In general, irregular periods are very common during the perimenopause. The most common early menstrual irregularity noticed in the perimenopause is a shortening of cycle length.
Abiogenic petroleum origin. Abiogenic petroleum origin is a term used to describe a number of different hypotheses which propose that petroleum and natural gas are formed by inorganic means rather than by the decomposition of organisms.
The AER refers to unconventional natural gas as. 1  tight gas: natural gas found in low-permeability rock, including sandstone, siltstones, and carbonates. 2  shale gas: natural gas locked in fine-grained, organic-rich rock. 3  coalbed methane (CBM): natural gas contained in coal.