One geologic difference between unconventional "shale" reservoirs is their highly laminated/layered nature as compared to most "more conventional" formations. They can include significant variations in the mechanical properties of associated layers down to an inch scale. Over recent years, there has been significant discussion in industry literature about the potential effects of these thin layers on fracture height growth.
This discussion has mostly centered around the idea of "slippage" where a fracture might separate at a layer boundary and lose the sharp "point", and/or delamination where by a horizontal boundary at a layer interface would separate vertically and open a (probably short) horizontal fracture. These two ideas will be briefly examined, and a third possibility raised - simply higher stress in a thin layer.
The physical justification for higher stress in a thin layer is examined, and then the height confinement characteristics of thin (or multiple thin) layers will be examined. Or, is a thin high stress layer a better barrier than a thicker, lower stress interval? If thin layers can provide significant barriers, how does that interact with gridding for gridded fracture models or with "Pseudo-3D" models where there is no explicit gridding. All of these questions will be addressed based on detailed simulations for a layered reservoir.
