Fluid Substitution for NMR T2 Distribution Accuracy
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Solution Overview
Problem
Nuclear magnetic resonance (NMR) measurements on partially water-saturated rocks provide inaccurate petrophysical parameters due to mud invasion, leading to incorrect grain size distribution and suboptimal hydrocarbon production schemes, resulting in inefficient resource recovery and increased costs.
Innovation Solution
A method and apparatus that correct NMR data by transforming T2 distributions for fully water-saturated rock using a fluid substitution technique, accounting for irreducible and mobile water components, and applying total porosity constraints to derive accurate reservoir rock properties for improved hydrocarbon production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If NMR measurements are performed on partially water-saturated rocks at downhole condition, then the measurements can be obtained in situ without core sampling, but the T2 distribution cannot provide correct grain size distribution and petrophysical parameters become inaccurate
Solution Approach 1:
The patent introduces an intermediary fluid substitution model that acts as a mediator between the measured partially water-saturated T2 distribution and the desired fully water-saturated T2 distribution. The model uses irreducible water saturation as an intermediary parameter to transform the measurement conditions, allowing in situ measurements to yield accurate petrophysical parameters by mathematically substituting the fluid saturation state.
Solution Approach 2:
The patent changes the saturation parameter from partial water saturation to full water saturation through a mathematical transformation. By applying the fluid substitution model that incorporates irreducible water saturation, the T2 distribution parameters are transformed to represent what would be measured under fully saturated conditions, thereby recovering accurate grain size distribution and petrophysical parameters from in situ measurements.
2Measurement precision
If fluid substitution is performed to correct T2 distributions, then accurate petrophysical parameters can be obtained, but the computational complexity and processing time increase
Solution Approach 1:
The patent segments the water saturation into two distinct components: irreducible water saturation and mobile water saturation. This segmentation allows the complex fluid substitution problem to be broken down into manageable parts, where the irreducible water portion is treated separately from the mobile water portion, simplifying the mathematical transformation while maintaining accuracy in the corrected T2 distribution.
Solution Approach 2:
The patent applies partial action by focusing the fluid substitution transformation only on the mobile water component of the T2 distribution, while keeping the irreducible water component unchanged. This selective approach reduces computational complexity compared to transforming the entire T2 distribution, as only the portion affected by mud invasion requires correction.
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
The method enhances the accuracy of petrophysical parameters, enabling more precise reservoir modeling and optimization of hydrocarbon production, reducing uncertainties and costs associated with suboptimal field development.
Implementation Method 1
Nuclear magnetic resonance (NMR) measurements of reservoir rocks can provide petrophysical parameters of oil or gas bearing formations
Data Source
AI summary
A method for transforming an earth formation and/or production equipment based on correcting nuclear magnetic resonance (NMR) data to account for partially water-saturated rock includes: receiving NMR logging data having echo-trains for an earth formation; inverting the echo-trains to provide transverse relaxation time constant (T2) distributions for various components of fluid in the earth formation; substituting a T2 distribution for mobile water of fully water-saturated rock for a T2 distribution for mobile water of partially water-saturated rock based on values of the mobile water T2 distribution of partially water-saturated rock and a total porosity constraint; summing the T2 distribution for mobile water of fully water-saturated rock and a T2 distribution for an immobile water component of the fluid to provide a T2, distribution for fully water-saturated rock; and transforming the earth formation and/or the production equipment based on a parameter derived from the T2 distribution for fully water-saturated rock.