AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Fractures Interactions in Multistage Hydraulic Fracturing
(1) Petroleum Engineering, Louisiana State University, Baton Rouge, LA.
Very low permeability of shale gas reservoirs has made multi-stage fracturing a promising solution for geologists to improve recovery factor and consequently production in the horizontal wells. Lacking a good understanding of the mechanisms involved in the multistage fracturing has left operators with trial and error approaches in designing fracture treatments. This research is mainly focused on understanding the mechanics of multi-stage fracturing. I will try to highlight the phenomena that make multi-stage treatments quite different from classical single stage treatments. These differences are generally rooted in the fact that at each stage, induced fractures will perturb their surrounding stress fields, which may affect the growth path of the next sets of fractures. On top of that compressible proppants will contribute to the normal compliance of the induced fractures. It will be shown how this excessive compliance could sometimes be used as an advantage to avoid fractures interceptions and its consequent damages. On the other hand, the stress field induced by more recent fractures may crush proppants in the previously-induced fracture or lead to further slippage along the previously opened fractures. Recent microseismic records have also confirmed seismic activities in the previously fractured zones during stimulation of new zones. Especially in case of pressure sensitive reservoirs, the overall permeability of each zone may decrease by the fracturing in other zones. Damage to the reservoir permeability could also be caused by gel remnants trapped in the intercepted fractures. In this presentation, I am trying to quantitatively verify different possible scenarios of interactions between different fracture stages. Studying controlling parameters that would affect the strength of these interactions will lead to determining the optimized spacing between fracture stages and also a better selection of fracturing fluid and proppants to maximize the drainage area in the stimulated zone.