System and method for logging isotope fractionation effects during mud gas logging

A mud gas analyzer, comprising:

• at least one degasser adapted to extract gas from drilling mud passing through a flow path formed at least partially by a drill string within a well and an annulus positioned between an exterior surface of the drill string and a formation surrounding the well at a well-site;
• at least one gas analyzer, adapted to analyze the gas extracted by the plurality of degassers and generate a sequence of signals indicative of ratios of isotopes of gas species of gas extracted from the drilling mud;
• and
• a computer system including a processor adapted to execute logic to cause the processor to, receive the sequence of signals, and to calculate and log isotopic characteristics of gas entering the drilling mud at particular locations of the well,
• wherein the computer system uses data indicative of a predetermined rate of degassing of gas from the drilling mud, and one or more predetermined kinetic isotopic fractionation factor to calculate and log isotopic characteristics of gas entering the drilling mud at particular locations of the well.

One or more non-transitory computer readable medium storing processor executable code that when executed by one or more processors of a computer system cause the one or more processor to:

• receive information indicative of a geometry of a well, and a geometry of a tool string within the well, and a flow rate of drilling mud from at least one of a communication device and input device of the computer system or receive information from any other source providing particular locations of the well at which mixing of fractions of a gas species occurred
• receive a sequence of signals indicative of ratios of isotopes of a gas species of gas extracted from a drilling mud from the at least one of the communication device and the input device of the computer system, and
• calculate and log isotopic characteristics of gas entering the drilling mud at particular locations of the well,
• wherein the signals are indicative of a first level of retention of gas species in the drilling mud prior to reinjection of the drilling mud into the drill string, and are also indicative of a second level of retention of gases in the drilling mud upon exiting from an annulus;
• and
• wherein the processor executable code, when executed by one or more processors of the computer system, cause the one or more processor to analyze the sequence of signals to determine an isotopic composition of a gas species with logic indicative of δformation=(δOUT−fIN*δIN)/fformation where δformation is the isotopic composition of the gas entering the drilling mud at particular locations of the well, δOUT is the isotopic composition of the gas in the drilling mud upon exiting from the annulus, δIN is the isotopic composition of the gas in the drilling mud prior to reinjection of the drilling mud into the drill string, fIN is a fraction of the gas species transported out that is not coming from the formation, but is recycled gas;
• and fformation1−fIN.

One or more non-transitory computer readable medium storing processor executable code that when executed by one or more processors of a computer system cause the one or more processor to:

• receive information indicative of a geometry of a well, and a geometry of a tool string within the well, and a flow rate of drilling mud from at least one of a communication device and input device of the computer system or receive information from any other source providing particular locations of the well at which mixing of fractions of a gas species occurred
• receive a sequence of signals indicative of ratios of isotopes of a gas species of gas extracted from a drilling mud from the at least one of the communication device and the input device of the computer system, and
• calculate and log isotopic characteristics of gas entering the drilling mud at particular locations of the well,
• wherein the processor executable code, when executed by one or more processors of the computer system, cause the one or more processor to use data indicative of a predetermined rate of degassing of gas from the drilling mud, and one or more predetermined kinetic isotopic fractionation factor to calculate and log isotopic characteristics of gas entering the drilling mud at particular locations of the well.