Core Flooding Saturation Correction for Capillary End Effects
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Solution Overview
Problem
Conventional core flooding experiments for determining residual fluid saturation in subsurface formations are affected by capillary end effects, leading to errors in calculating saturation and relative permeabilities due to the discontinuity at the outlet end of the rock core sample, which results in non-representative reservoir data.
Innovation Solution
The methods involve conducting core flooding experiments in steps of increasing injection rate, measuring stabilized average remaining fluid saturation and differential pressure, and applying specific mathematical formulas to correct for capillary end effects, allowing for linear fitting to determine more realistic residual fluid saturations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If core flooding experiments are conducted using conventional methods, then residual fluid saturation can be determined, but capillary end effects cause errors in saturation and relative permeability calculations
Solution Approach 1:
The patent extracts and removes the capillary end effect artifact from the measurement data through mathematical correction. By identifying the specific region near the outlet end where capillary discontinuity occurs and applying correction formulas, the harmful capillary end effect is separated from the valid measurement data, allowing accurate determination of residual fluid saturation representative of the reservoir.
Solution Approach 2:
The patent introduces mathematical correction formulas as an intermediary between the raw measurement data and the final saturation values. These correction formulas act as a mediator that transforms the distorted measurements (affected by capillary end effects) into accurate reservoir-representative saturation values, bridging the gap between laboratory measurements and reservoir conditions.
2Measurement precision
If core sample size is increased to reduce end effects, then measurement accuracy improves, but experimental complexity and cost increase
Solution Approach 1:
The patent changes the parameters used in data analysis rather than physical parameters of the experiment itself. By applying mathematical corrections to the measured pressure drop and saturation data, the patent achieves reservoir-representative results without needing to change core sample size or experimental setup, thus avoiding increased complexity while maintaining measurement precision.
3Measurement precision
If multiple correction methods are applied to determine residual fluid saturation, then accuracy of reservoir evaluation improves, but computational complexity increases
Solution Approach 1:
The patent employs a self-correcting approach where the measurement system inherently accounts for capillary end effects through the proposed correction methodology. The correction formulas are designed to automatically adjust the measured data without requiring complex external interventions or multiple iterative correction steps, simplifying the computational process while maintaining high accuracy.
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
These methods provide reservoir-representative residual fluid saturation values, reducing errors and improving the accuracy of evaluating hydrocarbon reservoir performance and recovery technologies.
Implementation Method 1
Capillary end effects originate from the discontinuity of capillarity at the outlet end of the core sample. The outlet of the core is characterized by a zero capillary pressure which can trap wetting phase in a region near the outlet of the core
Data Source
AI summary
A method for determining residual fluid saturation of a subsurface formation includes acquiring a sample of the subsurface formation, determining a first residual oil saturation during a water flooding process, determining a second residual oil saturation during a gas flooding process, determining a third residual oil saturation during an enhanced oil recovery (EOR) processes, and determining irreducible water saturation during an oil displacing water process.