In the oilfield, the term "unconventional" almost always means difficult to get, for one or another reason. One reason addressed in this paper relates to formations characterized by the lack of permeable features that connect or can be easily connected to the wellbore using conventional stimulation techniques. The common logic of placing larger and larger fractures does work but, when using this approach, the cost-over-reward ratio can be far from desirable.
It is well-known that placing a second fracture sometime later in the life of a well will result in a fracture that extends in a slightly different direction, mostly caused by the drainage of the fluid near the fracture face. In this situation, fracture redirection is probably caused by the pore-pressure decline near the producing fracture face. In some instances, the new fracture produces almost as if it has reached a new formation.
This paper discusses placement of such "second" (or third) hydraulic fractures within the same time domain from the same wellbore section. It is believed that the first fracture will modify the stress field to a perpendicular direction. Combined with the hypothesis of the hard-to-accept concept that fractures often shy away from the most productive areas, this approach will cause the second fracture to extend directly into the more productive areas, thus providing a substantial production boost.