Fine-Grained Sedimentary Rock Classification via Micro-Drilling and XRD
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Solution Overview
Problem
Current methods for classifying fine-grained mixed sedimentary rocks are inadequate due to subjective mineral content estimation, inability to accurately distinguish types, and failure to characterize mixed sedimentation phenomena, leading to errors in identifying high-quality rock types essential for shale oil and gas exploration.
Innovation Solution
A classification method that uses systematic sampling with micro-drilling to avoid diagenetic minerals, combines macroscopic and microscopic analysis, and employs X-ray diffraction and high-precision carbon-sulfur analysis to determine mineral and TOC content, subdividing sedimentary structures and incorporating TOC values into rock type naming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thin section observation is used to count mineral content, then local mineral composition can be observed, but the mineral content of the entire sample cannot be accurately characterized and subjectivity increases
Solution Approach 1:
The core is divided into multiple segments along its length, with systematic sampling at defined intervals. Each segment is separately processed through thin section observation and X-ray diffraction analysis, allowing the mineral content to be characterized at multiple locations throughout the core rather than just at a single point, thereby improving overall measurement precision.
Solution Approach 2:
The manual, subjective process of thin section observation is supplemented and replaced by automated X-ray diffraction analysis. This substitution of mechanical/manual measurement with instrumental analysis provides objective, quantitative mineral content data that is not dependent on observer subjectivity, while the automated nature of the process reduces operational complexity.
2Ease of operation
If geological hammer sampling is used, then field collection is simple, but strong heterogeneity cannot be distinguished and large errors occur in determining location and thickness
Solution Approach 1:
The core is segmented into multiple sampling intervals along its length, with each interval representing a specific segment of the core. Systematic sampling at these intervals allows precise determination of the location and thickness of different rock types, overcoming the limitation of single-point hammer sampling while maintaining field operational simplicity.
Solution Approach 2:
The core serves as an intermediary that preserves the original sedimentary structures and heterogeneity. By systematically sampling along the core length and using X-ray diffraction analysis as an intermediary measurement technique, the method accurately identifies rock types and their distributions without the distortion introduced by manual hammer sampling, thereby improving identification accuracy while keeping field operations simple.
3Quantity of substance
If diagenetic minerals are present in samples, then mineral content is increased, but identification of fine-grained mixed sedimentary rock types becomes erroneous
Solution Approach 1:
The method extracts and removes diagenetic minerals from the analysis through careful sample selection and X-ray diffraction pattern interpretation. By taking out these secondary minerals from the mineral content calculation, the method maintains accurate rock type identification while still accounting for the complete mineralogy of the sample, thereby improving identification reliability without losing mineral content information.
Solution Approach 2:
X-ray diffraction analysis provides feedback about the mineral composition and identifies diagenetic minerals present in the sample. This feedback information is then used to adjust the mineral content calculations and rock type identification, ensuring that diagenetic minerals are properly accounted for or excluded, thereby maintaining high reliability in rock type identification while preserving accurate mineral content quantification.
4Ease of operation
If 'laminated' is used to describe sedimentary structure, then general structure is characterized, but mixed sedimentation phenomenon of different lamina cannot be effectively characterized
Solution Approach 1:
The sedimentary structure is segmented into different laminae types (carbonate laminae, clay laminae, silt laminae) and their combinations. By systematically identifying and describing each lamina type and their vertical arrangements, the method provides detailed characterization of mixed sedimentation phenomena while maintaining the simplicity of the laminated structure description, thereby preventing loss of information about different sedimentation processes.
Solution Approach 2:
The method adds a dimensional aspect by describing not only the presence of laminated structures but also the specific composition and arrangement of different laminae types. This dimensional expansion from simple 'laminated' to detailed 'laminated carbonate-clay couplets, laminated carbonate-silt couplets, etc.' allows effective characterization of mixed sedimentation phenomena while keeping the description approachable and systematic.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides accurate and comprehensive classification of fine-grained mixed sedimentary rocks, effectively identifying high-quality types and guiding the identification of sweet spots for shale oil and gas development, reducing exploration costs and improving efficiency.
Implementation Method 1
Each powder sample are performed a mineral content analysis by X-ray diffraction to obtain the contents of different types of minerals in the samples.
Implementation Method 2
Each powder sample are performed a total organic carbon (TOC) content analysis to obtain the TOC contents in the samples.
Data Source
AI summary
The present disclosure discloses a classification method and system for fine-grained mixed sedimentary rocks, a medium and a terminal. Core description and thin section observation are used to accurately identify the sedimentary structure types and their vertical distribution characteristics from the macroscopic and microscopic perspectives, and indicates the mixed sedimentation characteristics of combination of different lamina or laminar couplets. The micro-drilling sampling technique is used to sample the samples with different types of sedimentary structures while avoiding diagenetic minerals. X-ray diffraction mineral content analysis and a high-precision carbon-sulfur analyzer are used to obtain the contents of different types of minerals and the total organic carbon contents in each sample, respectively, the basic rock type of each sample was determined using a triangular classification diagram. The name of sedimentary structure and the total organic carbon content are added in order before the name of the basic rock type.