NMR Well Log Capillary Pressure Curves
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Solution Overview
Problem
Current methods for determining capillary pressure in subsurface rock formations are expensive, time-consuming, and environmentally unfriendly, often resulting in sparse data points and gross errors in reservoir simulation due to the need for physical rock samples and complex calibration processes.
Innovation Solution
A computer-implemented method using nuclear magnetic resonance (NMR) well log data and water saturation well log data to determine initial capillary pressure and calibrate it, allowing for the generation of continuous capillary pressure curves without the need for physical rock samples, through Thomeer hyperbola modeling and optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mercury injection capillary pressure experiments are used, then capillary pressure data can be obtained, but the process is expensive, time-consuming, and environmentally harmful
Solution Approach 1:
The patent replaces the mechanical mercury injection system with a nuclear magnetic resonance (NMR) based measurement system. Instead of physically injecting mercury into rock cores to measure capillary pressure, the invention uses NMR logging tools to measure hydrogen distribution in the subsurface formation, which can be converted to capillary pressure curves through the established relationship between NMR relaxation times and pore size distribution. This substitution eliminates environmental harm while providing continuous capillary pressure data.
Solution Approach 2:
The patent creates a virtual copy of the capillary pressure measurement process by using NMR measurements to infer capillary pressure characteristics without physical rock sampling. The NMR log data provides a continuous profile that copies the essential information of traditional discrete MICP measurements, allowing engineers to populate reservoir models with accurate capillary pressure curves without conducting expensive and harmful laboratory experiments on every formation.
2Measurement precision
If physical rock samples are required for capillary pressure measurement, then accurate data can be obtained, but data availability is limited and costs increase
Solution Approach 1:
The patent replaces physical rock sampling and laboratory analysis with in-situ NMR logging measurements. The NMR tool measures hydrogen distribution directly in the subsurface formation, eliminating the need to extract, transport, and analyze physical rock cores. This substitution dramatically increases data availability from sparse discrete points to continuous profiles while reducing costs and preserving formation integrity.
Solution Approach 2:
The patent leverages the multi-functionality of NMR logging tools that can simultaneously measure porosity, permeability, fluid saturation, and capillary pressure characteristics from the same pass through the formation. This universal measurement capability eliminates the need for separate physical sampling campaigns and provides comprehensive reservoir characterization data in a single operation.
3Ease of manufacture
If NMR wireline response is used to obtain capillary pressure curves, then data can be obtained without physical samples, but the presence of hydrocarbon effects and calibration complexities reduce reliability
Solution Approach 1:
The patent applies preliminary calibration of the NMR-based capillary pressure method using available formation data before full deployment. By establishing calibration relationships between NMR measurements and expected capillary pressure behavior based on formation lithology and fluid properties, the method accounts for hydrocarbon effects and other complexities in advance, improving reliability while maintaining the advantages of non-invasive measurement.
Solution Approach 2:
The patent incorporates feedback mechanisms where NMR measurements are continuously refined by comparing with reservoir simulation results and adjusting calibration parameters. This iterative feedback process accounts for hydrocarbon effects and improves the accuracy of capillary pressure curves over time, transforming the initial reliability issue into a strength through continuous optimization.
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 approach provides accurate and cost-effective capillary pressure measurements, reducing errors and increasing data availability, while being environmentally friendly by eliminating the need for mercury injection capillary pressure experiments.
Implementation Method 1
nuclear magnetic resonance well log data from measurements obtained from the formation by a nuclear magnetic resonance log
Data Source
AI summary
Continuous capillary pressure (Pc) curves of subsurface rock formations adjacent wells are determined based on translation relaxation time (T2) data from nuclear magnetic resonance (NMR) and from wireline well logs, such as resistivity logs, to obtain water saturation (Sw) of the rock in the formations. The T2 data and the hydrocarbon density, water density, free water level, and paleo-water level of the formation are processed to obtain parameters of Thomeer hyperbolas that closely conform to water saturation values obtained from the other well logs. The Thomeer hyperbolas so determined are converted to capillary pressure curves.