Author: Abdelsalam Nasar Abdelhafid
In the beginning, the question should be asked that is there a relationship between the shale Hydraulic Fracturing (HF) and the shale anisotropy (Sh-ANISO)? If there is, what is the impact; is it minor or huge (negligible or considerable, respectively)? Starting from this, the involvement of the topic “Sh-ANISO” has not deeply been included as a key parameter in designing HF (HF length, HF propagation magnitude and orientation, etc.). The Sh-ANISO has not even be blamed for causing the swift decline of the production rate or the rapid increase of the water cut (WC%) after a short time, in many cases. This piece of writing highlights the influence of Sh-ANISO on HF.
As the importance of considering the major stresses orientations, including the vertical, maximum horizontal, and minimum horizontal stresses (sv, sH-MAX, and sh-min, respectively) is in maximizing the recovery factor by increasing the fractured area, the significance of applying the knowledge of Sh-ANISO becomes even greater in optimizing the HF patterns (primary and secondary fractures; tensile and shear failure modes, respectively). Maintaining the highest RF constant by avoiding damaging the fractured zone as a result of the optimal selection of α (α is the angle between the shale bedding plane and the horizontal plane), by crossing the highest number of shale beddings, and by maximizing tensile fractures and minimizing the shear fractures.
The producer would not only receive a high RF and keep it high for long period, but also would protect the fractured zone from being severely harmed (avoiding making the formation a chunk that would plug the flow path and trap away viscus hydrocarbons) and assist keeping the created channels as active link for a continues and constant influx towards the well bore.
The associated figure shows a sketch of different scenarios of HF as a function of shale anisotropy orientation. Scenario #1 (in black color) is in all three cases as the conventional applied mechanism. However, it is not necessarily always the optimal. The new favorable HF practice (in green color) is the one that takes care of as many parameters as possible and includes the critical factors, such as Sh-ANISO into consideration. The outcome of such practice could be huge. The results can vary to the extent of saving the formation from being damaged (although some researchers emphasize that damage in HF is not an issue, but I would say that avoiding harming the formation is favorable), where the formation would not be damaged, the flowing path would not be blocked and the flow rate would be high and constant longer than the conventional HF practices. This technique of “Sh-ANISO compass sensing”, could also maintain the high and constant flow rate and increase the oil swapping efficiency as a result of delaying the water breakout time by fracturing away from the Oil-Water-Contact (OWC) and maximizing the crossed shale layers.