Using Microseismic Source Parameters to Evaluate the Influence of Faults on Fracture Treatments - A Geophysical Approach to Interpretation

Abstract

AbstractMicroseismic monitoring during hydraulic fracturing treatments has confirmed that hydraulic fractures are much more complex than might have been assumed even a few years ago, when conventional fracture models were considered adequate. Analysis of diagnostic pump-in tests and mining tunnels has shown that fracture complexity exists in both the near-wellbore and far-field regions of the fracture. Also, microseismic monitoring and interpretation have shown that even fractures initiated in the same wellbore during successive stages can have distinctly different characteristics.Evaluating the effectiveness of hydraulic fracture treatments using microseismic events is challenging. The most common techniques attempt to correlate production with the dimensions of the microseismic clouds and volume estimates based on the density of microseismic events.Geophysical interpretation has shown that microseismic activity recorded during fracturing treatments can sometimes be associated with existing geological structures such as faults. It is possible to examine the frequency of the microseismic event magnitudes during a fracturing treatment and determine if microseismic events are being produced by the failure of the existing rock fabric, or activation of existing geologic structural features, which might be detrimental to well performance. The resulting frequency-magnitude distributions can then be correlated to observed fracture geometries.We show that it is possible to use microseismic magnitude to identify whether faults are influencing the observed dimensions of the microseismic event cloud. We also show that it is possible to use microseismic magnitude values to evaluate fracture behavior in real-time applications, allowing stimulation engineers to modify individual stage treatment designs as the specific situation dictates. The potential benefits to both stimulation cost and production results will also be discussed.