The Expulsinator device: A new approach for a lab-scaled, near-natural generation- and expulsion simulation

Abstract

Abstract Investigating hydrocarbon generation and expulsion by pyrolysis is limited by methodologies incapable of simulating conditions close to those prevailing in natural systems. Destructive sample preparation, inappropriate pressure regimes and pyrolysis in closed mode and/or in the absence of water caused results not representative for natural processes. We here present a new approach for a laboratory scaled simulation of generation, primary migration and expulsion under near-natural conditions, using the “Expulsinator” device. Near-natural conditions are realized by application of lithostatic pressure onto a source-rock disc with intact pore network and by pyrolysis at the presence of water, conducted in open flow through mode. This study will give a detailed technical description of the apparatus and the methodology to implement an Expulsinator experiment. An Expulsinator experiment generates a combined generation and expulsion profile, resulting in a detailed source rock characterization, incorporating yields for oil and gas, as well as rock deformation data on mm- and μm-scale. Thus, information is provided about timing and amplitude of generation and expulsion events. The apparatus uses a novel way of continuous sampling during the pyrolysis, enabling product removal from the reactor during the generation and expulsion process. Sampling in open flow-through mode is technically demanding and requires stimulation by a modifier for quantitative removal of the expelled products from the reactor. Test experiments demonstrate that the modifier has no impact onto the expulsion behavior of the source rock. Following the technical description, the generation and expulsion profile of one Expulsinator experiment is discussed. Beside information about timing of product generation and expulsion, the experiment shows the connection between rock expansion/compression and expulsion events. The efficiency of this new methodology is compared with conventional closed hydrous pyrolysis. The results exhibit the advantages of the apparatus: Liquid yields are increased, and hydrocarbon (HC) -gas generation reduced, due to a suppression of secondary reaction by the open setup. Furthermore, conventional pyrolysis achieved lower expulsion rates, due to the absence of lithostatic pressure. The Expulsinator shows high potential for further applications, in particular for implementation of lab-simulation data into numeric models.