Downhole carbon logging apparatus, systems, and methods

#When locating and extracting hydrocarbons, well logging is commonly used to evaluate underground formations for the presence and producibility of hydrocarbon reservoirs. During the well-drilling process, or shortly thereafter, instruments are passed through the well bore to collect information about the formations through which the well bore passes. The information is traditionally collected in “log” form, i.e., a table or chart of measured data values as a function of instrument position.

#Embodiments of the invention may be understood by referring to the following description and accompanying drawings which illustrate examples of such embodiments. In the drawings:

#FIG. 1 shows an illustrative environment for drilling a well, according to some example embodiments.

#FIG. 2 illustrates a wireline operation, according to some example embodiments.

#Methods, apparatus and systems that can be used to determine organic carbon content of a reservoir are described. In the following description, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. Some embodiments may be used after or during the drilling operation (e.g., wireline operations, Measurement While Drilling (MWD), Logging While Drilling (LWD), etc.).

#In some embodiments, a tool is positioned downhole to irradiate formations of the earth. The irradiation causes neutron and nucleus interaction with the earth formation. The resulting radiation that is caused by the irradiation of the formations can be received and processed. In some example embodiments, the resulting radiation is gamma rays.

#The tool can use two different methods to collect the resulting radiation: radiation sorted by energy and radiation sorted by time lapse. The radiation sorted by energy provides elemental yields. The radiation sorted by time lapse provides a capture cross section.