oa LIPS: A new instrument performing high resolution core logs of organic carbon

Objective: This paper describes a new pyrolysis instrument (LIPS: "Laser Induced Pyrolysis System") performing high resolution (centimetric or less) logs of organic carbon on ancient sediment cores . Stakes: the usual methods for determining the quantity of carbon in sediment samples (Rock-Eval, Leco, analysis of thin sections, etc.) are quite expensive, provide low resolution results (typically: one sample every 30cm to 2m) and are time and sample consuming. The processing of geophysical well logs provides low-resolution logs (about 30-50 cm). The characterization of organic carbon on cores needs high resolution, because its abundance may show huge variations at the millimetre or centimetre scale. One of the parameters driving the organic carbon quantity in ancient sediment is the climate. Principle: The LIPS performs automatic core analysis of organic carbon. The principle of the instrument consists in the pyrolysis of organic carbon using a beam of an infrared radiation emitted by power laser diodes focused on a small area of core (up to 20 MW/m2). Different power ranges can be used to adapt the instrument to the material analyzed. The organic vapors, oxidized compounds, micro- and nano-particles emitted during the very short impact (typically, 1-2 seconds) can be detected by various detectors (Photo ionization Detector, Flame Ionization Detector, Mass Spectrometer, Gas Analyzer, etc.) allowing high resolution logs of organic carbon. One hundred data points on a 1 meter core can be acquired in less than one hour. In order to obtain logs of organic carbon the method requires a calibration on a few points using, for instance, Rock-Eval or Organic Carbon Analyser on a limited number of samples. This new instrument consists in 4 main parts: 1/Bench for core examination and for acquiring the X,Y,Z coordinates of the laser impact on the core surface, 2/Core Box Storage Unit (CBSU), allowing to store up to 30 core boxes, 3/Core Box Sampler, used to carry the core boxes from CBSU to Acquisition Unit and vice-versa, 4/Acquisition Unit, including laser gun, detector(s), mechanism for moving the laser head and device for extracting organic vapors. Results: Initially developed for unconventional resources and tarmat in reservoirs, the LIPS is successfully applied for palaeoclimate recording.