Abstract
The main goal in stimulating shale formations is to maximize the reservoir contact with the hydraulic fracture face. In order to achieve this goal current practices include pumping low-viscosity fluids at high rates with small mesh proppant cycles. A novel approach was used in a well in the Eagle Ford shale to enhance the stimulated area. This technique, called “relax-a-frac”, was developed by an operator/service company alliance during the exploration phase. Real-time microseismic hydraulic fracture monitoring (RT HFM) indicated that the conventional slickwater treatments were not providing adequate lateral coverage across the planned stage. To address this issue, controlled changes were made to the pumping schedule, and the effects were evaluated using RT HFM. The results indicated that relax-a-frac proved to be highly successful in increasing the estimated stimulated volume (ESV) in this formation and area.
In relax-a-frac, a part of the stimulation treatment was pumped (usually pad plus proppant slugs), followed by an extended shutdown to relax the formation. Once the surface pressure reached a predetermined value, the treatment was resumed, as per program, with monitoring for microseismic activity. The microseismic activity observed during the second part of the treatment showed a significant increase compared to that of the first part, with improved lateral coverage. The resultant ESV increased significantly from this technique as compared to any other specific changes tried on these wells. Production log results from Well 1 showed a definitive correlation between production contribution and the ESV derived from HFM analysis. This paper documents that this novel approach more effectively stimulates the Eagle Ford shale when compared to the typical treatment designs. Conclusions from a detailed comparison of the well performance and its relation to the treatment design are included.
