower limit of an effective sandstone reservoir according to claim 1, wherein in step 5, a system cluster analysis method is used to perform similarity analysis, characterized in that: The inter-group linkage algorithm is used to conduct similarity analysis on the acoustic time differences and natural gammas that are arranged from large to small and labeled with serial numbers.

5. The method for determining the lower limit of an effective sandstone reservoir according to claim 1, characterized in that: The second restriction condition in step 6 is the acoustic wave time difference value corresponding to the data sample point with obvious differentiation distance.

6. A system using the method for determining the lower limit of an effective sandstone reservoir according to claim 1, characterized in that: include, Acquisition module: acquires natural gamma curve and acoustic time difference logging curve data, and performs borehole collapse correction processing on the natural gamma curve and acoustic time difference logging curve; Processing sampling module: standardize the natural gamma curve and acoustic time difference logging curve after correction, and perform equal-space sampling on the natural gamma curve and acoustic time difference logging curve of a single well or multiple wells in the same layer; The first determination module: presets a first restriction condition, determines the sandstone segment, extracts the natural gamma and acoustic time difference values ​​of the sandstone segment, and sorts and numbers the acoustic time difference values; Analysis module: Based on the time difference of the sound waves and the natural gamma with marked serial numbers, the system cluster analysis method is used to conduct similarity analysis; The second determination module: based on the difference of differentiation distances through system cluster analysis, the second restriction condition is set to determine the lower limit of the physical properties of the effective sandstone reservoir.

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