Search

Mud shale hydration and swelling are major challenges in the development of water-based drilling fluids (WBDFs). In this work, the inhibition performance and inhibition mechanism of polyethylene glycol (PEG) and potassium chloride (KCl) were investigated by hot rolling recovery tests, linear swell tests, Fourier transform infrared spectroscopy, X-ray diffraction, atomic absorption spectrophotometry and X-ray photoelectron spectroscopy. The experimental results show that the combination of PEG and KCl achieved higher recovery and lower linear swelling rate than those obtained by individual PEG or KCl. Compared to the d-spacing of Na-montmorillonite (Na-Mt) with PEG or KCl, the d-spacing of Na-Mt with PEG+KCl was lower, which indicates that KCl and PEG have synergistic inhibition effect. This synergistic effect can replace sodium ions and water molecules from the interlayer space of Na-Mt and decrease the d-spacing of Na-Mt. Based on the above experimental results and analysis, a method for optimizing PEG and KCl concentrations was proposed and further verified by rheological and hot rolling recovery tests of WBDFs. Hence, the results of this work can provide valuable theoretical guidance for developing other synergistic inhibitors. [ABSTRACT FROM AUTHOR]

Sesquiterpanes are ubiquitous components of crude oils and ancient sediments. Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hesigewula Sag were analyzed by gas chromatography–mass spectrometry (GC–MS). C14 bicyclic sesquiterpanes, namely, 8β(H)-drimane, 8β(H)-homodrimane, and 8α(H)-homodrimane were detected and identified on basis of their diagnostic fragment ions (m/z 123, 179, 193, and 207), and previously published mass spectra data, and these bicyclic sesquiterpanes presented relatively regular characteristics in their thermal evolution. The ratios 8β(H)-drimane/8β(H)-homodrimane, 8β(H)-homodrimane/8α(H)-homodrimane, and 8β(H)-drimane/8α(H)-homodrimane all show a clear upward trend with increasing temperature below the temperature turning point. Thus, all these ratios can be used as evolution indexes of source rocks in the immature–low-maturity stage. However, the last two ratios may be more suitable than the first ratio as valid parameters for measuring the extent of thermal evolution of organic matter in the immature–low-maturity stage because their change amplitude with increasing temperature is more obvious. [ABSTRACT FROM AUTHOR]

Gas chromatography/mass spectrometry (GC/MS) can only analyze volatile molecular compounds, and it has limitations when applied to determine the complex components of crude oils and hydrocarbon source rocks. Based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and GC/MS analyses, the molecular compositions of NSO compounds in extracts from the Permian Dalong Formation, Sichuan Basin and the Permian Lucaogou Formation, Junggar Basin in China were compared. Analyses of types of heteroatoms present (S1, S2, S3, OS, OS2, O2S, NS, and NOS compounds) suggest that marine shales from the Dalong Formation are mainly composed of carboxylic acids (O2 compounds) with a high abundance of fatty acids, indicating a marine phytoplankton organic source. However, lacustrine shales from the Lucaogou Formation are dominated by pyrrolic compounds (N1 compounds) with abundant dibenzocarbazole. It suggests that the organic source materials may be derived from lower aquatic organisms and lacustrine algae. Overall, FT-ICR-MS has potential for applications in analyses and determination of depositional environments and organic sources in petroleum geology. [ABSTRACT FROM AUTHOR]