Time-Dependent NMR Logging for Gas Production Rate Prediction
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Solution Overview
Problem
Current NMR logging measurements do not effectively incorporate time-dependent saturation and de-saturation phenomena to estimate free gas storage and production rates in geologic reservoirs, limiting the accuracy of potential gas production rates.
Innovation Solution
A system and method utilizing time-dependent NMR measurements, where gas is injected into a sample under pressure, and NMR signals are monitored as the gas migrates into and out of the sample, allowing for the estimation of fluid production rates by analyzing T2 distributions and mass changes, applicable to both laboratory and downhole applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional NMR logging measurements are used, then free gas storage can be estimated, but time-dependent saturation and de-saturation phenomena are not incorporated, limiting production rate accuracy
Solution Approach 1:
The patent applies dynamics by transitioning from static NMR measurements to time-dependent dynamic measurements. The system performs repeated NMR measurements during fluid injection and production cycles, capturing the dynamic saturation and de-saturation processes. This allows characterization of fluid movement over time, enabling accurate production rate predictions by incorporating temporal variations in pore fluid content.
2Measurement precision
If time-dependent NMR measurements are implemented, then production rate prediction accuracy improves, but measurement complexity and data processing requirements increase
Solution Approach 1:
The patent applies preliminary action by conducting fluid injection and pressure cycling operations before final production rate prediction. The system first saturates the formation with fluid under controlled pressure, then removes pressure to create de-saturation conditions. These preliminary steps establish the time-dependent NMR signal variations needed for accurate production rate prediction, separating the complex measurement process into manageable sequential phases.
Solution Approach 2:
The system uses feedback by continuously monitoring NMR signals during injection and production cycles, using this information to update and refine production rate predictions. The time-dependent NMR measurements provide real-time feedback on fluid saturation changes, which are incorporated into the prediction algorithm to improve accuracy while managing data complexity through iterative refinement.
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 precise prediction of fluid production rates from geologic reservoirs by distinguishing contributions from different pore systems and fluids, providing detailed production profiles and porosity information, aiding in production planning and infrastructure decisions.
Implementation Method 1
Time-dependent nuclear magnetic resonance (NMR) has been used to monitor chemical reactions
Implementation Method 2
On a pump-up cycle, after removing borehole fluids, a fluid is injected into a region of investigation
Data Source
AI summary
A tool having a pump-out unit, pumping unit, and NMR unit is disposed in a wellbore. On a pump-up cycle, after removing borehole fluids, a fluid is injected into a region of investigation. NMR measurements are made while fluid migrates into the region of investigation. On a production cycle, pressure is removed, allowing fluid to exit the formation while NMR measurements are made. A rate of fluid production is estimated using the time-dependent NMR measurements. Alternatively, the mass of a sample is measured. Fluid is injected into the sample and the mass of the injected sample is measured. Pressure is removed and the mass of the injected sample as the fluid migrates out of the sample is measured. The change in mass of the injected sample as the fluid migrates out of the sample is determined and a rate of fluid production is estimated using the determined change in mass.