Source Rock Maturity Assessment Using Wetness-Corrected δ2H Values
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Solution Overview
Problem
Existing methods for determining source rock maturity using hydrogen isotope ratios fail to accurately account for isotopic reversals, leading to incorrect maturity calculations and potential miss-drilling in hydrocarbon production.
Innovation Solution
A method involving the use of a computer to correct hydrogen isotope values by establishing a relationship between wetness and δ2H values, applying a best-fit equation to generate a reference line, and adjusting δ2H values to match the line, thereby enabling accurate VRo determination for maturity assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hydrogen isotope ratios are used to determine source rock maturity, then maturity assessment can be performed, but isotopic reversals cause incorrect maturity calculations
Solution Approach 1:
The patent introduces wetness as an intermediary parameter to mediate between hydrogen isotope ratios and maturity assessment. By establishing a relationship between wetness and δ2H values through a best-fit equation, the method uses wetness as a mediator to correct isotopic reversal effects, thereby improving the reliability of maturity calculations while maintaining the ability to perform maturity assessment using hydrogen isotope ratios.
Solution Approach 2:
The patent changes the parameter relationship by introducing a correction mechanism that transforms the direct δ2H-to-maturity relationship into a two-step process: first determining wetness from δ2H values using a best-fit equation, then using wetness to determine maturity. This parameter transformation resolves the isotopic reversal problem by decoupling the direct relationship that causes inaccuracies.
2Ease of operation
If a direct relationship between δ2H values and VRo is assumed, then maturity determination is simplified, but isotopic reversals lead to miss-drilling
Solution Approach 1:
The patent introduces wetness as an intermediary between δ2H values and VRo determination. Instead of directly assuming a relationship between δ2H and VRo, the method first calculates wetness from δ2H values using a best-fit equation, then uses wetness to determine VRo and maturity. This intermediary approach maintains operational simplicity while eliminating the reliability issues caused by isotopic reversals.
Solution Approach 2:
The patent performs a preliminary calculation of wetness from δ2H values using a best-fit equation before determining maturity. This preliminary action of establishing the wetness-δ2H relationship through regression analysis prepares the data in a corrected form that eliminates isotopic reversal effects, ensuring accurate maturity determination without complicating the overall process.
3Device complexity
If isotopic reversal is not accounted for, then the assessment process remains straightforward, but sweet spots are incorrectly identified
Solution Approach 1:
The patent changes the assessment approach by transforming the raw δ2H values into corrected wetness values using a best-fit equation before maturity determination. This parameter transformation adds a correction step that accounts for isotopic reversals, improving sweet spot identification accuracy while maintaining relatively simple implementation through automated calculation.
Solution Approach 2:
The patent implements a feedback mechanism where the relationship between wetness and δ2H values is established through a best-fit equation derived from multiple gas samples. This feedback loop allows the system to learn and correct for isotopic reversal patterns, improving sweet spot identification accuracy without significantly increasing process complexity through automation.
Data Source
AI summary
A computer receives a measured wetness of and a measured δ2H value associated with a test gas sample from a hydrocarbon formation. The measured wetness is a molar ratio of heavy gas compounds over a total gas within the measured sample. The computer receives calculated wetnesses calculated δ2H values associated with a gas samples taken from one or more analogous hydrocarbon reservoirs. The measured wetness received for the test gas sample is identified from among the plurality of calculated wetnesses. The computer determines a corresponding δ2H value from among the calculated δ2H values that corresponds to the measured wetness of the test gas sample. The computer determines a predicted sample VRo (vitrinite reflectance equivalent) for the test gas sample based on the corresponding δ2H value and a correlation of δ2H values to VRo values. Hydrocarbons are produced from the hydrocarbon formation based on the predicted sample VRo.