Rock Core Wettability Analysis via Coreflooding
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Solution Overview
Problem
Conventional methods for determining rock sample wettability and cation exchange capacity are not representative of in-situ reservoir conditions, leading to inaccurate measurements and inefficient enhanced oil recovery (EOR) processes due to overestimation or underestimation of cation exchange sites and failure to identify occupied cations by crude oil.
Innovation Solution
A method involving coreflooding steps to displace native components and determine the amount of indigenous and total exchangeable cations on cation exchange sites, allowing for the calculation of wettability and occupancy by crude oil, using a series of organic solvents and brine injections to maintain reservoir conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rock sample is cleaned to remove any oil in the rock sample, then the cation exchange capacity can be determined by wet chemistry method, but the determined cation exchange capacity is not representative of in-situ reservoir conditions
Solution Approach 1:
The method performs preliminary coreflooding steps to displace native components (crude oil, indigenous exchangeable cations, and formation fluids) from the rock core sample before conducting cation exchange capacity determination. This preliminary displacement action preserves the rock sample in a state that represents in-situ reservoir conditions, allowing accurate determination of both CEC and the amount of crude oil occupying cation exchange sites without the need to clean the sample of oil
2Measurement precision
If the rock sample is ground to fine particles, then the cation exchange sites are exposed for measurement, but excessive grinding increases the cation exchange capacity by exposing more sites than at in-situ conditions
Solution Approach 1:
The method uses partial grinding of the rock core sample rather than excessive grinding to fine particles. This partial grinding action is sufficient to expose cation exchange sites for measurement while maintaining the rock sample structure close to in-situ conditions, thereby avoiding the overestimation of cation exchange capacity that would result from excessive grinding
3Ease of operation
If conventional wettability measurement methods are used, then general rock wettability can be assessed, but the wettability of different cation exchange sites cannot be determined
Solution Approach 1:
The method segments the cation exchange sites based on their crude oil occupancy status, distinguishing between sites occupied by crude oil and sites not occupied by crude oil. By using coreflooding with displaced crude oil and analyzing the distribution of exchangeable cations, the method provides separate wettability measurements for different types of cation exchange sites, thereby preserving site-specific information that would be lost in conventional bulk measurements
4Reliability
If insufficient grinding is performed, then the rock sample structure is preserved, but some reservoir representative cation exchange sites are not exposed
Solution Approach 1:
The method changes the measurement parameters by using coreflooding techniques and analyzing displaced fluids to detect cation exchange sites that are not exposed through traditional grinding methods. This parameter change allows accurate measurement of CEC and crude oil occupancy without requiring extensive grinding, thereby maintaining reservoir representativeness while achieving measurement precision
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 accurate differentiation of cation exchange sites and their wettability, enabling more effective design of EOR operations by quantifying exchangeable cations and oil occupancy, thereby enhancing oil recovery efforts.
Implementation Method 1
subjecting the rock core sample to a plurality of coreflooding steps, the plurality of coreflooding steps displacing the plurality of indigenous exchangeable cations, the crude oil, and the one or more fluids
Implementation Method 2
displacing an excess of cations present in a plurality of interstitial pore spaces of the rock core sample by using a first organic solvent
Implementation Method 3
displacing the plurality of indigenous exchangeable cations from the cation exchange sites of the rock core sample with a first injection fluid
Implementation Method 4
displacing the third organic solvent with the formation brine such that the cations present in the formation brine adsorb onto the cation exchange sites
Implementation Method 5
displacing the third organic solvent with the formation brine such that the cations present in the formation brine adsorb onto the cation exchange sites
Implementation Method 6
determining a wettability of different cation exchange sites of a rock core sample, at a preserved state
Data Source
AI summary
A method for determining properties of different cation exchange sites in a rock core sample, at a preserved state of the rock core sample may include providing a rock core sample that 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, the crude oil, and the one or more fluids in at least three separate coreflooding steps to render the rock core sample clean of native components; determining an amount of indigenous exchangeable cations adsorbed onto the cation exchange sites; subjecting the rock core sample clean of native components to a plurality of coreflooding steps to determine a total amount of exchangeable cations adsorbed onto the cation exchange sites when the rock core sample is clean of native components; and determining at least one property of different cation exchange sites in the rock core sample at the preserved state based on the amount of indigenous exchangeable cations and the total amount of exchangeable cations.