It is well known that pre-existing fractures and depletion play an integral role in the completion and production of infill wells. However, it is often left to speculation as to where and how these depleted fractures are distributed along the wellbore. To bring additional context to this problem, this paper will discuss a case study in which three complimentary technologies were used to gain better understanding. The insights gained will help to better utilize data obtained from image logs and will help validate the process of using drilling data to identify depletion.
The case study presented focuses on an infill shale well flanked by two offset producers. During drilling, mud gas was analyzed and post drilling, an imaging tool was deployed to identify fractures present. Subsequently, depletion mapping was performed on the infill well by using raw drilling data, acquired at the surface, to identify areas of pressure depletion and their approximate magnitude based on drilling response. By combining these three complimentary measurements a better understanding of fracture propagation and drainage was obtained.
The analysis performed on this data brought many insights which will be shared in this paper. It was seen that depletion around fractures can likely be identified using drilling data and this can sometimes be further validated by changes in the mud gas composition. It will demonstrate how some fractures have depletion associated with them, while others do not, and may provide insight in how to distinguish between producing and non-producing fractures in oil-based image logs.
While this method of identifying fractures using drilling data has been utilized and validated in wells across North America, this paper will document the first time that the process was compared to image logs and will outline why these processes are complimentary to one another.
As more research is now being conducted into fracture interactions and their various causes and effects, it is becoming more apparent that one of the key factors for fracture interactions is the existence of preexisting fractures. These pre-existing fractures have often been created during the fracturing of offset wells (Gale 2018, Wutherich 2020, Juarez 2021). The fractures create a path for fracturing fluids to "short circuit" directly to producing wells, rather than being used to break new rock, and as a result can cause poor hydraulic fracture efficiency.
