Rock Wettability Determination via Dimensionless Imbibition
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Solution Overview
Problem
Current methods for measuring rock wettability in oilfield applications are inadequate, as they fail to accurately assess intermediate and mixed-wetting conditions, and do not account for variations in core properties and sample geometry, leading to incomplete understanding of oil production rates and recovery efficiency.
Innovation Solution
A method involving spontaneous imbibition experiments with dimensionless time correlations to adjust oil recovery curves, allowing for comparison of rock samples and determination of wettability indices, which categorize rocks as more water-wet, mixed-wet, or oil-wet based on imbibition rates and saturation conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional wettability measurement methods (Amott-Harvey, USBM) are used, then wettability can be determined, but they fail to account for variations in core properties and sample geometry, leading to incomplete understanding of oil production rates
Solution Approach 1:
The patent introduces dimensionless time as a new parameter to normalize imbibition data across different core properties and geometries. By transforming the imbibition time using dimensionless groups that incorporate core permeability, porosity, and geometry factors, the method enables accurate wettability comparison while accounting for variations in core properties and sample dimensions.
2Ease of manufacture
If binary wettability classification (water-wet or oil-wet) is used, then simplification is achieved, but intermediate and mixed-wetting conditions are masked
Solution Approach 1:
The patent segments the continuous wettability spectrum into distinct categories (strongly water-wet, intermediate water-wet, mixed-wet, intermediate oil-wet, strongly oil-wet) based on the slope of the dimensionless oil recovery curve. This segmentation preserves information about intermediate conditions while providing a structured classification system that is more informative than binary classification.
3Quantity of substance
If spontaneous imbibition experiments are performed without dimensionless time correlation, then oil recovery data can be obtained, but variations in sample size and geometry prevent accurate comparison between different rock samples
Solution Approach 1:
The patent creates equipotential conditions for comparison by normalizing all imbibition data to a common dimensionless time scale. This transformation eliminates the effects of varying sample sizes and geometries, allowing accurate comparison of wettability characteristics across different rock samples regardless of their physical dimensions.
4Quantity of substance
If traditional imbibition methods are used, then oil recovery measurement is achieved, but prediction of oil production rates and recovery efficiency is incomplete
Solution Approach 1:
The patent establishes a feedback relationship between the dimensionless imbibition slope (which characterizes wettability) and oil production rates. By correlating the normalized imbibition behavior with production performance, the method enables prediction of oil production rates and recovery efficiency based on wettability characteristics, providing actionable insights for reservoir management.
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 a more accurate assessment of rock wettability, enabling better prediction of oil production rates and recovery efficiency by accounting for variations in rock properties and sample geometry, and distinguishing between water-wet, mixed-wet, and oil-wet conditions.
Implementation Method 1
A spontaneous imbibition experiment provides the amount of oil recovered over time due to naturally occurring capillary forces
Implementation Method 2
Wettability describes the preference of a solid to be in contact with one fluid over another based on the balance of surface and interfacial forces
Data Source
AI summary
A new method of assessing wettability of a reservoir rock is provided, using a mineral oil/alkane saturated sample first, a crude oil and water saturated sample equivalent to natural reservoir rock second, and a third crude oil saturated, water free sample, measuring different wettability states and comparing the slopes of all three adjusted values to determine a wettability state for the reservoir rock.