Natural gas maturity continuous detection method based on drilling debris tank head gas
By collecting and processing the top gas of the cuttings tank during drilling, and using light hydrocarbon components and carbon isotope analysis, a continuous natural gas maturity detection method was constructed. This method solves the problems of high cost and low accuracy of traditional methods, and realizes efficient, low-cost, and real-time detection of deep-sea oil and gas exploration.
Patent Information
- Application Number
- CN202511592820.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-03
- Publication Date
- 2026-01-09
AI Technical Summary
Traditional oil and gas maturity assessment methods are costly, polluting, and difficult to guarantee analytical accuracy. Furthermore, they are difficult to achieve continuous, low-cost, and high-precision detection in the high-temperature and high-pressure environment of the deep sea.
By collecting mud gas and cuttings samples in real time during drilling, and using a graded processing procedure including screening, washing, sealing, preservation and heating, maturity analysis is performed using light hydrocarbon components and carbon isotopes of the cuttings tank top gas, thus constructing a continuous detection system.
It enables continuous, low-cost, and high-precision natural gas maturity detection in deep-sea oil and gas exploration, avoiding the omission of key geological information, adapting to various oil-based mud systems, meeting the needs of real-time exploration decision-making, and reducing detection costs.
Smart Images
Figure CN121298949A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a natural gas maturity continuous detection method, in particular to a natural gas maturity continuous detection method based on drilling cuttings tank top gas. BACKGROUND
[0002] In the field of deep-sea oil and gas exploration, accurate evaluation of oil and gas maturity is a core technical link for resource exploration and development. However, the traditional evaluation method highly depends on core and oil and gas sampling analysis, and has the following limitations: (1) High economic and technical threshold, need to call special equipment such as drilling rig or logging ship, long operation cycle and high comprehensive cost, and downhole operation of complex tools is easy to cause engineering risks such as sticking and instrument failure; (2) Difficult to control sample pollution, invasion of drilling fluid filtrate in wellbore will cause sample failure, and multiple prevention and control mechanisms need to be established but are difficult to implement on site; (3) Limited geological information representation, discrete sampling mode is difficult to obtain continuous well section data, and small volume samples are easy to miss key geological characteristics, and spatial resolution is insufficient.
[0003] In addition, the existing technical system also faces double contradictions: although the oil-based mud system improves drilling efficiency, the hydrocarbon components may interfere with the mud gas and cuttings tank top gas geochemical characteristics, resulting in distortion of core parameters such as carbon isotope; although the Flair fluid logging technology introduces quantitative constant temperature degassing process, due to the high solubility of heavy hydrocarbon (C 5+ ) and the time constraint of degassing, the identification efficiency of light hydrocarbon components in mud gas is low, and it is difficult to truly reflect the underground fluid characteristics. The processing of cuttings samples may also encounter component loss or microbial degradation during transportation and preservation, and the traditional detection process needs multiple sampling verification, resulting in poor repeatability, especially in deep-sea high temperature and high pressure extreme environment, sample stability problem is further highlighted, and conventional preservation technology is difficult to guarantee analysis accuracy.
[0004] Therefore, it is urgent to break through the technical bottleneck, develop a continuous, low-cost and high-precision natural gas maturity detection method suitable for oil-based mud environment, and build a whole-chain technical solution from real-time sampling downhole to rapid analysis on ground, so as to realize dynamic monitoring and accurate description of oil and gas maturity index. SUMMARY
[0005] The present application aims to provide a natural gas maturity continuous detection method based on drilling cuttings tank top gas, to solve the problems of high cost, serious pollution, multiple limitations and difficulty in guaranteeing analysis accuracy in the traditional evaluation and detection method of oil and gas maturity.
[0006] To achieve the above purpose, the specific scheme is as follows: A natural gas maturity continuous detection method based on drilling cuttings tank top gas, comprising the steps of: S1, cutting sample processing, fresh cuttings were fished at the outlet of the vibrating screen, 30 mesh nylon mesh was used to assist screening, and impurity particles with a particle size greater than 5 mm were removed; then the surface of the cuttings was slowly washed with a mist spray using deionized water at a water flow pressure of 0.1-0.2 MPa; during the washing process, the surface smoothness of the cuttings, metal debris and drilling fluid additive clumps were removed; S2: sample collection, sealed sampling was completed within 30 minutes after the cuttings were transferred to the platform; about 300 g of washed cuttings were picked and quickly loaded into a 300 ml glass headspace bottle; the bottle was continuously purged with nitrogen at a flow rate of 2 L / min for 30 seconds, after the purging was completed, it was immediately sealed with a screw cap with a polytetrafluoroethylene gasket, and the depth and sampling time were marked; S3: sample storage and transportation, the cuttings headspace bottle was placed upright in a portable refrigerator, and was sent to the laboratory within 24 hours for sample analysis; S4: water bath heating, the cuttings headspace bottle was taken out of the refrigerator, after balancing to room temperature, it was placed in a constant temperature water bath device for water bath heating; after heating, the headspace bottle was taken out and naturally cooled to room temperature; S5: test analysis, initial temperature 35℃, keep for 2 minutes; linearly increase the temperature to 200℃ at a rate of 4℃ / min, and keep at 200℃ for 20 minutes to ensure that the C8 light hydrocarbon components with high carbon number completely flow out; after the end of the temperature rising program, the concentration of C4-C8 light hydrocarbon compounds was determined, and the light hydrocarbon parameter ratio of isobutane / n-butane, 2,4-dimethylpentane / 2,3-dimethylpentane was calculated after data processing; S6: data processing, fitting the light hydrocarbon maturity parameters of the mudstone section with the methane carbon isotope of the mud gas or the vitrinite reflectance of the kerogen, establishing a light hydrocarbon maturity model of the cuttings tank head gas, and estimating the maturity of the natural gas / kerogen around the exploration well.
[0007] Further, in step S1, after each batch of sampling, the sampling tool was wiped with anhydrous ethanol, and after drying, the next sampling was performed to prevent cross contamination.
[0008] Further, in step S1, sampling was performed every 10-20 m in the conventional well section; when the logging data showed oil and gas shows, thin layers or special lithology, the sampling interval was shortened to ≤5 m at a time.
[0009] Further, in step S2, the glass headspace bottle was soaked in 10% nitric acid solution for 24 hours before sampling, then repeatedly washed with deionized water until neutral, and finally dried in a 120℃ oven for 4 hours.
[0010] Further, in step S4, the water bath temperature was 60℃, the heating time was 2 hours, and during the period, the headspace bottle was gently shaken 1-2 times every 30 minutes.
[0011] In summary, the present application has the following beneficial effects relative to the prior art: (1) Continuous detection system construction and data integrity improvement By real-time collection of mud gas and cuttings samples in the drilling, such as cuttings sampling every 10 / 20 m, about 50 to 100 sets of continuous data can be systematically obtained in a 1,000 m well section, which can completely depict the vertical evolution law of kerogen / natural gas maturity. Compared with the traditional discrete sampling mode only in the reservoir section, this scheme can capture more subtle geological changes and effectively avoid missing key information.
[0012] (2) Multi-dimensional anti-interference technology and precision guarantee In view of the oil-based mud pollution problem, a hierarchical pretreatment process is developed, and after the cuttings sample is treated, the light hydrocarbon components of the tank top gas can accurately reflect the formation properties. Through cross verification of the cuttings tank top gas light hydrocarbon maturity parameter and the mud gas carbon isotope (δ¹³C), the reliability of the cuttings tank top gas light hydrocarbon maturity parameter in depicting natural gas maturity is confirmed (Ref. 1), and the analytical limitation of the cuttings tank top gas isotope in the oil-based mud background is revealed (Ref. 2). Figure 1 Figure 2
[0013] (3) Process compatibility and real-time decision support The detection process is seamlessly embedded in the conventional drilling operation, and the period from sample collection to obtaining core parameters such as C4~C8 light hydrocarbon components and carbon isotopes is relatively short, which basically meets the real-time exploration decision-making needs on site. This technology does not need to change the drilling process parameters and is suitable for various oil-based mud systems.
[0014] (4) Efficient use of resources and cost optimization The mud gas and cuttings generated during drilling are directly used as the analysis object, and special downhole sampling tools (such as MDT modules) and supporting operation costs are saved. Compared with the traditional method, the single well detection cost is significantly reduced, and the economic benefit is remarkable, especially in deep-sea deep exploration. BRIEF DESCRIPTION OF DRAWINGS
[0015] The drawings described herein are used to provide a further understanding of the present application, and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings: Figure 1 Correlation analysis of mud gas isotope and cuttings tank top gas light hydrocarbon maturity parameter in the mudstone section of Well B52 in the deep water area of Baiyun Sag, Pearl River Mouth Basin; Figure 2 Correlation analysis of cuttings tank top gas and mud gas methane carbon isotope in Well B52 in the deep water area of Baiyun Sag, Pearl River Mouth Basin; Figure 3 The fitting relationship between light hydrocarbon parameters of cuttings tank top gas and methane carbon isotopes of mud gas in the mudstone section of well B52 in the deep water area of Baiyun Depression, Pearl River Estuary. Figure 4 The flowchart is a method for continuous detection of natural gas maturity based on top gas of drilling cuttings tank provided by the present invention. Detailed Implementation
[0016] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0017] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form may also include the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0018] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.
[0019] See Figures 1 to 4 As shown, this invention provides a method for continuous detection of natural gas maturity based on top gas from drilling cuttings containers, comprising the following steps: (1) Rock cuttings sample processing: A dedicated sampling platform is set up at the outlet of the vibrating screen to ensure that operators can quickly collect fresh rock cuttings. A 30-mesh nylon mesh is used for assisted screening to remove impurity particles larger than 5 mm in diameter, retaining fine-grained rock cuttings to ensure the extraction efficiency of hydrocarbons. Deionized water is used during the rinsing process, and the water pressure is controlled at 0.1-0.2 MPa. The surface of the rock cuttings is slowly rinsed by a mist spray to avoid strong water flow from dispersing fine minerals and causing hydrocarbon loss.
[0020] By combining visual and physical screening, smooth-surfaced fragments (mostly collapsed rock fragments from the wellbore), metal debris (which can be initially separated by magnetic adsorption), and clumps of drilling fluid additives (harder than normal rock cuttings, which can be identified with the aid of a hardness tester) are removed. After each batch of sampling, the sampling tools are wiped with anhydrous ethanol and dried before the next sampling to prevent cross-contamination.
[0021] As a preferred method, sampling intervals in conventional well sections are strictly implemented according to the geological design. For example, in the Baiyun Depression area, sampling is generally carried out once every 10-20m. When logging data shows oil and gas indications (such as abnormally high gas values or decreased drilling fluid density), thin formations (thickness less than 5m), or special lithologies (such as limestone, dolomite, and other carbonate rock formations), the sampling interval needs to be shortened to once every 5m, and parallel sample collection (2-3 duplicate samples per group of samples) should be added to the well section to improve data reliability.
[0022] (2) Sample collection (sampling): After the rock cuttings are transferred from the vibrating screen to the sampling platform, the timing device is started to ensure that the sealed sampling is completed within 30 minutes.
[0023] Take approximately 300g of the cleaned cuttings sample and quickly place it into a 300ml glass capped bottle. Purge the bottle with nitrogen at a flow rate of 2L / min for 30 seconds, ensuring the nitrogen delivery tube is inserted to the bottom of the bottle to fully replace the oxygen and air. After purging, immediately seal the bottle with a screw cap fitted with a PTFE gasket and label it with the depth and sampling time. Calculate the true sampling depth based on the late arrival time: True depth = Current well depth − Cuttings return time × Rate of drilling.
[0024] As a preferred method, the sampling glass headspaces are pretreated before sampling: first, they are soaked in 10% nitric acid solution for 24 hours to remove any organic contaminants that may remain on the bottle walls, then rinsed repeatedly with deionized water until neutral, and finally dried in an oven at 120°C for 4 hours and cooled for later use.
[0025] (3) Sample preservation and transportation: The rock cutting headspace bottle should be placed upright in a portable refrigerator (temperature <4℃) to inhibit microbial degradation; violent shaking should be avoided during transportation, and the sample should be delivered to the laboratory for analysis within 24 hours.
[0026] (4) Water bath heating: Take the headspace bottle of rock cuttings out of the refrigerator, equilibrate to room temperature (about 25°C), and then put it into a constant temperature water bath device for water bath heating; after the heating is completed, take out the headspace bottle and let it cool naturally to room temperature (about 30 minutes).
[0027] As a preferred method, the water bath temperature is 60°C, the heating time is 2 hours, and the headspace bottle is gently shaken 1-2 times every 30 minutes during the heating process to promote the release of hydrocarbon compounds from the rock cuttings into the headspace.
[0028] (5) Testing and analysis: The experimental operation was carried out in accordance with the "Gas Chromatographic Analysis Method of Saturated Hydrocarbons in Petroleum and Sedimentary Organic Matter". The composition of light hydrocarbons was analyzed using a gas chromatograph (GC-FID). The chromatographic column was HP-PONA (50m×0.20mm×0.5μm), and the carrier gas was pure nitrogen (flow rate 1mL / min).
[0029] Heating program: Initial temperature 35℃, hold for 2 minutes (to ensure full vaporization of light hydrocarbon components); linearly increase temperature to 200℃ at a rate of 4℃ / min, and hold at 200℃ for 20 minutes to ensure complete outflow of high carbon number C8 light hydrocarbon components.
[0030] After the heating program is completed, the concentrations of C4-C8 light hydrocarbons are measured, and the isobutane / n-butane ratio is calculated after data processing. i -C4 / n The ratio of light hydrocarbon parameters such as -C4), 2,4-dimethylpentane / 2,3-dimethylpentane (2,4-DMP / 2,3-DMP).
[0031] (6) Data processing: Since the gas analyzed from the sandstone reservoir development section is a migrating gas and cannot reflect the in-situ properties of the formation, the light hydrocarbon maturity parameters of the mudstone section are fitted with the methane carbon isotopes of mud gas or the vitrinite reflectance of kerogen to preliminarily screen reliable maturity parameters. Figure 1 The higher the coefficient of determination of the fitting formula, the better. Generally, since there is a large amount of methane carbon isotope data in drilling mud gas, the fitting effect is better, and methane carbon isotopes in drilling mud gas are generally considered to accurately reflect the properties of underground natural gas. If there is a large amount of kerogen vitrinite reflectance test analysis data in the well, the maturity parameter of light hydrocarbons can also be fitted with vitrinite reflectance to prioritize the application of the more reliable maturity parameter. Through the established maturity assessment model, such as... i -C4 / n The correlation equation between preferred parameters such as -C4, 2,4-DMP / 2,3-DMP and the carbon isotopes of methane in mud gas ( Figure 1 This is used to obtain approximate values for the methane isotopes or kerogen vitrinite reflectance of the natural gas in that formation. (Using cuttings tank top gas...) i -C4 / n -The relationship between C4 and the carbon isotopes of methane in mud gas is taken as an example ( Figure 3 ):
[0032] In the formula: y The methane carbon isotopes in mud gas x Gas for cuttings container top i -C4 / n -C4 ratio.
[0033] Therefore, as long as there is one exploration well in the exploration area with mud gas isotope logging or vitrinite reflectance data, a light hydrocarbon maturity model for the top gas of the cuttings tank can be established, thereby estimating the maturity of natural gas / kerogen around the exploration well. This invention, by optimizing sample processing and analysis procedures, achieves continuous and low-cost detection of natural gas maturity under oil-based mud systems, providing an efficient technical means for deep-sea oil and gas exploration. This method has been verified in practical application at well B52 in the Baiyun Depression of the Pearl River Mouth Basin, meeting the exploration accuracy requirements.
[0034] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for continuous detection of natural gas maturity based on top gas from drilling cuttings containers, characterized in that, Including the following steps: S1, rock cuttings sample processing: Fresh rock cuttings are collected at the outlet of the vibrating screen and screened with a 30-mesh nylon mesh to remove impurity particles larger than 5mm. Then, the surface of the rock cuttings is slowly rinsed with deionized water at a water flow pressure of 0.1-0.2MPa using a mist spray method. During the rinsing process, smooth shards, metal fragments, and drilling fluid additive clumps are removed. S2: Sample collection. Complete sealed sampling within 30 minutes after the rock cuttings are transferred to the platform. Take 300g of the cleaned rock cuttings and quickly put it into a 300ml glass headspace bottle. Purge the air in the bottle with nitrogen at a flow rate of 2L / min for 30 seconds. After purging, immediately seal the bottle with a screw cap with a polytetrafluoroethylene gasket and mark the depth and sampling time. S3: Sample preservation and transportation: Place the rock cutting headspace vial upright in a portable refrigerator and deliver it to the laboratory for sample analysis within 24 hours; S4: Water bath heating. Remove the headspace bottle of rock cuttings from the refrigerator, allow it to reach room temperature, and then place it in a constant temperature water bath for water bath heating. After heating, remove the headspace bottle and allow it to cool naturally to room temperature. S5: Test and analysis: Initial temperature 35℃, hold for 2 minutes; linearly increase temperature to 200℃ at a rate of 4℃ / min, and hold at 200℃ for 20 minutes to ensure complete efflux of high carbon number C8 light hydrocarbon components; after the heating program is completed, measure the concentration of C4~C8 light hydrocarbon compounds, and calculate the light hydrocarbon parameter ratios of isobutane / n-butane and 2,4-dimethylpentane / 2,3-dimethylpentane after data processing; S6: Data processing, fitting the light hydrocarbon maturity parameters of the mudstone section with the methane carbon isotopes of mud gas or the vitrinite reflectance of kerogen, establishing a light hydrocarbon maturity model for the top gas of the cuttings tank, and estimating the maturity of natural gas / kerogen around the exploration well.
2. The method for continuous detection of natural gas maturity based on top gas from drilling cuttings containers according to claim 1, characterized in that, In step S1, after each batch of sampling, the sampling tool is wiped with anhydrous ethanol, dried, and then the next sampling is carried out to prevent cross-contamination.
3. The method for continuous detection of natural gas maturity based on top gas from drilling cuttings containers according to claim 1, characterized in that, In step S1, samples are taken every 10-20m in the conventional well section; when logging data shows oil and gas indications, thin formations, or special lithology, the sampling interval is shortened to ≤5m.
4. The method for continuous detection of natural gas maturity based on top gas from drilling cuttings tanks according to claim 1, characterized in that, In step S2, before sampling, the glass top empty bottle is soaked in 10% nitric acid solution for 24 hours, then rinsed repeatedly with deionized water until neutral, and finally dried in an oven at 120°C for 4 hours.
5. The method for continuous detection of natural gas maturity based on top gas from drilling cuttings containers according to claim 1, characterized in that, In step S4, the water bath temperature is 60°C and the heating time is 2 hours, during which the headspace bottle is gently shaken 1-2 times every 30 minutes.