In 2019, a process was developed that uses standard drilling data, obtained on virtually every well, to identify and quantify areas of localized depletion which occur around producing fractures in unconventional shale reservoirs. This data is most often used to mitigate fracture interactions. This paper however will examine the value of analyzing a pad of infill wells when there is a single-parent well and discuss how this information can be used to calibrate fracture models.
Examining how the frequency and magnitude of depletion events decrease as the distance from the parent well increases gives significant insight into several design aspects. Firstly, this data can be used to calibrate fracture growth models in a way similar to how microseismic might be used. Secondly, by analyzing not only how the number of fractures decreases, but also how the magnitude of depletion decreases as you move away from the parent well, operators will be better able to understand the impact of well spacing on the volume of recoverable reserves.
One of the most difficult aspects of shale development is accurately understanding how hydraulic fractures are growing and subsequently producing. The most widely accepted method of observing fracture growth is with microseismic monitoring, where fractures are located based on seismic measurements in offset wells such as the example shown in Figure 1. This process can be cost-prohibitive, and the resolution of the data makes interpretation difficult. For example, it can be difficult to discern whether a cloud of microseismic events is caused by a single fracture or several growing simultaneously.
Models can be created to simulate an estimated fracture length and height, but the highly heterogeneous nature of shale reservoirs and the large number of uncertainties in the model make these models only somewhat useful. These models can be improved through microseismic calibrations, but at the cost of hundreds of thousands of dollars.
