Behavior of Oxidized Type-ii Kerogen During Artificial Maturation

A series of artificially oxidized type II kerogens (ventilated oven, 140-degrees-C, 8-256 h) from the Paris Basin (France) has been pyrolyzed in cold-seal autoclaves at temperatures ranging between 250 and 450-degrees-C for 24 h at 100 MPa. Oxidates and pyrolysates have been characterized by C-13 solid-state NMR, FTIR spectroscopy, Rock-Eval pyrolysis, elemental analysis, and CHCl3 extraction. Results indicate that oxidation is responsible for an important decrease of the petroleum potential and for the increase of different oxygen-bearing functions' (carbonyl, carboxyl, esters, ethers) concentration. The behavior of the different oxidates during artificial maturation is characterized by two distinct stages: oxygen removal (250-300-degrees-C) and hydrocarbon production (300-450-degrees-C). It is shown that oxidation induces an important decrease of the hydrocarbon yield during maturation and that no regeneration of petroleum potential can be observed. Comparison of the most oxidized kerogen (256 h) with an unoxidized type III coal of similar initial elemental composition has also been carried out

Spectroscopic Analyses of Aromatic-hydrocarbons Extracted From Naturally and Artificially Matured Coals

Experimental simulation of Mahakam delta (Indonesia) coals maturation has been carried out in a confined system under pressure. Chloroformic extracts have been fractionated by liquid chromatography. Aromatic hydrocarbons have been concentrated and analyzed by FTIR spectroscopy (Nicolet 20 SX B), high-resolution proton NMR (Brucker AM 500 MHz), and synchronous excitation-emission UV fluorescence (Perkin-Elmer LS 50). Band assignment was made in order to take into account the evolution of the proton NMR, FTIR, and synchronous UV fluorescence spectra with respect to bibliographic data and spectral resolution. Results have been compared to those of a natural homogeneous series of coals of increasing rank. The corrected organic carbon content (% COC = % C x 100/(% C + % H + % O + % N)) was chosen as a common maturity index for both natural and artificial series. The progressive removal of aliphatic chains, the increase in the proton aromaticity, and the structural rearrangement are similar for both series. However, some significant discrepancies are noticed between the artificial and natural series. They mostly concern the rate of aromatization, the intensity of ring condensation, and the amount of extractable hydrocarbons

Risk of bias in cross-sectional studies: Protocol for a scoping review of concepts and tools

Cross-sectional studies are commonly used to study human health and disease, but are especially susceptible to bias. This scoping review aims to identify and describe available tools to assess the risk of bias (RoB) in cross-sectional studies and to compile the key bias concepts relevant to cross-sectional studies into an item bank. Using the JBI scoping review methodology, the strategy to locate relevant RoB concepts and tools is a combination of database searches, prospective review of PROSPERO registry records; and consultation with knowledge users and content experts. English language records will be included if they describe tools, checklists, or instruments which describe or permit assessment of RoB for cross-sectional studies. Systematic reviews will be included if they consider eligible RoB tools or use RoB tools for RoB of cross-sectional studies. All records will be independently screened, selected, and extracted by one researcher and checked by a second. An analytic framework will be used to structure the extraction of data. Results for the scoping review are pending. Results from this scoping review will be used to inform future selection of RoB tools and to consider whether development of a new RoB tool for cross-sectional studies is needed