Determining source rock maturity based on hydrogen isotopes

A method comprising:

• receiving a test gas sample from a wellbore within a test hydrocarbon formation;
• determining a measured wetness of the test gas sample;
• determining a measured δ2H value associated with the test gas sample;
• receiving a plurality of calculated δ2H values from a plurality of gas samples with a corresponding plurality of calculated wetnesses of the plurality of gas samples, wherein the plurality of gas samples are taken from one or more analogous hydrocarbon formations that are analogous to the test hydrocarbon formation;
• identifying, from the plurality of calculated wetnesses, the measured wetness of the test gas sample;
• determining a corresponding δ2H value from among the plurality of calculated δ2H values that corresponds to the measured wetness of the test gas sample;
• adjusting the measured δ2H value to equal the corresponding δ2H value to provide an adjusted δ2H value;
• determining a predicted sample VRo (vitrinite reflectance equivalent) for the test gas sample based on the adjusted δ2H value and a correlation of δ2H values to VRo values, the VRo values correlating with gas maturity;
• and
• producing hydrocarbons from the hydrocarbon formation based on the predicted sample VRo.

A method comprising:

• receiving, by a computer system, a dataset comprising calculated wetnesses of and calculated δ2H values associated with hydrocarbon gasses;
• determining, by the computer system, a reference line from the dataset;
• plotting, by the computer system, the reference line on a plot;
• plotting, by the computer system, a sample wetness of and a sample δ2H value associated with a received gas sample received from a hydrocarbon formation on the plot with the reference line to produce a plotted point;
• increasing, by the computer system, a δ2H value of the plotted point to provide an adjusted plotted point so that a δ2H value of the adjusted plotted point matches the reference line;
• determining, by the computer system, an adjusted δ2H value from the adjusted plotted point, wherein the adjusted δ2H value is the δ2H value of the adjusted plotted point;
• and
• determining, by the computer system, a predicted sample VRo (vitrinite reflectance equivalent) for the received gas sample based on the adjusted δ2H value and a correlation of δ2H values to VRo values, the VRo values correlating with gas maturity.