Pores, spores, pollen and pellets are all important constituents of resource shales. Pores provide the storage place and, when connected, the transport route for hydrocarbon molecules. Conventional Scanning Electron Microscopy (SEM and FESEM) of pores from untreated surfaces from several resource shales reveal a common variety of pore types. An inexpensive method of analysis has been developed to measure porosity, and dimensions of pores. The shales exhibit a variety of porosities, but usually <10 average „area? percent. Usually, porosity is less when measurements are made on surfaces parallel to laminations, than on surfaces perpendicular to laminations owing to the platy nature of the contained clay minerals. Proportions of micropores (defined here as >1 µm in length) and nanopores (defined here as <1 µm in length) are about equal in the different shales.
Fecal pellets, the excrement of marine organisms, are storehouses of organic matter and pores, and may provide a significant source of gas during burial. Experiments with modern pellets indicate the undigested organic matter can generate not only has, but also liquid hydrocarbons which are apparently related to the remains of their food source. Sometimes the pellets are enriched in lamina that are not bioturbated, suggesting that they are produced in the water column above the euxinic zone, perhaps during periodic algal blooms.
Pollen and spores present in Paleozoic shales provide a robust means of regionally correlating strata and for defining major, eustatically controlled stratal surfaces.
Examples are provided of each of these shale features and their significance. Though small in scale, these common constituents of shales are often overlooked in the quest for preferred target strata for horizontal wells. However, as suggested by these examples, they may play an important role in exploration and development of resource shales.
URTeC 1573336
