Volume of Organic Matter Method for Tar Quantification
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Solution Overview
Problem
Current methods for assessing hydrocarbon saturation in oil reservoirs, such as the Archie Equation and NMR logging tools, are inadequate for accurately quantifying the volumes of immovable hydrocarbons like tar and pyrobitumen, which significantly impact reservoir performance, due to their inability to distinguish between oil, tar, and pyrobitumen and reliance on indirect measurements.
Innovation Solution
The Volume of Organic Matter (VOM) method, which involves direct measurement of hydrocarbons using pyrolysis and compositional modeling to determine the volume of tar and pyrobitumen in reservoir rock, providing quantitative data in meaningful units for reservoir characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Archie Equation is used to assess hydrocarbon saturation, then reservoir parameters can be calculated, but the calculation is compromised when tar is present due to sensitivity to wettability changes and inability to discriminate between oil, tar, and pyrobitumen
Solution Approach 1:
The patent segments the hydrocarbon assessment into distinct components: movable hydrocarbons (oil), immovable hydrocarbons (tar and pyrobitumen), and uses separate analytical methods for each. The compositional modeling divides the organic matter into end-members (oil, tar, pyrobitumen, kerogen) and calculates each component's contribution separately, allowing accurate saturation calculations even when tar is present.
Solution Approach 2:
The patent introduces compositional modeling as an intermediary tool that bridges the gap between raw pyrolysis data and reservoir characterization. This modeling framework uses conversion factors and end-member compositions to translate pyrolysis yields into meaningful volumetric percentages of different hydrocarbon types, enabling accurate assessment despite the presence of tar.
2Quantity of substance
If NMR logging tools are used to assess oil reservoir fluid properties, then information about fluid nature can be obtained, but explicit calculation of component volumes is not possible and reliance on indirect measurements and assumptions is required
Solution Approach 1:
The patent replaces the indirect NMR measurement approach with a direct pyrolysis-based analytical system. Instead of using magnetic resonance to infer fluid properties, the method uses thermal decomposition (pyrolysis) to directly release and quantify hydrocarbon components, substituting a chemical-physical process for a physical measurement technique.
Solution Approach 2:
The patent changes the measurement parameters from NMR signal intensity (which requires interpretation) to pyrolysis hydrocarbon yield (which provides direct compositional data). By measuring the actual hydrocarbon content through pyrolysis and using conversion factors, the method obtains explicit volumetric percentages of oil, tar, and pyrobitumen without relying on indirect assumptions.
3Reliability
If residual hydrocarbon staining is analyzed to assess movable hydrocarbons, then characteristics are preserved and understood, but only a fraction of total hydrocarbons is represented due to losses during drilling and volatilization
Solution Approach 1:
The patent extracts and quantifies both movable and immovable hydrocarbons through pyrolysis, separating them into distinct components. By using compositional modeling to account for all hydrocarbon types (oil, tar, pyrobitumen) and applying appropriate conversion factors, the method recovers the full hydrocarbon budget rather than relying solely on residual staining that represents only a fraction.
Solution Approach 2:
The patent performs preliminary pyrolysis treatment on the rock sample to release all bound hydrocarbons before analysis. This preliminary thermal decomposition step ensures that both movable and immovable hydrocarbons are liberated and can be quantified, preventing the losses that occur during subsequent handling and analysis.
4Object-generated harmful factors
If tar and pyrobitumen are present in significant quantities, then fluid mobility is reduced, but current methods cannot accurately quantify their volumes relative to reservoir porosity
Solution Approach 1:
The patent segments the immovable hydrocarbon assessment into separate quantification of tar and pyrobitumen using compositional modeling. By calculating the volumetric percentage of each component separately and relating it to reservoir porosity, the method provides precise measurement of how each substance impacts fluid mobility, rather than treating them as a single undifferentiated phase.
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
The VOM method allows for accurate discrimination and quantification of organic matter components, enabling effective assessment of their impact on reservoir performance by providing geochemical data in units relevant to reservoir geologists and engineers, enhancing the understanding of tar and pyrobitumen occurrence and their effect on porosity and fluid mobility.
Implementation Method 1
The VOM method involves direct measurement of hydrocarbons using pyrolysis and compositional modeling
Data Source
AI summary
A method for calculating the volume of various predetermined organic end-members in samples of rock at various depths in oil reservoir rock is utilized to produce one or more graphic displays that are use to interpret the data to identify, e.g., tar mats, in order to improve the efficient production of hydrocarbons from the well. Data is collected from the samples by known pyrolysis and compositional modeling methods; additional data is obtained by elemental analysis to determine weight percentages of C, H, N, S and O in the selected end-members and characterization of physical properties of representative samples of the reservoir rock, e.g., from core samples; the data is then processed in accordance with the method to provide a series of data points used to produce the graphic displays for visual interpretation.