NMR Characterization of Deeply Buried Carbonate Rock Pore Structure
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Solution Overview
Problem
Traditional methods fail to accurately characterize the rock physical characteristics of deeply buried carbonate reservoirs due to their complex pore structure and heterogeneity, making it difficult to evaluate their developmental characteristics effectively.
Innovation Solution
A method involving sampling, core extraction, thin section analysis, normal pressure nuclear magnetic resonance testing, and establishing relations to characterize porosity, permeability, and pore structure, which includes determining sampling positions, extracting core plunger samples, making rock thin sections, identifying rock types, performing rock physical characteristic tests, and using nuclear magnetic resonance to establish correlations for accurate characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional methods (thin section observation, SEM, CT scanning) are used to characterize rock physical characteristics, then qualitative or semi-quantitative analysis can be obtained, but the complex pore structure and heterogeneity of deeply buried carbonate rocks cannot be accurately characterized
Solution Approach 1:
The patent replaces traditional mechanical and optical testing methods (thin section observation, SEM, CT scanning) with nuclear magnetic resonance (NMR) technology. NMR uses magnetic fields and radiofrequency pulses to characterize pore structure, porosity, and permeability without mechanical contact or complex sample preparation, achieving accurate characterization of deeply buried carbonate rocks while simplifying the testing process.
Solution Approach 2:
The patent utilizes different NMR relaxation time parameters (T1 and T2) to characterize different aspects of pore structure. By analyzing the distribution and characteristics of these relaxation times, the method can distinguish between different pore types and sizes, accurately capturing the complex pore structure of carbonate rocks without requiring multiple different testing methods.
2Reliability
If core samples from deeply buried carbonate reservoirs are analyzed using conventional methods, then some rock properties can be measured, but the heterogeneous and complex pore structure leads to inaccurate characterization
Solution Approach 1:
The patent replaces difficult-to-interpret visual and microscopic methods with NMR technology that directly measures pore characteristics through relaxation time signals. This substitution makes it easier to detect and quantify pore structure heterogeneity, providing reliable reservoir evaluation data from core samples of deeply buried carbonate rocks.
Solution Approach 2:
The patent uses nuclear magnetic resonance signals as an intermediary to indirectly characterize pore structure properties. Instead of directly observing complex pore geometries, the method measures NMR relaxation times that reflect pore size, connectivity, and fluid characteristics, converting difficult-to-measure structural properties into easily interpretable signal parameters.
3Productivity
If multiple traditional testing methods are employed to characterize rock properties, then comprehensive data can be obtained, but the process is time-consuming and destructive
Solution Approach 1:
The patent merges multiple characterization functions (porosity measurement, pore size distribution, permeability estimation) into a single NMR testing procedure. This consolidation eliminates the need for sequential thin section preparation, SEM imaging, and CT scanning, dramatically reducing testing time while providing comprehensive pore structure data in one non-destructive measurement.
Solution Approach 2:
The NMR method provides self-contained characterization capability, requiring minimal sample preparation and no destructive processing. The core sample remains intact throughout testing, allowing repeated measurements and eliminating time-consuming sample preparation steps associated with traditional methods, thereby improving overall testing efficiency.
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
Enables the massive, quick, non-destructive, and accurate characterization of rock physical characteristics under both normal and overburden pressures, providing technical support for oilfield evaluations of rock types.
Implementation Method 1
performing a normal pressure nuclear magnetic resonance test and rock physical characteristic tests for measuring rock physical characteristics on the core plunger sample
Data Source
AI summary
The invention relates to the technical field of oilfield exploration and development, and particularly relates to a method for characterizing the rock physical characteristics of deeply buried carbonate rocks, comprising the following steps: determining a rock type of a rock thin section by identifying the surface structure characteristics of the rock thin section corresponding to a core plunger sample; performing a normal pressure nuclear magnetic resonance test and rock physical characteristic tests on the core plunger sample; establishing an identification plate, a first relation, a second relation and a third relation; characterizing the rock physical characteristics of a target rock sample under normal pressure and its buried depth according to the normal pressure nuclear magnetic resonance test result and the overburden pressure nuclear magnetic resonance test result of the target rock sample respectively.