Cation Exchange Site Determination in Rock Core Samples
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Solution Overview
Problem
Conventional methods for determining cation exchange capacity in rock samples are not representative of in-situ reservoir conditions, as they either overestimate or underestimate the capacity due to sample preparation and fail to identify reservoir-specific exchangeable cations, impacting enhanced oil recovery efforts.
Innovation Solution
A method involving coreflooding steps to displace indigenous exchangeable cations and fluids from rock core samples, using organic solvents and formation brine to replicate reservoir conditions, allowing for the differentiation and quantification of cation exchange sites such as Na+, K+, and Ca2+, enabling more accurate analysis of cation exchange sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the rock sample is cleaned to remove oil and ground to fine particles using conventional wet chemistry methods, then the sample preparation is simplified and cation exchange capacity can be determined, but the determined capacity becomes unrepresentative of in-situ reservoir conditions due to exposure of additional cation exchange sites and loss of indigenous cations
Solution Approach 1:
The method performs preliminary coreflooding operations to displace indigenous cations and restore the rock sample to reservoir conditions before analysis. This preliminary action ensures that the cation exchange sites are in their native state with indigenous cations present, making the subsequent CEC determination representative of actual reservoir conditions rather than laboratory-prepared states
Solution Approach 2:
The method changes the physical state and composition parameters of the rock sample by performing coreflooding with formation brine and organic solvents to displace indigenous cations and restore reservoir conditions. This parameter change ensures that the sample maintains its in-situ characteristics during CEC determination, avoiding the artifacts introduced by conventional grinding and cleaning procedures
2Ease of operation
If conventional wet chemistry methods are used to determine cation exchange capacity, then the procedure is straightforward, but the method cannot identify reservoir-specific exchangeable cations or determine which cation exchange sites are occupied by crude oil
Solution Approach 1:
The method segments the cation exchange sites into different categories based on their occupancy status (occupied by crude oil versus occupied by indigenous cations) through sequential coreflooding steps. This segmentation allows for separate determination and identification of different cation types and their specific locations on exchange sites, preserving reservoir-specific information that would be lost in bulk analysis
Solution Approach 2:
The method uses formation brine and organic solvents as intermediary substances during coreflooding to selectively displace and identify different cation types. These intermediaries enable the differentiation and identification of reservoir-specific exchangeable cations without directly analyzing the complex crude oil-rock system, thus preserving detailed cation information while maintaining operational feasibility
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 method provides a more accurate determination of cation exchange sites, enhancing the design of enhanced oil recovery operations by considering reservoir-specific exchangeable cations, leading to improved efficacy in EOR processes.
Implementation Method 1
subjecting the rock core sample to a plurality of coreflooding steps, the plurality of coreflooding step displacing the plurality of indigenous exchangeable cations and the one or more fluids
Implementation Method 2
using organic solvents and formation brine to replicate reservoir conditions, allowing for the differentiation and quantification of cation exchange sites
Implementation Method 3
determining an amount of indigenous exchangeable cations adsorbed onto the cation exchange sites
Data Source
AI summary
A method for determining properties of different cation exchange sites in a rock core sample may include providing a rock core sample that is in either a preserved state or a non-preserved state, wherein a preserved form of the rock core sample includes a plurality of indigenous exchangeable cations adsorbed onto the cation exchange sites, a plurality of cation exchange sites occupied by a crude oil, and one or more fluids occupying pore spaces in the rock core sample; subjecting the rock core sample to a plurality of coreflooding steps, the plurality of coreflooding step displacing the plurality of indigenous exchangeable cations and the one or more fluids in at least two separate coreflooding steps to render the rock core sample clean of indigenous exchangeable cations; and determining an amount of indigenous exchangeable cations adsorbed onto the cation exchange sites.