NMR Relaxation Time Measurement for Rock Wettability

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Solution Overview

Problem

Current methods for determining wettability characteristics of porous media, particularly in oil-bearing reservoirs, are invasive, time-consuming, and limited in their ability to assess changes during oil recovery processes, especially in regions with metal casing or far from the wellbore.

Innovation Solution

A method using NMR spectroscopy to measure relaxation times in fluid samples before, during, and after secondary or tertiary oil recovery processes, allowing for the calculation of a wettability index modification factor to compare different recovery processes and assess changes in wettability within and around wellbores.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional intrusive methods (Amott or USBM indices) are used to determine wettability characteristics, then measurement precision may be adequate, but the process becomes time-consuming and cannot be readily transferred to field conditions

Engineering Contradiction:

Improvewettability measurement precisionVSAvoidtime consumption

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces traditional intrusive mechanical/chemical methods (Amott or USBM indices) with NMR spectroscopy, an electromagnetic field-based technique. This substitution enables non-intrusive measurement of wettability characteristics by analyzing relaxation times of fluids in porous media, dramatically reducing time consumption while maintaining measurement precision and enabling field application.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes changes in NMR relaxation time parameters (T1 and T2) of fluids under different saturation conditions to determine wettability characteristics. By measuring relaxation times at different fluid saturations and comparing them to reference values, the system calculates wettability indices efficiently without time-consuming intrusive procedures.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If NMR logging tools are used to measure wettability in-situ, then non-intrusive measurement and field applicability are achieved, but the tools cannot be used in wellbores lined with metal casing

Engineering Contradiction:

Improvenon-intrusive measurement capabilityVSAvoidapplicability in metal-cased wellbores

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent employs an NMR logging tool that uses electromagnetic fields as an intermediary to measure wettability characteristics through the metal casing. The electromagnetic fields can penetrate the metal casing and interact with the fluids in the porous media, allowing non-intrusive measurement in metal-cased wellbores without direct contact with the formation.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If current NMR methods are used to assess wettability changes, then non-intrusive measurement is possible, but the ability to compare different recovery processes and assess changes during oil recovery is limited

Engineering Contradiction:

Improvenon-intrusive measurementVSAvoidinformation on wettability changes during recovery processes

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

The patent implements a feedback mechanism where NMR relaxation time measurements are continuously taken during secondary and tertiary oil recovery processes. The measured relaxation times are compared to reference values to calculate wettability indices, providing real-time feedback on wettability changes. This enables assessment of how different recovery processes affect wettability characteristics and allows for optimization of recovery operations.

Inventive Principle:

Principle #23Feedback

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 non-invasive, efficient determination of wettability changes and comparison of recovery processes, improving oil recovery efficiency by providing insights into fluid distribution and rock interactions within reservoirs.

Implementation Method 1

nuclear magnetic resonance (NMR) techniques may be used to ascertain information regarding fluids contained within a porous medium

Methodology Applied

Scientific EffectNuclear magnetic resonance (NMR):

Implementation Method 2

measuring a relaxation time for the fluid within the first sample

Methodology Applied

Scientific EffectRelaxation time measurement:

Data Source

PatentUS9575203B2Method for measuring rock wettability

Publication Date: 2017.02.21 BP EXPLORATION OPERATING CO LTD

AI summary

method of comparing a secondary oil recovery process with a tertiary oil recovery process, the secondary oil recovery process and the tertiary oil recovery process being applied to a substantially fluid-saturated porous medium containing an oil phase and an aqueous phase. The method comprising using relaxation time measurements in the calculation of a wettability index modification factor for the oil phase or the aqueous phase, thereby comparing the tertiary oil recovery process with the secondary oil recovery process.