Clastic rock while-drilling granularity evaluation method based on element logging parameters

Abstract

The invention relates to a clastic rock while-drilling granularity evaluation method based on element logging parameters. The problem of clastic rock reservoir granularity while-drilling analysis is solved by utilizing the element logging parameters. K, Na, Ti, Mn, Ni, Fe and Zr are preferably selected as sensitive parameters for indicating the particle size of the reservoir, a calculation method for the particle size index of the sunken clastic rock reservoir in the West Lake during well logging while drilling is established, and meanwhile, the particle size grading standard of the sunken clastic rock reservoir in the West Lake is established. According to the method, classification while drilling and quantitative evaluation of clastic rock granularity can be rapidly realized, and the method has the advantages of accuracy, rapidness, convenience and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of reservoir evaluation, and particularly relates to a method for evaluating the particle size of clastic rocks while drilling based on element logging parameters. Background Art

[0002] The evaluation of clastic rock reservoirs is a key task in oil and gas reservoir geological exploration, which includes various aspects such as reservoir lithology, physical properties, and hydrocarbon-bearing properties. Among them, the physical properties of the reservoir are affected by factors such as the particle size of clastic rocks, degree of compaction, cementation type, and properties of cementing materials. Moreover, the innate anti-compaction degree of reservoir rocks is affected by the size of clastic particles. Under the same burial depth, the larger the particle size of clastic rocks, the better the physical properties of the reservoir. Therefore, effectively analyzing the particle size of clastic rock reservoirs during the drilling process is a common requirement for rapid reservoir evaluation and analysis of the hydrocarbon accumulation mode.

[0003] Currently, the methods for determining the particle size of clastic rock reservoirs include screening method, laser particle size analysis method, thin section particle size analysis method, image analysis method, etc. However, with the popular application of polycrystalline diamond compact (PDC) bits in major oil and gas fields, the cuttings are finer than those of roller cone bits, and the degree of damage to the original formation particles is high. It is difficult to accurately analyze the particle size of clastic rocks using cuttings. Therefore, the above methods can only use samples taken from drilling cores or sidewall cores for sampling and analysis. The costs of drilling cores and sidewall cores are high, and they can only reflect the local particle size of the reservoir and cannot reflect the longitudinal distribution of the overall particle size. At the same time, since the above methods require analysis operations in the laboratory and the transportation time in remote areas is relatively long, the entire analysis cycle is greatly extended, thereby affecting the timeliness of decision-making.

[0004] CN107688037A discloses a method for determining downhole rock grain size curves using nuclear magnetic resonance (NMR) logging T2 distribution. The method comprises the following steps: S1. preparing experimental cores; S2. analyzing multiple core samples using a nuclear magnetic resonance (NMR) analyzer and a laser particle size analyzer to obtain the NMR T2 distribution and rock grain size distribution curve for each core; S3. measuring the porosity parameters of the multiple cores using a porosity analyzer; S4. collecting and recording formation NMR T2 distribution data and formation porosity parameters using a NMR logging device, with a recording step of 1 point / 0.1 m; S5. selecting a conversion coefficient C value for converting the regional T2 distribution to a grain size distribution curve; S6. obtaining the formation grain size distribution curve; and S7. outputting the calculated results. Yang Ning's team (Yang Ning et al., "Calculation of Grain Size Parameters Using Wavelet Transform of Gamma Log Curves." Modern Geology, 26.4 (2012): 6) calculated grain size parameters such as the median grain size using a binary wavelet transform method based on the natural gamma curve. CN116411958A discloses a method, system, equipment and storage medium for calculating median grain size based on well logging data. The method mainly establishes a model for obtaining the calcium content in the rock skeleton to correct the resistivity, thereby eliminating the influence of calcium cement on the well logging response, and combines natural gamma to eliminate the influence of mud cement. At the same time, based on well logging data such as acoustic wave time difference, neutron and density, a skeleton index parameter is established to eliminate the influence of pore fluid on the well logging response. The corrected resistivity and skeleton index are combined to establish a grain size median calculation model, and the model is calibrated based on the grain size median of the measured core sample to achieve well logging evaluation of the grain size median and accurate lithology identification of the tight conglomerate reservoir.

[0005] However, most of the above methods are based on wireline logging parameters or logging while drilling parameters. Wireline logging is usually performed after drilling is completed or mid-drilling, which is time-sensitive and expensive. While logging while drilling can ensure timeliness, it can usually only collect natural gamma ray, resistivity, neutron, and sonic curves, resulting in low accuracy and high cost and usage requirements. Therefore, a method for evaluating clastic rock grain size that is accurate, fast, convenient, and low-cost is needed. Summary of the invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for evaluating the particle size of clastic rocks while drilling based on element logging parameters, which can quickly realize the classification and quantitative evaluation of the particle size of clastic rocks while drilling, and has the advantages of accuracy, speed, convenience and low cost.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for evaluating the particle size of clastic rocks while drilling based on element logging parameters. The method comprises the following steps:

[0009] (1) Obtain the elemental logging parameters of the clastic rock reservoir in the Xihu Sag, including the contents of major elements, trace elements, and element ratios;

[0010] (2) Screen sensitive parameters according to the sensitivity of elements to grain size response, and the sensitive parameters include K, Na, Ti, Mn, Ni, Fe, and Zr;

[0011] (3) Based on the statistical relationship between element ratios and clastic rock types in the Xihu Sag, establish a calculation formula for the grain size index of the clastic rock reservoir in the Xihu Sag;

[0012] (4) Determine the grain size classification threshold through statistical analysis, and classify the grain size index of the clastic rock reservoir in the Xihu Sag;

[0013] (5) Output the evaluation result of the in - situ grain size of clastic rock according to the real - time calculated grain size index of the clastic rock reservoir in the Xihu Sag.

[0014] The in - situ grain size evaluation method for clastic rock provided by the present invention solves the problem of in - situ analysis of the grain size of clastic rock reservoirs by using elemental logging parameters; preferably selects K, Na, Ti, Mn, Ni, Fe, Zr as sensitive parameters indicating the reservoir grain size, and establishes a calculation method for the grain size index of the clastic rock reservoir in the Xihu Sag during logging while drilling. At the same time, a grain size classification standard for the reservoir in the Xihu Sag area is established. According to this method, the in - situ grading and quantitative evaluation of the grain size of clastic rock can be quickly realized, with the advantages of accuracy, speed, convenience, and low cost.

[0015] When selecting sensitive parameters indicating the reservoir grain size, in the sandstone reservoirs of the Xihu Sag, sandstones with coarser grains usually have better pore-throat preservation ability. Therefore, coarse-grained sandstones tend to have lower matrix and cement contents. At the same time, the samples of low-energy braided river channels in the study area are mainly fine sandstones, with weak hydrodynamic conditions, poor sorting and rounding, and the characteristics of high clay content. The samples of high-energy braided river channels are mainly medium sandstones, with strong hydrodynamic conditions and the characteristics of low clay content. Based on the above factors, sandstone reservoirs with larger grain sizes show lower K and Na element contents in the element logging parameters. Considering that the provenance in the Xihu Sag area is mainly felsic, strong hydrodynamic sorting results in more enrichment of Ti and Fe carried by clay in fine-grained sediments. Mn is easily oxidized to form oxides or hydroxides under oxidizing conditions and is often enriched in sediments in oxidizing environments. However, the Mn content in coarse-grained sediments is usually low because of its weak adsorption ability and easy removal by hydrodynamic sorting. In fine-grained clastic rocks, Mn can be enriched through organic matter complexation or sulfidation in reducing environments, such as anoxic basins and organic matter-rich environments. In fine-grained clastic rocks, Ni is easily adsorbed by clay minerals or organic matter and has a higher content in black shales and mudstones, especially forming sulfides by combining with sulfur in anoxic environments. In the Xihu Sag, there are more clay minerals or residual primary feldspars, and Ti in coarse grains is lost faster than Mn. Zircon heavy minerals are more stable, and an increase in Zr / Ti may indicate long-term transportation or mature deposition. Based on the above analysis, after comparing and analyzing the changes in element logging parameters of reservoirs with different grain sizes, K, Na, Ti, Mn, Ni, Fe, and Zr are preferably selected as sensitive parameters indicating the reservoir grain size.

[0016] Preferably, the clastic rock reservoirs in the Xihu Sag described in step (1) include the clastic rock reservoirs of the Huagang Formation and the Pinghu Formation in the Xihu Sag.

[0017] Preferably, the element logging parameters described in step (1) are measured while drilling or by XRF scanning of cuttings.

[0018] Preferably, the screening of the sensitive parameters described in step (2) is carried out based on the sedimentary environment characteristics and provenance conditions characteristics reflected by the element logging parameters.

[0019] Preferably, the element ratios described in step (3) include Fe / Mn, Mn / Ti, Ni / Ti, and Zr / Ti.

[0020] Preferably, the calculation formula for establishing the grain size index of the clastic rock reservoirs in the Xihu Sag described in step (3) is also based on the statistical relationship between the total content of K+Na and the types of clastic rocks in the Xihu Sag.

[0021] Preferably, the calculation formula for the grain size index of the clastic rock reservoirs in the Xihu Sag described in step (3) is as follows:

[0022]

[0023] Wherein: S y is the clastic rock grain size index of the Xihu Sag, %; R is the correction coefficient of the Xihu Sag, calibrated by the calculation results of adjacent wells or wells in adjacent areas and the conclusions of drilling cores and sidewall cores, dimensionless; Ni is the content of nickel element, %; Ti is the content of titanium element, %; K is the content of potassium element, %; Na is the content of sodium element, %; Zr is the content of zirconium element, %; Fe is the content of iron element, %; Mn is the content of manganese element, %.

[0024] Preferably, the classification of the clastic rock reservoir grain size index in step (4) specifically includes:

[0025] 0 < S y < 0.3 is mudstone or silty mudstone, with a particle size < 0.01 mm, for example, it can be 0.008 mm, 0.005 mm or 0.002 mm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] 0.3 ≤ S y < 0.4 is siltstone or muddy siltstone, with a particle size of 0.01 - 0.1 mm, for example, it can be 0.01 mm, 0.05 mm or 0.1 mm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] 0.4 ≤ S y < 0.7 is fine sandstone, with a particle size of 0.1 - 0.25 mm, for example, it can be 0.1 mm, 0.125 mm or 0.25 mm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0028] 0.7 ≤ S y < 1.2 is medium sandstone, with a particle size of 0.25 - 0.5 mm, for example, it can be 0.1 mm, 0.125 mm or 0.25 mm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0029] 1.2 ≤ S y < 1.5 is gravel-bearing fine sandstone, the particle size of the sandy part is 0.1 - 0.25 mm, for example, it can be 0.1 mm, 0.15 mm or 0.25 mm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable; the particle size of the gravel part > 2 mm, for example, it can be 3 mm, 4 mm or 5 mm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] 1.5 ≤ S y<1.8 is gravel-bearing medium sandstone. The particle size of the sandy part is 0.25 - 0.5 mm, for example, it can be 0.25 mm, 0.3 mm or 0.5 mm, but not limited to the listed values. Other unlisted values within the numerical range are equally applicable; the particle size of the gravel part > 2 mm, for example, it can be 3 mm, 4 mm or 5 mm, but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0031] S y ≥1.8 is glutenite or coarse sandstone. Among them, for glutenite, the particle size of the sandy part is 0.1 - 2 mm, for example, it can be 0.1 mm, 1 mm or 2 mm, but not limited to the listed values. Other unlisted values within the numerical range are equally applicable; the particle size of the gravel part > 2 mm, for example, it can be 3 mm, 4 mm or 5 mm, but not limited to the listed values. Other unlisted values within the numerical range are equally applicable; the particle size of coarse sandstone is 0.5 - 2 mm, for example, it can be 0.5 mm, 1 mm or 2 mm, but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0032] Preferably, the coincidence rate between the calculated real-time clastic rock reservoir grain size index in step (5) and its grading evaluation standard ≥ 75.6%, for example, it can be 75.6%, 80%, 85%, 90% or 95%, but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The clastic rock grain size evaluation method provided by the present invention solves the problem of in-situ analysis of the grain size of clastic rock reservoirs by using element logging parameters; preferably, K, Na, Ti, Mn, Ni, Fe, Zr are used as sensitive parameters indicating the grain size of the reservoir, and a calculation method for the grain size index of the clastic rock reservoir in the Xihu Sag during logging is established. At the same time, a reservoir grain size grading standard for the Xihu Sag area is established. According to this method, the in-situ grading and quantitative evaluation of the clastic rock grain size can be quickly realized, with the advantages of accuracy, speed, convenience and low cost. Description of the Drawings

[0035] Figure 1 is a relationship diagram between the clastic rock type in the Xihu Sag provided by the present invention and the total content of K + Na;

[0036] Figure 2 is a relationship diagram between the clastic rock type in the Xihu Sag provided by the present invention and Fe / Mn;

[0037] Figure 3 is a relationship diagram between the clastic rock type in the Xihu Sag provided by the present invention and Mn / Ti;

[0038] Figure 4 It is a diagram showing the relationship between the clastic rock types in the Xihu Sag and Ni / Ti provided by the present invention;

[0039] Figure 5 It is a diagram showing the relationship between the clastic rock types in the Xihu Sag and Zr / Ti provided by the present invention. Detailed implementation manners

[0040] The technical solution of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0041] The present invention provides a method for evaluating the particle size of clastic rocks while drilling based on element logging parameters. The method for evaluating the particle size of clastic rocks while drilling includes the following steps:

[0042] (1) Obtain the element logging parameters of the clastic rock reservoirs in the Huagang Formation and Pinghu Formation of the Xihu Sag through measurement while drilling or XRF scanning of cuttings, including the contents of major elements, trace elements, and element ratios.

[0043] (2) Based on the sedimentary environment characteristics and provenance conditions characteristics reflected by the element logging parameters, screen sensitive parameters according to the sensitivity of elements to particle size response. The sensitive parameters include K, Na, Ti, Mn, Ni, Fe, and Zr.

[0044] (3) The diagrams showing the relationships between the clastic rock types in the Xihu Sag and the total content of K+Na, Fe / Mn, Mn / Ti, Ni / Ti, and Zr / Ti are respectively as Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 shown. It can be seen from the diagrams that there is a good correlation between the particle size of the clastic rock reservoirs in the Huagang Formation and Pinghu Formation of the Xihu Sag and parameters such as K+Na, Fe / Mn, Mn / Ti, Ni / Ti, and Zr / Ti.

[0045] Based on the statistical relationships between the total content of K+Na, Fe / Mn, Mn / Ti, Ni / Ti, Zr / Ti and the clastic rock types in the Xihu Sag, establish the following calculation formula for the particle size index of the clastic rock reservoirs in the Xihu Sag:

[0046]

[0047] Where: S yφ is the grain size index of clastic rocks in the Xihu Sag, %; R is the correction coefficient of the Xihu Sag, calibrated by the calculation results of adjacent wells or wells in adjacent areas and the conclusions of drilling cores and sidewall cores, dimensionless; Ni is the nickel element content, %; Ti is the titanium element content, %; K is the potassium element content, %; Na is the sodium element content, %; Zr is the zirconium element content, %; Fe is the iron element content, %; Mn is the manganese element content, %.

[0048] (4) Determine the grain size classification threshold through statistical analysis, and classify the grain size index of the clastic rock reservoir in the Xihu Sag. The classification is shown in Table 1.

[0049] Table 1

[0050]

[0051] (5) Output the evaluation result of the grain size of clastic rocks while drilling according to the grain size index of the clastic rock reservoir in the Xihu Sag calculated in real time. The coincidence rate of the grain size index of the clastic rock reservoir in the Xihu Sag calculated in real time and its classification evaluation standard is ≥75.6%.

[0052] Example 1

[0053] This example provides a method for evaluating the grain size of clastic rocks while drilling based on elemental logging parameters. The method for evaluating the grain size of clastic rocks while drilling includes the following steps:

[0054] Obtain the elemental logging parameters of the clastic rock reservoir samples in the Huagang Formation and Pinghu Formation of the Xihu Sag by XRF scanning of cuttings, and screen the sensitive parameters as K, Na, Ti, Mn, Ni, Fe, and Zr. The obtained results are shown in Table 2.

[0055] Table 2

[0056]

[0057]

[0058] It can be seen from Table 2 that there is a good correlation between the clastic rock types in the Xihu Sag and the total content of K+Na, Fe / Mn, Mn / Ti, Ni / Ti, and Zr / Ti.

[0059] Obtain the grain size index of the clastic rock reservoir in the Xihu Sag through real-time calculation, and further obtain the grain size classification of the clastic rock reservoir in the Huagang Formation and Pinghu Formation of the Xihu Sag. The obtained results are shown in Table 3.

[0060] Table 3

[0061]

[0062] It can be seen from Table 3 that the grain size of the clastic rock reservoir in the Huagang Formation and Pinghu Formation of the Xihu Sag is in good compliance with the classification evaluation standard of the grain size index value.

[0063] In summary, the method for evaluating the particle size of clastic rocks while drilling provided by the present invention solves the problem of analyzing the particle size of clastic rock reservoirs while drilling by using elemental logging parameters; preferably, K, Na, Ti, Mn, Ni, Fe, and Zr are used as sensitive parameters indicating the particle size of the reservoir, and a calculation method for the particle size index of clastic rock reservoirs in the Xihu Sag during logging while drilling is established. At the same time, a particle size grading standard for reservoirs in the Xihu Sag area is established. According to this method, the particle size grading and quantitative evaluation of clastic rocks while drilling can be quickly realized, which has the advantages of accuracy, speed, convenience, and low cost.

[0064] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for evaluating the grain size of clastic rocks while drilling based on element logging parameters, characterized in that, The method for evaluating the particle size of clastic rocks while drilling includes the following steps: (1) Obtain the element logging parameters of the clastic rock reservoirs in the Xihu Sag, including the contents of major elements, trace elements, and element ratios; (2) Screen sensitive parameters according to the sensitivity of elements to particle size. The sensitive parameters include K, Na, Ti, Mn, Ni, Fe, and Zr; (3) Based on the statistical relationship between the element ratios and the types of clastic rocks in the Xihu Sag, establish a calculation formula for the particle size index of the clastic rock reservoirs in the Xihu Sag; (4) Determine the particle size grading threshold through statistical analysis and classify the particle size index of the clastic rock reservoirs in the Xihu Sag; (5) Output the evaluation result of the particle size of clastic rocks while drilling according to the particle size index of the clastic rock reservoirs in the Xihu Sag calculated in real time.

2. The method for evaluating the particle size of clastic rock while drilling according to claim 1, wherein The clastic rock reservoirs in the Xihu Sag described in step (1) include the clastic rock reservoirs of the Huagang Formation and the Pinghu Formation in the Xihu Sag.

3. The method for evaluating the particle size of clastic rock while drilling according to claim 1 or 2, characterized in that, The element logging parameters described in step (1) are measured while drilling or by XRF scanning of cuttings.

4. The method for evaluating the particle size of clastic rocks while drilling according to any one of claims 1-3, characterized in that The screening of the sensitive parameters described in step (2) is carried out based on the sedimentary environment characteristics and provenance conditions characteristics reflected by the element logging parameters.

5. The method for evaluating the particle size of clastic rock while drilling according to any one of claims 1-4, characterized in that, The element ratios described in step (3) include Fe / Mn, Mn / Ti, Ni / Ti, and Zr / Ti.

6. The method for evaluating the particle size of clastic rock while drilling according to any one of claims 1-5, characterized in that, The establishment of the calculation formula for the particle size index of the clastic rock reservoirs in the Xihu Sag described in step (3) is also based on the statistical relationship between the total content of K+Na and the types of clastic rocks in the Xihu Sag.

7. The method for evaluating the particle size of clastic rock while drilling according to any one of claims 1-6, characterized in that, The calculation formula for the particle size index of the clastic rock reservoirs in the Xihu Sag described in step (3) is as follows: Where: S y is the clastic rock grain size index of the Xihu Sag, %; R is the correction coefficient of the Xihu Sag, calibrated by the calculation results of adjacent wells or wells in adjacent areas and the conclusions of drilling cores and sidewall cores, dimensionless; Ni is the nickel element content, %; Ti is the titanium element content, %; K is the potassium element content, %; Na is the sodium element content, %; Zr is the zirconium element content, %; Fe is the iron element content, %; Mn is the manganese element content, %.

8. The method for evaluating the particle size of clastic rocks while drilling according to claim 7, wherein The classification of the particle size index of the clastic rock reservoirs in the Xihu Sag described in step (4) specifically includes: 0 < S y <0.3 is mudstone or siltstone mudstone, particle size < 0.01mm; 0.3 ≤ S y <0.4 is siltstone or argillaceous siltstone with a particle size of 0.01 - 0.1 mm; 0.4 ≤ S y <0.7 is fine sandstone with a particle size of 0.1 - 0.25 mm; 0.7 ≤ S y <1.2 is medium sandstone with a particle size of 0.25 - 0.5 mm; 1.2 ≤ S y <1.5 is gravelly fine sandstone, the particle size of the sandy part is 0.1 - 0.25 mm, and the particle size of the gravel part > 2 mm; 1.5≤S y <1.8 is gravelly medium sandstone, the particle size of the sandy part is 0.25 - 0.5 mm, and the particle size of the gravel part is > 2 mm; S y ≥1.8 is glutenite or coarse sandstone. Among them, the particle size of the sandy part in glutenite is 0.1 - 2 mm, and the particle size of the gravel part > 2 mm; the particle size of coarse sandstone is 0.5 - 2 mm.

9. The method for evaluating the particle size of clastic rocks while drilling according to any one of claims 1-8, characterized in that, The coincidence rate between the particle size index of the clastic rock reservoirs in the Xihu Sag calculated in real time described in step (5) and its classification evaluation standard is ≥75.6%.

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