Deposited clastic rock mineral content prediction method based on acoustic logging time difference parameters

Abstract

The invention discloses a sedimentary clastic rock mineral content prediction method based on an acoustic logging time difference parameter, and relates to the technical field of geophysical research and application, the method comprises the following steps: obtaining the interval transit time value of each measurement point of drilling acoustic logging, and calculating the porosity of a unit layer corresponding to each measurement point of the drilling acoustic logging time difference parameter; correcting the porosity of the unit layer corresponding to each measuring point to obtain a corrected value; constructing a sedimentary clastic rock mineral content prediction model, and inputting the correction value into the sedimentary clastic rock mineral content prediction model to obtain the mineral content of a unit layer corresponding to each measurement point; and based on the mineral content of the unit layer corresponding to each measuring point, the mineral content in the drilling rock stratum is given according to the requirements of different well depth sections. The method solves the problems of complex technology, high cost, long data acquisition period, poor timeliness and the like for acquiring the mineral content in the stratum lithology, can quickly acquire the drill hole carbonate mineral content curve, and is high in refinement degree.

Description

Technical Field

[0001] The present invention relates to the field of geophysical research and application technology, and more particularly to a method for predicting the mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters. Background Art

[0002] In the exploration and development process of sandstone-type uranium deposits, carbonate mineral content is a very important parameter. Under the current technical background and technical status, the collection of carbonate content in formation lithology is basically measured by chemical analysis under laboratory conditions. The technology is complex, the cost is high, the data acquisition cycle is long, and there is a lack of systematicness and refinement. Although neutron-density logging and element capture spectrum logging (ECS) can also be used to invert the carbonate mineral content, the logging cost is greatly increased, which is not conducive to cost reduction and efficiency improvement, and lacks economic practicality.

[0003] Therefore, how to provide a method for predicting the mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a method for predicting the mineral content of sedimentary clastic rocks based on the time difference parameters of acoustic logging, which solves the problems of complex technology for obtaining mineral content in formation lithology, high cost, long data acquisition cycle, and poor timeliness. At the same time, it can quickly obtain the carbonate mineral content curve of the borehole with a high degree of refinement.

[0005] To achieve the above-mentioned object, the present invention adopts the following technical solution: a method for predicting the mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters, comprising: obtaining acoustic time difference values of each measuring point of borehole acoustic logging, and calculating the porosity of the unit layer corresponding to each measuring point of the borehole acoustic logging time difference parameters based on the acoustic time difference values;

[0006] Correct the porosity of the unit layer corresponding to each measuring point to obtain the correction value;

[0007] Constructing a sedimentary clastic rock mineral content prediction model, inputting the correction value into the sedimentary clastic rock mineral content prediction model, and obtaining the mineral content of the unit layer corresponding to each measuring point;

[0008] Based on the mineral content of the unit layer corresponding to each measuring point, the mineral content in the drilled rock layer is given according to the requirements of different well depth sections.

[0009] Preferably, data on the mineral content and porosity of sedimentary clastic rocks in core samples of boreholes in the working area are obtained, and a sedimentary clastic rock mineral content prediction model is constructed based on the data.

[0010] Preferably, the mineral content is carbonate mineral content.

[0011] Preferably, the sedimentary clastic rock mineral content prediction model is expressed as:

[0012] y=a*ln(x)+b;

[0013] Where y represents the mineral content in sedimentary clastic rock, x represents the porosity of sedimentary clastic rock, and a and b are both constants.

[0014] Preferably, calculating the porosity of the unit layer corresponding to each measuring point of the borehole acoustic logging time difference parameter based on the acoustic wave time difference value includes:

[0015] DELT=PHI e *S xo *DELT W +PHI e *(1-S xo )*DELT h +V sh *DELT sh +(1-V sh -PHI e )*DELT i ;

[0016] Among them, DELT represents the well logging reading; DELT W Indicates the well logging reading in water; DELT h Indicates the well logging reading in gas; DELT sh Indicates the logging reading in mud; DELT i Represents the well log reading in the skeleton; PHI e represents effective porosity; S xo Indicates the water saturation in the intrusion zone (decimal); V sh Indicates the volume of mud.

[0017] Preferably, the porosity of the unit layer corresponding to each measuring point is corrected to obtain a corrected value, including:

[0018] PHI i =PHI e / C p ;

[0019] Among them, PHI i PHI represents the porosity of the unit layer after compaction correction; e C represents the effective porosity of the unit layer corresponding to each measuring point calculated by the acoustic wave time difference; p Represents the compaction correction factor.

[0020] Preferably, based on the mineral content of the unit layer corresponding to each measuring point, the mineral content of the drilled rock layer is given according to the requirements of different well depth sections, including:

[0021]

[0022] in, Indicates the mineral content in the rock layer encountered; y i Indicates the mineral content in the unit layer corresponding to each measuring point; i represents the serial number of the acoustic logging measuring point.

[0023] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a method for predicting the mineral content of sedimentary clastic rocks based on the acoustic logging time difference parameters, which solves the problems of complex technology for obtaining carbonate mineral content in stratum lithology, high cost, long data acquisition cycle, and poor timeliness. At the same time, the carbonate mineral content curve of the drill hole can be quickly obtained with a high degree of refinement, which is of great benefit to the quantitative classification of the permeability of the stratum and can provide strong data support for the design of uranium in-situ leaching process. The present invention is also applicable to the exploration and development of other mineral resources in sedimentary clastic rocks. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0025] Figure 1 A flow chart of a method for predicting mineral content in sedimentary clastic rocks based on acoustic logging time difference parameters provided by the present invention.

[0026] Figure 2 This is a schematic diagram of the single-transmitter, dual-receiver acoustic logging principle provided by an embodiment of the present invention.

[0027] Figure 3 This is a fitting diagram of the porosity (PHI) and carbonate mineral content of drill core samples in a certain area provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0029] The embodiment of the present invention discloses a method for predicting the mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters, such as Figure 1As shown, it includes: obtaining the acoustic wave time difference value of each measuring point of the borehole acoustic logging, and calculating the porosity of the unit layer corresponding to each measuring point of the borehole acoustic logging time difference parameter based on the acoustic wave time difference value;

[0030] Correct the porosity of the unit layer corresponding to each measuring point to obtain the correction value;

[0031] Constructing a sedimentary clastic rock mineral content prediction model, inputting the correction value into the sedimentary clastic rock mineral content prediction model, and obtaining the mineral content of the unit layer corresponding to each measuring point;

[0032] Based on the mineral content of the unit layer corresponding to each measuring point, the mineral content in the drilled rock layer is given according to the requirements of different well depth sections.

[0033] In geophysical exploration, acoustic logging is a key technology for obtaining rock physical parameters by measuring the propagation characteristics of acoustic waves in formations. Its core is to analyze information such as acoustic wave velocity (time difference), amplitude attenuation, and waveform characteristics to address the following geological and engineering problems: formation porosity evaluation, lithology identification and stratigraphic division, fracture and anisotropy analysis, formation pressure prediction (abnormally high pressure detection, drilling safety warning), mechanical property parameter calculation (elastic modulus estimation, rock brittleness evaluation), oil and gas detection and saturation estimation, engineering geological problem diagnosis, and special applications (shear wave anisotropy imaging, seismic calibration, and synthetic seismic recording).

[0034] The basic principle of acoustic logging is to first establish an artificial sound field in the well and then measure the propagation time of the sound wave through the rock formation. In order to effectively eliminate the influence of mud and well diameter on acoustic logging data, the acoustic logging device widely used in actual work is a single-transmitter, dual-receiver device. That is, a single sound source transmits a sound pulse with a certain sound power, direction and frequency characteristics into the well, and then uses two receiving units to measure the propagation time of the sound wave through the rock formation. Figure 2 shown.

[0035] The relationship between the propagation characteristics of sound waves in rock formations and the physical properties of the rock formations is shown in formula (1). The specific formula may vary depending on different studies or applications, but it usually involves the acoustic time difference (DT) and other related parameters.

[0036] s=(1-Tm)DT (1)

[0037] Where s represents the formation factor, which represents the acoustic formation factor; Tm represents a constant, whose value may depend on the type of rock; DT represents the acoustic time difference, which represents the time it takes for the sound wave to propagate in the rock formation.

[0038] Specifically, the mineral content is carbonate mineral content.

[0039] Among them, the study of carbonates in sedimentary clastic rocks is mainly used for reservoir evaluation and diagenetic history research. For example, a high content of carbonate cement (>10%) may significantly reduce the porosity of sandstone reservoirs; the degree of dolomitization (Mg / Ca ratio) can be used to infer the properties of paleofluids, etc.

[0040] In sedimentary clastic rocks, carbonates occur in various forms, which are mainly affected by the sedimentary environment, diagenesis, and later fluid activity. Common forms include:

[0041] ① Cement: Carbonate minerals fill the intergranular pores of clastic particles, forming a cemented structure. Characteristics: Cement often occurs in the form of granular, intergranular, or rim-shaped cements, significantly affecting rock porosity and permeability.

[0042] ② Replacement products: Carbonate minerals replace detrital particles or early cements through diagenesis. Characteristics: Formation of pseudo-structures.

[0043] ③ Authigenic Carbonate: Microcrystalline or fine-crystalline carbonate minerals that precipitate directly during diagenesis. Characteristics: Usually associated with changes in pore water chemistry.

[0044] ④Pore-filling Carbonate: Carbonate minerals fill secondary dissolution pores or cracks.

[0045] ⑤ Detrital Carbonate Clasts: Carbonate rock fragments from the parent rock, mixed into the detrital sediments.

[0046] The quantification of carbonate content requires a combination of mineralogical, geochemical and petrological methods. Commonly used methods are as follows:

[0047] ①Thin-section Analysis:

[0048] Principle: Observe the morphology, distribution and proportion of carbonate minerals in thin sections using a polarizing microscope.

[0049] Methods: The area percentage of carbonate minerals was calculated using the point counting method or image analysis software.

[0050] Applicability: Suitable for qualitative and semi-quantitative analysis of cements or replaced carbonates, but with lower accuracy for microcrystalline or cryptocrystalline carbonates.

[0051] ②Chemical Dissolution:

[0052] Principle: Rock powder is reacted with dilute hydrochloric acid (HCl), the volume of CO2 released or the weight loss is measured, and the total carbonate content (expressed as CaCO3 equivalent) is calculated.

[0053] Formula: Carbonate content (wt.%) = (difference in sample mass before and after reaction / initial sample mass) × 100.

[0054] Applicability: Rapidly determines total carbonate content, but cannot distinguish between different carbonate minerals.

[0055] ③X-ray Diffraction (XRD):

[0056] Principle: Quantitatively analyze the relative content of carbonate minerals such as calcite and dolomite through the intensity of mineral diffraction peaks.

[0057] Steps: After the sample is crushed, it is compared with the standard substance and the ratios are calculated using the Rietveld refinement method.

[0058] Advantages: can distinguish different carbonate minerals with high accuracy (error <5%).

[0059] ④ Cathodoluminescence (CL) and scanning electron microscopy (SEM-EDS):

[0060] Cathodoluminescence: Identify the generation or origin of cements through the luminescence characteristics of carbonate minerals.

[0061] Scanning electron microscopy: Combined with energy spectrum analysis, it can determine the carbonate composition in the micro area.

[0062] ⑤ Geochemical Logging Methods:

[0063] Neutron-density logging: Use the crossplot of neutron porosity and density logging to identify carbonate minerals.

[0064] Element Capture Spectroscopy (ECS): By measuring the Ca and Mg content in the formation, the carbonate mineral content is inverted.

[0065] In a specific embodiment of the present invention, acoustic logging is a commonly used technical means in geophysical exploration. The geological information carried in its parameters is timely, and there is an essential correlation between its parameter values and the carbonate content in the lithology of the formation. A method for rapidly estimating the carbonate mineral content in sedimentary debris using the time difference parameters of acoustic logging will better solve the problems in the existing technology.

[0066] Specifically, data on the mineral content and porosity of sedimentary clastic rocks in drill core samples in the working area are obtained, and a sedimentary clastic rock mineral content prediction model is constructed based on the data.

[0067] In a specific embodiment of the present invention, a sedimentary clastic rock mineral content prediction model is constructed based on the relationship between porosity and carbonate mineral content in sedimentary clastic rocks: relevant data on sedimentary clastic rock mineral content and porosity of borehole core samples in the working area are fully collected and sorted out, and a sedimentary clastic rock mineral content prediction model is constructed based on the relationship between rock formation porosity and carbonate mineral content in a specific area by using the correlation analysis principle. The porosity of borehole core samples in a certain area (PHI e ) and carbonate mineral content analysis data are shown in Table 1.

[0068] Table 1 Porosity of core samples in a certain area (PHI e ) and carbonate mineral content analysis data list

[0069]

[0070]

[0071] The fitting diagram of the porosity (PHI) of the drill core samples and the carbonate mineral content is shown in the figure below: Figure 3 As shown, we can get:

[0072] y=-14.9ln(x)+52.48 (2)

[0073] Where: y represents the carbonate mineral content in sedimentary clastic rock (%); x represents the porosity of sedimentary clastic rock (%); considering that there are generally regional differences in geological environments, some universal laws or empirical data models must fully consider this influencing factor before application. Based on this, formula (2) can be expressed as formula (3).

[0074] Specifically, the sedimentary clastic rock mineral content prediction model is expressed as:

[0075] y=a*ln(x)+b (3)

[0076] Among them, y represents the carbonate mineral content in sedimentary clastic rock (%); x represents the porosity of sedimentary clastic rock (%); a represents a constant, which is related to regional geological background, stratigraphic factors, rock properties and other parameters; b represents a constant, which is related to factors such as sonic logging equipment and drilling geometry parameters.

[0077] Specifically, the porosity of the unit layer corresponding to each measuring point of the borehole acoustic logging time difference parameter is calculated based on the acoustic wave time difference value, as shown in formula (4):

[0078] DELT=PHIe *S xo *DELT W +PHI e *(1-S xo )*DELT h +V sh *DELT sh +(1-V sh -PHI e )*DELT i (4)

[0079] DELT represents the well logging reading in microseconds per meter (μs / m); W Indicates the logging reading in 100% water, in microseconds per meter (μs / m); DELT h Indicates the logging reading in 100% gas, in microseconds per meter (μs / m); DELT sh Indicates the logging reading in 100% mud, in microseconds per meter (μs / m); DELT i Indicates the logging reading in 100% skeleton, in microseconds per meter (μs / m); PHI e represents effective porosity; S xo Indicates the water saturation in the intrusion zone (decimal); V sh Indicates the volume of mud. V i represents the component volume of skeletal sandstone;

[0080] Specifically, the porosity of the unit layer corresponding to each measuring point is corrected to obtain a correction value, including:

[0081] PHI i =PHI e / C p (5)

[0082] Among them, PHI i PHI represents the porosity of the unit layer after compaction correction; e C represents the effective porosity of the unit layer corresponding to each measuring point calculated by the acoustic wave time difference; p represents the compaction correction factor, C p =1.68-0.0002D. D represents the depth of the formation, in meters (m).

[0083] In the embodiment of the present invention, the porosity of the unit layer corresponding to the time difference parameter of each measuring point of the borehole acoustic logging is estimated: the acoustic time difference parameter value obtained at each measuring point of the acoustic logging is substituted into formula (4) to calculate the effective porosity (PHI) of the unit layer corresponding to each measuring point e). In general, the detection range of acoustic transit time logging is within the mud invasion zone. Due to the action of various pressures during drilling, the gas space in the rock within the mud invasion zone is often completely filled with water. Therefore, in the specific calculation, formula (4) can be simplified to three terms: mud, sand, and water.

[0084] According to practical experience, the effective porosity of the unit layer corresponding to each measuring point calculated based on the acoustic logging time difference parameters needs to be compacted, as shown in formula (5).

[0085] Estimate the carbonate mineral content of the unit layer corresponding to the time difference parameters of each measuring point of borehole acoustic logging: the effective porosity (PHI) of each measuring point corresponding to the unit layer calculated by the time difference parameters of acoustic logging is used to calculate the effective porosity (PHI) of each measuring point. e ) is inserted into formula (2) after compaction correction to estimate the carbonate mineral content in the unit layer corresponding to each measuring point.

[0086] Specifically, based on the mineral content of the unit layer corresponding to each measuring point, the mineral content of the drilled rock layer is given according to the requirements of different well depth sections, including:

[0087]

[0088] in, Indicates the mineral content in the rock layer encountered, %; y i Indicates the mineral content in the unit layer corresponding to each measuring point, %; i represents the serial number of the acoustic logging measuring point.

[0089] Among them, the carbonate mineral content in a given drilled rock layer is estimated: the estimated carbonate mineral content in the unit layer corresponding to each measuring point is substituted into formula (6) and the arithmetic mean is calculated, as shown in Table 2.

[0090] Table 2 Comparison of carbonate mineral content in core samples analyzed from a certain area and calculated results from acoustic logging

[0091]

[0092] Looking at Table 2, among the 11 given well sections, the carbonate mineral content in the rock formation calculated using the acoustic logging time difference parameters is compared with the core sample analysis results. Only one well section has an error greater than 10%, accounting for 9.10%. The errors of the remaining well sections are all within the range of ±10%.

[0093] Analysis of the cause of the error: The acoustic time difference parameters are obtained through acoustic logging under the original geological background conditions. The carbonate mineral content in the drilled stratum lithology estimated by them contains information about the original geological background to a certain extent. Once the core rock samples are collected, they are no longer in the original geological environment of the samples. Therefore, there must be a certain difference between the carbonate mineral content obtained by sample testing under laboratory conditions and the carbonate mineral content calculated using the acoustic logging time difference parameters. This difference should be an in-situ property.

[0094] The embodiments of the present invention have the following beneficial effects:

[0095] ① It can replace chemical analysis methods to quickly obtain the carbonate mineral content in the lithology of the formation without increasing costs. The data acquisition cycle is short and it has strong timeliness and cost-saving and efficiency-enhancing properties.

[0096] ② The carbonate mineral content curve of the drill hole can be quickly obtained to provide data support for the design of uranium in-situ leaching process.

[0097] ③ It can quickly provide the carbonate mineral content in the lithology of any well depth section as needed, that is, the carbonate mineral content of the entire series of lithology of the drilling hole, with a high degree of refinement and strong systematicity.

[0098] ④ The obtained drilling carbonate mineral content curve can be used to quantitatively divide the permeability of the formation.

[0099] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0100] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting the mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters, characterized in that: include: Acquiring acoustic transit time values at each measuring point of borehole acoustic logging, and calculating the porosity of a unit layer corresponding to each measuring point of the borehole acoustic logging transit time parameter based on the acoustic transit time values; Correct the porosity of the unit layer corresponding to each measuring point to obtain the correction value; Constructing a sedimentary clastic rock mineral content prediction model, inputting the correction value into the sedimentary clastic rock mineral content prediction model, and obtaining the mineral content of the unit layer corresponding to each measuring point; Based on the mineral content of the unit layer corresponding to each measuring point, the mineral content in the drilled rock layer is given according to the requirements of different well depth sections.

2. The method for predicting the mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters according to claim 1, characterized in that: Obtain data on the mineral content and porosity of sedimentary clastic rocks from drill core samples in the work area, and construct a sedimentary clastic rock mineral content prediction model based on the data.

3. The method for predicting the mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters according to claim 1, characterized in that: The mineral content mentioned is the carbonate mineral content.

4. The method for predicting mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters according to claim 1, characterized in that: The sedimentary clastic rock mineral content prediction model is expressed as: y=a*ln(x)+b; Where y represents the mineral content in sedimentary clastic rock, x represents the porosity of sedimentary clastic rock, and a and b are both constants.

5. The method for predicting the mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters according to claim 1, characterized in that: Calculating the porosity of the unit layer corresponding to each measuring point of the borehole acoustic logging time difference parameter based on the acoustic wave time difference value includes: DELT=PHI e *S xo *DELTA W +PHI e *(1-S xo )*DELTA h +V sh *DELTA sh +(1-V sh -PHI e )*DELTA i ; Among them, DELT represents the well logging reading; DELT W Indicates the well logging reading in water; DELT h Indicates the well logging reading in gas; DELT sh Indicates the logging reading in mud; DELT i Represents the well log reading in the skeleton; PHI e represents effective porosity; S xo Indicates the water saturation in the intrusion zone; V sh Indicates the volume of mud.

6. The method for predicting the mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters according to claim 5, characterized in that: Correct the porosity of the unit layer corresponding to each measuring point to obtain the correction value, including: FLY i PHI e / C p ; Among them, PHI i PHI represents the porosity of the unit layer after compaction correction; e C represents the effective porosity of the unit layer corresponding to each measuring point calculated by the acoustic wave time difference; p Represents the compaction correction factor.

7. The method for predicting mineral content of sedimentary clastic rocks based on acoustic logging time difference parameters according to claim 1, characterized in that: Based on the mineral content of the unit layer corresponding to each measuring point, the mineral content of the drilled rock layer is given according to the requirements of different well depth sections, including: in, Indicates the mineral content in the rock layer encountered; y i Indicates the mineral content in the unit layer corresponding to each measuring point; i represents the serial number of the acoustic logging measuring point.

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