Shale Oil Soaking Time Determination via NMR and Resistivity
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Solution Overview
Problem
Current methods for determining the soaking time of shale oil/gas wells after hydraulic fracturing are not accurate or reliable, leading to inefficiencies in fluid backflow and production rates due to the dense and low-porosity nature of shale reservoirs.
Innovation Solution
A method using a device comprising an online NMR tester, resistivity tester, and other components to simulate reservoir conditions, measure core sample resistivity and nuclear magnetic signals, and calculate a reasonable soaking time based on pressure attenuation and fluid injection volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If well soaking is performed for a longer period to enhance fluid transmission capacity, then initial production increases, but time loss and operational efficiency deteriorate
Solution Approach 1:
The patent replaces traditional mechanical timing methods with nuclear magnetic resonance (NMR) technology to determine soaking time. The NMR method measures fluid distribution and saturation in real-time, providing an objective scientific basis for determining the optimal soaking time point, thus eliminating arbitrary or extended soaking periods while ensuring maximum initial production.
Solution Approach 2:
The patent implements a feedback mechanism where NMR measurements during soaking provide real-time data on fluid saturation and distribution. This feedback allows dynamic adjustment and precise determination of when the soaking process has achieved optimal results, preventing both insufficient and excessive soaking durations.
2Measurement precision
If traditional methods are used to determine soaking time without precise measurement, then device complexity is reduced, but measurement precision and reliability deteriorate
Solution Approach 1:
The patent introduces an intermediary NMR measurement system that acts as a mediator between the complex reservoir environment and the simple decision-making process. The NMR device translates complex subsurface fluid dynamics into clear, quantifiable metrics (T2 spectra, saturation levels) that directly indicate optimal soaking time, bridging the gap between complexity and simplicity.
Solution Approach 2:
The patent creates a simplified representative model of the reservoir conditions through NMR measurements on core samples and well data. This 'copy' of the reservoir's fluid behavior allows accurate soaking time determination without directly observing the complex actual reservoir, enabling precise measurement with manageable device complexity.
3Reliability
If extensive testing and experimentation are conducted to determine optimal soaking time, then reliability of the method improves, but loss of time and operational complexity increase
Solution Approach 1:
The patent performs preliminary NMR measurements and core sample testing before actual well soaking to establish baseline parameters and validation protocols. This preliminary action creates a validated framework that ensures reliability during the actual soaking operation, preventing the need for extensive testing during production and reducing overall time loss.
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 allows for the determination of an optimal soaking time that enhances fluid transmission capacity and production rates by accurately simulating reservoir conditions and evaluating core permeability.
Implementation Method 1
continuously monitoring methane nuclear magnetic signals of the plurality of first core samples and the plurality of second core samples using the online NMR tester
Implementation Method 2
activating the resistivity tester to measure a resistivity change curve of each of the plurality of first core samples
Implementation Method 3
vacuumizing the core gripper using the vacuum pump to simulate the state of each of the first core samples in the reservoir
Implementation Method 4
activating the confining pressure pump, and applying a core confining pressure to each of the plurality of first core samples in the core gripper
Data Source
AI summary
Disclosed is a method for determining a reasonable soaking time of a shale oil/gas well, implementing testing and experimentation using a device for testing a reasonable soaking time of a shale oil/gas well. The method includes: selecting a core sample; measuring and obtaining a porosity of the core sample; simulating a state of a first core sample in a reservoir; injecting methane to reach a pore pressure of the reservoir; injecting a simulated fracturing fluid into a core gripper; measuring a resistivity change curve of the first core sample; measuring and obtaining a half-life period of pressure attenuation of a first pressure sensor until an inflection point appears in the resistivity change curve of the first core sample; obtaining an experimental duration during which the first core sample and a second core sample present the shortest half-life period of pressure attenuation; obtaining a time point at which core NMR signals of the first core sample and the second core sample have the largest change amplitude; obtaining soaking time at a core scale after sorting; and obtaining the soaking time of the shale oil/gas well.