Reservoir Rock API Gravity via CO2 Emission
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Solution Overview
Problem
Conventional methods for determining API gravity of crude oil require grinding samples into powder, leading to sample loss and inaccuracy due to smearing and evaporation, and are time-consuming.
Innovation Solution
A method involving oxidative testing where a reservoir sample is heated at a fixed rate to detect the peak carbon dioxide emission temperature, using an empirical correlation to determine API gravity without grinding the sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If samples are ground into powder for pyrolysis analysis, then the analysis can be performed, but sample loss and inaccuracy occur due to smearing and evaporation
Solution Approach 1:
The patent extracts only the necessary information (API gravity) directly from intact core samples or produced fluids without requiring physical disruption. The oxidation method measures CO2 evolution from unground samples, eliminating the grinding step that causes sample loss while still obtaining the required measurement parameter.
Solution Approach 2:
The patent uses CO2 evolution as an intermediary measurement parameter that correlates to API gravity. Instead of directly measuring physical properties of ground samples, the method uses the oxidation reaction and CO2 release pattern as a mediator to infer API gravity from intact samples, avoiding the need for sample disruption.
2Measurement precision
If samples are ground into powder for pyrolysis analysis, then the analysis can be performed, but inaccuracy occurs due to smearing and evaporation
Solution Approach 1:
The patent extracts the essential measurement information directly from intact samples without the intermediate grinding step. By measuring CO2 evolution from unground core samples or produced fluids, the method eliminates processing errors introduced by sample preparation while maintaining measurement capability.
Solution Approach 2:
The oxidation method allows samples to undergo natural oxidation reactions without mechanical disruption. The sample's inherent chemical properties are measured directly through CO2 evolution patterns, eliminating the need for external sample preparation processes that introduce errors.
3Measurement precision
If conventional pyrolysis methods are used, then API gravity can be determined, but the process is time consuming and requires large sample amounts
Solution Approach 1:
The oxidation method uses partial oxidation at controlled temperatures to generate measurable CO2 evolution patterns. By performing oxidation at multiple temperature stages (e.g., 400°C, 500°C, 600°C) rather than complete combustion, the method achieves sufficient measurement signal with shorter processing time and smaller sample amounts.
Solution Approach 2:
The patent changes the measurement parameter from direct pyrolysis product analysis to CO2 evolution rate measurement during oxidation. This parameter change enables faster analysis with smaller samples because CO2 detection is more sensitive and the oxidation process can be completed more quickly than full pyrolysis while still providing API gravity information.
4Measurement precision
If samples are ground into powder, then analysis can proceed, but equipment complexity and operational difficulty increase
Solution Approach 1:
The patent removes the sample preparation step entirely from the analysis process. By using intact samples or produced fluids directly in the oxidation apparatus, the method eliminates grinding equipment and associated operational complexity while maintaining the ability to determine API gravity.
Solution Approach 2:
The method uses CO2 evolution as an intermediary that can be measured directly from intact samples. This eliminates the need for mechanical sample preparation equipment and procedures, simplifying both the device and operational workflow while preserving measurement 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
This method provides accurate and precise API gravity determination with minimal sample processing, reducing errors and time consumption, and is suitable for well planning and oil recovery strategies.
Implementation Method 1
heating the sample to a first temperature using an oxidative testing apparatus. The sample is then heated to a second temperature over a period using a fixed heating rate using the oxidative testing apparatus
Implementation Method 2
Pyrolysis approaches in which flame ionization detection is used to determine API gravity have also been demonstrated
Implementation Method 3
Pyrolysis approaches in which flame ionization detection is used to determine API gravity have also been demonstrated
Data Source
AI summary
A method of determining an API gravity of a crude oil is provided. The method includes obtaining a reservoir sample containing the crude oil and heating the sample to a first temperature using an oxidative testing apparatus. The sample is then heated to a second temperature, which is greater than the first temperature, over a period using a fixed heating rate. The rate of carbon dioxide emission from the sample is detected during the period of heating to the second temperature. The peak rate of carbon dioxide emission from the sample is then determined and the peak carbon dioxide emission temperature associated with the peak rate of carbon dioxide emission is also determined. The API gravity of the crude oil in the reservoir sample is determined using an empirical correlation between API gravity and the peak carbon dioxide emission temperature associated with the fixed heating rate.